--- /dev/null
+package torrent
+
+import (
+ "bytes"
+ "encoding/hex"
+ "fmt"
+ "io"
+ "net"
+ "time"
+
+ pp "github.com/anacrolix/torrent/peer_protocol"
+
+ "github.com/anacrolix/missinggo"
+ "github.com/anacrolix/torrent/metainfo"
+ "github.com/anacrolix/torrent/mse"
+)
+
+func handshakeWriter(w io.Writer, bb <-chan []byte, done chan<- error) {
+ var err error
+ for b := range bb {
+ _, err = w.Write(b)
+ if err != nil {
+ break
+ }
+ }
+ done <- err
+}
+
+type (
+ peerExtensionBytes [8]byte
+ peerID [20]byte
+)
+
+func (pex *peerExtensionBytes) SupportsExtended() bool {
+ return pex[5]&0x10 != 0
+}
+
+func (pex *peerExtensionBytes) SupportsDHT() bool {
+ return pex[7]&0x01 != 0
+}
+
+func (pex *peerExtensionBytes) SupportsFast() bool {
+ return pex[7]&0x04 != 0
+}
+
+type handshakeResult struct {
+ peerExtensionBytes
+ peerID
+ metainfo.Hash
+}
+
+// ih is nil if we expect the peer to declare the InfoHash, such as when the
+// peer initiated the connection. Returns ok if the handshake was successful,
+// and err if there was an unexpected condition other than the peer simply
+// abandoning the handshake.
+func handshake(sock io.ReadWriter, ih *metainfo.Hash, peerID [20]byte, extensions peerExtensionBytes) (res handshakeResult, ok bool, err error) {
+ // Bytes to be sent to the peer. Should never block the sender.
+ postCh := make(chan []byte, 4)
+ // A single error value sent when the writer completes.
+ writeDone := make(chan error, 1)
+ // Performs writes to the socket and ensures posts don't block.
+ go handshakeWriter(sock, postCh, writeDone)
+
+ defer func() {
+ close(postCh) // Done writing.
+ if !ok {
+ return
+ }
+ if err != nil {
+ panic(err)
+ }
+ // Wait until writes complete before returning from handshake.
+ err = <-writeDone
+ if err != nil {
+ err = fmt.Errorf("error writing: %s", err)
+ }
+ }()
+
+ post := func(bb []byte) {
+ select {
+ case postCh <- bb:
+ default:
+ panic("mustn't block while posting")
+ }
+ }
+
+ post([]byte(pp.Protocol))
+ post(extensions[:])
+ if ih != nil { // We already know what we want.
+ post(ih[:])
+ post(peerID[:])
+ }
+ var b [68]byte
+ _, err = io.ReadFull(sock, b[:68])
+ if err != nil {
+ err = nil
+ return
+ }
+ if string(b[:20]) != pp.Protocol {
+ return
+ }
+ missinggo.CopyExact(&res.peerExtensionBytes, b[20:28])
+ missinggo.CopyExact(&res.Hash, b[28:48])
+ missinggo.CopyExact(&res.peerID, b[48:68])
+ peerExtensions.Add(hex.EncodeToString(res.peerExtensionBytes[:]), 1)
+
+ // TODO: Maybe we can just drop peers here if we're not interested. This
+ // could prevent them trying to reconnect, falsely believing there was
+ // just a problem.
+ if ih == nil { // We were waiting for the peer to tell us what they wanted.
+ post(res.Hash[:])
+ post(peerID[:])
+ }
+
+ ok = true
+ return
+}
+
+// Wraps a raw connection and provides the interface we want for using the
+// connection in the message loop.
+type deadlineReader struct {
+ nc net.Conn
+ r io.Reader
+}
+
+func (r deadlineReader) Read(b []byte) (int, error) {
+ // Keep-alives should be received every 2 mins. Give a bit of gracetime.
+ err := r.nc.SetReadDeadline(time.Now().Add(150 * time.Second))
+ if err != nil {
+ return 0, fmt.Errorf("error setting read deadline: %s", err)
+ }
+ return r.r.Read(b)
+}
+
+func handleEncryption(
+ rw io.ReadWriter,
+ skeys mse.SecretKeyIter,
+ policy EncryptionPolicy,
+) (
+ ret io.ReadWriter,
+ headerEncrypted bool,
+ cryptoMethod uint32,
+ err error,
+) {
+ if !policy.ForceEncryption {
+ var protocol [len(pp.Protocol)]byte
+ _, err = io.ReadFull(rw, protocol[:])
+ if err != nil {
+ return
+ }
+ rw = struct {
+ io.Reader
+ io.Writer
+ }{
+ io.MultiReader(bytes.NewReader(protocol[:]), rw),
+ rw,
+ }
+ if string(protocol[:]) == pp.Protocol {
+ ret = rw
+ return
+ }
+ }
+ headerEncrypted = true
+ ret, err = mse.ReceiveHandshake(rw, skeys, func(provides uint32) uint32 {
+ cryptoMethod = func() uint32 {
+ switch {
+ case policy.ForceEncryption:
+ return mse.CryptoMethodRC4
+ case policy.DisableEncryption:
+ return mse.CryptoMethodPlaintext
+ case policy.PreferNoEncryption && provides&mse.CryptoMethodPlaintext != 0:
+ return mse.CryptoMethodPlaintext
+ default:
+ return mse.DefaultCryptoSelector(provides)
+ }
+ }()
+ return cryptoMethod
+ })
+ return
+}