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 20static 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 62static bool 63owner_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 130static 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 142static int __init owner_mt_init(void) 143{ 144 return xt_register_match(&owner_mt_reg); 145} 146 147static void __exit owner_mt_exit(void) 148{ 149 xt_unregister_match(&owner_mt_reg); 150} 151 152module_init(owner_mt_init); 153module_exit(owner_mt_exit); 154MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>"); 155MODULE_DESCRIPTION("Xtables: socket owner matching"); 156MODULE_LICENSE("GPL"); 157MODULE_ALIAS("ipt_owner"); 158MODULE_ALIAS("ip6t_owner"); 159