extensions/libip6t_tcp.c

   1 /* Shared library add-on to iptables to add TCP support. */
   2 #include <stdio.h>
   3 #include <netdb.h>
   4 #include <string.h>
   5 #include <stdlib.h>
   6 #include <getopt.h>
   7 #include <ip6tables.h>
   8 #include <linux/netfilter_ipv6/ip6_tables.h>
   9
  10 /* Function which prints out usage message. */
  11 static void
  12 help(void)
  13 {
  14         printf(
  15 "TCP v%s options:\n"
  16 " --tcp-flags [!] mask comp     match when TCP flags & mask == comp\n"
  17 "                               (Flags: SYN ACK FIN RST URG PSH ALL NONE)\n"
  18 "[!] --syn                      match when only SYN flag set\n"
  19 "                               (equivalent to --tcp-flags SYN,RST,ACK SYN)\n"
  20 " --source-port [!] port[:port]\n"
  21 " --sport ...\n"
  22 "                               match source port(s)\n"
  23 " --destination-port [!] port[:port]\n"
  24 " --dport ...\n"
  25 "                               match destination port(s)\n"
  26 " --tcp-option [!] number       match if TCP option set\n\n",
  27 IPTABLES_VERSION);
  28 }
  29
  30 static struct option opts[] = {
  31         { "source-port", 1, 0, '1' },
  32         { "sport", 1, 0, '1' }, /* synonym */
  33         { "destination-port", 1, 0, '2' },
  34         { "dport", 1, 0, '2' }, /* synonym */
  35         { "syn", 0, 0, '3' },
  36         { "tcp-flags", 1, 0, '4' },
  37         { "tcp-option", 1, 0, '5' },
  38         {0}
  39 };
  40
  41 static void
  42 parse_tcp_ports(const char *portstring, u_int16_t *ports)
  43 {
  44         char *buffer;
  45         char *cp;
  46
  47         buffer = strdup(portstring);
  48         if ((cp = strchr(buffer, ':')) == NULL)
  49                 ports[0] = ports[1] = parse_port(buffer, "tcp");
  50         else {
  51                 *cp = '\0';
  52                 cp++;
  53
  54                 ports[0] = buffer[0] ? parse_port(buffer, "tcp") : 0;
  55                 ports[1] = cp[0] ? parse_port(cp, "tcp") : 0xFFFF;
  56
  57                 if (ports[0] > ports[1])
  58                         exit_error(PARAMETER_PROBLEM,
  59                                    "invalid portrange (min > max)");
  60         }
  61         free(buffer);
  62 }
  63
  64 struct tcp_flag_names {
  65         const char *name;
  66         unsigned int flag;
  67 };
  68
  69 static struct tcp_flag_names tcp_flag_names[]
  70 = { { "FIN", 0x01 },
  71     { "SYN", 0x02 },
  72     { "RST", 0x04 },
  73     { "PSH", 0x08 },
  74     { "ACK", 0x10 },
  75     { "URG", 0x20 },
  76     { "ALL", 0x3F },
  77     { "NONE", 0 },
  78 };
  79
  80 static unsigned int
  81 parse_tcp_flag(const char *flags)
  82 {
  83         unsigned int ret = 0;
  84         char *ptr;
  85         char *buffer;
  86
  87         buffer = strdup(flags);
  88
  89         for (ptr = strtok(buffer, ","); ptr; ptr = strtok(NULL, ",")) {
  90                 unsigned int i;
  91                 for (i = 0;
  92                      i < sizeof(tcp_flag_names)/sizeof(struct tcp_flag_names);
  93                      i++) {
  94                         if (strcasecmp(tcp_flag_names[i].name, ptr) == 0) {
  95                                 ret |= tcp_flag_names[i].flag;
  96                                 break;
  97                         }
  98                 }
  99                 if (i == sizeof(tcp_flag_names)/sizeof(struct tcp_flag_names))
 100                         exit_error(PARAMETER_PROBLEM,
 101                                    "Unknown TCP flag `%s'", ptr);
 102                 }
 103
 104         free(buffer);
 105         return ret;
 106 }
 107
 108 static void
 109 parse_tcp_flags(struct ip6t_tcp *tcpinfo,
 110                 const char *mask,
 111                 const char *cmp,
 112                 int invert)
 113 {
 114         tcpinfo->flg_mask = parse_tcp_flag(mask);
 115         tcpinfo->flg_cmp = parse_tcp_flag(cmp);
 116
 117         if (invert)
 118                 tcpinfo->invflags |= IP6T_TCP_INV_FLAGS;
 119 }
 120
 121 static void
 122 parse_tcp_option(const char *option, u_int8_t *result)
 123 {
 124         unsigned int ret;
 125
 126         if (string_to_number(option, 1, 255, &ret) == -1)
 127                 exit_error(PARAMETER_PROBLEM, "Bad TCP option `%s'", option);
 128
 129         *result = (u_int8_t)ret;
 130 }
 131
 132 /* Initialize the match. */
 133 static void
 134 init(struct ip6t_entry_match *m, unsigned int *nfcache)
 135 {
 136         struct ip6t_tcp *tcpinfo = (struct ip6t_tcp *)m->data;
 137
 138         tcpinfo->spts[1] = tcpinfo->dpts[1] = 0xFFFF;
 139 }
 140
 141 #define TCP_SRC_PORTS 0x01
 142 #define TCP_DST_PORTS 0x02
 143 #define TCP_FLAGS 0x04
 144 #define TCP_OPTION      0x08
 145
 146 /* Function which parses command options; returns true if it
 147    ate an option. */
 148 static int
 149 parse(int c, char **argv, int invert, unsigned int *flags,
 150       const struct ip6t_entry *entry,
 151       unsigned int *nfcache,
 152       struct ip6t_entry_match **match)
 153 {
 154         struct ip6t_tcp *tcpinfo = (struct ip6t_tcp *)(*match)->data;
 155
 156         switch (c) {
 157         case '1':
 158                 if (*flags & TCP_SRC_PORTS)
 159                         exit_error(PARAMETER_PROBLEM,
 160                                    "Only one `--source-port' allowed");
 161                 check_inverse(optarg, &invert, &optind, 0);
 162                 parse_tcp_ports(argv[optind-1], tcpinfo->spts);
 163                 if (invert)
 164                         tcpinfo->invflags |= IP6T_TCP_INV_SRCPT;
 165                 *flags |= TCP_SRC_PORTS;
 166                 break;
 167
 168         case '2':
 169                 if (*flags & TCP_DST_PORTS)
 170                         exit_error(PARAMETER_PROBLEM,
 171                                    "Only one `--destination-port' allowed");
 172                 check_inverse(optarg, &invert, &optind, 0);
 173                 parse_tcp_ports(argv[optind-1], tcpinfo->dpts);
 174                 if (invert)
 175                         tcpinfo->invflags |= IP6T_TCP_INV_DSTPT;
 176                 *flags |= TCP_DST_PORTS;
 177                 break;
 178
 179         case '3':
 180                 if (*flags & TCP_FLAGS)
 181                         exit_error(PARAMETER_PROBLEM,
 182                                    "Only one of `--syn' or `--tcp-flags' "
 183                                    " allowed");
 184                 parse_tcp_flags(tcpinfo, "SYN,RST,ACK", "SYN", invert);
 185                 *flags |= TCP_FLAGS;
 186                 break;
 187
 188         case '4':
 189                 if (*flags & TCP_FLAGS)
 190                         exit_error(PARAMETER_PROBLEM,
 191                                    "Only one of `--syn' or `--tcp-flags' "
 192                                    " allowed");
 193                 check_inverse(optarg, &invert, &optind, 0);
 194
 195                 if (!argv[optind]
 196                     || argv[optind][0] == '-' || argv[optind][0] == '!')
 197                         exit_error(PARAMETER_PROBLEM,
 198                                    "--tcp-flags requires two args.");
 199
 200                 parse_tcp_flags(tcpinfo, argv[optind-1], argv[optind],
 201                                 invert);
 202                 optind++;
 203                 *flags |= TCP_FLAGS;
 204                 break;
 205
 206         case '5':
 207                 if (*flags & TCP_OPTION)
 208                         exit_error(PARAMETER_PROBLEM,
 209                                    "Only one `--tcp-option' allowed");
 210                 check_inverse(optarg, &invert, &optind, 0);
 211                 parse_tcp_option(argv[optind-1], &tcpinfo->option);
 212                 if (invert)
 213                         tcpinfo->invflags |= IP6T_TCP_INV_OPTION;
 214                 *flags |= TCP_OPTION;
 215                 break;
 216
 217         default:
 218                 return 0;
 219         }
 220
 221         return 1;
 222 }
 223
 224 /* Final check; we don't care. */
 225 static void
 226 final_check(unsigned int flags)
 227 {
 228 }
 229
 230 static char *
 231 port_to_service(int port)
 232 {
 233         struct servent *service;
 234
 235         if ((service = getservbyport(htons(port), "tcp")))
 236                 return service->s_name;
 237
 238         return NULL;
 239 }
 240
 241 static void
 242 print_port(u_int16_t port, int numeric)
 243 {
 244         char *service;
 245
 246         if (numeric || (service = port_to_service(port)) == NULL)
 247                 printf("%u", port);
 248         else
 249                 printf("%s", service);
 250 }
 251
 252 static void
 253 print_ports(const char *name, u_int16_t min, u_int16_t max,
 254             int invert, int numeric)
 255 {
 256         const char *inv = invert ? "!" : "";
 257
 258         if (min != 0 || max != 0xFFFF || invert) {
 259                 printf("%s", name);
 260                 if (min == max) {
 261                         printf(":%s", inv);
 262                         print_port(min, numeric);
 263                 } else {
 264                         printf("s:%s", inv);
 265                         print_port(min, numeric);
 266                         printf(":");
 267                         print_port(max, numeric);
 268                 }
 269                 printf(" ");
 270         }
 271 }
 272
 273 static void
 274 print_option(u_int8_t option, int invert, int numeric)
 275 {
 276         if (option || invert)
 277                 printf("option=%s%u ", invert ? "!" : "", option);
 278 }
 279
 280 static void
 281 print_tcpf(u_int8_t flags)
 282 {
 283         int have_flag = 0;
 284
 285         while (flags) {
 286                 unsigned int i;
 287
 288                 for (i = 0; (flags & tcp_flag_names[i].flag) == 0; i++);
 289
 290                 if (have_flag)
 291                         printf(",");
 292                 printf("%s", tcp_flag_names[i].name);
 293                 have_flag = 1;
 294
 295                 flags &= ~tcp_flag_names[i].flag;
 296         }
 297
 298         if (!have_flag)
 299                 printf("NONE");
 300 }
 301
 302 static void
 303 print_flags(u_int8_t mask, u_int8_t cmp, int invert, int numeric)
 304 {
 305         if (mask || invert) {
 306                 printf("flags:%s", invert ? "!" : "");
 307                 if (numeric)
 308                         printf("0x%02X/0x%02X ", mask, cmp);
 309                 else {
 310                         print_tcpf(mask);
 311                         printf("/");
 312                         print_tcpf(cmp);
 313                         printf(" ");
 314                 }
 315         }
 316 }
 317
 318 /* Prints out the union ipt_matchinfo. */
 319 static void
 320 print(const struct ip6t_ip6 *ip,
 321       const struct ip6t_entry_match *match, int numeric)
 322 {
 323         const struct ip6t_tcp *tcp = (struct ip6t_tcp *)match->data;
 324
 325         printf("tcp ");
 326         print_ports("spt", tcp->spts[0], tcp->spts[1],
 327                     tcp->invflags & IP6T_TCP_INV_SRCPT,
 328                     numeric);
 329         print_ports("dpt", tcp->dpts[0], tcp->dpts[1],
 330                     tcp->invflags & IP6T_TCP_INV_DSTPT,
 331                     numeric);
 332         print_option(tcp->option,
 333                      tcp->invflags & IP6T_TCP_INV_OPTION,
 334                      numeric);
 335         print_flags(tcp->flg_mask, tcp->flg_cmp,
 336                     tcp->invflags & IP6T_TCP_INV_FLAGS,
 337                     numeric);
 338         if (tcp->invflags & ~IP6T_TCP_INV_MASK)
 339                 printf("Unknown invflags: 0x%X ",
 340                        tcp->invflags & ~IP6T_TCP_INV_MASK);
 341 }
 342
 343 /* Saves the union ipt_matchinfo in parsable form to stdout. */
 344 static void save(const struct ip6t_ip6 *ip, const struct ip6t_entry_match *match)
 345 {
 346         const struct ip6t_tcp *tcpinfo = (struct ip6t_tcp *)match->data;
 347
 348         if (tcpinfo->spts[0] != 0
 349             || tcpinfo->spts[1] != 0xFFFF) {
 350                 if (tcpinfo->invflags & IP6T_TCP_INV_SRCPT)
 351                         printf("! ");
 352                 if (tcpinfo->spts[0]
 353                     != tcpinfo->spts[1])
 354                         printf("--sport %u:%u ",
 355                                tcpinfo->spts[0],
 356                                tcpinfo->spts[1]);
 357                 else
 358                         printf("--sport %u ",
 359                                tcpinfo->spts[0]);
 360         }
 361
 362         if (tcpinfo->dpts[0] != 0
 363             || tcpinfo->dpts[1] != 0xFFFF) {
 364                 if (tcpinfo->invflags & IP6T_TCP_INV_DSTPT)
 365                         printf("! ");
 366                 if (tcpinfo->dpts[0]
 367                     != tcpinfo->dpts[1])
 368                         printf("--dport %u:%u ",
 369                                tcpinfo->dpts[0],
 370                                tcpinfo->dpts[1]);
 371                 else
 372                         printf("--dport %u ",
 373                                tcpinfo->dpts[0]);
 374         }
 375
 376         if (tcpinfo->option
 377             || (tcpinfo->invflags & IP6T_TCP_INV_OPTION)) {
 378                 if (tcpinfo->invflags & IP6T_TCP_INV_OPTION)
 379                         printf("! ");
 380                 printf("--tcp-option %u ", tcpinfo->option);
 381         }
 382
 383         if (tcpinfo->flg_mask
 384             || (tcpinfo->invflags & IP6T_TCP_INV_FLAGS)) {
 385                 if (tcpinfo->invflags & IP6T_TCP_INV_FLAGS)
 386                         printf("! ");
 387
 388                 printf("--tcp-flags ");
 389                 if (tcpinfo->flg_mask != 0xFF) {
 390                         print_tcpf(tcpinfo->flg_mask);
 391                 }
 392                 printf(" ");
 393                 print_tcpf(tcpinfo->flg_cmp);
 394                 printf(" ");
 395         }
 396 }
 397
 398 static struct ip6tables_match tcp = {
 399         .name           = "tcp",
 400         .version        = IPTABLES_VERSION,
 401         .size           = IP6T_ALIGN(sizeof(struct ip6t_tcp)),
 402         .userspacesize  = IP6T_ALIGN(sizeof(struct ip6t_tcp)),
 403         .help           = &help,
 404         .init           = &init,
 405         .parse          = &parse,
 406         .final_check    = &final_check,
 407         .print          = &print,
 408         .save           = &save,
 409         .extra_opts     = opts,
 410 };
 411
 412 void
 413 _init(void)
 414 {
 415         register_match6(&tcp);
 416 }