1/*
2 * Kernel module to match various things tied to sockets associated with
3 * locally generated outgoing packets.
4 *
5 * (C) 2000 Marc Boucher <marc@mbsi.ca>
6 *
7 * Copyright �� CC Computer Consultants GmbH, 2007 - 2008
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
12 */
13#include <linux/module.h>
14#include <linux/skbuff.h>
15#include <linux/file.h>
16#include <net/sock.h>
17#include <net/inet_sock.h>
18#include <linux/netfilter/x_tables.h>
19#include <linux/netfilter/xt_owner.h>
20
21static int owner_check(const struct xt_mtchk_param *par)
22{
23	struct xt_owner_match_info *info = par->matchinfo;
24
25	/* For now only allow adding matches from the initial user namespace */
26	if ((info->match & (XT_OWNER_UID|XT_OWNER_GID)) &&
27	    (current_user_ns() != &init_user_ns))
28		return -EINVAL;
29	return 0;
30}
31
32static bool
33owner_mt(const struct sk_buff *skb, struct xt_action_param *par)
34{
35	const struct xt_owner_match_info *info = par->matchinfo;
36	const struct file *filp;
37	struct sock *sk = skb_to_full_sk(skb);
38
39	if (sk == NULL || sk->sk_socket == NULL)
40		return (info->match ^ info->invert) == 0;
41	else if (info->match & info->invert & XT_OWNER_SOCKET)
42		/*
43		 * Socket exists but user wanted ! --socket-exists.
44		 * (Single ampersands intended.)
45		 */
46		return false;
47
48	filp = sk->sk_socket->file;
49	if (filp == NULL)
50		return ((info->match ^ info->invert) &
51		       (XT_OWNER_UID | XT_OWNER_GID)) == 0;
52
53	if (info->match & XT_OWNER_UID) {
54		kuid_t uid_min = make_kuid(&init_user_ns, info->uid_min);
55		kuid_t uid_max = make_kuid(&init_user_ns, info->uid_max);
56		if ((uid_gte(filp->f_cred->fsuid, uid_min) &&
57		     uid_lte(filp->f_cred->fsuid, uid_max)) ^
58		    !(info->invert & XT_OWNER_UID))
59			return false;
60	}
61
62	if (info->match & XT_OWNER_GID) {
63		kgid_t gid_min = make_kgid(&init_user_ns, info->gid_min);
64		kgid_t gid_max = make_kgid(&init_user_ns, info->gid_max);
65		if ((gid_gte(filp->f_cred->fsgid, gid_min) &&
66		     gid_lte(filp->f_cred->fsgid, gid_max)) ^
67		    !(info->invert & XT_OWNER_GID))
68			return false;
69	}
70
71	return true;
72}
73
74static struct xt_match owner_mt_reg __read_mostly = {
75	.name       = "owner",
76	.revision   = 1,
77	.family     = NFPROTO_UNSPEC,
78	.checkentry = owner_check,
79	.match      = owner_mt,
80	.matchsize  = sizeof(struct xt_owner_match_info),
81	.hooks      = (1 << NF_INET_LOCAL_OUT) |
82	              (1 << NF_INET_POST_ROUTING),
83	.me         = THIS_MODULE,
84};
85
86static int __init owner_mt_init(void)
87{
88	return xt_register_match(&owner_mt_reg);
89}
90
91static void __exit owner_mt_exit(void)
92{
93	xt_unregister_match(&owner_mt_reg);
94}
95
96module_init(owner_mt_init);
97module_exit(owner_mt_exit);
98MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
99MODULE_DESCRIPTION("Xtables: socket owner matching");
100MODULE_LICENSE("GPL");
101MODULE_ALIAS("ipt_owner");
102MODULE_ALIAS("ip6t_owner");
103