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package security
import (
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"encoding/base64"
"errors"
"fmt"
"io"
)
type CredentialCipher struct {
aead cipher.AEAD
}
func NewCredentialCipher(encodedKey string) (*CredentialCipher, error) {
key, err := base64.StdEncoding.DecodeString(encodedKey)
if err != nil {
return nil, fmt.Errorf("decode credential key: %w", err)
}
if len(key) != 32 {
return nil, errors.New("credential key must be a base64-encoded 32-byte key")
}
block, err := aes.NewCipher(key)
if err != nil {
return nil, fmt.Errorf("create credential cipher: %w", err)
}
aead, err := cipher.NewGCM(block)
if err != nil {
return nil, fmt.Errorf("create credential AEAD: %w", err)
}
return &CredentialCipher{aead: aead}, nil
}
func (c *CredentialCipher) Encrypt(plaintext string) ([]byte, error) {
if plaintext == "" {
return nil, errors.New("credential cannot be empty")
}
nonce := make([]byte, c.aead.NonceSize())
if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
return nil, fmt.Errorf("generate credential nonce: %w", err)
}
return c.aead.Seal(nonce, nonce, []byte(plaintext), nil), nil
}
func (c *CredentialCipher) Decrypt(ciphertext []byte) (string, error) {
if len(ciphertext) < c.aead.NonceSize() {
return "", errors.New("credential ciphertext is truncated")
}
nonce := ciphertext[:c.aead.NonceSize()]
plaintext, err := c.aead.Open(nil, nonce, ciphertext[c.aead.NonceSize():], nil)
if err != nil {
return "", errors.New("decrypt credential: authentication failed")
}
return string(plaintext), nil
}
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