decoder.c

   1 /* @(#) $Id: ./src/analysisd/decoders/decoder.c, 2011/09/08 dcid Exp $
   2  */
   3
   4 /* Copyright (C) 2009 Trend Micro Inc.
   5  * All rights reserved.
   6  *
   7  * This program is a free software; you can redistribute it
   8  * and/or modify it under the terms of the GNU General Public
   9  * License (version 2) as published by the FSF - Free Software
  10  * Foundation.
  11  *
  12  * License details at the LICENSE file included with OSSEC or
  13  * online at: http://www.ossec.net/en/licensing.html
  14  */
  15
  16
  17 #include "shared.h"
  18 #include "os_regex/os_regex.h"
  19 #include "os_xml/os_xml.h"
  20
  21
  22 #include "eventinfo.h"
  23 #include "decoder.h"
  24
  25
  26
  27 /* DecodeEvent.
  28  * Will use the osdecoders to decode the received event.
  29  */
  30 void DecodeEvent(Eventinfo *lf)
  31 {
  32     OSDecoderNode *node;
  33     OSDecoderNode *child_node;
  34     OSDecoderInfo *nnode;
  35
  36     char *llog;
  37     char *pmatch;
  38     char *cmatch;
  39     char *regex_prev = NULL;
  40
  41
  42     node = OS_GetFirstOSDecoder(lf->program_name);
  43
  44
  45     /* Return if no node...
  46      * This shouldn't happen here anyways.
  47      */
  48     if(!node)
  49         return;
  50
  51
  52     #ifdef TESTRULE
  53     if(!alert_only)
  54     {
  55         print_out("\n**Phase 2: Completed decoding.");
  56     }
  57     #endif
  58
  59     do
  60     {
  61         nnode = node->osdecoder;
  62
  63
  64         /* First checking program name */
  65         if(lf->program_name)
  66         {
  67             if(!OSMatch_Execute(lf->program_name, lf->p_name_size,
  68                         nnode->program_name))
  69             {
  70                 continue;
  71             }
  72             pmatch = lf->log;
  73         }
  74
  75
  76         /* If prematch fails, go to the next osdecoder in the list */
  77         if(nnode->prematch)
  78         {
  79             if(!(pmatch = OSRegex_Execute(lf->log, nnode->prematch)))
  80             {
  81                 continue;
  82             }
  83
  84             /* Next character */
  85             if(*pmatch != '\0')
  86                 pmatch++;
  87         }
  88
  89
  90         #ifdef TESTRULE
  91         if(!alert_only)print_out("       decoder: '%s'", nnode->name);
  92         #endif
  93
  94
  95         lf->decoder_info = nnode;
  96
  97
  98         child_node = node->child;
  99
 100
 101         /* If no child node is set, set the child node
 102          * as if it were the child (ugh)
 103          */
 104         if(!child_node)
 105         {
 106             child_node = node;
 107         }
 108
 109         else
 110         {
 111             /* Check if we have any child osdecoder */
 112             while(child_node)
 113             {
 114                 nnode = child_node->osdecoder;
 115
 116
 117                 /* If we have a pre match and it matches, keep
 118                  * going. If we don't have a prematch, stop
 119                  * and go for the regexes.
 120                  */
 121                 if(nnode->prematch)
 122                 {
 123                     char *llog;
 124
 125                     /* If we have an offset set, use it */
 126                     if(nnode->prematch_offset & AFTER_PARENT)
 127                     {
 128                         llog = pmatch;
 129                     }
 130                     else
 131                     {
 132                         llog = lf->log;
 133                     }
 134
 135                     if((cmatch = OSRegex_Execute(llog, nnode->prematch)))
 136                     {
 137                         if(*cmatch != '\0')
 138                             cmatch++;
 139
 140                         lf->decoder_info = nnode;
 141
 142                         break;
 143                     }
 144                 }
 145                 else
 146                 {
 147                     cmatch = pmatch;
 148                     break;
 149                 }
 150
 151
 152                 /* If we have multiple regex-only childs,
 153                  * do not attempt to go any further with them.
 154                  */
 155                 if(child_node->osdecoder->get_next)
 156                 {
 157                     do
 158                     {
 159                         child_node = child_node->next;
 160                     }while(child_node && child_node->osdecoder->get_next);
 161
 162                     if(!child_node)
 163                         return;
 164
 165                     child_node = child_node->next;
 166                     nnode = NULL;
 167                 }
 168                 else
 169                 {
 170                     child_node = child_node->next;
 171                     nnode = NULL;
 172                 }
 173             }
 174         }
 175
 176
 177         /* Nothing matched */
 178         if(!nnode)
 179             return;
 180
 181
 182         /* If we have a external decoder, execute it */
 183         if(nnode->plugindecoder)
 184         {
 185             nnode->plugindecoder(lf);
 186             return;
 187         }
 188
 189
 190         /* Getting the regex */
 191         while(child_node)
 192         {
 193             if(nnode->regex)
 194             {
 195                 int i = 0;
 196
 197                 /* With regex we have multiple options
 198                  * regarding the offset:
 199                  * after the prematch,
 200                  * after the parent,
 201                  * after some previous regex,
 202                  * or any offset
 203                  */
 204                 if(nnode->regex_offset)
 205                 {
 206                     if(nnode->regex_offset & AFTER_PARENT)
 207                     {
 208                         llog = pmatch;
 209                     }
 210                     else if(nnode->regex_offset & AFTER_PREMATCH)
 211                     {
 212                         llog = cmatch;
 213                     }
 214                     else if(nnode->regex_offset & AFTER_PREVREGEX)
 215                     {
 216                         if(!regex_prev)
 217                             llog = cmatch;
 218                         else
 219                             llog = regex_prev;
 220                     }
 221                 }
 222                 else
 223                 {
 224                     llog = lf->log;
 225                 }
 226
 227                 /* If Regex does not match, return */
 228                 if(!(regex_prev = OSRegex_Execute(llog, nnode->regex)))
 229                 {
 230                     if(nnode->get_next)
 231                     {
 232                         child_node = child_node->next;
 233                         nnode = child_node->osdecoder;
 234                         continue;
 235                     }
 236                     return;
 237                 }
 238
 239
 240                 /* Fixing next pointer */
 241                 if(*regex_prev != '\0')
 242                     regex_prev++;
 243
 244                 while(nnode->regex->sub_strings[i])
 245                 {
 246                     if(nnode->order[i])
 247                     {
 248                         nnode->order[i](lf, nnode->regex->sub_strings[i]);
 249                         nnode->regex->sub_strings[i] = NULL;
 250                         i++;
 251                         continue;
 252                     }
 253
 254                     /* We do not free any memory used above */
 255                     os_free(nnode->regex->sub_strings[i]);
 256                     nnode->regex->sub_strings[i] = NULL;
 257                     i++;
 258                 }
 259
 260                 /* If we have a next regex, try getting it */
 261                 if(nnode->get_next)
 262                 {
 263                     child_node = child_node->next;
 264                     nnode = child_node->osdecoder;
 265                     continue;
 266                 }
 267
 268                 break;
 269             }
 270
 271             /* If we don't have a regex, we may leave now */
 272             return;
 273         }
 274
 275         /* ok to return  */
 276         return;
 277     }while((node=node->next) != NULL);
 278
 279     #ifdef TESTRULE
 280     if(!alert_only)
 281     {
 282         print_out("       No decoder matched.");
 283     }
 284     #endif
 285
 286 }
 287
 288
 289 /*** Event decoders ****/
 290 void *DstUser_FP(Eventinfo *lf, char *field)
 291 {
 292     #ifdef TESTRULE
 293     if(!alert_only)print_out("       dstuser: '%s'", field);
 294     #endif
 295
 296     lf->dstuser = field;
 297     return(NULL);
 298 }
 299 void *SrcUser_FP(Eventinfo *lf, char *field)
 300 {
 301     #ifdef TESTRULE
 302     if(!alert_only)print_out("       srcuser: '%s'", field);
 303     #endif
 304
 305     lf->srcuser = field;
 306     return(NULL);
 307 }
 308 void *SrcIP_FP(Eventinfo *lf, char *field)
 309 {
 310     #ifdef TESTRULE
 311     if(!alert_only)print_out("       srcip: '%s'", field);
 312     #endif
 313
 314     lf->srcip = field;
 315     return(NULL);
 316 }
 317 void *DstIP_FP(Eventinfo *lf, char *field)
 318 {
 319     #ifdef TESTRULE
 320     if(!alert_only)print_out("       dstip: '%s'", field);
 321     #endif
 322
 323     lf->dstip = field;
 324     return(NULL);
 325 }
 326 void *SrcPort_FP(Eventinfo *lf, char *field)
 327 {
 328     #ifdef TESTRULE
 329     if(!alert_only)print_out("       srcport: '%s'", field);
 330     #endif
 331
 332     lf->srcport = field;
 333     return(NULL);
 334 }
 335 void *DstPort_FP(Eventinfo *lf, char *field)
 336 {
 337     #ifdef TESTRULE
 338     if(!alert_only)print_out("       dstport: '%s'", field);
 339     #endif
 340
 341     lf->dstport = field;
 342     return(NULL);
 343 }
 344 void *Protocol_FP(Eventinfo *lf, char *field)
 345 {
 346     #ifdef TESTRULE
 347     if(!alert_only)print_out("       proto: '%s'", field);
 348     #endif
 349
 350     lf->protocol = field;
 351     return(NULL);
 352 }
 353 void *Action_FP(Eventinfo *lf, char *field)
 354 {
 355     #ifdef TESTRULE
 356     if(!alert_only)print_out("       action: '%s'", field);
 357     #endif
 358
 359     lf->action = field;
 360     return(NULL);
 361 }
 362 void *ID_FP(Eventinfo *lf, char *field)
 363 {
 364     #ifdef TESTRULE
 365     if(!alert_only)print_out("       id: '%s'", field);
 366     #endif
 367
 368     lf->id = field;
 369     return(NULL);
 370 }
 371 void *Url_FP(Eventinfo *lf, char *field)
 372 {
 373     #ifdef TESTRULE
 374     if(!alert_only)print_out("       url: '%s'", field);
 375     #endif
 376
 377     lf->url = field;
 378     return(NULL);
 379 }
 380 void *Data_FP(Eventinfo *lf, char *field)
 381 {
 382     #ifdef TESTRULE
 383     if(!alert_only)print_out("       extra_data: '%s'", field);
 384     #endif
 385
 386     lf->data = field;
 387     return(NULL);
 388 }
 389 void *Status_FP(Eventinfo *lf, char *field)
 390 {
 391     #ifdef TESTRULE
 392     if(!alert_only)print_out("       status: '%s'", field);
 393     #endif
 394
 395     lf->status = field;
 396     return(NULL);
 397 }
 398 void *SystemName_FP(Eventinfo *lf, char *field)
 399 {
 400     #ifdef TESTRULE
 401     if(!alert_only)print_out("       system_name: '%s'", field);
 402     #endif
 403
 404     lf->systemname = field;
 405     return(NULL);
 406 }
 407 void *None_FP(Eventinfo *lf, char *field)
 408 {
 409     free(field);
 410     return(NULL);
 411 }
 412
 413
 414 /* EOF */