Allow Advanced Permissions metadata in signtypeddata payload

packages/eth-json-rpc-middleware/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Allow Advanced Permissions `metadata` in signTypedData V4 requests ([#8603](https://github.com/MetaMask/core/pull/8603))
+
 ## [23.1.2]
 
 ### Changed

packages/eth-json-rpc-middleware/src/utils/validation.test.ts

@@ -160,5 +160,122 @@ describe('Validation Utils', () => {
 
       expect(() => validateTypedMessageKeys(data)).toThrow('Invalid input.');
     });
+
+    describe('metadata', () => {
+      const baseTypedData = {
+        types: {
+          EIP712Domain: [{ name: 'name', type: 'string' }],
+        },
+        primaryType: 'EIP712Domain',
+        domain: {},
+        message: {},
+      };
+
+      it('does not throw when metadata has exactly justification and origin as strings', () => {
+        const data = JSON.stringify({
+          ...baseTypedData,
+          metadata: {
+            justification: 'Permission to spend tokens',
+            origin: 'https://example.com',
+          },
+        });
+
+        expect(() => validateTypedMessageKeys(data)).not.toThrow();
+      });
+
+      it('does not throw when metadata is the only top-level key', () => {
+        const data = JSON.stringify({
+          metadata: {
+            justification: 'Permission to spend tokens',
+            origin: 'https://example.com',
+          },
+        });
+
+        expect(() => validateTypedMessageKeys(data)).not.toThrow();
+      });
+
+      it.each([
+        ['null', null],
+        ['a string', 'not-an-object'],
+        ['a number', 42],
+        ['a boolean', true],
+        ['an array', ['justification', 'origin']],
+      ])('throws when metadata is %s', (_label, value) => {
+        const data = JSON.stringify({
+          ...baseTypedData,
+          metadata: value,
+        });
+
+        expect(() => validateTypedMessageKeys(data)).toThrow('Invalid input.');
+      });
+
+      it('throws when metadata is missing justification', () => {
+        const data = JSON.stringify({
+          ...baseTypedData,
+          metadata: {
+            origin: 'https://example.com',
+          },
+        });
+
+        expect(() => validateTypedMessageKeys(data)).toThrow('Invalid input.');
+      });
+
+      it('throws when metadata is missing origin', () => {
+        const data = JSON.stringify({
+          ...baseTypedData,
+          metadata: {
+            justification: 'Permission to spend tokens',
+          },
+        });
+
+        expect(() => validateTypedMessageKeys(data)).toThrow('Invalid input.');
+      });
+
+      it('throws when metadata.justification is not a string', () => {
+        const data = JSON.stringify({
+          ...baseTypedData,
+          metadata: {
+            justification: 123,
+            origin: 'https://example.com',
+          },
+        });
+
+        expect(() => validateTypedMessageKeys(data)).toThrow('Invalid input.');
+      });
+
+      it('throws when metadata.origin is not a string', () => {
+        const data = JSON.stringify({
+          ...baseTypedData,
+          metadata: {
+            justification: 'Permission to spend tokens',
+            origin: 123,
+          },
+        });
+
+        expect(() => validateTypedMessageKeys(data)).toThrow('Invalid input.');
+      });
+
+      it('throws when metadata has an extraneous third key', () => {
+        const data = JSON.stringify({
+          ...baseTypedData,
+          metadata: {
+            justification: 'Permission to spend tokens',
+            origin: 'https://example.com',
+            extra: 'unexpected',
+          },
+        });
+
+        expect(() => validateTypedMessageKeys(data)).toThrow('Invalid input.');
+      });
+
+      it('throws when metadata is an empty object', () => {
+        const data = JSON.stringify({
+          ...baseTypedData,
+          metadata: {},
+        });
+
+        expect(() => validateTypedMessageKeys(data)).toThrow('Invalid input.');
+      });
+    });
   });
 });

packages/eth-json-rpc-middleware/src/utils/validation.ts

@@ -199,12 +199,38 @@ export function validateTypedDataForPrototypePollution(data: string): void {
  */
 export function validateTypedMessageKeys(data: string): void {
   const parsedData = parseTypedMessage(data);
-  const allowedKeys = new Set(Object.keys(TYPED_MESSAGE_SCHEMA.properties));
+  const allowedKeys = new Set([
+    ...Object.keys(TYPED_MESSAGE_SCHEMA.properties),
+    'metadata',
+  ]);
   const hasExtraneousKey = Object.keys(parsedData).some(
     (key) => !allowedKeys.has(key),
   );
 
   if (hasExtraneousKey) {
     throw rpcErrors.invalidInput();
   }
+
+  // Advanced Permissions adds `metadata: { justification: string, origin: string }` to eth_signTypedData requests.
+  // see GatorPermissionsController.decodePermissionFromPermissionContextForOrigin for more details.
+  const { metadata } = parsedData as { metadata?: unknown };
+  if (metadata !== undefined) {
+    if (typeof metadata !== 'object' || metadata === null) {
+      throw rpcErrors.invalidInput();
+    }
+
+    const { justification, origin } = metadata as {
+      justification?: unknown;
+      origin?: unknown;
+    };
+
+    if (typeof justification !== 'string' || typeof origin !== 'string') {
+      throw rpcErrors.invalidInput();
+    }
+
+    // we only need to check the keys length, because we already checked the known keys (justification and origin).
+    if (Object.keys(metadata).length !== 2) {
+      throw rpcErrors.invalidInput();
+    }
+  }
 }