net/http: don't send body on redirects for 301, 302, 303 when GetBody is set

The presence of Request.GetBody being set on a request was causing all
redirected requests to have a body, even if the redirect status didn't
warrant one.

This bug came from 307/308 support (https://golang.org/cl/29852) which
removed the line that set req.Body to nil after POST/PUT redirects.

Change-Id: I2a4dd5320f810ae25cfd8ea8ca7c9700e5dbd369
Reviewed-on: https://go-review.googlesource.com/35633
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>

src/net/http/client.go

@@ -413,11 +413,12 @@ func (c *Client) checkRedirect(req *Request, via []*Request) error {
 
 // redirectBehavior describes what should happen when the
 // client encounters a 3xx status code from the server
-func redirectBehavior(reqMethod string, resp *Response, ireq *Request) (redirectMethod string, shouldRedirect bool) {
+func redirectBehavior(reqMethod string, resp *Response, ireq *Request) (redirectMethod string, shouldRedirect, includeBody bool) {
 	switch resp.StatusCode {
 	case 301, 302, 303:
 		redirectMethod = reqMethod
 		shouldRedirect = true
+		includeBody = false
 
 		// RFC 2616 allowed automatic redirection only with GET and
 		// HEAD requests. RFC 7231 lifts this restriction, but we still
@@ -429,6 +430,7 @@ func redirectBehavior(reqMethod string, resp *Response, ireq *Request) (redirect
 	case 307, 308:
 		redirectMethod = reqMethod
 		shouldRedirect = true
+		includeBody = true
 
 		// Treat 307 and 308 specially, since they're new in
 		// Go 1.8, and they also require re-sending the request body.
@@ -449,7 +451,7 @@ func redirectBehavior(reqMethod string, resp *Response, ireq *Request) (redirect
 			shouldRedirect = false
 		}
 	}
-	return redirectMethod, shouldRedirect
+	return redirectMethod, shouldRedirect, includeBody
 }
 
 // Do sends an HTTP request and returns an HTTP response, following
@@ -496,7 +498,10 @@ func (c *Client) Do(req *Request) (*Response, error) {
 		reqs        []*Request
 		resp        *Response
 		copyHeaders = c.makeHeadersCopier(req)
+
+		// Redirect behavior:
 		redirectMethod string
+		includeBody    bool
 	)
 	uerr := func(err error) error {
 		req.closeBody()
@@ -534,7 +539,7 @@ func (c *Client) Do(req *Request) (*Response, error) {
 				Cancel:   ireq.Cancel,
 				ctx:      ireq.ctx,
 			}
-			if ireq.GetBody != nil {
+			if includeBody && ireq.GetBody != nil {
 				req.Body, err = ireq.GetBody()
 				if err != nil {
 					return nil, uerr(err)
@@ -598,7 +603,7 @@ func (c *Client) Do(req *Request) (*Response, error) {
 		}
 
 		var shouldRedirect bool
-		redirectMethod, shouldRedirect = redirectBehavior(req.Method, resp, reqs[0])
+		redirectMethod, shouldRedirect, includeBody = redirectBehavior(req.Method, resp, reqs[0])
 		if !shouldRedirect {
 			return resp, nil
 		}

src/net/http/client_test.go

@@ -360,25 +360,25 @@ func TestPostRedirects(t *testing.T) {
 	wantSegments := []string{
 		`POST / "first"`,
 		`POST /?code=301&next=302 "c301"`,
-		`GET /?code=302 "c301"`,
-		`GET / "c301"`,
+		`GET /?code=302 ""`,
+		`GET / ""`,
 		`POST /?code=302&next=302 "c302"`,
-		`GET /?code=302 "c302"`,
-		`GET / "c302"`,
+		`GET /?code=302 ""`,
+		`GET / ""`,
 		`POST /?code=303&next=301 "c303wc301"`,
-		`GET /?code=301 "c303wc301"`,
-		`GET / "c303wc301"`,
+		`GET /?code=301 ""`,
+		`GET / ""`,
 		`POST /?code=304 "c304"`,
 		`POST /?code=305 "c305"`,
 		`POST /?code=307&next=303,308,302 "c307"`,
 		`POST /?code=303&next=308,302 "c307"`,
-		`GET /?code=308&next=302 "c307"`,
+		`GET /?code=308&next=302 ""`,
 		`GET /?code=302 "c307"`,
-		`GET / "c307"`,
+		`GET / ""`,
 		`POST /?code=308&next=302,301 "c308"`,
 		`POST /?code=302&next=301 "c308"`,
-		`GET /?code=301 "c308"`,
-		`GET / "c308"`,
+		`GET /?code=301 ""`,
+		`GET / ""`,
 		`POST /?code=404 "c404"`,
 	}
 	want := strings.Join(wantSegments, "\n")
@@ -399,20 +399,20 @@ func TestDeleteRedirects(t *testing.T) {
 	wantSegments := []string{
 		`DELETE / "first"`,
 		`DELETE /?code=301&next=302,308 "c301"`,
-		`GET /?code=302&next=308 "c301"`,
-		`GET /?code=308 "c301"`,
+		`GET /?code=302&next=308 ""`,
+		`GET /?code=308 ""`,
 		`GET / "c301"`,
 		`DELETE /?code=302&next=302 "c302"`,
-		`GET /?code=302 "c302"`,
-		`GET / "c302"`,
+		`GET /?code=302 ""`,
+		`GET / ""`,
 		`DELETE /?code=303 "c303"`,
-		`GET / "c303"`,
+		`GET / ""`,
 		`DELETE /?code=307&next=301,308,303,302,304 "c307"`,
 		`DELETE /?code=301&next=308,303,302,304 "c307"`,
-		`GET /?code=308&next=303,302,304 "c307"`,
+		`GET /?code=308&next=303,302,304 ""`,
 		`GET /?code=303&next=302,304 "c307"`,
-		`GET /?code=302&next=304 "c307"`,
-		`GET /?code=304 "c307"`,
+		`GET /?code=302&next=304 ""`,
+		`GET /?code=304 ""`,
 		`DELETE /?code=308&next=307 "c308"`,
 		`DELETE /?code=307 "c308"`,
 		`DELETE / "c308"`,
@@ -432,7 +432,11 @@ func testRedirectsByMethod(t *testing.T, method string, table []redirectTest, wa
 	ts = httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		log.Lock()
 		slurp, _ := ioutil.ReadAll(r.Body)
-		fmt.Fprintf(&log.Buffer, "%s %s %q\n", r.Method, r.RequestURI, slurp)
+		fmt.Fprintf(&log.Buffer, "%s %s %q", r.Method, r.RequestURI, slurp)
+		if cl := r.Header.Get("Content-Length"); r.Method == "GET" && len(slurp) == 0 && (r.ContentLength != 0 || cl != "") {
+			fmt.Fprintf(&log.Buffer, " (but with body=%T, content-length = %v, %q)", r.Body, r.ContentLength, cl)
+		}
+		log.WriteByte('\n')
 		log.Unlock()
 		urlQuery := r.URL.Query()
 		if v := urlQuery.Get("code"); v != "" {
@@ -475,7 +479,24 @@ func testRedirectsByMethod(t *testing.T, method string, table []redirectTest, wa
 	want = strings.TrimSpace(want)
 
 	if got != want {
-		t.Errorf("Log differs.\n Got:\n%s\nWant:\n%s\n", got, want)
+		got, want, lines := removeCommonLines(got, want)
+		t.Errorf("Log differs after %d common lines.\n\nGot:\n%s\n\nWant:\n%s\n", lines, got, want)
+	}
+}
+
+func removeCommonLines(a, b string) (asuffix, bsuffix string, commonLines int) {
+	for {
+		nl := strings.IndexByte(a, '\n')
+		if nl < 0 {
+			return a, b, commonLines
+		}
+		line := a[:nl+1]
+		if !strings.HasPrefix(b, line) {
+			return a, b, commonLines
+		}
+		commonLines++
+		a = a[len(line):]
+		b = b[len(line):]
 	}
 }