fix: drop viem from x402 address validation

packages/x402/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- Use `@metamask/utils` for Ethereum address checksum validation and drop `viem` as a package dependency. ([#246](https://github.com/MetaMask/smart-accounts-kit/pull/246))
+
 ## [0.1.0]
 
 ### Added

packages/x402/package.json

@@ -55,10 +55,12 @@
     "access": "public",
     "registry": "https://registry.npmjs.org/"
   },
+  "dependencies": {
+    "@metamask/utils": "^11.4.0"
+  },
   "peerDependencies": {
     "@x402/core": "^2.12.0",
-    "@x402/evm": "^2.12.0",
-    "viem": "^2.31.4"
+    "@x402/evm": "^2.12.0"
   },
   "devDependencies": {
     "@metamask/auto-changelog": "^5.0.2",
@@ -68,7 +70,6 @@
     "prettier": "^3.5.3",
     "tsup": "^8.5.0",
     "typescript": "5.5.4",
-    "viem": "2.31.4",
     "vitest": "^3.2.4"
   }
 }

packages/x402/src/ethereum.ts

@@ -0,0 +1,31 @@
+import {
+  getChecksumAddress,
+  isHexChecksumAddress,
+  type Hex,
+} from '@metamask/utils';
+
+/**
+ * Validate and normalize an Ethereum address to its EIP-55 checksum form.
+ *
+ * @param value - Address string to normalize.
+ * @returns The checksummed address.
+ */
+export function getAddress(value: string): Hex {
+  if (!isHexChecksumAddress(value)) {
+    throw new Error('Invalid Ethereum address');
+  }
+
+  const lowerAddress = value.toLowerCase();
+  const upperAddress = `0x${value.slice(2).toUpperCase()}`;
+  const checksummedAddress = getChecksumAddress(value);
+
+  if (
+    value !== lowerAddress &&
+    value !== upperAddress &&
+    value !== checksummedAddress
+  ) {
+    throw new Error('Invalid Ethereum address checksum');
+  }
+
+  return checksummedAddress;
+}

packages/x402/src/x402Client.ts

@@ -1,4 +1,6 @@
-import { type Hex, getAddress, isHex } from 'viem';
+import { isStrictHexString, type Hex } from '@metamask/utils';
+
+import { getAddress } from './ethereum';
 
 export type x402PaymentRequirements = {
   scheme: string;
@@ -49,7 +51,7 @@ export type x402Erc7710ClientConfig = {
 function normalizeDelegationPayload(
   payload: x402DelegationPaymentPayload,
 ): x402DelegationPaymentPayload {
-  if (!isHex(payload.permissionContext) || payload.permissionContext === '0x') {
+  if (!isStrictHexString(payload.permissionContext)) {
     throw new Error(
       'Invalid delegation payload: permissionContext must be non-empty hex data',
     );

packages/x402/src/x402Server.ts

@@ -1,5 +1,6 @@
-import { type Address, getAddress } from 'viem';
+import type { Hex } from '@metamask/utils';
 
+import { getAddress } from './ethereum';
 import type { x402PaymentRequirements } from './x402Client';
 
 export type x402Erc7710ServerConfig = {
@@ -14,7 +15,7 @@ export type x402Erc7710ServerConfig = {
  */
 function validateFacilitatorAddresses(
   publishedAddresses: unknown,
-): Address[] | undefined {
+): Hex[] | undefined {
   if (publishedAddresses === undefined) {
     return undefined;
   }
@@ -31,7 +32,7 @@ function validateFacilitatorAddresses(
     );
   }
 
-  const normalizedAddresses: Address[] = [];
+  const normalizedAddresses: Hex[] = [];
   const validationErrors: string[] = [];
 
   publishedAddresses.forEach((address, index) => {

packages/x402/test/x402Server.test.ts

@@ -119,6 +119,20 @@ describe('x402Erc7710Server', () => {
     ]);
   });
 
+  it('normalizes all-uppercase facilitatorAddresses', async () => {
+    const server = new x402Erc7710Server();
+
+    const result = await server.enhancePaymentRequirements(baseRequirements, {
+      extra: {
+        facilitatorAddresses: ['0xAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA'],
+      },
+    });
+
+    expect(result.extra?.facilitatorAddresses).toEqual([
+      '0xaAaAaAaaAaAaAaaAaAAAAAAAAaaaAaAaAaaAaaAa',
+    ]);
+  });
+
   it('throws when facilitatorAddresses is not an array', async () => {
     const server = new x402Erc7710Server();
 
@@ -156,4 +170,18 @@ describe('x402Erc7710Server', () => {
       'Invalid facilitatorAddresses specified: facilitatorAddresses[0] must be a string; facilitatorAddresses[1] is not a valid address: "not-an-address"',
     );
   });
+
+  it('throws for invalid mixed-case facilitatorAddress checksums', async () => {
+    const server = new x402Erc7710Server();
+
+    await expect(
+      server.enhancePaymentRequirements(baseRequirements, {
+        extra: {
+          facilitatorAddresses: ['0xaAaAaAaaAaAaAaaAaAAAAAAAAaaaAaAaAaaAaaAB'],
+        },
+      }),
+    ).rejects.toThrow(
+      'Invalid facilitatorAddresses specified: facilitatorAddresses[0] is not a valid address: "0xaAaAaAaaAaAaAaaAaAAAAAAAAaaaAaAaAaaAaaAB"',
+    );
+  });
 });

yarn.lock

@@ -862,18 +862,17 @@ __metadata:
   resolution: "@metamask/x402@workspace:packages/x402"
   dependencies:
     "@metamask/auto-changelog": "npm:^5.0.2"
+    "@metamask/utils": "npm:^11.4.0"
     "@x402/core": "npm:^2.12.0"
     "@x402/evm": "npm:^2.12.0"
     eslint: "npm:^9.39.2"
     prettier: "npm:^3.5.3"
     tsup: "npm:^8.5.0"
     typescript: "npm:5.5.4"
-    viem: "npm:2.31.4"
     vitest: "npm:^3.2.4"
   peerDependencies:
     "@x402/core": ^2.12.0
     "@x402/evm": ^2.12.0
-    viem: ^2.31.4
   languageName: unknown
   linkType: soft