net/netfilter/xt_owner.c

   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
  21 static 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
  32 static bool
  33 owner_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
  74 static 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
  86 static int __init owner_mt_init(void)
  87 {
  88         return xt_register_match(&owner_mt_reg);
  89 }
  90
  91 static void __exit owner_mt_exit(void)
  92 {
  93         xt_unregister_match(&owner_mt_reg);
  94 }
  95
  96 module_init(owner_mt_init);
  97 module_exit(owner_mt_exit);
  98 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
  99 MODULE_DESCRIPTION("Xtables: socket owner matching");
 100 MODULE_LICENSE("GPL");
 101 MODULE_ALIAS("ipt_owner");
 102 MODULE_ALIAS("ip6t_owner");