// SPDX-License-Identifier: GPL-2.0-only

  /* IP tables module for matching IPsec policy
   *
   * Copyright (c) 2004,2005 Patrick McHardy, <kaber@trash.net>

   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/kernel.h>

  #include <linux/module.h>
  #include <linux/skbuff.h>
  #include <linux/init.h>
  #include <net/xfrm.h>

  #include <linux/netfilter.h>

  #include <linux/netfilter/xt_policy.h>
  #include <linux/netfilter/x_tables.h>
  
  MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");

  MODULE_DESCRIPTION("Xtables: IPsec policy match");

  MODULE_LICENSE("GPL");

  static inline bool

  xt_addr_cmp(const union nf_inet_addr *a1, const union nf_inet_addr *m,
  	    const union nf_inet_addr *a2, unsigned short family)

  {
  	switch (family) {

  	case NFPROTO_IPV4:

  		return ((a1->ip ^ a2->ip) & m->ip) == 0;

  	case NFPROTO_IPV6:

  		return ipv6_masked_addr_cmp(&a1->in6, &m->in6, &a2->in6) == 0;

  	}

  	return false;

  }

  static bool

  match_xfrm_state(const struct xfrm_state *x, const struct xt_policy_elem *e,

  		 unsigned short family)
  {
  #define MATCH_ADDR(x,y,z)	(!e->match.x ||			       \

  				 (xt_addr_cmp(&e->x, &e->y, (const union nf_inet_addr *)(z), family) \

  				  ^ e->invert.x))
  #define MATCH(x,y)		(!e->match.x || ((e->x == (y)) ^ e->invert.x))

  	return MATCH_ADDR(saddr, smask, &x->props.saddr) &&
  	       MATCH_ADDR(daddr, dmask, &x->id.daddr) &&

  	       MATCH(proto, x->id.proto) &&
  	       MATCH(mode, x->props.mode) &&
  	       MATCH(spi, x->id.spi) &&
  	       MATCH(reqid, x->props.reqid);
  }
  
  static int
  match_policy_in(const struct sk_buff *skb, const struct xt_policy_info *info,
  		unsigned short family)
  {
  	const struct xt_policy_elem *e;

  	const struct sec_path *sp = skb_sec_path(skb);

  	int strict = info->flags & XT_POLICY_MATCH_STRICT;
  	int i, pos;
  
  	if (sp == NULL)
  		return -1;
  	if (strict && info->len != sp->len)
  		return 0;
  
  	for (i = sp->len - 1; i >= 0; i--) {
  		pos = strict ? i - sp->len + 1 : 0;
  		if (pos >= info->len)
  			return 0;
  		e = &info->pol[pos];

  		if (match_xfrm_state(sp->xvec[i], e, family)) {

  			if (!strict)
  				return 1;
  		} else if (strict)
  			return 0;
  	}
  
  	return strict ? 1 : 0;
  }
  
  static int
  match_policy_out(const struct sk_buff *skb, const struct xt_policy_info *info,
  		 unsigned short family)
  {
  	const struct xt_policy_elem *e;

  	const struct dst_entry *dst = skb_dst(skb);

  	int strict = info->flags & XT_POLICY_MATCH_STRICT;
  	int i, pos;
  
  	if (dst->xfrm == NULL)
  		return -1;

  	for (i = 0; dst && dst->xfrm;
  	     dst = ((struct xfrm_dst *)dst)->child, i++) {

  		pos = strict ? i : 0;
  		if (pos >= info->len)
  			return 0;
  		e = &info->pol[pos];
  
  		if (match_xfrm_state(dst->xfrm, e, family)) {
  			if (!strict)
  				return 1;
  		} else if (strict)
  			return 0;
  	}
  
  	return strict ? i == info->len : 0;
  }

  static bool

  policy_mt(const struct sk_buff *skb, struct xt_action_param *par)

  {

  	const struct xt_policy_info *info = par->matchinfo;

  	int ret;
  
  	if (info->flags & XT_POLICY_MATCH_IN)

  		ret = match_policy_in(skb, info, xt_family(par));

  	else

  		ret = match_policy_out(skb, info, xt_family(par));

  
  	if (ret < 0)

  		ret = info->flags & XT_POLICY_MATCH_NONE ? true : false;

  	else if (info->flags & XT_POLICY_MATCH_NONE)

  		ret = false;

  
  	return ret;
  }

  static int policy_mt_check(const struct xt_mtchk_param *par)

  {

  	const struct xt_policy_info *info = par->matchinfo;

  	const char *errmsg = "neither incoming nor outgoing policy selected";
  
  	if (!(info->flags & (XT_POLICY_MATCH_IN|XT_POLICY_MATCH_OUT)))
  		goto err;

  	if (par->hook_mask & ((1 << NF_INET_PRE_ROUTING) |
  	    (1 << NF_INET_LOCAL_IN)) && info->flags & XT_POLICY_MATCH_OUT) {

  		errmsg = "output policy not valid in PREROUTING and INPUT";
  		goto err;

  	}

  	if (par->hook_mask & ((1 << NF_INET_POST_ROUTING) |
  	    (1 << NF_INET_LOCAL_OUT)) && info->flags & XT_POLICY_MATCH_IN) {

  		errmsg = "input policy not valid in POSTROUTING and OUTPUT";
  		goto err;

  	}
  	if (info->len > XT_POLICY_MAX_ELEM) {

  		errmsg = "too many policy elements";
  		goto err;

  	}

  	return 0;

  err:
  	pr_info_ratelimited("%s
  ", errmsg);
  	return -EINVAL;

  }

  static struct xt_match policy_mt_reg[] __read_mostly = {

  	{
  		.name		= "policy",

  		.family		= NFPROTO_IPV4,

  		.checkentry 	= policy_mt_check,
  		.match		= policy_mt,

  		.matchsize	= sizeof(struct xt_policy_info),

  		.me		= THIS_MODULE,
  	},
  	{
  		.name		= "policy",

  		.family		= NFPROTO_IPV6,

  		.checkentry	= policy_mt_check,
  		.match		= policy_mt,

  		.matchsize	= sizeof(struct xt_policy_info),

  		.me		= THIS_MODULE,
  	},

  };

  static int __init policy_mt_init(void)

  {

  	return xt_register_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));

  }

  static void __exit policy_mt_exit(void)

  {

  	xt_unregister_matches(policy_mt_reg, ARRAY_SIZE(policy_mt_reg));

  }

  module_init(policy_mt_init);
  module_exit(policy_mt_exit);

  MODULE_ALIAS("ipt_policy");
  MODULE_ALIAS("ip6t_policy");