feat: Add getRandomBytes

packages/cryptography/CHANGELOG.md

@@ -9,11 +9,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
-- Initial release ([#10282](https://github.com/MetaMask/core/pull/10282), [#10431](https://github.com/MetaMask/core/pull/10431), [#10403](https://github.com/MetaMask/core/pull/10403), [#10468](https://github.com/MetaMask/core/pull/10468), [#10503](https://github.com/MetaMask/core/pull/10503))
+- Initial release ([#10282](https://github.com/MetaMask/core/pull/10282), [#10431](https://github.com/MetaMask/core/pull/10431), [#10403](https://github.com/MetaMask/core/pull/10403), [#10468](https://github.com/MetaMask/core/pull/10468), [#10503](https://github.com/MetaMask/core/pull/10503), [#10563](https://github.com/MetaMask/core/pull/10563))
   - Add `sha256`, `sha384`, and `sha512` functions for computing SHA digests
   - Add `hmacSha256`, `hmacSha384`, and `hmacSha512` functions for computing HMAC digests
   - Add `pbkdf2Sha256`, `pbkdf2Sha384`, and `pbkdf2Sha512` functions for key derivation
   - Add `hkdfSha256`, `hkdfSha384`, and `hkdfSha512` functions for key derivation
   - Add `getPublicKey` and `getSharedSecret` functions for X25519 key derivation exported via `@metamask/cryptography/x25519`
+  - Add `getRandomBytes` function for generating cryptographically secure random bytes
 
 [Unreleased]: https://github.com/MetaMask/core/

packages/cryptography/src/index.ts

@@ -1,5 +1,6 @@
 export * from './hkdf.js';
 export * from './hmac.js';
 export * from './pbkdf2.js';
+export * from './random.js';
 export * from './sha.js';
 export type * from './types.js';

packages/cryptography/src/random.test.ts

@@ -0,0 +1,31 @@
+import { getRandomBytes } from './random.js';
+
+describe('getRandomBytes', () => {
+  it('returns a Uint8Array of the requested length', () => {
+    const bytes = getRandomBytes(32);
+
+    expect(bytes).toBeInstanceOf(Uint8Array);
+    expect(bytes).toHaveLength(32);
+  });
+
+  it('fills the array using `crypto.getRandomValues`', () => {
+    const spy = jest
+      .spyOn(globalThis.crypto, 'getRandomValues')
+      .mockImplementation((array) => {
+        (array as Uint8Array).fill(0xab);
+        return array;
+      });
+
+    const bytes = getRandomBytes(4);
+
+    expect(spy).toHaveBeenCalledTimes(1);
+    expect(spy).toHaveBeenCalledWith(expect.any(Uint8Array));
+    expect(bytes).toStrictEqual(new Uint8Array([0xab, 0xab, 0xab, 0xab]));
+  });
+
+  it('throws if the length is zero', () => {
+    expect(() => getRandomBytes(0)).toThrow(
+      'Invalid length: Length must be greater than 0.',
+    );
+  });
+});

packages/cryptography/src/random.ts

@@ -0,0 +1,13 @@
+/**
+ * Generate random bytes using the platform's cryptographically secure pseudo-random number generator (CSPRNG).
+ *
+ * @param length - The number of random bytes to generate.
+ * @returns An `Uint8Array` of the provided length with random bytes.
+ * @throws If `length` is not greater than 0.
+ */
+export function getRandomBytes(length: number): Uint8Array {
+  if (length <= 0) {
+    throw new Error('Invalid length: Length must be greater than 0.');
+  }
+  return globalThis.crypto.getRandomValues(new Uint8Array(length));
+}