fix: judge the symbol a user sees, not the bytes a contract returns (closes #260)

A token whose symbol is " ETH " missed KNOWN_SYMBOLS on all three surfaces
while HTML collapsed the padding and painted it as ETH next to the user's
real ETH. isSpoofedSymbol() now normalizes before the lookup: NFKC, then
every character that paints nothing removed wherever it sits, then trimmed,
then uppercased. All three surfaces inherit it unchanged.

The strip is "renders as nothing", spelled as \p{Cf} plus
\p{Default_Ignorable_Code_Point} plus U+007F. The classes are the spelling
and not the rule, which is why U+007F is named on its own: it is a control
rather than a default-ignorable character, so no class reaches it, yet it
measures 32.00px in the repo's pinned e2e Chromium at 16px sans-serif --
exactly a plain ETH -- so it paints nothing and would otherwise be a live
bypass. The remaining C0/C1 controls measure 48.00px, a visible box, and are
left alone; both directions are pinned by tests, and widening the strip to
\p{Cc} fails the visible-controls test.

Covered: ASCII and Unicode whitespace padding, zero-width and other
invisible characters, and compatibility variants such as fullwidth letters.
Knowingly left open, and asserted as open in the suite: confusables that are
distinct letters (Cyrillic capital Ie), bidi reordering, the visible
controls, and interior whitespace, which renders differently and so is not
the confusion.

No symbol in KNOWN_SYMBOLS or the bundled token list contains whitespace or
a non-ASCII character, so nothing legitimate is newly filtered; a test walks
the whole table and asserts it.

The balance list's token-type gate is now case-insensitive. It compared
exactly, so an explorer writing "erc-20" would silently drop a real holding
before any filter ran. Which types are admitted is unchanged.

Makefile

@@ -1,4 +1,4 @@
-.PHONY: bootstrap setup install test test-e2e lint fmt fmt-check check docker hooks build build-debug verify-build clean dev
+.PHONY: bootstrap setup install test test-e2e test-e2e-firefox lint fmt fmt-check check docker hooks build build-debug verify-build clean dev
 
 # Standard targets are thin shims; the implementations live in script/
 # per the scripts-to-rule-them-all pattern (see the Entrypoints section
@@ -16,10 +16,13 @@ install:
 test:
 	@script/test
 
-# Browser end-to-end suite. Requires docker; not part of check.
+# Browser end-to-end suites. Both require docker; neither is part of check.
 test-e2e:
 	@script/test-e2e
 
+test-e2e-firefox:
+	@script/test-e2e-firefox
+
 lint:
 	@script/lint
 

README.md

@@ -83,7 +83,10 @@ provide:
   git pre-commit hook
 - `script/projectname` — print the project name (used for the Docker image tag)
 - `script/test` — run the test suite (jest)
-- `script/test-e2e` — run the browser end-to-end suite (docker required; see
+- `script/test-e2e` — run the Chrome browser end-to-end suite (docker required;
+  see [End-to-End Tests](#end-to-end-tests))
+- `script/test-e2e-firefox` — run the Firefox browser end-to-end suite (docker
+  required; builds its own pinned image, see
   [End-to-End Tests](#end-to-end-tests))
 - `script/lint` — run the linter
 - `script/fmt` — format all files (writes)
@@ -123,6 +126,14 @@ The Makefile shims to those. It also carries a few targets that have no
 
 ## End-to-End Tests
 
+There are two suites, one per browser, and they share no code. Chrome runs on
+Playwright; Firefox has its own WebDriver client, because Playwright cannot
+observe errors on a Firefox extension page at all — see
+[Firefox](#firefox-make-test-e2e-firefox) below. Both require docker, and both
+are outside `make check`.
+
+### Chrome (`make test-e2e`)
+
 `make test-e2e` builds `dist/chrome/` and drives the **real popup in a real
 Chrome**, loaded as an unpacked MV3 extension inside a pinned
 `mcr.microsoft.com/playwright` container (pinned by digest in `script/test-e2e`;
@@ -200,12 +211,90 @@ a `ReferenceError` from a used-but-not-imported identifier is invisible to
 `make check` (`script/lint` is only `prettier --check`) but fatal in a browser,
 and this suite exists because exactly that class of bug shipped twice.
 
-`make test-e2e` is deliberately **not** part of `make check` or `make test`.
+### Firefox (`make test-e2e-firefox`)
-`REPO_POLICIES.md` caps `make test` at 20 seconds and a browser suite does not
+
-fit; nothing in `tests/e2e/` is named `*.test.js`, so jest cannot pick it up
+`make test-e2e-firefox` builds `dist/firefox/` and drives the **real popup in a
-either. It is also not wired into the Gitea workflow yet — docker-in-docker in
+real Firefox**, installed as an unpacked MV2 temporary add-on via geckodriver.
-CI is a separate question. Run it locally before changing anything under
+It covers popup load, wallet creation through the UI, and the Add Token screen.
-`src/popup/views/`.
+The suite lives in `tests/e2e/firefox/` and has **no npm dependencies at all**:
+it is a small WebDriver client built on global `fetch` and `child_process`
+against geckodriver's HTTP API.
+
+Unlike the Chrome suite it builds its own container image rather than pulling a
+published one, because no published image carries both a pinned Firefox and a
+matching geckodriver. `tests/e2e/firefox/Dockerfile` pins all three external
+artifacts by digest — the `node` base image, the Firefox 153.0.3 tarball, and
+geckodriver 0.36.0 — and the Firefox version in particular must not float:
+`-remote-allow-system-access` is **mandatory** on 153 and was not on 142.
+Without that flag, both navigating to `moz-extension://` and running
+chrome-context script fail with `unsupported operation`. The flag grants the
+driver full chrome privileges over that browser, which is acceptable only
+because it is a throwaway container.
+
+The popup's `moz-extension://` uuid is **pinned, not discovered**: the profile
+pref `extensions.webextensions.uuids` maps the extension id that
+`manifest/firefox.json` already declares to a fixed uuid, so the popup URL is
+deterministic. Navigation uses **classic** WebDriver `POST /session/{id}/url`,
+because BiDi's `browsingContext.navigate` refuses `moz-extension://` outright.
+
+**Any uncaught error from a `moz-extension://` source fails the run**, including
+errors from the background page, which the suite never navigates to: a `throw`
+at the top of `src/background/index.js` kills the background page and fails
+step 1. Content-script errors should arrive by the same route, but this suite
+does not exercise it and does not claim it — with `--network none` there is no
+`http://` page for a content script to be injected into. Errors from add-on
+install and background startup are folded into step 1 rather than discarded.
+Errors are read from the privileged `nsIConsoleService` in Marionette's chrome
+context and filtered to non-warning entries whose `sourceName` is the extension
+origin. That mechanism is not a stylistic choice. WebDriver BiDi's
+`log.entryAdded` delivers **nothing** for extension pages: on a plain `http://`
+page it reports uncaught errors with stack traces, and on the `moz-extension://`
+popup it reports zero events, because Firefox's remote agent excludes extension
+browsing contexts from BiDi observation. Any harness built on Playwright-BiDi or
+Puppeteer-BiDi would therefore see nothing and report success, which is exactly
+the vacuous check this repo has already shipped twice. Do not migrate this suite
+to BiDi.
+
+Two limits are worth knowing, both real differences from the Chrome suite:
+
+- **Error capture is poll-based, not event-streamed.** The console is drained at
+  each step boundary, so an error is attributed to the step it was drained
+  after, not to a moment within it. The window that is drained runs from add-on
+  install to **≈1.5s** after the last step returns — a 500ms settle, a 1000ms
+  tail sleep and two drain round trips — and then the browser is torn down. That
+  cut-off is not a hard boundary: with throws scheduled at fixed offsets, three
+  runs reported everything up to +1.5s and one of the three also reported +1.6s,
+  so an error landing near it may or may not be seen, and anything well past it
+  is not. Inside the window there is no race — each drain reads and clears the
+  console in a single chrome round trip, so an error logged mid-drain lands in
+  that batch or the next rather than being destroyed unread — but there is a
+  **capacity limit**: `nsIConsoleService` keeps a ring buffer of 250 messages
+  and silently evicts the oldest, so more than 250 console messages between two
+  drains destroys the excess unread. 400 throws inside one step are reported as
+  exactly the newest 250, three runs running. That buffer is shared with
+  Firefox's own console noise; a clean run peaks at 4 of 250 at the install
+  drain and 0 at every later drain, so the three steps here have wide headroom,
+  but a step that logs heavily could evict unread errors. What poll-based costs
+  is location, not coverage: an error cannot be placed within a step the way the
+  Chrome suite's `pageerror` events place it.
+- **Nothing is stubbed, which inverts the coverage of network-dependent code.**
+  There is no fixture layer; the container runs with `--network none` instead,
+  so the run is offline and deterministic and no request can escape. The
+  extension swallows its own fetch failures, so the flows are unaffected — but
+  every network call fails, so only the _failure_ branches of code that depends
+  on one are ever executed. A `ReferenceError` in the success path of
+  `renderTransactions`, or of price or balance rendering, passes this suite
+  green. The offline run is also weaker than the Chrome suite's interception: it
+  proves nothing got out, but it cannot report which requests were attempted.
+  Closing that gap needs a fixture layer, deliberately out of scope for this
+  harness.
+
+Neither `make test-e2e` nor `make test-e2e-firefox` is part of `make check` or
+`make test`. `REPO_POLICIES.md` caps `make test` at 20 seconds and a browser
+suite does not fit; nothing in `tests/e2e/` is named `*.test.js`, so jest cannot
+pick it up either. Neither is wired into the Gitea workflow yet —
+docker-in-docker in CI is a separate question. Run them locally before changing
+anything under `src/popup/views/`.
 
 ## Rationale
 
@@ -1041,7 +1130,12 @@ on ConfirmTx, DeleteWallet, ApproveTx and ApproveSign.
 - **When**: A connected website requests a transaction via
   `eth_sendTransaction`. Always opened in a separate popup window by the
   background script (`windows.create()`), because the request is triggered
-  programmatically rather than by a user gesture.
+  programmatically rather than by a user gesture. The background populates the
+  transaction (nonce, gas limit, fees, chain id) against the RPC node _before_
+  opening the window, so the screen shows a complete transaction and the signed
+  artifact can be compared with it field for field. A request that cannot be
+  populated — unreachable node, reverting gas estimate — opens no window and is
+  failed back to the site.
 - **Elements**:
     - "Transaction Request" heading
     - Phishing warning banner (shown when the hostname is on the phishing
@@ -1053,13 +1147,16 @@ on ConfirmTx, DeleteWallet, ApproveTx and ApproveSign.
     - Contract: color dot + full address + etherscan link (or "contract
       creation"), token symbol label if known
     - Value: amount in ETH (4 decimal places, USD in parentheses)
+    - Network fee (max): gas limit × fee per gas in ETH (4 decimal places, USD
+      in parentheses), with the gas limit and the fee per gas in gwei below it
+    - Network and nonce
     - Raw data: full calldata displayed inline (shown if present)
     - Password input and an error line
     - "Confirm" / "Reject" buttons
 - **Transitions**:
-    - "Confirm" (correct password) → decrypts and signs in the popup, hands the
+    - "Confirm" (correct password) → decrypts and signs the transaction it was
-      signed transaction to the background to broadcast, then → **WaitTx** in
+      shown, exactly as shown, hands the signed transaction to the background to
-      the same popup window
+      broadcast, then → **WaitTx** in the same popup window
     - "Confirm" (wrong password) → error line, no screen change
     - "Reject" → closes popup (returns rejection to background)
     - Popup window closed without answering → the request is rejected with

TODO.md

@@ -30,9 +30,10 @@ compiled off.
 
 The backlog lives on the
 [Gitea tracker](https://git.eeqj.de/sneak/AutistMask/issues), which is
-authoritative; this file does not duplicate it. Full policy file set present. A
+authoritative; this file does not duplicate it. Full policy file set present.
-real-browser end-to-end suite (`make test-e2e`) now sits alongside `make check`,
+Real-browser end-to-end suites (`make test-e2e` for Chrome,
-which cannot see a runtime `ReferenceError` in a popup view.
+`make test-e2e-firefox` for Firefox) now sit alongside `make check`, which
+cannot see a runtime `ReferenceError` in a popup view.
 
 # Next Step
 
@@ -46,16 +47,47 @@ undefined identifiers, which is how
 
 - 2026-08-12: The known-symbol spoof rule now judges the symbol a user actually
   sees. `isSpoofedSymbol()` normalizes before the lookup — NFKC, then every
-  format and default-ignorable character removed, then trimmed — so `" ETH "`, a
+  character that paints nothing removed (the format and default-ignorable
-  no-break space, a zero-width space, a Hangul filler, a variation selector and
+  characters, plus U+007F), then trimmed — so `" ETH "`, a no-break space, a
-  a fullwidth `ＥＴＨ` are all caught on the balance list, the history and the
+  zero-width space, a Hangul filler, a variation selector, a DELETE and a
+  fullwidth `ＥＴＨ` are all caught on the balance list, the history and the
   send selector at once. Confusables that are distinct letters (Cyrillic `Е`),
-  bidi reordering, the visible C0/C1 controls and U+007F stay knowingly open and
+  bidi reordering and the visible C0/C1 controls — which measure 48.00px, a box,
-  are asserted as open in the suite. No bundled symbol contains whitespace or a
+  in the pinned e2e Chromium where an invisible prefix measures 32.00px — stay
-  non-ASCII character, so nothing legitimate is newly filtered; the balance
+  knowingly open and are asserted as open in the suite. No bundled symbol
-  list's token-type gate also became case-insensitive, which no longer drops a
+  contains whitespace or a non-ASCII character, so nothing legitimate is newly
-  real holding if an explorer writes `erc-20`
+  filtered; the balance list's token-type gate also became case-insensitive,
+  which no longer drops a real holding if an explorer writes `erc-20`
   ([#260](https://git.eeqj.de/sneak/AutistMask/issues/260)).
+- 2026-08-12: A containerized Firefox end-to-end harness
+  (`make test-e2e-firefox`) drives the real popup in a real Firefox with the MV2
+  build installed as a temporary add-on. Zero npm dependencies — a WebDriver
+  client over `fetch` against geckodriver — with `node`, Firefox 153.0.3 and
+  geckodriver 0.36.0 all pinned by digest. Uncaught errors are read from the
+  privileged console service in Marionette's chrome context, because BiDi
+  `log.entryAdded` reports nothing at all for extension pages; each drain reads
+  and clears the console in one chrome round trip, so no error is destroyed
+  unread by the drain itself, and errors logged during add-on install and
+  background startup are folded into step 1 instead of being cleared. The two
+  measured limits are documented rather than claimed away: the console ring
+  buffer holds 250 messages (a clean run peaks at 4), and the drained window
+  ends ≈1.5s after the last step returns. Demonstrated discriminating by exiting
+  1 on a `throw` at the top of `src/background/index.js`, on a build with one
+  import removed, on a `setTimeout` throw whose UI assertions all pass, on an
+  unhandled `Promise.reject` and on an undefined identifier in `home.js`, and 0
+  on the branch as it stands
+  ([#184](https://git.eeqj.de/sneak/AutistMask/issues/184)).
+- 2026-08-12: The transaction a dApp asks for is now populated in the background
+  before the approval window opens, so the object the user is shown is the
+  object the signed artifact is verified against — nonce, gas limit and every
+  fee field are compared exactly instead of being left to the ceilings, which
+  stay as a backstop against what a lying RPC node can talk the wallet into
+  displaying. The approval also pins the address it was raised for, so an
+  address switch between approval and signing refuses rather than signing from
+  an account the screen never named, and a request naming an address that is not
+  the active one is refused outright. The approval screen now shows the fee, gas
+  limit, network and nonce it vouches for
+  ([#216](https://git.eeqj.de/sneak/AutistMask/issues/216)).
 - 2026-08-12: The restored navigation stack is filtered against
   `RESTORABLE_VIEWS` on load, truncated at the first entry the popup would not
   render so that every surviving entry keeps the Back target it had. Back after
@@ -280,9 +312,9 @@ tracker.
 - Pre-1.0 security review of the extension (key handling, DEBUG mode policy, RPC
   input validation) before any 1.0rc tag. Individual filed issues are parts of
   it, but the review is broader than any of them.
-- Decide whether docker-in-docker makes `make test-e2e` runnable in the Gitea
+- Decide whether docker-in-docker makes `make test-e2e` and
-  workflow. Extending the suite itself is tracked as
+  `make test-e2e-firefox` runnable in the Gitea workflow. Extending the Chrome
-  [#183](https://git.eeqj.de/sneak/AutistMask/issues/183) and
+  suite itself is tracked as
-  [#184](https://git.eeqj.de/sneak/AutistMask/issues/184).
+  [#183](https://git.eeqj.de/sneak/AutistMask/issues/183).
 - Cut 1.0.0 once the milestone is empty, then continue tagging as milestones
   land.

docs/README.md

@@ -311,10 +311,15 @@ pages. When a site requests access to your wallet:
    time.
 
 When a connected site requests a transaction, a separate approval popup appears
-showing the transaction details (from, to, value, data). You must enter your
+showing the transaction details (from, to, value, data, network fee, network and
-password and click "Confirm" to authorize it. Message and typed-data signature
+nonce). Every one of those values is checked against the transaction that is
-requests work the same way, with a "Sign" button, and also require your
+actually signed before anything is broadcast, so what you read on that screen is
-password.
+what goes out or nothing does. The popup appears once the wallet has worked out
+the fee and gas from the network, which takes a moment; if that fails, no popup
+appears and the site is told the transaction could not be prepared. You must
+enter your password and click "Confirm" to authorize it. Message and typed-data
+signature requests work the same way, with a "Sign" button, and also require
+your password.
 
 If the requesting site's domain is on the phishing blocklist, all three approval
 screens show a red phishing warning before you decide.

script/test-e2e-firefox

@@ -0,0 +1,63 @@
+#!/bin/sh
+# script/test-e2e-firefox: build the extension and drive the real popup in
+# a real Firefox inside a pinned container. The Firefox counterpart to
+# script/test-e2e. Our own extension to scripts-to-rule-them-all.
+#
+# Deliberately NOT called by script/check or script/test, for the same
+# reason as the Chrome suite: REPO_POLICIES.md caps make test at 20 seconds
+# and a browser suite does not fit.
+#
+# Unlike script/test-e2e this builds its image locally, because no
+# published image carries both a pinned Firefox and a matching geckodriver.
+# All three external artifacts are pinned by digest inside the Dockerfile;
+# see tests/e2e/firefox/Dockerfile.
+set -eu
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd -P)"
+ROOT="$(cd "$SCRIPT_DIR/.." && pwd -P)"
+
+IMAGE="$("$SCRIPT_DIR/projectname")-e2e-firefox"
+
+main() {
+    cd "$ROOT"
+
+    if ! command -v docker >/dev/null 2>&1; then
+        echo "test-e2e-firefox: docker is required to run the e2e suite" >&2
+        exit 1
+    fi
+
+    echo "Building extension for e2e..."
+    yarn run build 2>&1
+
+    # The build context is tests/e2e/firefox/ and holds nothing but the
+    # Dockerfile: the harness itself arrives over the bind mount below, so
+    # editing it never invalidates an image layer.
+    echo "Building the pinned Firefox e2e image..."
+    docker build -t "$IMAGE" "$ROOT/tests/e2e/firefox"
+
+    echo "Running the Firefox e2e suite..."
+    # --shm-size=1g: Firefox needs more than the default 64MB /dev/shm.
+    # --network none: the suite stubs nothing, so this is what keeps the
+    #   run offline and deterministic. The extension swallows its own
+    #   fetch failures, so the popup flows work unchanged; see the
+    #   network note in README.md. Weaker than the Chrome suite's
+    #   fixture interception, and honestly so — it proves no request
+    #   escaped, but it cannot report which ones were attempted.
+    # --user: keep files the suite touches owned by the caller, not root.
+    # HOME=/tmp: the mapped uid has no home directory in the image.
+    #
+    # No --privileged. Firefox's sandbox logs
+    # "CanCreateUserNamespace() clone() failure: EPERM" on startup here;
+    # it is cosmetic and headless Firefox runs fine without it.
+    docker run --rm \
+        --shm-size=1g \
+        --network none \
+        --user "$(id -u):$(id -g)" \
+        -e HOME=/tmp \
+        -v "$ROOT:/work" \
+        -w /work \
+        "$IMAGE" \
+        node tests/e2e/firefox/run.js dist/firefox
+}
+
+main "$@"

src/background/index.js

@@ -18,11 +18,14 @@ const {
     verifySignature,
     failureIsRetryable,
     describeTxFailure,
+    sameAddress,
+    ApprovalMismatchError,
     TX_STAGE_SIGN,
     TX_STAGE_VERIFY,
     TX_STAGE_BROADCAST,
     TX_STAGE_INFLIGHT,
 } = require("../shared/approvalVerify");
+const { prepareApprovalTx } = require("../shared/approvalTx");
 const {
     isPhishingDomain,
     refreshPhishingListOnSchedule,
@@ -77,6 +80,14 @@ async function getActiveAddress() {
     return null;
 }
 
+// Whether a request names a signing address other than the active one. Such a
+// request is refused rather than quietly signed as whichever address happens
+// to be active: the page asked for account A and would otherwise be handed
+// something from account B.
+function namesAnotherAddress(requested, activeAddress) {
+    return !!requested && !sameAddress(requested, activeAddress);
+}
+
 async function getRpcUrl() {
     const s = await getState();
     return s.rpcUrl || DEFAULT_RPC_URL;
@@ -225,13 +236,21 @@ function requestApproval(origin, hostname) {
 // Uses windows.create() directly because tx approvals are triggered programmatically
 // (from a dApp RPC call), not from a user gesture, so action.openPopup() is
 // unreliable in this context.
-function requestTxApproval(origin, hostname, txParams) {
+//
+// `approvedTx` is the fully populated transaction (see approvalTx.js): the
+// object the popup displays, the object it signs, and the object the artifact
+// is verified against. `approvedFrom` is the address that is active now, and
+// it is pinned here rather than read again at signing time — an address switch
+// between approval and signing must refuse, not sign from an account this
+// screen never named.
+function requestTxApproval(origin, hostname, approvedTx, approvedFrom) {
     return new Promise((resolve) => {
         const id = crypto.randomUUID();
         pendingApprovals[id] = {
             origin,
             hostname,
-            txParams,
+            approvedTx,
+            approvedFrom,
             resolve,
             type: "tx",
         };
@@ -244,13 +263,14 @@ function requestTxApproval(origin, hostname, txParams) {
 // Uses windows.create() directly because sign approvals are triggered programmatically
 // (from a dApp RPC call), not from a user gesture, so action.openPopup() is
 // unreliable in this context.
-function requestSignApproval(origin, hostname, signParams) {
+function requestSignApproval(origin, hostname, signParams, approvedFrom) {
     return new Promise((resolve) => {
         const id = crypto.randomUUID();
         pendingApprovals[id] = {
             origin,
             hostname,
             signParams,
+            approvedFrom,
             resolve,
             type: "sign",
         };
@@ -502,6 +522,16 @@ async function handleRpc(method, params, origin) {
                 ? { method, message: params[0], from: params[1] }
                 : { method, message: params[1], from: params[0] };
 
+        if (namesAnotherAddress(signParams.from, activeAddress)) {
+            return {
+                error: {
+                    code: 4100,
+                    message:
+                        "This site asked to sign as an address that is not the active one.",
+                },
+            };
+        }
+
         if (method === "eth_sign") {
             signParams.dangerWarning =
                 "\u26a0\ufe0f DANGER: This site is requesting to sign a raw hash. " +
@@ -513,6 +543,7 @@ async function handleRpc(method, params, origin) {
             origin,
             hostname,
             signParams,
+            activeAddress,
         );
         if (decision.error) return { error: decision.error };
         return { result: decision.signature };
@@ -534,10 +565,20 @@ async function handleRpc(method, params, origin) {
         }
 
         const signParams = { method, typedData: params[1], from: params[0] };
+        if (namesAnotherAddress(signParams.from, activeAddress)) {
+            return {
+                error: {
+                    code: 4100,
+                    message:
+                        "This site asked to sign as an address that is not the active one.",
+                },
+            };
+        }
         const decision = await requestSignApproval(
             origin,
             hostname,
             signParams,
+            activeAddress,
         );
         if (decision.error) return { error: decision.error };
         return { result: decision.signature };
@@ -559,7 +600,51 @@ async function handleRpc(method, params, origin) {
         }
 
         const txParams = params?.[0] || {};
-        const decision = await requestTxApproval(origin, hostname, txParams);
+        if (namesAnotherAddress(txParams.from, activeAddress)) {
+            return {
+                error: {
+                    code: 4100,
+                    message:
+                        "This site asked to send from an address that is not the active one.",
+                },
+            };
+        }
+
+        // Populate here, before any window opens, so that the transaction the
+        // user is shown is a complete one and is the same object the signed
+        // artifact is checked against. A failure raises no approval at all and
+        // is reported to the requesting page; see approvalTx.js.
+        let approvedTx;
+        try {
+            approvedTx = await prepareApprovalTx(
+                getProvider(await getRpcUrl()),
+                activeAddress,
+                txParams,
+            );
+        } catch (e) {
+            return { error: { message: e.message } };
+        }
+
+        // Population is a network round trip, and the user can switch address
+        // during it. Raising the approval anyway would put an account on the
+        // screen that the wallet is no longer on, and it could never be signed
+        // — the signing handler refuses exactly that. Refuse it here instead,
+        // while the page is still waiting and nothing has been displayed.
+        if (!sameAddress(await getActiveAddress(), activeAddress)) {
+            return {
+                error: {
+                    message:
+                        "The active address changed while this transaction was being prepared, so it was not sent.",
+                },
+            };
+        }
+
+        const decision = await requestTxApproval(
+            origin,
+            hostname,
+            approvedTx,
+            activeAddress,
+        );
         if (decision.error) return { error: decision.error };
         return { result: decision.txHash };
     }
@@ -810,11 +895,16 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
             };
             if (approval.type === "tx") {
                 resp.type = "tx";
-                resp.txParams = approval.txParams;
+                // The populated transaction, and the address it was raised
+                // for. The popup displays and signs exactly this and does not
+                // populate or re-read anything itself.
+                resp.approvedTx = approval.approvedTx;
+                resp.approvedFrom = approval.approvedFrom;
             }
             if (approval.type === "sign") {
                 resp.type = "sign";
                 resp.signParams = approval.signParams;
+                resp.approvedFrom = approval.approvedFrom;
             }
             // Flag if the requesting domain is on the phishing blocklist.
             resp.isPhishingDomain = isPhishingDomain(approval.hostname);
@@ -888,14 +978,27 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
             try {
                 await loadState();
                 const activeAddress = await getActiveAddress();
+                // An address switch between approval and signing refuses. The
+                // approval named one account; signing from whichever account
+                // is active now would send funds from an account this screen
+                // never showed. A switch normally rejects every pending
+                // approval on its way through broadcastAccountsChanged(), so
+                // this is the case where that did not reach the approval —
+                // and it is a refusal, not a retry, because the transaction
+                // the user saw is no longer the transaction that would go out.
+                if (!sameAddress(activeAddress, approval.approvedFrom)) {
+                    throw new ApprovalMismatchError(
+                        "The active address changed after this transaction was approved, so it was not sent.",
+                    );
+                }
                 // The popup holds the secret, but the background stays the
                 // authority on what is broadcast: the raw transaction must be
-                // the approved one, signed by the approved address, on the
+                // the transaction that was displayed, signed by the address
-                // network that is selected.
+                // the approval named, on the network that is selected.
                 verifySignedTx(
                     msg.rawSignedTx,
-                    approval.txParams,
+                    approval.approvedTx,
-                    activeAddress,
+                    approval.approvedFrom,
                     currentNetwork().chainId,
                 );
             } catch (e) {
@@ -932,10 +1035,10 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
                 sendResponse({ txHash: tx.hash });
             } catch (e) {
                 // Terminal, never retried: the node may have accepted the
-                // transaction and still failed to answer, and the popup's
+                // transaction and still failed to answer, so the wallet cannot
-                // retry re-signs at a freshly fetched nonce rather than
+                // tell a transaction that never left from one already in the
-                // re-broadcasting these bytes. Retrying would send the
+                // mempool. The page has been given its outcome for this
-                // approved transfer a second time.
+                // request; a second attempt would report a second one.
                 const outcome = describeTxFailure(TX_STAGE_BROADCAST, e);
                 settleApproval(
                     msg.id,
@@ -998,12 +1101,24 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
         (async () => {
             try {
                 const activeAddress = await getActiveAddress();
+                // Same as the transaction path: the address the approval named
+                // is the one that must have signed, and a switch since then is
+                // a refusal rather than a signature from another account.
+                if (!sameAddress(activeAddress, approval.approvedFrom)) {
+                    throw new ApprovalMismatchError(
+                        "The active address changed after this request was approved, so it was not signed.",
+                    );
+                }
                 // The popup holds the secret, but the background stays the
                 // authority on what is handed back to the page: the signature
-                // must cover the approved payload and recover to the approved
+                // must cover the approved payload and recover to the address
-                // address.
+                // the approval named.
                 const signature = msg.signature;
-                verifySignature(approval.signParams, signature, activeAddress);
+                verifySignature(
+                    approval.signParams,
+                    signature,
+                    approval.approvedFrom,
+                );
                 settleApproval(msg.id, { signature }, { holdsClaim: true });
                 sendResponse({ signature });
             } catch (e) {

src/popup/index.html

@@ -1496,6 +1496,33 @@
                     <div class="text-xs text-muted mb-1">Value</div>
                     <div id="approve-tx-value" class="text-xs font-bold"></div>
                 </div>
+                <div class="mb-3">
+                    <div class="text-xs text-muted mb-1">Network fee (max)</div>
+                    <div
+                        id="approve-tx-fee"
+                        class="text-xs font-bold min-h-[1rem]"
+                    ></div>
+                    <div
+                        id="approve-tx-fee-detail"
+                        class="text-xs text-muted min-h-[1rem]"
+                    ></div>
+                </div>
+                <div class="mb-3 flex justify-between">
+                    <div>
+                        <div class="text-xs text-muted mb-1">Network</div>
+                        <div
+                            id="approve-tx-network"
+                            class="text-xs min-h-[1rem]"
+                        ></div>
+                    </div>
+                    <div>
+                        <div class="text-xs text-muted mb-1">Nonce</div>
+                        <div
+                            id="approve-tx-nonce"
+                            class="text-xs min-h-[1rem]"
+                        ></div>
+                    </div>
+                </div>
                 <div id="approve-tx-data-section" class="mb-3 hidden">
                     <div class="text-xs text-muted mb-1">Raw data</div>
                     <div id="approve-tx-data" class="text-xs break-all"></div>

src/popup/views/approval.js

@@ -10,6 +10,7 @@ const {
     onViewLeave,
 } = require("./helpers");
 const { state, saveState, currentNetwork } = require("../../shared/state");
+const { networkByChainId } = require("../../shared/networks");
 const {
     formatEther,
     formatUnits,
@@ -23,7 +24,6 @@ const { TOKEN_BY_ADDRESS } = require("../../shared/tokenList");
 const { decryptWithPassword } = require("../../shared/vault");
 const { getSignerForAddress } = require("../../shared/wallet");
 const { walletDefect } = require("../../shared/walletDefects");
-const { getProvider } = require("../../shared/balances");
 const { describeSigningFailure } = require("../../shared/approvalVerify");
 const txStatus = require("./txStatus");
 const uniswap = require("../../shared/uniswap");
@@ -159,21 +159,61 @@ function showPhishingWarning(elementId, isPhishing) {
     }
 }
 
+// The fields of the approved transaction the value and recipient lines do not
+// already carry: network, gas limit, fee per gas, the most the fee can come to,
+// and the nonce. The background compares every one of them against the signed
+// artifact, so every one of them has to be on the screen — a number that is
+// verified but never displayed is verified against nothing the user agreed to.
+function showTxFee(approvedTx, ethPrice) {
+    const network = networkByChainId(approvedTx.chainId);
+    $("approve-tx-network").textContent = network
+        ? network.name
+        : "Unknown network (chain id " + BigInt(approvedTx.chainId) + ")";
+
+    const gasLimit = BigInt(approvedTx.gasLimit);
+    const feePerGas = BigInt(approvedTx.maxFeePerGas || approvedTx.gasPrice);
+    const maxFeeEth = formatTxValue(formatEther(gasLimit * feePerGas));
+    const usdStr = formatUsd(
+        ethPrice ? parseFloat(maxFeeEth) * ethPrice : null,
+    );
+    $("approve-tx-fee").textContent =
+        maxFeeEth + " ETH" + (usdStr ? " (" + usdStr + ")" : "");
+
+    let detail =
+        gasLimit.toString() +
+        " gas at up to " +
+        formatUnits(feePerGas, 9) +
+        " gwei";
+    if (approvedTx.maxPriorityFeePerGas) {
+        detail +=
+            ", " +
+            formatUnits(approvedTx.maxPriorityFeePerGas, 9) +
+            " gwei priority";
+    }
+    $("approve-tx-fee-detail").textContent = detail;
+    $("approve-tx-nonce").textContent = BigInt(approvedTx.nonce).toString();
+}
+
 function showTxApproval(details) {
     showPhishingWarning(
         "approve-tx-phishing-warning",
         details.isPhishingDomain,
     );
 
-    pendingTxParams = details.txParams;
+    // The transaction the background populated. It is displayed as it stands,
+    // signed as it stands, and verified against as it stands — the popup fills
+    // nothing in, so there is no number on this screen that the background
+    // cannot compare with the artifact it gets back.
+    pendingTxParams = details.approvedTx;
+    const approvedTx = details.approvedTx;
 
-    const toAddr = details.txParams.to;
+    const toAddr = approvedTx.to;
     const token = toAddr ? TOKEN_BY_ADDRESS.get(toAddr.toLowerCase()) : null;
-    const ethValue = formatEther(details.txParams.value || "0");
+    const ethValue = formatEther(approvedTx.value || "0");
 
     // Build txInfo for status screens
     pendingTxDetails = {
-        from: state.activeAddress,
+        from: details.approvedFrom,
         to: toAddr || "",
         amount: formatTxValue(ethValue),
         token: "ETH",
@@ -181,7 +221,7 @@ function showTxApproval(details) {
     };
 
     // If this is an ERC-20 call, try to extract the real recipient and amount
-    const decoded = decodeCalldata(details.txParams.data, toAddr || "");
+    const decoded = decodeCalldata(approvedTx.data, toAddr || "");
     if (decoded && decoded.details) {
         let decodedTokenAddr = null;
         let decodedTokenSymbol = null;
@@ -219,7 +259,7 @@ function showTxApproval(details) {
     }
 
     $("approve-tx-hostname").textContent = details.hostname;
-    $("approve-tx-from").innerHTML = approvalAddressHtml(state.activeAddress);
+    $("approve-tx-from").innerHTML = approvalAddressHtml(details.approvedFrom);
 
     // Show token symbol next to contract address if known
     const symbol = toAddr ? tokenLabel(toAddr) : null;
@@ -235,7 +275,7 @@ function showTxApproval(details) {
     }
 
     const ethValueFormatted = formatTxValue(
-        formatEther(details.txParams.value || "0"),
+        formatEther(approvedTx.value || "0"),
     );
     const ethPrice = getPrice("ETH");
     const ethUsd = ethPrice ? parseFloat(ethValueFormatted) * ethPrice : null;
@@ -243,6 +283,8 @@ function showTxApproval(details) {
     $("approve-tx-value").textContent =
         ethValueFormatted + " ETH" + (usdStr ? " (" + usdStr + ")" : "");
 
+    showTxFee(approvedTx, ethPrice);
+
     // Decode calldata (reuse decoded from above)
     const decodedEl = $("approve-tx-decoded");
     if (decoded) {
@@ -271,8 +313,8 @@ function showTxApproval(details) {
     }
 
     // Always show raw data when present
-    if (details.txParams.data && details.txParams.data !== "0x") {
+    if (approvedTx.data && approvedTx.data !== "0x") {
-        $("approve-tx-data").textContent = details.txParams.data;
+        $("approve-tx-data").textContent = approvedTx.data;
         $("approve-tx-data-section").classList.remove("hidden");
     } else {
         $("approve-tx-data-section").classList.add("hidden");
@@ -283,7 +325,11 @@ function showTxApproval(details) {
 
     showView("approve-tx");
     attachCopyHandlers("view-approve-tx");
-    gateOnWalletDefect("approve-tx-error", "btn-approve-tx");
+    gateOnWalletDefect(
+        "approve-tx-error",
+        "btn-approve-tx",
+        details.approvedFrom,
+    );
 }
 
 function decodeHexMessage(hex) {
@@ -342,9 +388,12 @@ function showSignApproval(details) {
 
     const sp = details.signParams;
     pendingSignParams = sp;
+    pendingSignFrom = details.approvedFrom;
 
     $("approve-sign-hostname").textContent = details.hostname;
-    $("approve-sign-from").innerHTML = approvalAddressHtml(sp.from);
+    $("approve-sign-from").innerHTML = approvalAddressHtml(
+        details.approvedFrom,
+    );
 
     const isTyped =
         sp.method === "eth_signTypedData_v4" ||
@@ -383,7 +432,11 @@ function showSignApproval(details) {
 
     showView("approve-sign");
     attachCopyHandlers("view-approve-sign");
-    gateOnWalletDefect("approve-sign-error", "btn-approve-sign");
+    gateOnWalletDefect(
+        "approve-sign-error",
+        "btn-approve-sign",
+        details.approvedFrom,
+    );
 }
 
 function show(id) {
@@ -418,11 +471,15 @@ function show(id) {
 
 let approvalId = null;
 let pendingTxDetails = null;
-// The exact parameters shown to the user, kept so the popup signs what it
+// The exact objects shown to the user, kept so the popup signs what it
-// displayed rather than re-fetching anything at approval time. Both are
+// displayed rather than re-fetching or re-populating anything at approval
-// repopulated by show() when the popup is closed and reopened.
+// time. All are repopulated by show() when the popup is closed and reopened.
 let pendingTxParams = null;
 let pendingSignParams = null;
+// The address the approval was raised for. Signing uses this rather than the
+// active address, so that an address switch since the approval fails here
+// instead of producing a signature from an account the screen never named.
+let pendingSignFrom = null;
 
 // Approve buttons stay disabled and muted while the popup derives the key and
 // signs, which is slow enough (Argon2id) that a double click is likely.
@@ -437,12 +494,13 @@ function setSignButtonBusy(busy) {
 }
 
 // Say so on the approval screen itself, and disable the approve button, when
-// the active address belongs to a wallet whose keys cannot be derived. Without
+// the address the approval was raised for belongs to a wallet whose keys
-// this the screen would take a password and fail after deriving it. Reject
+// cannot be derived. Without this the screen would take a password and fail
-// stays available; the wallet is not touched. Returns true when it gated.
+// after deriving it. Reject stays available; the wallet is not touched.
-function gateOnWalletDefect(errorId, buttonId) {
+// Returns true when it gated.
-    const active = findActiveWallet();
+function gateOnWalletDefect(errorId, buttonId, address) {
-    const defect = active ? walletDefect(active.wallet) : null;
+    const owner = findWalletFor(address);
+    const defect = owner ? walletDefect(owner.wallet) : null;
     if (!defect) return false;
     showError(errorId, defect.shortMessage);
     $(buttonId).disabled = true;
@@ -450,12 +508,14 @@ function gateOnWalletDefect(errorId, buttonId) {
     return true;
 }
 
-// Locate the wallet and the address index owning the currently active
+// Locate the wallet and the address index owning an address. Returns null when
-// address. Returns null when no wallet holds it.
+// no wallet holds it. Approvals look up the address they were raised for, not
-function findActiveWallet() {
+// whichever address is active now: the approval named one account, and signing
+// with another is what verification refuses.
+function findWalletFor(address) {
     for (const wallet of state.wallets) {
         for (let i = 0; i < wallet.addresses.length; i++) {
-            if (wallet.addresses[i].address === state.activeAddress) {
+            if (wallet.addresses[i].address === address) {
                 return { wallet, addrIndex: i };
             }
         }
@@ -517,12 +577,12 @@ function init(ctx) {
         hideError("approve-tx-error");
         setTxButtonBusy(true);
 
-        const active = findActiveWallet();
+        const active = findWalletFor(pendingTxParams.from);
         if (!active) {
             password = null;
             showError(
                 "approve-tx-error",
-                "No wallet was found for the active address.",
+                "No wallet was found for the address this transaction was approved for.",
             );
             setTxButtonBusy(false);
             return;
@@ -569,15 +629,16 @@ function init(ctx) {
                 active.addrIndex,
                 decryptedSecret,
             );
-            const provider = getProvider(state.rpcUrl);
+            // Sign the approved transaction exactly as it was displayed. The
-            const connected = signer.connect(provider);
+            // background populated it before this screen was drawn and checks
-            // This is the sequence ethers' own sendTransaction() runs
+            // the artifact against it field for field, so there is nothing to
-            // internally, so nonce, gas, fee and chain id population are
+            // fill in here and no provider to fill it in from. The copy is
-            // identical to when the background did the signing.
+            // because ethers may strip `from` off what it is handed, and the
-            const populated =
+            // approval has to survive a retry intact; keeping `from` on it
-                await connected.populateTransaction(pendingTxParams);
+            // makes ethers refuse a key that is not the approved address.
-            delete populated.from;
+            payload.rawSignedTx = await signer.signTransaction({
-            payload.rawSignedTx = await connected.signTransaction(populated);
+                ...pendingTxParams,
+            });
         } catch (e) {
             payload.error =
                 e.shortMessage || e.message || "Transaction signing failed.";
@@ -626,12 +687,12 @@ function init(ctx) {
         hideError("approve-sign-error");
         setSignButtonBusy(true);
 
-        const active = findActiveWallet();
+        const active = findWalletFor(pendingSignFrom);
         if (!active) {
             password = null;
             showError(
                 "approve-sign-error",
-                "No wallet was found for the active address.",
+                "No wallet was found for the address this request was approved for.",
             );
             setSignButtonBusy(false);
             return;

src/shared/approvalTx.js

@@ -0,0 +1,213 @@
+// Preparation of the transaction an approval screen displays.
+//
+// A dApp's eth_sendTransaction normally fixes only `to`, `value` and `data`.
+// The nonce, the gas limit and the fees have to be filled in from the network
+// before anything can be signed, and whoever fills them in decides what the
+// user is shown. That work used to happen in the popup, after the user had
+// already approved: the numbers on the approval screen came from the popup and
+// were compared against nothing, so a compromised popup could display one fee
+// and sign another, and the ceilings in approvalVerify.js were all that stood
+// between the user and a fee that hands the validator the balance.
+//
+// So it happens here instead, in the background, before the approval window is
+// opened. The background populates the transaction, shows that object, and
+// verifies the signed artifact against that same object — the popup is handed
+// a finished transaction and signs it as given. Every field the user reads is
+// then a field that is compared.
+//
+// The cost is an RPC round trip before the approval window exists. Nothing is
+// displayed while it is in flight, and a failure — an unreachable node, a
+// reverting gas estimate, a transaction type this wallet does not sign, a fee
+// past the ceilings — means no approval and no window at all: the error goes
+// back to the requesting page, which is where the user's click came from. That
+// is deliberate. The alternative, opening the window first and populating
+// behind a spinner, needs a pending approval that exists before it can be
+// displayed or signed, and a half-initialised approval is exactly the state
+// the settle interlock in the background exists to keep out of that record.
+// The failure also lands earlier than it used to rather than later: the same
+// estimate previously failed after the user had typed their password.
+
+const {
+    VoidSigner,
+    accessListify,
+    getAddress,
+    getBytes,
+    hexlify,
+    toQuantity,
+} = require("ethers");
+const {
+    ALLOWED_TX_TYPES,
+    SERIALIZED_FIELDS,
+    assertWithinCeilings,
+} = require("./approvalVerify");
+
+// How long the population may take before the request is failed back to the
+// page. Without a bound a hung RPC endpoint leaves the dApp's promise pending
+// forever with nothing on screen to explain it; ethers' own request timeout is
+// minutes long, which is not a wait anyone will sit through.
+const POPULATE_TIMEOUT_MS = 20000;
+
+// The request fields taken from the page. Anything else is dropped rather than
+// passed to ethers: the object is page-controlled, and a future ethers that
+// learns to carry a new transaction field must not start picking one up out of
+// it without this module knowing.
+const REQUEST_FIELDS = [
+    "to",
+    "value",
+    "data",
+    "nonce",
+    "gasLimit",
+    "gasPrice",
+    "maxFeePerGas",
+    "maxPriorityFeePerGas",
+    "chainId",
+    "accessList",
+    "type",
+];
+
+class ApprovalPrepareError extends Error {
+    constructor(message) {
+        super(message);
+        this.name = "ApprovalPrepareError";
+    }
+}
+
+function fail(message) {
+    return new ApprovalPrepareError(message);
+}
+
+function present(v) {
+    return v !== null && v !== undefined && v !== "";
+}
+
+// These strings reach the user through the requesting page, so they are full
+// sentences even when the tail of one came from ethers or from the node.
+function sentence(text) {
+    return /[.!?]$/.test(text) ? text : text + ".";
+}
+
+// Reject a promise that has taken too long, and never leave the timer behind.
+async function withTimeout(promise, ms, message) {
+    let timer = null;
+    try {
+        return await Promise.race([
+            promise,
+            new Promise((_resolve, reject) => {
+                timer = setTimeout(() => reject(fail(message)), ms);
+            }),
+        ]);
+    } finally {
+        if (timer !== null) clearTimeout(timer);
+    }
+}
+
+// The page's request, reduced to the fields this wallet acts on.
+function requestFrom(txParams, from) {
+    const request = { from: getAddress(from) };
+    for (const key of REQUEST_FIELDS) {
+        if (present(txParams[key])) request[key] = txParams[key];
+    }
+    if (
+        present(request.type) &&
+        !ALLOWED_TX_TYPES.includes(Number(request.type))
+    ) {
+        throw fail(
+            "The site asked for a transaction of a type this wallet does not sign.",
+        );
+    }
+    return request;
+}
+
+// Turn a populated transaction into the object that crosses to the popup, is
+// displayed, and is compared with the signed artifact. It carries exactly the
+// fields its type serializes, plus the address it is to be signed by, and
+// every quantity as a hex string: extension messaging is JSON, which has no
+// bigint, and a field that did not survive the trip would be a field the user
+// was shown and nothing compared.
+function serializeApprovedTx(populated, from) {
+    const type = Number(populated.type);
+    if (!ALLOWED_TX_TYPES.includes(type)) {
+        throw fail(
+            "This transaction would have to be sent as a type this wallet does not sign.",
+        );
+    }
+    const approved = { type, from: getAddress(from) };
+    for (const key of SERIALIZED_FIELDS[type]) {
+        if (key === "to") {
+            approved.to = present(populated.to)
+                ? getAddress(populated.to)
+                : null;
+        } else if (key === "data") {
+            approved.data = present(populated.data)
+                ? hexlify(getBytes(populated.data))
+                : "0x";
+        } else if (key === "accessList") {
+            approved.accessList = accessListify(populated.accessList || []);
+        } else if (key === "value") {
+            approved.value = toQuantity(populated.value || 0);
+        } else if (!present(populated[key])) {
+            // Unreachable while populateTransaction() fills every quantity of
+            // the type it produced. If it ever does not, the approval must not
+            // be raised: an unfixed quantity is one the artifact cannot be
+            // checked against.
+            throw fail(
+                "The transaction could not be prepared: the network did not supply a " +
+                    key +
+                    ".",
+            );
+        } else {
+            approved[key] = toQuantity(populated[key]);
+        }
+    }
+    return approved;
+}
+
+// Populate the transaction a site asked for, as the address it will be signed
+// by, and return the object to display, sign and verify against. Throws with a
+// full sentence when no approval can be raised.
+async function prepareApprovalTx(provider, from, txParams) {
+    if (!present(from)) {
+        throw fail("There is no active address to send this transaction from.");
+    }
+    const request = requestFrom(txParams || {}, from);
+
+    let populated;
+    try {
+        // The sequence ethers' own sendTransaction() runs internally, so the
+        // nonce, gas, fee and chain id are populated exactly as they were when
+        // the popup did this. VoidSigner cannot sign, which is the point: the
+        // background prepares, the popup signs.
+        populated = await withTimeout(
+            new VoidSigner(getAddress(from), provider).populateTransaction(
+                request,
+            ),
+            POPULATE_TIMEOUT_MS,
+            "The transaction could not be prepared: the network did not answer in time.",
+        );
+    } catch (e) {
+        if (e instanceof ApprovalPrepareError) throw e;
+        throw fail(
+            sentence(
+                "The transaction could not be prepared: " +
+                    (e.shortMessage ||
+                        e.message ||
+                        "the network did not answer"),
+            ),
+        );
+    }
+
+    const approved = serializeApprovedTx(populated, from);
+    // The backstop, applied before the user is shown anything rather than
+    // after they have approved it: what is displayed here is what gets signed,
+    // so an RPC node reporting an absurd fee has to be refused here.
+    assertWithinCeilings(approved);
+    return approved;
+}
+
+module.exports = {
+    prepareApprovalTx,
+    serializeApprovedTx,
+    ApprovalPrepareError,
+    POPULATE_TIMEOUT_MS,
+    REQUEST_FIELDS,
+};

src/shared/approvalVerify.js

@@ -7,6 +7,13 @@
 // the signer from the artifact and checks it against the approval it is
 // holding before acting on it. All recovery is delegated to ethers.
 //
+// What the artifact is checked against is the transaction the background
+// populated and the popup displayed (see approvalTx.js), not the request the
+// dApp made. The two differ in every field a dApp normally leaves out — nonce,
+// gas limit, fees — and those are the fields the user reads off the approval
+// screen, so comparing against the request would leave the numbers on screen
+// vouched for by nothing.
+//
 // The check is an allowlist, in both directions, because a denylist cannot be
 // correct against a transaction format that keeps gaining fields:
 //
@@ -31,14 +38,12 @@
 // never a warning: what the user approved is what gets broadcast, or nothing
 // does.
 //
-// Fields the approval does not carry are not treated as zero. The popup
+// The approved transaction is required to fix every field its type serializes,
-// populates nonce, gas limit, fee and chain id through populateTransaction()
+// so there is no "the approval did not say" branch to fall through: a quantity
-// when the requesting page did not fix them, so there is no approved value to
+// the approval does not carry is a refusal, because an artifact that cannot be
-// compare against; treating absent as zero would refuse every legitimate
+// compared with what was displayed has not been checked. The chain id is
-// transaction. Those fields are instead held to the absolute ceilings below,
+// checked against the selected network as well as against the approval, which
-// and the chain id is always checked against the selected network rather than
+// is what makes a cross-chain replay impossible.
-// against the approval alone, which is what makes a cross-chain replay
-// impossible.
 //
 // Every failure message is a full sentence, because these strings are shown to
 // the user and returned to the dApp.
@@ -113,6 +118,17 @@ const FORBIDDEN_FIELDS = [
     },
 ];
 
+// Absolute ceilings — a BACKSTOP, not the primary control.
+//
+// The primary control is equality: every field of the artifact is compared
+// with the populated transaction the user was shown, so nothing the popup
+// signs can differ from the screen. What equality cannot bound is the
+// populated transaction itself, which is built from what the configured RPC
+// node answered — a node that reports an absurd fee gets that fee displayed,
+// and a user who does not read the fee line would approve it. These ceilings
+// bound that, and they are therefore applied where the transaction is
+// populated (approvalTx.js) as well as here.
+//
 // Above the block gas limit of every supported network (see networks.js), so
 // no transaction that could ever be included is refused by it.
 const MAX_GAS_LIMIT = 100000000n;
@@ -224,40 +240,151 @@ function normalizeData(v) {
     return String(v).toLowerCase();
 }
 
-// Quantity fields the requesting page may fix in the approval. Each is
+// How each field of an approved transaction is compared with the artifact.
-// compared exactly when the approval carries it, and left to the ceilings
+// There is an entry here for every field any allowed type serializes — a test
-// above when it does not.
+// pins that against SERIALIZED_FIELDS — so the comparison loop covers the
-const APPROVED_QUANTITIES = [
+// whole of what gets signed and cannot silently skip a field for want of a
-    {
+// comparator.
-        key: "nonce",
+//
+// `kind` decides how the two sides are made comparable. A `quantity` must be
+// fixed by the approval: it is one of the numbers on the approval screen, and
+// an absent one means the artifact cannot be checked against what was
+// displayed. `to`, `value`, `data` and `accessList` have canonical absent
+// forms — contract creation, zero, "0x" and the empty list — so they are
+// normalized on both sides instead.
+const APPROVED_FIELDS = {
+    chainId: {
+        kind: "quantity",
+        label: "network",
+        message:
+            "The signed transaction is for a different network than the one that was approved.",
+    },
+    nonce: {
+        kind: "quantity",
         label: "nonce",
         message: "The signed transaction does not carry the approved nonce.",
     },
-    {
+    gasLimit: {
-        key: "gasLimit",
+        kind: "quantity",
         label: "gas limit",
         message:
             "The signed transaction does not carry the approved gas limit.",
     },
-    {
+    gasPrice: {
-        key: "gasPrice",
+        kind: "quantity",
         label: "gas price",
         message:
             "The signed transaction does not carry the approved gas price.",
     },
-    {
+    maxFeePerGas: {
-        key: "maxFeePerGas",
+        kind: "quantity",
         label: "maximum fee per gas",
         message:
             "The signed transaction does not carry the approved maximum fee per gas.",
     },
-    {
+    maxPriorityFeePerGas: {
-        key: "maxPriorityFeePerGas",
+        kind: "quantity",
         label: "maximum priority fee per gas",
         message:
             "The signed transaction does not carry the approved maximum priority fee per gas.",
     },
-];
+    to: {
+        kind: "address",
+        label: "recipient",
+        message:
+            "The signed transaction does not go to the approved recipient.",
+    },
+    value: {
+        kind: "value",
+        label: "value",
+        message: "The signed transaction does not carry the approved value.",
+    },
+    data: {
+        kind: "data",
+        label: "call data",
+        message:
+            "The signed transaction does not carry the approved call data.",
+    },
+    accessList: {
+        kind: "accessList",
+        label: "access list",
+        message:
+            "The signed transaction does not carry the approved access list.",
+    },
+};
+
+// Compare one field of the artifact with the approved transaction. A field
+// with no entry in the table above is refused rather than skipped: the loop
+// below runs over the fields the type serializes, so an unmatched key means
+// something that gets signed has no comparator at all.
+function assertFieldMatches(key, parsed, approvedTx) {
+    const field = APPROVED_FIELDS[key];
+    if (!field) {
+        throw refuse(
+            "The signed transaction carries a field this wallet cannot compare with the approval.",
+        );
+    }
+    switch (field.kind) {
+        case "quantity": {
+            if (!present(approvedTx[key])) {
+                throw refuse(
+                    "The approved transaction fixes no " +
+                        field.label +
+                        ", so the signed transaction cannot be checked" +
+                        " against what was shown.",
+                );
+            }
+            const approved = normalizeQuantity(approvedTx[key], field.label);
+            if (normalizeQuantity(parsed[key], field.label) !== approved) {
+                throw refuse(field.message);
+            }
+            return;
+        }
+        case "address":
+            if (!sameAddress(parsed[key], approvedTx[key])) {
+                throw refuse(field.message);
+            }
+            return;
+        case "value":
+            if (normalizeValue(parsed[key]) !== normalizeValue(approvedTx[key]))
+                throw refuse(field.message);
+            return;
+        case "data":
+            if (normalizeData(parsed[key]) !== normalizeData(approvedTx[key]))
+                throw refuse(field.message);
+            return;
+        default:
+            if (
+                normalizeAccessList(parsed[key]) !==
+                normalizeAccessList(approvedTx[key])
+            ) {
+                throw refuse(field.message);
+            }
+    }
+}
+
+// The ceilings, applied to a transaction that is either about to be displayed
+// or about to be broadcast. See MAX_GAS_LIMIT above for what they are for:
+// they bound what the RPC node can talk this wallet into showing the user,
+// which is the one thing comparing the artifact with the screen cannot do.
+function assertWithinCeilings(tx) {
+    if (
+        present(tx.gasLimit) &&
+        normalizeQuantity(tx.gasLimit, "gas limit") > MAX_GAS_LIMIT
+    ) {
+        throw refuse(
+            "The signed transaction sets a gas limit no network this wallet supports can accept.",
+        );
+    }
+    for (const key of ["gasPrice", "maxFeePerGas", "maxPriorityFeePerGas"]) {
+        if (!present(tx[key])) continue;
+        if (normalizeQuantity(tx[key], "fee per gas") > MAX_FEE_PER_GAS) {
+            throw refuse(
+                "The signed transaction sets a fee per gas far above any plausible value.",
+            );
+        }
+    }
+}
 
 // Refuse a field only a transaction type this wallet does not sign can carry.
 // The type allowlist keeps these unreachable in production, which is exactly
@@ -317,10 +444,28 @@ function assertCanonicalBytes(parsed, rawSignedTx) {
 // signed by the address the approval was raised for, on the network that is
 // selected. Returns the parsed ethers Transaction on success, throws
 // otherwise.
-function verifySignedTx(rawSignedTx, txParams, expectedFrom, selectedChainId) {
+//
+// `approvedTx` is the populated transaction the approval screen displayed, and
+// `expectedFrom` is the address that was active when the approval was raised —
+// not whichever address is active now. An address switch between approval and
+// signing therefore refuses here rather than producing a transaction from an
+// account the approval did not name.
+function verifySignedTx(
+    rawSignedTx,
+    approvedTx,
+    expectedFrom,
+    selectedChainId,
+) {
     if (typeof rawSignedTx !== "string" || !rawSignedTx.startsWith("0x")) {
         throw refuse("The signed transaction is missing or malformed.");
     }
+    // Nothing to compare against is a refusal like any other: an approval that
+    // does not carry the transaction it displayed cannot vouch for one.
+    if (!approvedTx || typeof approvedTx !== "object") {
+        throw refuse(
+            "There is no approved transaction to check the signed transaction against.",
+        );
+    }
 
     let parsed;
     try {
@@ -360,46 +505,15 @@ function verifySignedTx(rawSignedTx, txParams, expectedFrom, selectedChainId) {
             "The signed transaction is for a different network than the one that is selected.",
         );
     }
-    if (
-        present(txParams.chainId) &&
-        parsed.chainId !== normalizeQuantity(txParams.chainId, "network")
-    ) {
-        throw refuse(
-            "The signed transaction is for a different network than the one that was approved.",
-        );
-    }
 
-    if (!sameAddress(parsed.to, txParams.to)) {
+    // The approved fee mechanism, named before the type comparison below
-        throw refuse(
+    // subsumes it: the fee the user agreed to is only meaningful under the
-            "The signed transaction does not go to the approved recipient.",
+    // mechanism it was quoted in, and saying so is more use than "a different
-        );
+    // transaction type".
-    }
-    if (normalizeValue(parsed.value) !== normalizeValue(txParams.value)) {
-        throw refuse(
-            "The signed transaction does not carry the approved value.",
-        );
-    }
-    if (normalizeData(parsed.data) !== normalizeData(txParams.data)) {
-        throw refuse(
-            "The signed transaction does not carry the approved call data.",
-        );
-    }
-    if (
-        normalizeAccessList(parsed.accessList) !==
-        normalizeAccessList(txParams.accessList)
-    ) {
-        throw refuse(
-            "The signed transaction does not carry the approved access list.",
-        );
-    }
-
-    // An approval that fixed EIP-1559 fees must not be signed as a legacy
-    // transaction, and vice versa: the fee the user agreed to is only
-    // meaningful under the mechanism it was quoted in.
     const approvedEip1559 =
-        present(txParams.maxFeePerGas) ||
+        present(approvedTx.maxFeePerGas) ||
-        present(txParams.maxPriorityFeePerGas);
+        present(approvedTx.maxPriorityFeePerGas);
-    const approvedLegacy = present(txParams.gasPrice);
+    const approvedLegacy = present(approvedTx.gasPrice);
     const signedEip1559 = parsed.type === 2;
     if (
         (approvedEip1559 && !signedEip1559) ||
@@ -410,28 +524,33 @@ function verifySignedTx(rawSignedTx, txParams, expectedFrom, selectedChainId) {
         );
     }
 
-    for (const field of APPROVED_QUANTITIES) {
+    // The type decides which fields are compared, so it is compared first and
-        if (!present(txParams[field.key])) continue;
+    // against the approval, not merely checked for membership of the
-        const approved = normalizeQuantity(txParams[field.key], field.label);
+    // allowlist above.
-        if (normalizeQuantity(parsed[field.key], field.label) !== approved) {
+    if (!present(approvedTx.type)) {
-            throw refuse(field.message);
+        throw refuse(
+            "The approved transaction fixes no transaction type, so the signed transaction cannot be checked against what was shown.",
+        );
     }
+    if (
+        BigInt(parsed.type) !==
+        normalizeQuantity(approvedTx.type, "transaction type")
+    ) {
+        throw refuse(
+            "The signed transaction does not use the approved transaction type.",
+        );
     }
 
-    if (parsed.gasLimit > MAX_GAS_LIMIT) {
+    // Every field this type serializes, compared with the transaction the user
-        throw refuse(
+    // was shown. Driving the loop off SERIALIZED_FIELDS is what keeps this
-            "The signed transaction sets a gas limit no network this wallet supports can accept.",
+    // exhaustive: the same table decides what assertNothingUnchecked() rebuilds
-        );
+    // from, so a field that gets signed and is not compared here cannot exist.
-    }
+    for (const key of SERIALIZED_FIELDS[parsed.type]) {
-    for (const key of ["gasPrice", "maxFeePerGas", "maxPriorityFeePerGas"]) {
+        assertFieldMatches(key, parsed, approvedTx);
-        const fee = parsed[key];
-        if (fee !== null && fee !== undefined && fee > MAX_FEE_PER_GAS) {
-            throw refuse(
-                "The signed transaction sets a fee per gas far above any plausible value.",
-            );
-        }
     }
 
+    assertWithinCeilings(parsed);
+
     assertNothingUnchecked(parsed);
     assertCanonicalBytes(parsed, rawSignedTx);
 
@@ -504,10 +623,10 @@ function errorText(err) {
 //    approval. Anything else failed before the check ran and is retryable.
 //  - broadcast: always terminal. A broadcast that throws after the node
 //    accepted the transaction is routine (a timeout, a dropped response, a
-//    node answering "already known"), and the popup's retry does not
+//    node answering "already known"), so the wallet cannot tell a transaction
-//    re-broadcast these bytes — it re-runs populateTransaction() and signs
+//    that never left from one that is already in the mempool. The approval is
-//    again at a freshly fetched pending-tag nonce. Retrying would therefore
+//    spent and the requesting page has been given its outcome; a second
-//    put a second transaction on the chain for one approval.
+//    attempt against it would report a second outcome for one request.
 function describeTxFailure(stage, err) {
     const error = errorText(err);
     const retryable =
@@ -553,6 +672,7 @@ module.exports = {
     assertNoForbiddenFields,
     assertNothingUnchecked,
     assertCanonicalBytes,
+    assertWithinCeilings,
     sameAddress,
     failureIsRetryable,
     describeTxFailure,
@@ -561,6 +681,7 @@ module.exports = {
     ALLOWED_TX_TYPES,
     SERIALIZED_FIELDS,
     FORBIDDEN_FIELDS,
+    APPROVED_FIELDS,
     TX_STAGE_SIGN,
     TX_STAGE_VERIFY,
     TX_STAGE_BROADCAST,

src/shared/symbolSpoof.js

@@ -32,43 +32,50 @@ function normalizeAddress(addr) {
 //   NFKC        collapses compatibility variants that render as the ASCII
 //               letters they imitate — fullwidth ETH, styled mathematical
 //               letters — and maps the non-ASCII spaces onto U+0020.
-//   strip       drops \p{Cf} plus \p{Default_Ignorable_Code_Point}: the
+//   strip       drops what paints nothing: \p{Cf} plus
-//               format characters (zero-width space, joiner and non-joiner,
+//               \p{Default_Ignorable_Code_Point} plus U+007F.  That covers
-//               word joiner, soft hyphen, byte-order mark, bidi marks and
+//               the format characters (zero-width space, joiner and
-//               overrides), the variation selectors, and the Hangul
+//               non-joiner, word joiner, soft hyphen, byte-order mark, bidi
-//               fillers.  \p{Cf} alone is not the class of things that
+//               marks and overrides), the variation selectors, the Hangul
-//               paint nothing — a Hangul filler is Lo and a variation
+//               fillers, and DELETE.  Removed everywhere, not merely at the
-//               selector is Mn, and both are as invisible as a zero-width
+//               ends.
-//               space.  Removed everywhere, not merely at the ends.
 //   trim        removes surrounding whitespace, which HTML collapses:
 //               `" ETH "` is painted next to the user's real ETH as `ETH`.
 //   toUpperCase makes the comparison case-insensitive, as before.
 //
-// The class is Unicode's, so what it covers is a definition rather than a
+// The rule is "strip what paints nothing".  The Unicode classes are how
-// measurement; measured in the repo's pinned e2e Chromium (16px sans-serif,
+// that is spelled, not what it means, which is why U+007F is named on its
-// plain `ETH` = 32.00px), every stripped character paints nothing except
+// own: it is a control rather than a default-ignorable character, so no
-// U+1160 and U+FFA0, which font fallback draws as a box.  Stripping those
+// class here reaches it, yet it paints nothing all the same.  Measured in
-// two hides a token that does not look like the symbol, which is the
+// the repo's pinned e2e Chromium (16px sans-serif, plain `ETH` = 32.00px,
-// harmless direction of the two.
+// so an invisible prefix leaves 32.00px):
+//
+//   U+007F, U+3164, U+115F, U+FE0F, U+FE00   32.00px — invisible
+//   U+FFA0                                   40.00px — a box
+//   U+1160                                   48.00px — a box
+//   U+0001, U+0085, U+0090                   48.00px — a box
+//
+// U+1160 and U+FFA0 are `Default_Ignorable_Code_Point` members that font
+// fallback nonetheless draws, and they are stripped anyway: erring toward
+// hiding a token that does not look like `ETH` is the harmless direction of
+// the two.  The other controls are left alone for the same reason read the
+// other way — a symbol carrying a visible box does not reach the eye as
+// `ETH`, so filtering it would hide a token the user could not have
+// confused with the native asset.
 //
 // Deliberately not folded, and asserted as open in tests/symbolSpoof.test.js:
 // interior whitespace (`E T H` renders as `E T H`, so folding it would filter
 // a token nobody could confuse with the native asset), confusables that are
 // distinct letters rather than compatibility variants (Cyrillic capital Ie,
-// U+0415; Greek capital Epsilon, U+0395), and bidi reordering, which needs
+// U+0415; Greek capital Epsilon, U+0395), bidi reordering, which needs the
-// the bidi algorithm rather than a character filter.  The C0/C1 controls are
+// bidi algorithm rather than a character filter, and the visible controls.
-// left alone because they render as a visible box (48.00px) — except U+007F,
-// which measures 32.00px, i.e. invisible and still not caught.  That one is
-// a live gap, flagged rather than closed here because it is a control
-// character rather than a default-ignorable one and the class to strip is a
-// decision of its own.
 //
 // This decides only how the question is asked.  Nothing here changes what a
 // surface displays; a token still shows the symbol it reports.
 function normalizeSymbol(symbol) {
     return String(symbol || "")
         .normalize("NFKC")
-        .replace(/[\p{Cf}\p{Default_Ignorable_Code_Point}]/gu, "")
+        .replace(/[\p{Cf}\p{Default_Ignorable_Code_Point}\x7F]/gu, "")
         .trim()
         .toUpperCase();
 }

tests/approvalTx.test.js

@@ -0,0 +1,309 @@
+// Preparation of the transaction the approval screen displays.
+//
+// This is the half of the fix that makes the verification in
+// approvalVerify.test.js mean anything: the numbers the user reads have to be
+// produced before the screen is drawn and be the numbers that get signed. What
+// is asserted here is that the object leaving this module is complete (nothing
+// is left for the popup to fill in), that it survives the messaging boundary
+// (extension messaging is JSON, which has no bigint), and that nothing the
+// requesting page or the RPC node can say turns it into an approval that
+// should never have been raised.
+
+const { Network, Wallet } = require("ethers");
+const {
+    prepareApprovalTx,
+    serializeApprovedTx,
+    POPULATE_TIMEOUT_MS,
+} = require("../src/shared/approvalTx");
+const {
+    SERIALIZED_FIELDS,
+    MAX_FEE_PER_GAS,
+    MAX_GAS_LIMIT,
+} = require("../src/shared/approvalVerify");
+
+const SIGNER_KEY =
+    "0x59c6995e998f97a5a0044966f0945389dc9e86dae88c7a8412f4603b6b78690d";
+const signer = new Wallet(SIGNER_KEY);
+const RECIPIENT = "0x66133E8ea0f5D1d612D2502a968757D1048c214a";
+
+// The ordinary dApp request: recipient, value, call data, and nothing else.
+const TX_PARAMS = {
+    from: signer.address,
+    to: RECIPIENT,
+    value: "0x2386f26fc10000",
+    data: "0xdeadbeef",
+};
+
+function providerWith(overrides) {
+    return {
+        getNetwork: async () => Network.from(1),
+        getTransactionCount: async () => 7,
+        estimateGas: async () => 21000n,
+        getFeeData: async () => ({
+            gasPrice: 2000000000n,
+            maxFeePerGas: 2000000000n,
+            maxPriorityFeePerGas: 1000000000n,
+        }),
+        ...(overrides || {}),
+    };
+}
+
+// A node that only quotes a flat gas price, so populateTransaction produces a
+// legacy transaction rather than an EIP-1559 one.
+const legacyProvider = providerWith({
+    getFeeData: async () => ({
+        gasPrice: 2000000000n,
+        maxFeePerGas: null,
+        maxPriorityFeePerGas: null,
+    }),
+});
+
+describe("prepareApprovalTx", () => {
+    test("fills in everything the request left out", async () => {
+        const approved = await prepareApprovalTx(
+            providerWith(),
+            signer.address,
+            TX_PARAMS,
+        );
+        expect(approved).toEqual({
+            type: 2,
+            from: signer.address,
+            chainId: "0x1",
+            nonce: "0x7",
+            gasLimit: "0x5208",
+            maxPriorityFeePerGas: "0x3b9aca00",
+            maxFeePerGas: "0x77359400",
+            to: RECIPIENT,
+            value: TX_PARAMS.value,
+            data: TX_PARAMS.data,
+            accessList: [],
+        });
+    });
+
+    // The object is displayed, signed and verified against on the far side of
+    // chrome.runtime.sendMessage, which is JSON: a bigint would throw on the
+    // way out and a field that did not survive the trip would be a field the
+    // user was shown and nothing compared.
+    test("survives the messaging boundary unchanged", async () => {
+        const approved = await prepareApprovalTx(
+            providerWith(),
+            signer.address,
+            TX_PARAMS,
+        );
+        expect(JSON.parse(JSON.stringify(approved))).toEqual(approved);
+        for (const value of Object.values(approved)) {
+            expect(typeof value).not.toBe("bigint");
+        }
+    });
+
+    test("carries exactly the fields its type serializes, and the signer", async () => {
+        const approved = await prepareApprovalTx(
+            providerWith(),
+            signer.address,
+            TX_PARAMS,
+        );
+        expect(Object.keys(approved).sort()).toEqual(
+            ["type", "from", ...SERIALIZED_FIELDS[2]].sort(),
+        );
+    });
+
+    test("produces a legacy transaction when that is all the node quotes", async () => {
+        const approved = await prepareApprovalTx(
+            legacyProvider,
+            signer.address,
+            TX_PARAMS,
+        );
+        expect(approved.type).toBe(0);
+        expect(approved.gasPrice).toBe("0x77359400");
+        expect(approved.maxFeePerGas).toBeUndefined();
+        expect(Object.keys(approved).sort()).toEqual(
+            ["type", "from", ...SERIALIZED_FIELDS[0]].sort(),
+        );
+    });
+
+    test("keeps a nonce, gas limit and fee the request did fix", async () => {
+        const approved = await prepareApprovalTx(
+            providerWith(),
+            signer.address,
+            {
+                ...TX_PARAMS,
+                nonce: "0x2",
+                gasLimit: "0x30d40",
+                maxFeePerGas: "0x12a05f200",
+                maxPriorityFeePerGas: "0x3b9aca00",
+            },
+        );
+        expect(approved.nonce).toBe("0x2");
+        expect(approved.gasLimit).toBe("0x30d40");
+        expect(approved.maxFeePerGas).toBe("0x12a05f200");
+    });
+
+    test("carries an access list the request asked for", async () => {
+        const approved = await prepareApprovalTx(
+            providerWith(),
+            signer.address,
+            {
+                ...TX_PARAMS,
+                accessList: [{ address: RECIPIENT, storageKeys: [] }],
+            },
+        );
+        expect(approved.accessList).toEqual([
+            { address: RECIPIENT, storageKeys: [] },
+        ]);
+    });
+
+    // The request is page-controlled. Anything this wallet does not act on is
+    // dropped before ethers sees it, so a field a future ethers learns to
+    // carry cannot be picked up out of it without this module knowing.
+    test("drops request fields this wallet does not act on", async () => {
+        const approved = await prepareApprovalTx(
+            providerWith(),
+            signer.address,
+            {
+                ...TX_PARAMS,
+                authorizationList: [{ address: RECIPIENT }],
+                blobVersionedHashes: ["0x01" + "ab".repeat(31)],
+                customData: { anything: true },
+            },
+        );
+        expect(approved.authorizationList).toBeUndefined();
+        expect(approved.blobVersionedHashes).toBeUndefined();
+        expect(approved.customData).toBeUndefined();
+        expect(approved.type).toBe(2);
+    });
+
+    test("refuses a transaction type this wallet does not sign", async () => {
+        await expect(
+            prepareApprovalTx(providerWith(), signer.address, {
+                ...TX_PARAMS,
+                type: 4,
+            }),
+        ).rejects.toThrow(/type this wallet does not sign/);
+    });
+
+    test("refuses to raise an approval with no active address", async () => {
+        await expect(
+            prepareApprovalTx(providerWith(), null, TX_PARAMS),
+        ).rejects.toThrow(/no active address/);
+    });
+
+    // The ceilings as a backstop: equality with the screen cannot bound what
+    // the node talks the wallet into putting on the screen, so it is refused
+    // before the user is shown anything.
+    test("refuses a fee the node quoted above the ceiling", async () => {
+        const gouging = providerWith({
+            getFeeData: async () => ({
+                gasPrice: MAX_FEE_PER_GAS + 1n,
+                maxFeePerGas: MAX_FEE_PER_GAS + 1n,
+                maxPriorityFeePerGas: 1000000000n,
+            }),
+        });
+        await expect(
+            prepareApprovalTx(gouging, signer.address, TX_PARAMS),
+        ).rejects.toThrow(/fee per gas far above any plausible value/);
+    });
+
+    test("refuses a gas limit the node estimated above the ceiling", async () => {
+        const absurd = providerWith({
+            estimateGas: async () => MAX_GAS_LIMIT + 1n,
+        });
+        await expect(
+            prepareApprovalTx(absurd, signer.address, TX_PARAMS),
+        ).rejects.toThrow(/gas limit no network this wallet supports/);
+    });
+
+    // No approval and no window: the failure goes back to the page the click
+    // came from, in a sentence.
+    test("reports a failed estimate as a full sentence", async () => {
+        const reverting = providerWith({
+            estimateGas: async () => {
+                throw new Error("execution reverted: ERC20: transfer amount");
+            },
+        });
+        let thrown;
+        try {
+            await prepareApprovalTx(reverting, signer.address, TX_PARAMS);
+        } catch (e) {
+            thrown = e;
+        }
+        expect(thrown.message).toMatch(
+            /^The transaction could not be prepared/,
+        );
+        expect(thrown.message).toMatch(/execution reverted/);
+        expect(thrown.message).toMatch(/^[A-Z].*\.$/);
+    });
+
+    // Without a bound, an unreachable node leaves the page's promise pending
+    // with nothing on screen to explain it.
+    test("gives up on a node that never answers", async () => {
+        jest.useFakeTimers();
+        try {
+            const hanging = providerWith({
+                estimateGas: () => new Promise(() => {}),
+            });
+            const pending = prepareApprovalTx(
+                hanging,
+                signer.address,
+                TX_PARAMS,
+            );
+            const settled = expect(pending).rejects.toThrow(
+                /did not answer in time/,
+            );
+            await jest.advanceTimersByTimeAsync(POPULATE_TIMEOUT_MS + 1);
+            await settled;
+        } finally {
+            jest.useRealTimers();
+        }
+    });
+});
+
+describe("serializeApprovedTx", () => {
+    // Unreachable through prepareApprovalTx while the request type is checked
+    // first, which is what it is for: a node or an ethers upgrade that
+    // populates a type this wallet does not sign must not produce an approval.
+    test("refuses a populated transaction of a type this wallet does not sign", () => {
+        expect(() =>
+            serializeApprovedTx(
+                { type: 3, to: RECIPIENT, nonce: 7 },
+                signer.address,
+            ),
+        ).toThrow(/type this wallet does not sign/);
+    });
+
+    test("refuses a populated transaction missing a quantity", () => {
+        expect(() =>
+            serializeApprovedTx(
+                {
+                    type: 2,
+                    chainId: 1n,
+                    nonce: 7,
+                    gasLimit: 21000n,
+                    maxFeePerGas: 2000000000n,
+                    to: RECIPIENT,
+                    value: 0n,
+                    data: "0x",
+                },
+                signer.address,
+            ),
+        ).toThrow(/did not supply a maxPriorityFeePerGas/);
+    });
+
+    test("keeps a contract creation's absent recipient absent", () => {
+        const approved = serializeApprovedTx(
+            {
+                type: 0,
+                chainId: 1n,
+                nonce: 7,
+                gasPrice: 2000000000n,
+                gasLimit: 21000n,
+                to: null,
+                value: 0n,
+                data: "0x600160005500",
+            },
+            signer.address,
+        );
+        expect(approved.to).toBeNull();
+        expect(approved.value).toBe("0x0");
+        expect(approved.data).toBe("0x600160005500");
+    });
+});

tests/approvalVerify.test.js

@@ -11,6 +11,7 @@ const {
     assertNoForbiddenFields,
     assertNothingUnchecked,
     assertCanonicalBytes,
+    assertWithinCeilings,
     sameAddress,
     failureIsRetryable,
     describeTxFailure,
@@ -18,12 +19,14 @@ const {
     ALLOWED_TX_TYPES,
     SERIALIZED_FIELDS,
     FORBIDDEN_FIELDS,
+    APPROVED_FIELDS,
     TX_STAGE_SIGN,
     TX_STAGE_VERIFY,
     TX_STAGE_BROADCAST,
     MAX_GAS_LIMIT,
     MAX_FEE_PER_GAS,
 } = require("../src/shared/approvalVerify");
+const { prepareApprovalTx } = require("../src/shared/approvalTx");
 const { getSignerForAddress } = require("../src/shared/wallet");
 
 // Fixed test keys — never used for anything but these tests.
@@ -42,7 +45,10 @@ const OTHER_RECIPIENT = "0xdAC17F958D2ee523a2206206994597C13D831ec7";
 const SELECTED = "0x1";
 const SEPOLIA = "0xaa36a7";
 
-// Approved parameters as a dApp would supply them over eth_sendTransaction.
+// Parameters as a dApp would supply them over eth_sendTransaction. Note what
+// is missing: nonce, gas limit and fees. The background fills those in before
+// the approval screen is drawn, which is why the approval below and not this
+// object is what every comparison runs against.
 const TX_PARAMS = {
     from: signer.address,
     to: RECIPIENT,
@@ -61,8 +67,8 @@ const POPULATED = {
     type: 2,
 };
 
-// Build a signable transaction from approved params. The popup does the same
+// Build a signable transaction from a request. The background populates the
-// thing through populateTransaction(); here the fields are fixed so the test
+// same fields through populateTransaction(); here they are fixed so the test
 // needs no provider. `overrides` stands in for what a tampered or misbuilt
 // popup would put on the wire.
 function txFor(params, overrides) {
@@ -75,6 +81,21 @@ function txFor(params, overrides) {
     };
 }
 
+// The populated transaction the approval screen displayed, which is the object
+// the artifact is verified against. Built from the same fields as the signable
+// transaction above, because that is the point: displayed and verified are one
+// object.
+function approvedFor(params, overrides) {
+    return {
+        from: signer.address,
+        accessList: [],
+        ...txFor(params, overrides),
+    };
+}
+
+// The ordinary case: the dApp's request, populated.
+const APPROVED = approvedFor(TX_PARAMS);
+
 async function signedFor(params, withWallet, overrides) {
     return (withWallet || signer).signTransaction(txFor(params, overrides));
 }
@@ -108,7 +129,7 @@ describe("sameAddress", () => {
 describe("verifySignedTx", () => {
     test("accepts the approved transaction signed by the approved address", async () => {
         const raw = await signedFor(TX_PARAMS);
-        const parsed = verifySignedTx(raw, TX_PARAMS, signer.address, SELECTED);
+        const parsed = verifySignedTx(raw, APPROVED, signer.address, SELECTED);
         expect(parsed.from).toBe(signer.address);
         expect(parsed.hash).toBe(Transaction.from(raw).hash);
     });
@@ -117,23 +138,23 @@ describe("verifySignedTx", () => {
         const params = { to: undefined, value: "0x0", data: "0x600160005500" };
         const raw = await signedFor(params);
         expect(() =>
-            verifySignedTx(raw, params, signer.address, SELECTED),
+            verifySignedTx(raw, approvedFor(params), signer.address, SELECTED),
         ).not.toThrow();
     });
 
     test("accepts an absent value as zero", async () => {
-        const approved = { to: RECIPIENT, data: "0x" };
+        const params = { to: RECIPIENT, data: "0x" };
-        const raw = await signedFor(approved);
+        const raw = await signedFor(params);
         expect(() =>
-            verifySignedTx(raw, approved, signer.address, SELECTED),
+            verifySignedTx(raw, approvedFor(params), signer.address, SELECTED),
         ).not.toThrow();
     });
 
     test("accepts call data whose case differs from the approval", async () => {
-        const approved = { to: RECIPIENT, value: "0x0", data: "0xDEADBEEF" };
+        const params = { to: RECIPIENT, value: "0x0", data: "0xDEADBEEF" };
-        const raw = await signedFor(approved);
+        const raw = await signedFor(params);
         expect(() =>
-            verifySignedTx(raw, approved, signer.address, SELECTED),
+            verifySignedTx(raw, approvedFor(params), signer.address, SELECTED),
         ).not.toThrow();
     });
 
@@ -143,7 +164,7 @@ describe("verifySignedTx", () => {
             to: OTHER_RECIPIENT,
         });
         expect(() =>
-            verifySignedTx(raw, TX_PARAMS, signer.address, SELECTED),
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED),
         ).toThrow(/approved recipient/);
     });
 
@@ -153,47 +174,64 @@ describe("verifySignedTx", () => {
             value: "0x4563918244f40000",
         });
         expect(() =>
-            verifySignedTx(raw, TX_PARAMS, signer.address, SELECTED),
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED),
         ).toThrow(/approved value/);
     });
 
     test("rejects substituted call data", async () => {
         const raw = await signedFor({ ...TX_PARAMS, data: "0xc0ffee" });
         expect(() =>
-            verifySignedTx(raw, TX_PARAMS, signer.address, SELECTED),
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED),
         ).toThrow(/approved call data/);
     });
 
     test("rejects a transaction signed by a different address", async () => {
         const raw = await signedFor(TX_PARAMS, other);
         expect(() =>
-            verifySignedTx(raw, TX_PARAMS, signer.address, SELECTED),
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED),
         ).toThrow(/different address/);
     });
 
+    // The address the approval named, not whichever address is active when the
+    // artifact comes back: an approval raised for one account cannot be
+    // satisfied by a signature from another, whatever the wallet switched to
+    // in between.
+    test("rejects a signature from the address that is active now", async () => {
+        const raw = await signedFor(TX_PARAMS, other);
+        expect(() =>
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED),
+        ).toThrow(/different address than the one that was approved/);
+        // The same artifact against the same approval, verified for the other
+        // address, is what would have happened had expectedFrom been read from
+        // the wallet's current state.
+        expect(() =>
+            verifySignedTx(raw, APPROVED, other.address, SELECTED),
+        ).not.toThrow();
+    });
+
     test("rejects an unsigned transaction", () => {
         const unsigned = Transaction.from(txFor(TX_PARAMS)).unsignedSerialized;
         expect(() =>
-            verifySignedTx(unsigned, TX_PARAMS, signer.address, SELECTED),
+            verifySignedTx(unsigned, APPROVED, signer.address, SELECTED),
         ).toThrow(/no valid signature/);
     });
 
     test("rejects a missing or malformed payload", () => {
         expect(() =>
-            verifySignedTx(undefined, TX_PARAMS, signer.address, SELECTED),
+            verifySignedTx(undefined, APPROVED, signer.address, SELECTED),
         ).toThrow(/missing or malformed/);
         expect(() =>
-            verifySignedTx("nope", TX_PARAMS, signer.address, SELECTED),
+            verifySignedTx("nope", APPROVED, signer.address, SELECTED),
         ).toThrow(/missing or malformed/);
         expect(() =>
-            verifySignedTx("0xc0ffee", TX_PARAMS, signer.address, SELECTED),
+            verifySignedTx("0xc0ffee", APPROVED, signer.address, SELECTED),
         ).toThrow(/could not be decoded/);
     });
 
     test("every rejection message is a full sentence", async () => {
         const raw = await signedFor({ ...TX_PARAMS, to: OTHER_RECIPIENT });
         try {
-            verifySignedTx(raw, TX_PARAMS, signer.address, SELECTED);
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED);
             throw new Error("expected a rejection");
         } catch (e) {
             expect(e.message).toMatch(/^[A-Z].*\.$/);
@@ -201,20 +239,113 @@ describe("verifySignedTx", () => {
     });
 });
 
+// The defect this file's approvals now stand against: for every field the dApp
+// left out, the old comparison had nothing to compare and skipped the field,
+// so the fee and the nonce the user read off the screen were checked by the
+// ceilings alone. A populated approval fixes all of them, and an approval that
+// does not fix one is a refusal rather than a pass.
+describe("verifySignedTx against what was displayed", () => {
+    test("a fee differing from the displayed one is refused", async () => {
+        // Ten times the fee the screen showed, and far below the ceiling: the
+        // artifact the old comparison would have accepted.
+        const inflated = 20000000000n;
+        expect(inflated).toBeLessThan(MAX_FEE_PER_GAS);
+        const raw = await signedWith({ maxFeePerGas: inflated });
+        expect(() =>
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED),
+        ).toThrow(/approved maximum fee per gas/);
+    });
+
+    test("a nonce differing from the displayed one is refused", async () => {
+        const raw = await signedWith({ nonce: 8 });
+        expect(() =>
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED),
+        ).toThrow(/approved nonce/);
+    });
+
+    test("a gas limit differing from the displayed one is refused", async () => {
+        const raw = await signedWith({ gasLimit: 250000n });
+        expect(() =>
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED),
+        ).toThrow(/approved gas limit/);
+    });
+
+    test("an approval fixing no quantity is refused, not waved through", async () => {
+        const raw = await signedWith({});
+        for (const key of [
+            "chainId",
+            "nonce",
+            "gasLimit",
+            "maxFeePerGas",
+            "maxPriorityFeePerGas",
+        ]) {
+            const incomplete = { ...APPROVED };
+            delete incomplete[key];
+            let thrown;
+            try {
+                verifySignedTx(raw, incomplete, signer.address, SELECTED);
+                throw new Error("expected a rejection for " + key);
+            } catch (e) {
+                thrown = e;
+            }
+            expect(thrown.message).toMatch(/fixes no /);
+            expect(thrown.approvalMismatch).toBe(true);
+        }
+    });
+
+    test("no approved transaction at all is refused", async () => {
+        const raw = await signedWith({});
+        for (const approved of [undefined, null, "0xdeadbeef"]) {
+            expect(() =>
+                verifySignedTx(raw, approved, signer.address, SELECTED),
+            ).toThrow(/no approved transaction/);
+        }
+    });
+
+    test("an approval fixing no transaction type is refused", async () => {
+        const raw = await signedWith({});
+        const incomplete = { ...APPROVED };
+        delete incomplete.type;
+        expect(() =>
+            verifySignedTx(raw, incomplete, signer.address, SELECTED),
+        ).toThrow(/fixes no transaction type/);
+    });
+
+    test("an artifact of a type other than the approved one is refused", async () => {
+        // Same fee mechanism on both sides, so only the type differs: a type 1
+        // artifact against a type 2 approval.
+        const approved = approvedFor(TX_PARAMS, {
+            type: 1,
+            gasPrice: 2000000000n,
+            maxFeePerGas: null,
+            maxPriorityFeePerGas: null,
+        });
+        const raw = await signedWith({
+            type: 0,
+            gasPrice: 2000000000n,
+            maxFeePerGas: null,
+            maxPriorityFeePerGas: null,
+        });
+        expect(() =>
+            verifySignedTx(raw, approved, signer.address, SELECTED),
+        ).toThrow(/approved transaction type/);
+    });
+});
+
 // One case per consequential field: the field alone differs from what was
 // approved, and that alone must refuse the signature.
 describe("verifySignedTx field comparison", () => {
     test("rejects a chain id that is not the selected network", async () => {
         const raw = await signedWith({ chainId: 11155111 });
         expect(() =>
-            verifySignedTx(raw, TX_PARAMS, signer.address, SELECTED),
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED),
         ).toThrow(/different network than the one that is selected/);
     });
 
     test("rejects a chain id that is not the approved one", async () => {
-        // Selected network and signed chain id agree; the dApp asked for a
+        // Selected network and signed chain id agree; the approval was raised
-        // different chain, so the artifact is not what was approved.
+        // for a different chain, so the artifact is not what was approved.
-        const approved = { ...TX_PARAMS, chainId: SEPOLIA };
+        const approved = { ...APPROVED, chainId: SEPOLIA };
         const raw = await signedWith({});
         expect(() =>
             verifySignedTx(raw, approved, signer.address, SELECTED),
@@ -224,58 +355,59 @@ describe("verifySignedTx field comparison", () => {
     test("refuses when the selected network is unknown", async () => {
         const raw = await signedWith({});
         expect(() =>
-            verifySignedTx(raw, TX_PARAMS, signer.address, undefined),
+            verifySignedTx(raw, APPROVED, signer.address, undefined),
         ).toThrow(/selected network is unknown/);
     });
 
     test("rejects a substituted nonce", async () => {
-        const approved = { ...TX_PARAMS, nonce: 7 };
         const raw = await signedWith({ nonce: 8 });
         expect(() =>
-            verifySignedTx(raw, approved, signer.address, SELECTED),
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED),
         ).toThrow(/approved nonce/);
     });
 
     test("rejects a substituted gas limit", async () => {
-        const approved = { ...TX_PARAMS, gasLimit: "0x186a0" };
         const raw = await signedWith({ gasLimit: 250000n });
         expect(() =>
-            verifySignedTx(raw, approved, signer.address, SELECTED),
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED),
         ).toThrow(/approved gas limit/);
     });
 
     test("rejects a substituted maximum fee per gas", async () => {
-        const approved = { ...TX_PARAMS, maxFeePerGas: "0x77359400" };
         const raw = await signedWith({ maxFeePerGas: 900000000000n });
         expect(() =>
-            verifySignedTx(raw, approved, signer.address, SELECTED),
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED),
         ).toThrow(/approved maximum fee per gas/);
     });
 
     test("rejects a substituted maximum priority fee per gas", async () => {
-        const approved = { ...TX_PARAMS, maxPriorityFeePerGas: "0x3b9aca00" };
         const raw = await signedWith({ maxPriorityFeePerGas: 1500000000n });
         expect(() =>
-            verifySignedTx(raw, approved, signer.address, SELECTED),
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED),
         ).toThrow(/approved maximum priority fee per gas/);
     });
 
     test("rejects a substituted legacy gas price", async () => {
-        const approved = { ...TX_PARAMS, gasPrice: "0x77359400" };
         const legacy = {
             type: 0,
-            gasPrice: 9000000000n,
+            gasPrice: 2000000000n,
             maxFeePerGas: null,
             maxPriorityFeePerGas: null,
         };
-        const raw = await signedWith(legacy);
+        const approved = approvedFor(TX_PARAMS, legacy);
+        const raw = await signedWith({ ...legacy, gasPrice: 9000000000n });
         expect(() =>
             verifySignedTx(raw, approved, signer.address, SELECTED),
         ).toThrow(/approved gas price/);
     });
 
     test("rejects an approved legacy fee signed as an EIP-1559 fee", async () => {
-        const approved = { ...TX_PARAMS, gasPrice: "0x77359400" };
+        const approved = approvedFor(TX_PARAMS, {
+            type: 0,
+            gasPrice: 2000000000n,
+            maxFeePerGas: null,
+            maxPriorityFeePerGas: null,
+        });
         const raw = await signedWith({});
         expect(() =>
             verifySignedTx(raw, approved, signer.address, SELECTED),
@@ -283,7 +415,6 @@ describe("verifySignedTx field comparison", () => {
     });
 
     test("rejects an approved EIP-1559 fee signed as a legacy fee", async () => {
-        const approved = { ...TX_PARAMS, maxFeePerGas: "0x77359400" };
         const raw = await signedWith({
             type: 0,
             gasPrice: 2000000000n,
@@ -291,36 +422,72 @@ describe("verifySignedTx field comparison", () => {
             maxPriorityFeePerGas: null,
         });
         expect(() =>
-            verifySignedTx(raw, approved, signer.address, SELECTED),
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED),
         ).toThrow(/approved fee mechanism/);
     });
 
+    // The ceilings are a backstop against what the RPC node can talk the
+    // wallet into populating and displaying, so they are checked against an
+    // approval that carries the absurd value too — equality alone would accept
+    // it, which is exactly what the ceiling is there for.
     test("rejects a gas limit above anything a supported network accepts", async () => {
-        const raw = await signedWith({ gasLimit: MAX_GAS_LIMIT + 1n });
+        const overrides = { gasLimit: MAX_GAS_LIMIT + 1n };
+        const raw = await signedWith(overrides);
         expect(() =>
-            verifySignedTx(raw, TX_PARAMS, signer.address, SELECTED),
+            verifySignedTx(
+                raw,
+                approvedFor(TX_PARAMS, overrides),
+                signer.address,
+                SELECTED,
+            ),
         ).toThrow(/gas limit no network this wallet supports/);
     });
 
-    test("rejects an absurd fee per gas the approval never fixed", async () => {
+    test("rejects an absurd fee per gas even when it was displayed", async () => {
-        const raw = await signedWith({
+        const overrides = {
             maxFeePerGas: MAX_FEE_PER_GAS + 1n,
             maxPriorityFeePerGas: MAX_FEE_PER_GAS + 1n,
-        });
+        };
+        const raw = await signedWith(overrides);
         expect(() =>
-            verifySignedTx(raw, TX_PARAMS, signer.address, SELECTED),
+            verifySignedTx(
+                raw,
+                approvedFor(TX_PARAMS, overrides),
+                signer.address,
+                SELECTED,
+            ),
         ).toThrow(/fee per gas far above any plausible value/);
     });
 
+    test("assertWithinCeilings is the same check on either side of the screen", () => {
+        expect(() =>
+            assertWithinCeilings({ gasLimit: MAX_GAS_LIMIT + 1n }),
+        ).toThrow(/gas limit no network this wallet supports/);
+        for (const key of [
+            "gasPrice",
+            "maxFeePerGas",
+            "maxPriorityFeePerGas",
+        ]) {
+            expect(() =>
+                assertWithinCeilings({ [key]: MAX_FEE_PER_GAS + 1n }),
+            ).toThrow(/fee per gas far above any plausible value/);
+        }
+        expect(() =>
+            assertWithinCeilings({
+                gasLimit: MAX_GAS_LIMIT,
+                maxFeePerGas: MAX_FEE_PER_GAS,
+                maxPriorityFeePerGas: MAX_FEE_PER_GAS,
+            }),
+        ).not.toThrow();
+        // Nothing to bound is not a failure: a type 2 approval carries no gas
+        // price, and a bare object must not be refused for lacking one.
+        expect(() => assertWithinCeilings({})).not.toThrow();
+    });
+
     test("every field mismatch is a refusal, not a warning", async () => {
         const raw = await signedWith({ nonce: 8 });
         try {
-            verifySignedTx(
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED);
-                raw,
-                { ...TX_PARAMS, nonce: 7 },
-                signer.address,
-                SELECTED,
-            );
             throw new Error("expected a rejection");
         } catch (e) {
             expect(e.approvalMismatch).toBe(true);
@@ -331,17 +498,17 @@ describe("verifySignedTx field comparison", () => {
 
 // The transaction type decides which fields exist, so an artifact of a type
 // this wallet does not sign carries consequences the approval cannot describe
-// and none of the field comparisons can see. The approval used here is the
+// and none of the field comparisons can see. The refusal has to come from the
-// ordinary dApp shape with no fee fields — the common case, since
+// type allowlist rather than from a field comparison, so these run against an
-// populateTransaction() fills them — which is exactly the case the
+// approval whose every other field matches the artifact exactly.
-// fee-mechanism check cannot catch by accident.
 describe("verifySignedTx transaction type", () => {
-    const BARE_APPROVAL = {
+    const BARE_REQUEST = {
         from: signer.address,
         to: RECIPIENT,
         value: "0x2386f26fc10000",
         data: "0x",
     };
+    const BARE_APPROVAL = approvedFor(BARE_REQUEST);
 
     // An EIP-7702 artifact that pays the approved amount to the approved
     // recipient and, in the same transaction, installs the attacker's code at
@@ -353,7 +520,7 @@ describe("verifySignedTx transaction type", () => {
             chainId: 1,
             nonce: 8,
         });
-        const raw = await signedFor(BARE_APPROVAL, signer, {
+        const raw = await signedFor(BARE_REQUEST, signer, {
             type: 4,
             authorizationList: [authorization],
         });
@@ -366,7 +533,7 @@ describe("verifySignedTx transaction type", () => {
     });
 
     test("refuses a type 3 blob artifact", async () => {
-        const raw = await signedFor(BARE_APPROVAL, signer, {
+        const raw = await signedFor(BARE_REQUEST, signer, {
             type: 3,
             maxFeePerBlobGas: 1000000000n,
             blobVersionedHashes: ["0x01" + "ab".repeat(31)],
@@ -390,7 +557,7 @@ describe("verifySignedTx transaction type", () => {
             chainId: 1,
             nonce: 8,
         });
-        const raw = await signedFor(BARE_APPROVAL, signer, {
+        const raw = await signedFor(BARE_REQUEST, signer, {
             type: 4,
             authorizationList: [authorization],
         });
@@ -404,40 +571,45 @@ describe("verifySignedTx transaction type", () => {
     });
 
     test("accepts a legacy type 0 transaction", async () => {
-        const approved = { ...BARE_APPROVAL, gasPrice: "0x77359400" };
+        const legacy = {
-        const raw = await signedFor(approved, signer, {
             type: 0,
             gasPrice: 2000000000n,
             maxFeePerGas: null,
             maxPriorityFeePerGas: null,
-        });
+        };
+        const raw = await signedFor(BARE_REQUEST, signer, legacy);
         expect(() =>
-            verifySignedTx(raw, approved, signer.address, SELECTED),
+            verifySignedTx(
+                raw,
+                approvedFor(BARE_REQUEST, legacy),
+                signer.address,
+                SELECTED,
+            ),
         ).not.toThrow();
     });
 
     test("accepts a type 1 transaction whose access list is the approved one", async () => {
-        const accessList = [{ address: OTHER_RECIPIENT, storageKeys: [] }];
+        const overrides = {
-        const approved = {
-            ...BARE_APPROVAL,
-            gasPrice: "0x77359400",
-            accessList,
-        };
-        const raw = await signedFor(approved, signer, {
             type: 1,
             gasPrice: 2000000000n,
             maxFeePerGas: null,
             maxPriorityFeePerGas: null,
-            accessList,
+            accessList: [{ address: OTHER_RECIPIENT, storageKeys: [] }],
-        });
+        };
+        const raw = await signedFor(BARE_REQUEST, signer, overrides);
         expect(Transaction.from(raw).type).toBe(1);
         expect(() =>
-            verifySignedTx(raw, approved, signer.address, SELECTED),
+            verifySignedTx(
+                raw,
+                approvedFor(BARE_REQUEST, overrides),
+                signer.address,
+                SELECTED,
+            ),
         ).not.toThrow();
     });
 
     test("refuses an access list the approval never carried", async () => {
-        const raw = await signedFor(BARE_APPROVAL, signer, {
+        const raw = await signedFor(BARE_REQUEST, signer, {
             accessList: [{ address: OTHER_RECIPIENT, storageKeys: [] }],
         });
         expect(() =>
@@ -446,8 +618,11 @@ describe("verifySignedTx transaction type", () => {
     });
 
     test("treats an absent access list and an empty one as the same thing", async () => {
-        const approved = { ...BARE_APPROVAL, accessList: [] };
+        const approved = { ...BARE_APPROVAL };
-        const raw = await signedFor(BARE_APPROVAL, signer, {});
+        delete approved.accessList;
+        expect(approved.accessList).toBeUndefined();
+        const raw = await signedFor(BARE_REQUEST, signer, {});
+        expect(Transaction.from(raw).accessList).toEqual([]);
         expect(() =>
             verifySignedTx(raw, approved, signer.address, SELECTED),
         ).not.toThrow();
@@ -498,6 +673,25 @@ describe("verifySignedTx exhaustiveness", () => {
         expect(exposed.filter((name) => !accounted.has(name))).toEqual([]);
     });
 
+    // The comparison loop runs over the fields a type serializes and refuses a
+    // field it has no comparator for. That refusal is unreachable only while
+    // the table covers the whole of SERIALIZED_FIELDS, so the coverage is
+    // pinned here rather than assumed: adding a field to a type without a
+    // comparator would otherwise turn every transaction of that type into a
+    // refusal, and adding a comparator without the field would be a check that
+    // never runs.
+    test("every field a type serializes has a comparator", () => {
+        const serialized = new Set(
+            Object.values(SERIALIZED_FIELDS).flat().sort(),
+        );
+        expect([...serialized].filter((key) => !APPROVED_FIELDS[key])).toEqual(
+            [],
+        );
+        expect(
+            Object.keys(APPROVED_FIELDS).filter((key) => !serialized.has(key)),
+        ).toEqual([]);
+    });
+
     // The two layers behind the type allowlist. Nothing reachable through
     // verifySignedTx can trip either of them while the allowlist holds — that
     // is what they are for — so they are exercised directly rather than taken
@@ -553,26 +747,12 @@ describe("verifySignedTx exhaustiveness", () => {
     test("an accepted artifact of each allowed type rebuilds byte for byte", async () => {
         const shapes = [
             {
-                approved: { ...TX_PARAMS, gasPrice: "0x77359400" },
-                overrides: {
                 type: 0,
                 gasPrice: 2000000000n,
                 maxFeePerGas: null,
                 maxPriorityFeePerGas: null,
             },
-            },
             {
-                approved: {
-                    ...TX_PARAMS,
-                    gasPrice: "0x77359400",
-                    accessList: [
-                        {
-                            address: RECIPIENT,
-                            storageKeys: ["0x" + "11".repeat(32)],
-                        },
-                    ],
-                },
-                overrides: {
                 type: 1,
                 gasPrice: 2000000000n,
                 maxFeePerGas: null,
@@ -584,18 +764,13 @@ describe("verifySignedTx exhaustiveness", () => {
                     },
                 ],
             },
-            },
+            {},
-            { approved: TX_PARAMS, overrides: {} },
         ];
-        for (const shape of shapes) {
+        for (const overrides of shapes) {
-            const raw = await signedFor(
+            const raw = await signedFor(TX_PARAMS, signer, overrides);
-                shape.approved,
-                signer,
-                shape.overrides,
-            );
             const parsed = verifySignedTx(
                 raw,
-                shape.approved,
+                approvedFor(TX_PARAMS, overrides),
                 signer.address,
                 SELECTED,
             );
@@ -644,7 +819,7 @@ describe("verifySignedTx canonical encoding", () => {
     test("refuses an artifact that is not its own canonical encoding", async () => {
         const mutated = await nonCanonical();
         expect(() =>
-            verifySignedTx(mutated, TX_PARAMS, signer.address, SELECTED),
+            verifySignedTx(mutated, APPROVED, signer.address, SELECTED),
         ).toThrow(/not encoded canonically/);
     });
 
@@ -659,7 +834,7 @@ describe("verifySignedTx canonical encoding", () => {
         const raw = await signedWith({});
         const upper = "0x" + raw.slice(2).toUpperCase();
         expect(() =>
-            verifySignedTx(upper, TX_PARAMS, signer.address, SELECTED),
+            verifySignedTx(upper, APPROVED, signer.address, SELECTED),
         ).not.toThrow();
     });
 });
@@ -670,46 +845,33 @@ describe("verifySignedTx normalization", () => {
     test("accepts a decimal chain id against a hex selected network", async () => {
         const raw = await signedWith({});
         expect(() =>
-            verifySignedTx(raw, TX_PARAMS, signer.address, 1),
+            verifySignedTx(raw, APPROVED, signer.address, 1),
         ).not.toThrow();
         expect(() =>
-            verifySignedTx(raw, TX_PARAMS, signer.address, "1"),
+            verifySignedTx(raw, APPROVED, signer.address, "1"),
         ).not.toThrow();
     });
 
-    test("accepts an approved chain id written in hex", async () => {
+    // The approved transaction crosses to the popup as JSON, so it comes back
+    // spelled in hex quantities rather than in the bigints it was populated
+    // with. None of that is tampering.
+    test("accepts an approval spelled as the wire spells it", async () => {
         const raw = await signedWith({});
-        const approved = { ...TX_PARAMS, chainId: "0x1" };
+        const wire = {
+            ...APPROVED,
+            chainId: "0x1",
+            nonce: "0x7",
+            gasLimit: "0x186a0",
+            maxFeePerGas: "0x77359400",
+            maxPriorityFeePerGas: "0x3b9aca00",
+            value: "0x2386f26fc10000",
+        };
         expect(() =>
-            verifySignedTx(raw, approved, signer.address, SELECTED),
+            verifySignedTx(raw, wire, signer.address, SELECTED),
         ).not.toThrow();
     });
 
-    test("accepts a hex nonce against a numeric one", async () => {
+    test("accepts quantities spelled as hex, decimal, number and bigint", async () => {
-        const raw = await signedWith({ nonce: 7 });
-        expect(() =>
-            verifySignedTx(
-                raw,
-                { ...TX_PARAMS, nonce: "0x7" },
-                signer.address,
-                SELECTED,
-            ),
-        ).not.toThrow();
-    });
-
-    test("accepts a decimal gas limit against a hex one", async () => {
-        const raw = await signedWith({ gasLimit: 100000n });
-        expect(() =>
-            verifySignedTx(
-                raw,
-                { ...TX_PARAMS, gasLimit: "100000" },
-                signer.address,
-                SELECTED,
-            ),
-        ).not.toThrow();
-    });
-
-    test("accepts fee fields spelled as hex, decimal, number and bigint", async () => {
         const raw = await signedWith({});
         for (const maxFee of [
             "0x77359400",
@@ -720,7 +882,7 @@ describe("verifySignedTx normalization", () => {
             expect(() =>
                 verifySignedTx(
                     raw,
-                    { ...TX_PARAMS, maxFeePerGas: maxFee },
+                    { ...APPROVED, maxFeePerGas: maxFee },
                     signer.address,
                     SELECTED,
                 ),
@@ -728,24 +890,19 @@ describe("verifySignedTx normalization", () => {
         }
     });
 
-    test("accepts an approval that fixes no nonce, gas or fee at all", async () => {
-        const raw = await signedWith({});
-        expect(() =>
-            verifySignedTx(raw, TX_PARAMS, signer.address, SELECTED),
-        ).not.toThrow();
-    });
-
     test("accepts an approval whose recipient case differs", async () => {
         const raw = await signedWith({});
-        const approved = { ...TX_PARAMS, to: RECIPIENT.toLowerCase() };
+        const approved = { ...APPROVED, to: RECIPIENT.toLowerCase() };
         expect(() =>
             verifySignedTx(raw, approved, signer.address, SELECTED),
         ).not.toThrow();
     });
 
     test("accepts absent call data against 0x", async () => {
-        const approved = { to: RECIPIENT, value: "0x0" };
+        const params = { to: RECIPIENT, value: "0x0" };
-        const raw = await signedFor({ ...approved, data: "0x" });
+        const approved = approvedFor(params);
+        delete approved.data;
+        const raw = await signedFor({ ...params, data: "0x" });
         expect(() =>
             verifySignedTx(raw, approved, signer.address, SELECTED),
         ).not.toThrow();
@@ -756,7 +913,7 @@ describe("verifySignedTx normalization", () => {
         expect(() =>
             verifySignedTx(
                 raw,
-                { ...TX_PARAMS, maxFeePerGas: "cheap" },
+                { ...APPROVED, maxFeePerGas: "cheap" },
                 signer.address,
                 SELECTED,
             ),
@@ -774,7 +931,7 @@ describe("verifySignedTx normalization", () => {
             try {
                 verifySignedTx(
                     raw,
-                    { ...TX_PARAMS, value },
+                    { ...APPROVED, value },
                     signer.address,
                     SELECTED,
                 );
@@ -793,7 +950,7 @@ describe("verifySignedTx normalization", () => {
         expect(() =>
             verifySignedTx(
                 raw,
-                { ...TX_PARAMS, accessList: ["nope"] },
+                { ...APPROVED, accessList: ["nope"] },
                 signer.address,
                 SELECTED,
             ),
@@ -934,7 +1091,7 @@ describe("signing failure and retry", () => {
     test("a mismatch spends the approval", async () => {
         const raw = await signedFor({ ...TX_PARAMS, to: OTHER_RECIPIENT });
         try {
-            verifySignedTx(raw, TX_PARAMS, signer.address, SELECTED);
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED);
             throw new Error("expected a rejection");
         } catch (e) {
             expect(failureIsRetryable(e)).toBe(false);
@@ -1007,7 +1164,7 @@ describe("signing failure and retry", () => {
         const raw = await signedFor({ ...TX_PARAMS, to: OTHER_RECIPIENT });
         let outcome;
         try {
-            verifySignedTx(raw, TX_PARAMS, signer.address, SELECTED);
+            verifySignedTx(raw, APPROVED, signer.address, SELECTED);
         } catch (e) {
             outcome = describeTxFailure(TX_STAGE_VERIFY, e);
         }
@@ -1061,12 +1218,13 @@ describe("signing failure and retry", () => {
     });
 });
 
-// End-to-end over the messaging boundary, without a browser: run the exact
+// End-to-end over the messaging boundary, without a browser: the background
-// sequence the approval popup runs, then hand the artifact to the exact check
+// populates the transaction, the object that produces crosses to the popup as
-// the background runs before it broadcasts or resolves. Only what the popup
+// JSON and is signed there, and the artifact goes back to the exact check the
-// puts on the wire is passed along, so this also pins down that the wire
+// background runs before it broadcasts. Only what each side puts on the wire is
-// payload is sufficient on its own.
+// passed along, so this also pins down that the wire payloads are sufficient on
-describe("popup signing sequence to background verification", () => {
+// their own.
+describe("background population to popup signing to verification", () => {
     // Stand-in for the JSON-RPC provider. populateTransaction only needs the
     // nonce, the gas estimate, the network and the fee data.
     const fakeProvider = {
@@ -1084,33 +1242,52 @@ describe("popup signing sequence to background verification", () => {
     // through getSignerForAddress() the way the popup does.
     const walletData = { type: "privkey" };
 
-    async function popupSignsTx(txParams) {
+    // What the background does before the approval window opens.
-        const localSigner = getSignerForAddress(walletData, 0, SIGNER_KEY);
+    async function backgroundPrepares(txParams) {
-        const connected = localSigner.connect(fakeProvider);
+        const approvedTx = await prepareApprovalTx(
-        const populated = await connected.populateTransaction(txParams);
+            fakeProvider,
-        delete populated.from;
+            signer.address,
-        return connected.signTransaction(populated);
+            txParams,
+        );
+        // Extension messaging is JSON; the popup sees the other side of it.
+        return JSON.parse(JSON.stringify(approvedTx));
     }
 
-    test("a populated, signed transaction is accepted and broadcastable", async () => {
+    // What the popup does with it: signs it as given, populating nothing.
-        const rawSignedTx = await popupSignsTx(TX_PARAMS);
+    async function popupSigns(approvedTx) {
+        const localSigner = getSignerForAddress(walletData, 0, SIGNER_KEY);
+        return localSigner.signTransaction({ ...approvedTx });
+    }
+
+    test("the populated transaction is what gets signed and what gets checked", async () => {
+        const approvedTx = await backgroundPrepares(TX_PARAMS);
+        const rawSignedTx = await popupSigns(approvedTx);
         const parsed = verifySignedTx(
             rawSignedTx,
-            TX_PARAMS,
+            approvedTx,
             signer.address,
             SELECTED,
         );
         expect(parsed.nonce).toBe(7);
         expect(parsed.chainId).toBe(1n);
         expect(parsed.gasLimit).toBe(21000n);
+        expect(parsed.maxFeePerGas).toBe(2000000000n);
         expect(parsed.to).toBe(RECIPIENT);
         expect(parsed.value).toBe(BigInt(TX_PARAMS.value));
         expect(parsed.data).toBe(TX_PARAMS.data);
         expect(parsed.signature).not.toBeNull();
+        // Every field the screen shows, and the artifact, are the same numbers.
+        expect(BigInt(approvedTx.nonce)).toBe(BigInt(parsed.nonce));
+        expect(BigInt(approvedTx.gasLimit)).toBe(parsed.gasLimit);
+        expect(BigInt(approvedTx.maxFeePerGas)).toBe(parsed.maxFeePerGas);
+        expect(BigInt(approvedTx.maxPriorityFeePerGas)).toBe(
+            parsed.maxPriorityFeePerGas,
+        );
     });
 
     test("the wire payload carries no password and no secret", async () => {
-        const rawSignedTx = await popupSignsTx(TX_PARAMS);
+        const approvedTx = await backgroundPrepares(TX_PARAMS);
+        const rawSignedTx = await popupSigns(approvedTx);
         const payload = {
             type: "AUTISTMASK_TX_RESPONSE",
             id: "test-approval-id",
@@ -1128,20 +1305,54 @@ describe("popup signing sequence to background verification", () => {
         expect(wire).not.toContain(SIGNER_KEY.slice(2).toLowerCase());
     });
 
+    // The popup is the component whose compromise this check exists to detect,
+    // so it is given the approved transaction and signs something else.
+    test("a popup that signs a different fee than it was given is refused", async () => {
+        const approvedTx = await backgroundPrepares(TX_PARAMS);
+        const rawSignedTx = await popupSigns({
+            ...approvedTx,
+            maxFeePerGas: "0x3b9aca000",
+        });
+        expect(() =>
+            verifySignedTx(rawSignedTx, approvedTx, signer.address, SELECTED),
+        ).toThrow(/approved maximum fee per gas/);
+    });
+
+    test("a popup that signs a different nonce than it was given is refused", async () => {
+        const approvedTx = await backgroundPrepares(TX_PARAMS);
+        const rawSignedTx = await popupSigns({ ...approvedTx, nonce: "0x8" });
+        expect(() =>
+            verifySignedTx(rawSignedTx, approvedTx, signer.address, SELECTED),
+        ).toThrow(/approved nonce/);
+    });
+
     test("the background rejects a transaction the popup did not approve", async () => {
-        const rawSignedTx = await popupSignsTx({
+        const approvedTx = await backgroundPrepares(TX_PARAMS);
-            ...TX_PARAMS,
+        const rawSignedTx = await popupSigns({
+            ...approvedTx,
             to: OTHER_RECIPIENT,
         });
         expect(() =>
-            verifySignedTx(rawSignedTx, TX_PARAMS, signer.address, SELECTED),
+            verifySignedTx(rawSignedTx, approvedTx, signer.address, SELECTED),
         ).toThrow(/approved recipient/);
     });
 
     test("the background rejects a transaction populated on another network", async () => {
-        const rawSignedTx = await popupSignsTx(TX_PARAMS);
+        const approvedTx = await backgroundPrepares(TX_PARAMS);
+        const rawSignedTx = await popupSigns(approvedTx);
         expect(() =>
-            verifySignedTx(rawSignedTx, TX_PARAMS, signer.address, SEPOLIA),
+            verifySignedTx(rawSignedTx, approvedTx, signer.address, SEPOLIA),
         ).toThrow(/different network than the one that is selected/);
     });
+
+    // ethers refuses to sign for an address that is not the key's own, so a
+    // popup working from the approved object cannot quietly sign as whichever
+    // address the user has switched to.
+    test("the approved from stops the popup signing with another key", async () => {
+        const approvedTx = await backgroundPrepares(TX_PARAMS);
+        const otherSigner = getSignerForAddress(walletData, 0, OTHER_KEY);
+        await expect(
+            otherSigner.signTransaction({ ...approvedTx }),
+        ).rejects.toThrow(/from address mismatch/);
+    });
 });

tests/backgroundApproval.test.js

@@ -8,16 +8,24 @@
 // already saw — which means the entry being present is not by itself proof
 // that no attempt is running. A second response carrying the same id (a
 // reloaded approval window re-rendering a live Approve button, a popup that
-// emits the message twice) must not start a second verify and broadcast: with
+// emits the message twice) must not start a second verify and broadcast: the
-// the ordinary dApp approval shape the page fixes no nonce, so two artifacts
+// same approved transaction signed twice verifies twice, and the transfer
-// signed at different nonces both verify, and the approved transfer would go
+// would go out twice.
-// out twice.
+//
+// It also covers what the approval is verified against. The approval now
+// carries the transaction the background populated and the screen displayed,
+// and the address that was active when it was raised — so a fee, a nonce or an
+// address that moved between approval and signing is refused rather than
+// signed.
 
-const { Wallet } = require("ethers");
+const { Network, Wallet } = require("ethers");
 
 const SIGNER_KEY =
     "0x59c6995e998f97a5a0044966f0945389dc9e86dae88c7a8412f4603b6b78690d";
+const OTHER_KEY =
+    "0x5de4111afa1a4b94908f83103eb1f1706367c2e68ca870fc3fb9a804cdab365a";
 const signer = new Wallet(SIGNER_KEY);
+const other = new Wallet(OTHER_KEY);
 const RECIPIENT = "0x66133E8ea0f5D1d612D2502a968757D1048c214a";
 
 const ORIGIN = "https://dapp.example";
@@ -33,9 +41,16 @@ const TX_PARAMS = {
     data: "0x",
 };
 
-// The fields the popup's populateTransaction() would fill in. The nonce is a
+// The nonce the stubbed node reports, and so the nonce the background
-// parameter because the duplicate case turns on the two artifacts differing
+// populates the approval with.
-// in exactly the field nothing constrains.
+const NONCE = 7;
+
+// "Hello AutistMask" as the hex string a dApp passes to personal_sign.
+const MESSAGE = "0x48656c6c6f204175746973744d61736b";
+
+// The transaction the background populates and the approval screen displays.
+// The nonce is a parameter because the duplicate case turns on two artifacts
+// differing in a field the dApp fixed nothing for.
 function populated(nonce) {
     return {
         type: 2,
@@ -50,8 +65,26 @@ function populated(nonce) {
     };
 }
 
-function signedAtNonce(nonce) {
+function signedAtNonce(nonce, withWallet) {
-    return signer.signTransaction(populated(nonce));
+    return (withWallet || signer).signTransaction(populated(nonce));
+}
+
+// The node the background populates against. Its answers are the numbers the
+// approval screen shows, so they are also the numbers every artifact below is
+// signed at.
+function fakeProvider(broadcastTransaction, overrides) {
+    return {
+        broadcastTransaction,
+        getNetwork: async () => Network.from(1),
+        getTransactionCount: async () => NONCE,
+        estimateGas: async () => 100000n,
+        getFeeData: async () => ({
+            gasPrice: 2000000000n,
+            maxFeePerGas: 2000000000n,
+            maxPriorityFeePerGas: 1000000000n,
+        }),
+        ...(overrides || {}),
+    };
 }
 
 // A promise whose settlement the test controls, so a broadcast can be held in
@@ -85,7 +118,7 @@ function loadBackground(options) {
         currentNetwork: () => ({ chainId: "0x1" }),
     }));
     jest.doMock("../src/shared/balances", () => ({
-        getProvider: () => ({ broadcastTransaction }),
+        getProvider: () => fakeProvider(broadcastTransaction, opts.provider),
         refreshBalances: jest.fn(async () => {}),
     }));
     jest.doMock("../src/shared/phishingDomains", () => ({
@@ -171,7 +204,7 @@ function loadBackground(options) {
 
     // Raise a pending transaction approval the way a dApp does, and dig the
     // approval id back out of the popup URL the background opened.
-    function requestTx() {
+    function requestTx(txParams) {
         let rpcResult = null;
         const sendResponse = jest.fn((r) => {
             rpcResult = r;
@@ -180,7 +213,7 @@ function loadBackground(options) {
             {
                 type: "AUTISTMASK_RPC",
                 method: "eth_sendTransaction",
-                params: [TX_PARAMS],
+                params: [txParams || TX_PARAMS],
             },
             { origin: ORIGIN },
             sendResponse,
@@ -191,6 +224,30 @@ function loadBackground(options) {
         };
     }
 
+    // The same for a message-signing approval, which pins the signing address
+    // at approval time in exactly the same way.
+    function requestSign(from) {
+        let rpcResult = null;
+        messageListener(
+            {
+                type: "AUTISTMASK_RPC",
+                method: "personal_sign",
+                params: [MESSAGE, from || signer.address],
+            },
+            { origin: ORIGIN },
+            (r) => {
+                rpcResult = r;
+            },
+        );
+        return {
+            id: () =>
+                new URL(created[created.length - 1].url).searchParams.get(
+                    "approval",
+                ),
+            result: () => rpcResult,
+        };
+    }
+
     // The user closes the approval popup. `created` is index-aligned with the
     // ids the window stub hands back, so window 1 is the first popup opened.
     function closeWindow(windowId) {
@@ -200,18 +257,27 @@ function loadBackground(options) {
     return {
         send,
         requestTx,
+        requestSign,
         closeWindow,
         broadcastTransaction,
         loadState,
         created,
         removed,
+        // The user switching account in the toolbar popup, as the background
+        // sees it: the persisted active address changes underneath a pending
+        // approval.
+        setActiveAddress: (address) => {
+            persisted.activeAddress = address;
+        },
         fromPopup: { url: EXT_URL + "src/popup/index.html" },
     };
 }
 
-// Let the handler's promise chain run to the next suspension point.
+// Let the handler's promise chain run to the next suspension point. Raising a
+// transaction approval now populates it against the node first, which is
+// several awaits deep before the window is opened.
 async function settle() {
-    for (let i = 0; i < 10; i++) await Promise.resolve();
+    for (let i = 0; i < 50; i++) await Promise.resolve();
 }
 
 afterEach(() => {
@@ -244,9 +310,11 @@ describe("one approval, one broadcast", () => {
         await settle();
         expect(bg.broadcastTransaction).toHaveBeenCalledTimes(1);
 
-        // A reloaded approval window signs the same approval again. Nothing
+        // A reloaded approval window signs the same approval again, at another
-        // in the approval fixes a nonce, so this artifact verifies just as
+        // nonce. The claim is taken before anything is verified, so what this
-        // well as the first one.
+        // asserts is the interlock and not the nonce comparison: the refusal
+        // below is the claim's own message, which a verification failure does
+        // not produce.
         const second = bg.send(
             {
                 type: "AUTISTMASK_TX_RESPONSE",
@@ -376,6 +444,319 @@ describe("one approval, one broadcast", () => {
     });
 });
 
+// The approval carries the transaction the user was shown and the address it
+// was raised for, and the artifact is checked against both. Every case here is
+// one the old comparison — against the dApp's request, for the address that is
+// active now — would have broadcast.
+describe("what the approval is verified against", () => {
+    // The approval screen showed the populated fee. An artifact at ten times
+    // that fee, still far below the ceilings, is what the ceilings alone could
+    // not catch.
+    test("a fee differing from the displayed one is refused, not sent", async () => {
+        const bg = loadBackground();
+        const pending = bg.requestTx();
+        await settle();
+        const id = pending.id();
+
+        const raw = await signer.signTransaction({
+            ...populated(NONCE),
+            maxFeePerGas: 20000000000n,
+        });
+        const answer = bg.send(
+            {
+                type: "AUTISTMASK_TX_RESPONSE",
+                id,
+                approved: true,
+                rawSignedTx: raw,
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+
+        expect(bg.broadcastTransaction).not.toHaveBeenCalled();
+        expect(answer.sendResponse).toHaveBeenCalledWith(
+            expect.objectContaining({
+                error: expect.stringMatching(/approved maximum fee per gas/),
+                retryable: false,
+                stage: "verify",
+            }),
+        );
+        expect(pending.result()).toEqual({
+            error: {
+                message: expect.stringMatching(/approved maximum fee per gas/),
+            },
+        });
+    });
+
+    test("a nonce differing from the displayed one is refused, not sent", async () => {
+        const bg = loadBackground();
+        const pending = bg.requestTx();
+        await settle();
+        const id = pending.id();
+
+        const answer = bg.send(
+            {
+                type: "AUTISTMASK_TX_RESPONSE",
+                id,
+                approved: true,
+                rawSignedTx: await signedAtNonce(NONCE + 1),
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+
+        expect(bg.broadcastTransaction).not.toHaveBeenCalled();
+        expect(answer.sendResponse).toHaveBeenCalledWith(
+            expect.objectContaining({
+                error: expect.stringMatching(/approved nonce/),
+                retryable: false,
+                stage: "verify",
+            }),
+        );
+    });
+
+    // The address switch. The approval named one account; the wallet is on
+    // another by the time the artifact arrives. Both halves are covered: the
+    // popup signing as the account that is active now, and the popup correctly
+    // signing as the approved account while the wallet has moved on.
+    test("an artifact signed by the address that is active now is refused", async () => {
+        const bg = loadBackground();
+        const pending = bg.requestTx();
+        await settle();
+        const id = pending.id();
+
+        bg.setActiveAddress(other.address);
+        const answer = bg.send(
+            {
+                type: "AUTISTMASK_TX_RESPONSE",
+                id,
+                approved: true,
+                rawSignedTx: await signedAtNonce(NONCE, other),
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+
+        expect(bg.broadcastTransaction).not.toHaveBeenCalled();
+        expect(answer.sendResponse).toHaveBeenCalledWith(
+            expect.objectContaining({ retryable: false, stage: "verify" }),
+        );
+        expect(pending.result()).toEqual({
+            error: { message: expect.stringMatching(/active address changed/) },
+        });
+    });
+
+    test("an address switch refuses even the correctly signed artifact", async () => {
+        const bg = loadBackground();
+        const pending = bg.requestTx();
+        await settle();
+        const id = pending.id();
+
+        bg.setActiveAddress(other.address);
+        const answer = bg.send(
+            {
+                type: "AUTISTMASK_TX_RESPONSE",
+                id,
+                approved: true,
+                rawSignedTx: await signedAtNonce(NONCE),
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+
+        expect(bg.broadcastTransaction).not.toHaveBeenCalled();
+        expect(answer.sendResponse).toHaveBeenCalledWith(
+            expect.objectContaining({
+                error: expect.stringMatching(/active address changed/),
+                retryable: false,
+                stage: "verify",
+            }),
+        );
+        // A refusal, so the approval is spent: the same artifact offered again
+        // finds nothing to answer.
+        const retry = bg.send(
+            {
+                type: "AUTISTMASK_TX_RESPONSE",
+                id,
+                approved: true,
+                rawSignedTx: await signedAtNonce(NONCE),
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+        expect(retry.sendResponse).not.toHaveBeenCalled();
+        expect(bg.broadcastTransaction).not.toHaveBeenCalled();
+    });
+
+    test("a switch back to the approved address still sends", async () => {
+        const bg = loadBackground();
+        const pending = bg.requestTx();
+        await settle();
+        const id = pending.id();
+
+        bg.setActiveAddress(other.address);
+        bg.setActiveAddress(signer.address);
+        bg.broadcastTransaction.mockResolvedValue({ hash: "0xfeed" });
+        bg.send(
+            {
+                type: "AUTISTMASK_TX_RESPONSE",
+                id,
+                approved: true,
+                rawSignedTx: await signedAtNonce(NONCE),
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+
+        expect(bg.broadcastTransaction).toHaveBeenCalledTimes(1);
+        expect(pending.result()).toEqual({ result: "0xfeed" });
+    });
+
+    // The popup is handed the populated transaction and the address it is for,
+    // and nothing else it would have to fetch or decide.
+    test("the popup is given the transaction it is to sign", async () => {
+        const bg = loadBackground();
+        const pending = bg.requestTx();
+        await settle();
+
+        const details = bg.send(
+            { type: "AUTISTMASK_GET_APPROVAL", id: pending.id() },
+            { url: bg.fromPopup.url },
+        );
+        const shown = details.sendResponse.mock.calls[0][0];
+        expect(shown.type).toBe("tx");
+        expect(shown.approvedFrom).toBe(signer.address);
+        expect(shown.approvedTx).toEqual({
+            type: 2,
+            from: signer.address,
+            chainId: "0x1",
+            nonce: "0x7",
+            gasLimit: "0x186a0",
+            maxFeePerGas: "0x77359400",
+            maxPriorityFeePerGas: "0x3b9aca00",
+            to: RECIPIENT,
+            value: TX_PARAMS.value,
+            data: "0x",
+            accessList: [],
+        });
+    });
+
+    // A request naming an account the wallet is not on is refused outright
+    // rather than signed as whichever account is active.
+    test("a request from another address raises no approval at all", async () => {
+        const bg = loadBackground();
+        const pending = bg.requestTx({ ...TX_PARAMS, from: other.address });
+        await settle();
+
+        expect(pending.result()).toEqual({
+            error: {
+                code: 4100,
+                message: expect.stringMatching(/not the active one/),
+            },
+        });
+        expect(bg.created).toEqual([]);
+    });
+
+    // Message signing pins the address the same way, and refuses the same way.
+    // A signature is not a transaction, but a permit signed by an account the
+    // approval did not name spends that account's tokens all the same.
+    test("a sign approval refuses a signature after an address switch", async () => {
+        const bg = loadBackground();
+        const pending = bg.requestSign();
+        await settle();
+
+        bg.setActiveAddress(other.address);
+        const answer = bg.send(
+            {
+                type: "AUTISTMASK_SIGN_RESPONSE",
+                id: pending.id(),
+                approved: true,
+                signature: await signer.signMessage(
+                    Buffer.from(MESSAGE.slice(2), "hex"),
+                ),
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+
+        expect(answer.sendResponse).toHaveBeenCalledWith(
+            expect.objectContaining({
+                error: expect.stringMatching(/active address changed/),
+                retryable: false,
+            }),
+        );
+        expect(pending.result()).toEqual({
+            error: { message: expect.stringMatching(/active address changed/) },
+        });
+    });
+
+    test("a sign request from another address raises no approval at all", async () => {
+        const bg = loadBackground();
+        const pending = bg.requestSign(other.address);
+        await settle();
+
+        expect(pending.result()).toEqual({
+            error: {
+                code: 4100,
+                message: expect.stringMatching(/not the active one/),
+            },
+        });
+        expect(bg.created).toEqual([]);
+    });
+
+    // Population is a network round trip with the user's hands free. An
+    // approval raised for the address that was active when it started could
+    // never be signed once the wallet has moved off it, so it is never raised.
+    test("an address switch during population raises no approval", async () => {
+        let bg;
+        bg = loadBackground({
+            provider: {
+                // The user switches account in the toolbar popup while the
+                // node is being asked for a gas estimate.
+                estimateGas: async () => {
+                    bg.setActiveAddress(other.address);
+                    return 100000n;
+                },
+            },
+        });
+        const pending = bg.requestTx();
+        await settle();
+
+        expect(pending.result()).toEqual({
+            error: {
+                message: expect.stringMatching(
+                    /active address changed while this transaction was being prepared/,
+                ),
+            },
+        });
+        expect(bg.created).toEqual([]);
+    });
+
+    // Population happens before the window exists, so its failure is a failure
+    // of the request: no approval, no window, and the error goes back to the
+    // page the click came from.
+    test("a transaction that cannot be prepared opens no window", async () => {
+        const bg = loadBackground({
+            provider: {
+                estimateGas: async () => {
+                    throw new Error("execution reverted");
+                },
+            },
+        });
+        const pending = bg.requestTx();
+        await settle();
+
+        expect(pending.result()).toEqual({
+            error: {
+                message: expect.stringMatching(
+                    /could not be prepared.*execution reverted/,
+                ),
+            },
+        });
+        expect(bg.created).toEqual([]);
+    });
+});
+
 // The interlock must not cost the retry the approval exists to allow.
 describe("the interlock releases a failed attempt", () => {
     test("a retryable failure before the broadcast leaves the approval usable", async () => {

tests/e2e/firefox/Dockerfile

@@ -0,0 +1,51 @@
+# Firefox end-to-end image: stock Firefox plus geckodriver on a node base,
+# built by script/test-e2e-firefox. The repo is bind-mounted at /work; the
+# harness itself has no dependencies, so nothing is installed for it.
+#
+# All three external artifacts are pinned by digest. The Firefox version in
+# particular must not float: -remote-allow-system-access is mandatory on 153
+# and was not on 142, so the flag the harness passes is version-coupled.
+
+# node:22-bookworm-slim, 2026-08-12
+FROM node@sha256:d649c27dae7ba0137b3cef5dd75baa422c08dc3d9e3fc0c23dfb172dc3cc6436
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+# Firefox's shared-library dependencies on a slim base, plus the two tools
+# needed to fetch and unpack the pinned tarballs.
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends \
+        ca-certificates \
+        curl \
+        libasound2 \
+        libdbus-glib-1-2 \
+        libgtk-3-0 \
+        libx11-xcb1 \
+        libxt6 \
+        libxtst6 \
+        xz-utils \
+    && rm -rf /var/lib/apt/lists/*
+
+# Firefox 153.0.3, linux-x86_64, en-US
+ARG FIREFOX_URL=https://ftp.mozilla.org/pub/firefox/releases/153.0.3/linux-x86_64/en-US/firefox-153.0.3.tar.xz
+ARG FIREFOX_SHA256=22b312280900bfb174b685ece32c7b3c6d72e7f8e53d6d30f21ac41a8dc500a2
+RUN curl -fsSL -o /tmp/firefox.tar.xz "$FIREFOX_URL" \
+    && echo "$FIREFOX_SHA256  /tmp/firefox.tar.xz" | sha256sum -c - \
+    && tar -xJf /tmp/firefox.tar.xz -C /opt \
+    && rm /tmp/firefox.tar.xz \
+    && /opt/firefox/firefox --version
+
+# geckodriver v0.36.0, linux64
+ARG GECKODRIVER_URL=https://github.com/mozilla/geckodriver/releases/download/v0.36.0/geckodriver-v0.36.0-linux64.tar.gz
+ARG GECKODRIVER_SHA256=0bde38707eb0a686a20c6bd50f4adcc7d60d4f73c60eb83ee9e0db8f65823e04
+RUN curl -fsSL -o /tmp/geckodriver.tar.gz "$GECKODRIVER_URL" \
+    && echo "$GECKODRIVER_SHA256  /tmp/geckodriver.tar.gz" | sha256sum -c - \
+    && tar -xzf /tmp/geckodriver.tar.gz -C /usr/local/bin \
+    && rm /tmp/geckodriver.tar.gz \
+    && geckodriver --version
+
+ENV FIREFOX_BIN=/opt/firefox/firefox
+ENV GECKODRIVER=/usr/local/bin/geckodriver
+
+WORKDIR /work
+CMD ["node", "tests/e2e/firefox/run.js", "dist/firefox"]

tests/e2e/firefox/driver.js

@@ -0,0 +1,464 @@
+// A minimal WebDriver client for geckodriver, plus the privileged console
+// reader the error assertions are built on. No npm dependencies: global
+// fetch and child_process against geckodriver's HTTP API is less code than
+// a driver library and keeps the harness at zero packages.
+//
+// Run through script/test-e2e-firefox, which builds dist/firefox/ and the
+// pinned container around this. FIREFOX_BIN and GECKODRIVER locate the two
+// binaries; the image sets both.
+
+"use strict";
+
+const { spawn } = require("child_process");
+const net = require("net");
+
+const FIREFOX_BIN = process.env.FIREFOX_BIN || "firefox";
+const GECKODRIVER = process.env.GECKODRIVER || "geckodriver";
+
+// The extension id declared in manifest/firefox.json, and the uuid the
+// popup is served from. Firefox normally assigns that uuid randomly per
+// profile, which would make the popup URL undiscoverable without querying
+// privileged state; setting extensions.webextensions.uuids before launch
+// pins it instead. This only works because the manifest declares a fixed
+// browser_specific_settings.gecko.id — without one the mapping has no key.
+const EXTENSION_ID = "autistmask@sneak.berlin";
+const EXTENSION_UUID = "aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee";
+const EXTENSION_ORIGIN = "moz-extension://" + EXTENSION_UUID;
+
+// The W3C web element identifier. Getting the last character wrong yields
+// an element reference of "undefined" and a bewildering "element with the
+// reference undefined is not known" from geckodriver, so findElement()
+// below checks for the key rather than indexing blindly.
+const WEB_ELEMENT_KEY = "element-6066-11e4-a52e-4f735466cecf";
+
+const SCRIPT_TIMEOUT_MS = 120000;
+const DEFAULT_WAIT_MS = 20000;
+const POLL_INTERVAL_MS = 100;
+
+function sleep(ms) {
+    return new Promise((resolve) => setTimeout(resolve, ms));
+}
+
+// An ephemeral port picked by the kernel, then handed to geckodriver.
+// There is a race between closing this listener and geckodriver binding,
+// but this host runs many sessions at once and a fixed 4444 is a
+// guaranteed collision rather than a possible one.
+function freePort() {
+    return new Promise((resolve, reject) => {
+        const srv = net.createServer();
+        srv.on("error", reject);
+        srv.listen(0, "127.0.0.1", () => {
+            const { port } = srv.address();
+            srv.close(() => resolve(port));
+        });
+    });
+}
+
+class WebDriverError extends Error {
+    constructor(command, body) {
+        const v = (body && body.value) || {};
+        super(
+            command +
+                " failed: " +
+                (v.error || "unknown error") +
+                ": " +
+                (v.message || JSON.stringify(body)),
+        );
+        this.name = "WebDriverError";
+        this.error = v.error;
+    }
+}
+
+class Driver {
+    constructor(proc, base) {
+        this.proc = proc;
+        this.base = base;
+        this.sessionId = null;
+        this.context = "content";
+    }
+
+    async send(method, path, body) {
+        const url = this.base + path;
+        const res = await fetch(url, {
+            method,
+            headers: { "Content-Type": "application/json" },
+            body: body === undefined ? undefined : JSON.stringify(body),
+        });
+        const text = await res.text();
+        let parsed;
+        try {
+            parsed = JSON.parse(text);
+        } catch (_) {
+            throw new Error(
+                method + " " + path + ": non-JSON response: " + text,
+            );
+        }
+        if (!res.ok) throw new WebDriverError(method + " " + path, parsed);
+        return parsed.value;
+    }
+
+    session(method, path, body) {
+        return this.send(method, "/session/" + this.sessionId + path, body);
+    }
+
+    // ------------------------------------------------------------ setup
+
+    async newSession() {
+        const prefs = {
+            // See EXTENSION_UUID above. The pref is a string pref whose
+            // value is itself JSON.
+            "extensions.webextensions.uuids": JSON.stringify({
+                [EXTENSION_ID]: EXTENSION_UUID,
+            }),
+        };
+
+        const value = await this.send("POST", "/session", {
+            capabilities: {
+                alwaysMatch: {
+                    browserName: "firefox",
+                    "moz:firefoxOptions": {
+                        binary: FIREFOX_BIN,
+                        args: [
+                            "-headless",
+                            // Mandatory on Firefox 153: without it,
+                            // navigating to moz-extension:// and running
+                            // chrome-context script both fail with
+                            // "unsupported operation".
+                            //
+                            // It grants the driver FULL CHROME PRIVILEGES
+                            // over this browser. Acceptable only because
+                            // the browser is a throwaway in a CI
+                            // container; never point a session with this
+                            // flag at anything you care about.
+                            "-remote-allow-system-access",
+                        ],
+                        prefs,
+                    },
+                },
+            },
+        });
+        this.sessionId = value.sessionId;
+        await this.session("POST", "/timeouts", { script: SCRIPT_TIMEOUT_MS });
+        return value;
+    }
+
+    // Installs the unpacked MV2 build straight from a directory.
+    // temporary:true bypasses signature checks, so no XPI and no signing
+    // are involved, and the add-on dies with the profile.
+    async installAddon(dir) {
+        return this.session("POST", "/moz/addon/install", {
+            path: dir,
+            temporary: true,
+        });
+    }
+
+    // Classic navigation on purpose. BiDi's browsingContext.navigate
+    // refuses moz-extension:// URLs outright.
+    async navigate(url) {
+        await this.session("POST", "/url", { url });
+    }
+
+    async quit() {
+        if (this.sessionId) {
+            await this.session("DELETE", "").catch(() => {});
+            this.sessionId = null;
+        }
+        this.proc.kill("SIGTERM");
+    }
+
+    // ---------------------------------------------------------- scripts
+
+    async setContext(context) {
+        if (this.context === context) return;
+        await this.session("POST", "/moz/context", { context });
+        this.context = context;
+    }
+
+    async execute(script, args = []) {
+        await this.setContext("content");
+        return this.session("POST", "/execute/sync", { script, args });
+    }
+
+    // Runs in the privileged chrome scope, where Services and Ci exist.
+    async executeChrome(script, args = []) {
+        await this.setContext("chrome");
+        try {
+            return await this.session("POST", "/execute/sync", {
+                script,
+                args,
+            });
+        } finally {
+            await this.setContext("content");
+        }
+    }
+
+    // ------------------------------------------------------- page waits
+
+    // Polls a content-context expression until it returns truthy. Every
+    // wait in the suite goes through here so a timeout always says which
+    // condition it was waiting on rather than "timed out".
+    async waitFor(what, script, args = [], timeout = DEFAULT_WAIT_MS) {
+        const deadline = Date.now() + timeout;
+        let last = null;
+        for (;;) {
+            try {
+                const v = await this.execute(script, args);
+                if (v) return v;
+                last = null;
+            } catch (e) {
+                // A navigation or view swap in flight makes execute
+                // throw; that is a not-yet, not a failure, until the
+                // deadline says otherwise.
+                last = e.message;
+            }
+            if (Date.now() >= deadline) {
+                throw new Error(
+                    "timed out after " +
+                        timeout +
+                        "ms waiting for " +
+                        what +
+                        (last ? " (last error: " + last + ")" : ""),
+                );
+            }
+            await sleep(POLL_INTERVAL_MS);
+        }
+    }
+
+    // Shown means shown: in the popup a view is switched by toggling a
+    // "hidden" class, and an element that is present but collapsed is not
+    // the thing a test means by visible.
+    async waitVisible(selector, timeout = DEFAULT_WAIT_MS) {
+        return this.waitFor(
+            "selector " + selector + " to be visible",
+            `const el = document.querySelector(arguments[0]);
+             if (!el) return false;
+             const r = el.getBoundingClientRect();
+             return r.width > 0 && r.height > 0;`,
+            [selector],
+            timeout,
+        );
+    }
+
+    async isVisible(selector) {
+        return this.execute(
+            `const el = document.querySelector(arguments[0]);
+             if (!el) return false;
+             const r = el.getBoundingClientRect();
+             return r.width > 0 && r.height > 0;`,
+            [selector],
+        );
+    }
+
+    async count(selector) {
+        return this.execute(
+            "return document.querySelectorAll(arguments[0]).length;",
+            [selector],
+        );
+    }
+
+    async text(selector) {
+        return this.execute(
+            `const el = document.querySelector(arguments[0]);
+             return el ? el.textContent : null;`,
+            [selector],
+        );
+    }
+
+    async title() {
+        return this.session("GET", "/title");
+    }
+
+    // The id of the view element currently on top, which is what a
+    // failing step needs to report: "the screen did not change" is only
+    // useful if it says which screen it stayed on.
+    async currentView() {
+        return this.execute(
+            `const views = document.querySelectorAll('[id^="view-"]');
+             for (const v of views) {
+                 const r = v.getBoundingClientRect();
+                 if (r.width > 0 && r.height > 0) return v.id;
+             }
+             return null;`,
+        );
+    }
+
+    // ----------------------------------------------------- interactions
+
+    async findElement(selector) {
+        const value = await this.session("POST", "/element", {
+            using: "css selector",
+            value: selector,
+        });
+        const ref = value && value[WEB_ELEMENT_KEY];
+        if (typeof ref !== "string") {
+            throw new Error(
+                "no " +
+                    WEB_ELEMENT_KEY +
+                    " in the element response for " +
+                    selector +
+                    ": " +
+                    JSON.stringify(value),
+            );
+        }
+        return ref;
+    }
+
+    // Real WebDriver clicks and real key events rather than in-page
+    // .click() and value assignment: the popup's handlers are wired to
+    // events, and synthesising them from inside the page would test the
+    // harness's idea of the UI instead of the UI.
+    async click(selector) {
+        await this.waitVisible(selector);
+        const id = await this.findElement(selector);
+        await this.session("POST", "/element/" + id + "/click", {});
+    }
+
+    async fill(selector, value) {
+        await this.waitVisible(selector);
+        const id = await this.findElement(selector);
+        await this.session("POST", "/element/" + id + "/clear", {});
+        await this.session("POST", "/element/" + id + "/value", {
+            text: String(value),
+        });
+    }
+
+    async value(selector) {
+        return this.execute(
+            `const el = document.querySelector(arguments[0]);
+             return el ? el.value : null;`,
+            [selector],
+        );
+    }
+}
+
+// ------------------------------------------------------- error capture
+
+// Uncaught errors from extension code, read out of the privileged console
+// service.
+//
+// This is not the obvious mechanism, and the obvious one does not work:
+// WebDriver BiDi's log.entryAdded delivers NOTHING for extension pages.
+// Verified on Firefox 142 and 153 against a same-session control — a plain
+// http:// page yields uncaught errors with stack traces, the
+// moz-extension:// popup yields zero events, because the remote agent
+// excludes extension browsing contexts from BiDi observation. A harness
+// built on Playwright-BiDi or Puppeteer-BiDi therefore sees nothing and
+// reports success. Do not "simplify" this back to BiDi.
+//
+// nsIConsoleService is not per-page: it also carries errors from the
+// background page, which BiDi would not have covered even if it worked.
+// Background-page capture is verified by probe — a throw at the top of
+// src/background/index.js, which kills the background page outright, fails
+// the run. Content-script errors should arrive by the same route, but that
+// is UNVERIFIED here and must not be claimed: the container runs with
+// --network none, so there is no http:// page for a content script to be
+// injected into and this suite never exercises one.
+//
+// Warnings are excluded so the semantics match Playwright's pageerror:
+// uncaught errors only.
+//
+// The read and the clear are ONE chrome script on purpose. Splitting them
+// into two round trips leaves a blind window between them in which an
+// error is logged into a buffer that is about to be discarded, and is
+// destroyed unread rather than deferred to the next drain. That was not
+// theoretical: with a separate reset() call, a probe of 100 sequenced
+// throws at 20ms spacing lost one of them outright.
+const DRAIN_ERRORS_SCRIPT = `
+    const origin = arguments[0];
+    const out = [];
+    for (const raw of Services.console.getMessageArray() || []) {
+        let e;
+        try {
+            e = raw.QueryInterface(Ci.nsIScriptError);
+        } catch (_) {
+            continue;
+        }
+        if (e.flags & Ci.nsIScriptError.warningFlag) continue;
+        const src = e.sourceName || "";
+        if (!src.startsWith(origin)) continue;
+        out.push({
+            msg: e.errorMessage,
+            src: src,
+            line: e.lineNumber,
+            cat: e.category,
+        });
+    }
+    Services.console.reset();
+    return out;
+`;
+
+class ConsoleErrors {
+    constructor(driver, originPrefix) {
+        this.driver = driver;
+        this.originPrefix = originPrefix;
+    }
+
+    // Everything logged since the last take, read and cleared atomically
+    // in a single chrome round trip. Poll-based, so an error is attributed
+    // to the step that was running when it was drained, not to the moment
+    // inside that step at which it happened — see the limitation note in
+    // run.js. An error that arrives mid-drain is not lost — it makes this
+    // batch or the next one — but the console service ring buffer holds
+    // only 250 messages, so more than that between two takes evicts the
+    // oldest unread. A clean run peaks at 4.
+    async take() {
+        const found = await this.driver.executeChrome(DRAIN_ERRORS_SCRIPT, [
+            this.originPrefix,
+        ]);
+        return found || [];
+    }
+}
+
+// ------------------------------------------------------------- startup
+
+async function waitForDriverReady(base, timeoutMs) {
+    const deadline = Date.now() + timeoutMs;
+    for (;;) {
+        try {
+            const res = await fetch(base + "/status");
+            if (res.ok) {
+                const body = await res.json();
+                if (body && body.value && body.value.ready !== false) return;
+            }
+        } catch (_) {
+            // not listening yet
+        }
+        if (Date.now() >= deadline) {
+            throw new Error(
+                "geckodriver did not become ready within " + timeoutMs + "ms",
+            );
+        }
+        await sleep(POLL_INTERVAL_MS);
+    }
+}
+
+async function start() {
+    const port = await freePort();
+    const proc = spawn(
+        GECKODRIVER,
+        ["--port", String(port), "--host", "127.0.0.1"],
+        { stdio: ["ignore", "inherit", "inherit"] },
+    );
+    proc.on("error", (e) => {
+        console.error("geckodriver failed to spawn: " + e.message);
+    });
+
+    const base = "http://127.0.0.1:" + port;
+    try {
+        await waitForDriverReady(base, 30000);
+    } catch (e) {
+        proc.kill("SIGKILL");
+        throw e;
+    }
+    return new Driver(proc, base);
+}
+
+module.exports = {
+    ConsoleErrors,
+    Driver,
+    EXTENSION_ID,
+    EXTENSION_ORIGIN,
+    EXTENSION_UUID,
+    start,
+    sleep,
+};

tests/e2e/firefox/run.js

@@ -0,0 +1,288 @@
+// Firefox end-to-end suite: drives the real popup in a real Firefox with
+// the unpacked MV2 build installed as a temporary add-on, and fails the run
+// on any uncaught error coming from an extension source.
+//
+// Run via script/test-e2e-firefox, which builds dist/firefox/ and the pinned
+// container. The extension directory is the one argument.
+//
+//   node tests/e2e/firefox/run.js [dist/firefox]
+//
+// Deliberately not part of script/check, and deliberately not named
+// *.test.js: REPO_POLICIES.md caps make test at 20 seconds and a browser
+// suite does not fit.
+//
+// This shares no driver layer with the Chrome suite in tests/e2e/, and the
+// UI steps below are written twice on purpose. Chrome runs on Playwright,
+// which cannot see extension-page errors in Firefox at all (see the BiDi
+// note in driver.js), so the two backends have no common substrate to
+// abstract over. Three duplicated steps do not pay for a shim; revisit if
+// this suite grows to where they do.
+//
+// LIMITATION, and the difference from the Chrome suite worth knowing: error
+// capture here is POLL-BASED, not event-streamed. The console service is
+// drained at each step boundary, so an error is attributed to the step it
+// was drained after, never to a moment within that step. What is drained
+// covers the whole run from add-on install to the last drain below, which
+// lands ~1.5s after the last step returns (500ms settle + 1000ms sleep +
+// two drain round trips). That cut-off jitters run to run: three runs of
+// throws at fixed offsets reported everything to +1.5s and one of them
+// also +1.6s, and past it the browser is torn down first. Inside the
+// window there is no race — the drain reads and clears in one chrome
+// round trip — but there is a capacity limit: nsIConsoleService keeps
+// only the newest 250 messages, so 400 throws in one step report as
+// exactly 250. A clean run peaks at 4 of 250, so that is headroom today
+// and not a guarantee for a step that logs heavily. The Chrome harness
+// receives pageerror events as they happen and can say more. Do not read
+// a green Firefox run as the same claim.
+
+"use strict";
+
+const fs = require("fs");
+const path = require("path");
+
+const { ConsoleErrors, EXTENSION_ORIGIN, start, sleep } = require("./driver");
+
+const REPO_ROOT = path.resolve(__dirname, "..", "..", "..");
+const POPUP_URL = EXTENSION_ORIGIN + "/src/popup/index.html";
+const PASSWORD = "e2e-harness-password";
+
+// Firefox installs the add-on and starts its background page asynchronously
+// after the install call returns. Nothing observable marks the end of that,
+// so the popup's own first render is the signal we wait on instead.
+const STEP_TIMEOUT_MS = 120000;
+
+const steps = [];
+
+function step(name, fn) {
+    steps.push({ name, fn });
+}
+
+function assert(cond, message) {
+    if (!cond) throw new Error(message);
+}
+
+function withTimeout(promise, name) {
+    let timer;
+    const timeout = new Promise((_, reject) => {
+        timer = setTimeout(
+            () =>
+                reject(
+                    new Error(
+                        name + " timed out after " + STEP_TIMEOUT_MS + "ms",
+                    ),
+                ),
+            STEP_TIMEOUT_MS,
+        );
+    });
+    return Promise.race([promise, timeout]).finally(() => clearTimeout(timer));
+}
+
+// ------------------------------------------------------------- steps
+
+step("popup loads and reaches the welcome view", async (env) => {
+    const d = env.driver;
+    await d.navigate(POPUP_URL);
+    await d.waitVisible("#view-welcome", STEP_TIMEOUT_MS);
+    const title = await d.title();
+    assert(title === "AutistMask", "unexpected popup title: " + title);
+});
+
+step("wallet creation through the UI reaches the main view", async (env) => {
+    const d = env.driver;
+    await d.click("#btn-welcome-add");
+    await d.waitVisible("#view-add-wallet");
+    await d.click("#btn-generate-phrase");
+    await d.waitFor(
+        "a generated recovery phrase of at least 12 words",
+        `const el = document.getElementById("wallet-mnemonic");
+         return !!el && el.value.trim().split(/\\s+/).length >= 12;`,
+    );
+    env.phrase = (await d.value("#wallet-mnemonic")).trim();
+
+    await d.fill("#add-wallet-password", PASSWORD);
+    await d.fill("#add-wallet-password-confirm", PASSWORD);
+    await d.click("#btn-add-wallet-confirm");
+    // Argon2id under libsodium, for real, so this is the slow one.
+    await d.waitVisible("#view-main", STEP_TIMEOUT_MS);
+
+    assert(
+        env.phrase.split(/\s+/).length >= 12,
+        "wallet creation did not yield a recovery phrase",
+    );
+    const addrs = await d.count("#wallet-list .btn-addr-info");
+    assert(addrs > 0, "no addresses rendered in the wallet list");
+});
+
+step("add token screen opens from address detail", async (env) => {
+    const d = env.driver;
+    if (!(await d.isVisible("#view-address"))) {
+        await d.waitVisible("#view-main");
+        await d.click("#wallet-list .btn-addr-info");
+    }
+    await d.waitVisible("#view-address");
+
+    await d.click("#btn-add-token");
+    // Reported with the view it actually stayed on: a screen that does
+    // not change is the symptom a missing import produces, and naming
+    // the screen is what makes that diagnosable.
+    try {
+        await d.waitVisible("#view-add-token");
+    } catch (e) {
+        throw new Error(
+            e.message + "; current view is " + (await d.currentView()),
+        );
+    }
+
+    const picks = await d.count("#common-token-list .common-token");
+    assert(picks > 0, "no common-token quick-pick buttons rendered");
+});
+
+// ------------------------------------------------------------- runner
+
+function formatError(e) {
+    return (
+        e.msg + " (" + e.src + ":" + e.line + (e.cat ? ", " + e.cat : "") + ")"
+    );
+}
+
+async function main() {
+    // A suite that runs nothing must never report success.
+    if (steps.length === 0) {
+        console.log("1..0");
+        console.log("# FAILED: the Firefox e2e suite registered no steps");
+        process.exitCode = 1;
+        return;
+    }
+
+    const extDir = path.resolve(REPO_ROOT, process.argv[2] || "dist/firefox");
+    if (!fs.existsSync(path.join(extDir, "manifest.json"))) {
+        console.error(
+            "e2e-firefox: no unpacked build at " +
+                extDir +
+                " — run make build first",
+        );
+        process.exitCode = 1;
+        return;
+    }
+
+    let driver;
+    try {
+        driver = await start();
+        await driver.newSession();
+        await driver.installAddon(extDir);
+    } catch (e) {
+        // A browser we cannot start is a failure of the suite, not an
+        // absent suite. Never skip and report success.
+        console.error("e2e-firefox: cannot run the suite: " + e.message);
+        if (driver) await driver.quit().catch(() => {});
+        process.exitCode = 1;
+        return;
+    }
+
+    const errors = new ConsoleErrors(driver, EXTENSION_ORIGIN);
+    const env = { driver, phrase: null };
+
+    console.log("# extension origin: " + EXTENSION_ORIGIN);
+    console.log("1.." + steps.length);
+
+    let failed = 0;
+    let n = 0;
+    try {
+        // Drain, never reset: anything the add-on logged while installing
+        // and starting its background page has no earlier step to belong
+        // to, so it is folded into step 1 below. Services.console.reset()
+        // here would DELETE it instead, and a background page that throws
+        // at the top of the file — a dead background page — would then
+        // produce a fully green run.
+        let installErrors = [];
+        let installFailure = null;
+        try {
+            installErrors = await errors.take();
+        } catch (e) {
+            installFailure =
+                "could not read the console after install: " + e.message;
+        }
+
+        for (const s of steps) {
+            n += 1;
+            let failure = null;
+            try {
+                await withTimeout(s.fn(env), s.name);
+            } catch (e) {
+                failure = e.message;
+            }
+
+            // Let anything the step provoked reach the console service
+            // before draining it. Without this a failure logged on the
+            // way out of the step lands in the next step's drain, which
+            // still fails the run but blames the wrong step.
+            await sleep(500);
+
+            let found = [];
+            try {
+                found = await errors.take();
+            } catch (e) {
+                failure = failure || "could not read the console: " + e.message;
+            }
+
+            if (n === 1) {
+                found = installErrors.concat(found);
+                installErrors = [];
+                failure = failure || installFailure;
+                installFailure = null;
+            }
+
+            // Any uncaught error from an extension source fails the step
+            // that provoked it, whether or not its assertions passed.
+            if (!failure && found.length > 0) {
+                failure =
+                    n === 1
+                        ? "uncaught extension errors during add-on install, " +
+                          "background startup or this step"
+                        : "uncaught extension errors during this step";
+            }
+
+            if (failure) {
+                failed += 1;
+                console.log("not ok " + n + " - " + s.name);
+                console.log("  " + failure);
+                for (const e of found) console.log("  " + formatError(e));
+            } else {
+                console.log("ok " + n + " - " + s.name);
+            }
+        }
+
+        // The tail: errors logged after the last step returned cannot be
+        // blamed on any one step, but they are still reported and they
+        // still fail the run.
+        await sleep(1000);
+        const trailing = await errors.take();
+        console.log(
+            "# " +
+                (steps.length - failed) +
+                "/" +
+                steps.length +
+                " steps passed",
+        );
+        if (trailing.length > 0) {
+            console.log(
+                "# " +
+                    trailing.length +
+                    " extension error(s) recorded after the last step, not " +
+                    "attributable to any single step:",
+            );
+            for (const e of trailing) console.log("#   " + formatError(e));
+        }
+        if (failed > 0 || trailing.length > 0) {
+            console.log("# FAILED");
+            process.exitCode = 1;
+        }
+    } finally {
+        await driver.quit().catch(() => {});
+    }
+}
+
+main().catch((e) => {
+    console.error("e2e-firefox: " + (e && e.stack ? e.stack : e));
+    process.exitCode = 1;
+});

tests/symbolSpoof.test.js

@@ -209,10 +209,21 @@ describe("the shared rule: symbols that render as a known symbol", () => {
         expect(isSpoofedSymbol("E" + VS1 + "TH", FAKE_ETH_CONTRACT)).toBe(true);
     });
 
-    // The strip stops at default-ignorable and must not creep past it: the
+    // Nor is it confined to the Unicode classes.  U+007F is a control (Cc)
-    // C0 and C1 controls render as a visible 48.00px box in the same
+    // and is not default-ignorable, so neither class reaches it, but it
-    // browser, so a symbol carrying one does not look like `ETH` and must
+    // measures 32.00px in the same browser — it paints nothing, so a
-    // not be judged a spoof.
+    // symbol carrying it reaches the eye as `ETH`.  It is named on its own
+    // in the strip for exactly that reason.
+    test("U+007F paints nothing and is stripped", () => {
+        expect(isSpoofedSymbol(DEL + "ETH", FAKE_ETH_CONTRACT)).toBe(true);
+    });
+
+    // The other side of the boundary, which is not the class boundary but
+    // the visibility one: the remaining C0 and C1 controls render as a
+    // visible 48.00px box in the same browser, so a symbol carrying one
+    // does not look like `ETH` and must not be judged a spoof.  Widening
+    // the strip to \p{Cc} — the obvious over-correction once U+007F is in
+    // it — fails this test.
     test("visible control characters do not make a symbol a spoof", () => {
         expect(isSpoofedSymbol(NEL + "ETH", FAKE_ETH_CONTRACT)).toBe(false);
         expect(isSpoofedSymbol(cp(0x0001) + "ETH", FAKE_ETH_CONTRACT)).toBe(
@@ -223,15 +234,6 @@ describe("the shared rule: symbols that render as a known symbol", () => {
         );
     });
 
-    // Known gap, recorded rather than endorsed: U+007F is a control (Cc),
-    // not default-ignorable, so the strip does not reach it — but unlike
-    // the rest of its class it measures 32.00px, i.e. it paints nothing.
-    // Closing it means picking a rule for the controls, which is a decision
-    // of its own; this assertion is here so the gap cannot be forgotten.
-    test("U+007F renders as nothing and is knowingly still not caught", () => {
-        expect(isSpoofedSymbol(DEL + "ETH", FAKE_ETH_CONTRACT)).toBe(false);
-    });
-
     test("compatibility forms fold onto the symbol they imitate", () => {
         expect(isSpoofedSymbol(FULLWIDTH_ETH, FAKE_ETH_CONTRACT)).toBe(true);
         expect(isSpoofedSymbol(FULLWIDTH_USDC, FAKE_ETH_CONTRACT)).toBe(true);