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