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	read_lock_bh(&sk->sk_callback_lock);
80	filp = sk->sk_socket ? sk->sk_socket->file : NULL;
81	if (filp == NULL) {
82		read_unlock_bh(&sk->sk_callback_lock);
83		return ((info->match ^ info->invert) &
84		       (XT_OWNER_UID | XT_OWNER_GID)) == 0;
85	}
86
87	if (info->match & XT_OWNER_UID) {
88		kuid_t uid_min = make_kuid(net->user_ns, info->uid_min);
89		kuid_t uid_max = make_kuid(net->user_ns, info->uid_max);
90		if ((uid_gte(filp->f_cred->fsuid, uid_min) &&
91		     uid_lte(filp->f_cred->fsuid, uid_max)) ^
92		    !(info->invert & XT_OWNER_UID)) {
93			read_unlock_bh(&sk->sk_callback_lock);
94			return false;
95		}
96	}
97
98	if (info->match & XT_OWNER_GID) {
99		unsigned int i, match = false;
100		kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
101		kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
102		struct group_info *gi = filp->f_cred->group_info;
103
104		if (gid_gte(filp->f_cred->fsgid, gid_min) &&
105		    gid_lte(filp->f_cred->fsgid, gid_max))
106			match = true;
107
108		if (!match && (info->match & XT_OWNER_SUPPL_GROUPS) && gi) {
109			for (i = 0; i < gi->ngroups; ++i) {
110				kgid_t group = gi->gid[i];
111
112				if (gid_gte(group, gid_min) &&
113				    gid_lte(group, gid_max)) {
114					match = true;
115					break;
116				}
117			}
118		}
119
120		if (match ^ !(info->invert & XT_OWNER_GID)) {
121			read_unlock_bh(&sk->sk_callback_lock);
122			return false;
123		}
124	}
125
126	read_unlock_bh(&sk->sk_callback_lock);
127	return true;
128}
129
130static struct xt_match owner_mt_reg __read_mostly = {
131	.name       = "owner",
132	.revision   = 1,
133	.family     = NFPROTO_UNSPEC,
134	.checkentry = owner_check,
135	.match      = owner_mt,
136	.matchsize  = sizeof(struct xt_owner_match_info),
137	.hooks      = (1 << NF_INET_LOCAL_OUT) |
138	              (1 << NF_INET_POST_ROUTING),
139	.me         = THIS_MODULE,
140};
141
142static int __init owner_mt_init(void)
143{
144	return xt_register_match(&owner_mt_reg);
145}
146
147static void __exit owner_mt_exit(void)
148{
149	xt_unregister_match(&owner_mt_reg);
150}
151
152module_init(owner_mt_init);
153module_exit(owner_mt_exit);
154MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
155MODULE_DESCRIPTION("Xtables: socket owner matching");
156MODULE_LICENSE("GPL");
157MODULE_ALIAS("ipt_owner");
158MODULE_ALIAS("ip6t_owner");
159