verify the server's certificate using tls.Config.VerifyPeerCertificate

Fixes #2.

README.md

@@ -9,4 +9,3 @@ This is an implementation of the [libp2p transport](https://github.com/libp2p/go
 ## Known limitations
 
 * currently only works with RSA host keys
-* [#2](https://github.com/marten-seemann/libp2p-quic-transport/issues/2)

conn_test.go

@@ -80,14 +80,14 @@ var _ = Describe("Connection", func() {
 		thirdPartyID, err := peer.IDFromPrivateKey(createPeer())
 		Expect(err).ToNot(HaveOccurred())
 
-		serverAddrChan, _ := runServer()
+		serverAddrChan, serverConnChan := runServer()
 		clientTransport, err := NewTransport(clientKey)
 		Expect(err).ToNot(HaveOccurred())
 		serverAddr := <-serverAddrChan
 		// dial, but expect the wrong peer ID
 		_, err = clientTransport.Dial(context.Background(), serverAddr, thirdPartyID)
-		Expect(err).To(MatchError("peer IDs don't match"))
-		// TODO(#2): don't accept a connection if the client's peer verification fails
-		// Consistently(serverConnChan).ShouldNot(Receive())
+		Expect(err).To(HaveOccurred())
+		Expect(err.Error()).To(ContainSubstring("TLS handshake error: bad certificate"))
+		Consistently(serverConnChan).ShouldNot(Receive())
 	})
 })

crypto.go

@@ -10,8 +10,6 @@ import (
 	"math/big"
 	"time"
 
-	"github.com/lucas-clemente/quic-go"
-
 	"github.com/gogo/protobuf/proto"
 	ic "github.com/libp2p/go-libp2p-crypto"
 	pb "github.com/libp2p/go-libp2p-crypto/pb"
@@ -20,10 +18,6 @@ import (
 // mint certificate selection is broken.
 const hostname = "quic.ipfs"
 
-type connectionStater interface {
-	ConnectionState() quic.ConnectionState
-}
-
 // TODO: make this private
 func GenerateConfig(privKey ic.PrivKey) (*tls.Config, error) {
 	key, hostCert, err := keyToCertificate(privKey)
@@ -63,17 +57,16 @@ func GenerateConfig(privKey ic.PrivKey) (*tls.Config, error) {
 	}, nil
 }
 
-func getRemotePubKey(conn connectionStater) (ic.PubKey, error) {
-	certChain := conn.ConnectionState().PeerCertificates
-	if len(certChain) != 2 {
+func getRemotePubKey(chain []*x509.Certificate) (ic.PubKey, error) {
+	if len(chain) != 2 {
 		return nil, errors.New("expected 2 certificates in the chain")
 	}
 	pool := x509.NewCertPool()
-	pool.AddCert(certChain[1])
-	if _, err := certChain[0].Verify(x509.VerifyOptions{Roots: pool}); err != nil {
+	pool.AddCert(chain[1])
+	if _, err := chain[0].Verify(x509.VerifyOptions{Roots: pool}); err != nil {
 		return nil, err
 	}
-	remotePubKey, err := x509.MarshalPKIXPublicKey(certChain[1].PublicKey)
+	remotePubKey, err := x509.MarshalPKIXPublicKey(chain[1].PublicKey)
 	if err != nil {
 		return nil, err
 	}

listener.go

@@ -60,7 +60,7 @@ func (l *listener) Accept() (tpt.Conn, error) {
 	if err != nil {
 		return nil, err
 	}
-	remotePubKey, err := getRemotePubKey(sess)
+	remotePubKey, err := getRemotePubKey(sess.ConnectionState().PeerCertificates)
 	if err != nil {
 		return nil, err
 	}

transport.go

@@ -2,6 +2,7 @@ package libp2pquic
 
 import (
 	"context"
+	"crypto/x509"
 	"errors"
 
 	ic "github.com/libp2p/go-libp2p-crypto"
@@ -45,11 +46,27 @@ func (t *transport) Dial(ctx context.Context, raddr ma.Multiaddr, p peer.ID) (tp
 	if err != nil {
 		return nil, err
 	}
-	sess, err := quicDialAddr(host, tlsConf, &quic.Config{Versions: []quic.VersionNumber{101}})
-	if err != nil {
-		return nil, err
+	var remotePubKey ic.PubKey
+	tlsConf.VerifyPeerCertificate = func(rawCerts [][]byte, _ [][]*x509.Certificate) error {
+		chain := make([]*x509.Certificate, len(rawCerts))
+		for i := 0; i < len(rawCerts); i++ {
+			cert, err := x509.ParseCertificate(rawCerts[i])
+			if err != nil {
+				return err
+			}
+			chain[i] = cert
+		}
+		var err error
+		remotePubKey, err = getRemotePubKey(chain)
+		if err != nil {
+			return err
+		}
+		if !p.MatchesPublicKey(remotePubKey) {
+			return errors.New("peer IDs don't match")
+		}
+		return nil
 	}
-	remotePubKey, err := getRemotePubKey(sess)
+	sess, err := quicDialAddr(host, tlsConf, &quic.Config{Versions: []quic.VersionNumber{101}})
 	if err != nil {
 		return nil, err
 	}
@@ -57,11 +74,6 @@ func (t *transport) Dial(ctx context.Context, raddr ma.Multiaddr, p peer.ID) (tp
 	if err != nil {
 		return nil, err
 	}
-	if !p.MatchesPublicKey(remotePubKey) {
-		err := errors.New("peer IDs don't match")
-		sess.Close(err)
-		return nil, err
-	}
 	return &conn{
 		privKey:         t.privKey,
 		localPeer:       t.localPeer,