mirror of
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80 lines
1.9 KiB
Go
80 lines
1.9 KiB
Go
package shadowstream
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import (
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"crypto/rand"
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"errors"
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"io"
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"net"
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"github.com/Dreamacro/clash/common/pool"
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)
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// ErrShortPacket means the packet is too short to be a valid encrypted packet.
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var ErrShortPacket = errors.New("short packet")
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// Pack encrypts plaintext using stream cipher s and a random IV.
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// Returns a slice of dst containing random IV and ciphertext.
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// Ensure len(dst) >= s.IVSize() + len(plaintext).
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func Pack(dst, plaintext []byte, s Cipher) ([]byte, error) {
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if len(dst) < s.IVSize()+len(plaintext) {
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return nil, io.ErrShortBuffer
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}
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iv := dst[:s.IVSize()]
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_, err := rand.Read(iv)
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if err != nil {
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return nil, err
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}
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s.Encrypter(iv).XORKeyStream(dst[len(iv):], plaintext)
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return dst[:len(iv)+len(plaintext)], nil
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}
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// Unpack decrypts pkt using stream cipher s.
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// Returns a slice of dst containing decrypted plaintext.
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func Unpack(dst, pkt []byte, s Cipher) ([]byte, error) {
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if len(pkt) < s.IVSize() {
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return nil, ErrShortPacket
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}
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if len(dst) < len(pkt)-s.IVSize() {
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return nil, io.ErrShortBuffer
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}
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iv := pkt[:s.IVSize()]
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s.Decrypter(iv).XORKeyStream(dst, pkt[len(iv):])
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return dst[:len(pkt)-len(iv)], nil
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}
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type PacketConn struct {
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net.PacketConn
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Cipher
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}
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// NewPacketConn wraps a net.PacketConn with stream cipher encryption/decryption.
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func NewPacketConn(c net.PacketConn, ciph Cipher) *PacketConn {
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return &PacketConn{PacketConn: c, Cipher: ciph}
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}
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const maxPacketSize = 64 * 1024
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func (c *PacketConn) WriteTo(b []byte, addr net.Addr) (int, error) {
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buf := pool.Get(maxPacketSize)
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defer pool.Put(buf)
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buf, err := Pack(buf, b, c.Cipher)
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if err != nil {
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return 0, err
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}
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_, err = c.PacketConn.WriteTo(buf, addr)
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return len(b), err
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}
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func (c *PacketConn) ReadFrom(b []byte) (int, net.Addr, error) {
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n, addr, err := c.PacketConn.ReadFrom(b)
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if err != nil {
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return n, addr, err
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}
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bb, err := Unpack(b[c.IVSize():], b[:n], c.Cipher)
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if err != nil {
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return n, addr, err
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}
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copy(b, bb)
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return len(bb), addr, err
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}
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