release/src/router/iptables/extensions/libipt_layer7.c

   1 /*
   2    Shared library add-on to iptables to add layer 7 matching support.
   3
   4    By Matthew Strait <quadong@users.sf.net>, Oct 2003.
   5
   6    http://l7-filter.sf.net
   7
   8    This program is free software; you can redistribute it and/or
   9    modify it under the terms of the GNU General Public License
  10    as published by the Free Software Foundation; either version
  11    2 of the License, or (at your option) any later version.
  12    http://www.gnu.org/licenses/gpl.txt
  13
  14    Based on libipt_string.c (C) 2000 Emmanuel Roger <winfield@freegates.be>
  15 */
  16
  17 #define _GNU_SOURCE
  18 #include <stdio.h>
  19 #include <netdb.h>
  20 #include <string.h>
  21 #include <stdlib.h>
  22 #include <getopt.h>
  23 #include <ctype.h>
  24 #include <dirent.h>
  25
  26 #include <iptables.h>
  27 #include <linux/netfilter_ipv4/ipt_layer7.h>
  28
  29 #define MAX_FN_LEN 256
  30
  31 static char l7dir[MAX_FN_LEN] = "\0";
  32
  33 /* Function which prints out usage message. */
  34 static void help(void)
  35 {
  36         printf(
  37         "LAYER7 match v%s options:\n"
  38         "--l7dir <directory>  : Look for patterns here instead of /etc/l7-protocols/\n"
  39         "                       (--l7dir must be specified before --l7proto if used!)\n"
  40         "--l7proto [!] <name> : Match the protocol defined in /etc/l7-protocols/name.pat\n"
  41         "--l7pkt              : Skip connection tracking and match individual packets\n",
  42
  43         IPTABLES_VERSION);
  44         fputc('\n', stdout);
  45 }
  46
  47 static struct option opts[] = {
  48         { .name = "l7proto", .has_arg = 1, .flag = 0, .val = '1' },
  49         { .name = "l7dir",   .has_arg = 1, .flag = 0, .val = '2' },
  50         { .name = "l7pkt",   .has_arg = 0, .flag = 0, .val = '3' },
  51         { .name = 0 }
  52 };
  53
  54 /* reads filename, puts protocol info into layer7_protocol_info, number of protocols to numprotos */
  55 int parse_protocol_file(char * filename, const unsigned char * protoname, struct ipt_layer7_info *info)
  56 {
  57         FILE * f;
  58         char * line = NULL;
  59         size_t len = 0;
  60
  61         enum { protocol, pattern, done } datatype = protocol;
  62
  63         f = fopen(filename, "r");
  64
  65         if(!f)
  66                 return 0;
  67
  68         while(getline(&line, &len, f) != -1)
  69         {
  70                 if(strlen(line) < 2 || line[0] == '#')
  71                         continue;
  72
  73                 /* strip the pesky newline... */
  74                 if(line[strlen(line) - 1] == '\n')
  75                         line[strlen(line) - 1] = '\0';
  76
  77                 if(datatype == protocol)
  78                 {
  79                         /* Ignore everything on the line beginning with the
  80                         first space or tab . For instance, this allows the
  81                         protocol line in http.pat to be "http " (or
  82                         "http I am so cool") instead of just "http". */
  83                         if(strchr(line, ' ')){
  84                                 char * space = strchr(line, ' ');
  85                                 space[0] = '\0';
  86                         }
  87                         if(strchr(line, '\t')){
  88                                 char * space = strchr(line, '\t');
  89                                 space[0] = '\0';
  90                         }
  91
  92                         /* sanity check.  First non-comment non-blank
  93                         line must be the same as the file name. */
  94                         if(strcmp(line, protoname))
  95                                 exit_error(OTHER_PROBLEM,
  96                                         "Protocol name (%s) doesn't match file name (%s).  Bailing out\n",
  97                                         line, filename);
  98
  99                         if(strlen(line) >= MAX_PROTOCOL_LEN)
 100                                  exit_error(PARAMETER_PROBLEM,
 101                                         "Protocol name in %s too long!", filename);
 102                         strncpy(info->protocol, line, MAX_PROTOCOL_LEN);
 103
 104                         datatype = pattern;
 105                 }
 106                 else if(datatype == pattern)
 107                 {
 108                         if(strlen(line) >= MAX_PATTERN_LEN)
 109                                  exit_error(PARAMETER_PROBLEM, "Pattern in %s too long!", filename);
 110                         strncpy(info->pattern, line, MAX_PATTERN_LEN);
 111
 112                         datatype = done;
 113                         break;
 114                 }
 115                 else
 116                         exit_error(OTHER_PROBLEM, "Internal error");
 117         }
 118
 119         if(datatype != done)
 120                 exit_error(OTHER_PROBLEM, "Failed to get all needed data from %s", filename);
 121
 122         if(line) free(line);
 123         fclose(f);
 124
 125         return 1;
 126
 127 /*
 128         fprintf(stderr, "protocol: %s\npattern: %s\n\n",
 129                         info->protocol,
 130                         info->pattern);
 131 */
 132 }
 133
 134 static int hex2dec(char c)
 135 {
 136         switch (c)
 137         {
 138                 case '0' ... '9':
 139                         return c - '0';
 140                 case 'a' ... 'f':
 141                         return c - 'a' + 10;
 142                 case 'A' ... 'F':
 143                         return c - 'A' + 10;
 144                 default:
 145                         exit_error(OTHER_PROBLEM, "hex2dec: bad value!\n");
 146                         return 0;
 147         }
 148 }
 149
 150 /* takes a string with \xHH escapes and returns one with the characters
 151 they stand for */
 152 static char * pre_process(char * s)
 153 {
 154         char * result = malloc(strlen(s) + 1);
 155         int sindex = 0, rindex = 0;
 156         while( sindex < strlen(s) )
 157         {
 158             if( sindex + 3 < strlen(s) &&
 159                 s[sindex] == '\\' && s[sindex+1] == 'x' &&
 160                 isxdigit(s[sindex + 2]) && isxdigit(s[sindex + 3]) )
 161                 {
 162                         /* carefully remember to call tolower here... */
 163                         result[rindex] = tolower( hex2dec(s[sindex + 2])*16 +
 164                                                   hex2dec(s[sindex + 3] ) );
 165
 166                         switch ( result[rindex] )
 167                         {
 168                         case 0x24:
 169                         case 0x28:
 170                         case 0x29:
 171                         case 0x2a:
 172                         case 0x2b:
 173                         case 0x2e:
 174                         case 0x3f:
 175                         case 0x5b:
 176                         case 0x5c:
 177                         case 0x5d:
 178                         case 0x5e:
 179                         case 0x7c:
 180                                 fprintf(stderr,
 181                                         "Warning: layer7 regexp contains a control character, %c, in hex (\\x%c%c).\n"
 182                                         "I recommend that you write this as %c or \\%c, depending on what you meant.\n",
 183                                         result[rindex], s[sindex + 2], s[sindex + 3], result[rindex], result[rindex]);
 184                                 break;
 185                         case 0x00:
 186                                 fprintf(stderr,
 187                                         "Warning: null (\\x00) in layer7 regexp.  A null terminates the regexp string!\n");
 188                                 break;
 189                         default:
 190                                 break;
 191                         }
 192
 193
 194                         sindex += 3; /* 4 total */
 195                 }
 196                 else
 197                         result[rindex] = tolower(s[sindex]);
 198
 199                 sindex++;
 200                 rindex++;
 201         }
 202         result[rindex] = '\0';
 203
 204         return result;
 205 }
 206
 207 #define MAX_SUBDIRS 128
 208 char ** readl7dir(char * dirname)
 209 {
 210         DIR             * scratchdir;
 211         struct dirent   ** namelist;
 212         char ** subdirs = malloc(MAX_SUBDIRS * sizeof(char *));
 213
 214         int n, d = 1;
 215         subdirs[0] = "";
 216
 217         n = scandir(dirname, &namelist, 0, alphasort);
 218
 219         if (n < 0)
 220         {
 221             perror("scandir");
 222             exit_error(OTHER_PROBLEM, "Couldn't open %s\n", dirname);
 223         }
 224         else
 225         {
 226                 while(n--)
 227                 {
 228                         char fulldirname[MAX_FN_LEN];
 229
 230                         snprintf(fulldirname, MAX_FN_LEN, "%s/%s", dirname, namelist[n]->d_name);
 231
 232                         if((scratchdir = opendir(fulldirname)) != NULL)
 233                         {
 234                                 closedir(scratchdir);
 235
 236                                 if(!strcmp(namelist[n]->d_name, ".") ||
 237                                    !strcmp(namelist[n]->d_name, ".."))
 238                                         /* do nothing */ ;
 239                                 else
 240                                 {
 241                                         subdirs[d] = malloc(strlen(namelist[n]->d_name) + 1);
 242                                         strcpy(subdirs[d], namelist[n]->d_name);
 243                                         d++;
 244                                         if(d >= MAX_SUBDIRS - 1)
 245                                         {
 246                                                 fprintf(stderr,
 247                                                   "Too many subdirectories, skipping the rest!\n");
 248                                                 break;
 249                                         }
 250                                 }
 251                         }
 252                         free(namelist[n]);
 253                 }
 254                 free(namelist);
 255         }
 256
 257         subdirs[d] = NULL;
 258
 259         return subdirs;
 260 }
 261
 262 static void
 263 parse_layer7_protocol(const unsigned char *s, struct ipt_layer7_info *info)
 264 {
 265         char filename[MAX_FN_LEN];
 266         char * dir = NULL;
 267         char ** subdirs;
 268         int n = 0, done = 0;
 269
 270         if(strlen(l7dir) > 0)
 271                 dir = l7dir;
 272         else
 273                 dir = "/etc/l7-protocols";
 274
 275         subdirs = readl7dir(dir);
 276
 277         while(subdirs[n] != NULL)
 278         {
 279                 int c = snprintf(filename, MAX_FN_LEN, "%s/%s/%s.pat", dir, subdirs[n], s);
 280
 281                 //fprintf(stderr, "Trying to find pattern in %s ... ", filename);
 282
 283                 if(c > MAX_FN_LEN)
 284                 {
 285                         exit_error(OTHER_PROBLEM,
 286                                 "Filename beginning with %s is too long!\n", filename);
 287                 }
 288
 289                 /* read in the pattern from the file */
 290                 if(parse_protocol_file(filename, s, info))
 291                 {
 292                         //fprintf(stderr, "found\n");
 293                         done = 1;
 294                         break;
 295                 }
 296
 297                 //fprintf(stderr, "not found\n");
 298
 299                 n++;
 300         }
 301
 302         if(!done)
 303                 exit_error(OTHER_PROBLEM,
 304                         "Couldn't find a pattern definition file for %s.\n", s);
 305
 306         /* process \xHH escapes and tolower everything. (our regex lib has no
 307         case insensitivity option.) */
 308         strncpy(info->pattern, pre_process(info->pattern), MAX_PATTERN_LEN);
 309 }
 310
 311 /* Function which parses command options; returns true if it ate an option */
 312 static int parse(int c, char **argv, int invert, unsigned int *flags,
 313       const struct ipt_entry *entry, unsigned int *nfcache,
 314       struct ipt_entry_match **match)
 315 {
 316         struct ipt_layer7_info *layer7info =
 317                 (struct ipt_layer7_info *)(*match)->data;
 318
 319         switch (c) {
 320         case '1':
 321                 check_inverse(optarg, &invert, &optind, 0);
 322                 parse_layer7_protocol(argv[optind-1], layer7info);
 323                 if (invert)
 324                         layer7info->invert = 1;
 325                 *flags = 1;
 326                 break;
 327
 328         case '2':
 329                 /* not going to use this, but maybe we need to strip a ! anyway (?) */
 330                 check_inverse(optarg, &invert, &optind, 0);
 331
 332                 if(strlen(argv[optind-1]) >= MAX_FN_LEN)
 333                         exit_error(PARAMETER_PROBLEM, "directory name too long\n");
 334
 335                 strncpy(l7dir, argv[optind-1], MAX_FN_LEN);
 336
 337                 *flags = 1;
 338                 break;
 339
 340         case '3':
 341                 layer7info->pkt = 1;
 342                 break;
 343
 344         default:
 345                 return 0;
 346         }
 347
 348         return 1;
 349 }
 350
 351 /* Final check; must have specified --l7proto */
 352 static void final_check(unsigned int flags)
 353 {
 354         if (!flags)
 355                 exit_error(PARAMETER_PROBLEM,
 356                            "LAYER7 match: You must specify `--l7proto'");
 357 }
 358
 359 static void print_protocol(char s[], int invert, int numeric)
 360 {
 361         fputs("l7proto ", stdout);
 362         if (invert) fputc('!', stdout);
 363         printf("%s ", s);
 364 }
 365
 366 /* Prints out the matchinfo. */
 367 static void print(const struct ipt_ip *ip,
 368       const struct ipt_entry_match *match,
 369       int numeric)
 370 {
 371         printf("LAYER7 ");
 372
 373         print_protocol(((struct ipt_layer7_info *)match->data)->protocol,
 374                   ((struct ipt_layer7_info *)match->data)->invert, numeric);
 375
 376         if (((struct ipt_layer7_info *)match->data)->pkt)
 377                 printf("l7pkt ");
 378 }
 379 /* Saves the union ipt_matchinfo in parsable form to stdout. */
 380 static void save(const struct ipt_ip *ip, const struct ipt_entry_match *match)
 381 {
 382         const struct ipt_layer7_info *info =
 383             (const struct ipt_layer7_info*) match->data;
 384
 385         printf("--l7proto %s%s ", (info->invert)   ? "! ": "", info->protocol);
 386 }
 387
 388 static struct iptables_match layer7 = {
 389     .name          = "layer7",
 390     .version       = IPTABLES_VERSION,
 391     .size          = IPT_ALIGN(sizeof(struct ipt_layer7_info)),
 392     .userspacesize = IPT_ALIGN(sizeof(struct ipt_layer7_info)),
 393     .help          = &help,
 394     .parse         = &parse,
 395     .final_check   = &final_check,
 396     .print         = &print,
 397     .save          = &save,
 398     .extra_opts    = opts
 399 };
 400
 401 void _init(void)
 402 {
 403         register_match(&layer7);
 404 }