mirror of
https://github.com/tailscale/tailscale.git
synced 2024-12-12 11:14:40 +00:00
79d8288f0a
No server support yet, but we want Tailscale 1.6 clients to be able to respond to them when the server can do it. Updates #1310 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
218 lines
6.9 KiB
Go
218 lines
6.9 KiB
Go
// 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 implements DERP, the Detour Encrypted Routing Protocol.
|
|
//
|
|
// DERP routes packets to clients using curve25519 keys as addresses.
|
|
//
|
|
// DERP is used by Tailscale nodes to proxy encrypted WireGuard
|
|
// packets through the Tailscale cloud servers when a direct path
|
|
// cannot be found or opened. DERP is a last resort. Both sides
|
|
// between very aggressive NATs, firewalls, no IPv6, etc? Well, DERP.
|
|
package derp
|
|
|
|
import (
|
|
"bufio"
|
|
"encoding/binary"
|
|
"errors"
|
|
"fmt"
|
|
"io"
|
|
"io/ioutil"
|
|
"time"
|
|
)
|
|
|
|
// MaxPacketSize is the maximum size of a packet sent over DERP.
|
|
// (This only includes the data bytes visible to magicsock, not
|
|
// including its on-wire framing overhead)
|
|
const MaxPacketSize = 64 << 10
|
|
|
|
// magic is the DERP magic number, sent in the frameServerKey frame
|
|
// upon initial connection.
|
|
const magic = "DERP🔑" // 8 bytes: 0x44 45 52 50 f0 9f 94 91
|
|
|
|
const (
|
|
nonceLen = 24
|
|
frameHeaderLen = 1 + 4 // frameType byte + 4 byte length
|
|
keyLen = 32
|
|
maxInfoLen = 1 << 20
|
|
keepAlive = 60 * time.Second
|
|
)
|
|
|
|
// ProtocolVersion is bumped whenever there's a wire-incompatible change.
|
|
// * version 1 (zero on wire): consistent box headers, in use by employee dev nodes a bit
|
|
// * version 2: received packets have src addrs in frameRecvPacket at beginning
|
|
const ProtocolVersion = 2
|
|
|
|
// frameType is the one byte frame type at the beginning of the frame
|
|
// header. The second field is a big-endian uint32 describing the
|
|
// length of the remaining frame (not including the initial 5 bytes).
|
|
type frameType byte
|
|
|
|
/*
|
|
Protocol flow:
|
|
|
|
Login:
|
|
* client connects
|
|
* server sends frameServerKey
|
|
* client sends frameClientInfo
|
|
* server sends frameServerInfo
|
|
|
|
Steady state:
|
|
* server occasionally sends frameKeepAlive (or framePing)
|
|
* client responds to any framePing with a framePong
|
|
* client sends frameSendPacket
|
|
* server then sends frameRecvPacket to recipient
|
|
*/
|
|
const (
|
|
frameServerKey = frameType(0x01) // 8B magic + 32B public key + (0+ bytes future use)
|
|
frameClientInfo = frameType(0x02) // 32B pub key + 24B nonce + naclbox(json)
|
|
frameServerInfo = frameType(0x03) // 24B nonce + naclbox(json)
|
|
frameSendPacket = frameType(0x04) // 32B dest pub key + packet bytes
|
|
frameForwardPacket = frameType(0x0a) // 32B src pub key + 32B dst pub key + packet bytes
|
|
frameRecvPacket = frameType(0x05) // v0/1: packet bytes, v2: 32B src pub key + packet bytes
|
|
frameKeepAlive = frameType(0x06) // no payload, no-op (to be replaced with ping/pong)
|
|
frameNotePreferred = frameType(0x07) // 1 byte payload: 0x01 or 0x00 for whether this is client's home node
|
|
|
|
// framePeerGone is sent from server to client to signal that
|
|
// a previous sender is no longer connected. That is, if A
|
|
// sent to B, and then if A disconnects, the server sends
|
|
// framePeerGone to B so B can forget that a reverse path
|
|
// exists on that connection to get back to A.
|
|
framePeerGone = frameType(0x08) // 32B pub key of peer that's gone
|
|
|
|
// framePeerPresent is like framePeerGone, but for other
|
|
// members of the DERP region when they're meshed up together.
|
|
framePeerPresent = frameType(0x09) // 32B pub key of peer that's connected
|
|
|
|
// frameWatchConns is how one DERP node in a regional mesh
|
|
// subscribes to the others in the region.
|
|
// There's no payload. If the sender doesn't have permission, the connection
|
|
// is closed. Otherwise, the client is initially flooded with
|
|
// framePeerPresent for all connected nodes, and then a stream of
|
|
// framePeerPresent & framePeerGone has peers connect and disconnect.
|
|
frameWatchConns = frameType(0x10)
|
|
|
|
// frameClosePeer is a privileged frame type (requires the
|
|
// mesh key for now) that closes the provided peer's
|
|
// connection. (To be used for cluster load balancing
|
|
// purposes, when clients end up on a non-ideal node)
|
|
frameClosePeer = frameType(0x11) // 32B pub key of peer to close.
|
|
|
|
framePing = frameType(0x12) // 8 byte ping payload, to be echoed back in framePong
|
|
framePong = frameType(0x13) // 8 byte payload, the contents of the ping being replied to
|
|
)
|
|
|
|
var bin = binary.BigEndian
|
|
|
|
func writeUint32(bw *bufio.Writer, v uint32) error {
|
|
var b [4]byte
|
|
bin.PutUint32(b[:], v)
|
|
// Writing a byte at a time is a bit silly,
|
|
// but it causes b not to escape,
|
|
// which more than pays for the silliness.
|
|
for _, c := range &b {
|
|
err := bw.WriteByte(c)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
func readUint32(br *bufio.Reader) (uint32, error) {
|
|
var b [4]byte
|
|
// Reading a byte at a time is a bit silly,
|
|
// but it causes b not to escape,
|
|
// which more than pays for the silliness.
|
|
for i := range &b {
|
|
c, err := br.ReadByte()
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
b[i] = c
|
|
}
|
|
return bin.Uint32(b[:]), nil
|
|
}
|
|
|
|
func readFrameTypeHeader(br *bufio.Reader, wantType frameType) (frameLen uint32, err error) {
|
|
gotType, frameLen, err := readFrameHeader(br)
|
|
if err == nil && wantType != gotType {
|
|
err = fmt.Errorf("bad frame type 0x%X, want 0x%X", gotType, wantType)
|
|
}
|
|
return frameLen, err
|
|
}
|
|
|
|
func readFrameHeader(br *bufio.Reader) (t frameType, frameLen uint32, err error) {
|
|
tb, err := br.ReadByte()
|
|
if err != nil {
|
|
return 0, 0, err
|
|
}
|
|
frameLen, err = readUint32(br)
|
|
if err != nil {
|
|
return 0, 0, err
|
|
}
|
|
return frameType(tb), frameLen, nil
|
|
}
|
|
|
|
// readFrame reads a frame header and then reads its payload into
|
|
// b[:frameLen].
|
|
//
|
|
// If the frame header length is greater than maxSize, readFrame returns
|
|
// an error after reading the frame header.
|
|
//
|
|
// If the frame is less than maxSize but greater than len(b), len(b)
|
|
// bytes are read, err will be io.ErrShortBuffer, and frameLen and t
|
|
// will both be set. That is, callers need to explicitly handle when
|
|
// they get more data than expected.
|
|
func readFrame(br *bufio.Reader, maxSize uint32, b []byte) (t frameType, frameLen uint32, err error) {
|
|
t, frameLen, err = readFrameHeader(br)
|
|
if err != nil {
|
|
return 0, 0, err
|
|
}
|
|
if frameLen > maxSize {
|
|
return 0, 0, fmt.Errorf("frame header size %d exceeds reader limit of %d", frameLen, maxSize)
|
|
}
|
|
|
|
n, err := io.ReadFull(br, b[:minUint32(frameLen, uint32(len(b)))])
|
|
if err != nil {
|
|
return 0, 0, err
|
|
}
|
|
remain := frameLen - uint32(n)
|
|
if remain > 0 {
|
|
if _, err := io.CopyN(ioutil.Discard, br, int64(remain)); err != nil {
|
|
return 0, 0, err
|
|
}
|
|
err = io.ErrShortBuffer
|
|
}
|
|
return t, frameLen, err
|
|
}
|
|
|
|
func writeFrameHeader(bw *bufio.Writer, t frameType, frameLen uint32) error {
|
|
if err := bw.WriteByte(byte(t)); err != nil {
|
|
return err
|
|
}
|
|
return writeUint32(bw, frameLen)
|
|
}
|
|
|
|
// writeFrame writes a complete frame & flushes it.
|
|
func writeFrame(bw *bufio.Writer, t frameType, b []byte) error {
|
|
if len(b) > 10<<20 {
|
|
return errors.New("unreasonably large frame write")
|
|
}
|
|
if err := writeFrameHeader(bw, t, uint32(len(b))); err != nil {
|
|
return err
|
|
}
|
|
if _, err := bw.Write(b); err != nil {
|
|
return err
|
|
}
|
|
return bw.Flush()
|
|
}
|
|
|
|
func minUint32(a, b uint32) uint32 {
|
|
if a < b {
|
|
return a
|
|
}
|
|
return b
|
|
}
|