Adds signAuthorization method for EIP-7702 (#407)

* Add methods for signing, hashing, and recovering authorizations, as per 7702

* Add signAuthorization components to index.ts and index.test.ts

* Fix linting errors

* Remove incorrect note from comment.

* Renamed a couple of authorization symbols to explicitly be EIP-7702, shuffled non-exported members to the bottom of the file, and renamed a few test constants to aid readability. Also used it.each for multiple test cases.

package.json

@@ -44,6 +44,7 @@
     "test:watch": "jest --watch"
   },
   "dependencies": {
+    "@ethereumjs/rlp": "^4.0.1",
     "@ethereumjs/util": "^8.1.0",
     "@metamask/abi-utils": "^3.0.0",
     "@metamask/utils": "^11.0.1",

src/index.test.ts

@@ -21,6 +21,9 @@ Array [
   "decrypt",
   "decryptSafely",
   "getEncryptionPublicKey",
+  "signEIP7702Authorization",
+  "recoverEIP7702Authorization",
+  "hashEIP7702Authorization",
 ]
 `);
   });

src/index.ts

@@ -1,4 +1,5 @@
 export * from './personal-sign';
 export * from './sign-typed-data';
 export * from './encryption';
+export * from './sign-eip7702-authorization';
 export { concatSig, normalize } from './utils';

src/sign-eip7702-authorization.test.ts

@@ -0,0 +1,242 @@
+import { bufferToHex, privateToAddress } from '@ethereumjs/util';
+
+import {
+  signEIP7702Authorization,
+  recoverEIP7702Authorization,
+  EIP7702Authorization,
+  hashEIP7702Authorization,
+} from './sign-eip7702-authorization';
+
+const TEST_PRIVATE_KEY = Buffer.from(
+  '4af1bceebf7f3634ec3cff8a2c38e51178d5d4ce585c52d6043e5e2cc3418bb0',
+  'hex',
+);
+
+const TEST_ADDRESS = bufferToHex(privateToAddress(TEST_PRIVATE_KEY));
+
+const TEST_AUTHORIZATION: EIP7702Authorization = [
+  8545,
+  '0x1234567890123456789012345678901234567890',
+  1,
+];
+
+const EXPECTED_AUTHORIZATION_HASH = Buffer.from(
+  'b847dee5b33802280f3279d57574e1eb6bf5d628d7f63049e3cb20bad211056c',
+  'hex',
+);
+
+const EXPECTED_SIGNATURE =
+  '0xebea1ac12f17a56a514dfecbcbc8bbee7b089fa3fcee31680d1e2c1588f623df7973cab74e12536678995377da38c96c65c52897750b73462c6760ef2737dba41b';
+
+describe('signAuthorization', () => {
+  describe('signAuthorization()', () => {
+    it('should produce the correct signature', () => {
+      const signature = signEIP7702Authorization({
+        privateKey: TEST_PRIVATE_KEY,
+        authorization: TEST_AUTHORIZATION,
+      });
+
+      expect(signature).toBe(EXPECTED_SIGNATURE);
+    });
+
+    it('should throw if private key is null', () => {
+      expect(() =>
+        signEIP7702Authorization({
+          privateKey: null as any,
+          authorization: TEST_AUTHORIZATION,
+        }),
+      ).toThrow('Missing privateKey parameter');
+    });
+
+    it('should throw if private key is undefined', () => {
+      expect(() =>
+        signEIP7702Authorization({
+          privateKey: undefined as any,
+          authorization: TEST_AUTHORIZATION,
+        }),
+      ).toThrow('Missing privateKey parameter');
+    });
+
+    it('should throw if authorization is null', () => {
+      expect(() =>
+        signEIP7702Authorization({
+          privateKey: TEST_PRIVATE_KEY,
+          authorization: null as any,
+        }),
+      ).toThrow('Missing authorization parameter');
+    });
+
+    it('should throw if authorization is undefined', () => {
+      expect(() =>
+        signEIP7702Authorization({
+          privateKey: TEST_PRIVATE_KEY,
+          authorization: undefined as any,
+        }),
+      ).toThrow('Missing authorization parameter');
+    });
+
+    it('should throw if chainId is null', () => {
+      expect(() =>
+        signEIP7702Authorization({
+          privateKey: TEST_PRIVATE_KEY,
+          authorization: [
+            null as unknown as number,
+            TEST_AUTHORIZATION[1],
+            TEST_AUTHORIZATION[2],
+          ],
+        }),
+      ).toThrow('Missing chainId parameter');
+    });
+
+    it('should throw if contractAddress is null', () => {
+      expect(() =>
+        signEIP7702Authorization({
+          privateKey: TEST_PRIVATE_KEY,
+          authorization: [
+            TEST_AUTHORIZATION[0],
+            null as unknown as string,
+            TEST_AUTHORIZATION[2],
+          ],
+        }),
+      ).toThrow('Missing contractAddress parameter');
+    });
+
+    it('should throw if nonce is null', () => {
+      expect(() =>
+        signEIP7702Authorization({
+          privateKey: TEST_PRIVATE_KEY,
+          authorization: [
+            TEST_AUTHORIZATION[0],
+            TEST_AUTHORIZATION[1],
+            null as unknown as number,
+          ],
+        }),
+      ).toThrow('Missing nonce parameter');
+    });
+  });
+
+  describe('hashAuthorization()', () => {
+    it('should produce the correct hash', () => {
+      const hash = hashEIP7702Authorization(TEST_AUTHORIZATION);
+
+      expect(hash).toStrictEqual(EXPECTED_AUTHORIZATION_HASH);
+    });
+
+    it('should throw if authorization is null', () => {
+      expect(() =>
+        hashEIP7702Authorization(null as unknown as EIP7702Authorization),
+      ).toThrow('Missing authorization parameter');
+    });
+
+    it('should throw if authorization is undefined', () => {
+      expect(() =>
+        hashEIP7702Authorization(undefined as unknown as EIP7702Authorization),
+      ).toThrow('Missing authorization parameter');
+    });
+
+    it('should throw if chainId is null', () => {
+      expect(() =>
+        hashEIP7702Authorization([
+          null as unknown as number,
+          TEST_AUTHORIZATION[1],
+          TEST_AUTHORIZATION[2],
+        ]),
+      ).toThrow('Missing chainId parameter');
+    });
+
+    it('should throw if contractAddress is null', () => {
+      expect(() =>
+        hashEIP7702Authorization([
+          TEST_AUTHORIZATION[0],
+          null as unknown as string,
+          TEST_AUTHORIZATION[2],
+        ]),
+      ).toThrow('Missing contractAddress parameter');
+    });
+
+    it('should throw if nonce is null', () => {
+      expect(() =>
+        hashEIP7702Authorization([
+          TEST_AUTHORIZATION[0],
+          TEST_AUTHORIZATION[1],
+          null as unknown as number,
+        ]),
+      ).toThrow('Missing nonce parameter');
+    });
+  });
+
+  describe('recoverAuthorization()', () => {
+    it('should recover the address from a signature', () => {
+      const recoveredAddress = recoverEIP7702Authorization({
+        authorization: TEST_AUTHORIZATION,
+        signature: EXPECTED_SIGNATURE,
+      });
+
+      expect(recoveredAddress).toBe(TEST_ADDRESS);
+    });
+
+    it('should throw if signature is null', () => {
+      expect(() =>
+        recoverEIP7702Authorization({
+          signature: null as unknown as string,
+          authorization: TEST_AUTHORIZATION,
+        }),
+      ).toThrow('Missing signature parameter');
+    });
+
+    it('should throw if signature is undefined', () => {
+      expect(() =>
+        recoverEIP7702Authorization({
+          signature: undefined as unknown as string,
+          authorization: TEST_AUTHORIZATION,
+        }),
+      ).toThrow('Missing signature parameter');
+    });
+
+    it('should throw if authorization is null', () => {
+      expect(() =>
+        recoverEIP7702Authorization({
+          signature: EXPECTED_SIGNATURE,
+          authorization: null as unknown as EIP7702Authorization,
+        }),
+      ).toThrow('Missing authorization parameter');
+    });
+
+    it('should throw if authorization is undefined', () => {
+      expect(() =>
+        recoverEIP7702Authorization({
+          signature: EXPECTED_SIGNATURE,
+          authorization: undefined as unknown as EIP7702Authorization,
+        }),
+      ).toThrow('Missing authorization parameter');
+    });
+  });
+
+  describe('sign-and-recover', () => {
+    const testCases = {
+      zeroChainId: [0, '0x1234567890123456789012345678901234567890', 1],
+      highChainId: [98765, '0x1234567890123456789012345678901234567890', 1],
+      zeroNonce: [8545, '0x1234567890123456789012345678901234567890', 0],
+      highNonce: [8545, '0x1234567890123456789012345678901234567890', 98765],
+      zeroContractAddress: [1, '0x0000000000000000000000000000000000000000', 1],
+      allZeroValues: [0, '0x0000000000000000000000000000000000000000', 0],
+    } as { [key: string]: EIP7702Authorization };
+
+    it.each(Object.entries(testCases))(
+      'should sign and recover %s',
+      (_, authorization) => {
+        const signature = signEIP7702Authorization({
+          privateKey: TEST_PRIVATE_KEY,
+          authorization,
+        });
+
+        const recoveredAddress = recoverEIP7702Authorization({
+          authorization,
+          signature,
+        });
+
+        expect(recoveredAddress).toBe(TEST_ADDRESS);
+      },
+    );
+  });
+});

src/sign-eip7702-authorization.ts

@@ -0,0 +1,129 @@
+import { encode } from '@ethereumjs/rlp';
+import { ecsign, publicToAddress, toBuffer } from '@ethereumjs/util';
+import { bytesToHex } from '@metamask/utils';
+import { keccak256 } from 'ethereum-cryptography/keccak';
+
+import { concatSig, isNullish, recoverPublicKey } from './utils';
+
+/**
+ * The authorization struct as defined in EIP-7702.
+ *
+ * @property chainId - The chain ID or 0 for any chain.
+ * @property contractAddress - The address of the contract being authorized.
+ * @property nonce - The nonce of the signing account (at the time of submission).
+ */
+export type EIP7702Authorization = [
+  chainId: number,
+  contractAddress: string,
+  nonce: number,
+];
+
+/**
+ * Sign an authorization message with the provided private key.
+ *
+ * @param options - The signing options.
+ * @param options.privateKey - The private key to sign with.
+ * @param options.authorization - The authorization data to sign.
+ * @returns The '0x'-prefixed hex encoded signature.
+ */
+export function signEIP7702Authorization({
+  privateKey,
+  authorization,
+}: {
+  privateKey: Buffer;
+  authorization: EIP7702Authorization;
+}): string {
+  validateEIP7702Authorization(authorization);
+
+  if (isNullish(privateKey)) {
+    throw new Error('Missing privateKey parameter');
+  }
+
+  const messageHash = hashEIP7702Authorization(authorization);
+
+  const { r, s, v } = ecsign(messageHash, privateKey);
+
+  // v is either 27n or 28n so is guaranteed to be a single byte
+  const vBuffer = toBuffer(v);
+
+  return concatSig(vBuffer, r, s);
+}
+
+/**
+ * Recover the address of the account that created the given authorization
+ * signature.
+ *
+ * @param options - The signature recovery options.
+ * @param options.signature - The '0x'-prefixed hex encoded message signature.
+ * @param options.authorization - The authorization data that was signed.
+ * @returns The '0x'-prefixed hex address of the signer.
+ */
+export function recoverEIP7702Authorization({
+  signature,
+  authorization,
+}: {
+  signature: string;
+  authorization: EIP7702Authorization;
+}): string {
+  validateEIP7702Authorization(authorization);
+
+  if (isNullish(signature)) {
+    throw new Error('Missing signature parameter');
+  }
+
+  const messageHash = hashEIP7702Authorization(authorization);
+
+  const publicKey = recoverPublicKey(messageHash, signature);
+
+  const sender = publicToAddress(publicKey);
+
+  return bytesToHex(sender);
+}
+
+/**
+ * Hash an authorization message according to the signing scheme.
+ * The message is encoded according to EIP-7702.
+ *
+ * @param authorization - The authorization data to hash.
+ * @returns The hash of the authorization message as a Buffer.
+ */
+export function hashEIP7702Authorization(
+  authorization: EIP7702Authorization,
+): Buffer {
+  validateEIP7702Authorization(authorization);
+
+  const encodedAuthorization = encode(authorization);
+
+  const message = Buffer.concat([
+    Buffer.from('05', 'hex'),
+    encodedAuthorization,
+  ]);
+
+  return Buffer.from(keccak256(message));
+}
+
+/**
+ * Validates an authorization object to ensure all required parameters are present.
+ *
+ * @param authorization - The authorization object to validate.
+ * @throws {Error} If the authorization object or any of its required parameters are missing.
+ */
+function validateEIP7702Authorization(authorization: EIP7702Authorization) {
+  if (isNullish(authorization)) {
+    throw new Error('Missing authorization parameter');
+  }
+
+  const [chainId, contractAddress, nonce] = authorization;
+
+  if (isNullish(chainId)) {
+    throw new Error('Missing chainId parameter');
+  }
+
+  if (isNullish(contractAddress)) {
+    throw new Error('Missing contractAddress parameter');
+  }
+
+  if (isNullish(nonce)) {
+    throw new Error('Missing nonce parameter');
+  }
+}