feat(shared): seal/open user private key with PIN-derived Argon2id KEK

packages/shared/src/crypto/userKey.test.ts

@@ -0,0 +1,51 @@
+import { describe, expect, it, beforeAll } from 'vitest';
+
+import { setCryptoBackend } from './backend';
+import { makeWasmTestBackend } from './testBackend';
+import { generateUserKeyPair, sealUserKey, openUserKey, KDF_PRESET } from './userKey';
+
+beforeAll(async () => { setCryptoBackend(await makeWasmTestBackend()); });
+
+describe('userKey', () => {
+  it('generates a 32-byte X25519 keypair', async () => {
+    const kp = await generateUserKeyPair();
+    expect(kp.publicKey).toHaveLength(32);
+    expect(kp.privateKey).toHaveLength(32);
+  });
+
+  it('seals and opens a private key with the same PIN', async () => {
+    const kp = await generateUserKeyPair();
+    const sealed = await sealUserKey({ privateKey: kp.privateKey, pin: '123456' });
+    const opened = await openUserKey({
+      sealed: sealed.sealedPrivateKey,
+      pin: '123456',
+      salt: sealed.salt,
+      kdfParams: sealed.kdfParams,
+    });
+    expect(Array.from(opened)).toEqual(Array.from(kp.privateKey));
+  });
+
+  it('throws when opening with the wrong PIN', async () => {
+    const kp = await generateUserKeyPair();
+    const sealed = await sealUserKey({ privateKey: kp.privateKey, pin: '123456' });
+    await expect(
+      openUserKey({ sealed: sealed.sealedPrivateKey, pin: '654321', salt: sealed.salt, kdfParams: sealed.kdfParams }),
+    ).rejects.toThrow();
+  });
+
+  it('throws when opening with the wrong salt', async () => {
+    const kp = await generateUserKeyPair();
+    const sealed = await sealUserKey({ privateKey: kp.privateKey, pin: '123456' });
+    const wrongSalt = new Uint8Array(sealed.salt.length); wrongSalt.fill(7);
+    await expect(
+      openUserKey({ sealed: sealed.sealedPrivateKey, pin: '123456', salt: wrongSalt, kdfParams: sealed.kdfParams }),
+    ).rejects.toThrow();
+  });
+
+  it('emits the documented KDF preset', async () => {
+    const kp = await generateUserKeyPair();
+    const sealed = await sealUserKey({ privateKey: kp.privateKey, pin: '123456' });
+    expect(sealed.kdfParams.algo).toBe('argon2id');
+    expect(sealed.kdfParams.preset).toBe(KDF_PRESET);
+  });
+});