1 /*
2 * Copyright (c) 2016 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 "modules/rtp_rtcp/source/rtcp_packet/sdes.h"
12
13 #include <string.h>
14
15 #include <utility>
16
17 #include "modules/rtp_rtcp/source/byte_io.h"
18 #include "modules/rtp_rtcp/source/rtcp_packet/common_header.h"
19 #include "rtc_base/checks.h"
20 #include "rtc_base/logging.h"
21
22 namespace webrtc {
23 namespace rtcp {
24 constexpr uint8_t Sdes::kPacketType;
25 constexpr size_t Sdes::kMaxNumberOfChunks;
26 // Source Description (SDES) (RFC 3550).
27 //
28 // 0 1 2 3
29 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
30 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
31 // header |V=2|P| SC | PT=SDES=202 | length |
32 // +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
33 // chunk | SSRC/CSRC_1 |
34 // 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
35 // | SDES items |
36 // | ... |
37 // +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
38 // chunk | SSRC/CSRC_2 |
39 // 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
40 // | SDES items |
41 // | ... |
42 // +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
43 //
44 // Canonical End-Point Identifier SDES Item (CNAME)
45 //
46 // 0 1 2 3
47 // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
48 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
49 // | CNAME=1 | length | user and domain name ...
50 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
51 namespace {
52 const uint8_t kTerminatorTag = 0;
53 const uint8_t kCnameTag = 1;
54
ChunkSize(const Sdes::Chunk & chunk)55 size_t ChunkSize(const Sdes::Chunk& chunk) {
56 // Chunk:
57 // SSRC/CSRC (4 bytes) | CNAME=1 (1 byte) | length (1 byte) | cname | padding.
58 size_t chunk_payload_size = 4 + 1 + 1 + chunk.cname.size();
59 size_t padding_size = 4 - (chunk_payload_size % 4); // Minimum 1.
60 return chunk_payload_size + padding_size;
61 }
62 } // namespace
63
Sdes()64 Sdes::Sdes() : block_length_(RtcpPacket::kHeaderLength) {}
65
~Sdes()66 Sdes::~Sdes() {}
67
Parse(const CommonHeader & packet)68 bool Sdes::Parse(const CommonHeader& packet) {
69 RTC_DCHECK_EQ(packet.type(), kPacketType);
70
71 uint8_t number_of_chunks = packet.count();
72 std::vector<Chunk> chunks; // Read chunk into temporary array, so that in
73 // case of an error original array would stay
74 // unchanged.
75 size_t block_length = kHeaderLength;
76
77 if (packet.payload_size_bytes() % 4 != 0) {
78 RTC_LOG(LS_WARNING) << "Invalid payload size "
79 << packet.payload_size_bytes()
80 << " bytes for a valid Sdes packet. Size should be"
81 " multiple of 4 bytes";
82 }
83 const uint8_t* const payload_end =
84 packet.payload() + packet.payload_size_bytes();
85 const uint8_t* looking_at = packet.payload();
86 chunks.resize(number_of_chunks);
87 for (size_t i = 0; i < number_of_chunks;) {
88 // Each chunk consumes at least 8 bytes.
89 if (payload_end - looking_at < 8) {
90 RTC_LOG(LS_WARNING) << "Not enough space left for chunk #" << (i + 1);
91 return false;
92 }
93 chunks[i].ssrc = ByteReader<uint32_t>::ReadBigEndian(looking_at);
94 looking_at += sizeof(uint32_t);
95 bool cname_found = false;
96
97 uint8_t item_type;
98 while ((item_type = *(looking_at++)) != kTerminatorTag) {
99 if (looking_at >= payload_end) {
100 RTC_LOG(LS_WARNING)
101 << "Unexpected end of packet while reading chunk #" << (i + 1)
102 << ". Expected to find size of the text.";
103 return false;
104 }
105 uint8_t item_length = *(looking_at++);
106 const size_t kTerminatorSize = 1;
107 if (looking_at + item_length + kTerminatorSize > payload_end) {
108 RTC_LOG(LS_WARNING)
109 << "Unexpected end of packet while reading chunk #" << (i + 1)
110 << ". Expected to find text of size " << item_length;
111 return false;
112 }
113 if (item_type == kCnameTag) {
114 if (cname_found) {
115 RTC_LOG(LS_WARNING)
116 << "Found extra CNAME for same ssrc in chunk #" << (i + 1);
117 return false;
118 }
119 cname_found = true;
120 chunks[i].cname.assign(reinterpret_cast<const char*>(looking_at),
121 item_length);
122 }
123 looking_at += item_length;
124 }
125 if (cname_found) {
126 // block_length calculates length of the packet that would be generated by
127 // Build/Create functions. Adjust it same way WithCName function does.
128 block_length += ChunkSize(chunks[i]);
129 ++i;
130 } else {
131 // RFC states CNAME item is mandatory.
132 // But same time it allows chunk without items.
133 // So while parsing, ignore all chunks without cname,
134 // but do not fail the parse.
135 RTC_LOG(LS_WARNING) << "CNAME not found for ssrc " << chunks[i].ssrc;
136 --number_of_chunks;
137 chunks.resize(number_of_chunks);
138 }
139 // Adjust to 32bit boundary.
140 looking_at += (payload_end - looking_at) % 4;
141 }
142
143 chunks_ = std::move(chunks);
144 block_length_ = block_length;
145 return true;
146 }
147
AddCName(uint32_t ssrc,std::string cname)148 bool Sdes::AddCName(uint32_t ssrc, std::string cname) {
149 RTC_DCHECK_LE(cname.length(), 0xffu);
150 if (chunks_.size() >= kMaxNumberOfChunks) {
151 RTC_LOG(LS_WARNING) << "Max SDES chunks reached.";
152 return false;
153 }
154 Chunk chunk;
155 chunk.ssrc = ssrc;
156 chunk.cname = std::move(cname);
157 chunks_.push_back(chunk);
158 block_length_ += ChunkSize(chunk);
159 return true;
160 }
161
BlockLength() const162 size_t Sdes::BlockLength() const {
163 return block_length_;
164 }
165
Create(uint8_t * packet,size_t * index,size_t max_length,PacketReadyCallback callback) const166 bool Sdes::Create(uint8_t* packet,
167 size_t* index,
168 size_t max_length,
169 PacketReadyCallback callback) const {
170 while (*index + BlockLength() > max_length) {
171 if (!OnBufferFull(packet, index, callback))
172 return false;
173 }
174 const size_t index_end = *index + BlockLength();
175 CreateHeader(chunks_.size(), kPacketType, HeaderLength(), packet, index);
176
177 for (const Sdes::Chunk& chunk : chunks_) {
178 ByteWriter<uint32_t>::WriteBigEndian(&packet[*index + 0], chunk.ssrc);
179 ByteWriter<uint8_t>::WriteBigEndian(&packet[*index + 4], kCnameTag);
180 ByteWriter<uint8_t>::WriteBigEndian(
181 &packet[*index + 5], static_cast<uint8_t>(chunk.cname.size()));
182 memcpy(&packet[*index + 6], chunk.cname.data(), chunk.cname.size());
183 *index += (6 + chunk.cname.size());
184
185 // In each chunk, the list of items must be terminated by one or more null
186 // octets. The next chunk must start on a 32-bit boundary.
187 // CNAME (1 byte) | length (1 byte) | name | padding.
188 size_t padding_size = 4 - ((6 + chunk.cname.size()) % 4);
189 const int kPadding = 0;
190 memset(packet + *index, kPadding, padding_size);
191 *index += padding_size;
192 }
193
194 RTC_CHECK_EQ(*index, index_end);
195 return true;
196 }
197 } // namespace rtcp
198 } // namespace webrtc
199