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

  /*
   * Kernel module to match various things tied to sockets associated with
   * locally generated outgoing packets.
   *
   * (C) 2000 Marc Boucher <marc@mbsi.ca>
   *

   * Copyright © CC Computer Consultants GmbH, 2007 - 2008

   */
  #include <linux/module.h>
  #include <linux/skbuff.h>
  #include <linux/file.h>

  #include <linux/cred.h>

  #include <net/sock.h>

  #include <net/inet_sock.h>

  #include <linux/netfilter/x_tables.h>
  #include <linux/netfilter/xt_owner.h>

  static int owner_check(const struct xt_mtchk_param *par)
  {
  	struct xt_owner_match_info *info = par->matchinfo;

  	struct net *net = par->net;

  	if (info->match & ~XT_OWNER_MASK)
  		return -EINVAL;

  	/* Only allow the common case where the userns of the writer
  	 * matches the userns of the network namespace.
  	 */

  	if ((info->match & (XT_OWNER_UID|XT_OWNER_GID)) &&

  	    (current_user_ns() != net->user_ns))

  		return -EINVAL;

  
  	/* Ensure the uids are valid */
  	if (info->match & XT_OWNER_UID) {
  		kuid_t uid_min = make_kuid(net->user_ns, info->uid_min);
  		kuid_t uid_max = make_kuid(net->user_ns, info->uid_max);
  
  		if (!uid_valid(uid_min) || !uid_valid(uid_max) ||
  		    (info->uid_max < info->uid_min) ||
  		    uid_lt(uid_max, uid_min)) {
  			return -EINVAL;
  		}
  	}
  
  	/* Ensure the gids are valid */
  	if (info->match & XT_OWNER_GID) {
  		kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
  		kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
  
  		if (!gid_valid(gid_min) || !gid_valid(gid_max) ||
  		    (info->gid_max < info->gid_min) ||
  		    gid_lt(gid_max, gid_min)) {
  			return -EINVAL;
  		}
  	}

  	return 0;
  }

  static bool

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

  {

  	const struct xt_owner_match_info *info = par->matchinfo;

  	const struct file *filp;

  	struct sock *sk = skb_to_full_sk(skb);

  	struct net *net = xt_net(par);

  	if (!sk || !sk->sk_socket || !net_eq(net, sock_net(sk)))

  		return (info->match ^ info->invert) == 0;
  	else if (info->match & info->invert & XT_OWNER_SOCKET)
  		/*
  		 * Socket exists but user wanted ! --socket-exists.
  		 * (Single ampersands intended.)
  		 */
  		return false;

  	filp = sk->sk_socket->file;

  	if (filp == NULL)
  		return ((info->match ^ info->invert) &
  		       (XT_OWNER_UID | XT_OWNER_GID)) == 0;

  	if (info->match & XT_OWNER_UID) {

  		kuid_t uid_min = make_kuid(net->user_ns, info->uid_min);
  		kuid_t uid_max = make_kuid(net->user_ns, info->uid_max);

  		if ((uid_gte(filp->f_cred->fsuid, uid_min) &&
  		     uid_lte(filp->f_cred->fsuid, uid_max)) ^

  		    !(info->invert & XT_OWNER_UID))

  			return false;

  	}

  	if (info->match & XT_OWNER_GID) {

  		unsigned int i, match = false;

  		kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
  		kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);

  		struct group_info *gi = filp->f_cred->group_info;
  
  		if (gid_gte(filp->f_cred->fsgid, gid_min) &&
  		    gid_lte(filp->f_cred->fsgid, gid_max))
  			match = true;
  
  		if (!match && (info->match & XT_OWNER_SUPPL_GROUPS) && gi) {
  			for (i = 0; i < gi->ngroups; ++i) {
  				kgid_t group = gi->gid[i];
  
  				if (gid_gte(group, gid_min) &&
  				    gid_lte(group, gid_max)) {
  					match = true;
  					break;
  				}
  			}
  		}
  
  		if (match ^ !(info->invert & XT_OWNER_GID))

  			return false;

  	}

  
  	return true;
  }

  static struct xt_match owner_mt_reg __read_mostly = {
  	.name       = "owner",
  	.revision   = 1,
  	.family     = NFPROTO_UNSPEC,

  	.checkentry = owner_check,

  	.match      = owner_mt,
  	.matchsize  = sizeof(struct xt_owner_match_info),
  	.hooks      = (1 << NF_INET_LOCAL_OUT) |
  	              (1 << NF_INET_POST_ROUTING),
  	.me         = THIS_MODULE,

  };
  
  static int __init owner_mt_init(void)
  {

  	return xt_register_match(&owner_mt_reg);

  }
  
  static void __exit owner_mt_exit(void)
  {

  	xt_unregister_match(&owner_mt_reg);

  }
  
  module_init(owner_mt_init);
  module_exit(owner_mt_exit);

  MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");

  MODULE_DESCRIPTION("Xtables: socket owner matching");

  MODULE_LICENSE("GPL");
  MODULE_ALIAS("ipt_owner");
  MODULE_ALIAS("ip6t_owner");