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110 lines
2.6 KiB
Go
110 lines
2.6 KiB
Go
package core
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import (
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"crypto/md5"
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"errors"
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"net"
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"sort"
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"strings"
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"github.com/shadowsocks/go-shadowsocks2/shadowaead"
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)
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type Cipher interface {
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StreamConnCipher
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PacketConnCipher
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}
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type StreamConnCipher interface {
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StreamConn(net.Conn) net.Conn
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}
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type PacketConnCipher interface {
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PacketConn(net.PacketConn) net.PacketConn
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}
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// ErrCipherNotSupported occurs when a cipher is not supported (likely because of security concerns).
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var ErrCipherNotSupported = errors.New("cipher not supported")
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const (
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aeadAes128Gcm = "AEAD_AES_128_GCM"
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aeadAes256Gcm = "AEAD_AES_256_GCM"
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aeadChacha20Poly1305 = "AEAD_CHACHA20_POLY1305"
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)
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// List of AEAD ciphers: key size in bytes and constructor
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var aeadList = map[string]struct {
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KeySize int
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New func([]byte) (shadowaead.Cipher, error)
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}{
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aeadAes128Gcm: {16, shadowaead.AESGCM},
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aeadAes256Gcm: {32, shadowaead.AESGCM},
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aeadChacha20Poly1305: {32, shadowaead.Chacha20Poly1305},
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}
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// ListCipher returns a list of available cipher names sorted alphabetically.
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func ListCipher() []string {
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var l []string
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for k := range aeadList {
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l = append(l, k)
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}
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sort.Strings(l)
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return l
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}
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// PickCipher returns a Cipher of the given name. Derive key from password if given key is empty.
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func PickCipher(name string, key []byte, password string) (Cipher, error) {
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name = strings.ToUpper(name)
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switch name {
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case "DUMMY":
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return &dummy{}, nil
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case "CHACHA20-IETF-POLY1305":
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name = aeadChacha20Poly1305
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case "AES-128-GCM":
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name = aeadAes128Gcm
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case "AES-256-GCM":
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name = aeadAes256Gcm
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}
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if choice, ok := aeadList[name]; ok {
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if len(key) == 0 {
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key = kdf(password, choice.KeySize)
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}
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if len(key) != choice.KeySize {
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return nil, shadowaead.KeySizeError(choice.KeySize)
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}
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aead, err := choice.New(key)
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return &aeadCipher{aead}, err
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}
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return nil, ErrCipherNotSupported
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}
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type aeadCipher struct{ shadowaead.Cipher }
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func (aead *aeadCipher) StreamConn(c net.Conn) net.Conn { return shadowaead.NewConn(c, aead) }
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func (aead *aeadCipher) PacketConn(c net.PacketConn) net.PacketConn {
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return shadowaead.NewPacketConn(c, aead)
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}
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// dummy cipher does not encrypt
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type dummy struct{}
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func (dummy) StreamConn(c net.Conn) net.Conn { return c }
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func (dummy) PacketConn(c net.PacketConn) net.PacketConn { return c }
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// key-derivation function from original Shadowsocks
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func kdf(password string, keyLen int) []byte {
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var b, prev []byte
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h := md5.New()
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for len(b) < keyLen {
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h.Write(prev)
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h.Write([]byte(password))
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b = h.Sum(b)
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prev = b[len(b)-h.Size():]
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h.Reset()
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}
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return b[:keyLen]
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}
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