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 <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
  24        /* For now only allow adding matches from the initial user namespace */
  25        if ((info->match & (XT_OWNER_UID|XT_OWNER_GID)) &&
  26            (current_user_ns() != &init_user_ns))
  27                return -EINVAL;
  28        return 0;
  29}
  30
  31static bool
  32owner_mt(const struct sk_buff *skb, struct xt_action_param *par)
  33{
  34        const struct xt_owner_match_info *info = par->matchinfo;
  35        const struct file *filp;
  36
  37        if (skb->sk == NULL || skb->sk->sk_socket == NULL)
  38                return (info->match ^ info->invert) == 0;
  39        else if (info->match & info->invert & XT_OWNER_SOCKET)
  40                /*
  41                 * Socket exists but user wanted ! --socket-exists.
  42                 * (Single ampersands intended.)
  43                 */
  44                return false;
  45
  46        filp = skb->sk->sk_socket->file;
  47        if (filp == NULL)
  48                return ((info->match ^ info->invert) &
  49                       (XT_OWNER_UID | XT_OWNER_GID)) == 0;
  50
  51        if (info->match & XT_OWNER_UID) {
  52                kuid_t uid_min = make_kuid(&init_user_ns, info->uid_min);
  53                kuid_t uid_max = make_kuid(&init_user_ns, info->uid_max);
  54                if ((uid_gte(filp->f_cred->fsuid, uid_min) &&
  55                     uid_lte(filp->f_cred->fsuid, uid_max)) ^
  56                    !(info->invert & XT_OWNER_UID))
  57                        return false;
  58        }
  59
  60        if (info->match & XT_OWNER_GID) {
  61                kgid_t gid_min = make_kgid(&init_user_ns, info->gid_min);
  62                kgid_t gid_max = make_kgid(&init_user_ns, info->gid_max);
  63                if ((gid_gte(filp->f_cred->fsgid, gid_min) &&
  64                     gid_lte(filp->f_cred->fsgid, gid_max)) ^
  65                    !(info->invert & XT_OWNER_GID))
  66                        return false;
  67        }
  68
  69        return true;
  70}
  71
  72static struct xt_match owner_mt_reg __read_mostly = {
  73        .name       = "owner",
  74        .revision   = 1,
  75        .family     = NFPROTO_UNSPEC,
  76        .checkentry = owner_check,
  77        .match      = owner_mt,
  78        .matchsize  = sizeof(struct xt_owner_match_info),
  79        .hooks      = (1 << NF_INET_LOCAL_OUT) |
  80                      (1 << NF_INET_POST_ROUTING),
  81        .me         = THIS_MODULE,
  82};
  83
  84static int __init owner_mt_init(void)
  85{
  86        return xt_register_match(&owner_mt_reg);
  87}
  88
  89static void __exit owner_mt_exit(void)
  90{
  91        xt_unregister_match(&owner_mt_reg);
  92}
  93
  94module_init(owner_mt_init);
  95module_exit(owner_mt_exit);
  96MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
  97MODULE_DESCRIPTION("Xtables: socket owner matching");
  98MODULE_LICENSE("GPL");
  99MODULE_ALIAS("ipt_owner");
 100MODULE_ALIAS("ip6t_owner");
 101