1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Kernel module to match AH parameters. */
3 /* (C) 1999-2000 Yon Uriarte <yon@astaro.de>
4 */
5 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
6 #include <linux/in.h>
7 #include <linux/module.h>
8 #include <linux/skbuff.h>
9 #include <linux/ip.h>
10
11 #include <linux/netfilter_ipv4/ipt_ah.h>
12 #include <linux/netfilter/x_tables.h>
13
14 MODULE_LICENSE("GPL");
15 MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
16 MODULE_DESCRIPTION("Xtables: IPv4 IPsec-AH SPI match");
17
18 /* Returns 1 if the spi is matched by the range, 0 otherwise */
19 static inline bool
spi_match(u_int32_t min,u_int32_t max,u_int32_t spi,bool invert)20 spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
21 {
22 bool r;
23 pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
24 invert ? '!' : ' ', min, spi, max);
25 r = (spi >= min && spi <= max) ^ invert;
26 pr_debug(" result %s\n", r ? "PASS" : "FAILED");
27 return r;
28 }
29
ah_mt(const struct sk_buff * skb,struct xt_action_param * par)30 static bool ah_mt(const struct sk_buff *skb, struct xt_action_param *par)
31 {
32 struct ip_auth_hdr _ahdr;
33 const struct ip_auth_hdr *ah;
34 const struct ipt_ah *ahinfo = par->matchinfo;
35
36 /* Must not be a fragment. */
37 if (par->fragoff != 0)
38 return false;
39
40 ah = skb_header_pointer(skb, par->thoff, sizeof(_ahdr), &_ahdr);
41 if (ah == NULL) {
42 /* We've been asked to examine this packet, and we
43 * can't. Hence, no choice but to drop.
44 */
45 pr_debug("Dropping evil AH tinygram.\n");
46 par->hotdrop = true;
47 return false;
48 }
49
50 return spi_match(ahinfo->spis[0], ahinfo->spis[1],
51 ntohl(ah->spi),
52 !!(ahinfo->invflags & IPT_AH_INV_SPI));
53 }
54
ah_mt_check(const struct xt_mtchk_param * par)55 static int ah_mt_check(const struct xt_mtchk_param *par)
56 {
57 const struct ipt_ah *ahinfo = par->matchinfo;
58
59 /* Must specify no unknown invflags */
60 if (ahinfo->invflags & ~IPT_AH_INV_MASK) {
61 pr_debug("unknown flags %X\n", ahinfo->invflags);
62 return -EINVAL;
63 }
64 return 0;
65 }
66
67 static struct xt_match ah_mt_reg __read_mostly = {
68 .name = "ah",
69 .family = NFPROTO_IPV4,
70 .match = ah_mt,
71 .matchsize = sizeof(struct ipt_ah),
72 .proto = IPPROTO_AH,
73 .checkentry = ah_mt_check,
74 .me = THIS_MODULE,
75 };
76
ah_mt_init(void)77 static int __init ah_mt_init(void)
78 {
79 return xt_register_match(&ah_mt_reg);
80 }
81
ah_mt_exit(void)82 static void __exit ah_mt_exit(void)
83 {
84 xt_unregister_match(&ah_mt_reg);
85 }
86
87 module_init(ah_mt_init);
88 module_exit(ah_mt_exit);
89
