1 /* Kernel module to match IPComp parameters for IPv4 and IPv6
2 *
3 * Copyright (C) 2013 WindRiver
4 *
5 * Author:
6 * Fan Du <fan.du@windriver.com>
7 *
8 * Based on:
9 * net/netfilter/xt_esp.c
10 *
11 * This program is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License
13 * as published by the Free Software Foundation; either version
14 * 2 of the License, or (at your option) any later version.
15 */
16
17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18 #include <linux/in.h>
19 #include <linux/module.h>
20 #include <linux/skbuff.h>
21 #include <linux/ip.h>
22
23 #include <linux/netfilter/xt_ipcomp.h>
24 #include <linux/netfilter/x_tables.h>
25
26 MODULE_LICENSE("GPL");
27 MODULE_AUTHOR("Fan Du <fan.du@windriver.com>");
28 MODULE_DESCRIPTION("Xtables: IPv4/6 IPsec-IPComp SPI match");
29 MODULE_ALIAS("ipt_ipcomp");
30 MODULE_ALIAS("ip6t_ipcomp");
31
32 /* Returns 1 if the spi is matched by the range, 0 otherwise */
33 static inline bool
spi_match(u_int32_t min,u_int32_t max,u_int32_t spi,bool invert)34 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
35 {
36 bool r;
37 pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
38 invert ? '!' : ' ', min, spi, max);
39 r = (spi >= min && spi <= max) ^ invert;
40 pr_debug(" result %s\n", r ? "PASS" : "FAILED");
41 return r;
42 }
43
comp_mt(const struct sk_buff * skb,struct xt_action_param * par)44 static bool comp_mt(const struct sk_buff *skb, struct xt_action_param *par)
45 {
46 struct ip_comp_hdr _comphdr;
47 const struct ip_comp_hdr *chdr;
48 const struct xt_ipcomp *compinfo = par->matchinfo;
49
50 /* Must not be a fragment. */
51 if (par->fragoff != 0)
52 return false;
53
54 chdr = skb_header_pointer(skb, par->thoff, sizeof(_comphdr), &_comphdr);
55 if (chdr == NULL) {
56 /* We've been asked to examine this packet, and we
57 * can't. Hence, no choice but to drop.
58 */
59 pr_debug("Dropping evil IPComp tinygram.\n");
60 par->hotdrop = true;
61 return 0;
62 }
63
64 return spi_match(compinfo->spis[0], compinfo->spis[1],
65 ntohs(chdr->cpi),
66 !!(compinfo->invflags & XT_IPCOMP_INV_SPI));
67 }
68
comp_mt_check(const struct xt_mtchk_param * par)69 static int comp_mt_check(const struct xt_mtchk_param *par)
70 {
71 const struct xt_ipcomp *compinfo = par->matchinfo;
72
73 /* Must specify no unknown invflags */
74 if (compinfo->invflags & ~XT_IPCOMP_INV_MASK) {
75 pr_err("unknown flags %X\n", compinfo->invflags);
76 return -EINVAL;
77 }
78 return 0;
79 }
80
81 static struct xt_match comp_mt_reg[] __read_mostly = {
82 {
83 .name = "ipcomp",
84 .family = NFPROTO_IPV4,
85 .match = comp_mt,
86 .matchsize = sizeof(struct xt_ipcomp),
87 .proto = IPPROTO_COMP,
88 .checkentry = comp_mt_check,
89 .me = THIS_MODULE,
90 },
91 {
92 .name = "ipcomp",
93 .family = NFPROTO_IPV6,
94 .match = comp_mt,
95 .matchsize = sizeof(struct xt_ipcomp),
96 .proto = IPPROTO_COMP,
97 .checkentry = comp_mt_check,
98 .me = THIS_MODULE,
99 },
100 };
101
comp_mt_init(void)102 static int __init comp_mt_init(void)
103 {
104 return xt_register_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
105 }
106
comp_mt_exit(void)107 static void __exit comp_mt_exit(void)
108 {
109 xt_unregister_matches(comp_mt_reg, ARRAY_SIZE(comp_mt_reg));
110 }
111
112 module_init(comp_mt_init);
113 module_exit(comp_mt_exit);
114