net/http: update bundled golang.org/x/net/http2 to import security fix

Update golang.org/x/net to v0.0.0-20190813141303-74dc4d7220e7 to import
the following security fix.

    commit 74dc4d7220e7acc4e100824340f3e66577424772
    Author: Filippo Valsorda <filippo@golang.org>
    Date:   Sun Aug 11 02:12:18 2019 -0400

    http2: limit number of control frames in server send queue

    An attacker could cause servers to queue an unlimited number of PING
    ACKs or RST_STREAM frames by soliciting them and not reading them, until
    the program runs out of memory.

    Limit control frames in the queue to a few thousands (matching the limit
    imposed by other vendors) by counting as they enter and exit the scheduler,
    so the protection will work with any WriteScheduler.

    Once the limit is exceeded, close the connection, as we have no way to
    communicate with the peer.

    Change-Id: I842968fc6ed3eac654b497ade8cea86f7267886b
    Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/525552
    Reviewed-by: Brad Fitzpatrick <bradfitz@google.com>

This change was generated with cmd/go and cmd/bundle:

$ go get -u golang.org/x/net
$ go mod tidy
$ go mod vendor
$ go generate net/http

Fixes CVE-2019-9512 and CVE-2019-9514
Fixes #33606

Change-Id: I464baf96175006aa101d65d3b0f6494f28a626ab
Reviewed-on: https://go-review.googlesource.com/c/go/+/190137
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

src/go.mod

@@ -4,7 +4,7 @@ go 1.12
 
 require (
 	golang.org/x/crypto v0.0.0-20190611184440-5c40567a22f8
-	golang.org/x/net v0.0.0-20190607181551-461777fb6f67
+	golang.org/x/net v0.0.0-20190813141303-74dc4d7220e7
 	golang.org/x/sys v0.0.0-20190529130038-5219a1e1c5f8 // indirect
 	golang.org/x/text v0.3.2 // indirect
 )

src/go.sum

@@ -2,8 +2,8 @@ golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACk
 golang.org/x/crypto v0.0.0-20190611184440-5c40567a22f8 h1:1wopBVtVdWnn03fZelqdXTqk7U7zPQCb+T4rbU9ZEoU=
 golang.org/x/crypto v0.0.0-20190611184440-5c40567a22f8/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/net v0.0.0-20190607181551-461777fb6f67 h1:rJJxsykSlULwd2P2+pg/rtnwN2FrWp4IuCxOSyS0V00=
-golang.org/x/net v0.0.0-20190607181551-461777fb6f67/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20190813141303-74dc4d7220e7 h1:fHDIZ2oxGnUZRN6WgWFCbYBjH9uqVPRCUVUDhs0wnbA=
+golang.org/x/net v0.0.0-20190813141303-74dc4d7220e7/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190529130038-5219a1e1c5f8 h1:2WjIC11WRITGlVWmyLXKjzIVj1ZwoWZ//tadeUUV6/o=

src/net/http/h2_bundle.go

@@ -3611,10 +3611,11 @@ func (p *http2pipe) Done() <-chan struct{} {
 }
 
 const (
-	http2prefaceTimeout        = 10 * time.Second
-	http2firstSettingsTimeout  = 2 * time.Second // should be in-flight with preface anyway
-	http2handlerChunkWriteSize = 4 << 10
-	http2defaultMaxStreams     = 250 // TODO: make this 100 as the GFE seems to?
+	http2prefaceTimeout         = 10 * time.Second
+	http2firstSettingsTimeout   = 2 * time.Second // should be in-flight with preface anyway
+	http2handlerChunkWriteSize  = 4 << 10
+	http2defaultMaxStreams      = 250 // TODO: make this 100 as the GFE seems to?
+	http2maxQueuedControlFrames = 10000
 )
 
 var (
@@ -3722,6 +3723,15 @@ func (s *http2Server) maxConcurrentStreams() uint32 {
 	return http2defaultMaxStreams
 }
 
+// maxQueuedControlFrames is the maximum number of control frames like
+// SETTINGS, PING and RST_STREAM that will be queued for writing before
+// the connection is closed to prevent memory exhaustion attacks.
+func (s *http2Server) maxQueuedControlFrames() int {
+	// TODO: if anybody asks, add a Server field, and remember to define the
+	// behavior of negative values.
+	return http2maxQueuedControlFrames
+}
+
 type http2serverInternalState struct {
 	mu          sync.Mutex
 	activeConns map[*http2serverConn]struct{}
@@ -4065,6 +4075,7 @@ type http2serverConn struct {
 	sawFirstSettings            bool // got the initial SETTINGS frame after the preface
 	needToSendSettingsAck       bool
 	unackedSettings             int    // how many SETTINGS have we sent without ACKs?
+	queuedControlFrames         int    // control frames in the writeSched queue
 	clientMaxStreams            uint32 // SETTINGS_MAX_CONCURRENT_STREAMS from client (our PUSH_PROMISE limit)
 	advMaxStreams               uint32 // our SETTINGS_MAX_CONCURRENT_STREAMS advertised the client
 	curClientStreams            uint32 // number of open streams initiated by the client
@@ -4456,6 +4467,14 @@ func (sc *http2serverConn) serve() {
 			}
 		}
 
+		// If the peer is causing us to generate a lot of control frames,
+		// but not reading them from us, assume they are trying to make us
+		// run out of memory.
+		if sc.queuedControlFrames > sc.srv.maxQueuedControlFrames() {
+			sc.vlogf("http2: too many control frames in send queue, closing connection")
+			return
+		}
+
 		// Start the shutdown timer after sending a GOAWAY. When sending GOAWAY
 		// with no error code (graceful shutdown), don't start the timer until
 		// all open streams have been completed.
@@ -4657,6 +4676,14 @@ func (sc *http2serverConn) writeFrame(wr http2FrameWriteRequest) {
 	}
 
 	if !ignoreWrite {
+		if wr.isControl() {
+			sc.queuedControlFrames++
+			// For extra safety, detect wraparounds, which should not happen,
+			// and pull the plug.
+			if sc.queuedControlFrames < 0 {
+				sc.conn.Close()
+			}
+		}
 		sc.writeSched.Push(wr)
 	}
 	sc.scheduleFrameWrite()
@@ -4774,10 +4801,8 @@ func (sc *http2serverConn) wroteFrame(res http2frameWriteResult) {
 // If a frame is already being written, nothing happens. This will be called again
 // when the frame is done being written.
 //
-// If a frame isn't being written we need to send one, the best frame
-// to send is selected, preferring first things that aren't
-// stream-specific (e.g. ACKing settings), and then finding the
-// highest priority stream.
+// If a frame isn't being written and we need to send one, the best frame
+// to send is selected by writeSched.
 //
 // If a frame isn't being written and there's nothing else to send, we
 // flush the write buffer.
@@ -4805,6 +4830,9 @@ func (sc *http2serverConn) scheduleFrameWrite() {
 		}
 		if !sc.inGoAway || sc.goAwayCode == http2ErrCodeNo {
 			if wr, ok := sc.writeSched.Pop(); ok {
+				if wr.isControl() {
+					sc.queuedControlFrames--
+				}
 				sc.startFrameWrite(wr)
 				continue
 			}
@@ -5097,6 +5125,8 @@ func (sc *http2serverConn) processSettings(f *http2SettingsFrame) error {
 	if err := f.ForeachSetting(sc.processSetting); err != nil {
 		return err
 	}
+	// TODO: judging by RFC 7540, Section 6.5.3 each SETTINGS frame should be
+	// acknowledged individually, even if multiple are received before the ACK.
 	sc.needToSendSettingsAck = true
 	sc.scheduleFrameWrite()
 	return nil
@@ -7451,7 +7481,7 @@ func (cc *http2ClientConn) roundTrip(req *Request) (res *Response, gotErrAfterRe
 		req.Method != "HEAD" {
 		// Request gzip only, not deflate. Deflate is ambiguous and
 		// not as universally supported anyway.
-		// See: http://www.gzip.org/zlib/zlib_faq.html#faq38
+		// See: https://zlib.net/zlib_faq.html#faq39
 		//
 		// Note that we don't request this for HEAD requests,
 		// due to a bug in nginx:
@@ -9445,7 +9475,7 @@ type http2WriteScheduler interface {
 
 	// Pop dequeues the next frame to write. Returns false if no frames can
 	// be written. Frames with a given wr.StreamID() are Pop'd in the same
-	// order they are Push'd.
+	// order they are Push'd. No frames should be discarded except by CloseStream.
 	Pop() (wr http2FrameWriteRequest, ok bool)
 }
 
@@ -9489,6 +9519,12 @@ func (wr http2FrameWriteRequest) StreamID() uint32 {
 	return wr.stream.id
 }
 
+// isControl reports whether wr is a control frame for MaxQueuedControlFrames
+// purposes. That includes non-stream frames and RST_STREAM frames.
+func (wr http2FrameWriteRequest) isControl() bool {
+	return wr.stream == nil
+}
+
 // DataSize returns the number of flow control bytes that must be consumed
 // to write this entire frame. This is 0 for non-DATA frames.
 func (wr http2FrameWriteRequest) DataSize() int {

src/vendor/golang.org/x/net/lif/zsys_solaris_amd64.go

@@ -1,4 +1,4 @@
-// Created by cgo -godefs - DO NOT EDIT
+// Code generated by cmd/cgo -godefs; DO NOT EDIT.
 // cgo -godefs defs_solaris.go
 
 package lif

src/vendor/golang.org/x/net/route/zsys_darwin.go

@@ -1,4 +1,4 @@
-// Created by cgo -godefs - DO NOT EDIT
+// Code generated by cmd/cgo -godefs; DO NOT EDIT.
 // cgo -godefs defs_darwin.go
 
 package route

src/vendor/golang.org/x/net/route/zsys_dragonfly.go

@@ -1,4 +1,4 @@
-// Created by cgo -godefs - DO NOT EDIT
+// Code generated by cmd/cgo -godefs; DO NOT EDIT.
 // cgo -godefs defs_dragonfly.go
 
 package route

src/vendor/golang.org/x/net/route/zsys_freebsd_386.go

@@ -1,4 +1,4 @@
-// Created by cgo -godefs - DO NOT EDIT
+// Code generated by cmd/cgo -godefs; DO NOT EDIT.
 // cgo -godefs defs_freebsd.go
 
 package route

src/vendor/golang.org/x/net/route/zsys_freebsd_amd64.go

@@ -1,4 +1,4 @@
-// Created by cgo -godefs - DO NOT EDIT
+// Code generated by cmd/cgo -godefs; DO NOT EDIT.
 // cgo -godefs defs_freebsd.go
 
 package route

src/vendor/golang.org/x/net/route/zsys_freebsd_arm.go

@@ -1,4 +1,4 @@
-// Created by cgo -godefs - DO NOT EDIT
+// Code generated by cmd/cgo -godefs; DO NOT EDIT.
 // cgo -godefs defs_freebsd.go
 
 package route

src/vendor/golang.org/x/net/route/zsys_netbsd.go

@@ -1,4 +1,4 @@
-// Created by cgo -godefs - DO NOT EDIT
+// Code generated by cmd/cgo -godefs; DO NOT EDIT.
 // cgo -godefs defs_netbsd.go
 
 package route

src/vendor/golang.org/x/net/route/zsys_openbsd.go

@@ -1,4 +1,4 @@
-// Created by cgo -godefs - DO NOT EDIT
+// Code generated by cmd/cgo -godefs; DO NOT EDIT.
 // cgo -godefs defs_openbsd.go
 
 package route

src/vendor/modules.txt

@@ -7,7 +7,7 @@ golang.org/x/crypto/hkdf
 golang.org/x/crypto/internal/chacha20
 golang.org/x/crypto/internal/subtle
 golang.org/x/crypto/poly1305
-# golang.org/x/net v0.0.0-20190607181551-461777fb6f67
+# golang.org/x/net v0.0.0-20190813141303-74dc4d7220e7
 golang.org/x/net/dns/dnsmessage
 golang.org/x/net/http/httpguts
 golang.org/x/net/http/httpproxy