/
aes256gcm.go
77 lines (67 loc) · 1.75 KB
/
aes256gcm.go
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package unlock
// based on https://gist.github.com/tscholl2/dc7dc15dc132ea70a98e8542fefffa28#file-aes-go
import (
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"crypto/sha256"
"golang.org/x/crypto/pbkdf2"
)
const (
bytesIV = 12
bytesSalt = 16
minKdfIterCount = 10000
)
func generateRandom(bytes int) ([]byte, error) {
generated := make([]byte, bytes)
_, err := rand.Read(generated)
return generated, err
}
func sha256sum(data []byte) []byte {
sum := sha256.Sum256(data)
return sum[:]
}
func deriveKey(passphrase []byte, salt []byte, kdfIterCount int) []byte {
if kdfIterCount < minKdfIterCount {
kdfIterCount = minKdfIterCount
}
return pbkdf2.Key(passphrase, salt, kdfIterCount, sha256.Size, sha256.New)
}
func createCipherGCM(key []byte) (cipher.AEAD, error) {
cipherBlock, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
return cipher.NewGCM(cipherBlock)
}
func encrypt(passphrase []byte, plaintext []byte, kdfIterCount int) ([]byte, error) {
salt, err := generateRandom(bytesSalt)
if err != nil {
return nil, err
}
key := deriveKey(passphrase, salt, kdfIterCount)
aesgcm, err := createCipherGCM(key)
if err != nil {
return nil, err
}
iv, err := generateRandom(bytesIV)
if err != nil {
return nil, err
}
ciphertext := aesgcm.Seal(nil, iv, plaintext, nil)
data := append(ciphertext, salt...)
data = append(iv, data...)
return data, nil
}
func decrypt(passphrase []byte, data []byte, kdfIterCount int) ([]byte, error) {
saltIdx := len(data) - bytesSalt
iv := data[:bytesIV]
ciphertext := data[bytesIV:saltIdx]
salt := data[saltIdx:]
key := deriveKey(passphrase, salt, kdfIterCount)
aesgcm, err := createCipherGCM(key)
if err != nil {
return nil, err
}
return aesgcm.Open(nil, iv, ciphertext, nil)
}