135 lines
3.4 KiB
Go
135 lines
3.4 KiB
Go
package dnsttclient
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import (
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"bufio"
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"context"
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"encoding/binary"
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"io"
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"log"
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"net"
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"sync"
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"time"
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"socksrevivepc/internal/dnsttcore/turbotunnel"
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)
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const dialTimeout = 30 * time.Second
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// TLSPacketConn is a TLS- and TCP-based transport for DNS messages, used for
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// DNS over TLS (DoT). Its WriteTo and ReadFrom methods exchange DNS messages
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// over a TLS channel, prefixing each message with a two-octet length field as
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// in DNS over TCP.
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//
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// TLSPacketConn deals only with already formatted DNS messages. It does not
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// handle encoding information into the messages. That is rather the
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// responsibility of DNSPacketConn.
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//
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// https://tools.ietf.org/html/rfc7858
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type TLSPacketConn struct {
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// QueuePacketConn is the direct receiver of ReadFrom and WriteTo calls.
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// recvLoop and sendLoop take the messages out of the receive and send
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// queues and actually put them on the network.
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*turbotunnel.QueuePacketConn
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}
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// NewTLSPacketConn creates a new TLSPacketConn configured to use the TLS
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// server at addr as a DNS over TLS resolver. It maintains a TLS connection to
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// the resolver, reconnecting as necessary. It closes the connection if any
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// reconnection attempt fails.
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func NewTLSPacketConn(addr string, dialTLSContext func(ctx context.Context, network, addr string) (net.Conn, error)) (*TLSPacketConn, error) {
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dial := func() (net.Conn, error) {
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ctx, cancel := context.WithTimeout(context.Background(), dialTimeout)
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defer cancel()
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return dialTLSContext(ctx, "tcp", addr)
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}
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// We maintain one TLS connection at a time, redialing it whenever it
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// becomes disconnected. We do the first dial here, outside the
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// goroutine, so that any immediate and permanent connection errors are
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// reported directly to the caller of NewTLSPacketConn.
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conn, err := dial()
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if err != nil {
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return nil, err
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}
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c := &TLSPacketConn{
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QueuePacketConn: turbotunnel.NewQueuePacketConn(turbotunnel.DummyAddr{}, 0),
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}
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go func() {
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defer c.Close()
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for {
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var wg sync.WaitGroup
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wg.Add(2)
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go func() {
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err := c.recvLoop(conn)
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if err != nil {
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log.Printf("recvLoop: %v", err)
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}
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wg.Done()
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}()
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go func() {
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err := c.sendLoop(conn)
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if err != nil {
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log.Printf("sendLoop: %v", err)
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}
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wg.Done()
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}()
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wg.Wait()
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conn.Close()
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// Whenever the TLS connection dies, redial a new one.
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conn, err = dial()
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if err != nil {
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log.Printf("dial tls: %v", err)
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break
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}
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}
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}()
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return c, nil
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}
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// recvLoop reads length-prefixed messages from conn and passes them to the
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// incoming queue.
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func (c *TLSPacketConn) recvLoop(conn net.Conn) error {
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br := bufio.NewReader(conn)
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for {
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var length uint16
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err := binary.Read(br, binary.BigEndian, &length)
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if err != nil {
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if err == io.EOF {
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err = nil
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}
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return err
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}
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p := make([]byte, int(length))
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_, err = io.ReadFull(br, p)
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if err != nil {
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return err
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}
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c.QueuePacketConn.QueueIncoming(p, turbotunnel.DummyAddr{})
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}
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}
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// sendLoop reads messages from the outgoing queue and writes them,
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// length-prefixed, to conn.
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func (c *TLSPacketConn) sendLoop(conn net.Conn) error {
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bw := bufio.NewWriter(conn)
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for p := range c.QueuePacketConn.OutgoingQueue(turbotunnel.DummyAddr{}) {
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length := uint16(len(p))
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if int(length) != len(p) {
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panic(len(p))
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}
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err := binary.Write(bw, binary.BigEndian, &length)
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if err != nil {
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return err
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}
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_, err = bw.Write(p)
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if err != nil {
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return err
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}
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err = bw.Flush()
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if err != nil {
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return err
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}
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}
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return nil
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}
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