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
owner_check(const struct xt_mtchk_param * par)20 static 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
62 static bool
owner_mt(const struct sk_buff * skb,struct xt_action_param * par)63 owner_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
130 static 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
owner_mt_init(void)142 static int __init owner_mt_init(void)
143 {
144 return xt_register_match(&owner_mt_reg);
145 }
146
owner_mt_exit(void)147 static void __exit owner_mt_exit(void)
148 {
149 xt_unregister_match(&owner_mt_reg);
150 }
151
152 module_init(owner_mt_init);
153 module_exit(owner_mt_exit);
154 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
155 MODULE_DESCRIPTION("Xtables: socket owner matching");
156 MODULE_LICENSE("GPL");
157 MODULE_ALIAS("ipt_owner");
158 MODULE_ALIAS("ip6t_owner");
159