libip4tc.c revision 1639fe86579f86f5f6a954a9b0adde2e16ad1980 
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
40#define STRUCT_ENTRY_TARGET	struct ipt_entry_target
41#define STRUCT_ENTRY		struct ipt_entry
42#define STRUCT_ENTRY_MATCH	struct ipt_entry_match
43#define STRUCT_GETINFO		struct ipt_getinfo
44#define STRUCT_GET_ENTRIES	struct ipt_get_entries
45#define STRUCT_COUNTERS		struct ipt_counters
46#define STRUCT_COUNTERS_INFO	struct ipt_counters_info
47#define STRUCT_STANDARD_TARGET	struct ipt_standard_target
48#define STRUCT_REPLACE		struct ipt_replace
49
50#define ENTRY_ITERATE		IPT_ENTRY_ITERATE
51#define TABLE_MAXNAMELEN	IPT_TABLE_MAXNAMELEN
52#define FUNCTION_MAXNAMELEN	IPT_FUNCTION_MAXNAMELEN
53
54#define GET_TARGET		ipt_get_target
55
56#define ERROR_TARGET		IPT_ERROR_TARGET
57#define NUMHOOKS		NF_IP_NUMHOOKS
58
59#define IPT_CHAINLABEL		xt_chainlabel
60
61#define TC_DUMP_ENTRIES		dump_entries
62#define TC_IS_CHAIN		iptc_is_chain
63#define TC_FIRST_CHAIN		iptc_first_chain
64#define TC_NEXT_CHAIN		iptc_next_chain
65#define TC_FIRST_RULE		iptc_first_rule
66#define TC_NEXT_RULE		iptc_next_rule
67#define TC_GET_TARGET		iptc_get_target
68#define TC_BUILTIN		iptc_builtin
69#define TC_GET_POLICY		iptc_get_policy
70#define TC_INSERT_ENTRY		iptc_insert_entry
71#define TC_REPLACE_ENTRY	iptc_replace_entry
72#define TC_APPEND_ENTRY		iptc_append_entry
73#define TC_CHECK_ENTRY		iptc_check_entry
74#define TC_DELETE_ENTRY		iptc_delete_entry
75#define TC_DELETE_NUM_ENTRY	iptc_delete_num_entry
76#define TC_FLUSH_ENTRIES	iptc_flush_entries
77#define TC_ZERO_ENTRIES		iptc_zero_entries
78#define TC_READ_COUNTER		iptc_read_counter
79#define TC_ZERO_COUNTER		iptc_zero_counter
80#define TC_SET_COUNTER		iptc_set_counter
81#define TC_CREATE_CHAIN		iptc_create_chain
82#define TC_GET_REFERENCES	iptc_get_references
83#define TC_DELETE_CHAIN		iptc_delete_chain
84#define TC_RENAME_CHAIN		iptc_rename_chain
85#define TC_SET_POLICY		iptc_set_policy
86#define TC_GET_RAW_SOCKET	iptc_get_raw_socket
87#define TC_INIT			iptc_init
88#define TC_FREE			iptc_free
89#define TC_COMMIT		iptc_commit
90#define TC_STRERROR		iptc_strerror
91#define TC_NUM_RULES		iptc_num_rules
92#define TC_GET_RULE		iptc_get_rule
93
94#define TC_AF			AF_INET
95#define TC_IPPROTO		IPPROTO_IP
96
97#define SO_SET_REPLACE		IPT_SO_SET_REPLACE
98#define SO_SET_ADD_COUNTERS	IPT_SO_SET_ADD_COUNTERS
99#define SO_GET_INFO		IPT_SO_GET_INFO
100#define SO_GET_ENTRIES		IPT_SO_GET_ENTRIES
101#define SO_GET_VERSION		IPT_SO_GET_VERSION
102
103#define STANDARD_TARGET		IPT_STANDARD_TARGET
104#define LABEL_RETURN		IPTC_LABEL_RETURN
105#define LABEL_ACCEPT		IPTC_LABEL_ACCEPT
106#define LABEL_DROP		IPTC_LABEL_DROP
107#define LABEL_QUEUE		IPTC_LABEL_QUEUE
108
109#define ALIGN			XT_ALIGN
110#define RETURN			IPT_RETURN
111
112#include "libiptc.c"
113
114#define IP_PARTS_NATIVE(n)			\
115(unsigned int)((n)>>24)&0xFF,			\
116(unsigned int)((n)>>16)&0xFF,			\
117(unsigned int)((n)>>8)&0xFF,			\
118(unsigned int)((n)&0xFF)
119
120#define IP_PARTS(n) IP_PARTS_NATIVE(ntohl(n))
121
122static int
123dump_entry(struct ipt_entry *e, struct xtc_handle *const handle)
124{
125	size_t i;
126	STRUCT_ENTRY_TARGET *t;
127
128	printf("Entry %u (%lu):\n", iptcb_entry2index(handle, e),
129	       iptcb_entry2offset(handle, e));
130	printf("SRC IP: %u.%u.%u.%u/%u.%u.%u.%u\n",
131	       IP_PARTS(e->ip.src.s_addr),IP_PARTS(e->ip.smsk.s_addr));
132	printf("DST IP: %u.%u.%u.%u/%u.%u.%u.%u\n",
133	       IP_PARTS(e->ip.dst.s_addr),IP_PARTS(e->ip.dmsk.s_addr));
134	printf("Interface: `%s'/", e->ip.iniface);
135	for (i = 0; i < IFNAMSIZ; i++)
136		printf("%c", e->ip.iniface_mask[i] ? 'X' : '.');
137	printf("to `%s'/", e->ip.outiface);
138	for (i = 0; i < IFNAMSIZ; i++)
139		printf("%c", e->ip.outiface_mask[i] ? 'X' : '.');
140	printf("\nProtocol: %u\n", e->ip.proto);
141	printf("Flags: %02X\n", e->ip.flags);
142	printf("Invflags: %02X\n", e->ip.invflags);
143	printf("Counters: %llu packets, %llu bytes\n",
144	       (unsigned long long)e->counters.pcnt, (unsigned long long)e->counters.bcnt);
145	printf("Cache: %08X\n", e->nfcache);
146
147	IPT_MATCH_ITERATE(e, print_match);
148
149	t = GET_TARGET(e);
150	printf("Target name: `%s' [%u]\n", t->u.user.name, t->u.target_size);
151	if (strcmp(t->u.user.name, STANDARD_TARGET) == 0) {
152		const unsigned char *data = t->data;
153		int pos = *(const int *)data;
154		if (pos < 0)
155			printf("verdict=%s\n",
156			       pos == -NF_ACCEPT-1 ? "NF_ACCEPT"
157			       : pos == -NF_DROP-1 ? "NF_DROP"
158			       : pos == -NF_QUEUE-1 ? "NF_QUEUE"
159			       : pos == RETURN ? "RETURN"
160			       : "UNKNOWN");
161		else
162			printf("verdict=%u\n", pos);
163	} else if (strcmp(t->u.user.name, IPT_ERROR_TARGET) == 0)
164		printf("error=`%s'\n", t->data);
165
166	printf("\n");
167	return 0;
168}
169
170static unsigned char *
171is_same(const STRUCT_ENTRY *a, const STRUCT_ENTRY *b, unsigned char *matchmask)
172{
173	unsigned int i;
174	unsigned char *mptr;
175
176	/* Always compare head structures: ignore mask here. */
177	if (a->ip.src.s_addr != b->ip.src.s_addr
178	    || a->ip.dst.s_addr != b->ip.dst.s_addr
179	    || a->ip.smsk.s_addr != b->ip.smsk.s_addr
180	    || a->ip.dmsk.s_addr != b->ip.dmsk.s_addr
181	    || a->ip.proto != b->ip.proto
182	    || a->ip.flags != b->ip.flags
183	    || a->ip.invflags != b->ip.invflags)
184		return NULL;
185
186	for (i = 0; i < IFNAMSIZ; i++) {
187		if (a->ip.iniface_mask[i] != b->ip.iniface_mask[i])
188			return NULL;
189		if ((a->ip.iniface[i] & a->ip.iniface_mask[i])
190		    != (b->ip.iniface[i] & b->ip.iniface_mask[i]))
191			return NULL;
192		if (a->ip.outiface_mask[i] != b->ip.outiface_mask[i])
193			return NULL;
194		if ((a->ip.outiface[i] & a->ip.outiface_mask[i])
195		    != (b->ip.outiface[i] & b->ip.outiface_mask[i]))
196			return NULL;
197	}
198
199	if (a->target_offset != b->target_offset
200	    || a->next_offset != b->next_offset)
201		return NULL;
202
203	mptr = matchmask + sizeof(STRUCT_ENTRY);
204	if (IPT_MATCH_ITERATE(a, match_different, a->elems, b->elems, &mptr))
205		return NULL;
206	mptr += XT_ALIGN(sizeof(struct ipt_entry_target));
207
208	return mptr;
209}
210
211#if 0
212/***************************** DEBUGGING ********************************/
213static inline int
214unconditional(const struct ipt_ip *ip)
215{
216	unsigned int i;
217
218	for (i = 0; i < sizeof(*ip)/sizeof(uint32_t); i++)
219		if (((uint32_t *)ip)[i])
220			return 0;
221
222	return 1;
223}
224
225static inline int
226check_match(const STRUCT_ENTRY_MATCH *m, unsigned int *off)
227{
228	assert(m->u.match_size >= sizeof(STRUCT_ENTRY_MATCH));
229	assert(ALIGN(m->u.match_size) == m->u.match_size);
230
231	(*off) += m->u.match_size;
232	return 0;
233}
234
235static inline int
236check_entry(const STRUCT_ENTRY *e, unsigned int *i, unsigned int *off,
237	    unsigned int user_offset, int *was_return,
238	    struct xtc_handle *h)
239{
240	unsigned int toff;
241	STRUCT_STANDARD_TARGET *t;
242
243	assert(e->target_offset >= sizeof(STRUCT_ENTRY));
244	assert(e->next_offset >= e->target_offset
245	       + sizeof(STRUCT_ENTRY_TARGET));
246	toff = sizeof(STRUCT_ENTRY);
247	IPT_MATCH_ITERATE(e, check_match, &toff);
248
249	assert(toff == e->target_offset);
250
251	t = (STRUCT_STANDARD_TARGET *)
252		GET_TARGET((STRUCT_ENTRY *)e);
253	/* next_offset will have to be multiple of entry alignment. */
254	assert(e->next_offset == ALIGN(e->next_offset));
255	assert(e->target_offset == ALIGN(e->target_offset));
256	assert(t->target.u.target_size == ALIGN(t->target.u.target_size));
257	assert(!TC_IS_CHAIN(t->target.u.user.name, h));
258
259	if (strcmp(t->target.u.user.name, STANDARD_TARGET) == 0) {
260		assert(t->target.u.target_size
261		       == ALIGN(sizeof(STRUCT_STANDARD_TARGET)));
262
263		assert(t->verdict == -NF_DROP-1
264		       || t->verdict == -NF_ACCEPT-1
265		       || t->verdict == RETURN
266		       || t->verdict < (int)h->entries->size);
267
268		if (t->verdict >= 0) {
269			STRUCT_ENTRY *te = get_entry(h, t->verdict);
270			int idx;
271
272			idx = iptcb_entry2index(h, te);
273			assert(strcmp(GET_TARGET(te)->u.user.name,
274				      IPT_ERROR_TARGET)
275			       != 0);
276			assert(te != e);
277
278			/* Prior node must be error node, or this node. */
279			assert(t->verdict == iptcb_entry2offset(h, e)+e->next_offset
280			       || strcmp(GET_TARGET(index2entry(h, idx-1))
281					 ->u.user.name, IPT_ERROR_TARGET)
282			       == 0);
283		}
284
285		if (t->verdict == RETURN
286		    && unconditional(&e->ip)
287		    && e->target_offset == sizeof(*e))
288			*was_return = 1;
289		else
290			*was_return = 0;
291	} else if (strcmp(t->target.u.user.name, IPT_ERROR_TARGET) == 0) {
292		assert(t->target.u.target_size
293		       == ALIGN(sizeof(struct ipt_error_target)));
294
295		/* If this is in user area, previous must have been return */
296		if (*off > user_offset)
297			assert(*was_return);
298
299		*was_return = 0;
300	}
301	else *was_return = 0;
302
303	if (*off == user_offset)
304		assert(strcmp(t->target.u.user.name, IPT_ERROR_TARGET) == 0);
305
306	(*off) += e->next_offset;
307	(*i)++;
308	return 0;
309}
310
311#ifdef IPTC_DEBUG
312/* Do every conceivable sanity check on the handle */
313static void
314do_check(struct xtc_handle *h, unsigned int line)
315{
316	unsigned int i, n;
317	unsigned int user_offset; /* Offset of first user chain */
318	int was_return;
319
320	assert(h->changed == 0 || h->changed == 1);
321	if (strcmp(h->info.name, "filter") == 0) {
322		assert(h->info.valid_hooks
323		       == (1 << NF_IP_LOCAL_IN
324			   | 1 << NF_IP_FORWARD
325			   | 1 << NF_IP_LOCAL_OUT));
326
327		/* Hooks should be first three */
328		assert(h->info.hook_entry[NF_IP_LOCAL_IN] == 0);
329
330		n = get_chain_end(h, 0);
331		n += get_entry(h, n)->next_offset;
332		assert(h->info.hook_entry[NF_IP_FORWARD] == n);
333
334		n = get_chain_end(h, n);
335		n += get_entry(h, n)->next_offset;
336		assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
337
338		user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
339	} else if (strcmp(h->info.name, "nat") == 0) {
340		assert((h->info.valid_hooks
341		        == (1 << NF_IP_PRE_ROUTING
342			    | 1 << NF_IP_POST_ROUTING
343			    | 1 << NF_IP_LOCAL_OUT)) ||
344		       (h->info.valid_hooks
345			== (1 << NF_IP_PRE_ROUTING
346			    | 1 << NF_IP_LOCAL_IN
347			    | 1 << NF_IP_POST_ROUTING
348			    | 1 << NF_IP_LOCAL_OUT)));
349
350		assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
351
352		n = get_chain_end(h, 0);
353
354		n += get_entry(h, n)->next_offset;
355		assert(h->info.hook_entry[NF_IP_POST_ROUTING] == n);
356		n = get_chain_end(h, n);
357
358		n += get_entry(h, n)->next_offset;
359		assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
360		user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
361
362		if (h->info.valid_hooks & (1 << NF_IP_LOCAL_IN)) {
363			n = get_chain_end(h, n);
364			n += get_entry(h, n)->next_offset;
365			assert(h->info.hook_entry[NF_IP_LOCAL_IN] == n);
366			user_offset = h->info.hook_entry[NF_IP_LOCAL_IN];
367		}
368
369	} else if (strcmp(h->info.name, "mangle") == 0) {
370		/* This code is getting ugly because linux < 2.4.18-pre6 had
371		 * two mangle hooks, linux >= 2.4.18-pre6 has five mangle hooks
372		 * */
373		assert((h->info.valid_hooks
374			== (1 << NF_IP_PRE_ROUTING
375			    | 1 << NF_IP_LOCAL_OUT)) ||
376		       (h->info.valid_hooks
377			== (1 << NF_IP_PRE_ROUTING
378			    | 1 << NF_IP_LOCAL_IN
379			    | 1 << NF_IP_FORWARD
380			    | 1 << NF_IP_LOCAL_OUT
381			    | 1 << NF_IP_POST_ROUTING)));
382
383		/* Hooks should be first five */
384		assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
385
386		n = get_chain_end(h, 0);
387
388		if (h->info.valid_hooks & (1 << NF_IP_LOCAL_IN)) {
389			n += get_entry(h, n)->next_offset;
390			assert(h->info.hook_entry[NF_IP_LOCAL_IN] == n);
391			n = get_chain_end(h, n);
392		}
393
394		if (h->info.valid_hooks & (1 << NF_IP_FORWARD)) {
395			n += get_entry(h, n)->next_offset;
396			assert(h->info.hook_entry[NF_IP_FORWARD] == n);
397			n = get_chain_end(h, n);
398		}
399
400		n += get_entry(h, n)->next_offset;
401		assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
402		user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
403
404		if (h->info.valid_hooks & (1 << NF_IP_POST_ROUTING)) {
405			n = get_chain_end(h, n);
406			n += get_entry(h, n)->next_offset;
407			assert(h->info.hook_entry[NF_IP_POST_ROUTING] == n);
408			user_offset = h->info.hook_entry[NF_IP_POST_ROUTING];
409		}
410	} else if (strcmp(h->info.name, "raw") == 0) {
411		assert(h->info.valid_hooks
412		       == (1 << NF_IP_PRE_ROUTING
413			   | 1 << NF_IP_LOCAL_OUT));
414
415		/* Hooks should be first three */
416		assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
417
418		n = get_chain_end(h, n);
419		n += get_entry(h, n)->next_offset;
420		assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
421
422		user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
423	} else {
424		fprintf(stderr, "Unknown table `%s'\n", h->info.name);
425		abort();
426	}
427
428	/* User chain == end of last builtin + policy entry */
429	user_offset = get_chain_end(h, user_offset);
430	user_offset += get_entry(h, user_offset)->next_offset;
431
432	/* Overflows should be end of entry chains, and unconditional
433           policy nodes. */
434	for (i = 0; i < NUMHOOKS; i++) {
435		STRUCT_ENTRY *e;
436		STRUCT_STANDARD_TARGET *t;
437
438		if (!(h->info.valid_hooks & (1 << i)))
439			continue;
440		assert(h->info.underflow[i]
441		       == get_chain_end(h, h->info.hook_entry[i]));
442
443		e = get_entry(h, get_chain_end(h, h->info.hook_entry[i]));
444		assert(unconditional(&e->ip));
445		assert(e->target_offset == sizeof(*e));
446		t = (STRUCT_STANDARD_TARGET *)GET_TARGET(e);
447		assert(t->target.u.target_size == ALIGN(sizeof(*t)));
448		assert(e->next_offset == sizeof(*e) + ALIGN(sizeof(*t)));
449
450		assert(strcmp(t->target.u.user.name, STANDARD_TARGET)==0);
451		assert(t->verdict == -NF_DROP-1 || t->verdict == -NF_ACCEPT-1);
452
453		/* Hooks and underflows must be valid entries */
454		entry2index(h, get_entry(h, h->info.hook_entry[i]));
455		entry2index(h, get_entry(h, h->info.underflow[i]));
456	}
457
458	assert(h->info.size
459	       >= h->info.num_entries * (sizeof(STRUCT_ENTRY)
460					 +sizeof(STRUCT_STANDARD_TARGET)));
461
462	assert(h->entries.size
463	       >= (h->new_number
464		   * (sizeof(STRUCT_ENTRY)
465		      + sizeof(STRUCT_STANDARD_TARGET))));
466	assert(strcmp(h->info.name, h->entries.name) == 0);
467
468	i = 0; n = 0;
469	was_return = 0;
470	/* Check all the entries. */
471	ENTRY_ITERATE(h->entries.entrytable, h->entries.size,
472		      check_entry, &i, &n, user_offset, &was_return, h);
473
474	assert(i == h->new_number);
475	assert(n == h->entries.size);
476
477	/* Final entry must be error node */
478	assert(strcmp(GET_TARGET(index2entry(h, h->new_number-1))
479		      ->u.user.name,
480		      ERROR_TARGET) == 0);
481}
482#endif /*IPTC_DEBUG*/
483
484#endif
485