80 lines
1.8 KiB
Go
80 lines
1.8 KiB
Go
package encryption
|
|
|
|
import (
|
|
"crypto/aes"
|
|
"crypto/cipher"
|
|
"crypto/rand"
|
|
"encoding/base64"
|
|
"fmt"
|
|
"io"
|
|
"strings"
|
|
)
|
|
|
|
const (
|
|
currentVersion byte = 1
|
|
keySize = 32
|
|
)
|
|
|
|
type Cipher struct {
|
|
gcm cipher.AEAD
|
|
}
|
|
|
|
func New(masterKey []byte) (Cipher, error) {
|
|
if len(masterKey) != keySize {
|
|
return Cipher{}, fmt.Errorf("master key must be %d bytes", keySize)
|
|
}
|
|
|
|
block, err := aes.NewCipher(masterKey)
|
|
if err != nil {
|
|
return Cipher{}, err
|
|
}
|
|
|
|
gcm, err := cipher.NewGCM(block)
|
|
if err != nil {
|
|
return Cipher{}, err
|
|
}
|
|
|
|
return Cipher{gcm: gcm}, nil
|
|
}
|
|
|
|
func NewFromBase64(encodedKey string) (Cipher, error) {
|
|
encodedKey = strings.TrimSpace(encodedKey)
|
|
if encodedKey == "" {
|
|
return Cipher{}, fmt.Errorf("MASTER_KEY_BASE64 is required")
|
|
}
|
|
|
|
key, err := base64.StdEncoding.DecodeString(encodedKey)
|
|
if err != nil {
|
|
return Cipher{}, fmt.Errorf("MASTER_KEY_BASE64 must be base64 encoded: %w", err)
|
|
}
|
|
|
|
return New(key)
|
|
}
|
|
|
|
func (c Cipher) Encrypt(plaintext []byte) ([]byte, error) {
|
|
nonce := make([]byte, c.gcm.NonceSize())
|
|
if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
ciphertext := make([]byte, 0, 1+len(nonce)+len(plaintext)+c.gcm.Overhead())
|
|
ciphertext = append(ciphertext, currentVersion)
|
|
ciphertext = append(ciphertext, nonce...)
|
|
ciphertext = c.gcm.Seal(ciphertext, nonce, plaintext, nil)
|
|
return ciphertext, nil
|
|
}
|
|
|
|
func (c Cipher) Decrypt(ciphertext []byte) ([]byte, error) {
|
|
nonceSize := c.gcm.NonceSize()
|
|
if len(ciphertext) < 1+nonceSize+c.gcm.Overhead() {
|
|
return nil, fmt.Errorf("ciphertext is too short")
|
|
}
|
|
if ciphertext[0] != currentVersion {
|
|
return nil, fmt.Errorf("unsupported ciphertext version")
|
|
}
|
|
|
|
nonce := ciphertext[1 : 1+nonceSize]
|
|
encrypted := ciphertext[1+nonceSize:]
|
|
return c.gcm.Open(nil, nonce, encrypted, nil)
|
|
}
|