[release-branch.go1.21] crypto/tls: QUIC: fix panics when processing post-handshake messages

The check for fragmentary post-handshake messages in QUICConn.HandleData
was reversed, resulting in a potential panic when HandleData receives
a partial message.

In addition, HandleData wasn't checking the size of buffered
post-handshake messages. Produce an error when a post-handshake
message is larger than maxHandshake.

TestQUICConnectionState was using an onHandleCryptoData hook
in runTestQUICConnection that was never being called.
(I think it was inadvertently removed at some point while
the CL was in review.) Fix this test while making the hook
more general.

For #62266
Fixes #62290

Change-Id: I210b70634e50beb456ab3977eb11272b8724c241
Reviewed-on: https://go-review.googlesource.com/c/go/+/522595
Run-TryBot: Damien Neil <dneil@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Marten Seemann <martenseemann@gmail.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
(cherry picked from commit e92c0f846c54d88f479b1c48f0dbc001d2ff53e9)
Reviewed-on: https://go-review.googlesource.com/c/go/+/523039
Auto-Submit: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

2 files changed, 74 insertions, 16 deletions

diff --git a/src/crypto/tls/quic.go b/src/crypto/tls/quic.go
index 286302f0ec..ba5c2af0fb 100644
--- a/src/crypto/tls/quic.go
+++ b/src/crypto/tls/quic.go
@@ -228,16 +228,22 @@ func (q *QUICConn) HandleData(level QUICEncryptionLevel, data []byte) error {
 		return nil
 	}
 	// The handshake goroutine has exited.
+	c.handshakeMutex.Lock()
+	defer c.handshakeMutex.Unlock()
 	c.hand.Write(c.quic.readbuf)
 	c.quic.readbuf = nil
 	for q.conn.hand.Len() >= 4 && q.conn.handshakeErr == nil {
 		b := q.conn.hand.Bytes()
 		n := int(b[1])<<16 | int(b[2])<<8 | int(b[3])
-		if 4+n < len(b) {
+		if n > maxHandshake {
+			q.conn.handshakeErr = fmt.Errorf("tls: handshake message of length %d bytes exceeds maximum of %d bytes", n, maxHandshake)
+			break
+		}
+		if len(b) < 4+n {
 			return nil
 		}
 		if err := q.conn.handlePostHandshakeMessage(); err != nil {
-			return quicError(err)
+			q.conn.handshakeErr = err
 		}
 	}
 	if q.conn.handshakeErr != nil {
diff --git a/src/crypto/tls/quic_test.go b/src/crypto/tls/quic_test.go
index 9a29fa56b8..323906a2f2 100644
--- a/src/crypto/tls/quic_test.go
+++ b/src/crypto/tls/quic_test.go
@@ -85,7 +85,7 @@ func (q *testQUICConn) setWriteSecret(level QUICEncryptionLevel, suite uint16, s
 
 var errTransportParametersRequired = errors.New("transport parameters required")
 
-func runTestQUICConnection(ctx context.Context, cli, srv *testQUICConn, onHandleCryptoData func()) error {
+func runTestQUICConnection(ctx context.Context, cli, srv *testQUICConn, onEvent func(e QUICEvent, src, dst *testQUICConn) bool) error {
 	a, b := cli, srv
 	for _, c := range []*testQUICConn{a, b} {
 		if !c.conn.conn.quic.started {
@@ -97,6 +97,9 @@ func runTestQUICConnection(ctx context.Context, cli, srv *testQUICConn, onHandle
 	idleCount := 0
 	for {
 		e := a.conn.NextEvent()
+		if onEvent != nil && onEvent(e, a, b) {
+			continue
+		}
 		switch e.Kind {
 		case QUICNoEvent:
 			idleCount++
@@ -211,6 +214,37 @@ func TestQUICSessionResumption(t *testing.T) {
 	}
 }
 
+func TestQUICFragmentaryData(t *testing.T) {
+	clientConfig := testConfig.Clone()
+	clientConfig.MinVersion = VersionTLS13
+	clientConfig.ClientSessionCache = NewLRUClientSessionCache(1)
+	clientConfig.ServerName = "example.go.dev"
+
+	serverConfig := testConfig.Clone()
+	serverConfig.MinVersion = VersionTLS13
+
+	cli := newTestQUICClient(t, clientConfig)
+	cli.conn.SetTransportParameters(nil)
+	srv := newTestQUICServer(t, serverConfig)
+	srv.conn.SetTransportParameters(nil)
+	onEvent := func(e QUICEvent, src, dst *testQUICConn) bool {
+		if e.Kind == QUICWriteData {
+			// Provide the data one byte at a time.
+			for i := range e.Data {
+				if err := dst.conn.HandleData(e.Level, e.Data[i:i+1]); err != nil {
+					t.Errorf("HandleData: %v", err)
+					break
+				}
+			}
+			return true
+		}
+		return false
+	}
+	if err := runTestQUICConnection(context.Background(), cli, srv, onEvent); err != nil {
+		t.Fatalf("error during first connection handshake: %v", err)
+	}
+}
+
 func TestQUICPostHandshakeClientAuthentication(t *testing.T) {
 	// RFC 9001, Section 4.4.
 	config := testConfig.Clone()
@@ -264,6 +298,28 @@ func TestQUICPostHandshakeKeyUpdate(t *testing.T) {
 	}
 }
 
+func TestQUICPostHandshakeMessageTooLarge(t *testing.T) {
+	config := testConfig.Clone()
+	config.MinVersion = VersionTLS13
+	cli := newTestQUICClient(t, config)
+	cli.conn.SetTransportParameters(nil)
+	srv := newTestQUICServer(t, config)
+	srv.conn.SetTransportParameters(nil)
+	if err := runTestQUICConnection(context.Background(), cli, srv, nil); err != nil {
+		t.Fatalf("error during connection handshake: %v", err)
+	}
+
+	size := maxHandshake + 1
+	if err := cli.conn.HandleData(QUICEncryptionLevelApplication, []byte{
+		byte(typeNewSessionTicket),
+		byte(size >> 16),
+		byte(size >> 8),
+		byte(size),
+	}); err == nil {
+		t.Fatalf("%v-byte post-handshake message: got no error, want one", size)
+	}
+}
+
 func TestQUICHandshakeError(t *testing.T) {
 	clientConfig := testConfig.Clone()
 	clientConfig.MinVersion = VersionTLS13
@@ -298,26 +354,22 @@ func TestQUICConnectionState(t *testing.T) {
 	cli.conn.SetTransportParameters(nil)
 	srv := newTestQUICServer(t, config)
 	srv.conn.SetTransportParameters(nil)
-	onHandleCryptoData := func() {
+	onEvent := func(e QUICEvent, src, dst *testQUICConn) bool {
 		cliCS := cli.conn.ConnectionState()
-		cliWantALPN := ""
 		if _, ok := cli.readSecret[QUICEncryptionLevelApplication]; ok {
-			cliWantALPN = "h3"
-		}
-		if want, got := cliCS.NegotiatedProtocol, cliWantALPN; want != got {
-			t.Errorf("cli.ConnectionState().NegotiatedProtocol = %q, want %q", want, got)
+			if want, got := cliCS.NegotiatedProtocol, "h3"; want != got {
+				t.Errorf("cli.ConnectionState().NegotiatedProtocol = %q, want %q", want, got)
+			}
 		}
-
 		srvCS := srv.conn.ConnectionState()
-		srvWantALPN := ""
 		if _, ok := srv.readSecret[QUICEncryptionLevelHandshake]; ok {
-			srvWantALPN = "h3"
-		}
-		if want, got := srvCS.NegotiatedProtocol, srvWantALPN; want != got {
-			t.Errorf("srv.ConnectionState().NegotiatedProtocol = %q, want %q", want, got)
+			if want, got := srvCS.NegotiatedProtocol, "h3"; want != got {
+				t.Errorf("srv.ConnectionState().NegotiatedProtocol = %q, want %q", want, got)
+			}
 		}
+		return false
 	}
-	if err := runTestQUICConnection(context.Background(), cli, srv, onHandleCryptoData); err != nil {
+	if err := runTestQUICConnection(context.Background(), cli, srv, onEvent); err != nil {
 		t.Fatalf("error during connection handshake: %v", err)
 	}
 }