libip4tc.c revision 7ac405297ec38449b30e3b05fd6bf2082fd3d803 
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_DELETE_ENTRY		iptc_delete_entry
80#define TC_DELETE_NUM_ENTRY	iptc_delete_num_entry
81#define TC_FLUSH_ENTRIES	iptc_flush_entries
82#define TC_ZERO_ENTRIES		iptc_zero_entries
83#define TC_READ_COUNTER		iptc_read_counter
84#define TC_ZERO_COUNTER		iptc_zero_counter
85#define TC_SET_COUNTER		iptc_set_counter
86#define TC_CREATE_CHAIN		iptc_create_chain
87#define TC_GET_REFERENCES	iptc_get_references
88#define TC_DELETE_CHAIN		iptc_delete_chain
89#define TC_RENAME_CHAIN		iptc_rename_chain
90#define TC_SET_POLICY		iptc_set_policy
91#define TC_GET_RAW_SOCKET	iptc_get_raw_socket
92#define TC_INIT			iptc_init
93#define TC_FREE			iptc_free
94#define TC_COMMIT		iptc_commit
95#define TC_STRERROR		iptc_strerror
96#define TC_NUM_RULES		iptc_num_rules
97#define TC_GET_RULE		iptc_get_rule
98
99#define TC_AF			AF_INET
100#define TC_IPPROTO		IPPROTO_IP
101
102#define SO_SET_REPLACE		IPT_SO_SET_REPLACE
103#define SO_SET_ADD_COUNTERS	IPT_SO_SET_ADD_COUNTERS
104#define SO_GET_INFO		IPT_SO_GET_INFO
105#define SO_GET_ENTRIES		IPT_SO_GET_ENTRIES
106#define SO_GET_VERSION		IPT_SO_GET_VERSION
107
108#define STANDARD_TARGET		IPT_STANDARD_TARGET
109#define LABEL_RETURN		IPTC_LABEL_RETURN
110#define LABEL_ACCEPT		IPTC_LABEL_ACCEPT
111#define LABEL_DROP		IPTC_LABEL_DROP
112#define LABEL_QUEUE		IPTC_LABEL_QUEUE
113
114#define ALIGN			IPT_ALIGN
115#define RETURN			IPT_RETURN
116
117#include "libiptc.c"
118
119#define IP_PARTS_NATIVE(n)			\
120(unsigned int)((n)>>24)&0xFF,			\
121(unsigned int)((n)>>16)&0xFF,			\
122(unsigned int)((n)>>8)&0xFF,			\
123(unsigned int)((n)&0xFF)
124
125#define IP_PARTS(n) IP_PARTS_NATIVE(ntohl(n))
126
127static int
128dump_entry(struct ipt_entry *e, struct iptc_handle *const handle)
129{
130	size_t i;
131	STRUCT_ENTRY_TARGET *t;
132
133	printf("Entry %u (%lu):\n", iptcb_entry2index(handle, e),
134	       iptcb_entry2offset(handle, e));
135	printf("SRC IP: %u.%u.%u.%u/%u.%u.%u.%u\n",
136	       IP_PARTS(e->ip.src.s_addr),IP_PARTS(e->ip.smsk.s_addr));
137	printf("DST IP: %u.%u.%u.%u/%u.%u.%u.%u\n",
138	       IP_PARTS(e->ip.dst.s_addr),IP_PARTS(e->ip.dmsk.s_addr));
139	printf("Interface: `%s'/", e->ip.iniface);
140	for (i = 0; i < IFNAMSIZ; i++)
141		printf("%c", e->ip.iniface_mask[i] ? 'X' : '.');
142	printf("to `%s'/", e->ip.outiface);
143	for (i = 0; i < IFNAMSIZ; i++)
144		printf("%c", e->ip.outiface_mask[i] ? 'X' : '.');
145	printf("\nProtocol: %u\n", e->ip.proto);
146	printf("Flags: %02X\n", e->ip.flags);
147	printf("Invflags: %02X\n", e->ip.invflags);
148	printf("Counters: %llu packets, %llu bytes\n",
149	       (unsigned long long)e->counters.pcnt, (unsigned long long)e->counters.bcnt);
150	printf("Cache: %08X\n", e->nfcache);
151
152	IPT_MATCH_ITERATE(e, print_match);
153
154	t = GET_TARGET(e);
155	printf("Target name: `%s' [%u]\n", t->u.user.name, t->u.target_size);
156	if (strcmp(t->u.user.name, STANDARD_TARGET) == 0) {
157		const unsigned char *data = t->data;
158		int pos = *(const int *)data;
159		if (pos < 0)
160			printf("verdict=%s\n",
161			       pos == -NF_ACCEPT-1 ? "NF_ACCEPT"
162			       : pos == -NF_DROP-1 ? "NF_DROP"
163			       : pos == -NF_QUEUE-1 ? "NF_QUEUE"
164			       : pos == RETURN ? "RETURN"
165			       : "UNKNOWN");
166		else
167			printf("verdict=%u\n", pos);
168	} else if (strcmp(t->u.user.name, IPT_ERROR_TARGET) == 0)
169		printf("error=`%s'\n", t->data);
170
171	printf("\n");
172	return 0;
173}
174
175static unsigned char *
176is_same(const STRUCT_ENTRY *a, const STRUCT_ENTRY *b, unsigned char *matchmask)
177{
178	unsigned int i;
179	unsigned char *mptr;
180
181	/* Always compare head structures: ignore mask here. */
182	if (a->ip.src.s_addr != b->ip.src.s_addr
183	    || a->ip.dst.s_addr != b->ip.dst.s_addr
184	    || a->ip.smsk.s_addr != b->ip.smsk.s_addr
185	    || a->ip.dmsk.s_addr != b->ip.dmsk.s_addr
186	    || a->ip.proto != b->ip.proto
187	    || a->ip.flags != b->ip.flags
188	    || a->ip.invflags != b->ip.invflags)
189		return NULL;
190
191	for (i = 0; i < IFNAMSIZ; i++) {
192		if (a->ip.iniface_mask[i] != b->ip.iniface_mask[i])
193			return NULL;
194		if ((a->ip.iniface[i] & a->ip.iniface_mask[i])
195		    != (b->ip.iniface[i] & b->ip.iniface_mask[i]))
196			return NULL;
197		if (a->ip.outiface_mask[i] != b->ip.outiface_mask[i])
198			return NULL;
199		if ((a->ip.outiface[i] & a->ip.outiface_mask[i])
200		    != (b->ip.outiface[i] & b->ip.outiface_mask[i]))
201			return NULL;
202	}
203
204	if (a->target_offset != b->target_offset
205	    || a->next_offset != b->next_offset)
206		return NULL;
207
208	mptr = matchmask + sizeof(STRUCT_ENTRY);
209	if (IPT_MATCH_ITERATE(a, match_different, a->elems, b->elems, &mptr))
210		return NULL;
211	mptr += IPT_ALIGN(sizeof(struct ipt_entry_target));
212
213	return mptr;
214}
215
216#if 0
217/***************************** DEBUGGING ********************************/
218static inline int
219unconditional(const struct ipt_ip *ip)
220{
221	unsigned int i;
222
223	for (i = 0; i < sizeof(*ip)/sizeof(uint32_t); i++)
224		if (((uint32_t *)ip)[i])
225			return 0;
226
227	return 1;
228}
229
230static inline int
231check_match(const STRUCT_ENTRY_MATCH *m, unsigned int *off)
232{
233	assert(m->u.match_size >= sizeof(STRUCT_ENTRY_MATCH));
234	assert(ALIGN(m->u.match_size) == m->u.match_size);
235
236	(*off) += m->u.match_size;
237	return 0;
238}
239
240static inline int
241check_entry(const STRUCT_ENTRY *e, unsigned int *i, unsigned int *off,
242	    unsigned int user_offset, int *was_return,
243	    struct iptc_handle *h)
244{
245	unsigned int toff;
246	STRUCT_STANDARD_TARGET *t;
247
248	assert(e->target_offset >= sizeof(STRUCT_ENTRY));
249	assert(e->next_offset >= e->target_offset
250	       + sizeof(STRUCT_ENTRY_TARGET));
251	toff = sizeof(STRUCT_ENTRY);
252	IPT_MATCH_ITERATE(e, check_match, &toff);
253
254	assert(toff == e->target_offset);
255
256	t = (STRUCT_STANDARD_TARGET *)
257		GET_TARGET((STRUCT_ENTRY *)e);
258	/* next_offset will have to be multiple of entry alignment. */
259	assert(e->next_offset == ALIGN(e->next_offset));
260	assert(e->target_offset == ALIGN(e->target_offset));
261	assert(t->target.u.target_size == ALIGN(t->target.u.target_size));
262	assert(!TC_IS_CHAIN(t->target.u.user.name, h));
263
264	if (strcmp(t->target.u.user.name, STANDARD_TARGET) == 0) {
265		assert(t->target.u.target_size
266		       == ALIGN(sizeof(STRUCT_STANDARD_TARGET)));
267
268		assert(t->verdict == -NF_DROP-1
269		       || t->verdict == -NF_ACCEPT-1
270		       || t->verdict == RETURN
271		       || t->verdict < (int)h->entries->size);
272
273		if (t->verdict >= 0) {
274			STRUCT_ENTRY *te = get_entry(h, t->verdict);
275			int idx;
276
277			idx = iptcb_entry2index(h, te);
278			assert(strcmp(GET_TARGET(te)->u.user.name,
279				      IPT_ERROR_TARGET)
280			       != 0);
281			assert(te != e);
282
283			/* Prior node must be error node, or this node. */
284			assert(t->verdict == iptcb_entry2offset(h, e)+e->next_offset
285			       || strcmp(GET_TARGET(index2entry(h, idx-1))
286					 ->u.user.name, IPT_ERROR_TARGET)
287			       == 0);
288		}
289
290		if (t->verdict == RETURN
291		    && unconditional(&e->ip)
292		    && e->target_offset == sizeof(*e))
293			*was_return = 1;
294		else
295			*was_return = 0;
296	} else if (strcmp(t->target.u.user.name, IPT_ERROR_TARGET) == 0) {
297		assert(t->target.u.target_size
298		       == ALIGN(sizeof(struct ipt_error_target)));
299
300		/* If this is in user area, previous must have been return */
301		if (*off > user_offset)
302			assert(*was_return);
303
304		*was_return = 0;
305	}
306	else *was_return = 0;
307
308	if (*off == user_offset)
309		assert(strcmp(t->target.u.user.name, IPT_ERROR_TARGET) == 0);
310
311	(*off) += e->next_offset;
312	(*i)++;
313	return 0;
314}
315
316#ifdef IPTC_DEBUG
317/* Do every conceivable sanity check on the handle */
318static void
319do_check(struct iptc_handle *h, unsigned int line)
320{
321	unsigned int i, n;
322	unsigned int user_offset; /* Offset of first user chain */
323	int was_return;
324
325	assert(h->changed == 0 || h->changed == 1);
326	if (strcmp(h->info.name, "filter") == 0) {
327		assert(h->info.valid_hooks
328		       == (1 << NF_IP_LOCAL_IN
329			   | 1 << NF_IP_FORWARD
330			   | 1 << NF_IP_LOCAL_OUT));
331
332		/* Hooks should be first three */
333		assert(h->info.hook_entry[NF_IP_LOCAL_IN] == 0);
334
335		n = get_chain_end(h, 0);
336		n += get_entry(h, n)->next_offset;
337		assert(h->info.hook_entry[NF_IP_FORWARD] == n);
338
339		n = get_chain_end(h, n);
340		n += get_entry(h, n)->next_offset;
341		assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
342
343		user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
344	} else if (strcmp(h->info.name, "nat") == 0) {
345		assert((h->info.valid_hooks
346		        == (1 << NF_IP_PRE_ROUTING
347			    | 1 << NF_IP_POST_ROUTING
348			    | 1 << NF_IP_LOCAL_OUT)) ||
349		       (h->info.valid_hooks
350			== (1 << NF_IP_PRE_ROUTING
351			    | 1 << NF_IP_LOCAL_IN
352			    | 1 << NF_IP_POST_ROUTING
353			    | 1 << NF_IP_LOCAL_OUT)));
354
355		assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
356
357		n = get_chain_end(h, 0);
358
359		n += get_entry(h, n)->next_offset;
360		assert(h->info.hook_entry[NF_IP_POST_ROUTING] == n);
361		n = get_chain_end(h, n);
362
363		n += get_entry(h, n)->next_offset;
364		assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
365		user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
366
367		if (h->info.valid_hooks & (1 << NF_IP_LOCAL_IN)) {
368			n = get_chain_end(h, n);
369			n += get_entry(h, n)->next_offset;
370			assert(h->info.hook_entry[NF_IP_LOCAL_IN] == n);
371			user_offset = h->info.hook_entry[NF_IP_LOCAL_IN];
372		}
373
374	} else if (strcmp(h->info.name, "mangle") == 0) {
375		/* This code is getting ugly because linux < 2.4.18-pre6 had
376		 * two mangle hooks, linux >= 2.4.18-pre6 has five mangle hooks
377		 * */
378		assert((h->info.valid_hooks
379			== (1 << NF_IP_PRE_ROUTING
380			    | 1 << NF_IP_LOCAL_OUT)) ||
381		       (h->info.valid_hooks
382			== (1 << NF_IP_PRE_ROUTING
383			    | 1 << NF_IP_LOCAL_IN
384			    | 1 << NF_IP_FORWARD
385			    | 1 << NF_IP_LOCAL_OUT
386			    | 1 << NF_IP_POST_ROUTING)));
387
388		/* Hooks should be first five */
389		assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
390
391		n = get_chain_end(h, 0);
392
393		if (h->info.valid_hooks & (1 << NF_IP_LOCAL_IN)) {
394			n += get_entry(h, n)->next_offset;
395			assert(h->info.hook_entry[NF_IP_LOCAL_IN] == n);
396			n = get_chain_end(h, n);
397		}
398
399		if (h->info.valid_hooks & (1 << NF_IP_FORWARD)) {
400			n += get_entry(h, n)->next_offset;
401			assert(h->info.hook_entry[NF_IP_FORWARD] == n);
402			n = get_chain_end(h, n);
403		}
404
405		n += get_entry(h, n)->next_offset;
406		assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
407		user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
408
409		if (h->info.valid_hooks & (1 << NF_IP_POST_ROUTING)) {
410			n = get_chain_end(h, n);
411			n += get_entry(h, n)->next_offset;
412			assert(h->info.hook_entry[NF_IP_POST_ROUTING] == n);
413			user_offset = h->info.hook_entry[NF_IP_POST_ROUTING];
414		}
415	} else if (strcmp(h->info.name, "raw") == 0) {
416		assert(h->info.valid_hooks
417		       == (1 << NF_IP_PRE_ROUTING
418			   | 1 << NF_IP_LOCAL_OUT));
419
420		/* Hooks should be first three */
421		assert(h->info.hook_entry[NF_IP_PRE_ROUTING] == 0);
422
423		n = get_chain_end(h, n);
424		n += get_entry(h, n)->next_offset;
425		assert(h->info.hook_entry[NF_IP_LOCAL_OUT] == n);
426
427		user_offset = h->info.hook_entry[NF_IP_LOCAL_OUT];
428
429#ifdef NF_IP_DROPPING
430	} else if (strcmp(h->info.name, "drop") == 0) {
431		assert(h->info.valid_hooks == (1 << NF_IP_DROPPING));
432
433		/* Hook should be first */
434		assert(h->info.hook_entry[NF_IP_DROPPING] == 0);
435		user_offset = 0;
436#endif
437	} else {
438		fprintf(stderr, "Unknown table `%s'\n", h->info.name);
439		abort();
440	}
441
442	/* User chain == end of last builtin + policy entry */
443	user_offset = get_chain_end(h, user_offset);
444	user_offset += get_entry(h, user_offset)->next_offset;
445
446	/* Overflows should be end of entry chains, and unconditional
447           policy nodes. */
448	for (i = 0; i < NUMHOOKS; i++) {
449		STRUCT_ENTRY *e;
450		STRUCT_STANDARD_TARGET *t;
451
452		if (!(h->info.valid_hooks & (1 << i)))
453			continue;
454		assert(h->info.underflow[i]
455		       == get_chain_end(h, h->info.hook_entry[i]));
456
457		e = get_entry(h, get_chain_end(h, h->info.hook_entry[i]));
458		assert(unconditional(&e->ip));
459		assert(e->target_offset == sizeof(*e));
460		t = (STRUCT_STANDARD_TARGET *)GET_TARGET(e);
461		assert(t->target.u.target_size == ALIGN(sizeof(*t)));
462		assert(e->next_offset == sizeof(*e) + ALIGN(sizeof(*t)));
463
464		assert(strcmp(t->target.u.user.name, STANDARD_TARGET)==0);
465		assert(t->verdict == -NF_DROP-1 || t->verdict == -NF_ACCEPT-1);
466
467		/* Hooks and underflows must be valid entries */
468		entry2index(h, get_entry(h, h->info.hook_entry[i]));
469		entry2index(h, get_entry(h, h->info.underflow[i]));
470	}
471
472	assert(h->info.size
473	       >= h->info.num_entries * (sizeof(STRUCT_ENTRY)
474					 +sizeof(STRUCT_STANDARD_TARGET)));
475
476	assert(h->entries.size
477	       >= (h->new_number
478		   * (sizeof(STRUCT_ENTRY)
479		      + sizeof(STRUCT_STANDARD_TARGET))));
480	assert(strcmp(h->info.name, h->entries.name) == 0);
481
482	i = 0; n = 0;
483	was_return = 0;
484	/* Check all the entries. */
485	ENTRY_ITERATE(h->entries.entrytable, h->entries.size,
486		      check_entry, &i, &n, user_offset, &was_return, h);
487
488	assert(i == h->new_number);
489	assert(n == h->entries.size);
490
491	/* Final entry must be error node */
492	assert(strcmp(GET_TARGET(index2entry(h, h->new_number-1))
493		      ->u.user.name,
494		      ERROR_TARGET) == 0);
495}
496#endif /*IPTC_DEBUG*/
497
498#endif
499