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 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 unsigned int i, match = false; 95 kgid_t gid_min = make_kgid(net->user_ns, info->gid_min); 96 kgid_t gid_max = make_kgid(net->user_ns, info->gid_max); 97 struct group_info *gi = filp->f_cred->group_info; 98 99 if (gid_gte(filp->f_cred->fsgid, gid_min) && 100 gid_lte(filp->f_cred->fsgid, gid_max)) 101 match = true; 102 103 if (!match && (info->match & XT_OWNER_SUPPL_GROUPS) && gi) { 104 for (i = 0; i < gi->ngroups; ++i) { 105 kgid_t group = gi->gid[i]; 106 107 if (gid_gte(group, gid_min) && 108 gid_lte(group, gid_max)) { 109 match = true; 110 break; 111 } 112 } 113 } 114 115 if (match ^ !(info->invert & XT_OWNER_GID)) 116 return false; 117 } 118 119 return true; 120 } 121 122 static struct xt_match owner_mt_reg __read_mostly = { 123 .name = "owner", 124 .revision = 1, 125 .family = NFPROTO_UNSPEC, 126 .checkentry = owner_check, 127 .match = owner_mt, 128 .matchsize = sizeof(struct xt_owner_match_info), 129 .hooks = (1 << NF_INET_LOCAL_OUT) | 130 (1 << NF_INET_POST_ROUTING), 131 .me = THIS_MODULE, 132 }; 133 134 static int __init owner_mt_init(void) 135 { 136 return xt_register_match(&owner_mt_reg); 137 } 138 139 static void __exit owner_mt_exit(void) 140 { 141 xt_unregister_match(&owner_mt_reg); 142 } 143 144 module_init(owner_mt_init); 145 module_exit(owner_mt_exit); 146 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>"); 147 MODULE_DESCRIPTION("Xtables: socket owner matching"); 148 MODULE_LICENSE("GPL"); 149 MODULE_ALIAS("ipt_owner"); 150 MODULE_ALIAS("ip6t_owner"); 151