selfpass/crypto/gcm.go

61 lines
1.0 KiB
Go

package crypto
import (
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"errors"
"fmt"
"io"
)
func GCMEncrypt(key []byte, plaintext []byte) ([]byte, error) {
if len(key) != 32 {
return nil, fmt.Errorf("key is not 32 bytes")
}
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
gcm, err := cipher.NewGCM(block)
if err != nil {
return nil, err
}
nonce := make([]byte, gcm.NonceSize())
_, err = io.ReadFull(rand.Reader, nonce)
if err != nil {
return nil, err
}
return gcm.Seal(nonce, nonce, plaintext, nil), nil
}
func GCMDecrypt(key []byte, ciphertext []byte) ([]byte, error) {
if len(key) != 32 {
return nil, fmt.Errorf("key is not 32 bytes")
}
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
gcm, err := cipher.NewGCM(block)
if err != nil {
return nil, err
}
if len(ciphertext) < gcm.NonceSize() {
return nil, errors.New("malformed ciphertext")
}
return gcm.Open(nil,
ciphertext[:gcm.NonceSize()],
ciphertext[gcm.NonceSize():],
nil,
)
}