LXR linux/net/netfilter/xt

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