1 /*
2 * Copyright 2013 The WebRTC Project Authors. All rights reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 #include "webrtc/p2p/base/asyncstuntcpsocket.h"
12
13 #include <string.h>
14
15 #include "webrtc/p2p/base/stun.h"
16 #include "webrtc/base/common.h"
17 #include "webrtc/base/logging.h"
18
19 namespace cricket {
20
21 static const size_t kMaxPacketSize = 64 * 1024;
22
23 typedef uint16_t PacketLength;
24 static const size_t kPacketLenSize = sizeof(PacketLength);
25 static const size_t kPacketLenOffset = 2;
26 static const size_t kBufSize = kMaxPacketSize + kStunHeaderSize;
27 static const size_t kTurnChannelDataHdrSize = 4;
28
IsStunMessage(uint16_t msg_type)29 inline bool IsStunMessage(uint16_t msg_type) {
30 // The first two bits of a channel data message are 0b01.
31 return (msg_type & 0xC000) ? false : true;
32 }
33
34 // AsyncStunTCPSocket
35 // Binds and connects |socket| and creates AsyncTCPSocket for
36 // it. Takes ownership of |socket|. Returns NULL if bind() or
37 // connect() fail (|socket| is destroyed in that case).
Create(rtc::AsyncSocket * socket,const rtc::SocketAddress & bind_address,const rtc::SocketAddress & remote_address)38 AsyncStunTCPSocket* AsyncStunTCPSocket::Create(
39 rtc::AsyncSocket* socket,
40 const rtc::SocketAddress& bind_address,
41 const rtc::SocketAddress& remote_address) {
42 return new AsyncStunTCPSocket(AsyncTCPSocketBase::ConnectSocket(
43 socket, bind_address, remote_address), false);
44 }
45
AsyncStunTCPSocket(rtc::AsyncSocket * socket,bool listen)46 AsyncStunTCPSocket::AsyncStunTCPSocket(
47 rtc::AsyncSocket* socket, bool listen)
48 : rtc::AsyncTCPSocketBase(socket, listen, kBufSize) {
49 }
50
Send(const void * pv,size_t cb,const rtc::PacketOptions & options)51 int AsyncStunTCPSocket::Send(const void *pv, size_t cb,
52 const rtc::PacketOptions& options) {
53 if (cb > kBufSize || cb < kPacketLenSize + kPacketLenOffset) {
54 SetError(EMSGSIZE);
55 return -1;
56 }
57
58 // If we are blocking on send, then silently drop this packet
59 if (!IsOutBufferEmpty())
60 return static_cast<int>(cb);
61
62 int pad_bytes;
63 size_t expected_pkt_len = GetExpectedLength(pv, cb, &pad_bytes);
64
65 // Accepts only complete STUN/ChannelData packets.
66 if (cb != expected_pkt_len)
67 return -1;
68
69 AppendToOutBuffer(pv, cb);
70
71 ASSERT(pad_bytes < 4);
72 char padding[4] = {0};
73 AppendToOutBuffer(padding, pad_bytes);
74
75 int res = FlushOutBuffer();
76 if (res <= 0) {
77 // drop packet if we made no progress
78 ClearOutBuffer();
79 return res;
80 }
81
82 // We claim to have sent the whole thing, even if we only sent partial
83 return static_cast<int>(cb);
84 }
85
ProcessInput(char * data,size_t * len)86 void AsyncStunTCPSocket::ProcessInput(char* data, size_t* len) {
87 rtc::SocketAddress remote_addr(GetRemoteAddress());
88 // STUN packet - First 4 bytes. Total header size is 20 bytes.
89 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
90 // |0 0| STUN Message Type | Message Length |
91 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
92
93 // TURN ChannelData
94 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
95 // | Channel Number | Length |
96 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
97
98 while (true) {
99 // We need at least 4 bytes to read the STUN or ChannelData packet length.
100 if (*len < kPacketLenOffset + kPacketLenSize)
101 return;
102
103 int pad_bytes;
104 size_t expected_pkt_len = GetExpectedLength(data, *len, &pad_bytes);
105 size_t actual_length = expected_pkt_len + pad_bytes;
106
107 if (*len < actual_length) {
108 return;
109 }
110
111 SignalReadPacket(this, data, expected_pkt_len, remote_addr,
112 rtc::CreatePacketTime(0));
113
114 *len -= actual_length;
115 if (*len > 0) {
116 memmove(data, data + actual_length, *len);
117 }
118 }
119 }
120
HandleIncomingConnection(rtc::AsyncSocket * socket)121 void AsyncStunTCPSocket::HandleIncomingConnection(
122 rtc::AsyncSocket* socket) {
123 SignalNewConnection(this, new AsyncStunTCPSocket(socket, false));
124 }
125
GetExpectedLength(const void * data,size_t len,int * pad_bytes)126 size_t AsyncStunTCPSocket::GetExpectedLength(const void* data, size_t len,
127 int* pad_bytes) {
128 *pad_bytes = 0;
129 PacketLength pkt_len =
130 rtc::GetBE16(static_cast<const char*>(data) + kPacketLenOffset);
131 size_t expected_pkt_len;
132 uint16_t msg_type = rtc::GetBE16(data);
133 if (IsStunMessage(msg_type)) {
134 // STUN message.
135 expected_pkt_len = kStunHeaderSize + pkt_len;
136 } else {
137 // TURN ChannelData message.
138 expected_pkt_len = kTurnChannelDataHdrSize + pkt_len;
139 // From RFC 5766 section 11.5
140 // Over TCP and TLS-over-TCP, the ChannelData message MUST be padded to
141 // a multiple of four bytes in order to ensure the alignment of
142 // subsequent messages. The padding is not reflected in the length
143 // field of the ChannelData message, so the actual size of a ChannelData
144 // message (including padding) is (4 + Length) rounded up to the nearest
145 // multiple of 4. Over UDP, the padding is not required but MAY be
146 // included.
147 if (expected_pkt_len % 4)
148 *pad_bytes = 4 - (expected_pkt_len % 4);
149 }
150 return expected_pkt_len;
151 }
152
153 } // namespace cricket
154