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 <linux/netfilter/x_tables.h>
  18 #include <linux/netfilter/xt_owner.h>
  19
  20 static bool
  21 owner_mt(const struct sk_buff *skb, const struct xt_match_param *par)
  22 {
  23         const struct xt_owner_match_info *info = par->matchinfo;
  24         const struct file *filp;
  25
  26         if (skb->sk == NULL || skb->sk->sk_socket == NULL)
  27                 return (info->match ^ info->invert) == 0;
  28         else if (info->match & info->invert & XT_OWNER_SOCKET)
  29                 /*
  30                  * Socket exists but user wanted ! --socket-exists.
  31                  * (Single ampersands intended.)
  32                  */
  33                 return false;
  34
  35         filp = skb->sk->sk_socket->file;
  36         if (filp == NULL)
  37                 return ((info->match ^ info->invert) &
  38                        (XT_OWNER_UID | XT_OWNER_GID)) == 0;
  39
  40         if (info->match & XT_OWNER_UID)
  41                 if ((filp->f_cred->fsuid >= info->uid_min &&
  42                     filp->f_cred->fsuid <= info->uid_max) ^
  43                     !(info->invert & XT_OWNER_UID))
  44                         return false;
  45
  46         if (info->match & XT_OWNER_GID)
  47                 if ((filp->f_cred->fsgid >= info->gid_min &&
  48                     filp->f_cred->fsgid <= info->gid_max) ^
  49                     !(info->invert & XT_OWNER_GID))
  50                         return false;
  51
  52         return true;
  53 }
  54
  55 static struct xt_match owner_mt_reg __read_mostly = {
  56         .name       = "owner",
  57         .revision   = 1,
  58         .family     = NFPROTO_UNSPEC,
  59         .match      = owner_mt,
  60         .matchsize  = sizeof(struct xt_owner_match_info),
  61         .hooks      = (1 << NF_INET_LOCAL_OUT) |
  62                       (1 << NF_INET_POST_ROUTING),
  63         .me         = THIS_MODULE,
  64 };
  65
  66 static int __init owner_mt_init(void)
  67 {
  68         return xt_register_match(&owner_mt_reg);
  69 }
  70
  71 static void __exit owner_mt_exit(void)
  72 {
  73         xt_unregister_match(&owner_mt_reg);
  74 }
  75
  76 module_init(owner_mt_init);
  77 module_exit(owner_mt_exit);
  78 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
  79 MODULE_DESCRIPTION("Xtables: socket owner matching");
  80 MODULE_LICENSE("GPL");
  81 MODULE_ALIAS("ipt_owner");
  82 MODULE_ALIAS("ip6t_owner");