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

  /*
   * Creates audit record for dropped/accepted packets
   *
   * (C) 2010-2011 Thomas Graf <tgraf@redhat.com>
   * (C) 2010-2011 Red Hat, Inc.

  */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/audit.h>
  #include <linux/module.h>
  #include <linux/skbuff.h>
  #include <linux/tcp.h>
  #include <linux/udp.h>
  #include <linux/if_arp.h>
  #include <linux/netfilter/x_tables.h>
  #include <linux/netfilter/xt_AUDIT.h>

  #include <linux/netfilter_bridge/ebtables.h>

  #include <net/ipv6.h>
  #include <net/ip.h>
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Thomas Graf <tgraf@redhat.com>");
  MODULE_DESCRIPTION("Xtables: creates audit records for dropped/accepted packets");
  MODULE_ALIAS("ipt_AUDIT");
  MODULE_ALIAS("ip6t_AUDIT");
  MODULE_ALIAS("ebt_AUDIT");
  MODULE_ALIAS("arpt_AUDIT");

  static bool audit_ip4(struct audit_buffer *ab, struct sk_buff *skb)

  {
  	struct iphdr _iph;
  	const struct iphdr *ih;

  	ih = skb_header_pointer(skb, skb_network_offset(skb), sizeof(_iph), &_iph);

  	if (!ih)
  		return false;

  	audit_log_format(ab, " saddr=%pI4 daddr=%pI4 proto=%hhu",
  			 &ih->saddr, &ih->daddr, ih->protocol);

  	return true;

  }

  static bool audit_ip6(struct audit_buffer *ab, struct sk_buff *skb)

  {
  	struct ipv6hdr _ip6h;
  	const struct ipv6hdr *ih;
  	u8 nexthdr;

  	__be16 frag_off;

  
  	ih = skb_header_pointer(skb, skb_network_offset(skb), sizeof(_ip6h), &_ip6h);

  	if (!ih)
  		return false;

  
  	nexthdr = ih->nexthdr;

  	ipv6_skip_exthdr(skb, skb_network_offset(skb) + sizeof(_ip6h), &nexthdr, &frag_off);

  
  	audit_log_format(ab, " saddr=%pI6c daddr=%pI6c proto=%hhu",
  			 &ih->saddr, &ih->daddr, nexthdr);

  	return true;

  }
  
  static unsigned int
  audit_tg(struct sk_buff *skb, const struct xt_action_param *par)
  {

  	struct audit_buffer *ab;

  	int fam = -1;

  	if (audit_enabled == AUDIT_OFF)

  		goto errout;

  	ab = audit_log_start(NULL, GFP_ATOMIC, AUDIT_NETFILTER_PKT);
  	if (ab == NULL)
  		goto errout;

  	audit_log_format(ab, "mark=%#x", skb->mark);

  	switch (xt_family(par)) {

  	case NFPROTO_BRIDGE:
  		switch (eth_hdr(skb)->h_proto) {
  		case htons(ETH_P_IP):
  			fam = audit_ip4(ab, skb) ? NFPROTO_IPV4 : -1;
  			break;
  		case htons(ETH_P_IPV6):
  			fam = audit_ip6(ab, skb) ? NFPROTO_IPV6 : -1;
  			break;
  		}
  		break;

  	case NFPROTO_IPV4:

  		fam = audit_ip4(ab, skb) ? NFPROTO_IPV4 : -1;

  		break;

  	case NFPROTO_IPV6:

  		fam = audit_ip6(ab, skb) ? NFPROTO_IPV6 : -1;

  		break;
  	}

  	if (fam == -1)
  		audit_log_format(ab, " saddr=? daddr=? proto=-1");

  	audit_log_end(ab);
  
  errout:
  	return XT_CONTINUE;
  }

  static unsigned int
  audit_tg_ebt(struct sk_buff *skb, const struct xt_action_param *par)
  {
  	audit_tg(skb, par);
  	return EBT_CONTINUE;
  }

  static int audit_tg_check(const struct xt_tgchk_param *par)
  {
  	const struct xt_audit_info *info = par->targinfo;
  
  	if (info->type > XT_AUDIT_TYPE_MAX) {

  		pr_info_ratelimited("Audit type out of range (valid range: 0..%hhu)
  ",
  				    XT_AUDIT_TYPE_MAX);

  		return -ERANGE;
  	}
  
  	return 0;
  }

  static struct xt_target audit_tg_reg[] __read_mostly = {
  	{
  		.name		= "AUDIT",
  		.family		= NFPROTO_UNSPEC,
  		.target		= audit_tg,
  		.targetsize	= sizeof(struct xt_audit_info),
  		.checkentry	= audit_tg_check,
  		.me		= THIS_MODULE,
  	},
  	{
  		.name		= "AUDIT",
  		.family		= NFPROTO_BRIDGE,
  		.target		= audit_tg_ebt,
  		.targetsize	= sizeof(struct xt_audit_info),
  		.checkentry	= audit_tg_check,
  		.me		= THIS_MODULE,
  	},

  };
  
  static int __init audit_tg_init(void)
  {

  	return xt_register_targets(audit_tg_reg, ARRAY_SIZE(audit_tg_reg));

  }
  
  static void __exit audit_tg_exit(void)
  {

  	xt_unregister_targets(audit_tg_reg, ARRAY_SIZE(audit_tg_reg));

  }
  
  module_init(audit_tg_init);
  module_exit(audit_tg_exit);