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 <linux/cred.h>
  17
  18 #include <net/sock.h>
  19 #include <net/inet_sock.h>
  20 #include <linux/netfilter/x_tables.h>
  21 #include <linux/netfilter/xt_owner.h>
  22
  23 static int owner_check(const struct xt_mtchk_param *par)
  24 {
  25         struct xt_owner_match_info *info = par->matchinfo;
  26         struct net *net = par->net;
  27
  28         /* Only allow the common case where the userns of the writer
  29          * matches the userns of the network namespace.
  30          */
  31         if ((info->match & (XT_OWNER_UID|XT_OWNER_GID)) &&
  32             (current_user_ns() != net->user_ns))
  33                 return -EINVAL;
  34
  35         /* Ensure the uids are valid */
  36         if (info->match & XT_OWNER_UID) {
  37                 kuid_t uid_min = make_kuid(net->user_ns, info->uid_min);
  38                 kuid_t uid_max = make_kuid(net->user_ns, info->uid_max);
  39
  40                 if (!uid_valid(uid_min) || !uid_valid(uid_max) ||
  41                     (info->uid_max < info->uid_min) ||
  42                     uid_lt(uid_max, uid_min)) {
  43                         return -EINVAL;
  44                 }
  45         }
  46
  47         /* Ensure the gids are valid */
  48         if (info->match & XT_OWNER_GID) {
  49                 kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
  50                 kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
  51
  52                 if (!gid_valid(gid_min) || !gid_valid(gid_max) ||
  53                     (info->gid_max < info->gid_min) ||
  54                     gid_lt(gid_max, gid_min)) {
  55                         return -EINVAL;
  56                 }
  57         }
  58
  59         return 0;
  60 }
  61
  62 static bool
  63 owner_mt(const struct sk_buff *skb, struct xt_action_param *par)
  64 {
  65         const struct xt_owner_match_info *info = par->matchinfo;
  66         const struct file *filp;
  67         struct sock *sk = skb_to_full_sk(skb);
  68         struct net *net = xt_net(par);
  69
  70         if (sk == NULL || sk->sk_socket == NULL)
  71                 return (info->match ^ info->invert) == 0;
  72         else if (info->match & info->invert & XT_OWNER_SOCKET)
  73                 /*
  74                  * Socket exists but user wanted ! --socket-exists.
  75                  * (Single ampersands intended.)
  76                  */
  77                 return false;
  78
  79         filp = sk->sk_socket->file;
  80         if (filp == NULL)
  81                 return ((info->match ^ info->invert) &
  82                        (XT_OWNER_UID | XT_OWNER_GID)) == 0;
  83
  84         if (info->match & XT_OWNER_UID) {
  85                 kuid_t uid_min = make_kuid(net->user_ns, info->uid_min);
  86                 kuid_t uid_max = make_kuid(net->user_ns, info->uid_max);
  87                 if ((uid_gte(filp->f_cred->fsuid, uid_min) &&
  88                      uid_lte(filp->f_cred->fsuid, uid_max)) ^
  89                     !(info->invert & XT_OWNER_UID))
  90                         return false;
  91         }
  92
  93         if (info->match & XT_OWNER_GID) {
  94                 kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
  95                 kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
  96                 if ((gid_gte(filp->f_cred->fsgid, gid_min) &&
  97                      gid_lte(filp->f_cred->fsgid, gid_max)) ^
  98                     !(info->invert & XT_OWNER_GID))
  99                         return false;
 100         }
 101
 102         return true;
 103 }
 104
 105 static struct xt_match owner_mt_reg __read_mostly = {
 106         .name       = "owner",
 107         .revision   = 1,
 108         .family     = NFPROTO_UNSPEC,
 109         .checkentry = owner_check,
 110         .match      = owner_mt,
 111         .matchsize  = sizeof(struct xt_owner_match_info),
 112         .hooks      = (1 << NF_INET_LOCAL_OUT) |
 113                       (1 << NF_INET_POST_ROUTING),
 114         .me         = THIS_MODULE,
 115 };
 116
 117 static int __init owner_mt_init(void)
 118 {
 119         return xt_register_match(&owner_mt_reg);
 120 }
 121
 122 static void __exit owner_mt_exit(void)
 123 {
 124         xt_unregister_match(&owner_mt_reg);
 125 }
 126
 127 module_init(owner_mt_init);
 128 module_exit(owner_mt_exit);
 129 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
 130 MODULE_DESCRIPTION("Xtables: socket owner matching");
 131 MODULE_LICENSE("GPL");
 132 MODULE_ALIAS("ipt_owner");
 133 MODULE_ALIAS("ip6t_owner");