keyring_message: introduce EncryptWithOptions

crypto/encryption_option.go

@@ -0,0 +1,49 @@
+package crypto
+
+import (
+	"github.com/ProtonMail/go-crypto/openpgp/packet"
+	"github.com/ProtonMail/gopenpgp/v2/constants"
+)
+
+// EncryptionOption defines an interface to apply configurations to packet.Config
+type EncryptionOption interface {
+	apply(*packet.Config)
+}
+
+type configFunc func(*packet.Config)
+
+func (f configFunc) apply(cfg *packet.Config) {
+	f(cfg)
+}
+
+// WithDefault applies default settings for encryption
+func WithDefault() EncryptionOption {
+	return configFunc(func(config *packet.Config) {
+		config.DefaultCipher = packet.CipherAES256
+		config.DefaultCompressionAlgo = constants.DefaultCompression
+		config.CompressionConfig = &packet.CompressionConfig{Level: constants.DefaultCompressionLevel}
+	})
+}
+
+// WithCompression allows None, Zip or Zlib compression algorithms and sets compression level
+func WithCompression(compressionAlgo packet.CompressionAlgo,
+	compressionConfig *packet.CompressionConfig) EncryptionOption {
+	return configFunc(func(config *packet.Config) {
+		config.DefaultCompressionAlgo = compressionAlgo
+		config.CompressionConfig = compressionConfig
+	})
+}
+
+// WithCipher allows Cipher3DES, CipherCAST5, CipherAES128, CipherAES192, CipherAES256 ciphers to be set
+func WithCipher(cipher packet.CipherFunction) EncryptionOption {
+	return configFunc(func(config *packet.Config) {
+		config.DefaultCipher = cipher
+	})
+}
+
+// WithSigningContext defines signing context in encryption configuration
+func WithSigningContext(signingContext *SigningContext) EncryptionOption {
+	return configFunc(func(config *packet.Config) {
+		config.SignatureNotations = append(config.SignatureNotations, signingContext.getNotation())
+	})
+}

crypto/keyring_message.go

@@ -46,6 +46,15 @@ func (keyRing *KeyRing) EncryptWithContextAndCompression(message *PlainMessage,
 	return asymmetricEncrypt(message, keyRing, privateKey, true, signingContext)
 }
 
+// EncryptWithOptions encrypts a PlainMessage to PGPMessage using public/private keys.
+// * message : The plain data as a PlainMessage.
+// * privateKey : (optional) an unlocked private keyring to include signature in the message.
+// * opts : (optional) options to specify compression type and signing context.
+// * output  : The encrypted data as PGPMessage.
+func (keyRing *KeyRing) EncryptWithOptions(message *PlainMessage, privateKey *KeyRing, opts ...EncryptionOption) (*PGPMessage, error) {
+	return asymmetricEncrypt(message, keyRing, privateKey, false, nil, opts...)
+}
+
 // Decrypt decrypts encrypted string using pgp keys, returning a PlainMessage
 // * message    : The encrypted input as a PGPMessage
 // * verifyKey  : Public key for signature verification (optional)
@@ -201,6 +210,7 @@ func asymmetricEncrypt(
 	publicKey, privateKey *KeyRing,
 	compress bool,
 	signingContext *SigningContext,
+	opts ...EncryptionOption,
 ) (*PGPMessage, error) {
 	var outBuf bytes.Buffer
 	var encryptWriter io.WriteCloser
@@ -212,7 +222,7 @@ func asymmetricEncrypt(
 		ModTime:  plainMessage.getFormattedTime(),
 	}
 
-	encryptWriter, err = asymmetricEncryptStream(hints, &outBuf, &outBuf, publicKey, privateKey, compress, signingContext)
+	encryptWriter, err = asymmetricEncryptStream(hints, &outBuf, &outBuf, publicKey, privateKey, compress, signingContext, opts...)
 	if err != nil {
 		return nil, err
 	}
@@ -238,6 +248,7 @@ func asymmetricEncryptStream(
 	publicKey, privateKey *KeyRing,
 	compress bool,
 	signingContext *SigningContext,
+	opts ...EncryptionOption,
 ) (encryptWriter io.WriteCloser, err error) {
 	config := &packet.Config{
 		DefaultCipher: packet.CipherAES256,
@@ -253,6 +264,11 @@ func asymmetricEncryptStream(
 		config.SignatureNotations = append(config.SignatureNotations, signingContext.getNotation())
 	}
 
+	// Overwrite defaults if EncryptionOptions are provided
+	for _, opt := range opts {
+		opt.apply(config)
+	}
+
 	var signEntity *openpgp.Entity
 	if privateKey != nil && len(privateKey.entities) > 0 {
 		var err error

crypto/keyring_message_test.go

@@ -4,6 +4,8 @@ import (
 	"io/ioutil"
 	"testing"
 
+	"github.com/ProtonMail/go-crypto/openpgp/packet"
+	"github.com/ProtonMail/gopenpgp/v2/constants"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -78,3 +80,27 @@ func TestTextMessageEncryptionWithSignatureAndContextAndCompression(t *testing.T
 	}
 	assert.Exactly(t, message.GetString(), decrypted.GetString())
 }
+
+func TestTextMessageEncryptionWithOptions(t *testing.T) {
+	var message = NewPlainMessageFromString("plain text")
+	var testContext = "test-context"
+
+	ciphertext, err := keyRingTestPublic.EncryptWithOptions(message, keyRingTestPrivate,
+		WithCompression(packet.CompressionZIP, &packet.CompressionConfig{Level: constants.DefaultCompressionLevel}),
+		WithCipher(packet.CipherAES256),
+		WithSigningContext(NewSigningContext(testContext, true)))
+	if err != nil {
+		t.Fatal("Expected no error when encrypting, got:", err)
+	}
+
+	decrypted, err := keyRingTestPrivate.DecryptWithContext(
+		ciphertext,
+		keyRingTestPublic,
+		GetUnixTime(),
+		NewVerificationContext(testContext, true, 0),
+	)
+	if err != nil {
+		t.Fatal("Expected no error when decrypting, got:", err)
+	}
+	assert.Exactly(t, message.GetString(), decrypted.GetString())
+}