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cipher.go
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cipher.go
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package snell
import (
"crypto/aes"
"crypto/cipher"
"github.com/Dreamacro/go-shadowsocks2/shadowaead"
"golang.org/x/crypto/argon2"
"golang.org/x/crypto/chacha20poly1305"
)
type snellCipher struct {
psk []byte
keySize int
makeAEAD func(key []byte) (cipher.AEAD, error)
}
func (sc *snellCipher) KeySize() int { return sc.keySize }
func (sc *snellCipher) SaltSize() int { return 16 }
func (sc *snellCipher) Encrypter(salt []byte) (cipher.AEAD, error) {
return sc.makeAEAD(snellKDF(sc.psk, salt, sc.KeySize()))
}
func (sc *snellCipher) Decrypter(salt []byte) (cipher.AEAD, error) {
return sc.makeAEAD(snellKDF(sc.psk, salt, sc.KeySize()))
}
func snellKDF(psk, salt []byte, keySize int) []byte {
// snell use a special kdf function
return argon2.IDKey(psk, salt, 3, 8, 1, 32)[:keySize]
}
func aesGCM(key []byte) (cipher.AEAD, error) {
blk, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
return cipher.NewGCM(blk)
}
func NewAES128GCM(psk []byte) shadowaead.Cipher {
return &snellCipher{
psk: psk,
keySize: 16,
makeAEAD: aesGCM,
}
}
func NewChacha20Poly1305(psk []byte) shadowaead.Cipher {
return &snellCipher{
psk: psk,
keySize: 32,
makeAEAD: chacha20poly1305.New,
}
}