1  // SPDX-License-Identifier: GPL-2.0-only
2  /* Kernel module to match AH parameters. */
3  
4  /* (C) 2001-2002 Andras Kis-Szabo <kisza@sch.bme.hu>
5   */
6  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
7  #include <linux/module.h>
8  #include <linux/skbuff.h>
9  #include <linux/ip.h>
10  #include <linux/ipv6.h>
11  #include <linux/types.h>
12  #include <net/checksum.h>
13  #include <net/ipv6.h>
14  
15  #include <linux/netfilter/x_tables.h>
16  #include <linux/netfilter_ipv6/ip6_tables.h>
17  #include <linux/netfilter_ipv6/ip6t_ah.h>
18  
19  MODULE_LICENSE("GPL");
20  MODULE_DESCRIPTION("Xtables: IPv6 IPsec-AH match");
21  MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>");
22  
23  /* Returns 1 if the spi is matched by the range, 0 otherwise */
24  static inline bool
spi_match(u_int32_t min,u_int32_t max,u_int32_t spi,bool invert)25  spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
26  {
27  	bool r;
28  
29  	pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
30  		 invert ? '!' : ' ', min, spi, max);
31  	r = (spi >= min && spi <= max) ^ invert;
32  	pr_debug(" result %s\n", r ? "PASS" : "FAILED");
33  	return r;
34  }
35  
ah_mt6(const struct sk_buff * skb,struct xt_action_param * par)36  static bool ah_mt6(const struct sk_buff *skb, struct xt_action_param *par)
37  {
38  	struct ip_auth_hdr _ah;
39  	const struct ip_auth_hdr *ah;
40  	const struct ip6t_ah *ahinfo = par->matchinfo;
41  	unsigned int ptr = 0;
42  	unsigned int hdrlen = 0;
43  	int err;
44  
45  	err = ipv6_find_hdr(skb, &ptr, NEXTHDR_AUTH, NULL, NULL);
46  	if (err < 0) {
47  		if (err != -ENOENT)
48  			par->hotdrop = true;
49  		return false;
50  	}
51  
52  	ah = skb_header_pointer(skb, ptr, sizeof(_ah), &_ah);
53  	if (ah == NULL) {
54  		par->hotdrop = true;
55  		return false;
56  	}
57  
58  	hdrlen = ipv6_authlen(ah);
59  
60  	pr_debug("IPv6 AH LEN %u %u ", hdrlen, ah->hdrlen);
61  	pr_debug("RES %04X ", ah->reserved);
62  	pr_debug("SPI %u %08X\n", ntohl(ah->spi), ntohl(ah->spi));
63  
64  	pr_debug("IPv6 AH spi %02X ",
65  		 spi_match(ahinfo->spis[0], ahinfo->spis[1],
66  			   ntohl(ah->spi),
67  			   !!(ahinfo->invflags & IP6T_AH_INV_SPI)));
68  	pr_debug("len %02X %04X %02X ",
69  		 ahinfo->hdrlen, hdrlen,
70  		 (!ahinfo->hdrlen ||
71  		  (ahinfo->hdrlen == hdrlen) ^
72  		  !!(ahinfo->invflags & IP6T_AH_INV_LEN)));
73  	pr_debug("res %02X %04X %02X\n",
74  		 ahinfo->hdrres, ah->reserved,
75  		 !(ahinfo->hdrres && ah->reserved));
76  
77  	return spi_match(ahinfo->spis[0], ahinfo->spis[1],
78  			  ntohl(ah->spi),
79  			  !!(ahinfo->invflags & IP6T_AH_INV_SPI)) &&
80  		(!ahinfo->hdrlen ||
81  		 (ahinfo->hdrlen == hdrlen) ^
82  		 !!(ahinfo->invflags & IP6T_AH_INV_LEN)) &&
83  		!(ahinfo->hdrres && ah->reserved);
84  }
85  
ah_mt6_check(const struct xt_mtchk_param * par)86  static int ah_mt6_check(const struct xt_mtchk_param *par)
87  {
88  	const struct ip6t_ah *ahinfo = par->matchinfo;
89  
90  	if (ahinfo->invflags & ~IP6T_AH_INV_MASK) {
91  		pr_debug("unknown flags %X\n", ahinfo->invflags);
92  		return -EINVAL;
93  	}
94  	return 0;
95  }
96  
97  static struct xt_match ah_mt6_reg __read_mostly = {
98  	.name		= "ah",
99  	.family		= NFPROTO_IPV6,
100  	.match		= ah_mt6,
101  	.matchsize	= sizeof(struct ip6t_ah),
102  	.checkentry	= ah_mt6_check,
103  	.me		= THIS_MODULE,
104  };
105  
ah_mt6_init(void)106  static int __init ah_mt6_init(void)
107  {
108  	return xt_register_match(&ah_mt6_reg);
109  }
110  
ah_mt6_exit(void)111  static void __exit ah_mt6_exit(void)
112  {
113  	xt_unregister_match(&ah_mt6_reg);
114  }
115  
116  module_init(ah_mt6_init);
117  module_exit(ah_mt6_exit);
118