libipt_icmp.c revision 1829ed482efbc8b390cc760d012b3a4450494e1a 
1/* Shared library add-on to iptables to add ICMP support. */
2#include <stdio.h>
3#include <netdb.h>
4#include <string.h>
5#include <stdlib.h>
6#include <getopt.h>
7#include <xtables.h>
8#include <linux/netfilter_ipv4/ip_tables.h>
9
10/* special hack for icmp-type 'any':
11 * Up to kernel <=2.4.20 the problem was:
12 * '-p icmp ' matches all icmp packets
13 * '-p icmp -m icmp' matches _only_ ICMP type 0 :(
14 * This is now fixed by initializing the field * to icmp type 0xFF
15 * See: https://bugzilla.netfilter.org/cgi-bin/bugzilla/show_bug.cgi?id=37
16 */
17
18struct icmp_names {
19	const char *name;
20	u_int8_t type;
21	u_int8_t code_min, code_max;
22};
23
24static const struct icmp_names icmp_codes[] = {
25	{ "any", 0xFF, 0, 0xFF },
26	{ "echo-reply", 0, 0, 0xFF },
27	/* Alias */ { "pong", 0, 0, 0xFF },
28
29	{ "destination-unreachable", 3, 0, 0xFF },
30	{   "network-unreachable", 3, 0, 0 },
31	{   "host-unreachable", 3, 1, 1 },
32	{   "protocol-unreachable", 3, 2, 2 },
33	{   "port-unreachable", 3, 3, 3 },
34	{   "fragmentation-needed", 3, 4, 4 },
35	{   "source-route-failed", 3, 5, 5 },
36	{   "network-unknown", 3, 6, 6 },
37	{   "host-unknown", 3, 7, 7 },
38	{   "network-prohibited", 3, 9, 9 },
39	{   "host-prohibited", 3, 10, 10 },
40	{   "TOS-network-unreachable", 3, 11, 11 },
41	{   "TOS-host-unreachable", 3, 12, 12 },
42	{   "communication-prohibited", 3, 13, 13 },
43	{   "host-precedence-violation", 3, 14, 14 },
44	{   "precedence-cutoff", 3, 15, 15 },
45
46	{ "source-quench", 4, 0, 0xFF },
47
48	{ "redirect", 5, 0, 0xFF },
49	{   "network-redirect", 5, 0, 0 },
50	{   "host-redirect", 5, 1, 1 },
51	{   "TOS-network-redirect", 5, 2, 2 },
52	{   "TOS-host-redirect", 5, 3, 3 },
53
54	{ "echo-request", 8, 0, 0xFF },
55	/* Alias */ { "ping", 8, 0, 0xFF },
56
57	{ "router-advertisement", 9, 0, 0xFF },
58
59	{ "router-solicitation", 10, 0, 0xFF },
60
61	{ "time-exceeded", 11, 0, 0xFF },
62	/* Alias */ { "ttl-exceeded", 11, 0, 0xFF },
63	{   "ttl-zero-during-transit", 11, 0, 0 },
64	{   "ttl-zero-during-reassembly", 11, 1, 1 },
65
66	{ "parameter-problem", 12, 0, 0xFF },
67	{   "ip-header-bad", 12, 0, 0 },
68	{   "required-option-missing", 12, 1, 1 },
69
70	{ "timestamp-request", 13, 0, 0xFF },
71
72	{ "timestamp-reply", 14, 0, 0xFF },
73
74	{ "address-mask-request", 17, 0, 0xFF },
75
76	{ "address-mask-reply", 18, 0, 0xFF }
77};
78
79static void
80print_icmptypes(void)
81{
82	unsigned int i;
83	printf("Valid ICMP Types:");
84
85	for (i = 0; i < sizeof(icmp_codes)/sizeof(struct icmp_names); i++) {
86		if (i && icmp_codes[i].type == icmp_codes[i-1].type) {
87			if (icmp_codes[i].code_min == icmp_codes[i-1].code_min
88			    && (icmp_codes[i].code_max
89				== icmp_codes[i-1].code_max))
90				printf(" (%s)", icmp_codes[i].name);
91			else
92				printf("\n   %s", icmp_codes[i].name);
93		}
94		else
95			printf("\n%s", icmp_codes[i].name);
96	}
97	printf("\n");
98}
99
100static void icmp_help(void)
101{
102	printf(
103"icmp match options:\n"
104"[!] --icmp-type typename	match icmp type\n"
105"[!] --icmp-type type[/code]	(or numeric type or type/code)\n");
106	print_icmptypes();
107}
108
109static const struct option icmp_opts[] = {
110	{ "icmp-type", 1, NULL, '1' },
111	{ .name = NULL }
112};
113
114static void
115parse_icmp(const char *icmptype, u_int8_t *type, u_int8_t code[])
116{
117	unsigned int limit = sizeof(icmp_codes)/sizeof(struct icmp_names);
118	unsigned int match = limit;
119	unsigned int i;
120
121	for (i = 0; i < limit; i++) {
122		if (strncasecmp(icmp_codes[i].name, icmptype, strlen(icmptype))
123		    == 0) {
124			if (match != limit)
125				xtables_error(PARAMETER_PROBLEM,
126					   "Ambiguous ICMP type `%s':"
127					   " `%s' or `%s'?",
128					   icmptype,
129					   icmp_codes[match].name,
130					   icmp_codes[i].name);
131			match = i;
132		}
133	}
134
135	if (match != limit) {
136		*type = icmp_codes[match].type;
137		code[0] = icmp_codes[match].code_min;
138		code[1] = icmp_codes[match].code_max;
139	} else {
140		char *slash;
141		char buffer[strlen(icmptype) + 1];
142		unsigned int number;
143
144		strcpy(buffer, icmptype);
145		slash = strchr(buffer, '/');
146
147		if (slash)
148			*slash = '\0';
149
150		if (!xtables_strtoui(buffer, NULL, &number, 0, UINT8_MAX))
151			xtables_error(PARAMETER_PROBLEM,
152				   "Invalid ICMP type `%s'\n", buffer);
153		*type = number;
154		if (slash) {
155			if (!xtables_strtoui(slash+1, NULL, &number, 0, UINT8_MAX))
156				xtables_error(PARAMETER_PROBLEM,
157					   "Invalid ICMP code `%s'\n",
158					   slash+1);
159			code[0] = code[1] = number;
160		} else {
161			code[0] = 0;
162			code[1] = 0xFF;
163		}
164	}
165}
166
167static void icmp_init(struct xt_entry_match *m)
168{
169	struct ipt_icmp *icmpinfo = (struct ipt_icmp *)m->data;
170
171	icmpinfo->type = 0xFF;
172	icmpinfo->code[1] = 0xFF;
173}
174
175static int icmp_parse(int c, char **argv, int invert, unsigned int *flags,
176                      const void *entry, struct xt_entry_match **match)
177{
178	struct ipt_icmp *icmpinfo = (struct ipt_icmp *)(*match)->data;
179
180	switch (c) {
181	case '1':
182		if (*flags == 1)
183			xtables_error(PARAMETER_PROBLEM,
184				   "icmp match: only use --icmp-type once!");
185		xtables_check_inverse(optarg, &invert, &optind, 0);
186		parse_icmp(argv[optind-1], &icmpinfo->type,
187			   icmpinfo->code);
188		if (invert)
189			icmpinfo->invflags |= IPT_ICMP_INV;
190		*flags = 1;
191		break;
192
193	default:
194		return 0;
195	}
196
197	return 1;
198}
199
200static void print_icmptype(u_int8_t type,
201			   u_int8_t code_min, u_int8_t code_max,
202			   int invert,
203			   int numeric)
204{
205	if (!numeric) {
206		unsigned int i;
207
208		for (i = 0;
209		     i < sizeof(icmp_codes)/sizeof(struct icmp_names);
210		     i++) {
211			if (icmp_codes[i].type == type
212			    && icmp_codes[i].code_min == code_min
213			    && icmp_codes[i].code_max == code_max)
214				break;
215		}
216
217		if (i != sizeof(icmp_codes)/sizeof(struct icmp_names)) {
218			printf("%s%s ",
219			       invert ? "!" : "",
220			       icmp_codes[i].name);
221			return;
222		}
223	}
224
225	if (invert)
226		printf("!");
227
228	printf("type %u", type);
229	if (code_min == 0 && code_max == 0xFF)
230		printf(" ");
231	else if (code_min == code_max)
232		printf(" code %u ", code_min);
233	else
234		printf(" codes %u-%u ", code_min, code_max);
235}
236
237static void icmp_print(const void *ip, const struct xt_entry_match *match,
238                       int numeric)
239{
240	const struct ipt_icmp *icmp = (struct ipt_icmp *)match->data;
241
242	printf("icmp ");
243	print_icmptype(icmp->type, icmp->code[0], icmp->code[1],
244		       icmp->invflags & IPT_ICMP_INV,
245		       numeric);
246
247	if (icmp->invflags & ~IPT_ICMP_INV)
248		printf("Unknown invflags: 0x%X ",
249		       icmp->invflags & ~IPT_ICMP_INV);
250}
251
252static void icmp_save(const void *ip, const struct xt_entry_match *match)
253{
254	const struct ipt_icmp *icmp = (struct ipt_icmp *)match->data;
255
256	if (icmp->invflags & IPT_ICMP_INV)
257		printf("! ");
258
259	/* special hack for 'any' case */
260	if (icmp->type == 0xFF) {
261		printf("--icmp-type any ");
262	} else {
263		printf("--icmp-type %u", icmp->type);
264		if (icmp->code[0] != 0 || icmp->code[1] != 0xFF)
265			printf("/%u", icmp->code[0]);
266		printf(" ");
267	}
268}
269
270static struct xtables_match icmp_mt_reg = {
271	.name		= "icmp",
272	.version	= XTABLES_VERSION,
273	.family		= NFPROTO_IPV4,
274	.size		= XT_ALIGN(sizeof(struct ipt_icmp)),
275	.userspacesize	= XT_ALIGN(sizeof(struct ipt_icmp)),
276	.help		= icmp_help,
277	.init		= icmp_init,
278	.parse		= icmp_parse,
279	.print		= icmp_print,
280	.save		= icmp_save,
281	.extra_opts	= icmp_opts,
282};
283
284void _init(void)
285{
286	xtables_register_match(&icmp_mt_reg);
287}
288