xref: /openbmc/linux/net/netfilter/xt_owner.c (revision 1417b719)
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