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