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 || !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 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"); 134