net/http: don't write redirect body if content-type is set

Fixes #25166

Change-Id: Id1fe18899579365519ac08ebedf74cd23c0fbd9f
Reviewed-on: https://go-review.googlesource.com/110296
Run-TryBot: Sam Whited <sam@samwhited.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/net/http/serve_test.go b/src/net/http/serve_test.go
index 529629f72243d2d1361d033da4f3927fcef43a93..4be94a67094910d4396ff1a2732beb9a5df6c5d8 100644 (file)
--- a/src/net/http/serve_test.go
+++ b/src/net/http/serve_test.go
@@ -2589,20 +2589,29 @@ func TestRedirect(t *testing.T) {
 
 // Test that Content-Type header is set for GET and HEAD requests.
 func TestRedirectContentTypeAndBody(t *testing.T) {
+       var unsetCT = []string{"sentinalValNoCT"}
+
        var tests = []struct {
+               initCT   []string
                method   string
                wantCT   string
                wantBody string
        }{
-               {MethodGet, "text/html; charset=utf-8", "<a href=\"/foo\">Found</a>.\n\n"},
-               {MethodHead, "text/html; charset=utf-8", ""},
-               {MethodPost, "", ""},
-               {MethodDelete, "", ""},
-               {"foo", "", ""},
+               {unsetCT, MethodGet, "text/html; charset=utf-8", "<a href=\"/foo\">Found</a>.\n\n"},
+               {unsetCT, MethodHead, "text/html; charset=utf-8", ""},
+               {unsetCT, MethodPost, "", ""},
+               {unsetCT, MethodDelete, "", ""},
+               {unsetCT, "foo", "", ""},
+               {[]string{"application/test"}, MethodGet, "application/test", ""},
+               {[]string{}, MethodGet, "", ""},
+               {nil, MethodGet, "", ""},
        }
        for _, tt := range tests {
                req := httptest.NewRequest(tt.method, "http://example.com/qux/", nil)
                rec := httptest.NewRecorder()
+               if len(tt.initCT) != 1 || &tt.initCT[0] != &unsetCT[0] {
+                       rec.Header()["Content-Type"] = tt.initCT
+               }
                Redirect(rec, req, "/foo", 302)
                if got, want := rec.Header().Get("Content-Type"), tt.wantCT; got != want {
                        t.Errorf("Redirect(%q) generated Content-Type header %q; want %q", tt.method, got, want)

diff --git a/src/net/http/server.go b/src/net/http/server.go
index 1cc4ba6adb49bd0a1754219f54eb806145eea57f..fca46d34809029cab7999cb49f83887b5b0afa9f 100644 (file)
--- a/src/net/http/server.go
+++ b/src/net/http/server.go
@@ -2003,6 +2003,9 @@ func StripPrefix(prefix string, h Handler) Handler {
 //
 // The provided code should be in the 3xx range and is usually
 // StatusMovedPermanently, StatusFound or StatusSeeOther.
+// If Content-Type has not been set Redirect sets the header to
+// "text/html; charset=utf-8" and writes a small HTML body.
+// Setting the Content-Type header to nil also prevents writing the body.
 func Redirect(w ResponseWriter, r *Request, url string, code int) {
        // parseURL is just url.Parse (url is shadowed for godoc).
        if u, err := parseURL(url); err == nil {
@@ -2039,9 +2042,14 @@ func Redirect(w ResponseWriter, r *Request, url string, code int) {
                }
        }
 
-       w.Header().Set("Location", hexEscapeNonASCII(url))
+       h := w.Header()
+       h.Set("Location", hexEscapeNonASCII(url))
+
+       if _, ok := h["Content-Type"]; ok {
+               return
+       }
        if r.Method == "GET" || r.Method == "HEAD" {
-               w.Header().Set("Content-Type", "text/html; charset=utf-8")
+               h.Set("Content-Type", "text/html; charset=utf-8")
        }
        w.WriteHeader(code)