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
  98 #define TC_AF                   AF_INET
  99 #define TC_IPPROTO              IPPROTO_IP
 100
 101 #define SO_SET_REPLACE          IPT_SO_SET_REPLACE
 102 #define SO_SET_ADD_COUNTERS     IPT_SO_SET_ADD_COUNTERS
 103 #define SO_GET_INFO             IPT_SO_GET_INFO
 104 #define SO_GET_ENTRIES          IPT_SO_GET_ENTRIES
 105 #define SO_GET_VERSION          IPT_SO_GET_VERSION
 106
 107 #define STANDARD_TARGET         IPT_STANDARD_TARGET
 108 #define LABEL_RETURN            IPTC_LABEL_RETURN
 109 #define LABEL_ACCEPT            IPTC_LABEL_ACCEPT
 110 #define LABEL_DROP              IPTC_LABEL_DROP
 111 #define LABEL_QUEUE             IPTC_LABEL_QUEUE
 112
 113 #define ALIGN                   IPT_ALIGN
 114 #define RETURN                  IPT_RETURN
 115
 116 #include "libiptc.c"
 117
 118 #define IP_PARTS_NATIVE(n)                      \
 119 (unsigned int)((n)>>24)&0xFF,                   \
 120 (unsigned int)((n)>>16)&0xFF,                   \
 121 (unsigned int)((n)>>8)&0xFF,                    \
 122 (unsigned int)((n)&0xFF)
 123
 124 #define IP_PARTS(n) IP_PARTS_NATIVE(ntohl(n))
 125
 126 int
 127 dump_entry(STRUCT_ENTRY *e, const TC_HANDLE_T handle)
 128 {
 129         size_t i;
 130         STRUCT_ENTRY_TARGET *t;
 131
 132         printf("Entry %u (%lu):\n", iptcb_entry2index(handle, e),
 133                iptcb_entry2offset(handle, e));
 134         printf("SRC IP: %u.%u.%u.%u/%u.%u.%u.%u\n",
 135                IP_PARTS(e->ip.src.s_addr),IP_PARTS(e->ip.smsk.s_addr));
 136         printf("DST IP: %u.%u.%u.%u/%u.%u.%u.%u\n",
 137                IP_PARTS(e->ip.dst.s_addr),IP_PARTS(e->ip.dmsk.s_addr));
 138         printf("Interface: `%s'/", e->ip.iniface);
 139         for (i = 0; i < IFNAMSIZ; i++)
 140                 printf("%c", e->ip.iniface_mask[i] ? 'X' : '.');
 141         printf("to `%s'/", e->ip.outiface);
 142         for (i = 0; i < IFNAMSIZ; i++)
 143                 printf("%c", e->ip.outiface_mask[i] ? 'X' : '.');
 144         printf("\nProtocol: %u\n", e->ip.proto);
 145         printf("Flags: %02X\n", e->ip.flags);
 146         printf("Invflags: %02X\n", e->ip.invflags);
 147         printf("Counters: %llu packets, %llu bytes\n",
 148                (unsigned long long)e->counters.pcnt, (unsigned long long)e->counters.bcnt);
 149         printf("Cache: %08X ", e->nfcache);
 150         if (e->nfcache & NFC_ALTERED) printf("ALTERED ");
 151         if (e->nfcache & NFC_UNKNOWN) printf("UNKNOWN ");
 152         printf("\n");
 153
 154         IPT_MATCH_ITERATE(e, print_match);
 155
 156         t = GET_TARGET(e);
 157         printf("Target name: `%s' [%u]\n", t->u.user.name, t->u.target_size);
 158         if (strcmp(t->u.user.name, STANDARD_TARGET) == 0) {
 159                 int pos = *(int *)t->data;
 160                 if (pos < 0)
 161                         printf("verdict=%s\n",
 162                                pos == -NF_ACCEPT-1 ? "NF_ACCEPT"
 163                                : pos == -NF_DROP-1 ? "NF_DROP"
 164                                : pos == -NF_QUEUE-1 ? "NF_QUEUE"
 165                                : pos == RETURN ? "RETURN"
 166                                : "UNKNOWN");
 167                 else
 168                         printf("verdict=%u\n", pos);
 169         } else if (strcmp(t->u.user.name, IPT_ERROR_TARGET) == 0)
 170                 printf("error=`%s'\n", t->data);
 171
 172         printf("\n");
 173         return 0;
 174 }
 175
 176 static unsigned char *
 177 is_same(const STRUCT_ENTRY *a, const STRUCT_ENTRY *b, unsigned char *matchmask)
 178 {
 179         unsigned int i;
 180         unsigned char *mptr;
 181
 182         /* Always compare head structures: ignore mask here. */
 183         if (a->ip.src.s_addr != b->ip.src.s_addr
 184             || a->ip.dst.s_addr != b->ip.dst.s_addr
 185             || a->ip.smsk.s_addr != b->ip.smsk.s_addr
 186             || a->ip.dmsk.s_addr != b->ip.dmsk.s_addr
 187             || a->ip.proto != b->ip.proto
 188             || a->ip.flags != b->ip.flags
 189             || a->ip.invflags != b->ip.invflags)
 190                 return NULL;
 191
 192         for (i = 0; i < IFNAMSIZ; i++) {
 193                 if (a->ip.iniface_mask[i] != b->ip.iniface_mask[i])
 194                         return NULL;
 195                 if ((a->ip.iniface[i] & a->ip.iniface_mask[i])
 196                     != (b->ip.iniface[i] & b->ip.iniface_mask[i]))
 197                         return NULL;
 198                 if (a->ip.outiface_mask[i] != b->ip.outiface_mask[i])
 199                         return NULL;
 200                 if ((a->ip.outiface[i] & a->ip.outiface_mask[i])
 201                     != (b->ip.outiface[i] & b->ip.outiface_mask[i]))
 202                         return NULL;
 203         }
 204
 205         if (a->nfcache != b->nfcache
 206             || a->target_offset != b->target_offset
 207             || a->next_offset != b->next_offset)
 208                 return NULL;
 209
 210         mptr = matchmask + sizeof(STRUCT_ENTRY);
 211         if (IPT_MATCH_ITERATE(a, match_different, a->elems, b->elems, &mptr))
 212                 return NULL;
 213         mptr += IPT_ALIGN(sizeof(struct ipt_entry_target));
 214
 215         return mptr;
 216 }
 217
 218 #if 0
 219 /***************************** DEBUGGING ********************************/
 220 static inline int
 221 unconditional(const struct ipt_ip *ip)
 222 {
 223         unsigned int i;
 224
 225         for (i = 0; i < sizeof(*ip)/sizeof(u_int32_t); i++)
 226                 if (((u_int32_t *)ip)[i])
 227                         return 0;
 228
 229         return 1;
 230 }
 231
 232 static inline int
 233 check_match(const STRUCT_ENTRY_MATCH *m, unsigned int *off)
 234 {
 235         assert(m->u.match_size >= sizeof(STRUCT_ENTRY_MATCH));
 236         assert(ALIGN(m->u.match_size) == m->u.match_size);
 237
 238         (*off) += m->u.match_size;
 239         return 0;
 240 }
 241
 242 static inline int
 243 check_entry(const STRUCT_ENTRY *e, unsigned int *i, unsigned int *off,
 244             unsigned int user_offset, int *was_return,
 245             TC_HANDLE_T h)
 246 {
 247         unsigned int toff;
 248         STRUCT_STANDARD_TARGET *t;
 249
 250         assert(e->target_offset >= sizeof(STRUCT_ENTRY));
 251         assert(e->next_offset >= e->target_offset
 252                + sizeof(STRUCT_ENTRY_TARGET));
 253         toff = sizeof(STRUCT_ENTRY);
 254         IPT_MATCH_ITERATE(e, check_match, &toff);
 255
 256         assert(toff == e->target_offset);
 257
 258         t = (STRUCT_STANDARD_TARGET *)
 259                 GET_TARGET((STRUCT_ENTRY *)e);
 260         /* next_offset will have to be multiple of entry alignment. */
 261         assert(e->next_offset == ALIGN(e->next_offset));
 262         assert(e->target_offset == ALIGN(e->target_offset));
 263         assert(t->target.u.target_size == ALIGN(t->target.u.target_size));
 264         assert(!TC_IS_CHAIN(t->target.u.user.name, h));
 265
 266         if (strcmp(t->target.u.user.name, STANDARD_TARGET) == 0) {
 267                 assert(t->target.u.target_size
 268                        == ALIGN(sizeof(STRUCT_STANDARD_TARGET)));
 269
 270                 assert(t->verdict == -NF_DROP-1
 271                        || t->verdict == -NF_ACCEPT-1
 272                        || t->verdict == RETURN
 273                        || t->verdict < (int)h->entries->size);
 274
 275                 if (t->verdict >= 0) {
 276                         STRUCT_ENTRY *te = get_entry(h, t->verdict);
 277                         int idx;
 278
 279                         idx = iptcb_entry2index(h, te);
 280                         assert(strcmp(GET_TARGET(te)->u.user.name,
 281                                       IPT_ERROR_TARGET)
 282                                != 0);
 283                         assert(te != e);
 284
 285                         /* Prior node must be error node, or this node. */
 286                         assert(t->verdict == iptcb_entry2offset(h, e)+e->next_offset
 287                                || strcmp(GET_TARGET(index2entry(h, idx-1))
 288                                          ->u.user.name, IPT_ERROR_TARGET)
 289                                == 0);
 290                 }
 291
 292                 if (t->verdict == RETURN
 293                     && unconditional(&e->ip)
 294                     && e->target_offset == sizeof(*e))
 295                         *was_return = 1;
 296                 else
 297                         *was_return = 0;
 298         } else if (strcmp(t->target.u.user.name, IPT_ERROR_TARGET) == 0) {
 299                 assert(t->target.u.target_size
 300                        == ALIGN(sizeof(struct ipt_error_target)));
 301
 302                 /* If this is in user area, previous must have been return */
 303                 if (*off > user_offset)
 304                         assert(*was_return);
 305
 306                 *was_return = 0;
 307         }
 308         else *was_return = 0;
 309
 310         if (*off == user_offset)
 311                 assert(strcmp(t->target.u.user.name, IPT_ERROR_TARGET) == 0);
 312
 313         (*off) += e->next_offset;
 314         (*i)++;
 315         return 0;
 316 }
 317
 318 #ifdef IPTC_DEBUG
 319 /* Do every conceivable sanity check on the handle */
 320 static void
 321 do_check(TC_HANDLE_T h, unsigned int line)
 322 {
 323         unsigned int i, n;
 324         unsigned int user_offset; /* Offset of first user chain */
 325         int was_return;
 326
 327         assert(h->changed == 0 || h->changed == 1);
 328         if (strcmp(h->info.name, "filter") == 0) {
 329                 assert(h->info.valid_hooks
 330                        == (1 << NF_IP_LOCAL_IN
 331                            | 1 << NF_IP_FORWARD
 332                            | 1 << NF_IP_LOCAL_OUT));
 333
 334                 /* Hooks should be first three */
 335                 assert(h->info.hook_entry[NF_IP_LOCAL_IN] == 0);
 336
 337                 n = get_chain_end(h, 0);
 338                 n += get_entry(h, n)->next_offset;
 339                 assert(h->info.hook_entry[NF_IP_FORWARD] == n);
 340
 341                 n = get_chain_end(h, n);
 342                 n += get_entry(h, n)->next_offset;
 343                 assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
 344
 345                 user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
 346         } else if (strcmp(h->info.name, "nat") == 0) {
 347                 assert((h->info.valid_hooks
 348                         == (1 << NF_IP_PRE_ROUTING
 349                             | 1 << NF_IP_POST_ROUTING
 350                             | 1 << NF_IP_LOCAL_OUT)) ||
 351                        (h->info.valid_hooks
 352                         == (1 << NF_IP_PRE_ROUTING
 353                             | 1 << NF_IP_LOCAL_IN
 354                             | 1 << NF_IP_POST_ROUTING
 355                             | 1 << NF_IP_LOCAL_OUT)));
 356
 357                 assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
 358
 359                 n = get_chain_end(h, 0);
 360
 361                 n += get_entry(h, n)->next_offset;
 362                 assert(h->info.hook_entry[NF_IP_POST_ROUTING] == n);
 363                 n = get_chain_end(h, n);
 364
 365                 n += get_entry(h, n)->next_offset;
 366                 assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
 367                 user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
 368
 369                 if (h->info.valid_hooks & (1 << NF_IP_LOCAL_IN)) {
 370                         n = get_chain_end(h, n);
 371                         n += get_entry(h, n)->next_offset;
 372                         assert(h->info.hook_entry[NF_IP_LOCAL_IN] == n);
 373                         user_offset = h->info.hook_entry[NF_IP_LOCAL_IN];
 374                 }
 375
 376         } else if (strcmp(h->info.name, "mangle") == 0) {
 377                 /* This code is getting ugly because linux < 2.4.18-pre6 had
 378                  * two mangle hooks, linux >= 2.4.18-pre6 has five mangle hooks
 379                  * */
 380                 assert((h->info.valid_hooks
 381                         == (1 << NF_IP_PRE_ROUTING
 382                             | 1 << NF_IP_LOCAL_OUT)) ||
 383                        (h->info.valid_hooks
 384                         == (1 << NF_IP_PRE_ROUTING
 385                             | 1 << NF_IP_LOCAL_IN
 386                             | 1 << NF_IP_FORWARD
 387                             | 1 << NF_IP_LOCAL_OUT
 388                             | 1 << NF_IP_POST_ROUTING)));
 389
 390                 /* Hooks should be first five */
 391                 assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
 392
 393                 n = get_chain_end(h, 0);
 394
 395                 if (h->info.valid_hooks & (1 << NF_IP_LOCAL_IN)) {
 396                         n += get_entry(h, n)->next_offset;
 397                         assert(h->info.hook_entry[NF_IP_LOCAL_IN] == n);
 398                         n = get_chain_end(h, n);
 399                 }
 400
 401                 if (h->info.valid_hooks & (1 << NF_IP_FORWARD)) {
 402                         n += get_entry(h, n)->next_offset;
 403                         assert(h->info.hook_entry[NF_IP_FORWARD] == n);
 404                         n = get_chain_end(h, n);
 405                 }
 406
 407                 n += get_entry(h, n)->next_offset;
 408                 assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
 409                 user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
 410
 411                 if (h->info.valid_hooks & (1 << NF_IP_POST_ROUTING)) {
 412                         n = get_chain_end(h, n);
 413                         n += get_entry(h, n)->next_offset;
 414                         assert(h->info.hook_entry[NF_IP_POST_ROUTING] == n);
 415                         user_offset = h->info.hook_entry[NF_IP_POST_ROUTING];
 416                 }
 417         } else if (strcmp(h->info.name, "raw") == 0) {
 418                 assert(h->info.valid_hooks
 419                        == (1 << NF_IP_PRE_ROUTING
 420                            | 1 << NF_IP_LOCAL_OUT));
 421
 422                 /* Hooks should be first three */
 423                 assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
 424
 425                 n = get_chain_end(h, n);
 426                 n += get_entry(h, n)->next_offset;
 427                 assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
 428
 429                 user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
 430
 431 #ifdef NF_IP_DROPPING
 432         } else if (strcmp(h->info.name, "drop") == 0) {
 433                 assert(h->info.valid_hooks == (1 << NF_IP_DROPPING));
 434
 435                 /* Hook should be first */
 436                 assert(h->info.hook_entry[NF_IP_DROPPING] == 0);
 437                 user_offset = 0;
 438 #endif
 439         } else {
 440                 fprintf(stderr, "Unknown table `%s'\n", h->info.name);
 441                 abort();
 442         }
 443
 444         /* User chain == end of last builtin + policy entry */
 445         user_offset = get_chain_end(h, user_offset);
 446         user_offset += get_entry(h, user_offset)->next_offset;
 447
 448         /* Overflows should be end of entry chains, and unconditional
 449            policy nodes. */
 450         for (i = 0; i < NUMHOOKS; i++) {
 451                 STRUCT_ENTRY *e;
 452                 STRUCT_STANDARD_TARGET *t;
 453
 454                 if (!(h->info.valid_hooks & (1 << i)))
 455                         continue;
 456                 assert(h->info.underflow[i]
 457                        == get_chain_end(h, h->info.hook_entry[i]));
 458
 459                 e = get_entry(h, get_chain_end(h, h->info.hook_entry[i]));
 460                 assert(unconditional(&e->ip));
 461                 assert(e->target_offset == sizeof(*e));
 462                 t = (STRUCT_STANDARD_TARGET *)GET_TARGET(e);
 463                 assert(t->target.u.target_size == ALIGN(sizeof(*t)));
 464                 assert(e->next_offset == sizeof(*e) + ALIGN(sizeof(*t)));
 465
 466                 assert(strcmp(t->target.u.user.name, STANDARD_TARGET)==0);
 467                 assert(t->verdict == -NF_DROP-1 || t->verdict == -NF_ACCEPT-1);
 468
 469                 /* Hooks and underflows must be valid entries */
 470                 entry2index(h, get_entry(h, h->info.hook_entry[i]));
 471                 entry2index(h, get_entry(h, h->info.underflow[i]));
 472         }
 473
 474         assert(h->info.size
 475                >= h->info.num_entries * (sizeof(STRUCT_ENTRY)
 476                                          +sizeof(STRUCT_STANDARD_TARGET)));
 477
 478         assert(h->entries.size
 479                >= (h->new_number
 480                    * (sizeof(STRUCT_ENTRY)
 481                       + sizeof(STRUCT_STANDARD_TARGET))));
 482         assert(strcmp(h->info.name, h->entries.name) == 0);
 483
 484         i = 0; n = 0;
 485         was_return = 0;
 486         /* Check all the entries. */
 487         ENTRY_ITERATE(h->entries.entrytable, h->entries.size,
 488                       check_entry, &i, &n, user_offset, &was_return, h);
 489
 490         assert(i == h->new_number);
 491         assert(n == h->entries.size);
 492
 493         /* Final entry must be error node */
 494         assert(strcmp(GET_TARGET(index2entry(h, h->new_number-1))
 495                       ->u.user.name,
 496                       ERROR_TARGET) == 0);
 497 }
 498 #endif /*IPTC_DEBUG*/
 499
 500 #endif