CVE-2015-5741 (Go, published 2020-02-08T19:15Z)
Description: value: The net/http library in net/http/transfer.go in Go before 1.4.3 does not properly parse HTTP headers, which allows remote attackers to conduct HTTP request smuggling attacks via a request that contains Content-Length and Transfer-Encoding header fields.
Severity: HIGH (CVSS v3 base score: 9.8)
Weakness: CWE-444 \u2014 Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
The product acts as an intermediary HTTP agent
         (such as a proxy or firewall) in the data flow between two
         entities such as a client and server, but it does not
         interpret malformed HTTP requests or responses in ways that
         are consistent with how the messages will be processed by
         those entities that are at the ultimate destination.
Repository: https://github.com/golang/go
Files changed:
src/net/http/readrequest_test.go
src/net/http/transfer.go
Commit message: net/http: harden Server against request smuggling

See RFC 7230.

Thanks to Régis Leroy for the report.

Change-Id: Ic1779bc2180900430d4d7a4938cac04ed73c304c
Reviewed-on: https://go-review.googlesource.com/11810
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>


Vulnerable code:
func TestReadRequest_BadConnectHost(t *testing.T) {
	data := []byte("CONNECT []%20%48%54%54%50%2f%31%2e%31%0a%4d%79%48%65%61%64%65%72%3a%20%31%32%33%0a%0a HTTP/1.0\n\n")
	r, err := ReadRequest(bufio.NewReader(bytes.NewReader(data)))
	if err == nil {
		t.Fatal("Got unexpected request = %#v", r)
	t.TransferEncoding, err = fixTransferEncoding(t.RequestMethod, t.Header)
func fixTransferEncoding(requestMethod string, header Header) ([]string, error) {

		// Chunked encoding trumps Content-Length. See RFC 2616
		// Section 4.4. Currently len(te) > 0 implies chunked
		// encoding.
		delete(header, "Content-Length")

	cl := strings.TrimSpace(header.get("Content-Length"))
	if !isResponse && requestMethod == "GET" {
		// RFC 2616 doesn't explicitly permit nor forbid an

Fixed code:
	"io/ioutil"

	// HEAD with Content-Length 0. Make sure this is permitted,
	// since I think we used to send it.
	{
		"HEAD / HTTP/1.1\r\nHost: issue8261.com\r\nConnection: close\r\nContent-Length: 0\r\n\r\n",
		&Request{
			Method: "HEAD",
			URL: &url.URL{
				Path: "/",
			},
			Header: Header{
				"Connection":     []string{"close"},
				"Content-Length": []string{"0"},
			},
			Host:       "issue8261.com",
			Proto:      "HTTP/1.1",
			ProtoMajor: 1,
			ProtoMinor: 1,
			Close:      true,
			RequestURI: "/",
		},

		noBody,
		noTrailer,
		noError,
	},
// reqBytes treats req as a request (with \n delimiters) and returns it with \r\n delimiters,
// ending in \r\n\r\n
func reqBytes(req string) []byte {
	return []byte(strings.Replace(strings.TrimSpace(req), "\n", "\r\n", -1) + "\r\n\r\n")
}

var badRequestTests = []struct {
	name string
	req  []byte
}{
	{"bad_connect_host", reqBytes("CONNECT []%20%48%54%54%50%2f%31%2e%31%0a%4d%79%48%65%61%64%65%72%3a%20%31%32%33%0a%0a HTTP/1.0")},
	{"smuggle_two_contentlen", reqBytes(`POST / HTTP/1.1
Content-Length: 3
Content-Length: 4

abc`)},
	{"smuggle_chunked_and_len", reqBytes(`POST / HTTP/1.1
Transfer-Encoding: chunked
Content-Length: 3

abc`)},
	{"smuggle_content_len_head", reqBytes(`HEAD / HTTP/1.1
Host: foo
Content-Length: 5`)},
}

func TestReadRequest_Bad(t *testing.T) {
	for _, tt := range badRequestTests {
		got, err := ReadRequest(bufio.NewReader(bytes.NewReader(tt.req)))
		if err == nil {
			all, err := ioutil.ReadAll(got.Body)
			t.Errorf("%s: got unexpected request = %#v\n  Body = %q, %v", tt.name, got, all, err)
		}
		if t.Method == "GET" || t.Method == "HEAD" {
			return false
		}
		t.RequestMethod = rr.Method
	t.TransferEncoding, err = fixTransferEncoding(isResponse, t.RequestMethod, t.Header)
func fixTransferEncoding(isResponse bool, requestMethod string, header Header) ([]string, error) {
	isRequest := !isResponse
		// RFC 7230 3.3.2 says "A sender MUST NOT send a
		// Content-Length header field in any message that
		// contains a Transfer-Encoding header field."
		if len(header["Content-Length"]) > 0 {
			if isRequest {
				return nil, errors.New("http: invalid Content-Length with Transfer-Encoding")
			}
			delete(header, "Content-Length")
		}
	contentLens := header["Content-Length"]
	isRequest := !isResponse
		// For HTTP requests, as part of hardening against request
		// smuggling (RFC 7230), don't allow a Content-Length header for
		// methods which don't permit bodies. As an exception, allow
		// exactly one Content-Length header if its value is "0".
		if isRequest && len(contentLens) > 0 && !(len(contentLens) == 1 && contentLens[0] == "0") {
			return 0, fmt.Errorf("http: method cannot contain a Content-Length; got %q", contentLens)
		}
	if len(contentLens) > 1 {
		// harden against HTTP request smuggling. See RFC 7230.
		return 0, errors.New("http: message cannot contain multiple Content-Length headers")
	}

	var cl string
	if len(contentLens) == 1 {
		cl = strings.TrimSpace(contentLens[0])
	}
	if !isResponse {
		// RFC 2616 neither explicitly permits nor forbids an
		// Likewise, all other request methods are assumed to have
		// no body if neither Transfer-Encoding chunked nor a
		// Content-Length are set.