http: avoid server crash on malformed client request

R=r, rsc
CC=golang-dev
https://golang.org/cl/206079

src/pkg/websocket/server.go

@@ -38,20 +38,34 @@ type Handler func(*Conn)
 
 // ServeHTTP implements the http.Handler interface for a Web Socket.
 func (f Handler) ServeHTTP(c *http.Conn, req *http.Request) {
-	if req.Method != "GET" || req.Proto != "HTTP/1.1" ||
-		req.Header["Upgrade"] != "WebSocket" ||
-		req.Header["Connection"] != "Upgrade" {
-		c.WriteHeader(http.StatusNotFound)
-		io.WriteString(c, "must use websocket to connect here")
+	if req.Method != "GET" || req.Proto != "HTTP/1.1" {
+		c.WriteHeader(http.StatusBadRequest)
+		io.WriteString(c, "Unexpected request")
 		return
 	}
+	if v, present := req.Header["Upgrade"]; !present || v != "WebSocket" {
+		c.WriteHeader(http.StatusBadRequest)
+		io.WriteString(c, "missing Upgrade: WebSocket header")
+		return
+	}
+	if v, present := req.Header["Connection"]; !present || v != "Upgrade" {
+		c.WriteHeader(http.StatusBadRequest)
+		io.WriteString(c, "missing Connection: Upgrade header")
+		return
+	}
+	origin, present := req.Header["Origin"]
+	if !present {
+		c.WriteHeader(http.StatusBadRequest)
+		io.WriteString(c, "missing Origin header")
+		return
+	}
+
 	rwc, buf, err := c.Hijack()
 	if err != nil {
 		panic("Hijack failed: ", err.String())
 		return
 	}
 	defer rwc.Close()
-	origin := req.Header["Origin"]
 	location := "ws://" + req.Host + req.URL.Path
 
 	// TODO(ukai): verify origin,location,protocol.
@@ -61,9 +75,9 @@ func (f Handler) ServeHTTP(c *http.Conn, req *http.Request) {
 	buf.WriteString("Connection: Upgrade\r\n")
 	buf.WriteString("WebSocket-Origin: " + origin + "\r\n")
 	buf.WriteString("WebSocket-Location: " + location + "\r\n")
-	protocol := ""
+	protocol, present := req.Header["Websocket-Protocol"]
 	// canonical header key of WebSocket-Protocol.
-	if protocol, found := req.Header["Websocket-Protocol"]; found {
+	if present {
 		buf.WriteString("WebSocket-Protocol: " + protocol + "\r\n")
 	}
 	buf.WriteString("\r\n")

src/pkg/websocket/websocket_test.go

@@ -6,6 +6,7 @@ package websocket
 
 import (
 	"bytes"
+	"fmt"
 	"http"
 	"io"
 	"log"
@@ -59,3 +60,17 @@ func TestEcho(t *testing.T) {
 	}
 	ws.Close()
 }
+
+func TestHTTP(t *testing.T) {
+	once.Do(startServer)
+
+	r, _, err := http.Get(fmt.Sprintf("http://%s/echo", serverAddr))
+	if err != nil {
+		t.Errorf("Get: error %v", err)
+		return
+	}
+	if r.StatusCode != http.StatusBadRequest {
+		t.Errorf("Get: got status %d", r.StatusCode)
+		return
+	}
+}