LXR linux/net/netfilter/xt

   1/*
   2 * Kernel module to match various things tied to sockets associated with
   3 * locally generated outgoing packets.
   4 *
   5 * (C) 2000 Marc Boucher <marc@mbsi.ca>
   6 *
   7 * Copyright © CC Computer Consultants GmbH, 2007 - 2008
   8 *
   9 * This program is free software; you can redistribute it and/or modify
  10 * it under the terms of the GNU General Public License version 2 as
  11 * published by the Free Software Foundation.
  12 */
  13#include <linux/module.h>
  14#include <linux/skbuff.h>
  15#include <linux/file.h>
  16#include <net/sock.h>
  17#include <net/inet_sock.h>
  18#include <linux/netfilter/x_tables.h>
  19#include <linux/netfilter/xt_owner.h>
  20
  21static int owner_check(const struct xt_mtchk_param *par)
  22{
  23        struct xt_owner_match_info *info = par->matchinfo;
  24
  25        /* For now only allow adding matches from the initial user namespace */
  26        if ((info->match & (XT_OWNER_UID|XT_OWNER_GID)) &&
  27            (current_user_ns() != &init_user_ns))
  28                return -EINVAL;
  29        return 0;
  30}
  31
  32static bool
  33owner_mt(const struct sk_buff *skb, struct xt_action_param *par)
  34{
  35        const struct xt_owner_match_info *info = par->matchinfo;
  36        const struct file *filp;
  37        struct sock *sk = skb_to_full_sk(skb);
  38
  39        if (sk == NULL || sk->sk_socket == NULL)
  40                return (info->match ^ info->invert) == 0;
  41        else if (info->match & info->invert & XT_OWNER_SOCKET)
  42                /*
  43                 * Socket exists but user wanted ! --socket-exists.
  44                 * (Single ampersands intended.)
  45                 */
  46                return false;
  47
  48        filp = sk->sk_socket->file;
  49        if (filp == NULL)
  50                return ((info->match ^ info->invert) &
  51                       (XT_OWNER_UID | XT_OWNER_GID)) == 0;
  52
  53        if (info->match & XT_OWNER_UID) {
  54                kuid_t uid_min = make_kuid(&init_user_ns, info->uid_min);
  55                kuid_t uid_max = make_kuid(&init_user_ns, info->uid_max);
  56                if ((uid_gte(filp->f_cred->fsuid, uid_min) &&
  57                     uid_lte(filp->f_cred->fsuid, uid_max)) ^
  58                    !(info->invert & XT_OWNER_UID))
  59                        return false;
  60        }
  61
  62        if (info->match & XT_OWNER_GID) {
  63                kgid_t gid_min = make_kgid(&init_user_ns, info->gid_min);
  64                kgid_t gid_max = make_kgid(&init_user_ns, info->gid_max);
  65                if ((gid_gte(filp->f_cred->fsgid, gid_min) &&
  66                     gid_lte(filp->f_cred->fsgid, gid_max)) ^
  67                    !(info->invert & XT_OWNER_GID))
  68                        return false;
  69        }
  70
  71        return true;
  72}
  73
  74static struct xt_match owner_mt_reg __read_mostly = {
  75        .name       = "owner",
  76        .revision   = 1,
  77        .family     = NFPROTO_UNSPEC,
  78        .checkentry = owner_check,
  79        .match      = owner_mt,
  80        .matchsize  = sizeof(struct xt_owner_match_info),
  81        .hooks      = (1 << NF_INET_LOCAL_OUT) |
  82                      (1 << NF_INET_POST_ROUTING),
  83        .me         = THIS_MODULE,
  84};
  85
  86static int __init owner_mt_init(void)
  87{
  88        return xt_register_match(&owner_mt_reg);
  89}
  90
  91static void __exit owner_mt_exit(void)
  92{
  93        xt_unregister_match(&owner_mt_reg);
  94}
  95
  96module_init(owner_mt_init);
  97module_exit(owner_mt_exit);
  98MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
  99MODULE_DESCRIPTION("Xtables: socket owner matching");
 100MODULE_LICENSE("GPL");
 101MODULE_ALIAS("ipt_owner");
 102MODULE_ALIAS("ip6t_owner");
 103