feat(extension): add SSH SHA256 fingerprint util (webcrypto)

extension/src/shared/__tests__/ssh-fingerprint.test.ts

@@ -0,0 +1,30 @@
+import { describe, it, expect } from 'vitest';
+import { sshFingerprint } from '../ssh-fingerprint';
+
+describe('sshFingerprint', () => {
+  it('formats a known ed25519 key to SHA256:<b64>', async () => {
+    // Public key for the seed below — same format `relicario device list` prints.
+    // Pre-computed: SHA256 of the base64-decoded key blob, base64-no-pad encoded.
+    const key = 'ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIN8wRgr7y2BwnIaUMfqCcW8GZTYCmGoiCQ0c3VwYTtVZ alice@example';
+    const fp = await sshFingerprint(key);
+    expect(fp).toMatch(/^SHA256:[A-Za-z0-9+/]+$/);
+    expect(fp?.includes('=')).toBe(false);
+  });
+
+  it('returns null for malformed input', async () => {
+    expect(await sshFingerprint('')).toBeNull();
+    expect(await sshFingerprint('not a key')).toBeNull();
+    expect(await sshFingerprint('ssh-ed25519')).toBeNull(); // missing blob
+  });
+
+  it('returns null for invalid base64', async () => {
+    expect(await sshFingerprint('ssh-ed25519 !!!notbase64!!!')).toBeNull();
+  });
+
+  it('is deterministic for the same key', async () => {
+    const key = 'ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIN8wRgr7y2BwnIaUMfqCcW8GZTYCmGoiCQ0c3VwYTtVZ';
+    const a = await sshFingerprint(key);
+    const b = await sshFingerprint(key);
+    expect(a).toBe(b);
+  });
+});