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* Copyright (C) 2009 Barracuda Networks, Inc.
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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* This library is distributed in the hope that it will be useful,
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* but WITHANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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#include "stunmessage.h"
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#include <QSharedData>
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#define ENSURE_D { if(!d) d = new Private; }
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// some attribute types we need to explicitly support
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AttribMessageIntegrity = 0x0008,
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AttribFingerprint = 0x8028
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// adapted from public domain source by Ross Williams and Eric Durbin
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unsigned long crctable[256] =
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0x00000000L, 0x77073096L, 0xEE0E612CL, 0x990951BAL,
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0x076DC419L, 0x706AF48FL, 0xE963A535L, 0x9E6495A3L,
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0x0EDB8832L, 0x79DCB8A4L, 0xE0D5E91EL, 0x97D2D988L,
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0x09B64C2BL, 0x7EB17CBDL, 0xE7B82D07L, 0x90BF1D91L,
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0x1DB71064L, 0x6AB020F2L, 0xF3B97148L, 0x84BE41DEL,
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0x1ADAD47DL, 0x6DDDE4EBL, 0xF4D4B551L, 0x83D385C7L,
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0x136C9856L, 0x646BA8C0L, 0xFD62F97AL, 0x8A65C9ECL,
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0x14015C4FL, 0x63066CD9L, 0xFA0F3D63L, 0x8D080DF5L,
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0x3B6E20C8L, 0x4C69105EL, 0xD56041E4L, 0xA2677172L,
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0x3C03E4D1L, 0x4B04D447L, 0xD20D85FDL, 0xA50AB56BL,
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0x35B5A8FAL, 0x42B2986CL, 0xDBBBC9D6L, 0xACBCF940L,
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0x32D86CE3L, 0x45DF5C75L, 0xDCD60DCFL, 0xABD13D59L,
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0x26D930ACL, 0x51DE003AL, 0xC8D75180L, 0xBFD06116L,
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0x21B4F4B5L, 0x56B3C423L, 0xCFBA9599L, 0xB8BDA50FL,
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0x2802B89EL, 0x5F058808L, 0xC60CD9B2L, 0xB10BE924L,
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0x2F6F7C87L, 0x58684C11L, 0xC1611DABL, 0xB6662D3DL,
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0x76DC4190L, 0x01DB7106L, 0x98D220BCL, 0xEFD5102AL,
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0x71B18589L, 0x06B6B51FL, 0x9FBFE4A5L, 0xE8B8D433L,
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0x7807C9A2L, 0x0F00F934L, 0x9609A88EL, 0xE10E9818L,
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0x7F6A0DBBL, 0x086D3D2DL, 0x91646C97L, 0xE6635C01L,
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0x6B6B51F4L, 0x1C6C6162L, 0x856530D8L, 0xF262004EL,
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0x6C0695EDL, 0x1B01A57BL, 0x8208F4C1L, 0xF50FC457L,
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0x65B0D9C6L, 0x12B7E950L, 0x8BBEB8EAL, 0xFCB9887CL,
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0x62DD1DDFL, 0x15DA2D49L, 0x8CD37CF3L, 0xFBD44C65L,
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0x4DB26158L, 0x3AB551CEL, 0xA3BC0074L, 0xD4BB30E2L,
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0x4ADFA541L, 0x3DD895D7L, 0xA4D1C46DL, 0xD3D6F4FBL,
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0x4369E96AL, 0x346ED9FCL, 0xAD678846L, 0xDA60B8D0L,
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0x44042D73L, 0x33031DE5L, 0xAA0A4C5FL, 0xDD0D7CC9L,
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0x5005713CL, 0x270241AAL, 0xBE0B1010L, 0xC90C2086L,
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0x5768B525L, 0x206F85B3L, 0xB966D409L, 0xCE61E49FL,
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0x5EDEF90EL, 0x29D9C998L, 0xB0D09822L, 0xC7D7A8B4L,
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0x59B33D17L, 0x2EB40D81L, 0xB7BD5C3BL, 0xC0BA6CADL,
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0xEDB88320L, 0x9ABFB3B6L, 0x03B6E20CL, 0x74B1D29AL,
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0xEAD54739L, 0x9DD277AFL, 0x04DB2615L, 0x73DC1683L,
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0xE3630B12L, 0x94643B84L, 0x0D6D6A3EL, 0x7A6A5AA8L,
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0xE40ECF0BL, 0x9309FF9DL, 0x0A00AE27L, 0x7D079EB1L,
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0xF00F9344L, 0x8708A3D2L, 0x1E01F268L, 0x6906C2FEL,
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0xF762575DL, 0x806567CBL, 0x196C3671L, 0x6E6B06E7L,
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0xFED41B76L, 0x89D32BE0L, 0x10DA7A5AL, 0x67DD4ACCL,
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0xF9B9DF6FL, 0x8EBEEFF9L, 0x17B7BE43L, 0x60B08ED5L,
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0xD6D6A3E8L, 0xA1D1937EL, 0x38D8C2C4L, 0x4FDFF252L,
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0xD1BB67F1L, 0xA6BC5767L, 0x3FB506DDL, 0x48B2364BL,
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0xD80D2BDAL, 0xAF0A1B4CL, 0x36034AF6L, 0x41047A60L,
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0xDF60EFC3L, 0xA867DF55L, 0x316E8EEFL, 0x4669BE79L,
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0xCB61B38CL, 0xBC66831AL, 0x256FD2A0L, 0x5268E236L,
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0xCC0C7795L, 0xBB0B4703L, 0x220216B9L, 0x5505262FL,
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0xC5BA3BBEL, 0xB2BD0B28L, 0x2BB45A92L, 0x5CB36A04L,
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0xC2D7FFA7L, 0xB5D0CF31L, 0x2CD99E8BL, 0x5BDEAE1DL,
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0x9B64C2B0L, 0xEC63F226L, 0x756AA39CL, 0x026D930AL,
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0x9C0906A9L, 0xEB0E363FL, 0x72076785L, 0x05005713L,
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0x95BF4A82L, 0xE2B87A14L, 0x7BB12BAEL, 0x0CB61B38L,
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0x92D28E9BL, 0xE5D5BE0DL, 0x7CDCEFB7L, 0x0BDBDF21L,
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0x86D3D2D4L, 0xF1D4E242L, 0x68DDB3F8L, 0x1FDA836EL,
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0x81BE16CDL, 0xF6B9265BL, 0x6FB077E1L, 0x18B74777L,
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0x88085AE6L, 0xFF0F6A70L, 0x66063BCAL, 0x11010B5CL,
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0x8F659EFFL, 0xF862AE69L, 0x616BFFD3L, 0x166CCF45L,
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0xA00AE278L, 0xD70DD2EEL, 0x4E048354L, 0x3903B3C2L,
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0xA7672661L, 0xD06016F7L, 0x4969474DL, 0x3E6E77DBL,
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0xAED16A4AL, 0xD9D65ADCL, 0x40DF0B66L, 0x37D83BF0L,
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0xA9BCAE53L, 0xDEBB9EC5L, 0x47B2CF7FL, 0x30B5FFE9L,
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0xBDBDF21CL, 0xCABAC28AL, 0x53B39330L, 0x24B4A3A6L,
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0xBAD03605L, 0xCDD70693L, 0x54DE5729L, 0x23D967BFL,
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0xB3667A2EL, 0xC4614AB8L, 0x5D681B02L, 0x2A6F2B94L,
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0xB40BBE37L, 0xC30C8EA1L, 0x5A05DF1BL, 0x2D02EF8DL
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void update(const QByteArray &in)
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for(int n = 0; n < in.size(); ++n)
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result = (result >> 8) ^ (crctable[(result & 0xff) ^ (quint8)in[n]]);
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return result ^= 0xffffffff;
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static quint32 process(const QByteArray &in)
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static quint8 magic_cookie[4] = { 0x21, 0x12, 0xA4, 0x42 };
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static quint16 read16(const quint8 *in)
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static quint32 read32(const quint8 *in)
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static void write16(quint8 *out, quint16 i)
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out[0] = (i >> 8) & 0xff;
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static void write32(quint8 *out, quint32 i)
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out[0] = (i >> 24) & 0xff;
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out[1] = (i >> 16) & 0xff;
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out[2] = (i >> 8) & 0xff;
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// do 3-field check of stun packet
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// returns length of packet not counting the header, or -1 on error
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static int check_and_get_length(const QByteArray &buf)
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// stun packets are at least 20 bytes
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// minimal 3-field check
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// top 2 bits of packet must be 0
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const quint8 *p = (const quint8 *)buf.data();
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quint16 mlen = read16(p + 2);
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// bottom 2 bits of message length field must be 0
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// (also, the message length should be a reasonable size)
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if(mlen + 20 > buf.size())
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// magic cookie must be set
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if(memcmp(p + 4, magic_cookie, 4) != 0)
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#define ATTRIBUTE_AREA_START 20
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#define ATTRIBUTE_AREA_MAX 65535
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#define ATTRIBUTE_VALUE_MAX 65531
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// note: because the attribute area of the packet has a maximum size of
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// 2^16-1, and each attribute itself has a 4 byte header, it follows that
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// the maximum size of an attribute's value is 2^16-5. this means that,
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// even if padded with up to 3 bytes, the physical size of an attribute's
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// value will not overflow a 16-bit unsigned integer.
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static quint16 round_up_length(quint16 in)
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Q_ASSERT(in <= ATTRIBUTE_VALUE_MAX);
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quint16 remainder = out % 4;
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out += (4 - remainder);
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// buf = entire stun packet
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// offset = byte index of current attribute (first is offset=20)
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// type = take attribute type
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// len = take attribute value length (value is at offset + 4)
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// returns offset of next attribute, -1 if no more
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static int get_attribute_props(const QByteArray &buf, int offset, quint16 *type, int *len)
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Q_ASSERT(offset >= ATTRIBUTE_AREA_START);
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const quint8 *p = (const quint8 *)buf.data();
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// need at least 4 bytes for an attribute
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if(offset + 4 > buf.size())
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quint16 _type = read16(p + offset);
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quint16 _alen = read16(p + offset);
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// get physical length. stun attributes are 4-byte aligned, and may
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// contain 0-3 bytes of padding.
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quint16 plen = round_up_length(_alen);
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if(offset + plen > buf.size())
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return offset + plen;
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// buf = entire stun packet
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// type = attribute type to find
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// len = take attribute value length (value is at offset + 4)
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// next = take offset of next attribute
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// returns offset of found attribute, -1 if not found
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static int find_attribute(const QByteArray &buf, quint16 type, int *len, int *next = 0)
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int at = ATTRIBUTE_AREA_START;
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_next = get_attribute_props(buf, at, &_type, &_len);
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// buf = stun packet to append attribute to
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// type = type of attribute
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// len = length of value
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// returns offset of new attribute, or -1 if it can't fit
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// note: attribute value is located at offset + 4 and is uninitialized
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// note: padding following attribute is zeroed out
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static int append_attribute_uninitialized(QByteArray *buf, quint16 type, int len)
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if(len > ATTRIBUTE_VALUE_MAX)
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quint16 alen = (quint16)len;
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quint16 plen = round_up_length(alen);
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if((buf->size() - ATTRIBUTE_AREA_START) + 4 + plen > ATTRIBUTE_AREA_MAX)
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int at = buf->size();
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buf->resize(buf->size() + 4 + plen);
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quint8 *p = (quint8 *)buf->data();
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write16(p + at, type);
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write16(p + at + 2, alen);
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for(int n = 0; n < plen - alen; ++n)
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p[at + alen + n] = 0;
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static quint32 fingerprint_calc(const quint8 *buf, int size)
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QByteArray region = QByteArray::fromRawData((const char *)buf, size);
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return Crc32::process(region) ^ 0x5354554e;
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static QByteArray message_integrity_calc(const quint8 *buf, int size, const QByteArray &key)
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QCA::MessageAuthenticationCode hmac("hmac(sha1)", key);
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QByteArray region = QByteArray::fromRawData((const char *)buf, size);
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QByteArray result = hmac.process(region).toByteArray();
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Q_ASSERT(result.size() == 20);
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// look for fingerprint attribute and confirm it
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// buf = entire stun packet
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// returns true if fingerprint attribute exists and is correct
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static bool fingerprint_check(const QByteArray &buf)
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at = find_attribute(buf, AttribFingerprint, &len);
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if(at == -1 || len != 4) // value must be 4 bytes
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const quint8 *p = (const quint8 *)buf.data();
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quint32 fpval = read32(p + at + 4);
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quint32 fpcalc = fingerprint_calc(p, at);
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// copy the input buffer and prepare for message integrity checking. the
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// packet is truncated after the message-integrity attribute (since nothing
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// after it is protected), and the packet length is adjusted in the header
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// buf = input stun packet
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// out = take output stun packet
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// offset = take offset of message-integrity attribute
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// returns true if message-integrity attribute exists and packet is prepared
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// note: message-integrity value is at offset + 4 and is exactly 20 bytes
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static bool message_integrity_prep(const QByteArray &buf, QByteArray *out, int *offset)
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at = find_attribute(buf, AttribMessageIntegrity, &len, &next);
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if(at == -1 || len != 20) // value must be 20 bytes
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// prepare new attribute area size
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int i = next - ATTRIBUTE_AREA_START;
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// new value must be divisible by 4
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// copy truncated packet
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*out = buf.mid(0, next);
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// set new length in header
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quint16 newlen = (quint16)i;
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write16((quint8 *)out->data() + 2, newlen);
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// confirm message integrity
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// buf = prepared stun packet (from message_integrity_prep())
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// offset = offset of message-integrity attribute
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// key = the HMAC key
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// returns true if correct
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static bool message_integrity_check(const QByteArray &buf, int offset, const QByteArray &key)
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QByteArray mival = QByteArray::fromRawData(buf.data() + offset + 4, 20);
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QByteArray micalc = message_integrity_calc((const quint8 *)buf.data(), offset, key);
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class StunMessage::Private : public QSharedData
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StunMessage::Class mclass;
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QList<Attribute> attribs;
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mclass = (StunMessage::Class)-1;
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memcpy(magic, magic_cookie, 4);
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StunMessage::StunMessage() :
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StunMessage::StunMessage(const StunMessage &from) :
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StunMessage::~StunMessage()
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StunMessage & StunMessage::operator=(const StunMessage &from)
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bool StunMessage::isNull() const
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return (d ? false: true);
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StunMessage::Class StunMessage::mclass() const
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quint16 StunMessage::method() const
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const quint8 *StunMessage::magic() const
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const quint8 *StunMessage::id() const
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QList<StunMessage::Attribute> StunMessage::attributes() const
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QByteArray StunMessage::attribute(quint16 type) const
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foreach(const Attribute &i, d->attribs)
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void StunMessage::setClass(Class mclass)
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void StunMessage::setMethod(quint16 method)
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void StunMessage::setMagic(const quint8 *magic)
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memcpy(d->magic, magic, 4);
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void StunMessage::setId(const quint8 *id)
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memcpy(d->id, id, 12);
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void StunMessage::setAttributes(const QList<Attribute> &attribs)
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d->attribs = attribs;
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QByteArray StunMessage::toBinary(int validationFlags, const QByteArray &key) const
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QByteArray buf(20, 0);
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quint8 *p = (quint8 *)buf.data();
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quint8 classbits = 0;
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if(d->mclass == Request)
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else if(d->mclass == Indication)
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else if(d->mclass == SuccessResponse)
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else if(d->mclass == ErrorResponse)
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// method bits are split into 3 sections
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m1 = d->method & 0x0f80; // M7-11
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m2 = d->method & 0x0070; // M4-6
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m3 = d->method & 0x000f; // M0-3
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// class bits are split into 2 sections
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c1 = classbits & 0x02; // C1
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c2 = classbits & 0x01; // C0
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quint16 type = m1 | m2 | m3 | c1 | c2;
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memcpy(p + 4, d->magic, 4);
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memcpy(p + 8, d->id, 12);
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foreach(const Attribute &i, d->attribs)
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int at = append_attribute_uninitialized(&buf, i.type, i.value.size());
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memcpy(buf.data() + at + 4, i.value.data(), i.value.size());
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// set attribute area size
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write16(p + 2, buf.size() - ATTRIBUTE_AREA_START);
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if(validationFlags & MessageIntegrity)
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quint16 alen = 20; // size of hmac(sha1)
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int at = append_attribute_uninitialized(&buf, AttribMessageIntegrity, alen);
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p = (quint8 *)buf.data(); // follow the resize
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// set attribute area size to include the new attribute
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write16(p + 2, buf.size() - ATTRIBUTE_AREA_START);
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// now calculate the hash and fill in the value
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QByteArray result = message_integrity_calc(p, at, key);
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Q_ASSERT(result.size() == alen);
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memcpy(p + at + 4, result.data(), alen);
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if(validationFlags & Fingerprint)
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quint16 alen = 4; // size of crc32
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int at = append_attribute_uninitialized(&buf, AttribFingerprint, alen);
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p = (quint8 *)buf.data(); // follow the resize
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// set attribute area size to include the new attribute
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write16(p + 2, buf.size() - ATTRIBUTE_AREA_START);
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// now calculate the fingerprint and fill in the value
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quint32 fpcalc = fingerprint_calc(p, at);
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write32(p + at + 4, fpcalc);
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StunMessage StunMessage::fromBinary(const QByteArray &a, ConvertResult *result, int validationFlags, const QByteArray &key)
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int mlen = check_and_get_length(a);
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*result = ErrorFormat;
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return StunMessage();
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if(validationFlags & Fingerprint)
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if(!fingerprint_check(a))
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*result = ErrorFingerprint;
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return StunMessage();
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if(validationFlags & MessageIntegrity)
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if(!message_integrity_prep(a, &in, &offset))
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*result = ErrorMessageIntegrity;
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return StunMessage();
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if(!message_integrity_check(in, offset, key))
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*result = ErrorMessageIntegrity;
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return StunMessage();
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// all validating complete, now just parse the packet
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const quint8 *p = (const quint8 *)in.data();
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// method bits are split into 3 sections
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m1 = p[0] & 0x3e; // M7-11
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m2 = p[1] & 0xe0; // M4-6
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m3 = p[1] & 0x0f; // M0-3
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// class bits are split into 2 sections
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c1 = p[0] & 0x01; // C1
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c2 = p[1] & 0x10; // C0
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quint16 method = m1 | m2 | m3;
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quint8 classbits = c1 | c2;
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if(classbits == 0) // 00
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else if(classbits == 1) // 01
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else if(classbits == 2) // 10
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mclass = SuccessResponse;
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mclass = ErrorResponse;
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out.setClass(mclass);
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out.setMethod(method);
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QList<Attribute> list;
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int at = ATTRIBUTE_AREA_START;
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next = get_attribute_props(in, at, &type, &len);
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attrib.value = in.mid(at + 4, len);
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out.setAttributes(list);
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*result = ConvertGood;
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bool StunMessage::isProbablyStun(const QByteArray &a)
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return (check_and_get_length(a) != -1 ? true: false);