http2: Respect peer's SETTINGS_MAX_HEADER_LIST_SIZE in ClientConn

Add a new peerMaxHeaderListSize member to ClientConn which records the
SETTINGS_MAX_HEADER_LIST_SIZE requested by the client's peer, and
respect this limit in (*ClientConn) encodeHeaders / encodeTrailers.

Attempting to send more than peerMaxHeaderListSize bytes of headers or
trailers will result in RoundTrip returning errRequestHeaderListSize.

Updates golang/go#13959

Change-Id: Ic707179782acdf8ae543429ea1af7f4f30e67e59
Reviewed-on: https://go-review.googlesource.com/29243
Run-TryBot: Tom Bergan <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Tom Bergan <[email protected]>

Author: appleby

http2/transport.go

@@ -87,7 +87,7 @@ type Transport struct {
 
 	// MaxHeaderListSize is the http2 SETTINGS_MAX_HEADER_LIST_SIZE to
 	// send in the initial settings frame. It is how many bytes
-	// of response headers are allow. Unlike the http2 spec, zero here
+	// of response headers are allowed. Unlike the http2 spec, zero here
 	// means to use a default limit (currently 10MB). If you actually
 	// want to advertise an ulimited value to the peer, Transport
 	// interprets the highest possible value here (0xffffffff or 1<<32-1)
@@ -172,9 +172,10 @@ type ClientConn struct {
 	fr              *Framer
 	lastActive      time.Time
 	// Settings from peer: (also guarded by mu)
-	maxFrameSize         uint32
-	maxConcurrentStreams uint32
-	initialWindowSize    uint32
+	maxFrameSize          uint32
+	maxConcurrentStreams  uint32
+	peerMaxHeaderListSize uint64
+	initialWindowSize     uint32
 
 	hbuf    bytes.Buffer // HPACK encoder writes into this
 	henc    *hpack.Encoder
@@ -519,17 +520,18 @@ func (t *Transport) NewClientConn(c net.Conn) (*ClientConn, error) {
 
 func (t *Transport) newClientConn(c net.Conn, singleUse bool) (*ClientConn, error) {
 	cc := &ClientConn{
-		t:                    t,
-		tconn:                c,
-		readerDone:           make(chan struct{}),
-		nextStreamID:         1,
-		maxFrameSize:         16 << 10, // spec default
-		initialWindowSize:    65535,    // spec default
-		maxConcurrentStreams: 1000,     // "infinite", per spec. 1000 seems good enough.
-		streams:              make(map[uint32]*clientStream),
-		singleUse:            singleUse,
-		wantSettingsAck:      true,
-		pings:                make(map[[8]byte]chan struct{}),
+		t:                     t,
+		tconn:                 c,
+		readerDone:            make(chan struct{}),
+		nextStreamID:          1,
+		maxFrameSize:          16 << 10,           // spec default
+		initialWindowSize:     65535,              // spec default
+		maxConcurrentStreams:  1000,               // "infinite", per spec. 1000 seems good enough.
+		peerMaxHeaderListSize: 0xffffffffffffffff, // "infinite", per spec. Use 2^64-1 instead.
+		streams:               make(map[uint32]*clientStream),
+		singleUse:             singleUse,
+		wantSettingsAck:       true,
+		pings:                 make(map[[8]byte]chan struct{}),
 	}
 	if d := t.idleConnTimeout(); d != 0 {
 		cc.idleTimeout = d
@@ -1085,8 +1087,13 @@ func (cs *clientStream) writeRequestBody(body io.Reader, bodyCloser io.Closer) (
 	var trls []byte
 	if hasTrailers {
 		cc.mu.Lock()
-		defer cc.mu.Unlock()
-		trls = cc.encodeTrailers(req)
+		trls, err = cc.encodeTrailers(req)
+		cc.mu.Unlock()
+		if err != nil {
+			cc.writeStreamReset(cs.ID, ErrCodeInternal, err)
+			cc.forgetStreamID(cs.ID)
+			return err
+		}
 	}
 
 	cc.wmu.Lock()
@@ -1189,62 +1196,86 @@ func (cc *ClientConn) encodeHeaders(req *http.Request, addGzipHeader bool, trail
 		}
 	}
 
-	// 8.1.2.3 Request Pseudo-Header Fields
-	// The :path pseudo-header field includes the path and query parts of the
-	// target URI (the path-absolute production and optionally a '?' character
-	// followed by the query production (see Sections 3.3 and 3.4 of
-	// [RFC3986]).
-	cc.writeHeader(":authority", host)
-	cc.writeHeader(":method", req.Method)
-	if req.Method != "CONNECT" {
-		cc.writeHeader(":path", path)
-		cc.writeHeader(":scheme", req.URL.Scheme)
-	}
-	if trailers != "" {
-		cc.writeHeader("trailer", trailers)
-	}
+	enumerateHeaders := func(f func(name, value string)) {
+		// 8.1.2.3 Request Pseudo-Header Fields
+		// The :path pseudo-header field includes the path and query parts of the
+		// target URI (the path-absolute production and optionally a '?' character
+		// followed by the query production (see Sections 3.3 and 3.4 of
+		// [RFC3986]).
+		f(":authority", host)
+		f(":method", req.Method)
+		if req.Method != "CONNECT" {
+			f(":path", path)
+			f(":scheme", req.URL.Scheme)
+		}
+		if trailers != "" {
+			f("trailer", trailers)
+		}
 
-	var didUA bool
-	for k, vv := range req.Header {
-		lowKey := strings.ToLower(k)
-		switch lowKey {
-		case "host", "content-length":
-			// Host is :authority, already sent.
-			// Content-Length is automatic, set below.
-			continue
-		case "connection", "proxy-connection", "transfer-encoding", "upgrade", "keep-alive":
-			// Per 8.1.2.2 Connection-Specific Header
-			// Fields, don't send connection-specific
-			// fields. We have already checked if any
-			// are error-worthy so just ignore the rest.
-			continue
-		case "user-agent":
-			// Match Go's http1 behavior: at most one
-			// User-Agent. If set to nil or empty string,
-			// then omit it. Otherwise if not mentioned,
-			// include the default (below).
-			didUA = true
-			if len(vv) < 1 {
+		var didUA bool
+		for k, vv := range req.Header {
+			if strings.EqualFold(k, "host") || strings.EqualFold(k, "content-length") {
+				// Host is :authority, already sent.
+				// Content-Length is automatic, set below.
 				continue
-			}
-			vv = vv[:1]
-			if vv[0] == "" {
+			} else if strings.EqualFold(k, "connection") || strings.EqualFold(k, "proxy-connection") ||
+				strings.EqualFold(k, "transfer-encoding") || strings.EqualFold(k, "upgrade") ||
+				strings.EqualFold(k, "keep-alive") {
+				// Per 8.1.2.2 Connection-Specific Header
+				// Fields, don't send connection-specific
+				// fields. We have already checked if any
+				// are error-worthy so just ignore the rest.
 				continue
+			} else if strings.EqualFold(k, "user-agent") {
+				// Match Go's http1 behavior: at most one
+				// User-Agent. If set to nil or empty string,
+				// then omit it. Otherwise if not mentioned,
+				// include the default (below).
+				didUA = true
+				if len(vv) < 1 {
+					continue
+				}
+				vv = vv[:1]
+				if vv[0] == "" {
+					continue
+				}
+
+			}
+
+			for _, v := range vv {
+				f(k, v)
 			}
 		}
-		for _, v := range vv {
-			cc.writeHeader(lowKey, v)
+		if shouldSendReqContentLength(req.Method, contentLength) {
+			f("content-length", strconv.FormatInt(contentLength, 10))
+		}
+		if addGzipHeader {
+			f("accept-encoding", "gzip")
+		}
+		if !didUA {
+			f("user-agent", defaultUserAgent)
 		}
 	}
-	if shouldSendReqContentLength(req.Method, contentLength) {
-		cc.writeHeader("content-length", strconv.FormatInt(contentLength, 10))
-	}
-	if addGzipHeader {
-		cc.writeHeader("accept-encoding", "gzip")
-	}
-	if !didUA {
-		cc.writeHeader("user-agent", defaultUserAgent)
+
+	// Do a first pass over the headers counting bytes to ensure
+	// we don't exceed cc.peerMaxHeaderListSize. This is done as a
+	// separate pass before encoding the headers to prevent
+	// modifying the hpack state.
+	hlSize := uint64(0)
+	enumerateHeaders(func(name, value string) {
+		hf := hpack.HeaderField{Name: name, Value: value}
+		hlSize += uint64(hf.Size())
+	})
+
+	if hlSize > cc.peerMaxHeaderListSize {
+		return nil, errRequestHeaderListSize
 	}
+
+	// Header list size is ok. Write the headers.
+	enumerateHeaders(func(name, value string) {
+		cc.writeHeader(strings.ToLower(name), value)
+	})
+
 	return cc.hbuf.Bytes(), nil
 }
 
@@ -1271,17 +1302,29 @@ func shouldSendReqContentLength(method string, contentLength int64) bool {
 }
 
 // requires cc.mu be held.
-func (cc *ClientConn) encodeTrailers(req *http.Request) []byte {
+func (cc *ClientConn) encodeTrailers(req *http.Request) ([]byte, error) {
 	cc.hbuf.Reset()
+
+	hlSize := uint64(0)
+	for k, vv := range req.Trailer {
+		for _, v := range vv {
+			hf := hpack.HeaderField{Name: k, Value: v}
+			hlSize += uint64(hf.Size())
+		}
+	}
+	if hlSize > cc.peerMaxHeaderListSize {
+		return nil, errRequestHeaderListSize
+	}
+
 	for k, vv := range req.Trailer {
-		// Transfer-Encoding, etc.. have already been filter at the
+		// Transfer-Encoding, etc.. have already been filtered at the
 		// start of RoundTrip
 		lowKey := strings.ToLower(k)
 		for _, v := range vv {
 			cc.writeHeader(lowKey, v)
 		}
 	}
-	return cc.hbuf.Bytes()
+	return cc.hbuf.Bytes(), nil
 }
 
 func (cc *ClientConn) writeHeader(name, value string) {
@@ -1911,6 +1954,8 @@ func (rl *clientConnReadLoop) processSettings(f *SettingsFrame) error {
 			cc.maxFrameSize = s.Val
 		case SettingMaxConcurrentStreams:
 			cc.maxConcurrentStreams = s.Val
+		case SettingMaxHeaderListSize:
+			cc.peerMaxHeaderListSize = uint64(s.Val)
 		case SettingInitialWindowSize:
 			// Values above the maximum flow-control
 			// window size of 2^31-1 MUST be treated as a
@@ -2077,6 +2122,7 @@ func (cc *ClientConn) writeStreamReset(streamID uint32, code ErrCode, err error)
 
 var (
 	errResponseHeaderListSize = errors.New("http2: response header list larger than advertised limit")
+	errRequestHeaderListSize  = errors.New("http2: request header list larger than peer's advertised limit")
 	errPseudoTrailers         = errors.New("http2: invalid pseudo header in trailers")
 )