/
cipher.go
80 lines (67 loc) · 1.54 KB
/
cipher.go
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// copy from qtunnel project
package ecrypt
import (
"crypto/aes"
"crypto/cipher"
"crypto/md5"
"crypto/rc4"
"fmt"
)
type Cipher struct {
enc cipher.Stream
dec cipher.Stream
}
type chiperCreator func(key []byte) (*Cipher, error)
var cipherMap = map[string]chiperCreator{
"rc4": newRC4Cipher,
"aes256cfb": newAES256CFBCipher,
}
func secretToKey(secret []byte, size int) []byte {
// size mod 16 must be 0
h := md5.New()
buf := make([]byte, size)
count := size / md5.Size
// repeatly fill the key with the secret
for i := 0; i < count; i++ {
h.Write(secret)
copy(buf[md5.Size*i:md5.Size*(i+1)-1], h.Sum(nil))
}
return buf
}
func newRC4Cipher(secret []byte) (*Cipher, error) {
ec, err := rc4.NewCipher(secretToKey(secret, 16))
if err != nil {
return nil, err
}
dc := *ec
return &Cipher{ec, &dc}, nil
}
func newAES256CFBCipher(secret []byte) (*Cipher, error) {
key := secretToKey(secret, 32)
block, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
ec := cipher.NewCFBEncrypter(block, key[:block.BlockSize()])
dc := cipher.NewCFBDecrypter(block, key[:block.BlockSize()])
return &Cipher{ec, dc}, nil
}
func NewCipher(cryptoMethod string, secret []byte) *Cipher {
cc := cipherMap[cryptoMethod]
if cc == nil {
fmt.Printf("unsupported crypto method %s", cryptoMethod)
return nil
}
c, err := cc(secret)
if err != nil {
fmt.Print(err)
return nil
}
return c
}
func (c *Cipher) Encrypt(dst, src []byte) {
c.enc.XORKeyStream(dst, src)
}
func (c *Cipher) Decrypt(dst, src []byte) {
c.dec.XORKeyStream(dst, src)
}