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(from: net->user_ns, uid: info->uid_min); |
38 | kuid_t uid_max = make_kuid(from: net->user_ns, uid: info->uid_max); |
39 | |
40 | if (!uid_valid(uid: uid_min) || !uid_valid(uid: uid_max) || |
41 | (info->uid_max < info->uid_min) || |
42 | uid_lt(left: uid_max, right: 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(from: net->user_ns, gid: info->gid_min); |
50 | kgid_t gid_max = make_kgid(from: net->user_ns, gid: info->gid_max); |
51 | |
52 | if (!gid_valid(gid: gid_min) || !gid_valid(gid: gid_max) || |
53 | (info->gid_max < info->gid_min) || |
54 | gid_lt(left: gid_max, right: 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(net1: net, net2: 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(from: net->user_ns, uid: info->uid_min); |
89 | kuid_t uid_max = make_kuid(from: net->user_ns, uid: info->uid_max); |
90 | if ((uid_gte(left: filp->f_cred->fsuid, right: uid_min) && |
91 | uid_lte(left: filp->f_cred->fsuid, right: 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(from: net->user_ns, gid: info->gid_min); |
101 | kgid_t gid_max = make_kgid(from: net->user_ns, gid: info->gid_max); |
102 | struct group_info *gi = filp->f_cred->group_info; |
103 | |
104 | if (gid_gte(left: filp->f_cred->fsgid, right: gid_min) && |
105 | gid_lte(left: filp->f_cred->fsgid, right: 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(left: group, right: gid_min) && |
113 | gid_lte(left: group, right: 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 | |
142 | static int __init owner_mt_init(void) |
143 | { |
144 | return xt_register_match(target: &owner_mt_reg); |
145 | } |
146 | |
147 | static void __exit owner_mt_exit(void) |
148 | { |
149 | xt_unregister_match(target: &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 | |