net/http/cgi: Correctly pass down the REMOTE_PORT value for CGI requests.

Currently when we get a CGI or FCGI request, the remote port of the client
is hard coded to zero, despite nearly every webserver passing down the
REMOTE_PORT variable.

This was likely originally excluded because the CGI RFC (rfc3875) does not
mention anything about the remote port of the client. However every webserver
tested does pass REMOTE_PORT down. This includes Apache 2.2, Apache 2.4,
nginx and lighttpd.

Fixes #8351

Change-Id: I4c6366cb39f0ccc05e038bd31d85f93b76e8d0c8
Reviewed-on: https://go-review.googlesource.com/1750Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/http/cgi/child.go

@@ -132,9 +132,9 @@ func RequestFromMap(params map[string]string) (*http.Request, error) {
 	}
 
 	// Request.RemoteAddr has its port set by Go's standard http
-	// server, so we do here too. We don't have one, though, so we
-	// use a dummy one.
-	r.RemoteAddr = net.JoinHostPort(params["REMOTE_ADDR"], "0")
+	// server, so we do here too.
+	remotePort, _ := strconv.Atoi(params["REMOTE_PORT"]) // zero if unset or invalid
+	r.RemoteAddr = net.JoinHostPort(params["REMOTE_ADDR"], strconv.Itoa(remotePort))
 
 	return r, nil
 }

src/net/http/cgi/child_test.go

@@ -22,6 +22,7 @@ func TestRequest(t *testing.T) {
 		"CONTENT_LENGTH":  "123",
 		"CONTENT_TYPE":    "text/xml",
 		"REMOTE_ADDR":     "5.6.7.8",
+		"REMOTE_PORT":     "54321",
 	}
 	req, err := RequestFromMap(env)
 	if err != nil {
@@ -60,7 +61,7 @@ func TestRequest(t *testing.T) {
 	if req.TLS != nil {
 		t.Errorf("expected nil TLS")
 	}
-	if e, g := "5.6.7.8:0", req.RemoteAddr; e != g {
+	if e, g := "5.6.7.8:54321", req.RemoteAddr; e != g {
 		t.Errorf("RemoteAddr: got %q; want %q", g, e)
 	}
 }
@@ -129,3 +130,21 @@ func TestRequestWithoutRequestURI(t *testing.T) {
 		t.Errorf("URL = %q; want %q", g, e)
 	}
 }
+
+func TestRequestWithoutRemotePort(t *testing.T) {
+	env := map[string]string{
+		"SERVER_PROTOCOL": "HTTP/1.1",
+		"HTTP_HOST":       "example.com",
+		"REQUEST_METHOD":  "GET",
+		"REQUEST_URI":     "/path?a=b",
+		"CONTENT_LENGTH":  "123",
+		"REMOTE_ADDR":     "5.6.7.8",
+	}
+	req, err := RequestFromMap(env)
+	if err != nil {
+		t.Fatalf("RequestFromMap: %v", err)
+	}
+	if e, g := "5.6.7.8:0", req.RemoteAddr; e != g {
+		t.Errorf("RemoteAddr: got %q; want %q", g, e)
+	}
+}