lnd.xprv/lndc/listener.go
2016-01-16 19:25:44 -08:00

207 lines
5.2 KiB
Go

package lndc
import (
"bytes"
"fmt"
"net"
"github.com/btcsuite/btcd/btcec"
"github.com/btcsuite/btcutil"
"github.com/btcsuite/fastsha256"
"github.com/codahale/chacha20poly1305"
)
// Listener...
type Listener struct {
longTermPriv *btcec.PrivateKey
tcp *net.TCPListener
}
var _ net.Listener = (*Listener)(nil)
// NewListener...
func NewListener(localPriv *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{localPriv, l}, nil
}
// Accept waits for and returns the next connection to the listener.
// Part of the net.Listener interface.
func (l *Listener) Accept() (c net.Conn, err error) {
conn, err := l.tcp.Accept()
if err != nil {
return nil, nil
}
lndc := NewConn(l.longTermPriv, conn)
// Exchange an ephemeral public key with the remote connection in order
// to establish a confidential connection before we attempt to
// authenticated.
ephemeralKey, err := l.createCipherConn(lndc)
if err != nil {
return nil, err
}
// Now that we've established an encrypted connection, authenticate the
// identity of the remote host.
ephemeralPub := ephemeralKey.PubKey().SerializeCompressed()
if err := l.authenticateConnection(lndc, ephemeralPub); err != nil {
lndc.Close()
return nil, err
}
return lndc, nil
}
// createCipherConn....
func (l *Listener) createCipherConn(lnConn *Conn) (*btcec.PrivateKey, error) {
var err error
var theirEphPubBytes []byte
// First, read and deserialize their ephemeral public key.
theirEphPubBytes, err = readClear(lnConn.conn)
if err != nil {
return nil, err
}
if len(theirEphPubBytes) != 33 {
return nil, fmt.Errorf("Got invalid %d byte eph pubkey %x\n",
len(theirEphPubBytes), theirEphPubBytes)
}
theirEphPub, err := btcec.ParsePubKey(theirEphPubBytes, btcec.S256())
if err != nil {
return nil, err
}
// Once we've parsed and verified their key, generate, and send own
// ephemeral key pair for use within this session.
myEph, err := btcec.NewPrivateKey(btcec.S256())
if err != nil {
return nil, err
}
if _, err := writeClear(lnConn.conn, myEph.PubKey().SerializeCompressed()); err != nil {
return nil, err
}
// Now that we have both keys, do non-interactive diffie with ephemeral
// pubkeys, sha256 for good luck.
sessionKey := fastsha256.Sum256(
btcec.GenerateSharedSecret(myEph, theirEphPub),
)
lnConn.chachaStream, err = chacha20poly1305.New(sessionKey[:])
// display private key for debug only
fmt.Printf("made session key %x\n", sessionKey)
lnConn.remoteNonceInt = 1 << 63
lnConn.myNonceInt = 0
lnConn.remotePub = theirEphPub
lnConn.authed = false
return myEph, nil
}
// AuthListen...
func (l *Listener) authenticateConnection(lnConn *Conn, localEphPubBytes []byte) error {
var err error
// TODO(roasbeef): should be using read/write clear here?
slice := make([]byte, 73)
n, err := lnConn.conn.Read(slice)
if err != nil {
fmt.Printf("Read error: %s\n", err.Error())
return err
}
fmt.Printf("read %d bytes\n", n)
authmsg := slice[:n]
if len(authmsg) != 53 && len(authmsg) != 73 {
return fmt.Errorf("got auth message of %d bytes, "+
"expect 53 or 73", len(authmsg))
}
myPKH := btcutil.Hash160(l.longTermPriv.PubKey().SerializeCompressed())
if !bytes.Equal(myPKH, authmsg[33:53]) {
return fmt.Errorf(
"remote host asking for PKH %x, that's not me", authmsg[33:53])
}
// do DH with id keys
theirPub, err := btcec.ParsePubKey(authmsg[:33], btcec.S256())
if err != nil {
return err
}
idDH := fastsha256.Sum256(
btcec.GenerateSharedSecret(lnConn.longTermPriv, theirPub),
)
myDHproof := btcutil.Hash160(
append(lnConn.remotePub.SerializeCompressed(), idDH[:]...),
)
theirDHproof := btcutil.Hash160(append(localEphPubBytes, idDH[:]...))
// If they already know our public key, then execute the fast path.
// Verify their DH proof, and send our own.
if len(authmsg) == 73 {
// Verify their DH proof.
if !bytes.Equal(authmsg[53:], theirDHproof) {
return fmt.Errorf("invalid DH proof from %s",
lnConn.RemoteAddr().String())
}
// Their DH proof checks out, so send ours now.
if _, err = lnConn.conn.Write(myDHproof); err != nil {
return err
}
} else {
// Otherwise, they don't yet know our public key. So we'll send
// it over to them, so we can both compute the DH proof.
msg := append(l.longTermPriv.PubKey().SerializeCompressed(), myDHproof...)
if _, err = lnConn.conn.Write(msg); err != nil {
return err
}
resp := make([]byte, 20)
if _, err := lnConn.conn.Read(resp); err != nil {
return err
}
// Verify their DH proof.
if bytes.Equal(resp, theirDHproof) == false {
return fmt.Errorf("Invalid DH proof %x", theirDHproof)
}
}
theirAdr := btcutil.Hash160(theirPub.SerializeCompressed())
copy(lnConn.remoteLNId[:], theirAdr[:16])
lnConn.remotePub = theirPub
lnConn.authed = true
return 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()
}