Esempio n. 1
0
func (conn *obfs4Conn) clientHandshake(nodeID *ntor.NodeID, peerIdentityKey *ntor.PublicKey, sessionKey *ntor.Keypair) error {
	if conn.isServer {
		return fmt.Errorf("clientHandshake called on server connection")
	}

	// Generate and send the client handshake.
	hs := newClientHandshake(nodeID, peerIdentityKey, sessionKey)
	blob, err := hs.generateHandshake()
	if err != nil {
		return err
	}
	if _, err = conn.Conn.Write(blob); err != nil {
		return err
	}

	// Consume the server handshake.
	var hsBuf [maxHandshakeLength]byte
	for {
		n, err := conn.Conn.Read(hsBuf[:])
		if err != nil {
			// The Read() could have returned data and an error, but there is
			// no point in continuing on an EOF or whatever.
			return err
		}
		conn.receiveBuffer.Write(hsBuf[:n])

		n, seed, err := hs.parseServerHandshake(conn.receiveBuffer.Bytes())
		if err == ErrMarkNotFoundYet {
			continue
		} else if err != nil {
			return err
		}
		_ = conn.receiveBuffer.Next(n)

		// Use the derived key material to intialize the link crypto.
		okm := ntor.Kdf(seed, framing.KeyLength*2)
		conn.encoder = framing.NewEncoder(okm[:framing.KeyLength])
		conn.decoder = framing.NewDecoder(okm[framing.KeyLength:])

		return nil
	}
}
Esempio n. 2
0
func (conn *obfs4Conn) serverHandshake(sf *obfs4ServerFactory, sessionKey *ntor.Keypair) error {
	if !conn.isServer {
		return fmt.Errorf("serverHandshake called on client connection")
	}

	// Generate the server handshake, and arm the base timeout.
	hs := newServerHandshake(sf.nodeID, sf.identityKey, sessionKey)
	if err := conn.Conn.SetDeadline(time.Now().Add(serverHandshakeTimeout)); err != nil {
		return err
	}

	// Consume the client handshake.
	var hsBuf [maxHandshakeLength]byte
	for {
		n, err := conn.Conn.Read(hsBuf[:])
		if err != nil {
			// The Read() could have returned data and an error, but there is
			// no point in continuing on an EOF or whatever.
			return err
		}
		conn.receiveBuffer.Write(hsBuf[:n])

		seed, err := hs.parseClientHandshake(sf.replayFilter, conn.receiveBuffer.Bytes())
		if err == ErrMarkNotFoundYet {
			continue
		} else if err != nil {
			return err
		}
		conn.receiveBuffer.Reset()

		if err := conn.Conn.SetDeadline(time.Time{}); err != nil {
			return nil
		}

		// Use the derived key material to intialize the link crypto.
		okm := ntor.Kdf(seed, framing.KeyLength*2)
		conn.encoder = framing.NewEncoder(okm[framing.KeyLength:])
		conn.decoder = framing.NewDecoder(okm[:framing.KeyLength])

		break
	}

	// Since the current and only implementation always sends a PRNG seed for
	// the length obfuscation, this makes the amount of data received from the
	// server inconsistent with the length sent from the client.
	//
	// Rebalance this by tweaking the client mimimum padding/server maximum
	// padding, and sending the PRNG seed unpadded (As in, treat the PRNG seed
	// as part of the server response).  See inlineSeedFrameLength in
	// handshake_ntor.go.

	// Generate/send the response.
	blob, err := hs.generateHandshake()
	if err != nil {
		return err
	}
	var frameBuf bytes.Buffer
	if _, err = frameBuf.Write(blob); err != nil {
		return err
	}

	// Send the PRNG seed as the first packet.
	if err := conn.makePacket(&frameBuf, packetTypePrngSeed, sf.lenSeed.Bytes()[:], 0); err != nil {
		return err
	}
	if _, err = conn.Conn.Write(frameBuf.Bytes()); err != nil {
		return err
	}

	return nil
}