src/gzip.cpp

   1 /*
   2
   3 Copyright (c) 2007, Arvid Norberg
   4 All rights reserved.
   5
   6 Redistribution and use in source and binary forms, with or without
   7 modification, are permitted provided that the following conditions
   8 are met:
   9
  10     * Redistributions of source code must retain the above copyright
  11       notice, this list of conditions and the following disclaimer.
  12     * Redistributions in binary form must reproduce the above copyright
  13       notice, this list of conditions and the following disclaimer in
  14       the documentation and/or other materials provided with the distribution.
  15     * Neither the name of the author nor the names of its
  16       contributors may be used to endorse or promote products derived
  17       from this software without specific prior written permission.
  18
  19 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  20 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  23 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29 POSSIBILITY OF SUCH DAMAGE.
  30
  31 */
  32
  33 #include "libtorrent/assert.hpp"
  34
  35 #include "zlib.h"
  36
  37 #include <vector>
  38
  39 namespace
  40 {
  41         enum
  42         {
  43                 FTEXT = 0x01,
  44                 FHCRC = 0x02,
  45                 FEXTRA = 0x04,
  46                 FNAME = 0x08,
  47                 FCOMMENT = 0x10,
  48                 FRESERVED = 0xe0,
  49
  50                 GZIP_MAGIC0 = 0x1f,
  51                 GZIP_MAGIC1 = 0x8b
  52         };
  53
  54 }
  55
  56 namespace libtorrent
  57 {
  58         // returns -1 if gzip header is invalid or the header size in bytes
  59         int gzip_header(const char* buf, int size)
  60         {
  61                 TORRENT_ASSERT(buf != 0);
  62                 TORRENT_ASSERT(size > 0);
  63
  64                 const unsigned char* buffer = reinterpret_cast<const unsigned char*>(buf);
  65                 const int total_size = size;
  66
  67                 // The zip header cannot be shorter than 10 bytes
  68                 if (size < 10) return -1;
  69
  70                 // check the magic header of gzip
  71                 if ((buffer[0] != GZIP_MAGIC0) || (buffer[1] != GZIP_MAGIC1)) return -1;
  72
  73                 int method = buffer[2];
  74                 int flags = buffer[3];
  75
  76                 // check for reserved flag and make sure it's compressed with the correct metod
  77                 if (method != Z_DEFLATED || (flags & FRESERVED) != 0) return -1;
  78
  79                 // skip time, xflags, OS code
  80                 size -= 10;
  81                 buffer += 10;
  82
  83                 if (flags & FEXTRA)
  84                 {
  85                         int extra_len;
  86
  87                         if (size < 2) return -1;
  88
  89                         extra_len = (buffer[1] << 8) | buffer[0];
  90
  91                         if (size < (extra_len+2)) return -1;
  92                         size -= (extra_len + 2);
  93                         buffer += (extra_len + 2);
  94                 }
  95
  96                 if (flags & FNAME)
  97                 {
  98                         while (size && *buffer)
  99                         {
 100                                 --size;
 101                                 ++buffer;
 102                         }
 103                         if (!size || *buffer) return -1;
 104
 105                         --size;
 106                         ++buffer;
 107                 }
 108
 109                 if (flags & FCOMMENT)
 110                 {
 111                         while (size && *buffer)
 112                         {
 113                                 --size;
 114                                 ++buffer;
 115                         }
 116                         if (!size || *buffer) return -1;
 117
 118                         --size;
 119                         ++buffer;
 120                 }
 121
 122                 if (flags & FHCRC)
 123                 {
 124                         if (size < 2) return -1;
 125
 126                         size -= 2;
 127                         buffer += 2;
 128                 }
 129
 130                 return total_size - size;
 131         }
 132
 133         bool inflate_gzip(
 134                 char const* in
 135                 , int size
 136                 , std::vector<char>& buffer
 137                 , int maximum_size
 138                 , std::string& error)
 139         {
 140                 TORRENT_ASSERT(maximum_size > 0);
 141
 142                 int header_len = gzip_header(in, size);
 143                 if (header_len < 0)
 144                 {
 145                         error = "invalid gzip header in tracker response";
 146                         return true;
 147                 }
 148
 149                 // start off with one kilobyte and grow
 150                 // if needed
 151                 buffer.resize(1024);
 152
 153                 // initialize the zlib-stream
 154                 z_stream str;
 155
 156                 // subtract 8 from the end of the buffer since that's CRC32 and input size
 157                 // and those belong to the gzip file
 158                 str.avail_in = (int)size - header_len - 8;
 159                 str.next_in = reinterpret_cast<Bytef*>(const_cast<char*>(in + header_len));
 160                 str.next_out = reinterpret_cast<Bytef*>(&buffer[0]);
 161                 str.avail_out = (int)buffer.size();
 162                 str.zalloc = Z_NULL;
 163                 str.zfree = Z_NULL;
 164                 str.opaque = 0;
 165                 // -15 is really important. It will make inflate() not look for a zlib header
 166                 // and just deflate the buffer
 167                 if (inflateInit2(&str, -15) != Z_OK)
 168                 {
 169                         error = "gzip out of memory";
 170                         return true;
 171                 }
 172
 173                 // inflate and grow inflate_buffer as needed
 174                 int ret = inflate(&str, Z_SYNC_FLUSH);
 175                 while (ret == Z_OK)
 176                 {
 177                         if (str.avail_out == 0)
 178                         {
 179                                 if (buffer.size() >= (unsigned)maximum_size)
 180                                 {
 181                                         inflateEnd(&str);
 182                                         error = "response too large";
 183                                         return true;
 184                                 }
 185                                 int new_size = (int)buffer.size() * 2;
 186                                 if (new_size > maximum_size)
 187                                         new_size = maximum_size;
 188                                 int old_size = (int)buffer.size();
 189
 190                                 buffer.resize(new_size);
 191                                 str.next_out = reinterpret_cast<Bytef*>(&buffer[old_size]);
 192                                 str.avail_out = new_size - old_size;
 193                         }
 194
 195                         ret = inflate(&str, Z_SYNC_FLUSH);
 196                 }
 197
 198                 buffer.resize(buffer.size() - str.avail_out);
 199                 inflateEnd(&str);
 200
 201                 if (ret != Z_STREAM_END)
 202                 {
 203                         error = "gzip error";
 204                         return true;
 205                 }
 206
 207                 // commit the resulting buffer
 208                 return false;
 209         }
 210
 211 }
 212