net/http: omit Content-Length in Response.Write for 1xx or 204 status

Per RFC 7230, Section 3.3.2: "A server MUST NOT send a Content-Length
header field in any response with a status code of 1xx (Informational)
or 204 (No Content).".

Fixes #16942

Change-Id: I8006c76c126304e13618966e6eafb08a3885d3cd
Reviewed-on: https://go-review.googlesource.com/28351
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/net/http/response.go b/src/net/http/response.go
index 5450d50c3ce8b0db74cb2f510686d3ac3878ba96..e04ecb9a1b4a471a66f56cd46c4b8456245c69da 100644 (file)
--- a/src/net/http/response.go
+++ b/src/net/http/response.go
@@ -300,7 +300,7 @@ func (r *Response) Write(w io.Writer) error {
        // contentLengthAlreadySent may have been already sent for
        // POST/PUT requests, even if zero length. See Issue 8180.
        contentLengthAlreadySent := tw.shouldSendContentLength()
-       if r1.ContentLength == 0 && !chunked(r1.TransferEncoding) && !contentLengthAlreadySent {
+       if r1.ContentLength == 0 && !chunked(r1.TransferEncoding) && !contentLengthAlreadySent && bodyAllowedForStatus(r.StatusCode) {
                if _, err := io.WriteString(w, "Content-Length: 0\r\n"); err != nil {
                        return err
                }

diff --git a/src/net/http/responsewrite_test.go b/src/net/http/responsewrite_test.go
index 90f6767d96b867a745199865a7e7f41bea0c7c1c..d41d89896efc42e4afaa95b452b21c4599e27613 100644 (file)
--- a/src/net/http/responsewrite_test.go
+++ b/src/net/http/responsewrite_test.go
@@ -241,7 +241,8 @@ func TestResponseWrite(t *testing.T) {
                        "HTTP/1.0 007 license to violate specs\r\nContent-Length: 0\r\n\r\n",
                },
 
-               // No stutter.
+               // No stutter.  Status code in 1xx range response should
+               // not include a Content-Length header.  See issue #16942.
                {
                        Response{
                                StatusCode: 123,
@@ -253,7 +254,23 @@ func TestResponseWrite(t *testing.T) {
                                Body:       nil,
                        },
 
-                       "HTTP/1.0 123 Sesame Street\r\nContent-Length: 0\r\n\r\n",
+                       "HTTP/1.0 123 Sesame Street\r\n\r\n",
+               },
+
+               // Status code 204 (No content) response should not include a
+               // Content-Length header.  See issue #16942.
+               {
+                       Response{
+                               StatusCode: 204,
+                               Status:     "No Content",
+                               ProtoMajor: 1,
+                               ProtoMinor: 0,
+                               Request:    dummyReq("GET"),
+                               Header:     Header{},
+                               Body:       nil,
+                       },
+
+                       "HTTP/1.0 204 No Content\r\n\r\n",
                },
        }