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Linux/net/netfilter/xt_owner.c

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  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");
132 

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