libip6t_ipv6header.c revision 2c69b55e55f2efc5a334b87ccdceaa9de0ecb658 
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/ip6t_ipv6header.h>
17
18/* This maybe required
19#include <linux/in.h>
20#include <linux/in6.h>
21*/
22
23
24/* A few hardcoded protocols for 'all' and in case the user has no
25 *    /etc/protocols */
26struct pprot {
27	char *name;
28	u_int8_t num;
29};
30
31struct numflag {
32	u_int8_t proto;
33	u_int8_t flag;
34};
35
36static const struct pprot chain_protos[] = {
37	{ "hop-by-hop", IPPROTO_HOPOPTS },
38	{ "protocol", IPPROTO_RAW },
39	{ "hop", IPPROTO_HOPOPTS },
40	{ "dst", IPPROTO_DSTOPTS },
41	{ "route", IPPROTO_ROUTING },
42	{ "frag", IPPROTO_FRAGMENT },
43	{ "auth", IPPROTO_AH },
44	{ "esp", IPPROTO_ESP },
45	{ "none", IPPROTO_NONE },
46	{ "prot", IPPROTO_RAW },
47	{ "0", IPPROTO_HOPOPTS },
48	{ "60", IPPROTO_DSTOPTS },
49	{ "43", IPPROTO_ROUTING },
50	{ "44", IPPROTO_FRAGMENT },
51	{ "51", IPPROTO_AH },
52	{ "50", IPPROTO_ESP },
53	{ "59", IPPROTO_NONE },
54	{ "255", IPPROTO_RAW },
55	/* { "all", 0 }, */
56};
57
58static const struct numflag chain_flags[] = {
59	{ IPPROTO_HOPOPTS, MASK_HOPOPTS },
60	{ IPPROTO_DSTOPTS, MASK_DSTOPTS },
61	{ IPPROTO_ROUTING, MASK_ROUTING },
62	{ IPPROTO_FRAGMENT, MASK_FRAGMENT },
63	{ IPPROTO_AH, MASK_AH },
64	{ IPPROTO_ESP, MASK_ESP },
65	{ IPPROTO_NONE, MASK_NONE },
66	{ IPPROTO_RAW, MASK_PROTO },
67};
68
69static char *
70proto_to_name(u_int8_t proto, int nolookup)
71{
72        unsigned int i;
73
74        if (proto && !nolookup) {
75                struct protoent *pent = getprotobynumber(proto);
76                if (pent)
77                        return pent->p_name;
78        }
79
80        for (i = 0; i < ARRAY_SIZE(chain_protos); ++i)
81                if (chain_protos[i].num == proto)
82                        return chain_protos[i].name;
83
84        return NULL;
85}
86
87static u_int16_t
88name_to_proto(const char *s)
89{
90        unsigned int proto=0;
91        struct protoent *pent;
92
93        if ((pent = getprotobyname(s)))
94        	proto = pent->p_proto;
95        else {
96        	unsigned int i;
97        	for (i = 0; i < ARRAY_SIZE(chain_protos); ++i)
98        		if (strcmp(s, chain_protos[i].name) == 0) {
99        			proto = chain_protos[i].num;
100        			break;
101        		}
102
103		if (i == ARRAY_SIZE(chain_protos))
104			xtables_error(PARAMETER_PROBLEM,
105        			"unknown header `%s' specified",
106        			s);
107        }
108
109        return proto;
110}
111
112static unsigned int
113add_proto_to_mask(int proto){
114	unsigned int i=0, flag=0;
115
116	for (i = 0; i < ARRAY_SIZE(chain_flags); ++i)
117			if (proto == chain_flags[i].proto){
118				flag = chain_flags[i].flag;
119				break;
120			}
121
122	if (i == ARRAY_SIZE(chain_flags))
123		xtables_error(PARAMETER_PROBLEM,
124		"unknown header `%d' specified",
125		proto);
126
127	return flag;
128}
129
130static void ipv6header_help(void)
131{
132	printf(
133"ipv6header match options:\n"
134"[!] --header headers     Type of header to match, by name\n"
135"                         names: hop,dst,route,frag,auth,esp,none,proto\n"
136"                    long names: hop-by-hop,ipv6-opts,ipv6-route,\n"
137"                                ipv6-frag,ah,esp,ipv6-nonxt,protocol\n"
138"                       numbers: 0,60,43,44,51,50,59\n"
139"--soft                    The header CONTAINS the specified extensions\n");
140}
141
142static const struct option ipv6header_opts[] = {
143	{ "header", 1, NULL, '1' },
144	{ "soft", 0, NULL, '2' },
145	{ .name = NULL }
146};
147
148static void ipv6header_init(struct xt_entry_match *m)
149{
150	struct ip6t_ipv6header_info *info = (struct ip6t_ipv6header_info *)m->data;
151
152	info->matchflags = 0x00;
153	info->invflags = 0x00;
154	info->modeflag = 0x00;
155}
156
157static unsigned int
158parse_header(const char *flags) {
159        unsigned int ret = 0;
160        char *ptr;
161        char *buffer;
162
163        buffer = strdup(flags);
164
165        for (ptr = strtok(buffer, ","); ptr; ptr = strtok(NULL, ","))
166		ret |= add_proto_to_mask(name_to_proto(ptr));
167
168        free(buffer);
169        return ret;
170}
171
172#define IPV6_HDR_HEADER	0x01
173#define IPV6_HDR_SOFT	0x02
174
175static int
176ipv6header_parse(int c, char **argv, int invert, unsigned int *flags,
177                 const void *entry, struct xt_entry_match **match)
178{
179	struct ip6t_ipv6header_info *info = (struct ip6t_ipv6header_info *)(*match)->data;
180
181	switch (c) {
182		case '1' :
183			/* Parse the provided header names */
184			if (*flags & IPV6_HDR_HEADER)
185				xtables_error(PARAMETER_PROBLEM,
186					"Only one `--header' allowed");
187
188			xtables_check_inverse(optarg, &invert, &optind, 0);
189
190			if (! (info->matchflags = parse_header(argv[optind-1])) )
191				xtables_error(PARAMETER_PROBLEM, "ip6t_ipv6header: cannot parse header names");
192
193			if (invert)
194				info->invflags |= 0xFF;
195			*flags |= IPV6_HDR_HEADER;
196			break;
197		case '2' :
198			/* Soft-mode requested? */
199			if (*flags & IPV6_HDR_SOFT)
200				xtables_error(PARAMETER_PROBLEM,
201					"Only one `--soft' allowed");
202
203			info->modeflag |= 0xFF;
204			*flags |= IPV6_HDR_SOFT;
205			break;
206		default:
207			return 0;
208	}
209
210	return 1;
211}
212
213static void ipv6header_check(unsigned int flags)
214{
215	if (!flags) xtables_error(PARAMETER_PROBLEM, "ip6t_ipv6header: no options specified");
216}
217
218static void
219print_header(u_int8_t flags){
220        int have_flag = 0;
221
222        while (flags) {
223                unsigned int i;
224
225                for (i = 0; (flags & chain_flags[i].flag) == 0; i++);
226
227                if (have_flag)
228                        printf(",");
229
230                printf("%s", proto_to_name(chain_flags[i].proto,0));
231                have_flag = 1;
232
233                flags &= ~chain_flags[i].flag;
234        }
235
236        if (!have_flag)
237                printf("NONE");
238}
239
240static void ipv6header_print(const void *ip,
241                             const struct xt_entry_match *match, int numeric)
242{
243	const struct ip6t_ipv6header_info *info = (const struct ip6t_ipv6header_info *)match->data;
244	printf("ipv6header ");
245
246        if (info->matchflags || info->invflags) {
247                printf("flags:%s", info->invflags ? "!" : "");
248                if (numeric)
249                        printf("0x%02X ", info->matchflags);
250                else {
251                        print_header(info->matchflags);
252                        printf(" ");
253                }
254        }
255
256	if (info->modeflag)
257		printf("soft ");
258}
259
260static void ipv6header_save(const void *ip, const struct xt_entry_match *match)
261{
262
263	const struct ip6t_ipv6header_info *info = (const struct ip6t_ipv6header_info *)match->data;
264
265	printf("%s--header ", info->invflags ? "! " : "");
266	print_header(info->matchflags);
267	printf(" ");
268	if (info->modeflag)
269		printf("--soft ");
270}
271
272static struct xtables_match ipv6header_mt6_reg = {
273	.name		= "ipv6header",
274	.version	= XTABLES_VERSION,
275	.family		= NFPROTO_IPV6,
276	.size		= XT_ALIGN(sizeof(struct ip6t_ipv6header_info)),
277	.userspacesize	= XT_ALIGN(sizeof(struct ip6t_ipv6header_info)),
278	.help		= ipv6header_help,
279	.init		= ipv6header_init,
280	.parse		= ipv6header_parse,
281	.final_check	= ipv6header_check,
282	.print		= ipv6header_print,
283	.save		= ipv6header_save,
284	.extra_opts	= ipv6header_opts,
285};
286
287void _init(void)
288{
289	xtables_register_match(&ipv6header_mt6_reg);
290}
291