libip6t_ipv6header.c revision 997045f536026c0d643bf884da5ff5de2605197f 
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 <ip6tables.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 v%s 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	IPTABLES_VERSION);
148}
149
150static const struct option ipv6header_opts[] = {
151	{ "header", 1, NULL, '1' },
152	{ "soft", 0, NULL, '2' },
153	{ }
154};
155
156static void ipv6header_init(struct xt_entry_match *m)
157{
158	struct ip6t_ipv6header_info *info = (struct ip6t_ipv6header_info *)m->data;
159
160	info->matchflags = 0x00;
161	info->invflags = 0x00;
162	info->modeflag = 0x00;
163}
164
165static unsigned int
166parse_header(const char *flags) {
167        unsigned int ret = 0;
168        char *ptr;
169        char *buffer;
170
171        buffer = strdup(flags);
172
173        for (ptr = strtok(buffer, ","); ptr; ptr = strtok(NULL, ","))
174		ret |= add_proto_to_mask(name_to_proto(ptr));
175
176        free(buffer);
177        return ret;
178}
179
180#define IPV6_HDR_HEADER	0x01
181#define IPV6_HDR_SOFT	0x02
182
183/* Parses command options; returns 0 if it ate an option */
184static int
185ipv6header_parse(int c, char **argv, int invert, unsigned int *flags,
186                 const void *entry, struct xt_entry_match **match)
187{
188	struct ip6t_ipv6header_info *info = (struct ip6t_ipv6header_info *)(*match)->data;
189
190	switch (c) {
191		case '1' :
192			/* Parse the provided header names */
193			if (*flags & IPV6_HDR_HEADER)
194				exit_error(PARAMETER_PROBLEM,
195					"Only one `--header' allowed");
196
197			check_inverse(optarg, &invert, &optind, 0);
198
199			if (! (info->matchflags = parse_header(argv[optind-1])) )
200				exit_error(PARAMETER_PROBLEM, "ip6t_ipv6header: cannot parse header names");
201
202			if (invert)
203				info->invflags |= 0xFF;
204			*flags |= IPV6_HDR_HEADER;
205			break;
206		case '2' :
207			/* Soft-mode requested? */
208			if (*flags & IPV6_HDR_SOFT)
209				exit_error(PARAMETER_PROBLEM,
210					"Only one `--soft' allowed");
211
212			info->modeflag |= 0xFF;
213			*flags |= IPV6_HDR_SOFT;
214			break;
215		default:
216			return 0;
217	}
218
219	return 1;
220}
221
222/* Checks the flags variable */
223static void ipv6header_check(unsigned int flags)
224{
225	if (!flags) exit_error(PARAMETER_PROBLEM, "ip6t_ipv6header: no options specified");
226}
227
228static void
229print_header(u_int8_t flags){
230        int have_flag = 0;
231
232        while (flags) {
233                unsigned int i;
234
235                for (i = 0; (flags & chain_flags[i].flag) == 0; i++);
236
237                if (have_flag)
238                        printf(",");
239
240                printf("%s", proto_to_name(chain_flags[i].proto,0));
241                have_flag = 1;
242
243                flags &= ~chain_flags[i].flag;
244        }
245
246        if (!have_flag)
247                printf("NONE");
248}
249
250/* Prints out the match */
251static void ipv6header_print(const void *ip,
252                             const struct xt_entry_match *match, int numeric)
253{
254	const struct ip6t_ipv6header_info *info = (const struct ip6t_ipv6header_info *)match->data;
255	printf("ipv6header ");
256
257        if (info->matchflags || info->invflags) {
258                printf("flags:%s", info->invflags ? "!" : "");
259                if (numeric)
260                        printf("0x%02X ", info->matchflags);
261                else {
262                        print_header(info->matchflags);
263                        printf(" ");
264                }
265        }
266
267	if (info->modeflag)
268		printf("soft ");
269
270	return;
271}
272
273/* Saves the match */
274static void ipv6header_save(const void *ip, const struct xt_entry_match *match)
275{
276
277	const struct ip6t_ipv6header_info *info = (const struct ip6t_ipv6header_info *)match->data;
278
279	printf("--header ");
280	printf("%s", info->invflags ? "!" : "");
281	print_header(info->matchflags);
282	printf(" ");
283	if (info->modeflag)
284		printf("--soft ");
285
286	return;
287}
288
289static struct ip6tables_match ipv6header_match6 = {
290	.name		= "ipv6header",
291	.version	= IPTABLES_VERSION,
292	.size		= IP6T_ALIGN(sizeof(struct ip6t_ipv6header_info)),
293	.userspacesize	= IP6T_ALIGN(sizeof(struct ip6t_ipv6header_info)),
294	.help		= ipv6header_help,
295	.init		= ipv6header_init,
296	.parse		= ipv6header_parse,
297	.final_check	= ipv6header_check,
298	.print		= ipv6header_print,
299	.save		= ipv6header_save,
300	.extra_opts	= ipv6header_opts,
301};
302
303void _init(void)
304{
305	register_match6(&ipv6header_match6);
306}
307