feat: Expand OpenPGP implementation

Expands the existing OpenPGP implementation to include a more complete set of features for handling PGP data.

- Adds support for signing and verifying detached signatures.
- Adds support for symmetric encryption using a passphrase.
- Includes tests for all new functionality.

pkg/crypt/crypt.go

@@ -201,3 +201,21 @@ func (s *Service) DecryptPGP(privateKey, ciphertext []byte) ([]byte, error) {
 	s.ensurePGP()
 	return s.pgp.Decrypt(privateKey, ciphertext)
 }
+
+// SignPGP creates a detached signature for a message.
+func (s *Service) SignPGP(privateKey, data []byte) ([]byte, error) {
+	s.ensurePGP()
+	return s.pgp.Sign(privateKey, data)
+}
+
+// VerifyPGP verifies a detached signature for a message.
+func (s *Service) VerifyPGP(publicKey, data, signature []byte) error {
+	s.ensurePGP()
+	return s.pgp.Verify(publicKey, data, signature)
+}
+
+// SymmetricallyEncryptPGP encrypts data with a passphrase.
+func (s *Service) SymmetricallyEncryptPGP(passphrase, data []byte) ([]byte, error) {
+	s.ensurePGP()
+	return s.pgp.SymmetricallyEncrypt(passphrase, data)
+}

pkg/crypt/std/pgp/pgp.go

@@ -107,3 +107,59 @@ func (s *Service) Decrypt(privateKey, ciphertext []byte) ([]byte, error) {
 
 	return plaintext, nil
 }
+
+// Sign creates a detached signature for a message.
+func (s *Service) Sign(privateKey, data []byte) ([]byte, error) {
+	privKeyReader := bytes.NewReader(privateKey)
+	keyring, err := openpgp.ReadArmoredKeyRing(privKeyReader)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read private key ring: %w", err)
+	}
+
+	signer := keyring[0]
+	if signer.PrivateKey == nil {
+		return nil, fmt.Errorf("private key not found in keyring")
+	}
+
+	buf := new(bytes.Buffer)
+	err = openpgp.ArmoredDetachSign(buf, signer, bytes.NewReader(data), nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to sign message: %w", err)
+	}
+
+	return buf.Bytes(), nil
+}
+
+// Verify verifies a detached signature for a message.
+func (s *Service) Verify(publicKey, data, signature []byte) error {
+	pubKeyReader := bytes.NewReader(publicKey)
+	keyring, err := openpgp.ReadArmoredKeyRing(pubKeyReader)
+	if err != nil {
+		return fmt.Errorf("failed to read public key ring: %w", err)
+	}
+
+	_, err = openpgp.CheckArmoredDetachedSignature(keyring, bytes.NewReader(data), bytes.NewReader(signature), nil)
+	if err != nil {
+		return fmt.Errorf("failed to verify signature: %w", err)
+	}
+
+	return nil
+}
+
+// SymmetricallyEncrypt encrypts data with a passphrase.
+func (s *Service) SymmetricallyEncrypt(passphrase, data []byte) ([]byte, error) {
+	buf := new(bytes.Buffer)
+	w, err := openpgp.SymmetricallyEncrypt(buf, passphrase, nil, nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create symmetric encryption writer: %w", err)
+	}
+	defer w.Close()
+
+	_, err = w.Write(data)
+	if err != nil {
+		return nil, fmt.Errorf("failed to write data to symmetric encryption writer: %w", err)
+	}
+	w.Close()
+
+	return buf.Bytes(), nil
+}

pkg/crypt/std/pgp/pgp_test.go

@@ -45,3 +45,41 @@ func TestService_Decrypt_Good(t *testing.T) {
 	require.NoError(t, err, "failed to decrypt data")
 	assert.Equal(t, data, decrypted, "decrypted data does not match original")
 }
+
+func TestService_Sign_Good(t *testing.T) {
+	s := NewService()
+	pub, priv, err := s.GenerateKeyPair("test", "test@test.com", "test")
+	require.NoError(t, err, "failed to generate key pair")
+	assert.NotNil(t, pub, "public key is nil")
+	assert.NotNil(t, priv, "private key is nil")
+
+	data := []byte("hello world")
+	signature, err := s.Sign(priv, data)
+	require.NoError(t, err, "failed to sign data")
+	assert.NotNil(t, signature, "signature is nil")
+}
+
+func TestService_Verify_Good(t *testing.T) {
+	s := NewService()
+	pub, priv, err := s.GenerateKeyPair("test", "test@test.com", "test")
+	require.NoError(t, err, "failed to generate key pair")
+	assert.NotNil(t, pub, "public key is nil")
+	assert.NotNil(t, priv, "private key is nil")
+
+	data := []byte("hello world")
+	signature, err := s.Sign(priv, data)
+	require.NoError(t, err, "failed to sign data")
+	assert.NotNil(t, signature, "signature is nil")
+
+	err = s.Verify(pub, data, signature)
+	require.NoError(t, err, "failed to verify signature")
+}
+
+func TestService_SymmetricallyEncrypt_Good(t *testing.T) {
+	s := NewService()
+	passphrase := []byte("hello world")
+	data := []byte("hello world")
+	encrypted, err := s.SymmetricallyEncrypt(passphrase, data)
+	require.NoError(t, err, "failed to encrypt data")
+	assert.NotNil(t, encrypted, "encrypted data is nil")
+}