fix: a permit on the zero address never reads as ETH (closes #660)

Permit2 has no allowance of ETH, but the swap decoder read a permit's
zero-address token as ETH. Its Allowance token line read ETH. A permit of
1 wei of the zero address before a V4 step of 5 ETH also stood as the
Amount figure, which then read 0.000000000000000001 ETH.

Such a permit now never stands as the Amount figure. Its lines give the
amount in base units and name the zero address, as for a token nothing
knows.

Model: opus-5-5

README.md

@@ -3491,52 +3491,54 @@ Currently supported:
   which it does only in the plain shape of Uniswap's own routes: it comes before
   the step that sets the input side, it is the only `PERMIT2_PERMIT` in the
   transaction and there is no `PERMIT2_PERMIT_BATCH`, its spender is the router,
-  the router may not let it fail, no step before it takes its token, a
+  its token is not the zero address, the router may not let it fail, no step
-  `PERMIT2_TRANSFER_FROM` of it included, or a token the decoder does not know,
+  before it takes its token, a `PERMIT2_TRANSFER_FROM` of it included, or a
-  and the decoder reads every step after it in full. Permit2 then lets the
+  token the decoder does not know, and the decoder reads every step after it in
-  router take no more of the token than that amount, so the permit covers every
+  full. Permit2 then lets the router take no more of the token than that amount,
-  take of it. A step before the permit takes under whatever allowance the router
+  so the permit covers every take of it. Permit2 has no allowance of ETH, so a
-  already had, so it may take more than the permit's amount, which would then
+  permit on the zero address covers no take of ETH. A step before the permit
-  read lower than what leaves the user's wallet: a `PERMIT2_TRANSFER_FROM` of
+  takes under whatever allowance the router already had, so it may take more
-  2,000 USDT into the router, then a permit of 600 USDT to the router and a V3
+  than the permit's amount, which would then read lower than what leaves the
-  exact-in of 2,000 USDT paid from the router, read `Amount 2000.0000 USDT`. A
+  user's wallet: a `PERMIT2_TRANSFER_FROM` of 2,000 USDT into the router, then a
-  later permit or batch may raise what Permit2 lets the router take, and so may
+  permit of 600 USDT to the router and a V3 exact-in of 2,000 USDT paid from the
-  a step the decoder does not read in full: a command the decoder does not read
+  router, read `Amount 2000.0000 USDT`. A later permit or batch may raise what
-  (listed at the end of this section), a step whose input it cannot read, in
+  Permit2 lets the router take, and so may a step the decoder does not read in
-  whole or in part, and a step it fails on. Every other `PERMIT2_PERMIT`, before
+  full: a command the decoder does not read (listed at the end of this section),
-  the step that sets the input side or after it, leaves `Token In` and the
+  a step whose input it cannot read, in whole or in part, and a step it fails
-  `Amount` line as they read with no permit, unless it lets a spender other than
+  on. Every other `PERMIT2_PERMIT`, before the step that sets the input side or
-  the router take `Token In` (see below): a permit of 5,000 DAI to another
+  after it, leaves `Token In` and the `Amount` line as they read with no permit,
-  address and then a V3 exact-in of 600 USDT read `Swap USDT → USDC` with
+  unless it lets a spender other than the router take `Token In` (see below): a
-  `Amount 600.0000 USDT`, and so do that exact-in and then a permit of 5,000 DAI
+  permit of 5,000 DAI to another address and then a V3 exact-in of 600 USDT read
-  to the router. When a permit's amount stands and the step that sets the input
+  `Swap USDT → USDC` with `Amount 600.0000 USDT`, and so do that exact-in and
-  side spends a token other than the permit's, or one the decoder does not know,
+  then a permit of 5,000 DAI to the router. When a permit's amount stands and
-  that step's amount gets lines of its own, unless it states no amount and the
+  the step that sets the input side spends a token other than the permit's, or
-  user pays it none of its input token. Each take the total does not count gives
+  one the decoder does not know, that step's amount gets lines of its own,
-  three lines after the `Amount` line (after `Token In` when there is none): one
+  unless it states no amount and the user pays it none of its input token. Each
-  of a token other than `Token In`; one of `Token In` after an amount that is
+  take the total does not count gives three lines after the `Amount` line (after
-  not a quantity (a V4 open delta, `ALREADY_PAID`, which keep their wording on
+  `Token In` when there is none): one of a token other than `Token In`; one of
-  the `Amount` line, or no stated amount, as of a V4 exact-out step); and one
+  `Token In` after an amount that is not a quantity (a V4 open delta,
-  whose amount the decoder does not know. When there is no `Amount` line, each
+  `ALREADY_PAID`, which keep their wording on the `Amount` line, or no stated
-  take the total counts gets them too, so that every amount the decoder reads is
+  amount, as of a V4 exact-out step); and one whose amount the decoder does not
-  shown: the amount the step that sets the input side states, when it is a
+  know. When there is no `Amount` line, each take the total counts gets them
-  quantity and the user pays that step (a V2 or V3 step whose `payerIsUser` is
+  too, so that every amount the decoder reads is shown: the amount the step that
-  true, a V4 step the user pays some of its input token, or a `WRAP_ETH`, whose
+  sets the input side states, when it is a quantity and the user pays that step
-  ETH comes from the transaction's value), and each later take of `Token In`
+  (a V2 or V3 step whose `payerIsUser` is true, a V4 step the user pays some of
-  added to it. A step that sets the input side and is paid from the router takes
+  its input token, or a `WRAP_ETH`, whose ETH comes from the transaction's
-  nothing from the user's wallet and gets none. A `PERMIT2_PERMIT` the decoder
+  value), and each later take of `Token In` added to it. A step that sets the
-  cannot read, then V3 exact-ins of 600 USDT and 400 DAI paid by the user, give
+  input side and is paid from the router takes nothing from the user's wallet
-  lines for both amounts. When the step that sets the input side states no
+  and gets none. A `PERMIT2_PERMIT` the decoder cannot read, then V3 exact-ins
-  amount, the user pays it some of its input token, and there is no `Amount`
+  of 600 USDT and 400 DAI paid by the user, give lines for both amounts. When
-  line, that step gets them too whenever another take's lines give a figure, or
+  the step that sets the input side states no amount, the user pays it some of
-  a `PERMIT2_TRANSFER_FROM` of its token gives one, on the lines below or, into
+  its input token, and there is no `Amount` line, that step gets them too
-  the router, on its `Paid to` line, so that figure cannot read as all that
+  whenever another take's lines give a figure, or a `PERMIT2_TRANSFER_FROM` of
-  leaves. When it states no amount and the user pays it none of its input token,
+  its token gives one, on the lines below or, into the router, on its `Paid to`
-  as when the router pays it, that step takes none of that token from the user's
+  line, so that figure cannot read as all that leaves. When it states no amount
-  wallet and never gets them, with a permit or without. They come in step order,
+  and the user pays it none of its input token, as when the router pays it, that
-  except that the step that sets the input side comes first when it has them,
+  step takes none of that token from the user's wallet and never gets them, with
-  followed, when there is no `Amount` line, by the other takes the total counts:
+  a permit or without. They come in step order, except that the step that sets
-  `Moved from the sender`, its amount, worded as the `Amount` line words one, or
+  the input side comes first when it has them, followed, when there is no
+  `Amount` line, by the other takes the total counts: `Moved from the sender`,
+  its amount, worded as the `Amount` line words one, or
   `Unknown (could not be decoded)` when the decoder does not know it;
   `Token moved`, giving the token's address as the `Token In` line does; and
   `Moved to`, which reads `The swap step that spends it`. A token the decoder
@@ -3569,30 +3571,32 @@ Currently supported:
   amount stands gives none: the `Amount` line gives its amount, `Token In` its
   token, and its spender is the router. Each allowance a `PERMIT2_PERMIT_BATCH`
   grants, one for each token it names, all for its one spender, gives the same
-  three lines, in step order with those of each `PERMIT2_PERMIT`. A
+  three lines, in step order with those of each `PERMIT2_PERMIT`. For an
-  `PERMIT2_PERMIT` or `PERMIT2_PERMIT_BATCH` whose input the decoder cannot
+  allowance of the zero address, `Permit2 allowance` gives the amount in base
-  read, such as one whose token or spender word has a nonzero top byte, may let
+  units and `Allowance token` gives the zero address. A `PERMIT2_PERMIT` or
-  any spender take any amount of any token: it gives one `Permit2 allowance`
+  `PERMIT2_PERMIT_BATCH` whose input the decoder cannot read, such as one whose
-  line alone, reading `Unknown (could not be decoded)`. These lines change no
+  token or spender word has a nonzero top byte, may let any spender take any
-  `Paid to` line: a permit or batch pays nobody. But code that a step runs, such
+  amount of any token: it gives one `Permit2 allowance` line alone, reading
-  as a V4 pool's hook or a token's own code, can call a spender other than the
+  `Unknown (could not be decoded)`. These lines change no `Paid to` line: a
-  router, which can then take up to its allowance from the user's wallet before
+  permit or batch pays nobody. But code that a step runs, such as a V4 pool's
-  the transaction ends. So an allowance to any spender but the router, or a
+  hook or a token's own code, can call a spender other than the router, which
-  permit or batch the decoder cannot read, makes the minimum read
+  can then take up to its allowance from the user's wallet before the
-  `Min. paid out`, and when its token is `Token In`, or the decoder does not
+  transaction ends. So an allowance to any spender but the router, or a permit
-  know its token or `Token In`, it leaves no `Amount` line, whose figure might
+  or batch the decoder cannot read, makes the minimum read `Min. paid out`, and
-  be too low: a permit of 5,000 USDT to another address and then a V3 exact-in
+  when its token is `Token In`, or the decoder does not know its token or
-  of 600 USDT read with no `Amount` line, and the 600 USDT gets lines of its
+  `Token In`, it leaves no `Amount` line, whose figure might be too low: a
-  own. A step goes unread when its recipient does not decode as an address, when
+  permit of 5,000 USDT to another address and then a V3 exact-in of 600 USDT
-  it is a V3 swap step whose path is shorter than one token address or has bytes
+  read with no `Amount` line, and the 600 USDT gets lines of its own. A step
-  after its last hop, or when it is a command the decoder does not read: every
+  goes unread when its recipient does not decode as an address, when it is a V3
-  command other than `PERMIT2_PERMIT`, `PERMIT2_PERMIT_BATCH`,
+  swap step whose path is shorter than one token address or has bytes after its
-  `PERMIT2_TRANSFER_FROM`, `V2_SWAP_EXACT_IN`, `V2_SWAP_EXACT_OUT`,
+  last hop, or when it is a command the decoder does not read: every command
-  `V3_SWAP_EXACT_IN`, `V3_SWAP_EXACT_OUT`, `V4_SWAP`, `SWEEP`, `TRANSFER`,
+  other than `PERMIT2_PERMIT`, `PERMIT2_PERMIT_BATCH`, `PERMIT2_TRANSFER_FROM`,
-  `PAY_PORTION`, `PAY_PORTION_FULL_PRECISION`, `ACROSS_V4_DEPOSIT_V3`,
+  `V2_SWAP_EXACT_IN`, `V2_SWAP_EXACT_OUT`, `V3_SWAP_EXACT_IN`,
-  `WRAP_ETH`, `UNWRAP_WETH` and `BALANCE_CHECK_ERC20`
+  `V3_SWAP_EXACT_OUT`, `V4_SWAP`, `SWEEP`, `TRANSFER`, `PAY_PORTION`,
-  (`PERMIT2_TRANSFER_FROM_BATCH`, `EXECUTE_SUB_PLAN` and the NFT commands among
+  `PAY_PORTION_FULL_PRECISION`, `ACROSS_V4_DEPOSIT_V3`, `WRAP_ETH`,
-  them), or a type its release names no command for.
+  `UNWRAP_WETH` and `BALANCE_CHECK_ERC20` (`PERMIT2_TRANSFER_FROM_BATCH`,
+  `EXECUTE_SUB_PLAN` and the NFT commands among them), or a type its release
+  names no command for.
 
 ### Non-Goals Forever
 

src/shared/uniswap.js

@@ -2023,14 +2023,16 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         // plain shape of Uniswap's own routes: it comes before the step that
         // set the input side, it is the only PERMIT2_PERMIT in the
         // transaction and there is no PERMIT2_PERMIT_BATCH, its spender is
-        // the router, the router may not let it fail, no step before it took
+        // the router, its token is not the zero address, the router may not
-        // its token or one not known (a PERMIT2_TRANSFER_FROM of its token
+        // let it fail, no step before it took its token or one not known (a
-        // included), and this decoder read every step after it in full (see
+        // PERMIT2_TRANSFER_FROM of its token included), and this decoder read
-        // stepsUnread). Permit2 then lets the router take no more of the token
+        // every step after it in full (see stepsUnread). Permit2 then lets the
-        // than that amount, so the permit covers every take of it. A step
+        // router take no more of the token than that amount, so the permit
-        // before it takes under whatever allowance the router already had, so
+        // covers every take of it. Permit2 has no allowance of ETH, so a
-        // it may take more. A later permit or batch, or a later step this
+        // permit on the zero address covers no take of ETH. A step before it
-        // decoder did not read, may raise what Permit2 lets the router take.
+        // takes under whatever allowance the router already had, so it may
+        // take more. A later permit or batch, or a later step this decoder
+        // did not read, may raise what Permit2 lets the router take.
         // Every other PERMIT2_PERMIT leaves Token In and the Amount line as
         // they read with no permit, and gets lines of its own below. A step
         // that may take from the sender what this decoder did not read leaves
@@ -2047,6 +2049,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             stepCommands.filter((c) => c === "PERMIT2_PERMIT").length === 1 &&
             !stepCommands.includes("PERMIT2_PERMIT_BATCH") &&
             sameAddress(permit.spender, toAddress) &&
+            permit.token !== "0x0000000000000000000000000000000000000000" &&
             !permit.allowedToFail &&
             permit.beforeEveryTake &&
             !stepsUnread.some((step) => step > permit.step);
@@ -2315,15 +2318,36 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                 });
                 continue;
             }
-            details.push({
+            // Permit2 has no allowance of ETH. An allowance of the zero
-                label: "Permit2 allowance",
+            // address reads as one of a token nothing knows: its amount in
-                value:
+            // base units, and the zero address as its token.
-                    p.amount >= MAX_UINT160
+            if (p.token === "0x0000000000000000000000000000000000000000") {
-                        ? "Unlimited"
+                details.push({
-                        : amountText(p.amount, tokenInfo(p.token, sources))
+                    label: "Permit2 allowance",
-                              .display,
+                    value:
-            });
+                        p.amount >= MAX_UINT160
-            details.push(tokenMovedLine("Allowance token", p.token, sources));
+                            ? "Unlimited"
+                            : unknownDecimalsAmount(p.amount),
+                });
+                details.push({
+                    label: "Allowance token",
+                    value: p.token,
+                    address: p.token,
+                    isToken: true,
+                });
+            } else {
+                details.push({
+                    label: "Permit2 allowance",
+                    value:
+                        p.amount >= MAX_UINT160
+                            ? "Unlimited"
+                            : amountText(p.amount, tokenInfo(p.token, sources))
+                                  .display,
+                });
+                details.push(
+                    tokenMovedLine("Allowance token", p.token, sources),
+                );
+            }
             details.push({
                 label: "Allowance spender",
                 value: p.spender,

tests/uniswap.test.js

@@ -3310,6 +3310,98 @@ describe("uniswap decoder", () => {
 
             expect(detail(result, "Amount").value).toBe("Up to 1000.0000 USDT");
         });
+
+        // https://git.eeqj.de/sneak/AutistMask/issues/660 — Permit2 has no
+        // allowance of ETH, so a permit on the zero address reads as one on a
+        // token nothing knows. On next at 53551c6 such a permit's Allowance
+        // token line read ETH. A permit of 1 wei of the zero address before a
+        // V4 step of 5 ETH made the Amount line read 0.000000000000000001 ETH.
+        describe("a permit on the zero address", () => {
+            const FIVE_ETH = 5000000000000000000n;
+            // The lines of a permit of `amount` base units of the zero
+            // address for the router.
+            const zeroAddressLines = (amount) => [
+                [
+                    "Permit2 allowance",
+                    amount + " base units (decimals unknown)",
+                ],
+                ["Allowance token", ZERO_ADDR],
+                ["Allowance spender", getAddress(ROUTER_ADDR)],
+            ];
+
+            test("a PERMIT2_PERMIT on the zero address names the address", () => {
+                const result = decodeSteps(
+                    [0x00, 0x0a],
+                    [
+                        V3_600,
+                        encodePermit2(
+                            ZERO_ADDR,
+                            1000000000000000000n,
+                            ROUTER_ADDR,
+                        ),
+                    ],
+                );
+                expect(linesBetweenTokens(result)).toEqual([
+                    ["Amount", "600.0000 USDT"],
+                    ...zeroAddressLines("1000000000000000000"),
+                ]);
+                expect(detail(result, "Allowance token").address).toBe(
+                    ZERO_ADDR,
+                );
+            });
+
+            test("a PERMIT2_PERMIT_BATCH entry on the zero address names the address", () => {
+                const result = decodeSteps(
+                    [0x03, 0x00],
+                    [
+                        encodePermit2Batch(
+                            [
+                                [USDT_ADDR, USDT_600],
+                                [ZERO_ADDR, 1000000000000000000n],
+                            ],
+                            ROUTER_ADDR,
+                        ),
+                        V3_600,
+                    ],
+                );
+                expect(linesBetweenTokens(result)).toEqual([
+                    ["Amount", "600.0000 USDT"],
+                    ...USDT_600_LINES,
+                    ...zeroAddressLines("1000000000000000000"),
+                ]);
+            });
+
+            test("a PERMIT2_PERMIT of 1 wei of the zero address, then a V4 step of 5 ETH the user settles, shows the 5 ETH", () => {
+                const result = decodeSteps(
+                    [0x0a, 0x10],
+                    [
+                        encodePermit2(ZERO_ADDR, 1n, ROUTER_ADDR),
+                        encodeV4Swap(
+                            new Uint8Array([
+                                V4_SWAP_EXACT_IN_SINGLE_ID,
+                                V4_SETTLE_ID,
+                                V4_TAKE_ALL_ID,
+                            ]),
+                            [
+                                encodeV4ExactInSingle(
+                                    ZERO_ADDR,
+                                    USDC_ADDR,
+                                    FIVE_ETH,
+                                    1n,
+                                ),
+                                settle(ZERO_ADDR, FIVE_ETH, true),
+                                encodeV4TakeAll(USDC_ADDR, 1n),
+                            ],
+                        ),
+                    ],
+                );
+                expect(detail(result, "Token In").value).toBe("ETH (native)");
+                expect(linesBetweenTokens(result)).toEqual([
+                    ["Amount", "5.0000 ETH"],
+                    ...zeroAddressLines("1"),
+                ]);
+            });
+        });
     });
 
     // https://git.eeqj.de/sneak/AutistMask/issues/359 — the output half, in