/net/netfilter/xt_owner.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Kernel module to match various things tied to sockets associated with
  4 * locally generated outgoing packets.
  5 *
  6 * (C) 2000 Marc Boucher <marc@mbsi.ca>
  7 *
  8 * Copyright © CC Computer Consultants GmbH, 2007 - 2008
  9 */
 10#include <linux/module.h>
 11#include <linux/skbuff.h>
 12#include <linux/file.h>
 13#include <linux/cred.h>
 14
 15#include <net/sock.h>
 16#include <net/inet_sock.h>
 17#include <linux/netfilter/x_tables.h>
 18#include <linux/netfilter/xt_owner.h>
 19
 20static int owner_check(const struct xt_mtchk_param *par)
 21{
 22	struct xt_owner_match_info *info = par->matchinfo;
 23	struct net *net = par->net;
 24
 25	if (info->match & ~XT_OWNER_MASK)
 26		return -EINVAL;
 27
 28	/* Only allow the common case where the userns of the writer
 29	 * matches the userns of the network namespace.
 30	 */
 31	if ((info->match & (XT_OWNER_UID|XT_OWNER_GID)) &&
 32	    (current_user_ns() != net->user_ns))
 33		return -EINVAL;
 34
 35	/* Ensure the uids are valid */
 36	if (info->match & XT_OWNER_UID) {
 37		kuid_t uid_min = make_kuid(net->user_ns, info->uid_min);
 38		kuid_t uid_max = make_kuid(net->user_ns, info->uid_max);
 39
 40		if (!uid_valid(uid_min) || !uid_valid(uid_max) ||
 41		    (info->uid_max < info->uid_min) ||
 42		    uid_lt(uid_max, uid_min)) {
 43			return -EINVAL;
 44		}
 45	}
 46
 47	/* Ensure the gids are valid */
 48	if (info->match & XT_OWNER_GID) {
 49		kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
 50		kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
 51
 52		if (!gid_valid(gid_min) || !gid_valid(gid_max) ||
 53		    (info->gid_max < info->gid_min) ||
 54		    gid_lt(gid_max, gid_min)) {
 55			return -EINVAL;
 56		}
 57	}
 58
 59	return 0;
 60}
 61
 62static bool
 63owner_mt(const struct sk_buff *skb, struct xt_action_param *par)
 64{
 65	const struct xt_owner_match_info *info = par->matchinfo;
 66	const struct file *filp;
 67	struct sock *sk = skb_to_full_sk(skb);
 68	struct net *net = xt_net(par);
 69
 70	if (!sk || !sk->sk_socket || !net_eq(net, sock_net(sk)))
 71		return (info->match ^ info->invert) == 0;
 72	else if (info->match & info->invert & XT_OWNER_SOCKET)
 73		/*
 74		 * Socket exists but user wanted ! --socket-exists.
 75		 * (Single ampersands intended.)
 76		 */
 77		return false;
 78
 79	filp = sk->sk_socket->file;
 80	if (filp == NULL)
 81		return ((info->match ^ info->invert) &
 82		       (XT_OWNER_UID | XT_OWNER_GID)) == 0;
 83
 84	if (info->match & XT_OWNER_UID) {
 85		kuid_t uid_min = make_kuid(net->user_ns, info->uid_min);
 86		kuid_t uid_max = make_kuid(net->user_ns, info->uid_max);
 87		if ((uid_gte(filp->f_cred->fsuid, uid_min) &&
 88		     uid_lte(filp->f_cred->fsuid, uid_max)) ^
 89		    !(info->invert & XT_OWNER_UID))
 90			return false;
 91	}
 92
 93	if (info->match & XT_OWNER_GID) {
 94		unsigned int i, match = false;
 95		kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
 96		kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
 97		struct group_info *gi = filp->f_cred->group_info;
 98
 99		if (gid_gte(filp->f_cred->fsgid, gid_min) &&
100		    gid_lte(filp->f_cred->fsgid, gid_max))
101			match = true;
102
103		if (!match && (info->match & XT_OWNER_SUPPL_GROUPS) && gi) {
104			for (i = 0; i < gi->ngroups; ++i) {
105				kgid_t group = gi->gid[i];
106
107				if (gid_gte(group, gid_min) &&
108				    gid_lte(group, gid_max)) {
109					match = true;
110					break;
111				}
112			}
113		}
114
115		if (match ^ !(info->invert & XT_OWNER_GID))
116			return false;
117	}
118
119	return true;
120}
121
122static struct xt_match owner_mt_reg __read_mostly = {
123	.name       = "owner",
124	.revision   = 1,
125	.family     = NFPROTO_UNSPEC,
126	.checkentry = owner_check,
127	.match      = owner_mt,
128	.matchsize  = sizeof(struct xt_owner_match_info),
129	.hooks      = (1 << NF_INET_LOCAL_OUT) |
130	              (1 << NF_INET_POST_ROUTING),
131	.me         = THIS_MODULE,
132};
133
134static int __init owner_mt_init(void)
135{
136	return xt_register_match(&owner_mt_reg);
137}
138
139static void __exit owner_mt_exit(void)
140{
141	xt_unregister_match(&owner_mt_reg);
142}
143
144module_init(owner_mt_init);
145module_exit(owner_mt_exit);
146MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
147MODULE_DESCRIPTION("Xtables: socket owner matching");
148MODULE_LICENSE("GPL");
149MODULE_ALIAS("ipt_owner");
150MODULE_ALIAS("ip6t_owner");