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// SPDX-License-Identifier: GPL-2.0-only
/*
* Kernel module to match various things tied to sockets associated with
* locally generated outgoing packets.
*
* (C) 2000 Marc Boucher <marc@mbsi.ca>
*
* Copyright © CC Computer Consultants GmbH, 2007 - 2008
*/
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/file.h>
#include <linux/cred.h>
#include <net/sock.h>
#include <net/inet_sock.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_owner.h>
static int owner_check(const struct xt_mtchk_param *par)
{
struct xt_owner_match_info *info = par->matchinfo;
struct net *net = par->net;
if (info->match & ~XT_OWNER_MASK)
return -EINVAL;
/* Only allow the common case where the userns of the writer
* matches the userns of the network namespace.
*/
if ((info->match & (XT_OWNER_UID|XT_OWNER_GID)) &&
(current_user_ns() != net->user_ns))
return -EINVAL;
/* Ensure the uids are valid */
if (info->match & XT_OWNER_UID) {
kuid_t uid_min = make_kuid(net->user_ns, info->uid_min);
kuid_t uid_max = make_kuid(net->user_ns, info->uid_max);
if (!uid_valid(uid_min) || !uid_valid(uid_max) ||
(info->uid_max < info->uid_min) ||
uid_lt(uid_max, uid_min)) {
return -EINVAL;
}
}
/* Ensure the gids are valid */
if (info->match & XT_OWNER_GID) {
kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
if (!gid_valid(gid_min) || !gid_valid(gid_max) ||
(info->gid_max < info->gid_min) ||
gid_lt(gid_max, gid_min)) {
return -EINVAL;
}
}
return 0;
}
static bool
owner_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
const struct xt_owner_match_info *info = par->matchinfo;
const struct file *filp;
struct sock *sk = skb_to_full_sk(skb);
struct net *net = xt_net(par);
if (!sk || !sk->sk_socket || !net_eq(net, sock_net(sk)))
return (info->match ^ info->invert) == 0;
else if (info->match & info->invert & XT_OWNER_SOCKET)
/*
* Socket exists but user wanted ! --socket-exists.
* (Single ampersands intended.)
*/
return false;
read_lock_bh(&sk->sk_callback_lock);
filp = sk->sk_socket ? sk->sk_socket->file : NULL;
if (filp == NULL) {
read_unlock_bh(&sk->sk_callback_lock);
return ((info->match ^ info->invert) &
(XT_OWNER_UID | XT_OWNER_GID)) == 0;
}
if (info->match & XT_OWNER_UID) {
kuid_t uid_min = make_kuid(net->user_ns, info->uid_min);
kuid_t uid_max = make_kuid(net->user_ns, info->uid_max);
if ((uid_gte(filp->f_cred->fsuid, uid_min) &&
uid_lte(filp->f_cred->fsuid, uid_max)) ^
!(info->invert & XT_OWNER_UID)) {
read_unlock_bh(&sk->sk_callback_lock);
return false;
}
}
if (info->match & XT_OWNER_GID) {
unsigned int i, match = false;
kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
struct group_info *gi = filp->f_cred->group_info;
if (gid_gte(filp->f_cred->fsgid, gid_min) &&
gid_lte(filp->f_cred->fsgid, gid_max))
match = true;
if (!match && (info->match & XT_OWNER_SUPPL_GROUPS) && gi) {
for (i = 0; i < gi->ngroups; ++i) {
kgid_t group = gi->gid[i];
if (gid_gte(group, gid_min) &&
gid_lte(group, gid_max)) {
match = true;
break;
}
}
}
if (match ^ !(info->invert & XT_OWNER_GID)) {
read_unlock_bh(&sk->sk_callback_lock);
return false;
}
}
read_unlock_bh(&sk->sk_callback_lock);
return true;
}
static struct xt_match owner_mt_reg __read_mostly = {
.name = "owner",
.revision = 1,
.family = NFPROTO_UNSPEC,
.checkentry = owner_check,
.match = owner_mt,
.matchsize = sizeof(struct xt_owner_match_info),
.hooks = (1 << NF_INET_LOCAL_OUT) |
(1 << NF_INET_POST_ROUTING),
.me = THIS_MODULE,
};
static int __init owner_mt_init(void)
{
return xt_register_match(&owner_mt_reg);
}
static void __exit owner_mt_exit(void)
{
xt_unregister_match(&owner_mt_reg);
}
module_init(owner_mt_init);
module_exit(owner_mt_exit);
MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
MODULE_DESCRIPTION("Xtables: socket owner matching");
MODULE_LICENSE("GPL");
MODULE_ALIAS("ipt_owner");
MODULE_ALIAS("ip6t_owner");
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