Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 struct sock *sk = skb_to_full_sk(skb);
67 struct net *net = xt_net(par);
68 const struct socket *sock;
69 const struct file *filp;
70
71 if (!sk || !READ_ONCE(sk->sk_socket) || !net_eq(net, sock_net(sk)))
72 return (info->match ^ info->invert) == 0;
73 else if (info->match & info->invert & XT_OWNER_SOCKET)
74 /*
75 * Socket exists but user wanted ! --socket-exists.
76 * (Single ampersands intended.)
77 */
78 return false;
79
80 /* The sk pointer remains valid as long as the skb is. The sk_socket and
81 * file pointer may become NULL if the socket is closed. Both structures
82 * (including file->cred) are RCU freed which means they can be accessed
83 * within a RCU read section.
84 */
85 sock = READ_ONCE(sk->sk_socket);
86 filp = sock ? READ_ONCE(sock->file) : NULL;
87 if (filp == NULL)
88 return ((info->match ^ info->invert) &
89 (XT_OWNER_UID | XT_OWNER_GID)) == 0;
90
91 if (info->match & XT_OWNER_UID) {
92 kuid_t uid_min = make_kuid(net->user_ns, info->uid_min);
93 kuid_t uid_max = make_kuid(net->user_ns, info->uid_max);
94
95 if ((uid_gte(filp->f_cred->fsuid, uid_min) &&
96 uid_lte(filp->f_cred->fsuid, uid_max)) ^
97 !(info->invert & XT_OWNER_UID))
98 return false;
99 }
100
101 if (info->match & XT_OWNER_GID) {
102 unsigned int i, match = false;
103 kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
104 kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
105 struct group_info *gi = filp->f_cred->group_info;
106
107 if (gid_gte(filp->f_cred->fsgid, gid_min) &&
108 gid_lte(filp->f_cred->fsgid, gid_max))
109 match = true;
110
111 if (!match && (info->match & XT_OWNER_SUPPL_GROUPS) && gi) {
112 for (i = 0; i < gi->ngroups; ++i) {
113 kgid_t group = gi->gid[i];
114
115 if (gid_gte(group, gid_min) &&
116 gid_lte(group, gid_max)) {
117 match = true;
118 break;
119 }
120 }
121 }
122
123 if (match ^ !(info->invert & XT_OWNER_GID))
124 return false;
125 }
126
127 return true;
128}
129
130static struct xt_match owner_mt_reg[] __read_mostly = {
131 {
132 .name = "owner",
133 .revision = 1,
134 .family = NFPROTO_IPV4,
135 .checkentry = owner_check,
136 .match = owner_mt,
137 .matchsize = sizeof(struct xt_owner_match_info),
138 .hooks = (1 << NF_INET_LOCAL_OUT) |
139 (1 << NF_INET_POST_ROUTING),
140 .me = THIS_MODULE,
141 },
142 {
143 .name = "owner",
144 .revision = 1,
145 .family = NFPROTO_IPV6,
146 .checkentry = owner_check,
147 .match = owner_mt,
148 .matchsize = sizeof(struct xt_owner_match_info),
149 .hooks = (1 << NF_INET_LOCAL_OUT) |
150 (1 << NF_INET_POST_ROUTING),
151 .me = THIS_MODULE,
152 }
153};
154
155static int __init owner_mt_init(void)
156{
157 return xt_register_matches(owner_mt_reg, ARRAY_SIZE(owner_mt_reg));
158}
159
160static void __exit owner_mt_exit(void)
161{
162 xt_unregister_matches(owner_mt_reg, ARRAY_SIZE(owner_mt_reg));
163}
164
165module_init(owner_mt_init);
166module_exit(owner_mt_exit);
167MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
168MODULE_DESCRIPTION("Xtables: socket owner matching");
169MODULE_LICENSE("GPL");
170MODULE_ALIAS("ipt_owner");
171MODULE_ALIAS("ip6t_owner");