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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 #include <arpa/inet.h>
21 
22 #ifdef DEBUG_CONNTRACK
23 #define inline
24 #endif
25 
26 #if !defined(__ANDROID__) && (!defined(__GLIBC__) || (__GLIBC__ < 2))
27 typedef unsigned int socklen_t;
28 #endif
29 
30 #include "libiptc/libip6tc.h"
31 
32 #define HOOK_PRE_ROUTING	NF_IP6_PRE_ROUTING
33 #define HOOK_LOCAL_IN		NF_IP6_LOCAL_IN
34 #define HOOK_FORWARD		NF_IP6_FORWARD
35 #define HOOK_LOCAL_OUT		NF_IP6_LOCAL_OUT
36 #define HOOK_POST_ROUTING	NF_IP6_POST_ROUTING
37 
38 #define STRUCT_ENTRY_TARGET	struct xt_entry_target
39 #define STRUCT_ENTRY		struct ip6t_entry
40 #define STRUCT_ENTRY_MATCH	struct xt_entry_match
41 #define STRUCT_GETINFO		struct ip6t_getinfo
42 #define STRUCT_GET_ENTRIES	struct ip6t_get_entries
43 #define STRUCT_COUNTERS		struct xt_counters
44 #define STRUCT_COUNTERS_INFO	struct xt_counters_info
45 #define STRUCT_STANDARD_TARGET	struct xt_standard_target
46 #define STRUCT_REPLACE		struct ip6t_replace
47 
48 #define ENTRY_ITERATE		IP6T_ENTRY_ITERATE
49 #define TABLE_MAXNAMELEN	XT_TABLE_MAXNAMELEN
50 #define FUNCTION_MAXNAMELEN	XT_FUNCTION_MAXNAMELEN
51 
52 #define GET_TARGET		ip6t_get_target
53 
54 #define ERROR_TARGET		XT_ERROR_TARGET
55 #define NUMHOOKS		NF_IP6_NUMHOOKS
56 
57 #define IPT_CHAINLABEL		xt_chainlabel
58 
59 #define TC_DUMP_ENTRIES		dump_entries6
60 #define TC_IS_CHAIN		ip6tc_is_chain
61 #define TC_FIRST_CHAIN		ip6tc_first_chain
62 #define TC_NEXT_CHAIN		ip6tc_next_chain
63 #define TC_FIRST_RULE		ip6tc_first_rule
64 #define TC_NEXT_RULE		ip6tc_next_rule
65 #define TC_GET_TARGET		ip6tc_get_target
66 #define TC_BUILTIN		ip6tc_builtin
67 #define TC_GET_POLICY		ip6tc_get_policy
68 #define TC_INSERT_ENTRY		ip6tc_insert_entry
69 #define TC_REPLACE_ENTRY	ip6tc_replace_entry
70 #define TC_APPEND_ENTRY		ip6tc_append_entry
71 #define TC_CHECK_ENTRY		ip6tc_check_entry
72 #define TC_DELETE_ENTRY		ip6tc_delete_entry
73 #define TC_DELETE_NUM_ENTRY	ip6tc_delete_num_entry
74 #define TC_FLUSH_ENTRIES	ip6tc_flush_entries
75 #define TC_ZERO_ENTRIES		ip6tc_zero_entries
76 #define TC_ZERO_COUNTER		ip6tc_zero_counter
77 #define TC_READ_COUNTER		ip6tc_read_counter
78 #define TC_SET_COUNTER		ip6tc_set_counter
79 #define TC_CREATE_CHAIN		ip6tc_create_chain
80 #define TC_GET_REFERENCES	ip6tc_get_references
81 #define TC_DELETE_CHAIN		ip6tc_delete_chain
82 #define TC_RENAME_CHAIN		ip6tc_rename_chain
83 #define TC_SET_POLICY		ip6tc_set_policy
84 #define TC_GET_RAW_SOCKET	ip6tc_get_raw_socket
85 #define TC_INIT			ip6tc_init
86 #define TC_FREE			ip6tc_free
87 #define TC_COMMIT		ip6tc_commit
88 #define TC_STRERROR		ip6tc_strerror
89 #define TC_NUM_RULES		ip6tc_num_rules
90 #define TC_GET_RULE		ip6tc_get_rule
91 #define TC_OPS			ip6tc_ops
92 
93 #define TC_AF			AF_INET6
94 #define TC_IPPROTO		IPPROTO_IPV6
95 
96 #define SO_SET_REPLACE		IP6T_SO_SET_REPLACE
97 #define SO_SET_ADD_COUNTERS	IP6T_SO_SET_ADD_COUNTERS
98 #define SO_GET_INFO		IP6T_SO_GET_INFO
99 #define SO_GET_ENTRIES		IP6T_SO_GET_ENTRIES
100 #define SO_GET_VERSION		IP6T_SO_GET_VERSION
101 
102 #define STANDARD_TARGET		XT_STANDARD_TARGET
103 #define LABEL_RETURN		IP6TC_LABEL_RETURN
104 #define LABEL_ACCEPT		IP6TC_LABEL_ACCEPT
105 #define LABEL_DROP		IP6TC_LABEL_DROP
106 #define LABEL_QUEUE		IP6TC_LABEL_QUEUE
107 
108 #define ALIGN			XT_ALIGN
109 #define RETURN			XT_RETURN
110 
111 #include "libiptc.c"
112 
113 #define BIT6(a, l) \
114  ((ntohl(a->s6_addr32[(l) / 32]) >> (31 - ((l) & 31))) & 1)
115 
116 static int
ipv6_prefix_length(const struct in6_addr * a)117 ipv6_prefix_length(const struct in6_addr *a)
118 {
119 	int l, i;
120 	for (l = 0; l < 128; l++) {
121 		if (BIT6(a, l) == 0)
122 			break;
123 	}
124 	for (i = l + 1; i < 128; i++) {
125 		if (BIT6(a, i) == 1)
126 			return -1;
127 	}
128 	return l;
129 }
130 
131 static int
dump_entry(struct ip6t_entry * e,struct xtc_handle * const handle)132 dump_entry(struct ip6t_entry *e, struct xtc_handle *const handle)
133 {
134 	size_t i;
135 	char buf[40];
136 	int len;
137 	struct xt_entry_target *t;
138 
139 	printf("Entry %u (%lu):\n", iptcb_entry2index(handle, e),
140 	       iptcb_entry2offset(handle, e));
141 	puts("SRC IP: ");
142 	inet_ntop(AF_INET6, &e->ipv6.src, buf, sizeof buf);
143 	puts(buf);
144 	putchar('/');
145 	len = ipv6_prefix_length(&e->ipv6.smsk);
146 	if (len != -1)
147 		printf("%d", len);
148 	else {
149 		inet_ntop(AF_INET6, &e->ipv6.smsk, buf, sizeof buf);
150 		puts(buf);
151 	}
152 	putchar('\n');
153 
154 	puts("DST IP: ");
155 	inet_ntop(AF_INET6, &e->ipv6.dst, buf, sizeof buf);
156 	puts(buf);
157 	putchar('/');
158 	len = ipv6_prefix_length(&e->ipv6.dmsk);
159 	if (len != -1)
160 		printf("%d", len);
161 	else {
162 		inet_ntop(AF_INET6, &e->ipv6.dmsk, buf, sizeof buf);
163 		puts(buf);
164 	}
165 	putchar('\n');
166 
167 	printf("Interface: `%s'/", e->ipv6.iniface);
168 	for (i = 0; i < IFNAMSIZ; i++)
169 		printf("%c", e->ipv6.iniface_mask[i] ? 'X' : '.');
170 	printf("to `%s'/", e->ipv6.outiface);
171 	for (i = 0; i < IFNAMSIZ; i++)
172 		printf("%c", e->ipv6.outiface_mask[i] ? 'X' : '.');
173 	printf("\nProtocol: %u\n", e->ipv6.proto);
174 	if (e->ipv6.flags & IP6T_F_TOS)
175 		printf("TOS: %u\n", e->ipv6.tos);
176 	printf("Flags: %02X\n", e->ipv6.flags);
177 	printf("Invflags: %02X\n", e->ipv6.invflags);
178 	printf("Counters: %llu packets, %llu bytes\n",
179 	       (unsigned long long)e->counters.pcnt, (unsigned long long)e->counters.bcnt);
180 	printf("Cache: %08X\n", e->nfcache);
181 
182 	IP6T_MATCH_ITERATE(e, print_match);
183 
184 	t = ip6t_get_target(e);
185 	printf("Target name: `%s' [%u]\n", t->u.user.name, t->u.target_size);
186 	if (strcmp(t->u.user.name, XT_STANDARD_TARGET) == 0) {
187 		const unsigned char *data = t->data;
188 		int pos = *(const int *)data;
189 		if (pos < 0)
190 			printf("verdict=%s\n",
191 			       pos == -NF_ACCEPT-1 ? "NF_ACCEPT"
192 			       : pos == -NF_DROP-1 ? "NF_DROP"
193 			       : pos == XT_RETURN ? "RETURN"
194 			       : "UNKNOWN");
195 		else
196 			printf("verdict=%u\n", pos);
197 	} else if (strcmp(t->u.user.name, XT_ERROR_TARGET) == 0)
198 		printf("error=`%s'\n", t->data);
199 
200 	printf("\n");
201 	return 0;
202 }
203 
204 static unsigned char *
is_same(const STRUCT_ENTRY * a,const STRUCT_ENTRY * b,unsigned char * matchmask)205 is_same(const STRUCT_ENTRY *a, const STRUCT_ENTRY *b,
206 	unsigned char *matchmask)
207 {
208 	unsigned int i;
209 	unsigned char *mptr;
210 
211 	/* Always compare head structures: ignore mask here. */
212 	if (memcmp(&a->ipv6.src, &b->ipv6.src, sizeof(struct in6_addr))
213 	    || memcmp(&a->ipv6.dst, &b->ipv6.dst, sizeof(struct in6_addr))
214 	    || memcmp(&a->ipv6.smsk, &b->ipv6.smsk, sizeof(struct in6_addr))
215 	    || memcmp(&a->ipv6.dmsk, &b->ipv6.dmsk, sizeof(struct in6_addr))
216 	    || a->ipv6.proto != b->ipv6.proto
217 	    || a->ipv6.tos != b->ipv6.tos
218 	    || a->ipv6.flags != b->ipv6.flags
219 	    || a->ipv6.invflags != b->ipv6.invflags)
220 		return NULL;
221 
222 	for (i = 0; i < IFNAMSIZ; i++) {
223 		if (a->ipv6.iniface_mask[i] != b->ipv6.iniface_mask[i])
224 			return NULL;
225 		if ((a->ipv6.iniface[i] & a->ipv6.iniface_mask[i])
226 		    != (b->ipv6.iniface[i] & b->ipv6.iniface_mask[i]))
227 			return NULL;
228 		if (a->ipv6.outiface_mask[i] != b->ipv6.outiface_mask[i])
229 			return NULL;
230 		if ((a->ipv6.outiface[i] & a->ipv6.outiface_mask[i])
231 		    != (b->ipv6.outiface[i] & b->ipv6.outiface_mask[i]))
232 			return NULL;
233 	}
234 
235 	if (a->target_offset != b->target_offset
236 	    || a->next_offset != b->next_offset)
237 		return NULL;
238 
239 	mptr = matchmask + sizeof(STRUCT_ENTRY);
240 	if (IP6T_MATCH_ITERATE(a, match_different, a->elems, b->elems, &mptr))
241 		return NULL;
242 	mptr += XT_ALIGN(sizeof(struct xt_entry_target));
243 
244 	return mptr;
245 }
246 
247 /* All zeroes == unconditional rule. */
248 static inline int
unconditional(const struct ip6t_ip6 * ipv6)249 unconditional(const struct ip6t_ip6 *ipv6)
250 {
251 	unsigned int i;
252 
253 	for (i = 0; i < sizeof(*ipv6); i++)
254 		if (((char *)ipv6)[i])
255 			break;
256 
257 	return (i == sizeof(*ipv6));
258 }
259 
260 #ifdef IPTC_DEBUG
261 /* Do every conceivable sanity check on the handle */
262 static void
do_check(struct xtc_handle * h,unsigned int line)263 do_check(struct xtc_handle *h, unsigned int line)
264 {
265 	unsigned int i, n;
266 	unsigned int user_offset; /* Offset of first user chain */
267 	int was_return;
268 
269 	assert(h->changed == 0 || h->changed == 1);
270 	if (strcmp(h->info.name, "filter") == 0) {
271 		assert(h->info.valid_hooks
272 		       == (1 << NF_IP6_LOCAL_IN
273 			   | 1 << NF_IP6_FORWARD
274 			   | 1 << NF_IP6_LOCAL_OUT));
275 
276 		/* Hooks should be first three */
277 		assert(h->info.hook_entry[NF_IP6_LOCAL_IN] == 0);
278 
279 		n = get_chain_end(h, 0);
280 		n += get_entry(h, n)->next_offset;
281 		assert(h->info.hook_entry[NF_IP6_FORWARD] == n);
282 
283 		n = get_chain_end(h, n);
284 		n += get_entry(h, n)->next_offset;
285 		assert(h->info.hook_entry[NF_IP6_LOCAL_OUT] == n);
286 
287 		user_offset = h->info.hook_entry[NF_IP6_LOCAL_OUT];
288 	} else if (strcmp(h->info.name, "nat") == 0) {
289 		assert((h->info.valid_hooks
290 			== (1 << NF_IP6_PRE_ROUTING
291 			    | 1 << NF_IP6_LOCAL_OUT
292 			    | 1 << NF_IP6_POST_ROUTING)) ||
293 		       (h->info.valid_hooks
294 			== (1 << NF_IP6_PRE_ROUTING
295 			    | 1 << NF_IP6_LOCAL_IN
296 			    | 1 << NF_IP6_LOCAL_OUT
297 			    | 1 << NF_IP6_POST_ROUTING)));
298 
299 		assert(h->info.hook_entry[NF_IP6_PRE_ROUTING] == 0);
300 
301 		n = get_chain_end(h, 0);
302 
303 		n += get_entry(h, n)->next_offset;
304 		assert(h->info.hook_entry[NF_IP6_POST_ROUTING] == n);
305 		n = get_chain_end(h, n);
306 
307 		n += get_entry(h, n)->next_offset;
308 		assert(h->info.hook_entry[NF_IP6_LOCAL_OUT] == n);
309 		user_offset = h->info.hook_entry[NF_IP6_LOCAL_OUT];
310 
311 		if (h->info.valid_hooks & (1 << NF_IP6_LOCAL_IN)) {
312 			n = get_chain_end(h, n);
313 			n += get_entry(h, n)->next_offset;
314 			assert(h->info.hook_entry[NF_IP6_LOCAL_IN] == n);
315 			user_offset = h->info.hook_entry[NF_IP6_LOCAL_IN];
316 		}
317 
318 	} else if (strcmp(h->info.name, "mangle") == 0) {
319 		/* This code is getting ugly because linux < 2.4.18-pre6 had
320 		 * two mangle hooks, linux >= 2.4.18-pre6 has five mangle hooks
321 		 * */
322 		assert((h->info.valid_hooks
323 			== (1 << NF_IP6_PRE_ROUTING
324 			    | 1 << NF_IP6_LOCAL_OUT)) ||
325 		       (h->info.valid_hooks
326 			== (1 << NF_IP6_PRE_ROUTING
327 			    | 1 << NF_IP6_LOCAL_IN
328 			    | 1 << NF_IP6_FORWARD
329 			    | 1 << NF_IP6_LOCAL_OUT
330 			    | 1 << NF_IP6_POST_ROUTING)));
331 
332 		/* Hooks should be first five */
333 		assert(h->info.hook_entry[NF_IP6_PRE_ROUTING] == 0);
334 
335 		n = get_chain_end(h, 0);
336 
337 		if (h->info.valid_hooks & (1 << NF_IP6_LOCAL_IN)) {
338 			n += get_entry(h, n)->next_offset;
339 			assert(h->info.hook_entry[NF_IP6_LOCAL_IN] == n);
340 			n = get_chain_end(h, n);
341 		}
342 
343 		if (h->info.valid_hooks & (1 << NF_IP6_FORWARD)) {
344 			n += get_entry(h, n)->next_offset;
345 			assert(h->info.hook_entry[NF_IP6_FORWARD] == n);
346 			n = get_chain_end(h, n);
347 		}
348 
349 		n += get_entry(h, n)->next_offset;
350 		assert(h->info.hook_entry[NF_IP6_LOCAL_OUT] == n);
351 		user_offset = h->info.hook_entry[NF_IP6_LOCAL_OUT];
352 
353 		if (h->info.valid_hooks & (1 << NF_IP6_POST_ROUTING)) {
354 			n = get_chain_end(h, n);
355 			n += get_entry(h, n)->next_offset;
356 			assert(h->info.hook_entry[NF_IP6_POST_ROUTING] == n);
357 			user_offset = h->info.hook_entry[NF_IP6_POST_ROUTING];
358 		}
359 	} else if (strcmp(h->info.name, "raw") == 0) {
360 		assert(h->info.valid_hooks
361 		       == (1 << NF_IP6_PRE_ROUTING
362 			   | 1 << NF_IP6_LOCAL_OUT));
363 
364 		/* Hooks should be first three */
365 		assert(h->info.hook_entry[NF_IP6_PRE_ROUTING] == 0);
366 
367 		n = get_chain_end(h, n);
368 		n += get_entry(h, n)->next_offset;
369 		assert(h->info.hook_entry[NF_IP6_LOCAL_OUT] == n);
370 
371 		user_offset = h->info.hook_entry[NF_IP6_LOCAL_OUT];
372 	} else {
373                 fprintf(stderr, "Unknown table `%s'\n", h->info.name);
374 		abort();
375 	}
376 
377 	/* User chain == end of last builtin + policy entry */
378 	user_offset = get_chain_end(h, user_offset);
379 	user_offset += get_entry(h, user_offset)->next_offset;
380 
381 	/* Overflows should be end of entry chains, and unconditional
382            policy nodes. */
383 	for (i = 0; i < NUMHOOKS; i++) {
384 		STRUCT_ENTRY *e;
385 		STRUCT_STANDARD_TARGET *t;
386 
387 		if (!(h->info.valid_hooks & (1 << i)))
388 			continue;
389 		assert(h->info.underflow[i]
390 		       == get_chain_end(h, h->info.hook_entry[i]));
391 
392 		e = get_entry(h, get_chain_end(h, h->info.hook_entry[i]));
393 		assert(unconditional(&e->ipv6));
394 		assert(e->target_offset == sizeof(*e));
395 		t = (STRUCT_STANDARD_TARGET *)GET_TARGET(e);
396 		printf("target_size=%u, align=%u\n",
397 			t->target.u.target_size, ALIGN(sizeof(*t)));
398 		assert(t->target.u.target_size == ALIGN(sizeof(*t)));
399 		assert(e->next_offset == sizeof(*e) + ALIGN(sizeof(*t)));
400 
401 		assert(strcmp(t->target.u.user.name, STANDARD_TARGET)==0);
402 		assert(t->verdict == -NF_DROP-1 || t->verdict == -NF_ACCEPT-1);
403 
404 		/* Hooks and underflows must be valid entries */
405 		iptcb_entry2index(h, get_entry(h, h->info.hook_entry[i]));
406 		iptcb_entry2index(h, get_entry(h, h->info.underflow[i]));
407 	}
408 
409 	assert(h->info.size
410 	       >= h->info.num_entries * (sizeof(STRUCT_ENTRY)
411 					 +sizeof(STRUCT_STANDARD_TARGET)));
412 
413 	assert(h->entries.size
414 	       >= (h->new_number
415 		   * (sizeof(STRUCT_ENTRY)
416 		      + sizeof(STRUCT_STANDARD_TARGET))));
417 	assert(strcmp(h->info.name, h->entries.name) == 0);
418 
419 	i = 0; n = 0;
420 	was_return = 0;
421 
422 #if 0
423 	/* Check all the entries. */
424 	ENTRY_ITERATE(h->entries.entrytable, h->entries.size,
425 		      check_entry, &i, &n, user_offset, &was_return, h);
426 
427 	assert(i == h->new_number);
428 	assert(n == h->entries.size);
429 
430 	/* Final entry must be error node */
431 	assert(strcmp(GET_TARGET(index2entry(h, h->new_number-1))
432 		      ->u.user.name,
433 		      ERROR_TARGET) == 0);
434 #endif
435 }
436 #endif /*IPTC_DEBUG*/
437