1 files changed, 93 insertions, 0 deletions
diff --git a/cryptfs/openssl_aead.go b/cryptfs/openssl_aead.go
new file mode 100644
index 0000000..02f50d8
--- /dev/null
+++ b/cryptfs/openssl_aead.go
@@ -0,0 +1,93 @@
+package cryptfs
+
+// Implements cipher.AEAD with OpenSSL backend
+
+import (
+	"bytes"
+	"github.com/spacemonkeygo/openssl"
+)
+
+type opensslGCM struct {
+	key [16]byte
+}
+
+func (be opensslGCM) Overhead() int {
+	return AUTH_TAG_LEN
+}
+
+func (be opensslGCM) NonceSize() int {
+	return NONCE_LEN
+}
+
+// Seal encrypts and authenticates plaintext, authenticates the
+// additional data and appends the result to dst, returning the updated
+// slice. The nonce must be NonceSize() bytes long and unique for all
+// time, for a given key.
+//
+// The plaintext and dst may alias exactly or not at all.
+func (be opensslGCM) Seal(dst, nonce, plaintext, data []byte) []byte {
+
+	cipherBuf := bytes.NewBuffer(dst)
+
+	ectx, err := openssl.NewGCMEncryptionCipherCtx(128, nil, be.key[:], nonce[:])
+	if err != nil {
+		panic(err)
+	}
+	part, err := ectx.EncryptUpdate(plaintext)
+	if err != nil {
+		panic(err)
+	}
+	cipherBuf.Write(part)
+	part, err = ectx.EncryptFinal()
+	if err != nil {
+		panic(err)
+	}
+	cipherBuf.Write(part)
+	part, err = ectx.GetTag()
+	if err != nil {
+		panic(err)
+	}
+	cipherBuf.Write(part)
+
+	return cipherBuf.Bytes()
+}
+
+// Open decrypts and authenticates ciphertext, authenticates the
+// additional data and, if successful, appends the resulting plaintext
+// to dst, returning the updated slice. The nonce must be NonceSize()
+// bytes long and both it and the additional data must match the
+// value passed to Seal.
+//
+// The ciphertext and dst may alias exactly or not at all.
+func (be opensslGCM) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
+
+	if len(data) > 0 {
+		panic("Extra data is not supported")
+	}
+
+	l := len(ciphertext)
+	tag := ciphertext[l-AUTH_TAG_LEN:l]
+	ciphertext = ciphertext[0:l-AUTH_TAG_LEN]
+	plainBuf := bytes.NewBuffer(dst)
+
+	dctx, err := openssl.NewGCMDecryptionCipherCtx(128, nil, be.key[:], nonce[:])
+	if err != nil {
+		return nil, err
+	}
+	part, err := dctx.DecryptUpdate(ciphertext)
+	if err != nil {
+		return nil, err
+	}
+	plainBuf.Write(part)
+	err = dctx.SetTag(tag)
+	if err != nil {
+		return nil, err
+	}
+	part, err = dctx.DecryptFinal()
+	if err != nil {
+		return nil, err
+	}
+	plainBuf.Write(part)
+
+	return plainBuf.Bytes(), nil
+}