src/libiptc/libip4tc.c

   1 /* Library which manipulates firewall rules.  Version 0.1. */
   2
   3 /* Architecture of firewall rules is as follows:
   4  *
   5  * Chains go INPUT, FORWARD, OUTPUT then user chains.
   6  * Each user chain starts with an ERROR node.
   7  * Every chain ends with an unconditional jump: a RETURN for user chains,
   8  * and a POLICY for built-ins.
   9  */
  10
  11 /* (C)1999 Paul ``Rusty'' Russell - Placed under the GNU GPL (See
  12    COPYING for details). */
  13
  14 #include <assert.h>
  15 #include <string.h>
  16 #include <errno.h>
  17 #include <stdlib.h>
  18 #include <stdio.h>
  19 #include <unistd.h>
  20
  21 #ifdef DEBUG_CONNTRACK
  22 #define inline
  23 #endif
  24
  25 #if !defined(__GLIBC__) || (__GLIBC__ < 2)
  26 typedef unsigned int socklen_t;
  27 #endif
  28
  29 #include "libiptc/libiptc.h"
  30
  31 #define IP_VERSION      4
  32 #define IP_OFFSET       0x1FFF
  33
  34 #define HOOK_PRE_ROUTING        NF_IP_PRE_ROUTING
  35 #define HOOK_LOCAL_IN           NF_IP_LOCAL_IN
  36 #define HOOK_FORWARD            NF_IP_FORWARD
  37 #define HOOK_LOCAL_OUT          NF_IP_LOCAL_OUT
  38 #define HOOK_POST_ROUTING       NF_IP_POST_ROUTING
  39 #ifdef NF_IP_DROPPING
  40 #define HOOK_DROPPING           NF_IP_DROPPING
  41 #endif
  42
  43 #define STRUCT_ENTRY_TARGET     struct ipt_entry_target
  44 #define STRUCT_ENTRY            struct ipt_entry
  45 #define STRUCT_ENTRY_MATCH      struct ipt_entry_match
  46 #define STRUCT_GETINFO          struct ipt_getinfo
  47 #define STRUCT_GET_ENTRIES      struct ipt_get_entries
  48 #define STRUCT_COUNTERS         struct ipt_counters
  49 #define STRUCT_COUNTERS_INFO    struct ipt_counters_info
  50 #define STRUCT_STANDARD_TARGET  struct ipt_standard_target
  51 #define STRUCT_REPLACE          struct ipt_replace
  52
  53 #define STRUCT_TC_HANDLE        struct iptc_handle
  54 #define TC_HANDLE_T             iptc_handle_t
  55
  56 #define ENTRY_ITERATE           IPT_ENTRY_ITERATE
  57 #define TABLE_MAXNAMELEN        IPT_TABLE_MAXNAMELEN
  58 #define FUNCTION_MAXNAMELEN     IPT_FUNCTION_MAXNAMELEN
  59
  60 #define GET_TARGET              ipt_get_target
  61
  62 #define ERROR_TARGET            IPT_ERROR_TARGET
  63 #define NUMHOOKS                NF_IP_NUMHOOKS
  64
  65 #define IPT_CHAINLABEL          ipt_chainlabel
  66
  67 #define TC_DUMP_ENTRIES         dump_entries
  68 #define TC_IS_CHAIN             iptc_is_chain
  69 #define TC_FIRST_CHAIN          iptc_first_chain
  70 #define TC_NEXT_CHAIN           iptc_next_chain
  71 #define TC_FIRST_RULE           iptc_first_rule
  72 #define TC_NEXT_RULE            iptc_next_rule
  73 #define TC_GET_TARGET           iptc_get_target
  74 #define TC_BUILTIN              iptc_builtin
  75 #define TC_GET_POLICY           iptc_get_policy
  76 #define TC_INSERT_ENTRY         iptc_insert_entry
  77 #define TC_REPLACE_ENTRY        iptc_replace_entry
  78 #define TC_APPEND_ENTRY         iptc_append_entry
  79 #define TC_DELETE_ENTRY         iptc_delete_entry
  80 #define TC_DELETE_NUM_ENTRY     iptc_delete_num_entry
  81 #define TC_CHECK_PACKET         iptc_check_packet
  82 #define TC_FLUSH_ENTRIES        iptc_flush_entries
  83 #define TC_ZERO_ENTRIES         iptc_zero_entries
  84 #define TC_READ_COUNTER         iptc_read_counter
  85 #define TC_ZERO_COUNTER         iptc_zero_counter
  86 #define TC_SET_COUNTER          iptc_set_counter
  87 #define TC_CREATE_CHAIN         iptc_create_chain
  88 #define TC_GET_REFERENCES       iptc_get_references
  89 #define TC_DELETE_CHAIN         iptc_delete_chain
  90 #define TC_RENAME_CHAIN         iptc_rename_chain
  91 #define TC_SET_POLICY           iptc_set_policy
  92 #define TC_GET_RAW_SOCKET       iptc_get_raw_socket
  93 #define TC_INIT                 iptc_init
  94 #define TC_FREE                 iptc_free
  95 #define TC_COMMIT               iptc_commit
  96 #define TC_STRERROR             iptc_strerror
  97 #define TC_NUM_RULES            iptc_num_rules
  98 #define TC_GET_RULE             iptc_get_rule
  99
 100 #define TC_AF                   AF_INET
 101 #define TC_IPPROTO              IPPROTO_IP
 102
 103 #define SO_SET_REPLACE          IPT_SO_SET_REPLACE
 104 #define SO_SET_ADD_COUNTERS     IPT_SO_SET_ADD_COUNTERS
 105 #define SO_GET_INFO             IPT_SO_GET_INFO
 106 #define SO_GET_ENTRIES          IPT_SO_GET_ENTRIES
 107 #define SO_GET_VERSION          IPT_SO_GET_VERSION
 108
 109 #define STANDARD_TARGET         IPT_STANDARD_TARGET
 110 #define LABEL_RETURN            IPTC_LABEL_RETURN
 111 #define LABEL_ACCEPT            IPTC_LABEL_ACCEPT
 112 #define LABEL_DROP              IPTC_LABEL_DROP
 113 #define LABEL_QUEUE             IPTC_LABEL_QUEUE
 114
 115 #define ALIGN                   IPT_ALIGN
 116 #define RETURN                  IPT_RETURN
 117
 118 #include "libiptc.c"
 119
 120 #define IP_PARTS_NATIVE(n)                      \
 121 (unsigned int)((n)>>24)&0xFF,                   \
 122 (unsigned int)((n)>>16)&0xFF,                   \
 123 (unsigned int)((n)>>8)&0xFF,                    \
 124 (unsigned int)((n)&0xFF)
 125
 126 #define IP_PARTS(n) IP_PARTS_NATIVE(ntohl(n))
 127
 128 int
 129 dump_entry(STRUCT_ENTRY *e, const TC_HANDLE_T handle)
 130 {
 131         size_t i;
 132         STRUCT_ENTRY_TARGET *t;
 133
 134         printf("Entry %u (%lu):\n", iptcb_entry2index(handle, e),
 135                iptcb_entry2offset(handle, e));
 136         printf("SRC IP: %u.%u.%u.%u/%u.%u.%u.%u\n",
 137                IP_PARTS(e->ip.src.s_addr),IP_PARTS(e->ip.smsk.s_addr));
 138         printf("DST IP: %u.%u.%u.%u/%u.%u.%u.%u\n",
 139                IP_PARTS(e->ip.dst.s_addr),IP_PARTS(e->ip.dmsk.s_addr));
 140         printf("Interface: `%s'/", e->ip.iniface);
 141         for (i = 0; i < IFNAMSIZ; i++)
 142                 printf("%c", e->ip.iniface_mask[i] ? 'X' : '.');
 143         printf("to `%s'/", e->ip.outiface);
 144         for (i = 0; i < IFNAMSIZ; i++)
 145                 printf("%c", e->ip.outiface_mask[i] ? 'X' : '.');
 146         printf("\nProtocol: %u\n", e->ip.proto);
 147         printf("Flags: %02X\n", e->ip.flags);
 148         printf("Invflags: %02X\n", e->ip.invflags);
 149         printf("Counters: %llu packets, %llu bytes\n",
 150                (unsigned long long)e->counters.pcnt, (unsigned long long)e->counters.bcnt);
 151         printf("Cache: %08X ", e->nfcache);
 152         if (e->nfcache & NFC_ALTERED) printf("ALTERED ");
 153         if (e->nfcache & NFC_UNKNOWN) printf("UNKNOWN ");
 154         printf("\n");
 155
 156         IPT_MATCH_ITERATE(e, print_match);
 157
 158         t = GET_TARGET(e);
 159         printf("Target name: `%s' [%u]\n", t->u.user.name, t->u.target_size);
 160         if (strcmp(t->u.user.name, STANDARD_TARGET) == 0) {
 161                 int pos = *(int *)t->data;
 162                 if (pos < 0)
 163                         printf("verdict=%s\n",
 164                                pos == -NF_ACCEPT-1 ? "NF_ACCEPT"
 165                                : pos == -NF_DROP-1 ? "NF_DROP"
 166                                : pos == -NF_QUEUE-1 ? "NF_QUEUE"
 167                                : pos == RETURN ? "RETURN"
 168                                : "UNKNOWN");
 169                 else
 170                         printf("verdict=%u\n", pos);
 171         } else if (strcmp(t->u.user.name, IPT_ERROR_TARGET) == 0)
 172                 printf("error=`%s'\n", t->data);
 173
 174         printf("\n");
 175         return 0;
 176 }
 177
 178 static unsigned char *
 179 is_same(const STRUCT_ENTRY *a, const STRUCT_ENTRY *b, unsigned char *matchmask)
 180 {
 181         unsigned int i;
 182         unsigned char *mptr;
 183
 184         /* Always compare head structures: ignore mask here. */
 185         if (a->ip.src.s_addr != b->ip.src.s_addr
 186             || a->ip.dst.s_addr != b->ip.dst.s_addr
 187             || a->ip.smsk.s_addr != b->ip.smsk.s_addr
 188             || a->ip.dmsk.s_addr != b->ip.dmsk.s_addr
 189             || a->ip.proto != b->ip.proto
 190             || a->ip.flags != b->ip.flags
 191             || a->ip.invflags != b->ip.invflags)
 192                 return NULL;
 193
 194         for (i = 0; i < IFNAMSIZ; i++) {
 195                 if (a->ip.iniface_mask[i] != b->ip.iniface_mask[i])
 196                         return NULL;
 197                 if ((a->ip.iniface[i] & a->ip.iniface_mask[i])
 198                     != (b->ip.iniface[i] & b->ip.iniface_mask[i]))
 199                         return NULL;
 200                 if (a->ip.outiface_mask[i] != b->ip.outiface_mask[i])
 201                         return NULL;
 202                 if ((a->ip.outiface[i] & a->ip.outiface_mask[i])
 203                     != (b->ip.outiface[i] & b->ip.outiface_mask[i]))
 204                         return NULL;
 205         }
 206
 207         if (a->nfcache != b->nfcache
 208             || a->target_offset != b->target_offset
 209             || a->next_offset != b->next_offset)
 210                 return NULL;
 211
 212         mptr = matchmask + sizeof(STRUCT_ENTRY);
 213         if (IPT_MATCH_ITERATE(a, match_different, a->elems, b->elems, &mptr))
 214                 return NULL;
 215         mptr += IPT_ALIGN(sizeof(struct ipt_entry_target));
 216
 217         return mptr;
 218 }
 219
 220 #if 0
 221 /***************************** DEBUGGING ********************************/
 222 static inline int
 223 unconditional(const struct ipt_ip *ip)
 224 {
 225         unsigned int i;
 226
 227         for (i = 0; i < sizeof(*ip)/sizeof(u_int32_t); i++)
 228                 if (((u_int32_t *)ip)[i])
 229                         return 0;
 230
 231         return 1;
 232 }
 233
 234 static inline int
 235 check_match(const STRUCT_ENTRY_MATCH *m, unsigned int *off)
 236 {
 237         assert(m->u.match_size >= sizeof(STRUCT_ENTRY_MATCH));
 238         assert(ALIGN(m->u.match_size) == m->u.match_size);
 239
 240         (*off) += m->u.match_size;
 241         return 0;
 242 }
 243
 244 static inline int
 245 check_entry(const STRUCT_ENTRY *e, unsigned int *i, unsigned int *off,
 246             unsigned int user_offset, int *was_return,
 247             TC_HANDLE_T h)
 248 {
 249         unsigned int toff;
 250         STRUCT_STANDARD_TARGET *t;
 251
 252         assert(e->target_offset >= sizeof(STRUCT_ENTRY));
 253         assert(e->next_offset >= e->target_offset
 254                + sizeof(STRUCT_ENTRY_TARGET));
 255         toff = sizeof(STRUCT_ENTRY);
 256         IPT_MATCH_ITERATE(e, check_match, &toff);
 257
 258         assert(toff == e->target_offset);
 259
 260         t = (STRUCT_STANDARD_TARGET *)
 261                 GET_TARGET((STRUCT_ENTRY *)e);
 262         /* next_offset will have to be multiple of entry alignment. */
 263         assert(e->next_offset == ALIGN(e->next_offset));
 264         assert(e->target_offset == ALIGN(e->target_offset));
 265         assert(t->target.u.target_size == ALIGN(t->target.u.target_size));
 266         assert(!TC_IS_CHAIN(t->target.u.user.name, h));
 267
 268         if (strcmp(t->target.u.user.name, STANDARD_TARGET) == 0) {
 269                 assert(t->target.u.target_size
 270                        == ALIGN(sizeof(STRUCT_STANDARD_TARGET)));
 271
 272                 assert(t->verdict == -NF_DROP-1
 273                        || t->verdict == -NF_ACCEPT-1
 274                        || t->verdict == RETURN
 275                        || t->verdict < (int)h->entries->size);
 276
 277                 if (t->verdict >= 0) {
 278                         STRUCT_ENTRY *te = get_entry(h, t->verdict);
 279                         int idx;
 280
 281                         idx = iptcb_entry2index(h, te);
 282                         assert(strcmp(GET_TARGET(te)->u.user.name,
 283                                       IPT_ERROR_TARGET)
 284                                != 0);
 285                         assert(te != e);
 286
 287                         /* Prior node must be error node, or this node. */
 288                         assert(t->verdict == iptcb_entry2offset(h, e)+e->next_offset
 289                                || strcmp(GET_TARGET(index2entry(h, idx-1))
 290                                          ->u.user.name, IPT_ERROR_TARGET)
 291                                == 0);
 292                 }
 293
 294                 if (t->verdict == RETURN
 295                     && unconditional(&e->ip)
 296                     && e->target_offset == sizeof(*e))
 297                         *was_return = 1;
 298                 else
 299                         *was_return = 0;
 300         } else if (strcmp(t->target.u.user.name, IPT_ERROR_TARGET) == 0) {
 301                 assert(t->target.u.target_size
 302                        == ALIGN(sizeof(struct ipt_error_target)));
 303
 304                 /* If this is in user area, previous must have been return */
 305                 if (*off > user_offset)
 306                         assert(*was_return);
 307
 308                 *was_return = 0;
 309         }
 310         else *was_return = 0;
 311
 312         if (*off == user_offset)
 313                 assert(strcmp(t->target.u.user.name, IPT_ERROR_TARGET) == 0);
 314
 315         (*off) += e->next_offset;
 316         (*i)++;
 317         return 0;
 318 }
 319
 320 #ifdef IPTC_DEBUG
 321 /* Do every conceivable sanity check on the handle */
 322 static void
 323 do_check(TC_HANDLE_T h, unsigned int line)
 324 {
 325         unsigned int i, n;
 326         unsigned int user_offset; /* Offset of first user chain */
 327         int was_return;
 328
 329         assert(h->changed == 0 || h->changed == 1);
 330         if (strcmp(h->info.name, "filter") == 0) {
 331                 assert(h->info.valid_hooks
 332                        == (1 << NF_IP_LOCAL_IN
 333                            | 1 << NF_IP_FORWARD
 334                            | 1 << NF_IP_LOCAL_OUT));
 335
 336                 /* Hooks should be first three */
 337                 assert(h->info.hook_entry[NF_IP_LOCAL_IN] == 0);
 338
 339                 n = get_chain_end(h, 0);
 340                 n += get_entry(h, n)->next_offset;
 341                 assert(h->info.hook_entry[NF_IP_FORWARD] == n);
 342
 343                 n = get_chain_end(h, n);
 344                 n += get_entry(h, n)->next_offset;
 345                 assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
 346
 347                 user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
 348         } else if (strcmp(h->info.name, "nat") == 0) {
 349                 assert((h->info.valid_hooks
 350                         == (1 << NF_IP_PRE_ROUTING
 351                             | 1 << NF_IP_POST_ROUTING
 352                             | 1 << NF_IP_LOCAL_OUT)) ||
 353                        (h->info.valid_hooks
 354                         == (1 << NF_IP_PRE_ROUTING
 355                             | 1 << NF_IP_LOCAL_IN
 356                             | 1 << NF_IP_POST_ROUTING
 357                             | 1 << NF_IP_LOCAL_OUT)));
 358
 359                 assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
 360
 361                 n = get_chain_end(h, 0);
 362
 363                 n += get_entry(h, n)->next_offset;
 364                 assert(h->info.hook_entry[NF_IP_POST_ROUTING] == n);
 365                 n = get_chain_end(h, n);
 366
 367                 n += get_entry(h, n)->next_offset;
 368                 assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
 369                 user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
 370
 371                 if (h->info.valid_hooks & (1 << NF_IP_LOCAL_IN)) {
 372                         n = get_chain_end(h, n);
 373                         n += get_entry(h, n)->next_offset;
 374                         assert(h->info.hook_entry[NF_IP_LOCAL_IN] == n);
 375                         user_offset = h->info.hook_entry[NF_IP_LOCAL_IN];
 376                 }
 377
 378         } else if (strcmp(h->info.name, "mangle") == 0) {
 379                 /* This code is getting ugly because linux < 2.4.18-pre6 had
 380                  * two mangle hooks, linux >= 2.4.18-pre6 has five mangle hooks
 381                  * */
 382                 assert((h->info.valid_hooks
 383                         == (1 << NF_IP_PRE_ROUTING
 384                             | 1 << NF_IP_LOCAL_OUT)) ||
 385                        (h->info.valid_hooks
 386                         == (1 << NF_IP_PRE_ROUTING
 387                             | 1 << NF_IP_LOCAL_IN
 388                             | 1 << NF_IP_FORWARD
 389                             | 1 << NF_IP_LOCAL_OUT
 390                             | 1 << NF_IP_POST_ROUTING)));
 391
 392                 /* Hooks should be first five */
 393                 assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
 394
 395                 n = get_chain_end(h, 0);
 396
 397                 if (h->info.valid_hooks & (1 << NF_IP_LOCAL_IN)) {
 398                         n += get_entry(h, n)->next_offset;
 399                         assert(h->info.hook_entry[NF_IP_LOCAL_IN] == n);
 400                         n = get_chain_end(h, n);
 401                 }
 402
 403                 if (h->info.valid_hooks & (1 << NF_IP_FORWARD)) {
 404                         n += get_entry(h, n)->next_offset;
 405                         assert(h->info.hook_entry[NF_IP_FORWARD] == n);
 406                         n = get_chain_end(h, n);
 407                 }
 408
 409                 n += get_entry(h, n)->next_offset;
 410                 assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
 411                 user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
 412
 413                 if (h->info.valid_hooks & (1 << NF_IP_POST_ROUTING)) {
 414                         n = get_chain_end(h, n);
 415                         n += get_entry(h, n)->next_offset;
 416                         assert(h->info.hook_entry[NF_IP_POST_ROUTING] == n);
 417                         user_offset = h->info.hook_entry[NF_IP_POST_ROUTING];
 418                 }
 419         } else if (strcmp(h->info.name, "raw") == 0) {
 420                 assert(h->info.valid_hooks
 421                        == (1 << NF_IP_PRE_ROUTING
 422                            | 1 << NF_IP_LOCAL_OUT));
 423
 424                 /* Hooks should be first three */
 425                 assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
 426
 427                 n = get_chain_end(h, n);
 428                 n += get_entry(h, n)->next_offset;
 429                 assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
 430
 431                 user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
 432
 433 #ifdef NF_IP_DROPPING
 434         } else if (strcmp(h->info.name, "drop") == 0) {
 435                 assert(h->info.valid_hooks == (1 << NF_IP_DROPPING));
 436
 437                 /* Hook should be first */
 438                 assert(h->info.hook_entry[NF_IP_DROPPING] == 0);
 439                 user_offset = 0;
 440 #endif
 441         } else {
 442                 fprintf(stderr, "Unknown table `%s'\n", h->info.name);
 443                 abort();
 444         }
 445
 446         /* User chain == end of last builtin + policy entry */
 447         user_offset = get_chain_end(h, user_offset);
 448         user_offset += get_entry(h, user_offset)->next_offset;
 449
 450         /* Overflows should be end of entry chains, and unconditional
 451            policy nodes. */
 452         for (i = 0; i < NUMHOOKS; i++) {
 453                 STRUCT_ENTRY *e;
 454                 STRUCT_STANDARD_TARGET *t;
 455
 456                 if (!(h->info.valid_hooks & (1 << i)))
 457                         continue;
 458                 assert(h->info.underflow[i]
 459                        == get_chain_end(h, h->info.hook_entry[i]));
 460
 461                 e = get_entry(h, get_chain_end(h, h->info.hook_entry[i]));
 462                 assert(unconditional(&e->ip));
 463                 assert(e->target_offset == sizeof(*e));
 464                 t = (STRUCT_STANDARD_TARGET *)GET_TARGET(e);
 465                 assert(t->target.u.target_size == ALIGN(sizeof(*t)));
 466                 assert(e->next_offset == sizeof(*e) + ALIGN(sizeof(*t)));
 467
 468                 assert(strcmp(t->target.u.user.name, STANDARD_TARGET)==0);
 469                 assert(t->verdict == -NF_DROP-1 || t->verdict == -NF_ACCEPT-1);
 470
 471                 /* Hooks and underflows must be valid entries */
 472                 entry2index(h, get_entry(h, h->info.hook_entry[i]));
 473                 entry2index(h, get_entry(h, h->info.underflow[i]));
 474         }
 475
 476         assert(h->info.size
 477                >= h->info.num_entries * (sizeof(STRUCT_ENTRY)
 478                                          +sizeof(STRUCT_STANDARD_TARGET)));
 479
 480         assert(h->entries.size
 481                >= (h->new_number
 482                    * (sizeof(STRUCT_ENTRY)
 483                       + sizeof(STRUCT_STANDARD_TARGET))));
 484         assert(strcmp(h->info.name, h->entries.name) == 0);
 485
 486         i = 0; n = 0;
 487         was_return = 0;
 488         /* Check all the entries. */
 489         ENTRY_ITERATE(h->entries.entrytable, h->entries.size,
 490                       check_entry, &i, &n, user_offset, &was_return, h);
 491
 492         assert(i == h->new_number);
 493         assert(n == h->entries.size);
 494
 495         /* Final entry must be error node */
 496         assert(strcmp(GET_TARGET(index2entry(h, h->new_number-1))
 497                       ->u.user.name,
 498                       ERROR_TARGET) == 0);
 499 }
 500 #endif /*IPTC_DEBUG*/
 501
 502 #endif