func (alg *AesGcm) Encrypt(aad, plainText, cek []byte) (iv, cipherText, authTag []byte, err error) {
cekSizeBits := len(cek) << 3
if cekSizeBits != alg.keySizeBits {
return nil, nil, nil, errors.New(fmt.Sprintf("AesGcm.Encrypt(): expected key of size %v bits, but was given %v bits.", alg.keySizeBits, cekSizeBits))
}
if iv, err = arrays.Random(12); err != nil {
return nil, nil, nil, err
}
var block cipher.Block
if block, err = aes.NewCipher(cek); err != nil {
return nil, nil, nil, err
}
var aesgcm cipher.AEAD
if aesgcm, err = cipher.NewGCM(block); err != nil {
return nil, nil, nil, err
}
cipherWithTag := aesgcm.Seal(nil, iv, plainText, aad)
cipherText = cipherWithTag[:len(cipherWithTag)-aesgcm.Overhead()]
authTag = cipherWithTag[len(cipherWithTag)-aesgcm.Overhead():]
return iv, cipherText, authTag, nil
}
// encrypt is used to encrypt a value
func (b *AESGCMBarrier) encrypt(path string, term uint32, gcm cipher.AEAD, plain []byte) []byte {
// Allocate the output buffer with room for tern, version byte,
// nonce, GCM tag and the plaintext
capacity := termSize + 1 + gcm.NonceSize() + gcm.Overhead() + len(plain)
size := termSize + 1 + gcm.NonceSize()
out := make([]byte, size, capacity)
// Set the key term
binary.BigEndian.PutUint32(out[:4], term)
// Set the version byte
out[4] = b.currentAESGCMVersionByte
// Generate a random nonce
nonce := out[5 : 5+gcm.NonceSize()]
rand.Read(nonce)
// Seal the output
switch b.currentAESGCMVersionByte {
case AESGCMVersion1:
out = gcm.Seal(out, nonce, plain, nil)
case AESGCMVersion2:
out = gcm.Seal(out, nonce, plain, []byte(path))
default:
panic("Unknown AESGCM version")
}
return out
}
func (alg *AesGcmKW) WrapNewKey(cekSizeBits int, key interface{}, header map[string]interface{}) (cek []byte, encryptedCek []byte, err error) {
if kek, ok := key.([]byte); ok {
kekSizeBits := len(kek) << 3
if kekSizeBits != alg.keySizeBits {
return nil, nil, errors.New(fmt.Sprintf("AesGcmKW.WrapNewKey(): expected key of size %v bits, but was given %v bits.", alg.keySizeBits, kekSizeBits))
}
if cek, err = arrays.Random(cekSizeBits >> 3); err != nil {
return nil, nil, err
}
var iv []byte
if iv, err = arrays.Random(12); err != nil {
return nil, nil, err
}
var block cipher.Block
if block, err = aes.NewCipher(kek); err != nil {
return nil, nil, err
}
var aesgcm cipher.AEAD
if aesgcm, err = cipher.NewGCM(block); err != nil {
return nil, nil, err
}
cipherWithTag := aesgcm.Seal(nil, iv, cek, nil)
cipherText := cipherWithTag[:len(cipherWithTag)-aesgcm.Overhead()]
authTag := cipherWithTag[len(cipherWithTag)-aesgcm.Overhead():]
header["iv"] = base64url.Encode(iv)
header["tag"] = base64url.Encode(authTag)
return cek, cipherText, nil
}
return nil, nil, errors.New("AesGcmKW.WrapNewKey(): expected key to be '[]byte' array")
}
// encrypt is used to encrypt a value
func (b *AESGCMBarrier) encrypt(term uint32, gcm cipher.AEAD, plain []byte) []byte {
// Allocate the output buffer with room for tern, version byte,
// nonce, GCM tag and the plaintext
capacity := termSize + 1 + gcm.NonceSize() + gcm.Overhead() + len(plain)
size := termSize + 1 + gcm.NonceSize()
out := make([]byte, size, capacity)
// Set the key term
binary.BigEndian.PutUint32(out[:4], term)
// Set the version byte
out[4] = aesgcmVersionByte
// Generate a random nonce
nonce := out[5 : 5+gcm.NonceSize()]
rand.Read(nonce)
// Seal the output
out = gcm.Seal(out, nonce, plain, nil)
return out
}
// encrypt is used to encrypt a value
func (b *AESGCMBarrier) encrypt(gcm cipher.AEAD, plain []byte) []byte {
// Allocate the output buffer with room for epoch, version byte,
// nonce, GCM tag and the plaintext
capacity := epochSize + 1 + gcm.NonceSize() + gcm.Overhead() + len(plain)
size := epochSize + 1 + gcm.NonceSize()
out := make([]byte, size, capacity)
// Set the epoch to 1
out[3] = keyEpoch
// Set the version byte
out[4] = aesgcmVersionByte
// Generate a random nonce
nonce := out[5 : 5+gcm.NonceSize()]
rand.Read(nonce)
// Seal the output
out = gcm.Seal(out, nonce, plain, nil)
return out
}
