feat: implement memzero helper function

README.md

@@ -87,6 +87,7 @@ import {
   crypto_sign_SEEDBYTES,
   crypto_sign_verify_detached,
   from_base64,
+  memzero,
   randombytes_buf,
   randombytes_uniform,
   to_base64,

example/src/components/TestResults.tsx

@@ -27,6 +27,7 @@ import '../tests/crypto_sign_keypair_test';
 import '../tests/crypto_sign_seed_keypair_test';
 import '../tests/crypto_sign_verify_detached_test';
 import '../tests/from_base64_test';
+import '../tests/memzero_test';
 import '../tests/randombytes_buf_test';
 import '../tests/randombytes_uniform_test';
 import '../tests/to_base64_test';

example/src/tests/memzero_test.ts

@@ -0,0 +1,10 @@
+import { memzero, to_hex } from 'react-native-libsodium';
+import { expect, test } from '../utils/testRunner';
+
+test('memzero', () => {
+  let buf = new Uint8Array([222, 173, 190, 239]);
+  memzero(buf);
+  expect(to_hex(buf)).toBe('00000000');
+
+  expect(() => memzero([0, 1, 2, 3] as unknown as Uint8Array)).toThrow();
+});

src/lib.native.ts

@@ -251,6 +251,15 @@ export function to_hex(input: string | Uint8Array): string {
   return global.jsi_to_hex(inputParam);
 }
 
+export function memzero(bytes: Uint8Array): void {
+  if (!(bytes instanceof Uint8Array)) {
+    throw new TypeError('Only Uint8Array instances can be wiped');
+  }
+  for (let i = 0; i < bytes.length; i++) {
+    bytes[i] = 0;
+  }
+}
+
 export function randombytes_buf(
   length: number,
   outputFormat?: Uint8ArrayOutputFormat | null
@@ -889,6 +898,7 @@ export default {
   crypto_sign_keypair,
   crypto_sign_verify_detached,
   from_base64,
+  memzero,
   randombytes_buf,
   randombytes_uniform,
   ready,