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[FIXED] Websocket: possible panic when decoding CLOSE frame #821

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merged 2 commits into from Sep 13, 2021
Merged

[FIXED] Websocket: possible panic when decoding CLOSE frame #821

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d8b7496
[FIXED] Websocket: possible panic when decoding CLOSE frame
kozlovic Sep 12, 2021
949abff
Updates based on code review
kozlovic Sep 13, 2021
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31 changes: 19 additions & 12 deletions ws.go
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Expand Up @@ -53,6 +53,7 @@ const (
wsContinuationFrame = 0
wsMaxFrameHeaderSize = 14
wsMaxControlPayloadSize = 125
wsCloseSatusSize = 2

// From https://tools.ietf.org/html/rfc6455#section-11.7
wsCloseStatusNormalClosure = 1000
Expand Down Expand Up @@ -372,7 +373,6 @@ func (r *websocketReader) handleControlFrame(frameType wsOpCode, buf []byte, pos
var payload []byte
var err error

statusPos := pos
if rem > 0 {
payload, pos, err = wsGet(r.r, buf, pos, rem)
if err != nil {
Expand All @@ -382,17 +382,24 @@ func (r *websocketReader) handleControlFrame(frameType wsOpCode, buf []byte, pos
switch frameType {
case wsCloseMessage:
status := wsCloseStatusNoStatusReceived
body := ""
// If there is a payload, it should contain 2 unsigned bytes
// that represent the status code and then optional payload.
if len(payload) >= 2 {
status = int(binary.BigEndian.Uint16(buf[statusPos : statusPos+2]))
body = string(buf[statusPos+2 : statusPos+len(payload)])
if body != "" && !utf8.ValidString(body) {
// https://tools.ietf.org/html/rfc6455#section-5.5.1
// If body is present, it must be a valid utf8
status = wsCloseStatusInvalidPayloadData
body = "invalid utf8 body in close frame"
var body string
lp := len(payload)
// If there is a payload, the status is represented as a 2-byte
// unsigned integer (in network byte order). Then, there may be an
// optional body.
hasStatus, hasBody := lp >= wsCloseSatusSize, lp > wsCloseSatusSize
if hasStatus {
// Decode the status
status = int(binary.BigEndian.Uint16(payload[:wsCloseSatusSize]))
// Now if there is a body, capture it and make sure this is a valid UTF-8.
if hasBody {
body = string(payload[wsCloseSatusSize:])
if !utf8.ValidString(body) {
// https://tools.ietf.org/html/rfc6455#section-5.5.1
// If body is present, it must be a valid utf8
status = wsCloseStatusInvalidPayloadData
body = "invalid utf8 body in close frame"
}
}
}
r.nc.wsEnqueueCloseMsg(status, body)
Expand Down
23 changes: 23 additions & 0 deletions ws_test.go
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Expand Up @@ -226,6 +226,29 @@ func TestWSParseControlFrames(t *testing.T) {
if err != io.EOF || n != 0 {
t.Fatalf("Error on read: n=%v err=%v", n, err)
}

// Write a CLOSE without payload
mr.buf.Write([]byte{136, 2, 3, 232})
n, err = r.Read(p)
if err != io.EOF || n != 0 {
t.Fatalf("Error on read: n=%v err=%v", n, err)
}

// Write a CLOSE with invalid status
mr.buf.Write([]byte{136, 1, 100})
n, err = r.Read(p)
if err != io.EOF || n != 0 {
t.Fatalf("Error on read: n=%v err=%v", n, err)
}

// Write CLOSE with valid status and payload but call with a read buffer
// that has capacity of 1.
mr.buf.Write([]byte{136, 6, 3, 232, 't', 'e', 's', 't'})
pl := []byte{136}
n, err = r.Read(pl[:])
if err != io.EOF || n != 0 {
t.Fatalf("Error on read: n=%v err=%v", n, err)
}
}

func TestWSParseInvalidFrames(t *testing.T) {
Expand Down