Move Linux client & common packages into a public repo.

derp/derp_client.go

@@ -0,0 +1,182 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package derp
+
+import (
+	"bufio"
+	"crypto/rand"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net"
+	"time"
+
+	"golang.org/x/crypto/curve25519"
+	"golang.org/x/crypto/nacl/box"
+)
+
+type Client struct {
+	serverKey  [32]byte
+	privateKey [32]byte // TODO(crawshaw): make this wgcfg.PrivateKey?
+	publicKey  [32]byte
+	logf       func(format string, args ...interface{})
+	netConn    net.Conn
+	conn       *bufio.ReadWriter
+}
+
+func NewClient(privateKey [32]byte, netConn net.Conn, conn *bufio.ReadWriter, logf func(format string, args ...interface{})) (*Client, error) {
+	c := &Client{
+		privateKey: privateKey,
+		logf:       logf,
+		netConn:    netConn,
+		conn:       conn,
+	}
+	curve25519.ScalarBaseMult(&c.publicKey, &c.privateKey)
+
+	if err := c.recvServerKey(); err != nil {
+		return nil, fmt.Errorf("derp.Client: failed to receive server key: %v", err)
+	}
+	if err := c.sendClientKey(); err != nil {
+		return nil, fmt.Errorf("derp.Client: failed to send client key: %v", err)
+	}
+	_, err := c.recvServerInfo()
+	if err != nil {
+		return nil, fmt.Errorf("derp.Client: failed to receive server info: %v", err)
+	}
+
+	return c, nil
+}
+
+func (c *Client) recvServerKey() error {
+	gotMagic, err := readUint32(c.conn, 0xffffffff)
+	if err != nil {
+		return err
+	}
+	if gotMagic != magic {
+		return fmt.Errorf("bad magic %x, want %x", gotMagic, magic)
+	}
+	if err := readType(c.conn.Reader, typeServerKey); err != nil {
+		return err
+	}
+	if _, err := io.ReadFull(c.conn, c.serverKey[:]); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (c *Client) recvServerInfo() (*serverInfo, error) {
+	if err := readType(c.conn.Reader, typeServerInfo); err != nil {
+		return nil, err
+	}
+	var nonce [24]byte
+	if _, err := io.ReadFull(c.conn, nonce[:]); err != nil {
+		return nil, fmt.Errorf("nonce: %v", err)
+	}
+	msgLen, err := readUint32(c.conn, oneMB)
+	if err != nil {
+		return nil, fmt.Errorf("msglen: %v", err)
+	}
+	msgbox := make([]byte, msgLen)
+	if _, err := io.ReadFull(c.conn, msgbox); err != nil {
+		return nil, fmt.Errorf("msgbox: %v", err)
+	}
+	msg, ok := box.Open(nil, msgbox, &nonce, &c.serverKey, &c.privateKey)
+	if !ok {
+		return nil, fmt.Errorf("msgbox: cannot open len=%d with server key %x", msgLen, c.serverKey[:])
+	}
+	info := new(serverInfo)
+	if err := json.Unmarshal(msg, info); err != nil {
+		return nil, fmt.Errorf("msg: %v", err)
+	}
+	return info, nil
+}
+
+func (c *Client) sendClientKey() error {
+	var nonce [24]byte
+	if _, err := rand.Read(nonce[:]); err != nil {
+		return err
+	}
+	msg := []byte("{}") // no clientInfo for now
+	msgbox := box.Seal(nil, msg, &nonce, &c.serverKey, &c.privateKey)
+
+	if _, err := c.conn.Write(c.publicKey[:]); err != nil {
+		return err
+	}
+	if _, err := c.conn.Write(nonce[:]); err != nil {
+		return err
+	}
+	if err := putUint32(c.conn.Writer, uint32(len(msgbox))); err != nil {
+		return err
+	}
+	if _, err := c.conn.Write(msgbox); err != nil {
+		return err
+	}
+	return c.conn.Flush()
+}
+
+func (c *Client) Send(dstKey [32]byte, msg []byte) (err error) {
+	defer func() {
+		if err != nil {
+			err = fmt.Errorf("derp.Send: %v", err)
+		}
+	}()
+
+	if err := c.conn.WriteByte(typeSendPacket); err != nil {
+		return err
+	}
+	if _, err := c.conn.Write(dstKey[:]); err != nil {
+		return err
+	}
+	msgLen := uint32(len(msg))
+	if int(msgLen) != len(msg) {
+		return fmt.Errorf("packet too big: %d", len(msg))
+	}
+	if err := putUint32(c.conn.Writer, msgLen); err != nil {
+		return err
+	}
+	if _, err := c.conn.Write(msg); err != nil {
+		return err
+	}
+	return c.conn.Flush()
+}
+
+func (c *Client) Recv(b []byte) (n int, err error) {
+	defer func() {
+		if err != nil {
+			err = fmt.Errorf("derp.Recv: %v", err)
+		}
+	}()
+
+loop:
+	for {
+		c.netConn.SetReadDeadline(time.Now().Add(120 * time.Second))
+		packetType, err := c.conn.ReadByte()
+		if err != nil {
+			return 0, err
+		}
+		switch packetType {
+		case typeKeepAlive:
+			continue
+		case typeRecvPacket:
+			break loop
+		default:
+			return 0, fmt.Errorf("derp.Recv: unknown packet type %d", packetType)
+		}
+	}
+
+	packetLen, err := readUint32(c.conn.Reader, oneMB)
+	if err != nil {
+		return 0, err
+	}
+	if int(packetLen) > len(b) {
+		// TODO(crawshaw): discard the packet
+		return 0, io.ErrShortBuffer
+	}
+	b = b[:packetLen]
+	if _, err := io.ReadFull(c.conn, b); err != nil {
+		return 0, err
+	}
+	return int(packetLen), nil
+}