libip4tc.c revision d59b9db031abee37a9aa9776662dd15370faabf4 
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)
26typedef 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			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
128static int
129dump_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
176static unsigned char *
177is_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 += IPT_ALIGN(sizeof(struct ipt_entry_target));
213
214	return mptr;
215}
216
217#if 0
218/***************************** DEBUGGING ********************************/
219static inline int
220unconditional(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
231static inline int
232check_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
241static inline int
242check_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 */
319static void
320do_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