test(safe): tighten dynamic owner test

- Replace the mock ERC-1271 code with a signature-dependent validator

- Use a fixed marker signature to verify the dynamic owner path

Author: mouseless0x

packages/permissionless/accounts/safe/signUserOperation.test.ts

@@ -1,4 +1,4 @@
-import { http, createTestClient, size, slice } from "viem"
+import { http, createTestClient, padHex, size, slice } from "viem"
 import {
     entryPoint06Address,
     entryPoint07Address
@@ -190,11 +190,13 @@ describe("signUserOperation", () => {
 
     testWithRpc("signUserOperation_V07 with dynamic owner", async ({ rpc }) => {
         const eoaOwner = privateKeyToAccount(generatePrivateKey())
-        const dynamicSignerKey = privateKeyToAccount(generatePrivateKey())
 
-        // Contract owner validated through EIP-1271. The runtime code echoes
-        // the called selector back, so isValidSignature always returns the
-        // expected magic value (both the bytes32 and legacy bytes variants).
+        // Contract owner validated through EIP-1271. The owner "signs" with a
+        // fixed 65-byte marker signature and the owner contract only returns
+        // the magic value when that marker arrives in the signature argument,
+        // proving the dynamic part is threaded through to isValidSignature.
+        const markerSignature = padHex("0xc0ffee", { dir: "right", size: 65 })
+
         const erc1271OwnerAddress = privateKeyToAccount(
             generatePrivateKey()
         ).address
@@ -205,21 +207,41 @@ describe("signUserOperation", () => {
             chain: foundry
         })
 
+        // Minimal EIP-1271 validator. Safe v1.4.1 calls the legacy
+        // isValidSignature(bytes _data, bytes _signature) variant, so the
+        // calldata layout is: 4-byte selector, then the two head words with
+        // the offsets of the `_data` and `_signature` tails. The code loads
+        // the first 32 bytes of `_signature`, requires them to start with the
+        // 0xc0ffee marker, and only then returns the magic value 0x20c13b0b
+        // (the selector of the legacy variant); anything else reverts:
+        //
+        //   PUSH1 0x24 CALLDATALOAD   // offset of `_signature` tail
+        //   PUSH1 0x24 ADD            // + 4-byte selector + 32-byte length
+        //   CALLDATALOAD              // signature[0..32]
+        //   PUSH1 0xe8 SHR            // >> 232 bits: keep first 3 bytes
+        //   PUSH3 0xc0ffee EQ         // matches the marker?
+        //   PUSH1 0x17 JUMPI          // if so, jump to the return block
+        //   PUSH1 0x00 PUSH1 0x00 REVERT
+        //   JUMPDEST                  // 0x17
+        //   PUSH4 0x20c13b0b          // legacy EIP-1271 magic value
+        //   PUSH1 0xe0 SHL            // left-align it as bytes4
+        //   PUSH1 0x00 MSTORE         // store word at memory offset 0
+        //   PUSH1 0x20 PUSH1 0x00 RETURN // return that 32-byte word
         await testClient.setCode({
             address: erc1271OwnerAddress,
-            bytecode: "0x60003560e01c60e01b60005260206000f3"
+            bytecode:
+                "0x6024356024013560e81c62c0ffee1460175760006000fd5b6320c13b0b60e01b60005260206000f3"
         })
 
-        // A KMS-style owner: signs with a local key but lives at the
-        // ERC-1271 contract address.
+        // An owner that lives at the ERC-1271 contract address and produces
+        // the marker signature the contract expects.
         const dynamicOwner = toAccount({
             address: erc1271OwnerAddress,
-            async signMessage({ message }) {
-                return dynamicSignerKey.signMessage({ message })
+            async signMessage() {
+                return markerSignature
             },
-            async signTypedData(typedData) {
-                // biome-ignore lint/suspicious/noExplicitAny: test helper
-                return dynamicSignerKey.signTypedData(typedData as any)
+            async signTypedData() {
+                return markerSignature
             },
             async signTransaction() {
                 throw new Error("Not supported")