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fix(passkey-crypto): change deriveEnterpriseSalt output encoding from base64 to base64url #8677

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fix(passkey-crypto): change deriveEnterpriseSalt output encoding from base64 to base64url #8677

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3 changes: 2 additions & 1 deletion modules/passkey-crypto/package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,8 @@
},
"dependencies": {
"@bitgo/public-types": "6.1.0",
"@bitgo/sdk-core": "^36.44.0"
"@bitgo/sdk-core": "^36.44.0",
"@bitgo/sjcl": "^1.1.0"
},
"devDependencies": {
"@types/node": "^18.0.0"
Expand Down
16 changes: 4 additions & 12 deletions modules/passkey-crypto/src/attachPasskeyToWallet.ts
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Expand Up @@ -37,8 +37,8 @@ export async function attachPasskeyToWallet(params: {
const keychain = await wallet.getEncryptedUserKeychain();
const keychainId = keychain.id;

// Derive enterprise-scoped salt
const enterpriseSalt = deriveEnterpriseSalt(device.prfSalt, enterpriseId);
// Derive enterprise-scoped salt (already base64url-encoded)
const prfSalt = deriveEnterpriseSalt(device.prfSalt, enterpriseId);

// Decrypt private key with existing passphrase
const privateKey = bitgo.decrypt({ password: existingPassphrase, input: keychain.encryptedPrv });
Expand All @@ -53,7 +53,7 @@ export async function attachPasskeyToWallet(params: {
publicKey: {
allowCredentials: [{ type: 'public-key', id: credentialIdBuffer }],
} as PublicKeyCredentialRequestOptions,
evalByCredential: { [device.credentialId]: enterpriseSalt },
evalByCredential: { [device.credentialId]: prfSalt },
});

if (!authResult.prfResult) {
Expand All @@ -64,20 +64,12 @@ export async function attachPasskeyToWallet(params: {
const prfPassword = derivePassword(authResult.prfResult);
const encryptedPrv = bitgo.encrypt({ password: prfPassword, input: privateKey });

// Convert enterpriseSalt from hex to base64url (URL-safe, no padding)
// as required by the server's prfSalt validation.
const prfSaltBase64url = Buffer.from(enterpriseSalt, 'hex')
.toString('base64')
.replace(/\+/g, '-')
.replace(/\//g, '_')
.replace(/=+$/, '');

// PUT webauthnInfo to keychain endpoint
const updatedKeychain = await bitgo
.put(bitgo.url(`/${coin}/key/${keychainId}`, 2))
.send({
webauthnInfo: {
prfSalt: prfSaltBase64url,
prfSalt,
otpDeviceId: device.id,
encryptedPrv,
},
Expand Down
10 changes: 6 additions & 4 deletions modules/passkey-crypto/src/deriveEnterpriseSalt.ts
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
import { createHmac } from 'crypto';
import * as sjcl from '@bitgo/sjcl';

/**
* Derives an enterprise-scoped PRF salt to prevent cross-enterprise key reuse.
Expand All @@ -8,9 +8,11 @@ import { createHmac } from 'crypto';
*
* @param baseSalt - Server-provided base64url-encoded PRF salt
* @param enterpriseId - Enterprise identifier
* @returns Hex-encoded HMAC-SHA256 digest
* @returns Base64url-encoded HMAC-SHA256 digest
*/
export function deriveEnterpriseSalt(baseSalt: string, enterpriseId: string): string {
const keyBytes = Buffer.from(baseSalt.replace(/-/g, '+').replace(/_/g, '/'), 'base64');
return createHmac('sha256', keyBytes).update(enterpriseId).digest('hex');
const keyBits = sjcl.codec.base64url.toBits(baseSalt);
const dataBits = sjcl.codec.utf8String.toBits(enterpriseId);
const resultBits = new sjcl.misc.hmac(keyBits, sjcl.hash.sha256).mac(dataBits);
return sjcl.codec.base64url.fromBits(resultBits);
}
6 changes: 3 additions & 3 deletions modules/passkey-crypto/test/unit/deriveEnterpriseSalt.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ import { deriveEnterpriseSalt } from '../../src';
const REAL_FIXTURE = {
basePrfSalt: 'ZqJ64M2dL65zn2-Jxd58SMN2ILc9QjbCFxUTGHd_LC8',
enterpriseId: '69c2aea1a3d7bc07f7f775c0ca86b0ec',
expectedDerivedSalt: 'a226ac3aace4bb2b84cfff34e37fb7217620852bb72d5e0dfdad4c2c8473994f',
expectedDerivedSalt: 'oiasOqzkuyuEz_8043-3IXYghSu3LV4N_a1MLIRzmU8',
};

describe('deriveEnterpriseSalt', function () {
Expand Down Expand Up @@ -37,10 +37,10 @@ describe('deriveEnterpriseSalt', function () {
assert.notStrictEqual(saltA, saltB);
});

it('returns a non-empty hex string', function () {
it('returns a non-empty base64url string', function () {
const result = deriveEnterpriseSalt(REAL_FIXTURE.basePrfSalt, REAL_FIXTURE.enterpriseId);
assert.strictEqual(typeof result, 'string');
assert.ok(result.length > 0);
assert.match(result, /^[0-9a-f]{64}$/);
assert.match(result, /^[A-Za-z0-9_-]+$/);
});
});
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