libipt_icmp.c revision 967279231a9ecfa99f26694a954afc535c63db1d 
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 <iptables.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
100/* Function which prints out usage message. */
101static void icmp_help(void)
102{
103	printf(
104"icmp match options:\n"
105"[!] --icmp-type typename	match icmp type\n"
106"				(or numeric type or type/code)\n");
107	print_icmptypes();
108}
109
110static const struct option icmp_opts[] = {
111	{ "icmp-type", 1, NULL, '1' },
112	{ .name = NULL }
113};
114
115static void
116parse_icmp(const char *icmptype, u_int8_t *type, u_int8_t code[])
117{
118	unsigned int limit = sizeof(icmp_codes)/sizeof(struct icmp_names);
119	unsigned int match = limit;
120	unsigned int i;
121
122	for (i = 0; i < limit; i++) {
123		if (strncasecmp(icmp_codes[i].name, icmptype, strlen(icmptype))
124		    == 0) {
125			if (match != limit)
126				exit_error(PARAMETER_PROBLEM,
127					   "Ambiguous ICMP type `%s':"
128					   " `%s' or `%s'?",
129					   icmptype,
130					   icmp_codes[match].name,
131					   icmp_codes[i].name);
132			match = i;
133		}
134	}
135
136	if (match != limit) {
137		*type = icmp_codes[match].type;
138		code[0] = icmp_codes[match].code_min;
139		code[1] = icmp_codes[match].code_max;
140	} else {
141		char *slash;
142		char buffer[strlen(icmptype) + 1];
143		unsigned int number;
144
145		strcpy(buffer, icmptype);
146		slash = strchr(buffer, '/');
147
148		if (slash)
149			*slash = '\0';
150
151		if (string_to_number(buffer, 0, 255, &number) == -1)
152			exit_error(PARAMETER_PROBLEM,
153				   "Invalid ICMP type `%s'\n", buffer);
154		*type = number;
155		if (slash) {
156			if (string_to_number(slash+1, 0, 255, &number) == -1)
157				exit_error(PARAMETER_PROBLEM,
158					   "Invalid ICMP code `%s'\n",
159					   slash+1);
160			code[0] = code[1] = number;
161		} else {
162			code[0] = 0;
163			code[1] = 0xFF;
164		}
165	}
166}
167
168/* Initialize the match. */
169static void icmp_init(struct xt_entry_match *m)
170{
171	struct ipt_icmp *icmpinfo = (struct ipt_icmp *)m->data;
172
173	icmpinfo->type = 0xFF;
174	icmpinfo->code[1] = 0xFF;
175}
176
177/* Function which parses command options; returns true if it
178   ate an option */
179static int icmp_parse(int c, char **argv, int invert, unsigned int *flags,
180                      const void *entry, struct xt_entry_match **match)
181{
182	struct ipt_icmp *icmpinfo = (struct ipt_icmp *)(*match)->data;
183
184	switch (c) {
185	case '1':
186		if (*flags == 1)
187			exit_error(PARAMETER_PROBLEM,
188				   "icmp match: only use --icmp-type once!");
189		check_inverse(optarg, &invert, &optind, 0);
190		parse_icmp(argv[optind-1], &icmpinfo->type,
191			   icmpinfo->code);
192		if (invert)
193			icmpinfo->invflags |= IPT_ICMP_INV;
194		*flags = 1;
195		break;
196
197	default:
198		return 0;
199	}
200
201	return 1;
202}
203
204static void print_icmptype(u_int8_t type,
205			   u_int8_t code_min, u_int8_t code_max,
206			   int invert,
207			   int numeric)
208{
209	if (!numeric) {
210		unsigned int i;
211
212		for (i = 0;
213		     i < sizeof(icmp_codes)/sizeof(struct icmp_names);
214		     i++) {
215			if (icmp_codes[i].type == type
216			    && icmp_codes[i].code_min == code_min
217			    && icmp_codes[i].code_max == code_max)
218				break;
219		}
220
221		if (i != sizeof(icmp_codes)/sizeof(struct icmp_names)) {
222			printf("%s%s ",
223			       invert ? "!" : "",
224			       icmp_codes[i].name);
225			return;
226		}
227	}
228
229	if (invert)
230		printf("!");
231
232	printf("type %u", type);
233	if (code_min == 0 && code_max == 0xFF)
234		printf(" ");
235	else if (code_min == code_max)
236		printf(" code %u ", code_min);
237	else
238		printf(" codes %u-%u ", code_min, code_max);
239}
240
241/* Prints out the union ipt_matchinfo. */
242static void icmp_print(const void *ip, const struct xt_entry_match *match,
243                       int numeric)
244{
245	const struct ipt_icmp *icmp = (struct ipt_icmp *)match->data;
246
247	printf("icmp ");
248	print_icmptype(icmp->type, icmp->code[0], icmp->code[1],
249		       icmp->invflags & IPT_ICMP_INV,
250		       numeric);
251
252	if (icmp->invflags & ~IPT_ICMP_INV)
253		printf("Unknown invflags: 0x%X ",
254		       icmp->invflags & ~IPT_ICMP_INV);
255}
256
257/* Saves the match in parsable form to stdout. */
258static void icmp_save(const void *ip, const struct xt_entry_match *match)
259{
260	const struct ipt_icmp *icmp = (struct ipt_icmp *)match->data;
261
262	if (icmp->invflags & IPT_ICMP_INV)
263		printf("! ");
264
265	/* special hack for 'any' case */
266	if (icmp->type == 0xFF) {
267		printf("--icmp-type any ");
268	} else {
269		printf("--icmp-type %u", icmp->type);
270		if (icmp->code[0] != 0 || icmp->code[1] != 0xFF)
271			printf("/%u", icmp->code[0]);
272		printf(" ");
273	}
274}
275
276static struct xtables_match icmp_mt_reg = {
277	.name		= "icmp",
278	.version	= XTABLES_VERSION,
279	.family		= PF_INET,
280	.size		= XT_ALIGN(sizeof(struct ipt_icmp)),
281	.userspacesize	= XT_ALIGN(sizeof(struct ipt_icmp)),
282	.help		= icmp_help,
283	.init		= icmp_init,
284	.parse		= icmp_parse,
285	.print		= icmp_print,
286	.save		= icmp_save,
287	.extra_opts	= icmp_opts,
288};
289
290void _init(void)
291{
292	xtables_register_match(&icmp_mt_reg);
293}
294