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secret.go
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secret.go
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// Package secret provides simple utilities for encrypting and decrypting data.
package secret
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"crypto/sha256"
"errors"
)
// ErrDecryptFailed is returned when Decrypt is unable to decrypt due to
// invalid inputs.
var ErrDecryptFailed = errors.New("decrypt failed")
// Encrypt data. Uses AES-256-CFB encrypter.
func Encrypt(key string, data []byte) ([]byte, error) {
keyb := sha256.Sum256([]byte(key))
ciph, err := aes.NewCipher(keyb[:])
if err != nil {
return nil, err
}
// The iv is added to the front of the final payload.
encdata := make([]byte, aes.BlockSize*2+len(data))
if _, err := rand.Read(encdata[:aes.BlockSize]); err != nil {
return nil, err
}
// The iv is also added to the front of the encrypted data so we can
// verify after decrypting.
dataiv := make([]byte, aes.BlockSize+len(data))
copy(dataiv, encdata[:aes.BlockSize])
copy(dataiv[aes.BlockSize:], data)
cipher.NewCFBEncrypter(ciph, encdata[:aes.BlockSize]).
XORKeyStream(encdata[aes.BlockSize:], dataiv)
return encdata, nil
}
// Decrypt data. Uses AES-256-CFB decrypter.
func Decrypt(key string, data []byte) ([]byte, error) {
if len(data) < aes.BlockSize {
return nil, ErrDecryptFailed
}
keyb := sha256.Sum256([]byte(key))
ciph, err := aes.NewCipher(keyb[:])
if err != nil {
return nil, err
}
decdata := make([]byte, len(data)-aes.BlockSize)
cipher.NewCFBDecrypter(ciph, data[:aes.BlockSize]).
XORKeyStream(decdata, data[aes.BlockSize:])
if len(decdata) < aes.BlockSize {
return nil, ErrDecryptFailed
}
if !bytes.Equal(data[:aes.BlockSize], decdata[:aes.BlockSize]) {
return nil, ErrDecryptFailed
}
return decdata[aes.BlockSize:], nil
}