feat(sdk-core): add passkey types, webauthn provider interface, and prf helpers

- WebAuthnOtpDevice: imported from @bitgo/public-types@6.1.0 (id, credentialId, prfSalt?)
- PasskeyAuthResult: stays local (ArrayBuffer not encodable in io-ts)
- WebAuthnProvider: create() -> PublicKeyCredential, get() -> PasskeyAuthResult
- buildEvalByCredential: returns { evalByCredential, credIdToDevice }, skips no-prfSalt devices
- matchDeviceByCredentialId: uses credIdToDevice map, throws retail error message
- export * from './passkey' added to bitgo/index.ts barrel
- unit tests: 8 cases covering happy path, empty list, prfSalt skip, and error message

TICKET: WCN-187

Author: derranW26

modules/sdk-core/package.json

@@ -40,7 +40,7 @@
     ]
   },
   "dependencies": {
-    "@bitgo/public-types": "5.96.2",
+    "@bitgo/public-types": "6.1.0",
     "@bitgo/sdk-lib-mpc": "^10.11.0",
     "@bitgo/secp256k1": "^1.11.0",
     "@bitgo/sjcl": "^1.1.0",

modules/sdk-core/src/bitgo/index.ts

@@ -20,6 +20,7 @@ export * from './market';
 export * from './pendingApproval';
 export { WalletProofs } from './proofs';
 export * from './recovery';
+export * from './passkey';
 export * from './staking';
 export * from './trading';
 export * from './tss';

modules/sdk-core/src/bitgo/passkey/index.ts

@@ -0,0 +1,2 @@
+export { WebAuthnOtpDevice, PasskeyAuthResult, PasskeyGetOptions, WebAuthnProvider } from './types';
+export { buildEvalByCredential, matchDeviceByCredentialId } from './prfHelpers';

modules/sdk-core/src/bitgo/passkey/prfHelpers.ts

@@ -0,0 +1,39 @@
+import type { KeychainWebauthnDevice } from '../keychain/iKeychains';
+
+/**
+ * Builds the PRF eval map and credential-to-device lookup from a wallet keychain's webauthn devices.
+ * Devices without a prfSalt are skipped.
+ */
+export function buildEvalByCredential(devices: KeychainWebauthnDevice[]): {
+  evalByCredential: Record<string, string>;
+  credIdToDevice: Map<string, KeychainWebauthnDevice>;
+} {
+  const evalByCredential: Record<string, string> = {};
+  const credIdToDevice = new Map<string, KeychainWebauthnDevice>();
+
+  for (const device of devices) {
+    if (!device.prfSalt) continue;
+
+    const { credID } = device.authenticatorInfo;
+    evalByCredential[credID] = device.prfSalt;
+    credIdToDevice.set(credID, device);
+  }
+
+  return { evalByCredential, credIdToDevice };
+}
+
+/**
+ * Returns the webauthn device matching the given credential ID.
+ * @throws if no matching device is found
+ */
+export function matchDeviceByCredentialId(
+  devices: KeychainWebauthnDevice[],
+  credentialId: string
+): KeychainWebauthnDevice {
+  const { credIdToDevice } = buildEvalByCredential(devices);
+  const device = credIdToDevice.get(credentialId);
+  if (!device) {
+    throw new Error('Could not identify which passkey device was used');
+  }
+  return device;
+}

modules/sdk-core/src/bitgo/passkey/types.ts

@@ -0,0 +1,24 @@
+export type { WebAuthnOtpDevice } from '@bitgo/public-types';
+
+/** Result of a WebAuthn assertion with the PRF extension. */
+export interface PasskeyAuthResult {
+  // raw PRF output; undefined if the authenticator does not support PRF
+  prfResult: ArrayBuffer | undefined;
+  // base64url credential ID identifying which passkey was used
+  credentialId: string;
+  // OTP code from the assertion
+  otpCode: string;
+}
+
+/** Options for WebAuthnProvider.get(). */
+export interface PasskeyGetOptions {
+  publicKey: PublicKeyCredentialRequestOptions;
+  // PRF eval map: { [credentialId]: prfSalt }
+  evalByCredential?: Record<string, string>;
+}
+
+/** Abstraction over the WebAuthn credential API. Inject a mock in tests. */
+export interface WebAuthnProvider {
+  create(options: PublicKeyCredentialCreationOptions): Promise<PublicKeyCredential>;
+  get(options: PasskeyGetOptions): Promise<PasskeyAuthResult>;
+}

modules/sdk-core/test/unit/bitgo/passkey/prfHelpers.test.ts

@@ -0,0 +1,79 @@
+import * as assert from 'assert';
+import { buildEvalByCredential, matchDeviceByCredentialId } from '../../../../src/bitgo/passkey/prfHelpers';
+import { KeychainWebauthnDevice } from '../../../../src/bitgo/keychain/iKeychains';
+
+const device1: KeychainWebauthnDevice = {
+  otpDeviceId: 'oid-1',
+  authenticatorInfo: { credID: 'cred-aaa', fmt: 'none', publicKey: 'pk-1' },
+  prfSalt: 'salt-aaa',
+  encryptedPrv: 'enc-prv-1',
+};
+
+const device2: KeychainWebauthnDevice = {
+  otpDeviceId: 'oid-2',
+  authenticatorInfo: { credID: 'cred-bbb', fmt: 'none', publicKey: 'pk-2' },
+  prfSalt: 'salt-bbb',
+  encryptedPrv: 'enc-prv-2',
+};
+
+describe('buildEvalByCredential', function () {
+  it('maps each device credID to its prfSalt in evalByCredential', function () {
+    const { evalByCredential } = buildEvalByCredential([device1, device2]);
+    assert.deepStrictEqual(evalByCredential, {
+      'cred-aaa': 'salt-aaa',
+      'cred-bbb': 'salt-bbb',
+    });
+  });
+
+  it('populates credIdToDevice with both devices', function () {
+    const { credIdToDevice } = buildEvalByCredential([device1, device2]);
+    assert.strictEqual(credIdToDevice.get('cred-aaa'), device1);
+    assert.strictEqual(credIdToDevice.get('cred-bbb'), device2);
+  });
+
+  it('returns empty maps for an empty device list', function () {
+    const { evalByCredential, credIdToDevice } = buildEvalByCredential([]);
+    assert.deepStrictEqual(evalByCredential, {});
+    assert.strictEqual(credIdToDevice.size, 0);
+  });
+
+  it('skips devices with empty prfSalt', function () {
+    const deviceNoPrf = { ...device1, prfSalt: '' };
+    const { evalByCredential, credIdToDevice } = buildEvalByCredential([deviceNoPrf, device2]);
+    assert.deepStrictEqual(evalByCredential, { 'cred-bbb': 'salt-bbb' });
+    assert.strictEqual(credIdToDevice.has('cred-aaa'), false);
+  });
+
+  it('skips devices with undefined prfSalt', function () {
+    const deviceNoPrf = { ...device1, prfSalt: undefined as unknown as string };
+    const { evalByCredential, credIdToDevice } = buildEvalByCredential([deviceNoPrf, device2]);
+    assert.deepStrictEqual(evalByCredential, { 'cred-bbb': 'salt-bbb' });
+    assert.strictEqual(credIdToDevice.has('cred-aaa'), false);
+  });
+});
+
+describe('matchDeviceByCredentialId', function () {
+  it('returns the matching device', function () {
+    const result = matchDeviceByCredentialId([device1, device2], 'cred-bbb');
+    assert.strictEqual(result, device2);
+  });
+
+  it('returns the first device when it matches', function () {
+    const result = matchDeviceByCredentialId([device1, device2], 'cred-aaa');
+    assert.strictEqual(result, device1);
+  });
+
+  it('throws with the retail error message when no device matches', function () {
+    assert.throws(
+      () => matchDeviceByCredentialId([device1, device2], 'cred-unknown'),
+      (err: Error) => {
+        assert.strictEqual(err.message, 'Could not identify which passkey device was used');
+        return true;
+      }
+    );
+  });
+
+  it('throws when the device list is empty', function () {
+    assert.throws(() => matchDeviceByCredentialId([], 'cred-aaa'), Error);
+  });
+});