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http2: Respect peer's SETTINGS_MAX_HEADER_LIST_SIZE in ClientConn
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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 <tombergan@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tom Bergan <tombergan@google.com>
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@appleby @tombergan
appleby authored and tombergan committed Aug 28, 2017
1 parent 57efc9c commit 66aacef
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Showing 2 changed files with 426 additions and 69 deletions.
182 changes: 114 additions & 68 deletions http2/transport.go
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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()
Expand Down Expand Up @@ -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
}

Expand All @@ -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) {
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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")
)

Expand Down
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