// SPDX-License-Identifier: GPL-2.0-only
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/* IP tables module for matching IPsec policy
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*
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* Copyright (c) 2004,2005 Patrick McHardy, <kaber@trash.net>
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/init.h>
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#include <net/xfrm.h>
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#include <linux/netfilter.h>
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#include <linux/netfilter/xt_policy.h>
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#include <linux/netfilter/x_tables.h>
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MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
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MODULE_DESCRIPTION("Xtables: IPsec policy match");
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MODULE_LICENSE("GPL");
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static inline bool
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xt_addr_cmp(const union nf_inet_addr *a1, const union nf_inet_addr *m,
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const union nf_inet_addr *a2, unsigned short family)
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{
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switch (family) {
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case NFPROTO_IPV4:
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return ((a1->ip ^ a2->ip) & m->ip) == 0;
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case NFPROTO_IPV6:
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return ipv6_masked_addr_cmp(&a1->in6, &m->in6, &a2->in6) == 0;
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}
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return false;
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}
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static bool
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match_xfrm_state(const struct xfrm_state *x, const struct xt_policy_elem *e,
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unsigned short family)
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{
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#define MATCH_ADDR(x,y,z) (!e->match.x || \
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(xt_addr_cmp(&e->x, &e->y, (const union nf_inet_addr *)(z), family) \
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^ e->invert.x))
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#define MATCH(x,y) (!e->match.x || ((e->x == (y)) ^ e->invert.x))
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return MATCH_ADDR(saddr, smask, &x->props.saddr) &&
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MATCH_ADDR(daddr, dmask, &x->id.daddr) &&
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MATCH(proto, x->id.proto) &&
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MATCH(mode, x->props.mode) &&
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MATCH(spi, x->id.spi) &&
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MATCH(reqid, x->props.reqid);
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}
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static int
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match_policy_in(const struct sk_buff *skb, const struct xt_policy_info *info,
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unsigned short family)
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{
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const struct xt_policy_elem *e;
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const struct sec_path *sp = skb_sec_path(skb);
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int strict = info->flags & XT_POLICY_MATCH_STRICT;
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int i, pos;
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if (sp == NULL)
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return -1;
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if (strict && info->len != sp->len)
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return 0;
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for (i = sp->len - 1; i >= 0; i--) {
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pos = strict ? i - sp->len + 1 : 0;
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if (pos >= info->len)
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return 0;
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e = &info->pol[pos];
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if (match_xfrm_state(sp->xvec[i], e, family)) {
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if (!strict)
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return 1;
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} else if (strict)
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return 0;
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}
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return strict ? 1 : 0;
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}
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static int
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match_policy_out(const struct sk_buff *skb, const struct xt_policy_info *info,
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unsigned short family)
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{
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const struct xt_policy_elem *e;
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const struct dst_entry *dst = skb_dst(skb);
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int strict = info->flags & XT_POLICY_MATCH_STRICT;
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int i, pos;
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if (dst->xfrm == NULL)
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return -1;
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for (i = 0; dst && dst->xfrm;
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dst = ((struct xfrm_dst *)dst)->child, i++) {
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pos = strict ? i : 0;
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if (pos >= info->len)
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return 0;
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e = &info->pol[pos];
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if (match_xfrm_state(dst->xfrm, e, family)) {
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if (!strict)
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return 1;
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} else if (strict)
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return 0;
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}
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return strict ? i == info->len : 0;
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}
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static bool
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policy_mt(const struct sk_buff *skb, struct xt_action_param *par)
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{
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const struct xt_policy_info *info = par->matchinfo;
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int ret;
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if (info->flags & XT_POLICY_MATCH_IN)
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ret = match_policy_in(skb, info, xt_family(par));
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else
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ret = match_policy_out(skb, info, xt_family(par));
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if (ret < 0)
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ret = info->flags & XT_POLICY_MATCH_NONE ? true : false;
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else if (info->flags & XT_POLICY_MATCH_NONE)
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ret = false;
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return ret;
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}
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static int policy_mt_check(const struct xt_mtchk_param *par)
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{
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const struct xt_policy_info *info = par->matchinfo;
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const char *errmsg = "neither incoming nor outgoing policy selected";
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if (!(info->flags & (XT_POLICY_MATCH_IN|XT_POLICY_MATCH_OUT)))
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goto err;
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if (par->hook_mask & ((1 << NF_INET_PRE_ROUTING) |
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(1 << NF_INET_LOCAL_IN)) && info->flags & XT_POLICY_MATCH_OUT) {
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errmsg = "output policy not valid in PREROUTING and INPUT";
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goto err;
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}
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if (par->hook_mask & ((1 << NF_INET_POST_ROUTING) |
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(1 << NF_INET_LOCAL_OUT)) && info->flags & XT_POLICY_MATCH_IN) {
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errmsg = "input policy not valid in POSTROUTING and OUTPUT";
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goto err;
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}
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if (info->len > XT_POLICY_MAX_ELEM) {
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errmsg = "too many policy elements";
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goto err;
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}
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return 0;
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err:
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pr_info_ratelimited("%s\n", errmsg);
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return -EINVAL;
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}
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static struct xt_match policy_mt_reg[] __read_mostly = {
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{
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.name = "policy",
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.family = NFPROTO_IPV4,
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.checkentry = policy_mt_check,
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.match = policy_mt,
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.matchsize = sizeof(struct xt_policy_info),
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.me = THIS_MODULE,
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},
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{
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.name = "policy",
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.family = NFPROTO_IPV6,
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.checkentry = policy_mt_check,
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.match = policy_mt,
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.matchsize = sizeof(struct xt_policy_info),
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.me = THIS_MODULE,
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},
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};
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static int __init policy_mt_init(void)
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{
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return xt_register_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
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}
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static void __exit policy_mt_exit(void)
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{
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xt_unregister_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));
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}
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module_init(policy_mt_init);
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module_exit(policy_mt_exit);
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MODULE_ALIAS("ipt_policy");
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MODULE_ALIAS("ip6t_policy");
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