/
enc.go
147 lines (119 loc) · 2.59 KB
/
enc.go
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package main
import (
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"errors"
"fmt"
"io"
"golang.org/x/crypto/scrypt"
)
type Enc interface {
Encrypt([]byte, []byte) ([]byte, error)
Decrypt([]byte, []byte) ([]byte, error)
}
type enc struct{}
const (
KeySize = 16
SaltSize = 32
NonceSize = 12
)
const Overhead = SaltSize + NonceSize
func NewEnc() Enc {
return &enc{}
}
func (e *enc) Encrypt(pass, message []byte) ([]byte, error) {
salt, err := e.randBytes(SaltSize)
if err != nil {
return nil, err
}
key, err := e.deriveKey(pass, salt)
if err != nil {
return nil, err
}
out, err := e.aesEncrypt(key, message)
if err != nil {
return nil, err
}
out = append(salt, out...)
return out, nil
}
func (e *enc) Decrypt(pass, message []byte) ([]byte, error) {
if len(message) < Overhead {
return nil, errors.New("Message is less than overhead")
}
key, err := e.deriveKey(pass, message[:SaltSize])
if err != nil {
return nil, err
}
out, err := e.aesDecrypt(key, message[SaltSize:])
if err != nil {
return nil, err
}
return out, nil
}
// deriveKey generates a new NaCl key from a passphrase and salt.
func (e *enc) deriveKey(pass, salt []byte) ([]byte, error) {
var aesKey = make([]byte, KeySize)
key, err := scrypt.Key(pass, salt, 1048576, 8, 1, KeySize)
if err != nil {
return nil, err
}
copy(aesKey[:], key)
return aesKey, nil
}
// GenerateNonce creates a new random nonce.
func (e *enc) generateNonce() ([]byte, error) {
nonce := make([]byte, NonceSize)
_, err := io.ReadFull(rand.Reader, nonce[:])
if err != nil {
return nil, err
}
return nonce, nil
}
// Encrypt secures a message using AES-GCM.
func (e *enc) aesEncrypt(key, message []byte) ([]byte, error) {
c, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
gcm, err := cipher.NewGCM(c)
if err != nil {
return nil, err
}
nonce, err := e.generateNonce()
if err != nil {
return nil, err
}
out := gcm.Seal(nonce, nonce, message, nil)
return out, nil
}
func (e *enc) aesDecrypt(key, message []byte) ([]byte, error) {
if len(message) <= NonceSize {
return nil, errors.New("Message is too short")
}
c, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
gcm, err := cipher.NewGCM(c)
if err != nil {
return nil, err
}
nonce := make([]byte, NonceSize)
copy(nonce, message)
out, err := gcm.Open(nil, nonce, message[NonceSize:], nil)
if err != nil {
fmt.Println("this err")
return nil, err
}
return out, nil
}
func (e *enc) randBytes(n int) ([]byte, error) {
r := make([]byte, n)
_, err := io.ReadFull(rand.Reader, r)
if err != nil {
return nil, err
}
return r, nil
}