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| 1 /* |
| 2 * libjingle |
| 3 * Copyright 2016 Google Inc. |
| 4 * |
| 5 * Redistribution and use in source and binary forms, with or without |
| 6 * modification, are permitted provided that the following conditions are met: |
| 7 * |
| 8 * 1. Redistributions of source code must retain the above copyright notice, |
| 9 * this list of conditions and the following disclaimer. |
| 10 * 2. Redistributions in binary form must reproduce the above copyright notice, |
| 11 * this list of conditions and the following disclaimer in the documentation |
| 12 * and/or other materials provided with the distribution. |
| 13 * 3. The name of the author may not be used to endorse or promote products |
| 14 * derived from this software without specific prior written permission. |
| 15 * |
| 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED |
| 17 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |
| 18 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO |
| 19 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 20 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| 21 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; |
| 22 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
| 23 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR |
| 24 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF |
| 25 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 26 */ |
| 27 |
| 28 #include "talk/media/base/turnutils.h" |
| 29 |
| 30 #include "webrtc/base/byteorder.h" |
| 31 #include "webrtc/base/checks.h" |
| 32 #include "webrtc/p2p/base/stun.h" |
| 33 |
| 34 namespace cricket { |
| 35 |
| 36 namespace { |
| 37 |
| 38 const size_t kTurnChannelHeaderLength = 4; |
| 39 |
| 40 bool IsTurnChannelData(const uint8_t* data, size_t length) { |
| 41 return length >= kTurnChannelHeaderLength && ((*data & 0xC0) == 0x40); |
| 42 } |
| 43 |
| 44 bool IsTurnSendIndicationPacket(const uint8_t* data, size_t length) { |
| 45 if (length < kStunHeaderSize) { |
| 46 return false; |
| 47 } |
| 48 |
| 49 uint16_t type = rtc::GetBE16(data); |
| 50 return (type == TURN_SEND_INDICATION); |
| 51 } |
| 52 |
| 53 } // namespace |
| 54 |
| 55 bool UnwrapTurnPacket(const uint8_t* packet, |
| 56 size_t packet_size, |
| 57 size_t* content_position, |
| 58 size_t* content_size) { |
| 59 if (IsTurnChannelData(packet, packet_size)) { |
| 60 // Turn Channel Message header format. |
| 61 // 0 1 2 3 |
| 62 // 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 |
| 63 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| 64 // | Channel Number | Length | |
| 65 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| 66 // | | |
| 67 // / Application Data / |
| 68 // / / |
| 69 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| 70 size_t length = rtc::GetBE16(&packet[2]); |
| 71 if (length + kTurnChannelHeaderLength > packet_size) { |
| 72 return false; |
| 73 } |
| 74 |
| 75 *content_position = kTurnChannelHeaderLength; |
| 76 *content_size = length; |
| 77 return true; |
| 78 } |
| 79 |
| 80 if (IsTurnSendIndicationPacket(packet, packet_size)) { |
| 81 // Validate STUN message length. |
| 82 const size_t stun_message_length = rtc::GetBE16(&packet[2]); |
| 83 if (stun_message_length + kStunHeaderSize != packet_size) { |
| 84 return false; |
| 85 } |
| 86 |
| 87 // First skip mandatory stun header which is of 20 bytes. |
| 88 size_t pos = kStunHeaderSize; |
| 89 // Loop through STUN attributes until we find STUN DATA attribute. |
| 90 while (pos < packet_size) { |
| 91 // Keep reading STUN attributes until we hit DATA attribute. |
| 92 // Attribute will be a TLV structure. |
| 93 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| 94 // | Type | Length | |
| 95 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| 96 // | Value (variable) .... |
| 97 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| 98 // The value in the length field MUST contain the length of the Value |
| 99 // part of the attribute, prior to padding, measured in bytes. Since |
| 100 // STUN aligns attributes on 32-bit boundaries, attributes whose content |
| 101 // is not a multiple of 4 bytes are padded with 1, 2, or 3 bytes of |
| 102 // padding so that its value contains a multiple of 4 bytes. The |
| 103 // padding bits are ignored, and may be any value. |
| 104 uint16_t attr_type, attr_length; |
| 105 const int kAttrHeaderLength = sizeof(attr_type) + sizeof(attr_length); |
| 106 |
| 107 if (packet_size < pos + kAttrHeaderLength) { |
| 108 return false; |
| 109 } |
| 110 |
| 111 // Getting attribute type and length. |
| 112 attr_type = rtc::GetBE16(&packet[pos]); |
| 113 attr_length = rtc::GetBE16(&packet[pos + sizeof(attr_type)]); |
| 114 |
| 115 pos += kAttrHeaderLength; // Skip STUN_DATA_ATTR header. |
| 116 |
| 117 // Checking for bogus attribute length. |
| 118 if (pos + attr_length > packet_size) { |
| 119 return false; |
| 120 } |
| 121 |
| 122 if (attr_type == STUN_ATTR_DATA) { |
| 123 *content_position = pos; |
| 124 *content_size = attr_length; |
| 125 return true; |
| 126 } |
| 127 |
| 128 pos += attr_length; |
| 129 if ((attr_length % 4) != 0) { |
| 130 pos += (4 - (attr_length % 4)); |
| 131 } |
| 132 } |
| 133 |
| 134 // There is no data attribute present in the message. |
| 135 return false; |
| 136 } |
| 137 |
| 138 // This is not a TURN packet. |
| 139 *content_position = 0; |
| 140 *content_size = packet_size; |
| 141 return true; |
| 142 } |
| 143 |
| 144 } // namespace cricket |
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