--- /dev/null
+From 265b691ac440bfb711d8de323346f7d72e620efe Mon Sep 17 00:00:00 2001
+From: Filippo Valsorda <filippo@golang.org>
+Date: Thu, 12 Sep 2019 12:37:36 -0400
+Subject: [PATCH] [release-branch.go1.12-security] net/textproto: don't
+ normalize headers with spaces before the colon
+
+RFC 7230 is clear about headers with a space before the colon, like
+
+X-Answer : 42
+
+being invalid, but we've been accepting and normalizing them for compatibility
+purposes since CL 5690059 in 2012.
+
+On the client side, this is harmless and indeed most browsers behave the same
+to this day. On the server side, this becomes a security issue when the
+behavior doesn't match that of a reverse proxy sitting in front of the server.
+
+For example, if a WAF accepts them without normalizing them, it might be
+possible to bypass its filters, because the Go server would interpret the
+header differently. Worse, if the reverse proxy coalesces requests onto a
+single HTTP/1.1 connection to a Go server, the understanding of the request
+boundaries can get out of sync between them, allowing an attacker to tack an
+arbitrary method and path onto a request by other clients, including
+authentication headers unknown to the attacker.
+
+This was recently presented at multiple security conferences:
+https://portswigger.net/blog/http-desync-attacks-request-smuggling-reborn
+
+net/http servers already reject header keys with invalid characters.
+Simply stop normalizing extra spaces in net/textproto, let it return them
+unchanged like it does for other invalid headers, and let net/http enforce
+RFC 7230, which is HTTP specific. This loses us normalization on the client
+side, but there's no right answer on the client side anyway, and hiding the
+issue sounds worse than letting the application decide.
+
+Fixes CVE-2019-16276
+
+Change-Id: I6d272de827e0870da85d93df770d6a0e161bbcf1
+Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/549719
+Reviewed-by: Brad Fitzpatrick <bradfitz@google.com>
+(cherry picked from commit 1280b868e82bf173ea3e988be3092d160ee66082)
+Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/558776
+Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
+
+CVE: CVE-2019-16276
+
+Upstream-Status: Backport [https://github.com/golang/go/commit/6e6f4aaf70c8b1cc81e65a26332aa9409de03ad8]
+
+Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
+---
+ src/net/http/serve_test.go | 4 ++++
+ src/net/http/transport_test.go | 27 +++++++++++++++++++++++++++
+ src/net/textproto/reader.go | 10 ++--------
+ src/net/textproto/reader_test.go | 13 ++++++-------
+ 4 files changed, 39 insertions(+), 15 deletions(-)
+
+diff --git a/src/net/http/serve_test.go b/src/net/http/serve_test.go
+index 6eb0088a96..89bfdfbb82 100644
+--- a/src/net/http/serve_test.go
++++ b/src/net/http/serve_test.go
+@@ -4748,6 +4748,10 @@ func TestServerValidatesHeaders(t *testing.T) {
+ {"foo\xffbar: foo\r\n", 400}, // binary in header
+ {"foo\x00bar: foo\r\n", 400}, // binary in header
+ {"Foo: " + strings.Repeat("x", 1<<21) + "\r\n", 431}, // header too large
++ // Spaces between the header key and colon are not allowed.
++ // See RFC 7230, Section 3.2.4.
++ {"Foo : bar\r\n", 400},
++ {"Foo\t: bar\r\n", 400},
+
+ {"foo: foo foo\r\n", 200}, // LWS space is okay
+ {"foo: foo\tfoo\r\n", 200}, // LWS tab is okay
+diff --git a/src/net/http/transport_test.go b/src/net/http/transport_test.go
+index 5c329543e2..5e5438a708 100644
+--- a/src/net/http/transport_test.go
++++ b/src/net/http/transport_test.go
+@@ -5133,3 +5133,30 @@ func TestTransportIgnores408(t *testing.T) {
+ }
+ t.Fatalf("timeout after %v waiting for Transport connections to die off", time.Since(t0))
+ }
++
++func TestInvalidHeaderResponse(t *testing.T) {
++ setParallel(t)
++ defer afterTest(t)
++ cst := newClientServerTest(t, h1Mode, HandlerFunc(func(w ResponseWriter, r *Request) {
++ conn, buf, _ := w.(Hijacker).Hijack()
++ buf.Write([]byte("HTTP/1.1 200 OK\r\n" +
++ "Date: Wed, 30 Aug 2017 19:09:27 GMT\r\n" +
++ "Content-Type: text/html; charset=utf-8\r\n" +
++ "Content-Length: 0\r\n" +
++ "Foo : bar\r\n\r\n"))
++ buf.Flush()
++ conn.Close()
++ }))
++ defer cst.close()
++ res, err := cst.c.Get(cst.ts.URL)
++ if err != nil {
++ t.Fatal(err)
++ }
++ defer res.Body.Close()
++ if v := res.Header.Get("Foo"); v != "" {
++ t.Errorf(`unexpected "Foo" header: %q`, v)
++ }
++ if v := res.Header.Get("Foo "); v != "bar" {
++ t.Errorf(`bad "Foo " header value: %q, want %q`, v, "bar")
++ }
++}
+diff --git a/src/net/textproto/reader.go b/src/net/textproto/reader.go
+index 2c4f25d5ae..1a5e364cf7 100644
+--- a/src/net/textproto/reader.go
++++ b/src/net/textproto/reader.go
+@@ -493,18 +493,12 @@ func (r *Reader) ReadMIMEHeader() (MIMEHeader, error) {
+ return m, err
+ }
+
+- // Key ends at first colon; should not have trailing spaces
+- // but they appear in the wild, violating specs, so we remove
+- // them if present.
++ // Key ends at first colon.
+ i := bytes.IndexByte(kv, ':')
+ if i < 0 {
+ return m, ProtocolError("malformed MIME header line: " + string(kv))
+ }
+- endKey := i
+- for endKey > 0 && kv[endKey-1] == ' ' {
+- endKey--
+- }
+- key := canonicalMIMEHeaderKey(kv[:endKey])
++ key := canonicalMIMEHeaderKey(kv[:i])
+
+ // As per RFC 7230 field-name is a token, tokens consist of one or more chars.
+ // We could return a ProtocolError here, but better to be liberal in what we
+diff --git a/src/net/textproto/reader_test.go b/src/net/textproto/reader_test.go
+index f85fbdc36d..b92fdcd3c7 100644
+--- a/src/net/textproto/reader_test.go
++++ b/src/net/textproto/reader_test.go
+@@ -188,11 +188,10 @@ func TestLargeReadMIMEHeader(t *testing.T) {
+ }
+ }
+
+-// Test that we read slightly-bogus MIME headers seen in the wild,
+-// with spaces before colons, and spaces in keys.
++// TestReadMIMEHeaderNonCompliant checks that we don't normalize headers
++// with spaces before colons, and accept spaces in keys.
+ func TestReadMIMEHeaderNonCompliant(t *testing.T) {
+- // Invalid HTTP response header as sent by an Axis security
+- // camera: (this is handled by IE, Firefox, Chrome, curl, etc.)
++ // These invalid headers will be rejected by net/http according to RFC 7230.
+ r := reader("Foo: bar\r\n" +
+ "Content-Language: en\r\n" +
+ "SID : 0\r\n" +
+@@ -202,9 +201,9 @@ func TestReadMIMEHeaderNonCompliant(t *testing.T) {
+ want := MIMEHeader{
+ "Foo": {"bar"},
+ "Content-Language": {"en"},
+- "Sid": {"0"},
+- "Audio Mode": {"None"},
+- "Privilege": {"127"},
++ "SID ": {"0"},
++ "Audio Mode ": {"None"},
++ "Privilege ": {"127"},
+ }
+ if !reflect.DeepEqual(m, want) || err != nil {
+ t.Fatalf("ReadMIMEHeader =\n%v, %v; want:\n%v", m, err, want)
