1 /* IP tables module for matching IPsec policy 2 * 3 * Copyright (c) 2004,2005 Patrick McHardy, <kaber@trash.net> 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License version 2 as 7 * published by the Free Software Foundation. 8 */ 9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 10 #include <linux/kernel.h> 11 #include <linux/module.h> 12 #include <linux/skbuff.h> 13 #include <linux/init.h> 14 #include <net/xfrm.h> 15 16 #include <linux/netfilter.h> 17 #include <linux/netfilter/xt_policy.h> 18 #include <linux/netfilter/x_tables.h> 19 20 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); 21 MODULE_DESCRIPTION("Xtables: IPsec policy match"); 22 MODULE_LICENSE("GPL"); 23 24 static inline bool 25 xt_addr_cmp(const union nf_inet_addr *a1, const union nf_inet_addr *m, 26 const union nf_inet_addr *a2, unsigned short family) 27 { 28 switch (family) { 29 case NFPROTO_IPV4: 30 return ((a1->ip ^ a2->ip) & m->ip) == 0; 31 case NFPROTO_IPV6: 32 return ipv6_masked_addr_cmp(&a1->in6, &m->in6, &a2->in6) == 0; 33 } 34 return false; 35 } 36 37 static bool 38 match_xfrm_state(const struct xfrm_state *x, const struct xt_policy_elem *e, 39 unsigned short family) 40 { 41 #define MATCH_ADDR(x,y,z) (!e->match.x || \ 42 (xt_addr_cmp(&e->x, &e->y, (const union nf_inet_addr *)(z), family) \ 43 ^ e->invert.x)) 44 #define MATCH(x,y) (!e->match.x || ((e->x == (y)) ^ e->invert.x)) 45 46 return MATCH_ADDR(saddr, smask, &x->props.saddr) && 47 MATCH_ADDR(daddr, dmask, &x->id.daddr) && 48 MATCH(proto, x->id.proto) && 49 MATCH(mode, x->props.mode) && 50 MATCH(spi, x->id.spi) && 51 MATCH(reqid, x->props.reqid); 52 } 53 54 static int 55 match_policy_in(const struct sk_buff *skb, const struct xt_policy_info *info, 56 unsigned short family) 57 { 58 const struct xt_policy_elem *e; 59 const struct sec_path *sp = skb->sp; 60 int strict = info->flags & XT_POLICY_MATCH_STRICT; 61 int i, pos; 62 63 if (sp == NULL) 64 return -1; 65 if (strict && info->len != sp->len) 66 return 0; 67 68 for (i = sp->len - 1; i >= 0; i--) { 69 pos = strict ? i - sp->len + 1 : 0; 70 if (pos >= info->len) 71 return 0; 72 e = &info->pol[pos]; 73 74 if (match_xfrm_state(sp->xvec[i], e, family)) { 75 if (!strict) 76 return 1; 77 } else if (strict) 78 return 0; 79 } 80 81 return strict ? 1 : 0; 82 } 83 84 static int 85 match_policy_out(const struct sk_buff *skb, const struct xt_policy_info *info, 86 unsigned short family) 87 { 88 const struct xt_policy_elem *e; 89 const struct dst_entry *dst = skb_dst(skb); 90 int strict = info->flags & XT_POLICY_MATCH_STRICT; 91 int i, pos; 92 93 if (dst->xfrm == NULL) 94 return -1; 95 96 for (i = 0; dst && dst->xfrm; dst = dst->child, i++) { 97 pos = strict ? i : 0; 98 if (pos >= info->len) 99 return 0; 100 e = &info->pol[pos]; 101 102 if (match_xfrm_state(dst->xfrm, e, family)) { 103 if (!strict) 104 return 1; 105 } else if (strict) 106 return 0; 107 } 108 109 return strict ? i == info->len : 0; 110 } 111 112 static bool 113 policy_mt(const struct sk_buff *skb, struct xt_action_param *par) 114 { 115 const struct xt_policy_info *info = par->matchinfo; 116 int ret; 117 118 if (info->flags & XT_POLICY_MATCH_IN) 119 ret = match_policy_in(skb, info, xt_family(par)); 120 else 121 ret = match_policy_out(skb, info, xt_family(par)); 122 123 if (ret < 0) 124 ret = info->flags & XT_POLICY_MATCH_NONE ? true : false; 125 else if (info->flags & XT_POLICY_MATCH_NONE) 126 ret = false; 127 128 return ret; 129 } 130 131 static int policy_mt_check(const struct xt_mtchk_param *par) 132 { 133 const struct xt_policy_info *info = par->matchinfo; 134 135 if (!(info->flags & (XT_POLICY_MATCH_IN|XT_POLICY_MATCH_OUT))) { 136 pr_info("neither incoming nor outgoing policy selected\n"); 137 return -EINVAL; 138 } 139 if (par->hook_mask & ((1 << NF_INET_PRE_ROUTING) | 140 (1 << NF_INET_LOCAL_IN)) && info->flags & XT_POLICY_MATCH_OUT) { 141 pr_info("output policy not valid in PREROUTING and INPUT\n"); 142 return -EINVAL; 143 } 144 if (par->hook_mask & ((1 << NF_INET_POST_ROUTING) | 145 (1 << NF_INET_LOCAL_OUT)) && info->flags & XT_POLICY_MATCH_IN) { 146 pr_info("input policy not valid in POSTROUTING and OUTPUT\n"); 147 return -EINVAL; 148 } 149 if (info->len > XT_POLICY_MAX_ELEM) { 150 pr_info("too many policy elements\n"); 151 return -EINVAL; 152 } 153 return 0; 154 } 155 156 static struct xt_match policy_mt_reg[] __read_mostly = { 157 { 158 .name = "policy", 159 .family = NFPROTO_IPV4, 160 .checkentry = policy_mt_check, 161 .match = policy_mt, 162 .matchsize = sizeof(struct xt_policy_info), 163 .me = THIS_MODULE, 164 }, 165 { 166 .name = "policy", 167 .family = NFPROTO_IPV6, 168 .checkentry = policy_mt_check, 169 .match = policy_mt, 170 .matchsize = sizeof(struct xt_policy_info), 171 .me = THIS_MODULE, 172 }, 173 }; 174 175 static int __init policy_mt_init(void) 176 { 177 return xt_register_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg)); 178 } 179 180 static void __exit policy_mt_exit(void) 181 { 182 xt_unregister_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg)); 183 } 184 185 module_init(policy_mt_init); 186 module_exit(policy_mt_exit); 187 MODULE_ALIAS("ipt_policy"); 188 MODULE_ALIAS("ip6t_policy"); 189