epan/follow.c

   1 /* follow.c
   2  *
   3  * $Id$
   4  *
   5  * Copyright 1998 Mike Hall <mlh@io.com>
   6  *
   7  * Wireshark - Network traffic analyzer
   8  * By Gerald Combs <gerald@wireshark.org>
   9  * Copyright 1998 Gerald Combs
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License
  13  * as published by the Free Software Foundation; either version 2
  14  * of the License, or (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  24  *
  25  */
  26
  27 #include "config.h"
  28
  29 #include <stdlib.h>
  30 #include <stdio.h>
  31 #include <string.h>
  32 #ifdef HAVE_UNISTD_H
  33 #include <unistd.h>
  34 #endif
  35
  36 #include <glib.h>
  37 #include <epan/packet.h>
  38 #include <epan/to_str.h>
  39 #include <epan/emem.h>
  40 #include <epan/ipproto.h>
  41 #include <epan/dissectors/packet-tcp.h>
  42 #include "follow.h"
  43 #include <epan/conversation.h>
  44
  45 #define MAX_IPADDR_LEN  16
  46
  47 typedef struct _tcp_frag {
  48   guint32             seq;
  49   guint32             len;
  50   guint32             data_len;
  51   gchar              *data;
  52   struct _tcp_frag   *next;
  53 } tcp_frag;
  54
  55 WS_DLL_PUBLIC_DEF
  56 FILE* data_out_file = NULL;
  57
  58 gboolean empty_tcp_stream;
  59 gboolean incomplete_tcp_stream;
  60
  61 static guint32 tcp_stream_to_follow = 0;
  62 static guint8  ip_address[2][MAX_IPADDR_LEN];
  63 static guint   port[2];
  64 static guint   bytes_written[2];
  65 static gboolean is_ipv6 = FALSE;
  66
  67 static int check_fragments( int, tcp_stream_chunk *, guint32 );
  68 static void write_packet_data( int, tcp_stream_chunk *, const char * );
  69
  70 void
  71 follow_stats(follow_stats_t* stats)
  72 {
  73         int i;
  74
  75         for (i = 0; i < 2 ; i++) {
  76                 memcpy(stats->ip_address[i], ip_address[i], MAX_IPADDR_LEN);
  77                 stats->port[i] = port[i];
  78                 stats->bytes_written[i] = bytes_written[i];
  79                 stats->is_ipv6 = is_ipv6;
  80         }
  81 }
  82
  83 /* This will build a display filter text that will only
  84    pass the packets related to the stream. There is a
  85    chance that two streams could intersect, but not a
  86    very good one */
  87 gchar*
  88 build_follow_conv_filter( packet_info *pi ) {
  89   char* buf;
  90   int len;
  91   conversation_t *conv=NULL;
  92   struct tcp_analysis *tcpd;
  93
  94   if( ((pi->net_src.type == AT_IPv4 && pi->net_dst.type == AT_IPv4) ||
  95        (pi->net_src.type == AT_IPv6 && pi->net_dst.type == AT_IPv6))
  96         && pi->ipproto == IP_PROTO_TCP
  97         && (conv=find_conversation(pi->fd->num, &pi->src, &pi->dst, pi->ptype,
  98               pi->srcport, pi->destport, 0)) != NULL ) {
  99     /* TCP over IPv4 */
 100     tcpd=get_tcp_conversation_data(conv, pi);
 101     if (tcpd) {
 102       buf = g_strdup_printf("tcp.stream eq %d", tcpd->stream);
 103       tcp_stream_to_follow = tcpd->stream;
 104       if (pi->net_src.type == AT_IPv4) {
 105         len = 4;
 106         is_ipv6 = FALSE;
 107       } else {
 108         len = 16;
 109         is_ipv6 = TRUE;
 110       }
 111     } else {
 112       return NULL;
 113     }
 114   }
 115   else if( pi->net_src.type == AT_IPv4 && pi->net_dst.type == AT_IPv4
 116            && pi->ipproto == IP_PROTO_UDP ) {
 117   /* UDP over IPv4 */
 118     buf = g_strdup_printf(
 119              "(ip.addr eq %s and ip.addr eq %s) and (udp.port eq %d and udp.port eq %d)",
 120              ip_to_str((guint8 *)pi->net_src.data),
 121              ip_to_str((guint8 *)pi->net_dst.data),
 122              pi->srcport, pi->destport );
 123     len = 4;
 124     is_ipv6 = FALSE;
 125   }
 126   else if( pi->net_src.type == AT_IPv6 && pi->net_dst.type == AT_IPv6
 127         && pi->ipproto == IP_PROTO_UDP ) {
 128     /* UDP over IPv6 */
 129     buf = g_strdup_printf(
 130              "(ipv6.addr eq %s and ipv6.addr eq %s) and (udp.port eq %d and udp.port eq %d)",
 131              ip6_to_str((const struct e_in6_addr *)pi->net_src.data),
 132              ip6_to_str((const struct e_in6_addr *)pi->net_dst.data),
 133              pi->srcport, pi->destport );
 134     len = 16;
 135     is_ipv6 = TRUE;
 136   }
 137   else {
 138     return NULL;
 139   }
 140   memcpy(ip_address[0], pi->net_src.data, len);
 141   memcpy(ip_address[1], pi->net_dst.data, len);
 142   port[0] = pi->srcport;
 143   port[1] = pi->destport;
 144   return buf;
 145 }
 146
 147 static gboolean         find_tcp_addr;
 148 static address          tcp_addr[2];
 149 static gboolean         find_tcp_index;
 150
 151 gchar*
 152 build_follow_index_filter(void) {
 153   gchar *buf;
 154
 155   find_tcp_addr = TRUE;
 156   buf = g_strdup_printf("tcp.stream eq %d", tcp_stream_to_follow);
 157   return buf;
 158 }
 159
 160 /* select a tcp stream to follow via it's address/port pairs */
 161 gboolean
 162 follow_tcp_addr(const address *addr0, guint port0,
 163                 const address *addr1, guint port1)
 164 {
 165   if (addr0 == NULL || addr1 == NULL || addr0->type != addr1->type ||
 166       port0 > G_MAXUINT16 || port1 > G_MAXUINT16 )  {
 167     return FALSE;
 168   }
 169
 170   if (find_tcp_index || find_tcp_addr) {
 171     return FALSE;
 172   }
 173
 174   switch (addr0->type) {
 175   default:
 176     return FALSE;
 177   case AT_IPv4:
 178   case AT_IPv6:
 179     is_ipv6 = addr0->type == AT_IPv6;
 180     break;
 181   }
 182
 183   find_tcp_index = TRUE;
 184
 185   memcpy(ip_address[0], addr0->data, addr0->len);
 186   SET_ADDRESS(&tcp_addr[0], addr0->type, addr0->len, ip_address[0]);
 187   port[0] = port0;
 188
 189   memcpy(ip_address[1], addr1->data, addr1->len);
 190   SET_ADDRESS(&tcp_addr[1], addr1->type, addr1->len, ip_address[1]);
 191   port[1] = port1;
 192
 193   return TRUE;
 194 }
 195
 196 /* select a tcp stream to follow via its index */
 197 gboolean
 198 follow_tcp_index(guint32 indx)
 199 {
 200   if (find_tcp_index || find_tcp_addr) {
 201     return FALSE;
 202   }
 203
 204   if (indx > get_tcp_stream_count()) {
 205     return FALSE;
 206   }
 207
 208   find_tcp_addr = TRUE;
 209   tcp_stream_to_follow = indx;
 210   memset(ip_address, 0, sizeof ip_address);
 211   port[0] = port[1] = 0;
 212
 213   return TRUE;
 214 }
 215
 216 guint32
 217 get_follow_tcp_index(void) {
 218   return tcp_stream_to_follow;
 219 }
 220
 221 /* here we are going to try and reconstruct the data portion of a TCP
 222    session. We will try and handle duplicates, TCP fragments, and out
 223    of order packets in a smart way. */
 224
 225 static tcp_frag *frags[2] = { 0, 0 };
 226 static guint32 seq[2];
 227 static guint8 src_addr[2][MAX_IPADDR_LEN];
 228 static guint src_port[2] = { 0, 0 };
 229
 230 void
 231 reassemble_tcp( guint32 tcp_stream, guint32 sequence, guint32 acknowledgement,
 232                 guint32 length, const char* data, guint32 data_length,
 233                 int synflag, address *net_src, address *net_dst,
 234                 guint srcport, guint dstport) {
 235   guint8 srcx[MAX_IPADDR_LEN], dstx[MAX_IPADDR_LEN];
 236   int src_index, j, first = 0, len;
 237   guint32 newseq;
 238   tcp_frag *tmp_frag;
 239   tcp_stream_chunk sc;
 240
 241   src_index = -1;
 242
 243   /* First, check if this packet should be processed. */
 244   if (find_tcp_index) {
 245     if ((port[0] == srcport && port[1] == dstport &&
 246          ADDRESSES_EQUAL(&tcp_addr[0], net_src) &&
 247          ADDRESSES_EQUAL(&tcp_addr[1], net_dst))
 248         ||
 249         (port[1] == srcport && port[0] == dstport &&
 250          ADDRESSES_EQUAL(&tcp_addr[1], net_src) &&
 251          ADDRESSES_EQUAL(&tcp_addr[0], net_dst))) {
 252       find_tcp_index = FALSE;
 253       tcp_stream_to_follow = tcp_stream;
 254     }
 255     else {
 256       return;
 257     }
 258   }
 259   else if ( tcp_stream != tcp_stream_to_follow )
 260     return;
 261
 262   if ((net_src->type != AT_IPv4 && net_src->type != AT_IPv6) ||
 263       (net_dst->type != AT_IPv4 && net_dst->type != AT_IPv6))
 264     return;
 265
 266   if (net_src->type == AT_IPv4)
 267     len = 4;
 268   else
 269     len = 16;
 270
 271   memcpy(srcx, net_src->data, len);
 272   memcpy(dstx, net_dst->data, len);
 273
 274   /* follow_tcp_index() needs to learn address/port pairs */
 275   if (find_tcp_addr) {
 276     find_tcp_addr = FALSE;
 277     memcpy(ip_address[0], net_src->data, net_src->len);
 278     port[0] = srcport;
 279     memcpy(ip_address[1], net_dst->data, net_dst->len);
 280     port[1] = dstport;
 281   }
 282
 283   /* Check to see if we have seen this source IP and port before.
 284      (Yes, we have to check both source IP and port; the connection
 285      might be between two different ports on the same machine.) */
 286   for( j=0; j<2; j++ ) {
 287     if (memcmp(src_addr[j], srcx, len) == 0 && src_port[j] == srcport ) {
 288       src_index = j;
 289     }
 290   }
 291   /* we didn't find it if src_index == -1 */
 292   if( src_index < 0 ) {
 293     /* assign it to a src_index and get going */
 294     for( j=0; j<2; j++ ) {
 295       if( src_port[j] == 0 ) {
 296         memcpy(src_addr[j], srcx, len);
 297         src_port[j] = srcport;
 298         src_index = j;
 299         first = 1;
 300         break;
 301       }
 302     }
 303   }
 304   if( src_index < 0 ) {
 305     fprintf( stderr, "ERROR in reassemble_tcp: Too many addresses!\n");
 306     return;
 307   }
 308
 309   if( data_length < length ) {
 310     incomplete_tcp_stream = TRUE;
 311   }
 312
 313   /* Before adding data for this flow to the data_out_file, check whether
 314    * this frame acks fragments that were already seen. This happens when
 315    * frames are not in the capture file, but were actually seen by the
 316    * receiving host (Fixes bug 592).
 317    */
 318   if( frags[1-src_index] ) {
 319     memcpy(sc.src_addr, dstx, len);
 320     sc.src_port = dstport;
 321     sc.dlen     = 0;        /* Will be filled in in check_fragments */
 322     while ( check_fragments( 1-src_index, &sc, acknowledgement ) )
 323       ;
 324   }
 325
 326   /* Initialize our stream chunk.  This data gets written to disk. */
 327   memcpy(sc.src_addr, srcx, len);
 328   sc.src_port = srcport;
 329   sc.dlen     = data_length;
 330
 331   /* now that we have filed away the srcs, lets get the sequence number stuff
 332      figured out */
 333   if( first ) {
 334     /* this is the first time we have seen this src's sequence number */
 335     seq[src_index] = sequence + length;
 336     if( synflag ) {
 337       seq[src_index]++;
 338     }
 339     /* write out the packet data */
 340     write_packet_data( src_index, &sc, data );
 341     return;
 342   }
 343   /* if we are here, we have already seen this src, let's
 344      try and figure out if this packet is in the right place */
 345   if( sequence < seq[src_index] ) {
 346     /* this sequence number seems dated, but
 347        check the end to make sure it has no more
 348        info than we have already seen */
 349     newseq = sequence + length;
 350     if( newseq > seq[src_index] ) {
 351       guint32 new_len;
 352
 353       /* this one has more than we have seen. let's get the
 354          payload that we have not seen. */
 355
 356       new_len = seq[src_index] - sequence;
 357
 358       if ( data_length <= new_len ) {
 359         data = NULL;
 360         data_length = 0;
 361         incomplete_tcp_stream = TRUE;
 362       } else {
 363         data += new_len;
 364         data_length -= new_len;
 365       }
 366       sc.dlen = data_length;
 367       sequence = seq[src_index];
 368       length = newseq - seq[src_index];
 369
 370       /* this will now appear to be right on time :) */
 371     }
 372   }
 373   if ( sequence == seq[src_index] ) {
 374     /* right on time */
 375     seq[src_index] += length;
 376     if( synflag ) seq[src_index]++;
 377     if( data ) {
 378       write_packet_data( src_index, &sc, data );
 379     }
 380     /* done with the packet, see if it caused a fragment to fit */
 381     while( check_fragments( src_index, &sc, 0 ) )
 382       ;
 383   }
 384   else {
 385     /* out of order packet */
 386     if(data_length > 0 && GT_SEQ(sequence, seq[src_index]) ) {
 387       tmp_frag = (tcp_frag *)g_malloc( sizeof( tcp_frag ) );
 388       tmp_frag->data = (gchar *)g_malloc( data_length );
 389       tmp_frag->seq = sequence;
 390       tmp_frag->len = length;
 391       tmp_frag->data_len = data_length;
 392       memcpy( tmp_frag->data, data, data_length );
 393       if( frags[src_index] ) {
 394         tmp_frag->next = frags[src_index];
 395       } else {
 396         tmp_frag->next = NULL;
 397       }
 398       frags[src_index] = tmp_frag;
 399     }
 400   }
 401 } /* end reassemble_tcp */
 402
 403 /* here we search through all the frag we have collected to see if
 404    one fits */
 405 static int
 406 check_fragments( int idx, tcp_stream_chunk *sc, guint32 acknowledged ) {
 407   tcp_frag *prev = NULL;
 408   tcp_frag *current;
 409   guint32 lowest_seq;
 410   gchar *dummy_str;
 411
 412   current = frags[idx];
 413   if( current ) {
 414     lowest_seq = current->seq;
 415     while( current ) {
 416       if( GT_SEQ(lowest_seq, current->seq) ) {
 417         lowest_seq = current->seq;
 418       }
 419
 420       if( current->seq < seq[idx] ) {
 421         guint32 newseq;
 422         /* this sequence number seems dated, but
 423            check the end to make sure it has no more
 424            info than we have already seen */
 425         newseq = current->seq + current->len;
 426         if( newseq > seq[idx] ) {
 427           guint32 new_pos;
 428
 429           /* this one has more than we have seen. let's get the
 430              payload that we have not seen. This happens when
 431              part of this frame has been retransmitted */
 432
 433           new_pos = seq[idx] - current->seq;
 434
 435           if ( current->data_len > new_pos ) {
 436             sc->dlen = current->data_len - new_pos;
 437             write_packet_data( idx, sc, current->data + new_pos );
 438           }
 439
 440           seq[idx] += (current->len - new_pos);
 441         }
 442
 443         /* Remove the fragment from the list as the "new" part of it
 444          * has been processed or its data has been seen already in
 445          * another packet. */
 446         if( prev ) {
 447           prev->next = current->next;
 448         } else {
 449           frags[idx] = current->next;
 450         }
 451         g_free( current->data );
 452         g_free( current );
 453         return 1;
 454       }
 455
 456       if( current->seq == seq[idx] ) {
 457         /* this fragment fits the stream */
 458         if( current->data ) {
 459           sc->dlen = current->data_len;
 460           write_packet_data( idx, sc, current->data );
 461         }
 462         seq[idx] += current->len;
 463         if( prev ) {
 464           prev->next = current->next;
 465         } else {
 466           frags[idx] = current->next;
 467         }
 468         g_free( current->data );
 469         g_free( current );
 470         return 1;
 471       }
 472       prev = current;
 473       current = current->next;
 474     }
 475     if( GT_SEQ(acknowledged, lowest_seq) ) {
 476       /* There are frames missing in the capture file that were seen
 477        * by the receiving host. Add dummy stream chunk with the data
 478        * "[xxx bytes missing in capture file]".
 479        */
 480       dummy_str = g_strdup_printf("[%d bytes missing in capture file]",
 481                         (int)(lowest_seq - seq[idx]) );
 482       sc->dlen = (guint32) strlen(dummy_str);
 483       write_packet_data( idx, sc, dummy_str );
 484       g_free(dummy_str);
 485       seq[idx] = lowest_seq;
 486       return 1;
 487     }
 488   }
 489   return 0;
 490 }
 491
 492 /* this should always be called before we start to reassemble a stream */
 493 void
 494 reset_tcp_reassembly(void)
 495 {
 496   tcp_frag *current, *next;
 497   int i;
 498
 499   empty_tcp_stream = TRUE;
 500   incomplete_tcp_stream = FALSE;
 501   find_tcp_addr = FALSE;
 502   find_tcp_index = FALSE;
 503   for( i=0; i<2; i++ ) {
 504     seq[i] = 0;
 505     memset(src_addr[i], '\0', MAX_IPADDR_LEN);
 506     src_port[i] = 0;
 507     memset(ip_address[i], '\0', MAX_IPADDR_LEN);
 508     port[i] = 0;
 509     bytes_written[i] = 0;
 510     current = frags[i];
 511     while( current ) {
 512       next = current->next;
 513       g_free( current->data );
 514       g_free( current );
 515       current = next;
 516     }
 517     frags[i] = NULL;
 518   }
 519 }
 520
 521 static void
 522 write_packet_data( int idx, tcp_stream_chunk *sc, const char *data )
 523 {
 524   size_t ret;
 525
 526   ret = fwrite( sc, 1, sizeof(tcp_stream_chunk), data_out_file );
 527   DISSECTOR_ASSERT(sizeof(tcp_stream_chunk) == ret);
 528
 529   ret = fwrite( data, 1, sc->dlen, data_out_file );
 530   DISSECTOR_ASSERT(sc->dlen == ret);
 531
 532   bytes_written[idx] += sc->dlen;
 533   empty_tcp_stream = FALSE;
 534 }