libipt_realm.c revision ecd48dd6ba534deea7fd4d0ce20c7b5c00f4128f 
1/* Shared library add-on to iptables to add realm matching support. */
2#include <stdio.h>
3#include <netdb.h>
4#include <string.h>
5#include <stdlib.h>
6#include <errno.h>
7#include <ctype.h>
8#include <getopt.h>
9#if defined(__GLIBC__) && __GLIBC__ == 2
10#include <net/ethernet.h>
11#else
12#include <linux/if_ether.h>
13#endif
14#include <xtables.h>
15#include <linux/netfilter_ipv4/ipt_realm.h>
16
17static void realm_help(void)
18{
19	printf(
20"realm match options:\n"
21"[!] --realm value[/mask]\n"
22"				Match realm\n");
23}
24
25static const struct option realm_opts[] = {
26	{ "realm", 1, NULL, '1' },
27	{ .name = NULL }
28};
29
30struct realmname {
31	int	id;
32	char*	name;
33	int	len;
34	struct realmname* next;
35};
36
37/* array of realms from /etc/iproute2/rt_realms */
38static struct realmname *realms = NULL;
39/* 1 if loading failed */
40static int rdberr = 0;
41
42
43static void load_realms(void)
44{
45	const char* rfnm = "/etc/iproute2/rt_realms";
46	char buf[512];
47	FILE *fil;
48	char *cur, *nxt;
49	int id;
50	struct realmname *oldnm = NULL, *newnm = NULL;
51
52	fil = fopen(rfnm, "r");
53	if (!fil) {
54		rdberr = 1;
55		return;
56	}
57
58	while (fgets(buf, sizeof(buf), fil)) {
59		cur = buf;
60		while ((*cur == ' ') || (*cur == '\t'))
61			cur++;
62		if ((*cur == '#') || (*cur == '\n') || (*cur == 0))
63			continue;
64
65		/* iproute2 allows hex and dec format */
66		errno = 0;
67		id = strtoul(cur, &nxt, strncmp(cur, "0x", 2) ? 10 : 16);
68		if ((nxt == cur) || errno)
69			continue;
70
71		/* same boundaries as in iproute2 */
72		if (id < 0 || id > 255)
73			continue;
74		cur = nxt;
75
76		if (!isspace(*cur))
77			continue;
78		while ((*cur == ' ') || (*cur == '\t'))
79			cur++;
80		if ((*cur == '#') || (*cur == '\n') || (*cur == 0))
81			continue;
82		nxt = cur;
83		while ((*nxt != 0) && !isspace(*nxt))
84			nxt++;
85		if (nxt == cur)
86			continue;
87
88		/* found valid data */
89		newnm = malloc(sizeof(struct realmname));
90		if (newnm == NULL) {
91			perror("libipt_realm: malloc failed");
92			exit(1);
93		}
94		newnm->id = id;
95		newnm->len = nxt - cur;
96		newnm->name = malloc(newnm->len + 1);
97		if (newnm->name == NULL) {
98			perror("libipt_realm: malloc failed");
99			exit(1);
100		}
101		strncpy(newnm->name, cur, newnm->len);
102		newnm->name[newnm->len] = 0;
103		newnm->next = NULL;
104
105		if (oldnm)
106			oldnm->next = newnm;
107		else
108			realms = newnm;
109		oldnm = newnm;
110	}
111
112	fclose(fil);
113}
114
115/* get realm id for name, -1 if error/not found */
116static int realm_name2id(const char* name)
117{
118	struct realmname* cur;
119
120	if ((realms == NULL) && (rdberr == 0))
121		load_realms();
122	cur = realms;
123	if (cur == NULL)
124		return -1;
125	while (cur) {
126		if (!strncmp(name, cur->name, cur->len + 1))
127			return cur->id;
128		cur = cur->next;
129	}
130	return -1;
131}
132
133/* get realm name for id, NULL if error/not found */
134static const char *realm_id2name(int id)
135{
136	struct realmname* cur;
137
138	if ((realms == NULL) && (rdberr == 0))
139		load_realms();
140	cur = realms;
141	if (cur == NULL)
142		return NULL;
143	while (cur) {
144		if (id == cur->id)
145			return cur->name;
146		cur = cur->next;
147	}
148	return NULL;
149}
150
151static int realm_parse(int c, char **argv, int invert, unsigned int *flags,
152                       const void *entry, struct xt_entry_match **match)
153{
154	struct ipt_realm_info *realminfo = (struct ipt_realm_info *)(*match)->data;
155	int id;
156
157	switch (c) {
158		char *end;
159	case '1':
160		xtables_check_inverse(argv[optind-1], &invert, &optind, 0);
161		end = optarg = argv[optind-1];
162		realminfo->id = strtoul(optarg, &end, 0);
163		if (end != optarg && (*end == '/' || *end == '\0')) {
164			if (*end == '/')
165				realminfo->mask = strtoul(end+1, &end, 0);
166			else
167				realminfo->mask = 0xffffffff;
168			if (*end != '\0' || end == optarg)
169				xtables_error(PARAMETER_PROBLEM,
170					   "Bad realm value `%s'", optarg);
171		} else {
172			id = realm_name2id(optarg);
173			if (id == -1)
174				xtables_error(PARAMETER_PROBLEM,
175					   "Realm `%s' not found", optarg);
176			realminfo->id = id;
177			realminfo->mask = 0xffffffff;
178		}
179		if (invert)
180			realminfo->invert = 1;
181		*flags = 1;
182		break;
183
184	default:
185		return 0;
186	}
187	return 1;
188}
189
190static void
191print_realm(unsigned long id, unsigned long mask, int numeric)
192{
193	const char* name = NULL;
194
195	if (mask != 0xffffffff)
196		printf("0x%lx/0x%lx ", id, mask);
197	else {
198		if (numeric == 0)
199			name = realm_id2name(id);
200		if (name)
201			printf("%s ", name);
202		else
203			printf("0x%lx ", id);
204	}
205}
206
207static void realm_print(const void *ip, const struct xt_entry_match *match,
208                        int numeric)
209{
210	const struct ipt_realm_info *ri = (const void *)match->data;
211
212	if (ri->invert)
213		printf("! ");
214
215	printf("realm ");
216	print_realm(ri->id, ri->mask, numeric);
217}
218
219static void realm_save(const void *ip, const struct xt_entry_match *match)
220{
221	const struct ipt_realm_info *ri = (const void *)match->data;
222
223	if (ri->invert)
224		printf("! ");
225
226	printf("--realm ");
227	print_realm(ri->id, ri->mask, 0);
228}
229
230static void realm_check(unsigned int flags)
231{
232	if (!flags)
233		xtables_error(PARAMETER_PROBLEM,
234			   "realm match: You must specify `--realm'");
235}
236
237static struct xtables_match realm_mt_reg = {
238	.name		= "realm",
239	.version	= XTABLES_VERSION,
240	.family		= NFPROTO_IPV4,
241	.size		= XT_ALIGN(sizeof(struct ipt_realm_info)),
242	.userspacesize	= XT_ALIGN(sizeof(struct ipt_realm_info)),
243	.help		= realm_help,
244	.parse		= realm_parse,
245	.final_check	= realm_check,
246	.print		= realm_print,
247	.save		= realm_save,
248	.extra_opts	= realm_opts,
249};
250
251void _init(void)
252{
253	xtables_register_match(&realm_mt_reg);
254}
255