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      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(__ANDROID__) && (!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 xtc_handle		iptc_handle
     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_CHECK_ENTRY		iptc_check_entry
     80 #define TC_DELETE_ENTRY		iptc_delete_entry
     81 #define TC_DELETE_NUM_ENTRY	iptc_delete_num_entry
     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			XT_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 static int
    129 dump_entry(struct ipt_entry *e, struct iptc_handle *const 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\n", e->nfcache);
    152 
    153 	IPT_MATCH_ITERATE(e, print_match);
    154 
    155 	t = GET_TARGET(e);
    156 	printf("Target name: `%s' [%u]\n", t->u.user.name, t->u.target_size);
    157 	if (strcmp(t->u.user.name, STANDARD_TARGET) == 0) {
    158 		const unsigned char *data = t->data;
    159 		int pos = *(const int *)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->target_offset != b->target_offset
    206 	    || a->next_offset != b->next_offset)
    207 		return NULL;
    208 
    209 	mptr = matchmask + sizeof(STRUCT_ENTRY);
    210 	if (IPT_MATCH_ITERATE(a, match_different, a->elems, b->elems, &mptr))
    211 		return NULL;
    212 	mptr += XT_ALIGN(sizeof(struct ipt_entry_target));
    213 
    214 	return mptr;
    215 }
    216 
    217 #if 0
    218 /***************************** DEBUGGING ********************************/
    219 static inline int
    220 unconditional(const struct ipt_ip *ip)
    221 {
    222 	unsigned int i;
    223 
    224 	for (i = 0; i < sizeof(*ip)/sizeof(uint32_t); i++)
    225 		if (((uint32_t *)ip)[i])
    226 			return 0;
    227 
    228 	return 1;
    229 }
    230 
    231 static inline int
    232 check_match(const STRUCT_ENTRY_MATCH *m, unsigned int *off)
    233 {
    234 	assert(m->u.match_size >= sizeof(STRUCT_ENTRY_MATCH));
    235 	assert(ALIGN(m->u.match_size) == m->u.match_size);
    236 
    237 	(*off) += m->u.match_size;
    238 	return 0;
    239 }
    240 
    241 static inline int
    242 check_entry(const STRUCT_ENTRY *e, unsigned int *i, unsigned int *off,
    243 	    unsigned int user_offset, int *was_return,
    244 	    struct iptc_handle *h)
    245 {
    246 	unsigned int toff;
    247 	STRUCT_STANDARD_TARGET *t;
    248 
    249 	assert(e->target_offset >= sizeof(STRUCT_ENTRY));
    250 	assert(e->next_offset >= e->target_offset
    251 	       + sizeof(STRUCT_ENTRY_TARGET));
    252 	toff = sizeof(STRUCT_ENTRY);
    253 	IPT_MATCH_ITERATE(e, check_match, &toff);
    254 
    255 	assert(toff == e->target_offset);
    256 
    257 	t = (STRUCT_STANDARD_TARGET *)
    258 		GET_TARGET((STRUCT_ENTRY *)e);
    259 	/* next_offset will have to be multiple of entry alignment. */
    260 	assert(e->next_offset == ALIGN(e->next_offset));
    261 	assert(e->target_offset == ALIGN(e->target_offset));
    262 	assert(t->target.u.target_size == ALIGN(t->target.u.target_size));
    263 	assert(!TC_IS_CHAIN(t->target.u.user.name, h));
    264 
    265 	if (strcmp(t->target.u.user.name, STANDARD_TARGET) == 0) {
    266 		assert(t->target.u.target_size
    267 		       == ALIGN(sizeof(STRUCT_STANDARD_TARGET)));
    268 
    269 		assert(t->verdict == -NF_DROP-1
    270 		       || t->verdict == -NF_ACCEPT-1
    271 		       || t->verdict == RETURN
    272 		       || t->verdict < (int)h->entries->size);
    273 
    274 		if (t->verdict >= 0) {
    275 			STRUCT_ENTRY *te = get_entry(h, t->verdict);
    276 			int idx;
    277 
    278 			idx = iptcb_entry2index(h, te);
    279 			assert(strcmp(GET_TARGET(te)->u.user.name,
    280 				      IPT_ERROR_TARGET)
    281 			       != 0);
    282 			assert(te != e);
    283 
    284 			/* Prior node must be error node, or this node. */
    285 			assert(t->verdict == iptcb_entry2offset(h, e)+e->next_offset
    286 			       || strcmp(GET_TARGET(index2entry(h, idx-1))
    287 					 ->u.user.name, IPT_ERROR_TARGET)
    288 			       == 0);
    289 		}
    290 
    291 		if (t->verdict == RETURN
    292 		    && unconditional(&e->ip)
    293 		    && e->target_offset == sizeof(*e))
    294 			*was_return = 1;
    295 		else
    296 			*was_return = 0;
    297 	} else if (strcmp(t->target.u.user.name, IPT_ERROR_TARGET) == 0) {
    298 		assert(t->target.u.target_size
    299 		       == ALIGN(sizeof(struct ipt_error_target)));
    300 
    301 		/* If this is in user area, previous must have been return */
    302 		if (*off > user_offset)
    303 			assert(*was_return);
    304 
    305 		*was_return = 0;
    306 	}
    307 	else *was_return = 0;
    308 
    309 	if (*off == user_offset)
    310 		assert(strcmp(t->target.u.user.name, IPT_ERROR_TARGET) == 0);
    311 
    312 	(*off) += e->next_offset;
    313 	(*i)++;
    314 	return 0;
    315 }
    316 
    317 #ifdef IPTC_DEBUG
    318 /* Do every conceivable sanity check on the handle */
    319 static void
    320 do_check(struct iptc_handle *h, unsigned int line)
    321 {
    322 	unsigned int i, n;
    323 	unsigned int user_offset; /* Offset of first user chain */
    324 	int was_return;
    325 
    326 	assert(h->changed == 0 || h->changed == 1);
    327 	if (strcmp(h->info.name, "filter") == 0) {
    328 		assert(h->info.valid_hooks
    329 		       == (1 << NF_IP_LOCAL_IN
    330 			   | 1 << NF_IP_FORWARD
    331 			   | 1 << NF_IP_LOCAL_OUT));
    332 
    333 		/* Hooks should be first three */
    334 		assert(h->info.hook_entry[NF_IP_LOCAL_IN] == 0);
    335 
    336 		n = get_chain_end(h, 0);
    337 		n += get_entry(h, n)->next_offset;
    338 		assert(h->info.hook_entry[NF_IP_FORWARD] == n);
    339 
    340 		n = get_chain_end(h, n);
    341 		n += get_entry(h, n)->next_offset;
    342 		assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
    343 
    344 		user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
    345 	} else if (strcmp(h->info.name, "nat") == 0) {
    346 		assert((h->info.valid_hooks
    347 		        == (1 << NF_IP_PRE_ROUTING
    348 			    | 1 << NF_IP_POST_ROUTING
    349 			    | 1 << NF_IP_LOCAL_OUT)) ||
    350 		       (h->info.valid_hooks
    351 			== (1 << NF_IP_PRE_ROUTING
    352 			    | 1 << NF_IP_LOCAL_IN
    353 			    | 1 << NF_IP_POST_ROUTING
    354 			    | 1 << NF_IP_LOCAL_OUT)));
    355 
    356 		assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
    357 
    358 		n = get_chain_end(h, 0);
    359 
    360 		n += get_entry(h, n)->next_offset;
    361 		assert(h->info.hook_entry[NF_IP_POST_ROUTING] == n);
    362 		n = get_chain_end(h, n);
    363 
    364 		n += get_entry(h, n)->next_offset;
    365 		assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
    366 		user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
    367 
    368 		if (h->info.valid_hooks & (1 << NF_IP_LOCAL_IN)) {
    369 			n = get_chain_end(h, n);
    370 			n += get_entry(h, n)->next_offset;
    371 			assert(h->info.hook_entry[NF_IP_LOCAL_IN] == n);
    372 			user_offset = h->info.hook_entry[NF_IP_LOCAL_IN];
    373 		}
    374 
    375 	} else if (strcmp(h->info.name, "mangle") == 0) {
    376 		/* This code is getting ugly because linux < 2.4.18-pre6 had
    377 		 * two mangle hooks, linux >= 2.4.18-pre6 has five mangle hooks
    378 		 * */
    379 		assert((h->info.valid_hooks
    380 			== (1 << NF_IP_PRE_ROUTING
    381 			    | 1 << NF_IP_LOCAL_OUT)) ||
    382 		       (h->info.valid_hooks
    383 			== (1 << NF_IP_PRE_ROUTING
    384 			    | 1 << NF_IP_LOCAL_IN
    385 			    | 1 << NF_IP_FORWARD
    386 			    | 1 << NF_IP_LOCAL_OUT
    387 			    | 1 << NF_IP_POST_ROUTING)));
    388 
    389 		/* Hooks should be first five */
    390 		assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
    391 
    392 		n = get_chain_end(h, 0);
    393 
    394 		if (h->info.valid_hooks & (1 << NF_IP_LOCAL_IN)) {
    395 			n += get_entry(h, n)->next_offset;
    396 			assert(h->info.hook_entry[NF_IP_LOCAL_IN] == n);
    397 			n = get_chain_end(h, n);
    398 		}
    399 
    400 		if (h->info.valid_hooks & (1 << NF_IP_FORWARD)) {
    401 			n += get_entry(h, n)->next_offset;
    402 			assert(h->info.hook_entry[NF_IP_FORWARD] == n);
    403 			n = get_chain_end(h, n);
    404 		}
    405 
    406 		n += get_entry(h, n)->next_offset;
    407 		assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
    408 		user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
    409 
    410 		if (h->info.valid_hooks & (1 << NF_IP_POST_ROUTING)) {
    411 			n = get_chain_end(h, n);
    412 			n += get_entry(h, n)->next_offset;
    413 			assert(h->info.hook_entry[NF_IP_POST_ROUTING] == n);
    414 			user_offset = h->info.hook_entry[NF_IP_POST_ROUTING];
    415 		}
    416 	} else if (strcmp(h->info.name, "raw") == 0) {
    417 		assert(h->info.valid_hooks
    418 		       == (1 << NF_IP_PRE_ROUTING
    419 			   | 1 << NF_IP_LOCAL_OUT));
    420 
    421 		/* Hooks should be first three */
    422 		assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
    423 
    424 		n = get_chain_end(h, n);
    425 		n += get_entry(h, n)->next_offset;
    426 		assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
    427 
    428 		user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
    429 
    430 #ifdef NF_IP_DROPPING
    431 	} else if (strcmp(h->info.name, "drop") == 0) {
    432 		assert(h->info.valid_hooks == (1 << NF_IP_DROPPING));
    433 
    434 		/* Hook should be first */
    435 		assert(h->info.hook_entry[NF_IP_DROPPING] == 0);
    436 		user_offset = 0;
    437 #endif
    438 	} else {
    439 		fprintf(stderr, "Unknown table `%s'\n", h->info.name);
    440 		abort();
    441 	}
    442 
    443 	/* User chain == end of last builtin + policy entry */
    444 	user_offset = get_chain_end(h, user_offset);
    445 	user_offset += get_entry(h, user_offset)->next_offset;
    446 
    447 	/* Overflows should be end of entry chains, and unconditional
    448            policy nodes. */
    449 	for (i = 0; i < NUMHOOKS; i++) {
    450 		STRUCT_ENTRY *e;
    451 		STRUCT_STANDARD_TARGET *t;
    452 
    453 		if (!(h->info.valid_hooks & (1 << i)))
    454 			continue;
    455 		assert(h->info.underflow[i]
    456 		       == get_chain_end(h, h->info.hook_entry[i]));
    457 
    458 		e = get_entry(h, get_chain_end(h, h->info.hook_entry[i]));
    459 		assert(unconditional(&e->ip));
    460 		assert(e->target_offset == sizeof(*e));
    461 		t = (STRUCT_STANDARD_TARGET *)GET_TARGET(e);
    462 		assert(t->target.u.target_size == ALIGN(sizeof(*t)));
    463 		assert(e->next_offset == sizeof(*e) + ALIGN(sizeof(*t)));
    464 
    465 		assert(strcmp(t->target.u.user.name, STANDARD_TARGET)==0);
    466 		assert(t->verdict == -NF_DROP-1 || t->verdict == -NF_ACCEPT-1);
    467 
    468 		/* Hooks and underflows must be valid entries */
    469 		entry2index(h, get_entry(h, h->info.hook_entry[i]));
    470 		entry2index(h, get_entry(h, h->info.underflow[i]));
    471 	}
    472 
    473 	assert(h->info.size
    474 	       >= h->info.num_entries * (sizeof(STRUCT_ENTRY)
    475 					 +sizeof(STRUCT_STANDARD_TARGET)));
    476 
    477 	assert(h->entries.size
    478 	       >= (h->new_number
    479 		   * (sizeof(STRUCT_ENTRY)
    480 		      + sizeof(STRUCT_STANDARD_TARGET))));
    481 	assert(strcmp(h->info.name, h->entries.name) == 0);
    482 
    483 	i = 0; n = 0;
    484 	was_return = 0;
    485 	/* Check all the entries. */
    486 	ENTRY_ITERATE(h->entries.entrytable, h->entries.size,
    487 		      check_entry, &i, &n, user_offset, &was_return, h);
    488 
    489 	assert(i == h->new_number);
    490 	assert(n == h->entries.size);
    491 
    492 	/* Final entry must be error node */
    493 	assert(strcmp(GET_TARGET(index2entry(h, h->new_number-1))
    494 		      ->u.user.name,
    495 		      ERROR_TARGET) == 0);
    496 }
    497 #endif /*IPTC_DEBUG*/
    498 
    499 #endif
    500