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 <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
24	/* For now only allow adding matches from the initial user namespace */
25	if ((info->match & (XT_OWNER_UID|XT_OWNER_GID)) &&
26	    (current_user_ns() != &init_user_ns))
27		return -EINVAL;
28	return 0;
29}
30
31static bool
32owner_mt(const struct sk_buff *skb, struct xt_action_param *par)
33{
34	const struct xt_owner_match_info *info = par->matchinfo;
35	const struct file *filp;
36
37	if (skb->sk == NULL || skb->sk->sk_socket == NULL)
38		return (info->match ^ info->invert) == 0;
39	else if (info->match & info->invert & XT_OWNER_SOCKET)
40		/*
41		 * Socket exists but user wanted ! --socket-exists.
42		 * (Single ampersands intended.)
43		 */
44		return false;
45
46	filp = skb->sk->sk_socket->file;
47	if (filp == NULL)
48		return ((info->match ^ info->invert) &
49		       (XT_OWNER_UID | XT_OWNER_GID)) == 0;
50
51	if (info->match & XT_OWNER_UID) {
52		kuid_t uid_min = make_kuid(&init_user_ns, info->uid_min);
53		kuid_t uid_max = make_kuid(&init_user_ns, info->uid_max);
54		if ((uid_gte(filp->f_cred->fsuid, uid_min) &&
55		     uid_lte(filp->f_cred->fsuid, uid_max)) ^
56		    !(info->invert & XT_OWNER_UID))
57			return false;
58	}
59
60	if (info->match & XT_OWNER_GID) {
61		kgid_t gid_min = make_kgid(&init_user_ns, info->gid_min);
62		kgid_t gid_max = make_kgid(&init_user_ns, info->gid_max);
63		if ((gid_gte(filp->f_cred->fsgid, gid_min) &&
64		     gid_lte(filp->f_cred->fsgid, gid_max)) ^
65		    !(info->invert & XT_OWNER_GID))
66			return false;
67	}
68
69	return true;
70}
71
72static struct xt_match owner_mt_reg __read_mostly = {
73	.name       = "owner",
74	.revision   = 1,
75	.family     = NFPROTO_UNSPEC,
76	.checkentry = owner_check,
77	.match      = owner_mt,
78	.matchsize  = sizeof(struct xt_owner_match_info),
79	.hooks      = (1 << NF_INET_LOCAL_OUT) |
80	              (1 << NF_INET_POST_ROUTING),
81	.me         = THIS_MODULE,
82};
83
84static int __init owner_mt_init(void)
85{
86	return xt_register_match(&owner_mt_reg);
87}
88
89static void __exit owner_mt_exit(void)
90{
91	xt_unregister_match(&owner_mt_reg);
92}
93
94module_init(owner_mt_init);
95module_exit(owner_mt_exit);
96MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
97MODULE_DESCRIPTION("Xtables: socket owner matching");
98MODULE_LICENSE("GPL");
99MODULE_ALIAS("ipt_owner");
100MODULE_ALIAS("ip6t_owner");
101