libip6t_ipv6header.c revision 825c317eedc12e1c8c93e22a96bc423d27b3c1f4 
1/* ipv6header match - matches IPv6 packets based
2on whether they contain certain headers */
3
4/* Original idea: Brad Chapman
5 * Rewritten by: Andras Kis-Szabo <kisza@sch.bme.hu> */
6
7#include <getopt.h>
8#include <xtables.h>
9#include <stddef.h>
10#include <stdio.h>
11#include <stdlib.h>
12#include <string.h>
13#include <netdb.h>
14#include <sys/types.h>
15
16#include <linux/netfilter_ipv6/ip6_tables.h>
17#include <linux/netfilter_ipv6/ip6t_ipv6header.h>
18
19/* This maybe required
20#include <linux/in.h>
21#include <linux/in6.h>
22*/
23
24
25/* A few hardcoded protocols for 'all' and in case the user has no
26 *    /etc/protocols */
27struct pprot {
28	char *name;
29	u_int8_t num;
30};
31
32struct numflag {
33	u_int8_t proto;
34	u_int8_t flag;
35};
36
37static const struct pprot chain_protos[] = {
38	{ "hop-by-hop", IPPROTO_HOPOPTS },
39	{ "protocol", IPPROTO_RAW },
40	{ "hop", IPPROTO_HOPOPTS },
41	{ "dst", IPPROTO_DSTOPTS },
42	{ "route", IPPROTO_ROUTING },
43	{ "frag", IPPROTO_FRAGMENT },
44	{ "auth", IPPROTO_AH },
45	{ "esp", IPPROTO_ESP },
46	{ "none", IPPROTO_NONE },
47	{ "prot", IPPROTO_RAW },
48	{ "0", IPPROTO_HOPOPTS },
49	{ "60", IPPROTO_DSTOPTS },
50	{ "43", IPPROTO_ROUTING },
51	{ "44", IPPROTO_FRAGMENT },
52	{ "51", IPPROTO_AH },
53	{ "50", IPPROTO_ESP },
54	{ "59", IPPROTO_NONE },
55	{ "255", IPPROTO_RAW },
56	/* { "all", 0 }, */
57};
58
59static const struct numflag chain_flags[] = {
60	{ IPPROTO_HOPOPTS, MASK_HOPOPTS },
61	{ IPPROTO_DSTOPTS, MASK_DSTOPTS },
62	{ IPPROTO_ROUTING, MASK_ROUTING },
63	{ IPPROTO_FRAGMENT, MASK_FRAGMENT },
64	{ IPPROTO_AH, MASK_AH },
65	{ IPPROTO_ESP, MASK_ESP },
66	{ IPPROTO_NONE, MASK_NONE },
67	{ IPPROTO_RAW, MASK_PROTO },
68};
69
70static char *
71proto_to_name(u_int8_t proto, int nolookup)
72{
73        unsigned int i;
74
75        if (proto && !nolookup) {
76                struct protoent *pent = getprotobynumber(proto);
77                if (pent)
78                        return pent->p_name;
79        }
80
81        for (i = 0; i < sizeof(chain_protos)/sizeof(struct pprot); i++)
82                if (chain_protos[i].num == proto)
83                        return chain_protos[i].name;
84
85        return NULL;
86}
87
88static u_int16_t
89name_to_proto(const char *s)
90{
91        unsigned int proto=0;
92        struct protoent *pent;
93
94        if ((pent = getprotobyname(s)))
95        	proto = pent->p_proto;
96        else {
97        	unsigned int i;
98        	for (i = 0;
99        		i < sizeof(chain_protos)/sizeof(struct pprot);
100        		i++) {
101        		if (strcmp(s, chain_protos[i].name) == 0) {
102        			proto = chain_protos[i].num;
103        			break;
104        		}
105        	}
106
107        	if (i == sizeof(chain_protos)/sizeof(struct pprot))
108        		exit_error(PARAMETER_PROBLEM,
109        			"unknown header `%s' specified",
110        			s);
111        }
112
113        return (u_int16_t)proto;
114}
115
116static unsigned int
117add_proto_to_mask(int proto){
118	unsigned int i=0, flag=0;
119
120	for (i = 0;
121		i < sizeof(chain_flags)/sizeof(struct numflag);
122		i++) {
123			if (proto == chain_flags[i].proto){
124				flag = chain_flags[i].flag;
125				break;
126			}
127	}
128
129	if (i == sizeof(chain_flags)/sizeof(struct numflag))
130		exit_error(PARAMETER_PROBLEM,
131		"unknown header `%d' specified",
132		proto);
133
134	return flag;
135}
136
137static void ipv6header_help(void)
138{
139	printf(
140"ipv6header match options:\n"
141"[!] --header headers     Type of header to match, by name\n"
142"                         names: hop,dst,route,frag,auth,esp,none,proto\n"
143"                    long names: hop-by-hop,ipv6-opts,ipv6-route,\n"
144"                                ipv6-frag,ah,esp,ipv6-nonxt,protocol\n"
145"                       numbers: 0,60,43,44,51,50,59\n"
146"--soft                    The header CONTAINS the specified extensions\n");
147}
148
149static const struct option ipv6header_opts[] = {
150	{ "header", 1, NULL, '1' },
151	{ "soft", 0, NULL, '2' },
152	{ .name = NULL }
153};
154
155static void ipv6header_init(struct xt_entry_match *m)
156{
157	struct ip6t_ipv6header_info *info = (struct ip6t_ipv6header_info *)m->data;
158
159	info->matchflags = 0x00;
160	info->invflags = 0x00;
161	info->modeflag = 0x00;
162}
163
164static unsigned int
165parse_header(const char *flags) {
166        unsigned int ret = 0;
167        char *ptr;
168        char *buffer;
169
170        buffer = strdup(flags);
171
172        for (ptr = strtok(buffer, ","); ptr; ptr = strtok(NULL, ","))
173		ret |= add_proto_to_mask(name_to_proto(ptr));
174
175        free(buffer);
176        return ret;
177}
178
179#define IPV6_HDR_HEADER	0x01
180#define IPV6_HDR_SOFT	0x02
181
182static int
183ipv6header_parse(int c, char **argv, int invert, unsigned int *flags,
184                 const void *entry, struct xt_entry_match **match)
185{
186	struct ip6t_ipv6header_info *info = (struct ip6t_ipv6header_info *)(*match)->data;
187
188	switch (c) {
189		case '1' :
190			/* Parse the provided header names */
191			if (*flags & IPV6_HDR_HEADER)
192				exit_error(PARAMETER_PROBLEM,
193					"Only one `--header' allowed");
194
195			check_inverse(optarg, &invert, &optind, 0);
196
197			if (! (info->matchflags = parse_header(argv[optind-1])) )
198				exit_error(PARAMETER_PROBLEM, "ip6t_ipv6header: cannot parse header names");
199
200			if (invert)
201				info->invflags |= 0xFF;
202			*flags |= IPV6_HDR_HEADER;
203			break;
204		case '2' :
205			/* Soft-mode requested? */
206			if (*flags & IPV6_HDR_SOFT)
207				exit_error(PARAMETER_PROBLEM,
208					"Only one `--soft' allowed");
209
210			info->modeflag |= 0xFF;
211			*flags |= IPV6_HDR_SOFT;
212			break;
213		default:
214			return 0;
215	}
216
217	return 1;
218}
219
220static void ipv6header_check(unsigned int flags)
221{
222	if (!flags) exit_error(PARAMETER_PROBLEM, "ip6t_ipv6header: no options specified");
223}
224
225static void
226print_header(u_int8_t flags){
227        int have_flag = 0;
228
229        while (flags) {
230                unsigned int i;
231
232                for (i = 0; (flags & chain_flags[i].flag) == 0; i++);
233
234                if (have_flag)
235                        printf(",");
236
237                printf("%s", proto_to_name(chain_flags[i].proto,0));
238                have_flag = 1;
239
240                flags &= ~chain_flags[i].flag;
241        }
242
243        if (!have_flag)
244                printf("NONE");
245}
246
247static void ipv6header_print(const void *ip,
248                             const struct xt_entry_match *match, int numeric)
249{
250	const struct ip6t_ipv6header_info *info = (const struct ip6t_ipv6header_info *)match->data;
251	printf("ipv6header ");
252
253        if (info->matchflags || info->invflags) {
254                printf("flags:%s", info->invflags ? "!" : "");
255                if (numeric)
256                        printf("0x%02X ", info->matchflags);
257                else {
258                        print_header(info->matchflags);
259                        printf(" ");
260                }
261        }
262
263	if (info->modeflag)
264		printf("soft ");
265}
266
267static void ipv6header_save(const void *ip, const struct xt_entry_match *match)
268{
269
270	const struct ip6t_ipv6header_info *info = (const struct ip6t_ipv6header_info *)match->data;
271
272	printf("%s--header ", info->invflags ? "! " : "");
273	print_header(info->matchflags);
274	printf(" ");
275	if (info->modeflag)
276		printf("--soft ");
277}
278
279static struct xtables_match ipv6header_mt6_reg = {
280	.name		= "ipv6header",
281	.version	= XTABLES_VERSION,
282	.family		= NFPROTO_IPV6,
283	.size		= XT_ALIGN(sizeof(struct ip6t_ipv6header_info)),
284	.userspacesize	= XT_ALIGN(sizeof(struct ip6t_ipv6header_info)),
285	.help		= ipv6header_help,
286	.init		= ipv6header_init,
287	.parse		= ipv6header_parse,
288	.final_check	= ipv6header_check,
289	.print		= ipv6header_print,
290	.save		= ipv6header_save,
291	.extra_opts	= ipv6header_opts,
292};
293
294void _init(void)
295{
296	xtables_register_match(&ipv6header_mt6_reg);
297}
298