websocket: don't send IPv6 zone identifier in outbound request, per RFC 6874

When making a request to an IPv6 address with a zone identifier, for
exmaple [fe80::1%en0], RFC 6874 says HTTP clients must remove the zone
identifier "%en0" before writing the request for security reason.

This change removes any IPv6 zone identifer attached to URI in the Host
header field in requests.

See golang/go#9544.

Change-Id: Ie5d18a0bc5f2768a95c59ec2b159ac0abdf685e8
Reviewed-on: https://go-review.googlesource.com/13296
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

2 files changed, 83 insertions, 52 deletions

diff --git a/websocket/hybi.go b/websocket/hybi.go
index c430dce..60bbc84 100644
--- a/websocket/hybi.go
+++ b/websocket/hybi.go
@@ -372,6 +372,23 @@ func generateNonce() (nonce []byte) {
 	return
 }
 
+// removeZone removes IPv6 zone identifer from host.
+// E.g., "[fe80::1%en0]:8080" to "[fe80::1]:8080"
+func removeZone(host string) string {
+	if !strings.HasPrefix(host, "[") {
+		return host
+	}
+	i := strings.LastIndex(host, "]")
+	if i < 0 {
+		return host
+	}
+	j := strings.LastIndex(host[:i], "%")
+	if j < 0 {
+		return host
+	}
+	return host[:j] + host[i:]
+}
+
 // getNonceAccept computes the base64-encoded SHA-1 of the concatenation of
 // the nonce ("Sec-WebSocket-Key" value) with the websocket GUID string.
 func getNonceAccept(nonce []byte) (expected []byte, err error) {
@@ -391,7 +408,10 @@ func getNonceAccept(nonce []byte) (expected []byte, err error) {
 func hybiClientHandshake(config *Config, br *bufio.Reader, bw *bufio.Writer) (err error) {
 	bw.WriteString("GET " + config.Location.RequestURI() + " HTTP/1.1\r\n")
 
-	bw.WriteString("Host: " + config.Location.Host + "\r\n")
+	// According to RFC 6874, an HTTP client, proxy, or other
+	// intermediary must remove any IPv6 zone identifier attached
+	// to an outgoing URI.
+	bw.WriteString("Host: " + removeZone(config.Location.Host) + "\r\n")
 	bw.WriteString("Upgrade: websocket\r\n")
 	bw.WriteString("Connection: Upgrade\r\n")
 	nonce := generateNonce()
diff --git a/websocket/hybi_test.go b/websocket/hybi_test.go
index 722ab31..9504aa2 100644
--- a/websocket/hybi_test.go
+++ b/websocket/hybi_test.go
@@ -31,63 +31,74 @@ func TestSecWebSocketAccept(t *testing.T) {
 }
 
 func TestHybiClientHandshake(t *testing.T) {
-	b := bytes.NewBuffer([]byte{})
-	bw := bufio.NewWriter(b)
-	br := bufio.NewReader(strings.NewReader(`HTTP/1.1 101 Switching Protocols
+	type test struct {
+		url, host string
+	}
+	tests := []test{
+		{"ws://server.example.com/chat", "server.example.com"},
+		{"ws://127.0.0.1/chat", "127.0.0.1"},
+	}
+	if _, err := url.ParseRequestURI("http://[fe80::1%25lo0]"); err == nil {
+		tests = append(tests, test{"ws://[fe80::1%25lo0]/chat", "[fe80::1]"})
+	}
+
+	for _, tt := range tests {
+		var b bytes.Buffer
+		bw := bufio.NewWriter(&b)
+		br := bufio.NewReader(strings.NewReader(`HTTP/1.1 101 Switching Protocols
 Upgrade: websocket
 Connection: Upgrade
 Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
 Sec-WebSocket-Protocol: chat
 
 `))
-	var err error
-	config := new(Config)
-	config.Location, err = url.ParseRequestURI("ws://server.example.com/chat")
-	if err != nil {
-		t.Fatal("location url", err)
-	}
-	config.Origin, err = url.ParseRequestURI("http://example.com")
-	if err != nil {
-		t.Fatal("origin url", err)
-	}
-	config.Protocol = append(config.Protocol, "chat")
-	config.Protocol = append(config.Protocol, "superchat")
-	config.Version = ProtocolVersionHybi13
-
-	config.handshakeData = map[string]string{
-		"key": "dGhlIHNhbXBsZSBub25jZQ==",
-	}
-	err = hybiClientHandshake(config, br, bw)
-	if err != nil {
-		t.Errorf("handshake failed: %v", err)
-	}
-	req, err := http.ReadRequest(bufio.NewReader(b))
-	if err != nil {
-		t.Fatalf("read request: %v", err)
-	}
-	if req.Method != "GET" {
-		t.Errorf("request method expected GET, but got %q", req.Method)
-	}
-	if req.URL.Path != "/chat" {
-		t.Errorf("request path expected /chat, but got %q", req.URL.Path)
-	}
-	if req.Proto != "HTTP/1.1" {
-		t.Errorf("request proto expected HTTP/1.1, but got %q", req.Proto)
-	}
-	if req.Host != "server.example.com" {
-		t.Errorf("request Host expected server.example.com, but got %v", req.Host)
-	}
-	var expectedHeader = map[string]string{
-		"Connection":             "Upgrade",
-		"Upgrade":                "websocket",
-		"Sec-Websocket-Key":      config.handshakeData["key"],
-		"Origin":                 config.Origin.String(),
-		"Sec-Websocket-Protocol": "chat, superchat",
-		"Sec-Websocket-Version":  fmt.Sprintf("%d", ProtocolVersionHybi13),
-	}
-	for k, v := range expectedHeader {
-		if req.Header.Get(k) != v {
-			t.Errorf(fmt.Sprintf("%s expected %q but got %q", k, v, req.Header.Get(k)))
+		var err error
+		var config Config
+		config.Location, err = url.ParseRequestURI(tt.url)
+		if err != nil {
+			t.Fatal("location url", err)
+		}
+		config.Origin, err = url.ParseRequestURI("http://example.com")
+		if err != nil {
+			t.Fatal("origin url", err)
+		}
+		config.Protocol = append(config.Protocol, "chat")
+		config.Protocol = append(config.Protocol, "superchat")
+		config.Version = ProtocolVersionHybi13
+		config.handshakeData = map[string]string{
+			"key": "dGhlIHNhbXBsZSBub25jZQ==",
+		}
+		if err := hybiClientHandshake(&config, br, bw); err != nil {
+			t.Fatal("handshake", err)
+		}
+		req, err := http.ReadRequest(bufio.NewReader(&b))
+		if err != nil {
+			t.Fatal("read request", err)
+		}
+		if req.Method != "GET" {
+			t.Errorf("request method expected GET, but got %s", req.Method)
+		}
+		if req.URL.Path != "/chat" {
+			t.Errorf("request path expected /chat, but got %s", req.URL.Path)
+		}
+		if req.Proto != "HTTP/1.1" {
+			t.Errorf("request proto expected HTTP/1.1, but got %s", req.Proto)
+		}
+		if req.Host != tt.host {
+			t.Errorf("request host expected %s, but got %s", tt.host, req.Host)
+		}
+		var expectedHeader = map[string]string{
+			"Connection":             "Upgrade",
+			"Upgrade":                "websocket",
+			"Sec-Websocket-Key":      config.handshakeData["key"],
+			"Origin":                 config.Origin.String(),
+			"Sec-Websocket-Protocol": "chat, superchat",
+			"Sec-Websocket-Version":  fmt.Sprintf("%d", ProtocolVersionHybi13),
+		}
+		for k, v := range expectedHeader {
+			if req.Header.Get(k) != v {
+				t.Errorf("%s expected %s, but got %v", k, v, req.Header.Get(k))
+			}
 		}
 	}
 }