Merge pull request #9508 from BitGo/pranavjain/wcn-43-remove-sjcl-decrypt-pr1

feat(sdk-api): SJCL-free v1 decrypt with temp fallback

Author: pranavjain97

modules/sdk-api/package.json

@@ -58,6 +58,9 @@
     "secrets.js-grempe": "^1.1.0",
     "superagent": "^9.0.1"
   },
+  "devDependencies": {
+    "crypto-browserify": "^3.12.0"
+  },
   "overrides": {
     "degenerator": "5.0.0"
   },

modules/sdk-api/src/bitgoAPI.ts

@@ -874,7 +874,8 @@ export class BitGoAPI implements BitGoBase {
     } catch (error) {
       if (
         error.message.includes("ccm: tag doesn't match") ||
-        error.message.includes('The operation failed for an operation-specific reason')
+        error.message.includes('The operation failed for an operation-specific reason') ||
+        error.message.includes('Unsupported state or unable to authenticate data')
       ) {
         throw new Error('incorrect password');
       }

modules/sdk-api/src/decryptV1.ts

@@ -0,0 +1,119 @@
+import { base64String, boundedInt, decodeWithCodec } from '@bitgo/sdk-core';
+import { createDecipheriv, pbkdf2 } from 'crypto';
+import * as t from 'io-ts';
+import { promisify } from 'util';
+
+/**
+ * Minimal shape the decrypt path needs from a crypto module. Both `node:crypto`
+ * and `crypto-browserify` satisfy this. Passing this in from tests lets the
+ * browser-shim test suite exercise the real decrypt code instead of a copy.
+ */
+export interface CryptoModule {
+  pbkdf2: typeof pbkdf2;
+  createDecipheriv: typeof createDecipheriv;
+}
+
+const defaultCrypto: CryptoModule = { pbkdf2, createDecipheriv };
+
+/**
+ * Upper bound on PBKDF2 iterations accepted from a v1 envelope. BitGo-produced
+ * v1 envelopes use 10,000; this cap is 10x that. Envelope validation enforces
+ * it up front before any KDF work runs.
+ */
+export const V1_MAX_ITER = 100_000;
+
+/**
+ * io-ts codec for a v1 (SJCL) envelope.
+ *
+ * Enforces the shape and the `iter` cap up front, before any KDF work runs.
+ */
+const V1EnvelopeCodec = t.intersection([
+  t.type({
+    v: t.literal(1),
+    iter: boundedInt(1, V1_MAX_ITER, 'iter'),
+    ks: t.union([t.literal(128), t.literal(256)]),
+    ts: t.union([t.literal(64), t.literal(96), t.literal(128)]),
+    mode: t.literal('ccm'),
+    cipher: t.literal('aes'),
+    salt: base64String,
+    iv: base64String,
+    ct: base64String,
+  }),
+  t.partial({
+    adata: t.string,
+  }),
+]);
+
+export type V1Envelope = t.TypeOf<typeof V1EnvelopeCodec>;
+
+export function parseV1Envelope(ciphertext: string): V1Envelope {
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(ciphertext);
+  } catch {
+    throw new Error('v1 decrypt: invalid JSON envelope');
+  }
+  return decodeWithCodec(V1EnvelopeCodec, parsed, 'v1 decrypt: invalid envelope');
+}
+
+/**
+ * CCM length field size L, in bytes, chosen to encode the plaintext length.
+ *
+ * SJCL picks the smallest L in [2, 4) that can represent the plaintext length,
+ * then derives the nonce length as (15 - L). We mirror that so Node's CCM
+ * uses the same nonce framing as the SJCL encoder produced.
+ */
+function ccmNonceLength(plaintextLen: number): number {
+  let L = 2;
+  while (L < 4 && plaintextLen >= Math.pow(2, 8 * L)) L++;
+  return 15 - L;
+}
+
+/**
+ * Decrypt a parsed v1 envelope given a crypto module.
+ *
+ * v1 = PBKDF2-SHA256(password, salt, iter, keyLen) then AES-CCM(key, nonce, ct||tag).
+ * Byte-for-byte compatible with `sjcl.decrypt` output for the same envelope.
+ *
+ * Exported so tests can inject `crypto-browserify` and exercise the exact
+ * runtime path the webpack browser bundle produces, without duplicating the
+ * decrypt logic.
+ */
+export async function decryptV1WithCrypto(password: string, ciphertext: string, crypto: CryptoModule): Promise<string> {
+  const env = parseV1Envelope(ciphertext);
+  const salt = Buffer.from(env.salt, 'base64');
+  const ivFull = Buffer.from(env.iv, 'base64');
+  const full = Buffer.from(env.ct, 'base64');
+  const tagBytes = env.ts / 8;
+  if (full.length < tagBytes) throw new Error('v1 decrypt: ciphertext shorter than tag');
+
+  const cipher = full.subarray(0, full.length - tagBytes);
+  const authTag = full.subarray(full.length - tagBytes);
+  const nonceLen = ccmNonceLength(cipher.length);
+  if (ivFull.length < nonceLen) throw new Error('v1 decrypt: iv shorter than nonce');
+  const iv = ivFull.subarray(0, nonceLen);
+
+  const keyBytes = env.ks / 8;
+  const key: Buffer = await promisify(crypto.pbkdf2)(password, salt, env.iter, keyBytes, 'sha256');
+
+  const decipher = crypto.createDecipheriv(`aes-${env.ks}-ccm`, key, iv, { authTagLength: tagBytes });
+  decipher.setAuthTag(authTag);
+  const aad = env.adata ? Buffer.from(env.adata, 'utf8') : Buffer.alloc(0);
+  decipher.setAAD(aad, { plaintextLength: cipher.length });
+
+  const pt = Buffer.concat([decipher.update(cipher), decipher.final()]);
+  return pt.toString('utf8');
+}
+
+/**
+ * Decrypt a v1 (SJCL PBKDF2-SHA256 + AES-CCM) envelope.
+ *
+ * Runs the same `node:crypto` code on server and browser. The BitGoJS webpack
+ * config already maps `crypto` -> `crypto-browserify`, whose `aes-256-ccm` and
+ * `pbkdf2` implementations are byte-compatible with Node's native ones and
+ * with SJCL's envelope format. Parity is guarded by tests in
+ * `test/unit/decryptV1.browser.ts`.
+ */
+export async function decryptV1(password: string, ciphertext: string): Promise<string> {
+  return decryptV1WithCrypto(password, ciphertext, defaultCrypto);
+}

modules/sdk-api/src/encrypt.ts

@@ -1,6 +1,7 @@
 import * as sjcl from '@bitgo/sjcl';
 import { randomBytes } from 'crypto';
 
+import { decryptV1 } from './decryptV1';
 import { decryptV2, encryptV2 } from './encryptV2';
 
 /**
@@ -65,15 +66,61 @@ export async function encrypt(
 }
 
 /**
- * Internal v1 (SJCL) decrypt helper. Not part of the public surface: callers use
- * the auto-detecting `decrypt` instead.
+ * Iter-cap violations are the only error we refuse to fall back on: SJCL has
+ * no upper bound on `iter`, so falling through to it would let a hostile
+ * envelope burn CPU running an inflated PBKDF2. Everything else -- codec
+ * rejection of a shape SJCL would accept, native crypto bug, auth-tag
+ * mismatch -- is safe to fall through to SJCL.
  */
-function decryptV1(password: string, ciphertext: string): string {
-  return sjcl.decrypt(password, ciphertext);
+function isIterCapViolation(err: unknown): boolean {
+  return err instanceof Error && /iter:\s*expected integer|iter out of range/i.test(err.message);
 }
 
 /**
- * Auto-detect v1 (SJCL) or v2 (Argon2id + AES-256-GCM) from the envelope `v` field and decrypt.
+ * v1 decrypt with an SJCL safety net.
+ *
+ * Design intent during rollout: zero false negatives. Any native failure
+ * (envelope shape our stricter codec rejects, framing bug, unsupported
+ * algorithm, auth-tag mismatch, etc.) falls through to `sjcl.decrypt` so the
+ * caller is never blocked. The only exception is an iter-cap violation,
+ * which is rethrown to preserve DoS protection.
+ *
+ * The console.warn only fires when native fails AND SJCL succeeds -- i.e.
+ * when the two engines disagree, which is the only signal worth
+ * investigating. Wrong password fails both engines silently and surfaces
+ * SJCL's auth error (mapped upstream to "incorrect password").
+ *
+ * `native` defaults to the module's `decryptV1` but is exposed as a parameter
+ * so tests can inject a throwing version to exercise the fallback path.
+ */
+export async function decryptV1WithFallback(
+  password: string,
+  ciphertext: string,
+  native: (pw: string, ct: string) => Promise<string> = decryptV1
+): Promise<string> {
+  try {
+    return await native(password, ciphertext);
+  } catch (nativeErr) {
+    if (isIterCapViolation(nativeErr)) throw nativeErr;
+    let result: string;
+    try {
+      result = sjcl.decrypt(password, ciphertext);
+    } catch (sjclErr) {
+      // Both engines rejected -- almost certainly a real auth failure.
+      // Rethrow SJCL's error so BitGoAPI.decrypt maps it to "incorrect password".
+      throw sjclErr;
+    }
+    // Native failed but SJCL succeeded -- real signal, log for the operator.
+    const message = nativeErr instanceof Error ? nativeErr.message : String(nativeErr);
+    // eslint-disable-next-line no-console
+    console.warn('[bitgo-sdk] v1 native decrypt failed; SJCL fallback succeeded:', message);
+    return result;
+  }
+}
+
+/**
+ * Auto-detect v1 (PBKDF2-SHA256 + AES-CCM) or v2 (Argon2id + AES-256-GCM)
+ * from the envelope `v` field and decrypt.
  */
 export async function decrypt(password: string, ciphertext: string): Promise<string> {
   let envelopeVersion: number | undefined;
@@ -90,5 +137,5 @@ export async function decrypt(password: string, ciphertext: string): Promise<str
   if (envelopeVersion !== undefined && envelopeVersion !== 1) {
     throw new Error(`decrypt: unknown envelope version ${envelopeVersion}`);
   }
-  return decryptV1(password, ciphertext);
+  return decryptV1WithFallback(password, ciphertext);
 }

modules/sdk-api/src/index.ts

@@ -1,5 +1,6 @@
 export * from './api';
 export * from './bitgoAPI';
+export * from './decryptV1';
 export * from './encrypt';
 export * from './encryptionSession';
 export * from './encryptV2';

modules/sdk-api/test/unit/decryptV1.browser.ts

@@ -0,0 +1,108 @@
+import * as sjcl from '@bitgo/sjcl';
+import assert from 'assert';
+
+import { decryptV1WithCrypto, V1_MAX_ITER } from '../../src';
+import { KEYCARD_BOX_A, KEYCARD_BOX_B, KEYCARD_PASSWORD, KEYCARD_PLAINTEXT_PREFIX } from './fixtures/keycard';
+// eslint-disable-next-line @typescript-eslint/no-var-requires
+const browserCrypto = require('crypto-browserify');
+
+/**
+ * sjcl.encrypt's typings require salt/iv, but the runtime picks them from
+ * sjcl.random when omitted. Feed real random words so the call type-checks
+ * without an `as` cast.
+ */
+function sjclEncrypt(password: string, plaintext: string, params: sjcl.SjclCipherParams): string {
+  const salt = sjcl.random.randomWords(2);
+  const iv = sjcl.random.randomWords(4);
+  return sjcl.encrypt(password, plaintext, { ...params, salt, iv });
+}
+
+/**
+ * Exercises the real `decryptV1WithCrypto` code path with `crypto-browserify`
+ * injected as the crypto module. This is exactly what webpack bundles for the
+ * browser (its `crypto` shim), so a green test here proves the browser build
+ * stays byte-compatible with SJCL-produced envelopes and the Node path.
+ */
+function decryptV1Browser(password: string, ciphertext: string): Promise<string> {
+  return decryptV1WithCrypto(password, ciphertext, browserCrypto);
+}
+
+describe('decryptV1 browser path (crypto-browserify shim)', () => {
+  const password = 'myPassword';
+  const plaintext = 'Hello, Browser!';
+
+  it('produces the same plaintext as sjcl.decrypt', async () => {
+    const ciphertext = sjclEncrypt(password, plaintext, { iter: 10000, ks: 256, ts: 64, mode: 'ccm' });
+    assert.strictEqual(await decryptV1Browser(password, ciphertext), sjcl.decrypt(password, ciphertext));
+  });
+
+  it('handles adata (AAD)', async () => {
+    const ciphertext = sjclEncrypt(password, plaintext, {
+      iter: 10000,
+      ks: 256,
+      ts: 64,
+      mode: 'ccm',
+      adata: 'ctx-A',
+    });
+    assert.strictEqual(await decryptV1Browser(password, ciphertext), plaintext);
+  });
+
+  it('handles UTF-8 password + plaintext', async () => {
+    const utf8Password = 'pässwörd中文🔐';
+    const utf8Plaintext = 'passphrase: 秘密キー ☃🔑';
+    const ciphertext = sjclEncrypt(utf8Password, utf8Plaintext, { iter: 10000, ks: 256, ts: 64, mode: 'ccm' });
+    assert.strictEqual(await decryptV1Browser(utf8Password, ciphertext), utf8Plaintext);
+  });
+
+  it('handles large plaintext (>64 KiB, forces L=3 nonce framing)', async () => {
+    const large = 'x'.repeat(70_000);
+    const ciphertext = sjclEncrypt(password, large, { iter: 1000, ks: 256, ts: 64, mode: 'ccm' });
+    assert.strictEqual(await decryptV1Browser(password, ciphertext), large);
+  });
+
+  it('handles aes-128 envelopes', async () => {
+    const ciphertext = sjclEncrypt(password, plaintext, { iter: 10000, ks: 128, ts: 64, mode: 'ccm' });
+    assert.strictEqual(await decryptV1Browser(password, ciphertext), plaintext);
+  });
+
+  it('handles 128-bit tag envelopes', async () => {
+    const ciphertext = sjclEncrypt(password, plaintext, { iter: 10000, ks: 256, ts: 128, mode: 'ccm' });
+    assert.strictEqual(await decryptV1Browser(password, ciphertext), plaintext);
+  });
+
+  it('rejects wrong password', async () => {
+    const ciphertext = sjclEncrypt(password, plaintext, { iter: 10000, ks: 256, ts: 64, mode: 'ccm' });
+    await assert.rejects(() => decryptV1Browser('wrongPassword', ciphertext));
+  });
+
+  it('rejects envelope with iter above cap before running PBKDF2', async () => {
+    const ciphertext = sjclEncrypt(password, plaintext, { iter: 10000, ks: 256, ts: 64, mode: 'ccm' });
+    const envelope = JSON.parse(ciphertext);
+    envelope.iter = V1_MAX_ITER + 1;
+    const start = Date.now();
+    await assert.rejects(() => decryptV1Browser(password, JSON.stringify(envelope)), /iter/);
+    assert.ok(Date.now() - start < 100, 'must reject before any KDF work');
+  });
+
+  it('parity across 50 randomised inputs', async () => {
+    const { randomBytes } = await import('crypto');
+    for (let i = 0; i < 50; i++) {
+      const pw = randomBytes(16).toString('hex');
+      const pt = randomBytes(1 + Math.floor(Math.random() * 500)).toString('base64');
+      const ciphertext = sjclEncrypt(pw, pt, { iter: 1000, ks: 256, ts: 64, mode: 'ccm' });
+      assert.strictEqual(await decryptV1Browser(pw, ciphertext), pt, `iteration ${i}`);
+    }
+  });
+
+  it('Box A + Box B: shim decrypt matches SJCL byte-for-byte', async () => {
+    for (const [label, ct] of [
+      ['A', KEYCARD_BOX_A],
+      ['B', KEYCARD_BOX_B],
+    ] as const) {
+      const sjclResult = sjcl.decrypt(KEYCARD_PASSWORD, ct);
+      const shimResult = await decryptV1Browser(KEYCARD_PASSWORD, ct);
+      assert.strictEqual(shimResult, sjclResult, `Box ${label} mismatch`);
+      assert.ok(shimResult.startsWith(KEYCARD_PLAINTEXT_PREFIX));
+    }
+  });
+});