turn_utils.cc (4507B)
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 "media/base/turn_utils.h" 12 13 #include <cstddef> 14 #include <cstdint> 15 16 #include "api/transport/stun.h" 17 #include "rtc_base/byte_order.h" 18 19 namespace webrtc { 20 21 namespace { 22 23 const size_t kTurnChannelHeaderLength = 4; 24 25 bool IsTurnChannelData(const uint8_t* data, size_t length) { 26 return length >= kTurnChannelHeaderLength && ((*data & 0xC0) == 0x40); 27 } 28 29 bool IsTurnSendIndicationPacket(const uint8_t* data, size_t length) { 30 if (length < kStunHeaderSize) { 31 return false; 32 } 33 34 uint16_t type = GetBE16(data); 35 return (type == TURN_SEND_INDICATION); 36 } 37 38 } // namespace 39 40 bool UnwrapTurnPacket(const uint8_t* packet, 41 size_t packet_size, 42 size_t* content_position, 43 size_t* content_size) { 44 if (IsTurnChannelData(packet, packet_size)) { 45 // Turn Channel Message header format. 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 // | Channel Number | Length | 50 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 51 // | | 52 // / Application Data / 53 // / / 54 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 55 size_t length = GetBE16(&packet[2]); 56 if (length + kTurnChannelHeaderLength > packet_size) { 57 return false; 58 } 59 60 *content_position = kTurnChannelHeaderLength; 61 *content_size = length; 62 return true; 63 } 64 65 if (IsTurnSendIndicationPacket(packet, packet_size)) { 66 // Validate STUN message length. 67 const size_t stun_message_length = GetBE16(&packet[2]); 68 if (stun_message_length + kStunHeaderSize != packet_size) { 69 return false; 70 } 71 72 // First skip mandatory stun header which is of 20 bytes. 73 size_t pos = kStunHeaderSize; 74 // Loop through STUN attributes until we find STUN DATA attribute. 75 while (pos < packet_size) { 76 // Keep reading STUN attributes until we hit DATA attribute. 77 // Attribute will be a TLV structure. 78 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 79 // | Type | Length | 80 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 81 // | Value (variable) .... 82 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 83 // The value in the length field MUST contain the length of the Value 84 // part of the attribute, prior to padding, measured in bytes. Since 85 // STUN aligns attributes on 32-bit boundaries, attributes whose content 86 // is not a multiple of 4 bytes are padded with 1, 2, or 3 bytes of 87 // padding so that its value contains a multiple of 4 bytes. The 88 // padding bits are ignored, and may be any value. 89 uint16_t attr_type, attr_length; 90 const int kAttrHeaderLength = sizeof(attr_type) + sizeof(attr_length); 91 92 if (packet_size < pos + kAttrHeaderLength) { 93 return false; 94 } 95 96 // Getting attribute type and length. 97 attr_type = GetBE16(&packet[pos]); 98 attr_length = GetBE16(&packet[pos + sizeof(attr_type)]); 99 100 pos += kAttrHeaderLength; // Skip STUN_DATA_ATTR header. 101 102 // Checking for bogus attribute length. 103 if (pos + attr_length > packet_size) { 104 return false; 105 } 106 107 if (attr_type == STUN_ATTR_DATA) { 108 *content_position = pos; 109 *content_size = attr_length; 110 return true; 111 } 112 113 pos += attr_length; 114 if ((attr_length % 4) != 0) { 115 pos += (4 - (attr_length % 4)); 116 } 117 } 118 119 // There is no data attribute present in the message. 120 return false; 121 } 122 123 // This is not a TURN packet. 124 *content_position = 0; 125 *content_size = packet_size; 126 return true; 127 } 128 129 } // namespace webrtc