fix: build hashes and recovery-phrase entropy come from ethers (closes #758)

build.js and script/lib/package.js hash with sha256 from ethers, with the
0x prefix stripped so the build receipt and SHA256SUMS keep bare lowercase
hex. generateMnemonic() takes its 16 bytes of entropy from randomBytes in
ethers. The README Crypto policy no longer lists these as exceptions.

Model: opus-5-5

README.md

@@ -264,6 +264,8 @@ The shared modules, each in one line:
   messaging, windows and the lock.
 - `buildInfo.js`: the version, license, author, commit and date compiled into
   About.
+- `calldataDecoder.js`: the ERC-20 `approve()` and `transfer()` decoder, which
+  hands other calldata to `uniswap.js`. Popup only.
 - `chainSwitch.js`: the popup's network switch.
 - `chainSwitchFields.js`: the fields a network switch changes.
 - `constants.js`: `DEBUG`, the default endpoints, the ERC-20 ABI and the burn
@@ -1187,17 +1189,20 @@ These helpers write one kind of value on every screen that shows it:
   times;
 - `renderAddressHtml()` in the same file: most addresses.
 
-Every screen shows token and ETH amounts the same way, through
-`truncateAmountNeverZero()` in `src/shared/amountDisplay.js`:
+Most screens show token and ETH amounts with four decimal places. History rows
+cut amounts to four decimals and never round up (`truncateAmount()` in
+`src/shared/amountDisplay.js`). The balance lists and Home's ETH balance round
+to four places. The screens that state what is being authorized cut as the
+history does, and extend an amount below 0.0001 to its first nonzero digit
+(`truncateAmountNeverZero()`). So a nonzero amount never reads as zero there.
+Those screens are:
 
-- an amount is cut to four decimal places, never rounded, so 0.99996 reads
-  `0.9999`;
-- an amount below 0.0001 is shown to its first nonzero digit, so 0.00004 reads
-  `0.00004`.
+- TxApproval;
+- SignApproval's Permit warning;
+- ConfirmTx, and Send's current balance;
+- WaitTx, SuccessTx and ErrorTx.
 
-So an amount never reads as more than it is, and a nonzero amount never reads as
-zero. TransactionDetail is the one exception: it shows the exact amount and its
-base units.
+TransactionDetail shows the exact amount and its base units.
 
 An amount to send is valid when it is a number above zero, written as digits
 with at most one decimal point. Nothing but zeros may follow the token's last
@@ -1376,7 +1381,7 @@ approval screens show a red warning.
 ### Transaction decoding
 
 TxApproval and TransactionDetail try to decode calldata into a summary
-(`decodeCalldata()` in `src/popup/views/approval.js`). SuccessTx repeats
+(`decodeCalldata()` in `src/shared/calldataDecoder.js`). SuccessTx repeats
 TxApproval's summary. Decoding is a display aid. When it fails, the raw calldata
 is shown in full. No contract gets any treatment beyond a legible confirmation
 screen.
@@ -1642,11 +1647,10 @@ The development dependencies ship nowhere:
 
 ### Crypto policy
 
-Hashing, key derivation, signing and encryption go through `ethers` or
-`libsodium-wrappers-sumo`. No primitive is implemented in this repository. A new
-recovery phrase draws its random bytes from the browser's
-`crypto.getRandomValues()`. The build tooling, `build.js` and `script/lib/`,
-hashes files with Node's `crypto`; none of it ships in the extension.
+In the extension, hashing, key derivation, signing and encryption go through
+`ethers` or `libsodium-wrappers-sumo`. A new recovery phrase takes its random
+bytes from `ethers`. `build.js` and `script/lib/package.js` also hash files with
+`ethers`. No primitive is implemented in this repository.
 
 ### Content Security Policy
 

build.js

@@ -1,8 +1,8 @@
 const fs = require("fs");
 const path = require("path");
-const crypto = require("crypto");
 const { execSync } = require("child_process");
 const esbuild = require("esbuild");
+const { sha256 } = require("ethers");
 const { resolveVersion } = require("./script/lib/version");
 const {
     BACKGROUND_ENTRY_PREFIX,
@@ -314,10 +314,8 @@ function copyIcons(distDir) {
 }
 
 function sha256File(absPath) {
-    return crypto
-        .createHash("sha256")
-        .update(fs.readFileSync(absPath))
-        .digest("hex");
+    // ethers prefixes the hex with 0x; the receipt holds bare hex.
+    return sha256(fs.readFileSync(absPath)).slice(2);
 }
 
 // Write the receipt for the files this build emitted. Deliberately records no

script/lib/package.js

@@ -25,9 +25,9 @@
 
 "use strict";
 
-const crypto = require("crypto");
 const fs = require("fs");
 const path = require("path");
+const ethers = require("ethers");
 
 const { readZip, writeZip } = require("./zip");
 const { resolveVersion } = require("./version");
@@ -60,8 +60,9 @@ function fail(message) {
     throw new Error(message);
 }
 
+// Lowercase hex without the 0x prefix ethers adds, as sha256sum prints it.
 function sha256(buf) {
-    return crypto.createHash("sha256").update(buf).digest("hex");
+    return ethers.sha256(buf).slice(2);
 }
 
 // Every regular file under dir, as archive-root-relative forward-slashed
@@ -291,4 +292,9 @@ if (require.main === module) {
     }
 }
 
-module.exports = { checkSelfContained, htmlReferences, manifestReferences };
+module.exports = {
+    checkSelfContained,
+    htmlReferences,
+    manifestReferences,
+    sha256,
+};

src/popup/views/addressToken.js

@@ -159,10 +159,10 @@ function renderBalance() {
     const addr =
         state.wallets[state.selectedWallet].addresses[state.selectedAddress];
     const tokenId = state.selectedToken;
-    let balance, price;
+    let amount, price;
     if (tokenId === "ETH") {
         // null when no refresh has read the balance.
-        balance = addr.balance;
+        amount = unknownableAmount(addr.balance);
         price = getPrice("ETH");
     } else {
         const id = tokenId.toLowerCase();
@@ -175,13 +175,12 @@ function renderBalance() {
         // null when the scale is unknown, or when no refresh has read the
         // token's balance: no quantity to show, and none to price.
         // balanceLine() states that rather than printing 0.0000.
-        if (tb) balance = tb.balance;
-        else balance = tracked && tracked.balanceNotFetched ? null : "0";
+        if (tb) amount = unknownableAmount(tb.balance);
+        else amount = tracked && tracked.balanceNotFetched ? null : 0;
         price = getPrice(tokenId);
     }
 
     // USD total for this token only
-    const amount = unknownableAmount(balance);
     const usdVal = price && amount !== null ? amount * price : null;
     const usdStr = formatUsd(usdVal);
     $("address-token-usd-total").innerHTML = escapeHtml(usdStr) || " ";
@@ -189,7 +188,7 @@ function renderBalance() {
     // Single token balance line (no tokenId — not clickable here)
     $("address-token-balance").innerHTML = balanceLine(
         currentSymbol,
-        balance,
+        amount,
         price,
     );
 }

src/popup/views/approval.js

@@ -12,9 +12,13 @@ const {
     formatFee,
     tokenLabel,
     blockscoutOffTokenNoteHtml,
-    tokenSourcesByChainId,
 } = require("./helpers");
-const { state, saveState, currentNetwork } = require("../../shared/state");
+const {
+    state,
+    saveState,
+    currentNetwork,
+    tokenSourcesByChainId,
+} = require("../../shared/state");
 const {
     networkById,
     networkByChainId,
@@ -26,21 +30,24 @@ const {
     getAddress,
     getBigInt,
     getBytes,
-    Interface,
     MaxUint256,
     toUtf8String,
 } = require("ethers");
 const { getPrice, formatUsd } = require("../../shared/prices");
-const { ERC20_ABI } = require("../../shared/constants");
 const { INVISIBLE_CHARACTERS } = require("../../shared/symbolSpoof");
 const {
     resolveTokenDecimals,
     resolveTokenSymbol,
     unknownDecimalsAmount,
 } = require("../../shared/approvalAmount");
+const {
+    decodeCalldata,
+    tokenAmountText,
+} = require("../../shared/calldataDecoder");
 // Four decimals, with the nonzero floor these screens hold: every amount this
 // view renders — the ERC-20 line, the ETH value, the max fee — and every one
-// it carries forward to the wait/success/error screens goes through it.
+// it carries forward to the wait/success/error screens goes through it. The
+// ERC-20 line gets it from tokenAmountText().
 const {
     truncateAmountNeverZero: formatTxValue,
 } = require("../../shared/amountDisplay");
@@ -54,11 +61,8 @@ const {
     typedDataChainRefusal,
 } = require("../../shared/approvalVerify");
 const txStatus = require("./txStatus");
-const uniswap = require("../../shared/uniswap");
 const { runtimeApi, sendMessage } = require("../../shared/browserApi");
 
-const erc20Iface = new Interface(ERC20_ABI);
-
 // The link opens the explorer of the network with `chainId`, or of the active
 // network when none is given. A chain id that names no network has no
 // explorer, so the address is drawn without a link.
@@ -70,141 +74,6 @@ function approvalAddressHtml(address, chainId) {
     return renderAddressHtml(address, { title, chainId });
 }
 
-// The amount line for a decoded ERC-20 call. With a known scale it is the
-// token quantity; with `decimals` null it is the base-unit integer with the
-// unknown scale stated, because formatting it with an assumed scale is what
-// showed a 5,000-token transfer as `0.0000`. `raw` is what the status screens
-// carry, `display` is what the approval screen shows.
-function tokenAmountText(rawAmount, decimals, symbol) {
-    if (decimals === null) {
-        const unknown = unknownDecimalsAmount(rawAmount);
-        return { raw: unknown, display: unknown };
-    }
-    const formatted = formatTxValue(formatUnits(rawAmount, decimals));
-    return {
-        raw: formatted,
-        display: formatted + (symbol ? " " + symbol : ""),
-    };
-}
-
-// Try to decode calldata sent from `fromAddress` to `toAddress` on the network
-// with chain id `chainId`, using known ABIs.
-// Returns { name, description, details } or null.
-function decodeCalldata(data, toAddress, chainId, fromAddress) {
-    if (!data || data === "0x" || data.length < 10) return null;
-
-    // Where a token's name and scale are looked for, for every decoder below:
-    // what the wallet knows of the tokens on the network with `chainId`, which
-    // need not be the active one. The ERC-20 amount line and the swap's Amount
-    // and Min. received lines resolve the scale the same way, and refuse to
-    // format the same way when it is nowhere.
-    const decimalsSources = tokenSourcesByChainId(chainId);
-
-    // Try ERC-20 (approve / transfer)
-    try {
-        const parsed = erc20Iface.parseTransaction({ data });
-        if (parsed) {
-            const tokenSymbol = resolveTokenSymbol(toAddress, decimalsSources);
-            // null when no source knows this token's scale. It is not
-            // defaulted to 18: an amount formatted with a guessed scale is
-            // the wrong number, and for a token with fewer decimals than the
-            // guess it is the wrong number in the direction that reads as
-            // zero. See tokenAmountText().
-            const tokenDecimals = resolveTokenDecimals(
-                toAddress,
-                decimalsSources,
-            );
-            const contractLabel = tokenSymbol
-                ? tokenSymbol + " (" + toAddress + ")"
-                : toAddress;
-
-            if (parsed.name === "approve") {
-                const spender = parsed.args[0];
-                const rawAmount = parsed.args[1];
-                const maxUint = BigInt(
-                    "0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
-                );
-                const isUnlimited = rawAmount === maxUint;
-                // An unbounded allowance needs no scale to describe, so it is
-                // still named rather than refused.
-                const amount = isUnlimited
-                    ? { raw: "Unlimited", display: "Unlimited" }
-                    : tokenAmountText(rawAmount, tokenDecimals, tokenSymbol);
-
-                return {
-                    name: "Token Approval",
-                    description: tokenSymbol
-                        ? "Approve spending of your " + tokenSymbol
-                        : "Approve spending of an ERC-20 token",
-                    details: [
-                        {
-                            label: "Token",
-                            value: contractLabel,
-                            address: toAddress,
-                            isToken: true,
-                        },
-                        {
-                            label: "Spender",
-                            value: spender,
-                            address: spender,
-                        },
-                        {
-                            label: "Amount",
-                            value: amount.display,
-                            rawValue: amount.raw,
-                        },
-                    ],
-                };
-            }
-
-            if (parsed.name === "transfer") {
-                const to = parsed.args[0];
-                const rawAmount = parsed.args[1];
-                const amount = tokenAmountText(
-                    rawAmount,
-                    tokenDecimals,
-                    tokenSymbol,
-                );
-
-                return {
-                    name: "Token Transfer",
-                    description: tokenSymbol
-                        ? "Transfer " + tokenSymbol
-                        : "Transfer ERC-20 token",
-                    details: [
-                        {
-                            label: "Token",
-                            value: contractLabel,
-                            address: toAddress,
-                            isToken: true,
-                        },
-                        { label: "Recipient", value: to, address: to },
-                        {
-                            label: "Amount",
-                            value: amount.display,
-                            rawValue: amount.raw,
-                        },
-                    ],
-                };
-            }
-        }
-    } catch {
-        // Not ERC-20 — fall through
-    }
-
-    // Try Uniswap Universal Router
-    const routerResult = uniswap.decode(
-        data,
-        toAddress,
-        chainId,
-        decimalsSources,
-        fromAddress,
-    );
-    if (routerResult) return routerResult;
-
-    return null;
-}
-
 function showPhishingWarning(elementId, isPhishing) {
     const el = $(elementId);
     if (!el) return;
@@ -1298,7 +1167,6 @@ function init(_ctx) {
 module.exports = {
     init,
     show,
-    decodeCalldata,
     formatTypedDataHtml,
     typedDataRefusal,
 };

src/popup/views/helpers.js

@@ -31,7 +31,12 @@ const { escapeHtml } = require("../../shared/html");
 const { isDebug } = require("../../shared/log");
 const { networkByChainId } = require("../../shared/networks");
 const { formatUsd, getPrice } = require("../../shared/prices");
-const { state, saveState, currentNetwork } = require("../../shared/state");
+const {
+    state,
+    saveState,
+    currentNetwork,
+    tokenSourcesByChainId,
+} = require("../../shared/state");
 const { displaySymbol } = require("../../shared/symbolDisplay");
 const { isSpoofedSymbol } = require("../../shared/symbolSpoof");
 const { walletHasRecoveryPhrase } = require("../../shared/wallet");
@@ -305,32 +310,6 @@ function nativeCurrency() {
     return currentNetwork().nativeCurrency;
 }
 
-// What the wallet knows of the tokens on the network with this chain id, or
-// on the active network when no chain id is given, as the `sources` that
-// resolveTokenSymbol() and resolveTokenDecimals() take. A contract address
-// names a token on one network only, and every token balance held is the
-// active network's, so another network gets the tokens tracked on it
-// (state.networkTrackedTokens, see applyChainSwitchFields()) and no balances.
-//
-// The wallets' balances hold what Blockscout reported for each token. So the
-// wallets are returned only while "Use Blockscout" is on.
-function tokenSourcesByChainId(chainId) {
-    const chainIdOrActive = chainId || currentNetwork().chainId;
-    const net = networkByChainId(chainIdOrActive);
-    if (net && net.id === state.networkId) {
-        return {
-            chainId: chainIdOrActive,
-            trackedTokens: state.trackedTokens,
-            wallets: state.useBlockscout ? state.wallets : [],
-        };
-    }
-    return {
-        chainId: chainIdOrActive,
-        trackedTokens: (net && state.networkTrackedTokens[net.id]) || [],
-        wallets: [],
-    };
-}
-
 // The line shown under a token while "Use Blockscout" is off. The token gets
 // the line only when the bundled list and the tracked tokens lack its name or
 // decimals. Otherwise this returns "". The token is a contract address on the
@@ -394,16 +373,13 @@ function formatFee(wei, symbol, chainId) {
 // the row that issue #307 was reported against: every screen that lists a
 // holding renders through here.
 //
-// `balance` is the stored balance, a decimal string. It is null for a holding
-// whose scale nothing knows
+// `amount` is null for a holding whose scale nothing knows
 // (https://git.eeqj.de/sneak/AutistMask/issues/349), and for a balance no
 // refresh has read. There is no quantity to print for it and no fiat value to
 // derive from one, and printing 0.0000 for a real holding is the failure this
 // whole rule exists to prevent, so the row says so instead.
-function balanceLine(symbol, balance, price, tokenId) {
-    const amount = unknownableAmount(balance);
-    const qty =
-        amount === null ? "quantity unknown" : truncateAmountNeverZero(balance);
+function balanceLine(symbol, amount, price, tokenId) {
+    const qty = amount === null ? "quantity unknown" : amount.toFixed(4);
     const usd =
         price && amount !== null
             ? escapeHtml(formatUsd(amount * price)) || " "
@@ -418,7 +394,7 @@ function balanceLine(symbol, balance, price, tokenId) {
         `<div class="flex text-xs${clickClass}"${tokenAttr}>` +
         `<span class="flex justify-between w-[42ch] max-w-full">` +
         `<span>${escapeHtml(displaySymbol(symbol))}</span>` +
-        `<span>${escapeHtml(qty)}</span>` +
+        `<span>${qty}</span>` +
         `</span>` +
         `<span class="text-right text-muted flex-1">${usd}</span>` +
         `</div>`
@@ -444,7 +420,7 @@ function markTrackedTokensNotFetched() {
 function balanceLinesForAddress(addr, trackedTokens, showZero) {
     let html = balanceLine(
         nativeCurrency(),
-        addr.balance,
+        unknownableAmount(addr.balance),
         getPrice("ETH"),
         "ETH",
     );
@@ -462,7 +438,7 @@ function balanceLinesForAddress(addr, trackedTokens, showZero) {
         if (bal === 0 && !showZero) continue;
         html += balanceLine(
             t.symbol,
-            t.balance,
+            bal,
             getPrice(t.address),
             t.address.toLowerCase(),
         );
@@ -480,7 +456,7 @@ function balanceLinesForAddress(addr, trackedTokens, showZero) {
             }
             html += balanceLine(
                 t.symbol,
-                t.balanceNotFetched ? null : "0",
+                t.balanceNotFetched ? null : 0,
                 getPrice(t.address),
                 t.address.toLowerCase(),
             );
@@ -491,8 +467,10 @@ function balanceLinesForAddress(addr, trackedTokens, showZero) {
 
 // Whether an address holds anything at all: ETH or any ERC-20 the wallet
 // knows about, except a token holding below 0.000001, which the balance list
-// under the remove-address warning leaves out too. Callers that warn about
-// holdings must ask this, not the rendered lines.
+// under the remove-address warning leaves out too. Deliberately unrounded —
+// the rendered lines round to four decimals, so a dust balance displays as
+// 0.0000 while still being real money at a real address. Callers that warn
+// about holdings must ask this, not the rendered figure.
 function addressHoldsFunds(addr) {
     if (!addr) return false;
     // A null or absent ETH balance reads as unknown, so the address may hold
@@ -867,7 +845,6 @@ module.exports = {
     keyMaterialName,
     unknownableAmount,
     nativeCurrency,
-    tokenSourcesByChainId,
     blockscoutOffTokenNoteHtml,
     tokenLabel,
     formatFee,

src/popup/views/home.js

@@ -31,7 +31,6 @@ const {
     resetSendValidation,
 } = require("./send");
 const { deriveAddressFromXpub } = require("../../shared/wallet");
-const { truncateAmountNeverZero } = require("../../shared/amountDisplay");
 const { canRemoveAddress } = require("../../shared/walletDelete");
 const {
     walletDefect,
@@ -82,8 +81,7 @@ function renderTotalValue() {
     if (ethBal === null) {
         el.textContent = "unknown (" + nativeCurrency() + ")";
     } else {
-        const ethStr =
-            truncateAmountNeverZero(addr.balance) + " " + nativeCurrency();
+        const ethStr = ethBal.toFixed(4) + " " + nativeCurrency();
         const ethUsd = ethPrice
             ? " (" + formatUsd(ethBal * ethPrice) + ")"
             : "";

src/popup/views/send.js

@@ -10,9 +10,13 @@ const {
     renderAddressHtml,
     attachCopyHandlers,
     goBack,
-    tokenSourcesByChainId,
 } = require("./helpers");
-const { state, currentAddress, currentNetwork } = require("../../shared/state");
+const {
+    state,
+    currentAddress,
+    currentNetwork,
+    tokenSourcesByChainId,
+} = require("../../shared/state");
 let ctx;
 const { getProvider } = require("../../shared/balances");
 const { resolveTokenDecimals } = require("../../shared/approvalAmount");

src/popup/views/transactionDetail.js

@@ -27,7 +27,7 @@ const { nativeCurrencyByChainId } = require("../../shared/networks");
 const { formatEther, formatUnits } = require("ethers");
 const { log, debugFetch } = require("../../shared/log");
 const { storedSettingIsOn } = require("../../shared/storedSettings");
-const { decodeCalldata } = require("./approval");
+const { decodeCalldata } = require("../../shared/calldataDecoder");
 
 /**
  * Determine a human-readable transaction type string from tx fields.

src/shared/amountDisplay.js

@@ -1,6 +1,15 @@
-// The amount rule from README.md's Amounts section. Every screen that shows a
-// token or ETH amount, except TransactionDetail, shows it through
-// truncateAmountNeverZero(), so one value reads the same on every screen.
+// The 4-decimal amount rule from README.md's Amounts section, and
+// the one exception to it, in one place. Three call sites had grown their own
+// copy of the truncation — the history and balance lists
+// (`src/shared/transactions.js`), the approval screen's ERC-20 amount line
+// (`src/shared/calldataDecoder.js`) and its Uniswap swap detail lines
+// (`src/shared/uniswap.js`) — and a fix applied to one of them left the other
+// two showing a different number for the same value.
+//
+// The two truncation functions below are the two policies, not two
+// implementations of one: summary lists truncate, and the screens that state
+// what is being authorized truncate with a floor. Keeping them adjacent is the
+// point, so a change to the rule cannot reach one screen and miss another.
 
 // Truncate to exactly four decimal places. Truncation, never rounding: an
 // amount must never be displayed as larger than it is, so 0.99999 stays
@@ -11,13 +20,12 @@ function truncateAmount(val) {
     return parts[0] + "." + (parts[1] + "0000").slice(0, 4);
 }
 
-// Four decimal places, truncated, and a nonzero amount never renders as zero.
-// Truncating alone would show an amount below 0.0001 as 0.0000, and a real
-// holding, transfer or allowance would then read as nothing.
-//
-// `val` is the exact decimal string: a stored balance, or what formatEther()
-// or formatUnits() returns. Never a JavaScript number, whose own rounding
-// would happen before the truncation.
+// The same rule, plus the invariant the approval and confirmation screens
+// hold: a nonzero amount never renders as zero. Truncating to four decimals
+// does exactly that to an amount below 0.0001 — one base unit of an 18-decimal
+// token, 500 of an 8-decimal one — and a real transfer or allowance then reads
+// as "nothing is being moved" on the screen whose whole job is to say what is
+// being authorized.
 //
 // When the truncated string carries no significant digit and the value does,
 // the amount is extended to its first significant digit instead. It stays in
@@ -46,6 +54,7 @@ function isBelowOneMillionth(balance) {
 }
 
 module.exports = {
+    truncateAmount,
     truncateAmountNeverZero,
     isBelowOneMillionth,
 };

src/shared/calldataDecoder.js

@@ -0,0 +1,155 @@
+// Decode a transaction's calldata into the summary that TxApproval and
+// TransactionDetail show: ERC-20 `approve` and `transfer` calls here, and
+// Uniswap Universal Router calls through uniswap.js. The summary is data; the
+// views turn its addresses into HTML.
+
+const { formatUnits, Interface } = require("ethers");
+const { ERC20_ABI } = require("./constants");
+const { tokenSourcesByChainId } = require("./state");
+const {
+    resolveTokenDecimals,
+    resolveTokenSymbol,
+    unknownDecimalsAmount,
+} = require("./approvalAmount");
+// Four decimals, with the nonzero floor the approval screens hold.
+const { truncateAmountNeverZero } = require("./amountDisplay");
+const uniswap = require("./uniswap");
+
+const erc20Iface = new Interface(ERC20_ABI);
+
+// The amount line for a decoded ERC-20 call. With a known scale it is the
+// token quantity; with `decimals` null it is the base-unit integer with the
+// unknown scale stated, because formatting it with an assumed scale is what
+// showed a 5,000-token transfer as `0.0000`. `raw` is what the status screens
+// carry, `display` is what the approval screen shows.
+function tokenAmountText(rawAmount, decimals, symbol) {
+    if (decimals === null) {
+        const unknown = unknownDecimalsAmount(rawAmount);
+        return { raw: unknown, display: unknown };
+    }
+    const formatted = truncateAmountNeverZero(formatUnits(rawAmount, decimals));
+    return {
+        raw: formatted,
+        display: formatted + (symbol ? " " + symbol : ""),
+    };
+}
+
+// Try to decode calldata sent from `fromAddress` to `toAddress` on the network
+// with chain id `chainId`, using known ABIs.
+// Returns { name, description, details } or null.
+function decodeCalldata(data, toAddress, chainId, fromAddress) {
+    if (!data || data === "0x" || data.length < 10) return null;
+
+    // Where a token's name and scale are looked for, for every decoder below:
+    // what the wallet knows of the tokens on the network with `chainId`, which
+    // need not be the active one. The ERC-20 amount line and the swap's Amount
+    // and Min. received lines resolve the scale the same way, and refuse to
+    // format the same way when it is nowhere.
+    const decimalsSources = tokenSourcesByChainId(chainId);
+
+    // Try ERC-20 (approve / transfer)
+    try {
+        const parsed = erc20Iface.parseTransaction({ data });
+        if (parsed) {
+            const tokenSymbol = resolveTokenSymbol(toAddress, decimalsSources);
+            // null when no source knows this token's scale. It is not
+            // defaulted to 18: an amount formatted with a guessed scale is
+            // the wrong number, and for a token with fewer decimals than the
+            // guess it is the wrong number in the direction that reads as
+            // zero. See tokenAmountText().
+            const tokenDecimals = resolveTokenDecimals(
+                toAddress,
+                decimalsSources,
+            );
+            const contractLabel = tokenSymbol
+                ? tokenSymbol + " (" + toAddress + ")"
+                : toAddress;
+
+            if (parsed.name === "approve") {
+                const spender = parsed.args[0];
+                const rawAmount = parsed.args[1];
+                const maxUint = BigInt(
+                    "0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+                );
+                const isUnlimited = rawAmount === maxUint;
+                // An unbounded allowance needs no scale to describe, so it is
+                // still named rather than refused.
+                const amount = isUnlimited
+                    ? { raw: "Unlimited", display: "Unlimited" }
+                    : tokenAmountText(rawAmount, tokenDecimals, tokenSymbol);
+
+                return {
+                    name: "Token Approval",
+                    description: tokenSymbol
+                        ? "Approve spending of your " + tokenSymbol
+                        : "Approve spending of an ERC-20 token",
+                    details: [
+                        {
+                            label: "Token",
+                            value: contractLabel,
+                            address: toAddress,
+                            isToken: true,
+                        },
+                        {
+                            label: "Spender",
+                            value: spender,
+                            address: spender,
+                        },
+                        {
+                            label: "Amount",
+                            value: amount.display,
+                            rawValue: amount.raw,
+                        },
+                    ],
+                };
+            }
+
+            if (parsed.name === "transfer") {
+                const to = parsed.args[0];
+                const rawAmount = parsed.args[1];
+                const amount = tokenAmountText(
+                    rawAmount,
+                    tokenDecimals,
+                    tokenSymbol,
+                );
+
+                return {
+                    name: "Token Transfer",
+                    description: tokenSymbol
+                        ? "Transfer " + tokenSymbol
+                        : "Transfer ERC-20 token",
+                    details: [
+                        {
+                            label: "Token",
+                            value: contractLabel,
+                            address: toAddress,
+                            isToken: true,
+                        },
+                        { label: "Recipient", value: to, address: to },
+                        {
+                            label: "Amount",
+                            value: amount.display,
+                            rawValue: amount.raw,
+                        },
+                    ],
+                };
+            }
+        }
+    } catch {
+        // Not ERC-20 — fall through
+    }
+
+    // Try Uniswap Universal Router
+    const routerResult = uniswap.decode(
+        data,
+        toAddress,
+        chainId,
+        decimalsSources,
+        fromAddress,
+    );
+    if (routerResult) return routerResult;
+
+    return null;
+}
+
+module.exports = { decodeCalldata, tokenAmountText };

src/shared/state.js

@@ -22,7 +22,7 @@
 // same thing in the editor is fast feedback in front of the build, not the
 // guarantee.
 
-const { networkById } = require("./networks");
+const { networkById, networkByChainId } = require("./networks");
 const { copyChainSwitchFields } = require("./chainSwitchFields");
 const {
     DEFAULT_STATE,
@@ -125,6 +125,32 @@ function currentNetwork() {
     return networkById(state.networkId);
 }
 
+// What the wallet knows of the tokens on the network with this chain id, or
+// on the active network when no chain id is given, as the `sources` that
+// resolveTokenSymbol() and resolveTokenDecimals() take. A contract address
+// names a token on one network only, and every token balance held is the
+// active network's, so another network gets the tokens tracked on it
+// (state.networkTrackedTokens, see applyChainSwitchFields()) and no balances.
+//
+// The wallets' balances hold what Blockscout reported for each token. So the
+// wallets are returned only while "Use Blockscout" is on.
+function tokenSourcesByChainId(chainId) {
+    const chainIdOrActive = chainId || currentNetwork().chainId;
+    const net = networkByChainId(chainIdOrActive);
+    if (net && net.id === state.networkId) {
+        return {
+            chainId: chainIdOrActive,
+            trackedTokens: state.trackedTokens,
+            wallets: state.useBlockscout ? state.wallets : [],
+        };
+    }
+    return {
+        chainId: chainIdOrActive,
+        trackedTokens: (net && state.networkTrackedTokens[net.id]) || [],
+        wallets: [],
+    };
+}
+
 // `baseline` holds the persisted fields as this page held them when its last
 // loadState() finished, or when its last successful saveState() began.
 // takeStoredNetwork(), takeStoredTrackedTokens() and
@@ -820,5 +846,6 @@ module.exports = {
     loadState,
     currentAddress,
     currentNetwork,
+    tokenSourcesByChainId,
     StateNotLoadedError,
 };

src/shared/transactions.js

@@ -16,7 +16,10 @@ const { nativeCurrencyByChainId } = require("./networks");
 // a scale is either reported or it is unknown, and "unknown" must mean the
 // same thing here as it does on the screens that refuse to format one.
 const { toDecimals } = require("./transferAmount");
-const { truncateAmountNeverZero } = require("./amountDisplay");
+// The plain 4-decimal rule. The history and balance lists deliberately keep
+// truncation without the approval screens' nonzero floor: the transaction
+// detail view is the authoritative record and already shows exact precision.
+const { truncateAmount: formatTxValue } = require("./amountDisplay");
 const { routerRelease } = require("./uniswap");
 const { storedSettingIsOn } = require("./storedSettings");
 
@@ -37,7 +40,7 @@ function parseTx(tx, addrLower, chainId) {
 
     // For contract calls, produce a meaningful label instead of "0.0000 ETH"
     let symbol = nativeCurrencyByChainId(chainId);
-    let value = truncateAmountNeverZero(formatEther(rawWei));
+    let value = formatTxValue(formatEther(rawWei));
     let exactValue = formatEther(rawWei);
     let rawAmount = rawWei;
     let rawUnit = "wei";
@@ -119,9 +122,7 @@ function parseTokenTransfer(tt, addrLower, chainId) {
     // The exact figure is not lost — it is the base-unit line below, which is
     // the one number that needs no scale to be true.
     const formatted =
-        decimals === null
-            ? ""
-            : truncateAmountNeverZero(formatUnits(rawVal, decimals));
+        decimals === null ? "" : formatTxValue(formatUnits(rawVal, decimals));
     const exact = decimals === null ? "" : formatUnits(rawVal, decimals);
     return {
         hash: tt.transaction_hash,

src/shared/wallet.js

@@ -1,7 +1,7 @@
 // Wallet operations: mnemonic generation, HD derivation, signing.
 // All crypto delegated to ethers.js.
 
-const { Mnemonic, HDNodeWallet, Wallet } = require("ethers");
+const { Mnemonic, HDNodeWallet, Wallet, randomBytes } = require("ethers");
 const { DEBUG, DEBUG_MNEMONIC, BIP44_ETH_PATH } = require("./constants");
 
 function generateMnemonic() {
@@ -10,10 +10,7 @@ function generateMnemonic() {
     // settings toggle drives, which would let a user of a release build turn
     // the hardcoded, publicly known test phrase back on for real wallets.
     if (DEBUG) return DEBUG_MNEMONIC;
-    const m = Mnemonic.fromEntropy(
-        globalThis.crypto.getRandomValues(new Uint8Array(16)),
-    );
-    return m.phrase;
+    return Mnemonic.fromEntropy(randomBytes(16)).phrase;
 }
 
 // Every extended key (xprv or xpub) entering the app goes through this.

tests/approvalAmount.test.js

@@ -23,7 +23,7 @@ const {
     resolveTokenDecimals,
     unknownDecimalsAmount,
 } = require("../src/shared/approvalAmount");
-const { decodeCalldata } = require("../src/popup/views/approval");
+const { decodeCalldata } = require("../src/shared/calldataDecoder");
 
 const iface = new Interface(ERC20_ABI);
 

tests/approvalDisplayFloor.test.js

@@ -13,7 +13,7 @@
 // asserted on `rawValue` alongside the displayed line.
 //
 // Both amount paths of that screen are covered: the ERC-20 line decoded by
-// `src/popup/views/approval.js`, and the swap's `Amount` and `Min. received`
+// `src/shared/calldataDecoder.js`, and the swap's `Amount` and `Min. received`
 // lines decoded by `src/shared/uniswap.js`.
 
 globalThis.chrome = {
@@ -23,9 +23,12 @@ globalThis.chrome = {
 const { AbiCoder, Interface } = require("ethers");
 const { ERC20_ABI } = require("../src/shared/constants");
 const { state } = require("../src/shared/state");
-const { decodeCalldata } = require("../src/popup/views/approval");
+const { decodeCalldata } = require("../src/shared/calldataDecoder");
 const uniswap = require("../src/shared/uniswap");
-const { truncateAmountNeverZero } = require("../src/shared/amountDisplay");
+const {
+    truncateAmount,
+    truncateAmountNeverZero,
+} = require("../src/shared/amountDisplay");
 
 const iface = new Interface(ERC20_ABI);
 
@@ -181,7 +184,12 @@ describe("the four-decimal rule is otherwise unchanged", () => {
         expect(amount(transferData(0n), DAI).rawValue).toBe("0.0000");
     });
 
-    test("one base unit of an 18-decimal token reads as itself", () => {
+    // The three truncators now share one module. The floor is a policy of the
+    // approval and confirmation screens only: the history and balance lists
+    // keep plain truncation, because the transaction detail view is the
+    // authoritative record and already shows exact precision.
+    test("the list rule stays unfloored", () => {
+        expect(truncateAmount("0.000000000000000001")).toBe("0.0000");
         expect(truncateAmountNeverZero("0.000000000000000001")).toBe(
             "0.000000000000000001",
         );

tests/balanceLineEscaping.test.js

@@ -41,13 +41,13 @@ describe("balanceLine", () => {
         // this payload before its id attribute, so an assertion about the
         // rest of the payload would pass on the cap and say nothing about
         // the escape.
-        const html = balanceLine(HOSTILE_SYMBOL, "1", null, null);
+        const html = balanceLine(HOSTILE_SYMBOL, 1, null, null);
         expect(html).not.toContain("<iframe");
         expect(html).toContain("&lt;iframe");
     });
 
     test("caps the symbol before rendering it", () => {
-        const html = balanceLine("A".repeat(4096), "1", null, null);
+        const html = balanceLine("A".repeat(4096), 1, null, null);
         expect(html).toContain("A".repeat(MAX_SYMBOL_LENGTH - 1) + "…");
         expect(html).not.toContain("A".repeat(MAX_SYMBOL_LENGTH + 1));
     });
@@ -55,13 +55,13 @@ describe("balanceLine", () => {
     // The token id lands inside data-token="...", so a quote in it is a
     // way out of the attribute and into a new one.
     test("keeps a quote-bearing token id inside its attribute", () => {
-        const html = balanceLine("TKN", "1", null, '" onclick="alert(1)');
+        const html = balanceLine("TKN", 1, null, '" onclick="alert(1)');
         expect(html).not.toContain('onclick="');
         expect(html).toContain('data-token="&quot; onclick=&quot;alert(1)"');
     });
 
     test("renders an ordinary holding unchanged", () => {
-        const html = balanceLine("USDC", "1.5", null, "0xabc");
+        const html = balanceLine("USDC", 1.5, null, "0xabc");
         expect(html).toContain("<span>USDC</span>");
         expect(html).toContain("<span>1.5000</span>");
         expect(html).toContain('data-token="0xabc"');
@@ -69,7 +69,7 @@ describe("balanceLine", () => {
 
     // formatUsd() writes a value under a cent as "< $0.01".
     test("escapes the USD value along with the symbol", () => {
-        const html = balanceLine("USDC", "0.001", 1, null);
+        const html = balanceLine("USDC", 0.001, 1, null);
         expect(html).toContain("&lt; $0.01");
         expect(html).not.toContain("< $0.01");
     });

tests/balanceTruncation.test.js

@@ -1,78 +0,0 @@
-// The balance lists and Home's ETH line show a balance as Send does (README.md,
-// Amounts): cut to four decimal places, never rounded up, and a nonzero amount
-// never shown as zero
-// (https://git.eeqj.de/sneak/AutistMask/issues/757).
-//
-// Driven through the real popup over a stored profile on Ethereum Mainnet.
-
-const {
-    ADDRESS,
-    bootPopup,
-    cleanupPopup,
-    unversionedValidProfile,
-} = require("./support/popupBoot");
-const { balanceLine } = require("../src/popup/views/helpers");
-
-const USDC = "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48";
-
-afterEach(() => {
-    cleanupPopup();
-});
-
-// The quantity cell of a balance row.
-function quantity(row) {
-    return row.match(/<span>([^<]*)<\/span><\/span>/)[1];
-}
-
-// The popup on Home over one address holding `eth` ETH and `usdc` USDC.
-function bootHolding(eth, usdc) {
-    const profile = unversionedValidProfile({
-        trackedTokens: [{ address: USDC, symbol: "USDC", decimals: 6 }],
-    });
-    profile.wallets[0].addresses[0] = {
-        address: ADDRESS,
-        balance: eth,
-        tokenBalances: [
-            { address: USDC, symbol: "USDC", decimals: 6, balance: usdc },
-        ],
-    };
-    return bootPopup(profile);
-}
-
-// The balance row for `token` in Home's wallet list.
-function homeRow(page, token) {
-    return page
-        .node("wallet-list")
-        .innerHTML.split("<div ")
-        .find((row) => row.includes('data-token="' + token + '"'));
-}
-
-describe("balanceLine", () => {
-    test("cuts 0.99996 to 0.9999, never rounding it up to 1.0000", () => {
-        expect(quantity(balanceLine("ETH", "0.99996", null, "ETH"))).toBe(
-            "0.9999",
-        );
-    });
-
-    test("shows 0.00004 as 0.00004, not 0.0000", () => {
-        expect(quantity(balanceLine("USDC", "0.00004", null, USDC))).toBe(
-            "0.00004",
-        );
-    });
-});
-
-describe("Home", () => {
-    test("the ETH line and the balance list read 0.99996 ETH as 0.9999", async () => {
-        const page = await bootHolding("0.99996", "0.00004");
-
-        expect(page.visibleViews()).toEqual(["main"]);
-        expect(page.text("total-value")).toBe("0.9999 ETH");
-        expect(quantity(homeRow(page, "ETH"))).toBe("0.9999");
-    });
-
-    test("the balance list reads 0.00004 USDC as 0.00004", async () => {
-        const page = await bootHolding("0.99996", "0.00004");
-
-        expect(quantity(homeRow(page, USDC.toLowerCase()))).toBe("0.00004");
-    });
-});

tests/deleteAddress.test.js

@@ -4,8 +4,8 @@
 // the copy is the substance and is tested as such. Two things it must not
 // get wrong: what it takes to get the address back — the app refuses both
 // obvious routes — and what counts as holding something, which is any
-// ERC-20 as well as ETH, at any size, including a balance below the four
-// decimals the balance lines render. The DOM behaviour
+// ERC-20 as well as ETH, at any size, including a balance that rounds to
+// zero at the four decimals the balance lines render. The DOM behaviour
 // around them is driven against the real popup by tests/e2e/run.js.
 
 // helpers.js pulls in state.js, which reads chrome.storage.local at load.
@@ -102,7 +102,7 @@ describe("whether an address holds anything", () => {
         expect(addressHoldsFunds(TOKEN_ONLY)).toBe(true);
     });
 
-    // 0.00001 ETH is below four decimals. It is still money.
+    // 0.00001 ETH renders as "0.0000" at four decimals. It is still money.
     test("an ETH balance below the displayed precision counts", () => {
         expect(addressHoldsFunds(DUST)).toBe(true);
     });
@@ -141,12 +141,13 @@ describe("the balance warning on the removal confirmation", () => {
         expect(html).toContain("2500.0000");
     });
 
-    // The rendered line shows the balance to its first nonzero digit, as Home
-    // and AddressDetail do (README.md, Amounts).
-    test("an ETH balance below 0.0001 is warned about, and reads as itself", () => {
+    // The rendered line says 0.0000 for this address — that is the display
+    // format, shared with Home and AddressDetail — and the warning is shown
+    // all the same, because the balance is not zero.
+    test("an ETH balance that renders as 0.0000 is warned about", () => {
         const html = balanceWarningHtml(DUST);
         expect(html).toContain("This address holds a balance.");
-        expect(html).toContain("<span>0.00001</span>");
+        expect(html).toContain("<span>0.0000</span>");
     });
 
     test("an ETH balance no refresh has read is warned about, and reads as unknown", () => {

tests/fabricatedDecimals.test.js

@@ -47,7 +47,7 @@ const { fetchTokenBalances } = require("../src/shared/balances");
 const { debugFetch } = require("../src/shared/log");
 const { state } = require("../src/shared/state");
 const { unknownDecimalsAmount } = require("../src/shared/approvalAmount");
-const { decodeCalldata } = require("../src/popup/views/approval");
+const { decodeCalldata } = require("../src/shared/calldataDecoder");
 const { TOKEN_BY_ADDRESS } = require("../src/shared/tokenList");
 
 const HOLDER = "0x" + "a".repeat(40);

tests/packaging.test.js

@@ -1,4 +1,5 @@
-// The release archives: the zip container, and the self-containment rule.
+// The release archives: the zip container, the self-containment rule, and the
+// digest format in release/SHA256SUMS.
 //
 // script/package produces one archive per browser and script/lib/package.js
 // decides what goes in it. The trap that rule exists for is real and specific:
@@ -11,12 +12,14 @@
 // So the packager resolves every reference in the manifest and in every HTML
 // document, and fails on any that leaves the extension root. These are the
 // cases for that, plus the archive format itself — new code, and the thing the
-// artifact is made of.
+// artifact is made of. One more case checks the digest format in
+// release/SHA256SUMS.
 
 const {
     checkSelfContained,
     htmlReferences,
     manifestReferences,
+    sha256,
 } = require("../script/lib/package");
 const { readZip, writeZip } = require("../script/lib/zip");
 
@@ -142,6 +145,14 @@ describe("archive self-containment", () => {
     });
 });
 
+// release/SHA256SUMS is checked with `sha256sum -c`, which needs the digest
+// as bare lowercase hex. The expected value is the FIPS 180-2 digest of "abc".
+test("sha256 prints the digest as sha256sum does", () => {
+    expect(sha256(Buffer.from("abc"))).toBe(
+        "ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad",
+    );
+});
+
 describe("the zip container", () => {
     const files = [
         { name: "manifest.json", data: Buffer.from('{"a":1}') },

tests/resolveTokenSymbol.test.js

@@ -22,7 +22,7 @@ const { Interface } = require("ethers");
 const { ERC20_ABI } = require("../src/shared/constants");
 const { state } = require("../src/shared/state");
 const { resolveTokenSymbol } = require("../src/shared/approvalAmount");
-const { decodeCalldata } = require("../src/popup/views/approval");
+const { decodeCalldata } = require("../src/shared/calldataDecoder");
 
 const iface = new Interface(ERC20_ABI);
 

tests/transactions.test.js

@@ -1361,31 +1361,6 @@ describe("fetchRecentTransactions merge and dedup", () => {
         expect(txs[0].holders).toBe(3500000);
     });
 
-    // README.md, Amounts: a nonzero amount never reads as zero.
-    test("a token transfer below 0.0001 shows its first nonzero digit", async () => {
-        respondWith(
-            [],
-            [
-                {
-                    transaction_hash: "0x" + "4".repeat(64),
-                    block_number: 21000040,
-                    timestamp: TS,
-                    from: { hash: ORDINARY_PEER },
-                    to: { hash: VICTIM },
-                    total: { value: "40", decimals: "6" },
-                    token: {
-                        symbol: "USDC",
-                        address_hash: USDC_CONTRACT,
-                        holders_count: "3500000",
-                    },
-                },
-            ],
-        );
-
-        const txs = await fetchRecentTransactions(VICTIM, BLOCKSCOUT, "0x1");
-        expect(txs[0].value).toBe("0.00004");
-    });
-
     test("two transfers of the same token in one transaction collapse to one entry", async () => {
         const hash = "0x" + "3".repeat(64);
         const leg = (value) => ({

tests/uniswapRouterAddress.test.js

@@ -47,7 +47,7 @@ globalThis.chrome = {
 const { state } = require("../src/shared/state");
 const { fetchRecentTransactions } = require("../src/shared/transactions");
 const approval = require("../src/popup/views/approval");
-const { decodeCalldata } = approval;
+const { decodeCalldata } = require("../src/shared/calldataDecoder");
 const transactionDetail = require("../src/popup/views/transactionDetail");
 
 const MAINNET = "0x1";

tests/uniswapUnknownDecimals.test.js

@@ -18,7 +18,7 @@ globalThis.chrome = {
 const { AbiCoder, Interface } = require("ethers");
 const { state } = require("../src/shared/state");
 const { unknownDecimalsAmount } = require("../src/shared/approvalAmount");
-const { decodeCalldata } = require("../src/popup/views/approval");
+const { decodeCalldata } = require("../src/shared/calldataDecoder");
 
 const ROUTER = "0x66a9893cc07d91d95644aedd05d03f95e1dba8af";
 const RECIPIENT = "0xC0FfEE0000000000000000000000000000c0fFEe";

tests/unknownScaleDisplay.test.js

@@ -96,7 +96,7 @@ afterEach(() => {
 describe("balanceLine", () => {
     test("an unknown quantity and a zero one render differently", () => {
         const unknown = balanceLine("NOVEL", null, null, NOVEL);
-        const zero = balanceLine("NOVEL", "0", null, NOVEL);
+        const zero = balanceLine("NOVEL", 0, null, NOVEL);
         expect(unknown).not.toBe(zero);
         expect(quantities(unknown)).toEqual(["NOVEL", "quantity unknown"]);
         expect(quantities(zero)).toEqual(["NOVEL", "0.0000"]);
@@ -105,7 +105,7 @@ describe("balanceLine", () => {
     test("an unknown quantity produces no fiat figure, a zero one does", () => {
         prices[NOVEL] = 3;
         const unknown = balanceLine("NOVEL", null, 3, NOVEL);
-        const zero = balanceLine("NOVEL", "0", 3, NOVEL);
+        const zero = balanceLine("NOVEL", 0, 3, NOVEL);
         // A price times an unknown quantity is not $0.00: that is the same
         // claim of "nothing here" the quantity cell just refused to make.
         expect(unknown).toContain(