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 "absl/strings/string_view.h"
18 #include "modules/rtp_rtcp/source/byte_io.h"
19 #include "modules/rtp_rtcp/source/rtcp_packet/common_header.h"
20 #include "rtc_base/checks.h"
21 #include "rtc_base/logging.h"
22
23 namespace webrtc {
24 namespace rtcp {
25 constexpr uint8_t Sdes::kPacketType;
26 constexpr size_t Sdes::kMaxNumberOfChunks;
27 // Source Description (SDES) (RFC 3550).
28 //
29 // 0 1 2 3
30 // 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
31 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
32 // header |V=2|P| SC | PT=SDES=202 | length |
33 // +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
34 // chunk | SSRC/CSRC_1 |
35 // 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
36 // | SDES items |
37 // | ... |
38 // +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
39 // chunk | SSRC/CSRC_2 |
40 // 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
41 // | SDES items |
42 // | ... |
43 // +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
44 //
45 // Canonical End-Point Identifier SDES Item (CNAME)
46 //
47 // 0 1 2 3
48 // 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
49 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
50 // | CNAME=1 | length | user and domain name ...
51 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
52 namespace {
53 const uint8_t kTerminatorTag = 0;
54 const uint8_t kCnameTag = 1;
55
ChunkSize(const Sdes::Chunk & chunk)56 size_t ChunkSize(const Sdes::Chunk& chunk) {
57 // Chunk:
58 // SSRC/CSRC (4 bytes) | CNAME=1 (1 byte) | length (1 byte) | cname | padding.
59 size_t chunk_payload_size = 4 + 1 + 1 + chunk.cname.size();
60 size_t padding_size = 4 - (chunk_payload_size % 4); // Minimum 1.
61 return chunk_payload_size + padding_size;
62 }
63 } // namespace
64
Sdes()65 Sdes::Sdes() : block_length_(RtcpPacket::kHeaderLength) {}
66
~Sdes()67 Sdes::~Sdes() {}
68
Parse(const CommonHeader & packet)69 bool Sdes::Parse(const CommonHeader& packet) {
70 RTC_DCHECK_EQ(packet.type(), kPacketType);
71
72 uint8_t number_of_chunks = packet.count();
73 std::vector<Chunk> chunks; // Read chunk into temporary array, so that in
74 // case of an error original array would stay
75 // unchanged.
76 size_t block_length = kHeaderLength;
77
78 if (packet.payload_size_bytes() % 4 != 0) {
79 RTC_LOG(LS_WARNING) << "Invalid payload size "
80 << packet.payload_size_bytes()
81 << " bytes for a valid Sdes packet. Size should be"
82 " multiple of 4 bytes";
83 }
84 const uint8_t* const payload_end =
85 packet.payload() + packet.payload_size_bytes();
86 const uint8_t* looking_at = packet.payload();
87 chunks.resize(number_of_chunks);
88 for (size_t i = 0; i < number_of_chunks;) {
89 // Each chunk consumes at least 8 bytes.
90 if (payload_end - looking_at < 8) {
91 RTC_LOG(LS_WARNING) << "Not enough space left for chunk #" << (i + 1);
92 return false;
93 }
94 chunks[i].ssrc = ByteReader<uint32_t>::ReadBigEndian(looking_at);
95 looking_at += sizeof(uint32_t);
96 bool cname_found = false;
97
98 uint8_t item_type;
99 while ((item_type = *(looking_at++)) != kTerminatorTag) {
100 if (looking_at >= payload_end) {
101 RTC_LOG(LS_WARNING)
102 << "Unexpected end of packet while reading chunk #" << (i + 1)
103 << ". Expected to find size of the text.";
104 return false;
105 }
106 uint8_t item_length = *(looking_at++);
107 const size_t kTerminatorSize = 1;
108 if (looking_at + item_length + kTerminatorSize > payload_end) {
109 RTC_LOG(LS_WARNING)
110 << "Unexpected end of packet while reading chunk #" << (i + 1)
111 << ". Expected to find text of size " << item_length;
112 return false;
113 }
114 if (item_type == kCnameTag) {
115 if (cname_found) {
116 RTC_LOG(LS_WARNING)
117 << "Found extra CNAME for same ssrc in chunk #" << (i + 1);
118 return false;
119 }
120 cname_found = true;
121 chunks[i].cname.assign(reinterpret_cast<const char*>(looking_at),
122 item_length);
123 }
124 looking_at += item_length;
125 }
126 if (cname_found) {
127 // block_length calculates length of the packet that would be generated by
128 // Build/Create functions. Adjust it same way WithCName function does.
129 block_length += ChunkSize(chunks[i]);
130 ++i;
131 } else {
132 // RFC states CNAME item is mandatory.
133 // But same time it allows chunk without items.
134 // So while parsing, ignore all chunks without cname,
135 // but do not fail the parse.
136 RTC_LOG(LS_WARNING) << "CNAME not found for ssrc " << chunks[i].ssrc;
137 --number_of_chunks;
138 chunks.resize(number_of_chunks);
139 }
140 // Adjust to 32bit boundary.
141 looking_at += (payload_end - looking_at) % 4;
142 }
143
144 chunks_ = std::move(chunks);
145 block_length_ = block_length;
146 return true;
147 }
148
AddCName(uint32_t ssrc,absl::string_view cname)149 bool Sdes::AddCName(uint32_t ssrc, absl::string_view cname) {
150 RTC_DCHECK_LE(cname.length(), 0xffu);
151 if (chunks_.size() >= kMaxNumberOfChunks) {
152 RTC_LOG(LS_WARNING) << "Max SDES chunks reached.";
153 return false;
154 }
155 Chunk chunk;
156 chunk.ssrc = ssrc;
157 chunk.cname = std::string(cname);
158 chunks_.push_back(chunk);
159 block_length_ += ChunkSize(chunk);
160 return true;
161 }
162
BlockLength() const163 size_t Sdes::BlockLength() const {
164 return block_length_;
165 }
166
Create(uint8_t * packet,size_t * index,size_t max_length,PacketReadyCallback callback) const167 bool Sdes::Create(uint8_t* packet,
168 size_t* index,
169 size_t max_length,
170 PacketReadyCallback callback) const {
171 while (*index + BlockLength() > max_length) {
172 if (!OnBufferFull(packet, index, callback))
173 return false;
174 }
175 const size_t index_end = *index + BlockLength();
176 CreateHeader(chunks_.size(), kPacketType, HeaderLength(), packet, index);
177
178 for (const Sdes::Chunk& chunk : chunks_) {
179 ByteWriter<uint32_t>::WriteBigEndian(&packet[*index + 0], chunk.ssrc);
180 ByteWriter<uint8_t>::WriteBigEndian(&packet[*index + 4], kCnameTag);
181 ByteWriter<uint8_t>::WriteBigEndian(
182 &packet[*index + 5], static_cast<uint8_t>(chunk.cname.size()));
183 memcpy(&packet[*index + 6], chunk.cname.data(), chunk.cname.size());
184 *index += (6 + chunk.cname.size());
185
186 // In each chunk, the list of items must be terminated by one or more null
187 // octets. The next chunk must start on a 32-bit boundary.
188 // CNAME (1 byte) | length (1 byte) | name | padding.
189 size_t padding_size = 4 - ((6 + chunk.cname.size()) % 4);
190 const int kPadding = 0;
191 memset(packet + *index, kPadding, padding_size);
192 *index += padding_size;
193 }
194
195 RTC_CHECK_EQ(*index, index_end);
196 return true;
197 }
198 } // namespace rtcp
199 } // namespace webrtc
200