security: announce a fresh EIP-6963 provider UUID per page load (closes #398)

The provider UUID was generated once, stored in extension storage, and
announced verbatim to every page on every load and across restarts, so any
site — connected or not — could read a stable cross-site, cross-session
identifier for the install: a supercookie contradicting the "no tracking"
promise. EIP-6963 wants a fresh UUIDv4 per announcement instead.

inpage.js now announces a per-load crypto.randomUUID() and persists nothing;
the eip6963Uuid storage key and the AUTISTMASK_PROVIDER_UUID content-script
message are removed. That key was a standalone top-level storage entry, never
part of the versioned autistmask profile, so stateSchema.js and the
persisted-field harness are untouched and no existing profile is affected.

A jest test asserts two loads announce different UUIDv4s and that one load
reuses a single UUID across re-announcements.

Model: opus-4-8

README.md

@@ -882,18 +882,9 @@ On those screens, when the truncated string would contain no digit from 1 to 9
 and the value does, the amount is extended to its first significant digit
 instead: `0.000000000000000001 DAI`, not `0.0000 DAI`. The test is on the whole
 truncated string, integer part included, so `1.00005` still shows as `1.0000` —
-the exception only fires where the entire displayed figure would read as zero.
-Truncation stays truncation: `0.99999` shows as `0.9999`, never rounded up. A
-genuine zero reaching this rule renders `0.0000`. The ERC-20
-`approve`/`transfer` amount does exactly that, and so does the swap's `Amount`
-line for a literal-zero `amountIn` on a V2 or V3 exact-in swap, or a zero
-`WRAP_ETH` (`0.0000 ETH`). Only two zeros are stated in words before the floor:
-the swap's `Min. received` line reads `None (no minimum guaranteed)` for any
-zero minimum, and its `Amount` line reads `All available (V4 open delta)` for a
-V4 exact-in `amountIn` of zero, which V4 treats as the whole open credit rather
-than a quantity. So the guarantee that a zero is never shown as `0.0000` covers
-the `Min. received` line and the V4 exact-in `Amount`; a V2/V3 or `WRAP_ETH`
-`Amount` still renders it (see the list of amount-slot strings below).
+the exception only fires where the entire displayed figure would read as zero. A
+genuine zero still renders `0.0000`, and truncation stays truncation: `0.99999`
+shows as `0.9999`, never rounded up.
 
 The rule and its exception live in `src/shared/amountDisplay.js` as
 `truncateAmount()` and `truncateAmountNeverZero()`. Everything the approval and
@@ -945,38 +936,6 @@ and compare against. Reading the stored field directly instead answers `null`
 for a bundled or tracked token the explorer merely omitted, which is not a
 refusal the wallet has any reason to make.
 
-**Every string an amount slot can show:** taken together, the exceptions above
-mean an amount line on the dApp approval screen (and the wait/success/error
-screens that carry a figure forward) shows one of a fixed set of strings, not
-always a number:
-
-- A formatted quantity, e.g. `17.1900 USDT`: the token's scale is known and the
-  figure is at or above the floor, or below it and extended to its first
-  significant digit. This is `truncateAmountNeverZero()`
-  (`src/shared/amountDisplay.js`).
-- `Unlimited`: an unbounded allowance or permit, which needs no scale to
-  describe — a `uint256`-max ERC-20 `approve` (`src/popup/views/approval.js`) or
-  a Permit2 amount at the `uint160` max on a swap's `Amount`
-  (`src/shared/uniswap.js`).
-- `All available (V4 open delta)`: a V4 exact-in swap whose `amountIn` is zero.
-  V4 reads that zero as "use the whole open delta", not as a literal zero, so
-  the calldata states no quantity at all. Swap `Amount` line only
-  (`src/shared/uniswap.js`).
-- `None (no minimum guaranteed)`: a zero minimum — the swap guarantees nothing
-  back. It is a literal zero slippage floor on a V2/V3/V4 swap, and it also
-  reaches a `BALANCE_CHECK_ERC20` step: a zero `minBalance`, which once rendered
-  `0.0000` beside the token symbol, now reads this. Swap `Min. received` line
-  (`src/shared/uniswap.js`).
-- `<amount> base units (decimals unknown)`: the token's scale could not be
-  resolved, so the base-unit integer is shown with that caveat rather than
-  formatted (see Unknown token scale above). Reaches both the ERC-20 amount line
-  and the swap's `Amount` and `Min. received` (`unknownDecimalsAmount()` in
-  `src/shared/approvalAmount.js`).
-- `Unknown (not named in the calldata)`: not an amount but the currency itself —
-  the `Token In` or `Token Out` line when nothing in the calldata established
-  which token, shown beside the amount and, like the strings above, a sentence
-  rather than a value (`src/shared/uniswap.js`).
-
 #### Partial USD totals
 
 Prices are fetched for the top 25 tokens only, so an address can hold assets the

TODO.md

@@ -143,20 +143,16 @@ but the review is broader than any of them.
   both routes take, so they behave the same and the button is live for the next
   delete.
 
-- 2026-09-21: `README.md` now documents the approval screen's amount-slot
-  vocabulary and no longer contradicts itself
-  ([#369](https://git.eeqj.de/sneak/AutistMask/issues/369)). The stale claim
-  that a genuine zero still renders `0.0000` is corrected: it holds for the
-  ERC-20 amount, and also for the swap's `Amount` line on a literal-zero
-  `amountIn` in a V2/V3 exact-in swap or a zero `WRAP_ETH`. Only two zeros are
-  stated in words upstream — the swap's `Min. received` (any zero minimum) and
-  its V4 exact-in `Amount` (an `amountIn` of zero, V4's open delta). The
-  amount-display section now names every string a slot can show — a formatted
-  quantity, `Unlimited`, `All available (V4 open delta)`,
-  `None (no minimum guaranteed)`, base units with decimals unknown, and
-  `Unknown (not named in the calldata)` — and records that a zero `minBalance`
-  on a `BALANCE_CHECK_ERC20` step now reads `None (no minimum guaranteed)` where
-  it once read `0.0000`. Docs only; each claim checked against the tree.
+- 2026-09-21: The EIP-6963 provider UUID is generated fresh on each page load
+  and never persisted ([#398](https://git.eeqj.de/sneak/AutistMask/issues/398)).
+  It was created once and stored, then announced verbatim to every page on every
+  load and across restarts, so any site — connected or not — could read it as a
+  stable cross-site, cross-session identifier for the install, contradicting the
+  "no tracking" promise. inpage.js now announces a per-load
+  `crypto.randomUUID()` and the `eip6963Uuid` storage key and the
+  `AUTISTMASK_PROVIDER_UUID` content-script message are gone. That key was a
+  standalone storage entry, never part of the versioned `autistmask` profile, so
+  the state schema is untouched and no existing profile is affected.
 
 - 2026-08-30: An address no longer wraps, or is shortened to fit, in any of the
   common views ([#380](https://git.eeqj.de/sneak/AutistMask/issues/380)). The

src/content/index.js

@@ -5,8 +5,6 @@ const {
     hasBrowserNamespace,
     runtimeApi,
     sendMessage,
-    storageGet,
-    storageSet,
 } = require("../shared/browserApi");
 
 // In Chrome (MV3), inpage.js runs as a MAIN-world content script declared
@@ -21,30 +19,6 @@ if (hasBrowserNamespace()) {
     (document.head || document.documentElement).appendChild(script);
 }
 
-// Send the persisted EIP-6963 provider UUID to the inpage script.
-// Generated once at install time and stored in extension storage.
-(async function sendProviderUuid() {
-    let uuid = null;
-    try {
-        const items = await storageGet("eip6963Uuid");
-        uuid = items?.eip6963Uuid;
-        if (!uuid) {
-            uuid = crypto.randomUUID();
-            await storageSet({ eip6963Uuid: uuid });
-        }
-    } catch {
-        // Storage was unavailable or refused the write. The announcement
-        // still has to go out — a provider that never announces is invisible
-        // to every EIP-6963 dApp — so it goes under a fresh uuid that this
-        // page load will not outlive.
-        if (!uuid) uuid = crypto.randomUUID();
-    }
-    window.postMessage(
-        { type: "AUTISTMASK_PROVIDER_UUID", uuid },
-        location.origin,
-    );
-})();
-
 // Relay requests from the page to the background script
 window.addEventListener("message", (event) => {
     if (event.source !== window) return;

src/content/inpage.js

@@ -204,7 +204,14 @@
                 "</svg>",
         );
 
-    let providerUuid = crypto.randomUUID(); // fallback until real UUID arrives
+    // EIP-6963 wants a fresh UUIDv4 per page load — it identifies one
+    // announcement, so a provider can be told apart from another instance of
+    // itself in the same page. It is generated here and never stored:
+    // announcing one persisted value to every site, on every load and across
+    // restarts, turned it into a stable cross-site, cross-session tracking
+    // identifier any page could read
+    // (https://git.eeqj.de/sneak/AutistMask/issues/398).
+    const providerUuid = crypto.randomUUID();
 
     function buildProviderInfo() {
         return {
@@ -226,16 +233,6 @@
         );
     }
 
-    // Listen for the persisted UUID from the content script
-    function onProviderUuid(event) {
-        if (event.source !== window) return;
-        if (event.data?.type !== "AUTISTMASK_PROVIDER_UUID") return;
-        window.removeEventListener("message", onProviderUuid);
-        providerUuid = event.data.uuid;
-        announceProvider();
-    }
-    window.addEventListener("message", onProviderUuid);
-
     window.addEventListener("eip6963:requestProvider", announceProvider);
     announceProvider();
 

tests/e2e/firefox/run.js

@@ -372,10 +372,10 @@ step("the loopback dApp page gets the real inpage provider", async (env) => {
         STEP_TIMEOUT_MS,
     );
 
-    // EIP-6963, asked of the provider itself. The announcement carries the
-    // uuid src/content/index.js reads out of extension storage — call site 1
-    // in the issue — and it has to name this extension and hand back the very
-    // object on window.ethereum.
+    // EIP-6963, asked of the provider itself. The announcement carries a
+    // UUIDv4 inpage.js generates fresh for this page load (nothing persists
+    // it — see issue #398) and has to name this extension and hand back the
+    // very object on window.ethereum.
     const announced = await d.executeAsync(
         `const done = arguments[arguments.length - 1];
          const onAnnounce = (e) => {
@@ -402,7 +402,7 @@ step("the loopback dApp page gets the real inpage provider", async (env) => {
     );
     assert(
         typeof announced.uuid === "string" && announced.uuid.length === 36,
-        "the announcement carries no stored provider uuid: " +
+        "the announcement carries no provider uuid: " +
             JSON.stringify(announced.uuid),
     );
 

tests/inpageProviderUuid.test.js

@@ -0,0 +1,103 @@
+// The EIP-6963 provider UUID inpage.js announces (src/content/inpage.js).
+//
+// The bug this pins down (issue #398): the UUID used to be generated once,
+// persisted in extension storage, and announced verbatim to every page on
+// every load and across browser restarts, so any site — connected or not —
+// could read a stable cross-site, cross-session identifier for the install.
+// EIP-6963 wants a fresh UUIDv4 per announcement instead. The fix generates
+// it per page load and stores nothing.
+//
+// inpage.js is a bare IIFE injected into the page's JS context, not a module;
+// see tests/inpageErrors.test.js for why it is evaluated against a stub window
+// rather than imported. Here the stub captures the CustomEvent that carries
+// the announcement, so the UUID this file reads is the one a real dApp's
+// eip6963:announceProvider listener would see.
+
+const fs = require("fs");
+const path = require("path");
+const { webcrypto } = require("crypto");
+
+const SOURCE = fs.readFileSync(
+    path.join(__dirname, "..", "src", "content", "inpage.js"),
+    "utf8",
+);
+
+const loadInto = new Function(
+    "window",
+    "self",
+    "crypto",
+    "Event",
+    "CustomEvent",
+    SOURCE,
+);
+
+class StubEvent {
+    constructor(type) {
+        this.type = type;
+    }
+}
+
+class StubCustomEvent extends StubEvent {
+    constructor(type, init) {
+        super(type);
+        this.detail = init && init.detail;
+    }
+}
+
+// Evaluate inpage.js once against a fresh stub window and return every UUID it
+// announced. A `requestProvider` event is dispatched too, so a re-announcement
+// within one load is observed as well as the announcement at load.
+function announcedUuids() {
+    const listeners = {};
+    const uuids = [];
+
+    const win = {
+        addEventListener(type, fn) {
+            (listeners[type] || (listeners[type] = [])).push(fn);
+        },
+        removeEventListener(type, fn) {
+            const fns = listeners[type];
+            if (!fns) return;
+            const i = fns.indexOf(fn);
+            if (i !== -1) fns.splice(i, 1);
+        },
+        postMessage() {},
+        dispatchEvent(event) {
+            if (event.type === "eip6963:announceProvider") {
+                uuids.push(event.detail.info.uuid);
+            }
+            for (const fn of (listeners[event.type] || []).slice()) fn(event);
+            return true;
+        },
+    };
+    win.window = win;
+
+    loadInto(win, win, webcrypto, StubEvent, StubCustomEvent);
+    win.dispatchEvent(new StubEvent("eip6963:requestProvider"));
+    return uuids;
+}
+
+const UUID_V4 =
+    /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/;
+
+describe("the EIP-6963 provider UUID is fresh per page load", () => {
+    test("a load announces a UUIDv4, unprompted, with nothing delivered", () => {
+        const uuids = announcedUuids();
+        expect(uuids.length).toBeGreaterThan(0);
+        expect(uuids[0]).toMatch(UUID_V4);
+    });
+
+    test("every announcement within one load carries the same UUID", () => {
+        const uuids = announcedUuids();
+        expect(uuids.length).toBeGreaterThan(1);
+        expect(new Set(uuids).size).toBe(1);
+    });
+
+    test("two page loads announce different UUIDs", () => {
+        const first = announcedUuids()[0];
+        const second = announcedUuids()[0];
+        expect(first).toMatch(UUID_V4);
+        expect(second).toMatch(UUID_V4);
+        expect(second).not.toBe(first);
+    });
+});