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aes.go
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aes.go
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package aes
import (
"crypto/aes"
"crypto/cipher"
"encoding/base64"
"errors"
"github.com/alexfalkowski/go-service/crypto/algo"
"github.com/alexfalkowski/go-service/crypto/rand"
)
// Code is adapted from https://gist.github.com/fracasula/38aa1a4e7481f9cedfa78a0cdd5f1865.
// ErrInvalidLength for aes.
var ErrInvalidLength = errors.New("invalid length")
// Generate for aes.
func Generate() (string, error) {
s, err := rand.GenerateBytes(32)
return base64.StdEncoding.EncodeToString(s), err
}
// Algo for aes.
type Algo interface {
algo.Cipher
}
// NewAlgo for aes.
func NewAlgo(cfg *Config) (Algo, error) {
if !IsEnabled(cfg) {
return &algo.NoCipher{}, nil
}
k, err := cfg.GetKey()
return &aesAlgo{key: []byte(k)}, err
}
type aesAlgo struct {
key []byte
}
func (a *aesAlgo) Encrypt(msg string) (string, error) {
g, err := a.aead()
if err != nil {
return "", err
}
n, err := rand.GenerateBytes(uint32(g.NonceSize()))
if err != nil {
return "", err
}
s := g.Seal(n, n, []byte(msg), nil)
return base64.StdEncoding.EncodeToString(s), nil
}
func (a *aesAlgo) Decrypt(msg string) (string, error) {
d, err := base64.StdEncoding.DecodeString(msg)
if err != nil {
return "", err
}
g, err := a.aead()
if err != nil {
return "", err
}
size := g.NonceSize()
if len(d) < size {
return "", ErrInvalidLength
}
nonce, c := d[:size], d[size:]
d, err = g.Open(nil, nonce, c, nil)
return string(d), err
}
func (a *aesAlgo) aead() (cipher.AEAD, error) {
b, err := aes.NewCipher(a.key)
if err != nil {
return nil, err
}
return cipher.NewGCM(b)
}