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         if (info->match & ~XT_OWNER_MASK)
  26                 return -EINVAL;
  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 || !sk->sk_socket || !net_eq(net, sock_net(sk)))
  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         read_lock_bh(&sk->sk_callback_lock);
  80         filp = sk->sk_socket ? sk->sk_socket->file : NULL;
  81         if (filp == NULL) {
  82                 read_unlock_bh(&sk->sk_callback_lock);
  83                 return ((info->match ^ info->invert) &
  84                        (XT_OWNER_UID | XT_OWNER_GID)) == 0;
  85         }
  86
  87         if (info->match & XT_OWNER_UID) {
  88                 kuid_t uid_min = make_kuid(net->user_ns, info->uid_min);
  89                 kuid_t uid_max = make_kuid(net->user_ns, info->uid_max);
  90                 if ((uid_gte(filp->f_cred->fsuid, uid_min) &&
  91                      uid_lte(filp->f_cred->fsuid, uid_max)) ^
  92                     !(info->invert & XT_OWNER_UID)) {
  93                         read_unlock_bh(&sk->sk_callback_lock);
  94                         return false;
  95                 }
  96         }
  97
  98         if (info->match & XT_OWNER_GID) {
  99                 unsigned int i, match = false;
 100                 kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
 101                 kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
 102                 struct group_info *gi = filp->f_cred->group_info;
 103
 104                 if (gid_gte(filp->f_cred->fsgid, gid_min) &&
 105                     gid_lte(filp->f_cred->fsgid, gid_max))
 106                         match = true;
 107
 108                 if (!match && (info->match & XT_OWNER_SUPPL_GROUPS) && gi) {
 109                         for (i = 0; i < gi->ngroups; ++i) {
 110                                 kgid_t group = gi->gid[i];
 111
 112                                 if (gid_gte(group, gid_min) &&
 113                                     gid_lte(group, gid_max)) {
 114                                         match = true;
 115                                         break;
 116                                 }
 117                         }
 118                 }
 119
 120                 if (match ^ !(info->invert & XT_OWNER_GID)) {
 121                         read_unlock_bh(&sk->sk_callback_lock);
 122                         return false;
 123                 }
 124         }
 125
 126         read_unlock_bh(&sk->sk_callback_lock);
 127         return true;
 128 }
 129
 130 static struct xt_match owner_mt_reg __read_mostly = {
 131         .name       = "owner",
 132         .revision   = 1,
 133         .family     = NFPROTO_UNSPEC,
 134         .checkentry = owner_check,
 135         .match      = owner_mt,
 136         .matchsize  = sizeof(struct xt_owner_match_info),
 137         .hooks      = (1 << NF_INET_LOCAL_OUT) |
 138                       (1 << NF_INET_POST_ROUTING),
 139         .me         = THIS_MODULE,
 140 };
 141
 142 static int __init owner_mt_init(void)
 143 {
 144         return xt_register_match(&owner_mt_reg);
 145 }
 146
 147 static void __exit owner_mt_exit(void)
 148 {
 149         xt_unregister_match(&owner_mt_reg);
 150 }
 151
 152 module_init(owner_mt_init);
 153 module_exit(owner_mt_exit);
 154 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
 155 MODULE_DESCRIPTION("Xtables: socket owner matching");
 156 MODULE_LICENSE("GPL");
 157 MODULE_ALIAS("ipt_owner");
 158 MODULE_ALIAS("ip6t_owner");