package torrent import ( "bytes" "encoding/hex" "fmt" "io" "net" "time" "github.com/anacrolix/missinggo" "github.com/anacrolix/torrent/metainfo" "github.com/anacrolix/torrent/mse" pp "github.com/anacrolix/torrent/peer_protocol" ) type ExtensionBit uint const ( ExtensionBitDHT = 0 // http://www.bittorrent.org/beps/bep_0005.html ExtensionBitExtended = 20 // http://www.bittorrent.org/beps/bep_0010.html ExtensionBitFast = 2 // http://www.bittorrent.org/beps/bep_0006.html ) 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 ) func (pex peerExtensionBytes) SupportsExtended() bool { return pex.GetBit(ExtensionBitExtended) } func (pex peerExtensionBytes) SupportsDHT() bool { return pex.GetBit(ExtensionBitDHT) } func (pex peerExtensionBytes) SupportsFast() bool { return pex.GetBit(ExtensionBitFast) } func (pex *peerExtensionBytes) SetBit(bit ExtensionBit) { pex[7-bit/8] |= 1 << bit % 8 } func (pex peerExtensionBytes) GetBit(bit ExtensionBit) bool { return pex[7-bit/8]&(1<<(bit%8)) != 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 }