func (alg *AesGcm) Decrypt(aad, cek, iv, cipherText, authTag []byte) (plainText []byte, err error) {
cekSizeBits := len(cek) << 3
if cekSizeBits != alg.keySizeBits {
return nil, errors.New(fmt.Sprintf("AesGcm.Decrypt(): expected key of size %v bits, but was given %v bits.", alg.keySizeBits, cekSizeBits))
}
var block cipher.Block
if block, err = aes.NewCipher(cek); err != nil {
return nil, err
}
var aesgcm cipher.AEAD
if aesgcm, err = cipher.NewGCM(block); err != nil {
return nil, err
}
cipherWithTag := append(cipherText, authTag...)
if plainText, err = aesgcm.Open(nil, iv, cipherWithTag, aad); err != nil {
return nil, err
}
return plainText, nil
}
// Decrypts a proto using an AEAD. Unmarshals the result into dst. The result
// should only be considered written if this function returns true.
func DecryptProto(aead cipher.AEAD, msg string, additionalData []byte, dst proto.Message) bool {
msgBytes, err := base64.RawURLEncoding.DecodeString(msg)
if err != nil {
glog.V(2).Infof("Tried to decrypt proto with invalid base64: %v", err)
return false
}
var msgProto pb.EncryptedMessage
err = proto.Unmarshal(msgBytes, &msgProto)
if err != nil {
glog.V(2).Infof("Tried to decrypt proto with invalid pb.EncryptedMessage: %v", err)
return false
}
// Decrypt in-place.
plaintext := msgProto.Ciphertext
plaintext, err = aead.Open(plaintext[:0], msgProto.Nonce, msgProto.Ciphertext, additionalData)
if err != nil {
glog.V(2).Infof("Failed to decrypt data: %v", err)
return false
}
err = proto.Unmarshal(plaintext, dst)
if err != nil {
glog.V(2).Infof("Failed to decrypt proto: %v", err)
return false
}
return true
}
func (alg *AesGcmKW) Unwrap(encryptedCek []byte, key interface{}, cekSizeBits int, header map[string]interface{}) (cek []byte, err error) {
if kek, ok := key.([]byte); ok {
kekSizeBits := len(kek) << 3
if kekSizeBits != alg.keySizeBits {
return nil, errors.New(fmt.Sprintf("AesGcmKW.Unwrap(): expected key of size %v bits, but was given %v bits.", alg.keySizeBits, kekSizeBits))
}
var iv, tag string
if iv, ok = header["iv"].(string); !ok {
return nil, errors.New("AesGcmKW.Unwrap(): expected 'iv' param in JWT header, but was not found.")
}
if tag, ok = header["tag"].(string); !ok {
return nil, errors.New("AesGcmKW.Unwrap(): expected 'tag' param in JWT header, but was not found.")
}
var ivBytes, tagBytes []byte
if ivBytes, err = base64url.Decode(iv); err != nil {
return nil, err
}
if tagBytes, err = base64url.Decode(tag); err != nil {
return nil, err
}
var block cipher.Block
if block, err = aes.NewCipher(kek); err != nil {
return nil, err
}
var aesgcm cipher.AEAD
if aesgcm, err = cipher.NewGCM(block); err != nil {
return nil, err
}
cipherAndTag := append(encryptedCek, tagBytes...)
if cek, err = aesgcm.Open(nil, ivBytes, cipherAndTag, nil); err != nil {
fmt.Printf("err = %v\n", err)
return nil, err
}
return cek, nil
}
return nil, errors.New("AesGcmKW.Unwrap(): expected key to be '[]byte' array")
}
// decrypt is used to decrypt a value
func (b *AESGCMBarrier) decrypt(gcm cipher.AEAD, cipher []byte) ([]byte, error) {
// Verify the epoch
if cipher[0] != 0 || cipher[1] != 0 || cipher[2] != 0 || cipher[3] != keyEpoch {
return nil, fmt.Errorf("epoch mis-match")
}
// Verify the version byte
if cipher[4] != aesgcmVersionByte {
return nil, fmt.Errorf("version bytes mis-match")
}
// Capture the parts
nonce := cipher[5 : 5+gcm.NonceSize()]
raw := cipher[5+gcm.NonceSize():]
out := make([]byte, 0, len(raw)-gcm.NonceSize())
// Attempt to open
return gcm.Open(out, nonce, raw, nil)
}
// decrypt is used to decrypt a value
func (b *AESGCMBarrier) decrypt(gcm cipher.AEAD, cipher []byte) ([]byte, error) {
// Verify the term is always just one
term := binary.BigEndian.Uint32(cipher[:4])
if term != initialKeyTerm {
return nil, fmt.Errorf("term mis-match")
}
// Verify the version byte
if cipher[4] != aesgcmVersionByte {
return nil, fmt.Errorf("version bytes mis-match")
}
// Capture the parts
nonce := cipher[5 : 5+gcm.NonceSize()]
raw := cipher[5+gcm.NonceSize():]
out := make([]byte, 0, len(raw)-gcm.NonceSize())
// Attempt to open
return gcm.Open(out, nonce, raw, nil)
}
// decrypt is used to decrypt a value
func (b *AESGCMBarrier) decrypt(path string, gcm cipher.AEAD, cipher []byte) ([]byte, error) {
// Verify the term is always just one
term := binary.BigEndian.Uint32(cipher[:4])
if term != initialKeyTerm {
return nil, fmt.Errorf("term mis-match")
}
// Capture the parts
nonce := cipher[5 : 5+gcm.NonceSize()]
raw := cipher[5+gcm.NonceSize():]
out := make([]byte, 0, len(raw)-gcm.NonceSize())
// Verify the cipher byte and attempt to open
switch cipher[4] {
case AESGCMVersion1:
return gcm.Open(out, nonce, raw, nil)
case AESGCMVersion2:
return gcm.Open(out, nonce, raw, []byte(path))
default:
return nil, fmt.Errorf("version bytes mis-match")
}
}
func getErrData(aead cipher.AEAD, stream io.Reader) (string, ErrData) {
// Decode encrypted error from STDIN (json base64 gob)
var api APIErr
err := json.NewDecoder(stream).Decode(&api)
if err != nil {
panic(err)
}
rawdata, err := base64.StdEncoding.DecodeString(api.Data)
if err != nil {
panic(err)
}
rawdatabuf := bytes.NewBuffer(rawdata)
encdecoder := gob.NewDecoder(rawdatabuf)
var encerr EncryptedError
err = encdecoder.Decode(&encerr)
if err != nil {
panic(err)
}
errbytes, err := aead.Open(nil, encerr.Nonce, encerr.Ciphertext, nil)
if err != nil {
panic(err)
}
// Decode error struct from decrypted bytes
errbuf := bytes.NewBuffer(errbytes)
errdecoder := gob.NewDecoder(errbuf)
var errdata ErrData
err = errdecoder.Decode(&errdata)
if err != nil {
panic(err)
}
return api.Status, errdata
}
/*
Decrypt decrypts a literal of the form <b64URLmetadata>.<b64URLciphertext>.<b64URLnonce> given an AEAD cipher and
produces a metadata and data string.
*/
func Decrypt(aeadCipher cipher.AEAD, literal string) (string, string, error) {
var (
literalSubStrings []string
metadata []byte
ciphertext []byte
nonce []byte
data []byte
err error
)
//Split the literal into its base64 encoded metadata, ciphertext and nonce components
literalSubStrings = strings.Split(literal, ".")
if len(literalSubStrings) != 3 {
return "", "", fmt.Errorf("Bad AEAD Literal: %v\n", literal)
}
//Decode the metadata, ciphertext and nonce
metadata, err = base64.URLEncoding.DecodeString(literalSubStrings[0])
if err != nil {
return "", "", fmt.Errorf("Decode metadata failed: %v\n", literal)
}
ciphertext, err = base64.URLEncoding.DecodeString(literalSubStrings[1])
if err != nil {
return "", "", fmt.Errorf("Decode ciphertext failed: %v\n", literal)
}
nonce, err = base64.URLEncoding.DecodeString(literalSubStrings[2])
if err != nil {
return "", "", fmt.Errorf("Decode nonce failed: %v\n", literal)
}
//Open validates the integrity of the metadata using the authentication code in the ciphertext
//and, if valid, decrypts the ciphertext
data, err = aeadCipher.Open(data, nonce, ciphertext, metadata)
if err != nil {
return "", "", err
}
return string(metadata), string(data), nil
}
