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
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
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 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
122 static 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
134 static int __init owner_mt_init(void)
135 {
136 return xt_register_match(&owner_mt_reg);
137 }
138
139 static void __exit owner_mt_exit(void)
140 {
141 xt_unregister_match(&owner_mt_reg);
142 }
143
144 module_init(owner_mt_init);
145 module_exit(owner_mt_exit);
146 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
147 MODULE_DESCRIPTION("Xtables: socket owner matching");
148 MODULE_LICENSE("GPL");
149 MODULE_ALIAS("ipt_owner");
150 MODULE_ALIAS("ip6t_owner");
151
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