net/netfilter/xt_owner.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Kernel module to match various things tied to sockets associated with
   4  * locally generated outgoing packets.
   5  *
   6  * (C) 2000 Marc Boucher <marc@mbsi.ca>
   7  *
   8  * Copyright © CC Computer Consultants GmbH, 2007 - 2008
   9  */
  10 #include <linux/module.h>
  11 #include <linux/skbuff.h>
  12 #include <linux/file.h>
  13 #include <linux/cred.h>
  14
  15 #include <net/sock.h>
  16 #include <net/inet_sock.h>
  17 #include <linux/netfilter/x_tables.h>
  18 #include <linux/netfilter/xt_owner.h>
  19
  20 static int owner_check(const struct xt_mtchk_param *par)
  21 {
  22         struct xt_owner_match_info *info = par->matchinfo;
  23         struct net *net = par->net;
  24
  25         /* Only allow the common case where the userns of the writer
  26          * matches the userns of the network namespace.
  27          */
  28         if ((info->match & (XT_OWNER_UID|XT_OWNER_GID)) &&
  29             (current_user_ns() != net->user_ns))
  30                 return -EINVAL;
  31
  32         /* Ensure the uids are valid */
  33         if (info->match & XT_OWNER_UID) {
  34                 kuid_t uid_min = make_kuid(net->user_ns, info->uid_min);
  35                 kuid_t uid_max = make_kuid(net->user_ns, info->uid_max);
  36
  37                 if (!uid_valid(uid_min) || !uid_valid(uid_max) ||
  38                     (info->uid_max < info->uid_min) ||
  39                     uid_lt(uid_max, uid_min)) {
  40                         return -EINVAL;
  41                 }
  42         }
  43
  44         /* Ensure the gids are valid */
  45         if (info->match & XT_OWNER_GID) {
  46                 kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
  47                 kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
  48
  49                 if (!gid_valid(gid_min) || !gid_valid(gid_max) ||
  50                     (info->gid_max < info->gid_min) ||
  51                     gid_lt(gid_max, gid_min)) {
  52                         return -EINVAL;
  53                 }
  54         }
  55
  56         return 0;
  57 }
  58
  59 static bool
  60 owner_mt(const struct sk_buff *skb, struct xt_action_param *par)
  61 {
  62         const struct xt_owner_match_info *info = par->matchinfo;
  63         const struct file *filp;
  64         struct sock *sk = skb_to_full_sk(skb);
  65         struct net *net = xt_net(par);
  66
  67         if (!sk || !sk->sk_socket || !net_eq(net, sock_net(sk)))
  68                 return (info->match ^ info->invert) == 0;
  69         else if (info->match & info->invert & XT_OWNER_SOCKET)
  70                 /*
  71                  * Socket exists but user wanted ! --socket-exists.
  72                  * (Single ampersands intended.)
  73                  */
  74                 return false;
  75
  76         filp = sk->sk_socket->file;
  77         if (filp == NULL)
  78                 return ((info->match ^ info->invert) &
  79                        (XT_OWNER_UID | XT_OWNER_GID)) == 0;
  80
  81         if (info->match & XT_OWNER_UID) {
  82                 kuid_t uid_min = make_kuid(net->user_ns, info->uid_min);
  83                 kuid_t uid_max = make_kuid(net->user_ns, info->uid_max);
  84                 if ((uid_gte(filp->f_cred->fsuid, uid_min) &&
  85                      uid_lte(filp->f_cred->fsuid, uid_max)) ^
  86                     !(info->invert & XT_OWNER_UID))
  87                         return false;
  88         }
  89
  90         if (info->match & XT_OWNER_GID) {
  91                 kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
  92                 kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
  93                 if ((gid_gte(filp->f_cred->fsgid, gid_min) &&
  94                      gid_lte(filp->f_cred->fsgid, gid_max)) ^
  95                     !(info->invert & XT_OWNER_GID))
  96                         return false;
  97         }
  98
  99         return true;
 100 }
 101
 102 static struct xt_match owner_mt_reg __read_mostly = {
 103         .name       = "owner",
 104         .revision   = 1,
 105         .family     = NFPROTO_UNSPEC,
 106         .checkentry = owner_check,
 107         .match      = owner_mt,
 108         .matchsize  = sizeof(struct xt_owner_match_info),
 109         .hooks      = (1 << NF_INET_LOCAL_OUT) |
 110                       (1 << NF_INET_POST_ROUTING),
 111         .me         = THIS_MODULE,
 112 };
 113
 114 static int __init owner_mt_init(void)
 115 {
 116         return xt_register_match(&owner_mt_reg);
 117 }
 118
 119 static void __exit owner_mt_exit(void)
 120 {
 121         xt_unregister_match(&owner_mt_reg);
 122 }
 123
 124 module_init(owner_mt_init);
 125 module_exit(owner_mt_exit);
 126 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
 127 MODULE_DESCRIPTION("Xtables: socket owner matching");
 128 MODULE_LICENSE("GPL");
 129 MODULE_ALIAS("ipt_owner");
 130 MODULE_ALIAS("ip6t_owner");