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storage.go
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storage.go
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package session
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"crypto/rand"
"encoding/base64"
"encoding/gob"
"errors"
"net/http"
)
func init() {
gob.Register(M{})
}
type Storage interface {
Clean(*Session) error
Flush(*Session) error
LoadTo(*http.Request, *Session) error
}
const (
keySize = 16
aesKeySize = 32
)
var (
defaultKey = genKey(keySize)[:keySize]
)
func SetKey(key []byte) {
defaultKey = key[:keySize]
}
func GetKey() []byte {
return defaultKey
}
var errKeyTooShort = errors.New("The key is too short")
var errValueTooShort = errors.New("The value is too short")
func encrypt(key, value []byte) ([]byte, error) {
if len(key) < aesKeySize-keySize {
return nil, errKeyTooShort
}
key = append(key[:aesKeySize-keySize], defaultKey...)
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
iv := make([]byte, block.BlockSize())
rand.Read(iv)
stream := cipher.NewCTR(block, iv)
stream.XORKeyStream(value, value)
return append(iv, value...), nil
}
func decrypt(key, value []byte) ([]byte, error) {
if len(key) < aesKeySize-keySize {
return nil, errKeyTooShort
}
key = append(key[:aesKeySize-keySize], defaultKey...)
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
if len(value) > block.BlockSize() {
iv := value[:block.BlockSize()]
value = value[block.BlockSize():]
stream := cipher.NewCTR(block, iv)
stream.XORKeyStream(value, value)
return value, nil
}
return nil, errValueTooShort
}
func decoding(key []byte, src string, dst *M) error {
// 1. base64 decoding
buf, err := base64.StdEncoding.DecodeString(src)
if err != nil {
return err
}
// 2. cypto decoding
buf, err = decrypt(key, buf)
if err != nil {
return err
}
// 3. gob decoding
g := gob.NewDecoder(bytes.NewBuffer(buf))
if err = g.Decode(&dst); err != nil {
return err
}
return nil
}
func encoding(key []byte, src map[string]interface{}) (string, error) {
// 1. gob encoding
var buf bytes.Buffer
g := gob.NewEncoder(&buf)
if err := g.Encode(src); err != nil {
return "", err
}
// 2. cypto encoding
ciphertext, err := encrypt(key, buf.Bytes())
if err != nil {
return "", err
}
// 3. base64 encoding
return base64.StdEncoding.EncodeToString(ciphertext), nil
}