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 |
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 | |
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, offset: par->thoff, len: sizeof(_ahdr), buffer: &_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(min: ahinfo->spis[0], max: ahinfo->spis[1], |
51 | ntohl(ah->spi), |
52 | invert: !!(ahinfo->invflags & IPT_AH_INV_SPI)); |
53 | } |
54 | |
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 | |
77 | static int __init ah_mt_init(void) |
78 | { |
79 | return xt_register_match(target: &ah_mt_reg); |
80 | } |
81 | |
82 | static void __exit ah_mt_exit(void) |
83 | { |
84 | xt_unregister_match(target: &ah_mt_reg); |
85 | } |
86 | |
87 | module_init(ah_mt_init); |
88 | module_exit(ah_mt_exit); |
89 | |