Xray-core/transport/internet/kcp/crypt.go

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// +build !confonly
package kcp
import (
"crypto/cipher"
"encoding/binary"
"hash/fnv"
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"github.com/xtls/xray-core/common"
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)
// SimpleAuthenticator is a legacy AEAD used for KCP encryption.
type SimpleAuthenticator struct{}
// NewSimpleAuthenticator creates a new SimpleAuthenticator
func NewSimpleAuthenticator() cipher.AEAD {
return &SimpleAuthenticator{}
}
// NonceSize implements cipher.AEAD.NonceSize().
func (*SimpleAuthenticator) NonceSize() int {
return 0
}
// Overhead implements cipher.AEAD.NonceSize().
func (*SimpleAuthenticator) Overhead() int {
return 6
}
// Seal implements cipher.AEAD.Seal().
func (a *SimpleAuthenticator) Seal(dst, nonce, plain, extra []byte) []byte {
dst = append(dst, 0, 0, 0, 0, 0, 0) // 4 bytes for hash, and then 2 bytes for length
binary.BigEndian.PutUint16(dst[4:], uint16(len(plain)))
dst = append(dst, plain...)
fnvHash := fnv.New32a()
common.Must2(fnvHash.Write(dst[4:]))
fnvHash.Sum(dst[:0])
dstLen := len(dst)
xtra := 4 - dstLen%4
if xtra != 4 {
dst = append(dst, make([]byte, xtra)...)
}
xorfwd(dst)
if xtra != 4 {
dst = dst[:dstLen]
}
return dst
}
// Open implements cipher.AEAD.Open().
func (a *SimpleAuthenticator) Open(dst, nonce, cipherText, extra []byte) ([]byte, error) {
dst = append(dst, cipherText...)
dstLen := len(dst)
xtra := 4 - dstLen%4
if xtra != 4 {
dst = append(dst, make([]byte, xtra)...)
}
xorbkd(dst)
if xtra != 4 {
dst = dst[:dstLen]
}
fnvHash := fnv.New32a()
common.Must2(fnvHash.Write(dst[4:]))
if binary.BigEndian.Uint32(dst[:4]) != fnvHash.Sum32() {
return nil, newError("invalid auth")
}
length := binary.BigEndian.Uint16(dst[4:6])
if len(dst)-6 != int(length) {
return nil, newError("invalid auth")
}
return dst[6:], nil
}