net/http: support multiple identical Content-Length headers

Referencing RFC 7230 Section 3.3.2, this CL
deduplicates multiple identical Content-Length headers
of a message or rejects the message as invalid if the
Content-Length values differ.

Fixes #16490

Change-Id: Ia6b0f58ec7d35710b11a36113d2bd9128f693f64
Reviewed-on: https://go-review.googlesource.com/31252Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/net/http/request_test.go

@@ -365,18 +365,68 @@ func TestFormFileOrder(t *testing.T) {
 
 var readRequestErrorTests = []struct {
 	in  string
-	err error
+	err string
+
+	header Header
 }{
-	{"GET / HTTP/1.1\r\nheader:foo\r\n\r\n", nil},
-	{"GET / HTTP/1.1\r\nheader:foo\r\n", io.ErrUnexpectedEOF},
-	{"", io.EOF},
+	0: {"GET / HTTP/1.1\r\nheader:foo\r\n\r\n", "", Header{"Header": {"foo"}}},
+	1: {"GET / HTTP/1.1\r\nheader:foo\r\n", io.ErrUnexpectedEOF.Error(), nil},
+	2: {"", io.EOF.Error(), nil},
+	3: {
+		in:  "HEAD / HTTP/1.1\r\nContent-Length:4\r\n\r\n",
+		err: "http: method cannot contain a Content-Length",
+	},
+	4: {
+		in:     "HEAD / HTTP/1.1\r\n\r\n",
+		header: Header{},
+	},
+
+	// Multiple Content-Length values should either be
+	// deduplicated if same or reject otherwise
+	// See Issue 16490.
+	5: {
+		in:  "POST / HTTP/1.1\r\nContent-Length: 10\r\nContent-Length: 0\r\n\r\nGopher hey\r\n",
+		err: "cannot contain multiple Content-Length headers",
+	},
+	6: {
+		in:  "POST / HTTP/1.1\r\nContent-Length: 10\r\nContent-Length: 6\r\n\r\nGopher\r\n",
+		err: "cannot contain multiple Content-Length headers",
+	},
+	7: {
+		in:     "PUT / HTTP/1.1\r\nContent-Length: 6 \r\nContent-Length: 6\r\nContent-Length:6\r\n\r\nGopher\r\n",
+		err:    "",
+		header: Header{"Content-Length": {"6"}},
+	},
+	8: {
+		in:  "PUT / HTTP/1.1\r\nContent-Length: 1\r\nContent-Length: 6 \r\n\r\n",
+		err: "cannot contain multiple Content-Length headers",
+	},
+	9: {
+		in:  "POST / HTTP/1.1\r\nContent-Length:\r\nContent-Length: 3\r\n\r\n",
+		err: "cannot contain multiple Content-Length headers",
+	},
+	10: {
+		in:     "HEAD / HTTP/1.1\r\nContent-Length:0\r\nContent-Length: 0\r\n\r\n",
+		header: Header{"Content-Length": {"0"}},
+	},
 }
 
 func TestReadRequestErrors(t *testing.T) {
 	for i, tt := range readRequestErrorTests {
-		_, err := ReadRequest(bufio.NewReader(strings.NewReader(tt.in)))
-		if err != tt.err {
-			t.Errorf("%d. got error = %v; want %v", i, err, tt.err)
+		req, err := ReadRequest(bufio.NewReader(strings.NewReader(tt.in)))
+		if err == nil {
+			if tt.err != "" {
+				t.Errorf("#%d: got nil err; want %q", i, tt.err)
+			}
+
+			if !reflect.DeepEqual(tt.header, req.Header) {
+				t.Errorf("#%d: gotHeader: %q wantHeader: %q", i, req.Header, tt.header)
+			}
+			continue
+		}
+
+		if tt.err == "" || !strings.Contains(err.Error(), tt.err) {
+			t.Errorf("%d: got error = %v; want %v", i, err, tt.err)
 		}
 	}
 }

src/net/http/response_test.go

@@ -792,6 +792,7 @@ func TestReadResponseErrors(t *testing.T) {
 	type testCase struct {
 		name    string // optional, defaults to in
 		in      string
+		header  Header
 		wantErr interface{} // nil, err value, or string substring
 	}
 
@@ -817,11 +818,22 @@ func TestReadResponseErrors(t *testing.T) {
 		}
 	}
 
+	contentLength := func(status, body string, wantErr interface{}, header Header) testCase {
+		return testCase{
+			name:    fmt.Sprintf("status %q %q", status, body),
+			in:      fmt.Sprintf("HTTP/1.1 %s\r\n%s", status, body),
+			wantErr: wantErr,
+			header:  header,
+		}
+	}
+
+	errMultiCL := "message cannot contain multiple Content-Length headers"
+
 	tests := []testCase{
-		{"", "", io.ErrUnexpectedEOF},
-		{"", "HTTP/1.1 301 Moved Permanently\r\nFoo: bar", io.ErrUnexpectedEOF},
-		{"", "HTTP/1.1", "malformed HTTP response"},
-		{"", "HTTP/2.0", "malformed HTTP response"},
+		{"", "", nil, io.ErrUnexpectedEOF},
+		{"", "HTTP/1.1 301 Moved Permanently\r\nFoo: bar", nil, io.ErrUnexpectedEOF},
+		{"", "HTTP/1.1", nil, "malformed HTTP response"},
+		{"", "HTTP/2.0", nil, "malformed HTTP response"},
 		status("20X Unknown", true),
 		status("abcd Unknown", true),
 		status("二百/两百 OK", true),
@@ -846,7 +858,21 @@ func TestReadResponseErrors(t *testing.T) {
 		version("HTTP/A.B", true),
 		version("HTTP/1", true),
 		version("http/1.1", true),
+
+		contentLength("200 OK", "Content-Length: 10\r\nContent-Length: 7\r\n\r\nGopher hey\r\n", errMultiCL, nil),
+		contentLength("200 OK", "Content-Length: 7\r\nContent-Length: 7\r\n\r\nGophers\r\n", nil, Header{"Content-Length": {"7"}}),
+		contentLength("201 OK", "Content-Length: 0\r\nContent-Length: 7\r\n\r\nGophers\r\n", errMultiCL, nil),
+		contentLength("300 OK", "Content-Length: 0\r\nContent-Length: 0 \r\n\r\nGophers\r\n", nil, Header{"Content-Length": {"0"}}),
+		contentLength("200 OK", "Content-Length:\r\nContent-Length:\r\n\r\nGophers\r\n", nil, nil),
+		contentLength("206 OK", "Content-Length:\r\nContent-Length: 0 \r\nConnection: close\r\n\r\nGophers\r\n", errMultiCL, nil),
+
+		// multiple content-length headers for 204 and 304 should still be checked
+		contentLength("204 OK", "Content-Length: 7\r\nContent-Length: 8\r\n\r\n", errMultiCL, nil),
+		contentLength("204 OK", "Content-Length: 3\r\nContent-Length: 3\r\n\r\n", nil, nil),
+		contentLength("304 OK", "Content-Length: 880\r\nContent-Length: 1\r\n\r\n", errMultiCL, nil),
+		contentLength("304 OK", "Content-Length: 961\r\nContent-Length: 961\r\n\r\n", nil, nil),
 	}
+
 	for i, tt := range tests {
 		br := bufio.NewReader(strings.NewReader(tt.in))
 		_, rerr := ReadResponse(br, nil)

src/net/http/transfer.go

@@ -473,8 +473,29 @@ func (t *transferReader) fixTransferEncoding() error {
 // function is not a method, because ultimately it should be shared by
 // ReadResponse and ReadRequest.
 func fixLength(isResponse bool, status int, requestMethod string, header Header, te []string) (int64, error) {
-	contentLens := header["Content-Length"]
 	isRequest := !isResponse
+	contentLens := header["Content-Length"]
+
+	// Hardening against HTTP request smuggling
+	if len(contentLens) > 1 {
+		// Per RFC 7230 Section 3.3.2, prevent multiple
+		// Content-Length headers if they differ in value.
+		// If there are dups of the value, remove the dups.
+		// See Issue 16490.
+		first := strings.TrimSpace(contentLens[0])
+		for _, ct := range contentLens[1:] {
+			if first != strings.TrimSpace(ct) {
+				return 0, fmt.Errorf("http: message cannot contain multiple Content-Length headers; got %q", contentLens)
+			}
+		}
+
+		// deduplicate Content-Length
+		header.Del("Content-Length")
+		header.Add("Content-Length", first)
+
+		contentLens = header["Content-Length"]
+	}
+
 	// Logic based on response type or status
 	if noBodyExpected(requestMethod) {
 		// For HTTP requests, as part of hardening against request
@@ -494,11 +515,6 @@ func fixLength(isResponse bool, status int, requestMethod string, header Header,
 		return 0, nil
 	}
 
-	if len(contentLens) > 1 {
-		// harden against HTTP request smuggling. See RFC 7230.
-		return 0, errors.New("http: message cannot contain multiple Content-Length headers")
-	}
-
 	// Logic based on Transfer-Encoding
 	if chunked(te) {
 		return -1, nil
@@ -519,7 +535,7 @@ func fixLength(isResponse bool, status int, requestMethod string, header Header,
 		header.Del("Content-Length")
 	}
 
-	if !isResponse {
+	if isRequest {
 		// RFC 2616 neither explicitly permits nor forbids an
 		// entity-body on a GET request so we permit one if
 		// declared, but we default to 0 here (not -1 below)