package brontide import ( "io" "net" "github.com/roasbeef/btcd/btcec" ) // Listener is an implementation of a net.Conn which executes an authenticated // key exchange and message encryption protocol dubeed "Machine" after // initial connection acceptance. See the Machine struct for additional // details w.r.t the handshake and encryption scheme used within the // connection. type Listener struct { localStatic *btcec.PrivateKey tcp *net.TCPListener } // A compile-time assertion to ensure that Conn meets the net.Listener interface. var _ net.Listener = (*Listener)(nil) // NewListener returns a new net.Listener which enforces the Brontide scheme // during both initial connection establishment and data transfer. func NewListener(localStatic *btcec.PrivateKey, listenAddr string) (*Listener, error) { addr, err := net.ResolveTCPAddr("tcp", listenAddr) if err != nil { return nil, err } l, err := net.ListenTCP("tcp", addr) if err != nil { return nil, err } return &Listener{ localStatic: localStatic, tcp: l, }, nil } // Accept waits for and returns the next connection to the listener. All // incoming connections are authenticated via the three act Brontide // key-exchange scheme. This funciton will fail with a non-nil error in the // case that either the handshake breaks down, or the remote peer doesn't know // our static public key. // // Part of the net.Listener interface. func (l *Listener) Accept() (net.Conn, error) { conn, err := l.tcp.Accept() if err != nil { return nil, err } brontideConn := &Conn{ conn: conn, noise: NewBrontideMachine(false, l.localStatic, nil), } // Attempt to carry out the first act of the handshake protocol. If the // connecting node doesn't know our long-term static public key, then // this portion will fail with a non-nil error. var actOne [ActOneSize]byte if _, err := io.ReadFull(conn, actOne[:]); err != nil { brontideConn.conn.Close() return nil, err } if err := brontideConn.noise.RecvActOne(actOne); err != nil { brontideConn.conn.Close() return nil, err } // Next, progress the handshake processes by sending over our ephemeral // key for the session along with an authenticating tag. actTwo, err := brontideConn.noise.GenActTwo() if err != nil { brontideConn.conn.Close() return nil, err } if _, err := conn.Write(actTwo[:]); err != nil { brontideConn.conn.Close() return nil, err } // Finally, finish the handshake processes by reading and decrypting // the connection peer's static public key. If this succeeds then both // sides have mutually authenticated each other. var actThree [ActThreeSize]byte if _, err := io.ReadFull(conn, actThree[:]); err != nil { brontideConn.conn.Close() return nil, err } if err := brontideConn.noise.RecvActThree(actThree); err != nil { brontideConn.conn.Close() return nil, err } return brontideConn, nil } // Close closes the listener. Any blocked Accept operations will be unblocked // and return errors. // // Part of the net.Listener interface. func (l *Listener) Close() error { return l.tcp.Close() } // Addr returns the listener's network address. // // Part of the net.Listener interface. func (l *Listener) Addr() net.Addr { return l.tcp.Addr() }