diff options
Diffstat (limited to 'kernel/net/netfilter/xt_osf.c')
-rw-r--r-- | kernel/net/netfilter/xt_osf.c | 428 |
1 files changed, 428 insertions, 0 deletions
diff --git a/kernel/net/netfilter/xt_osf.c b/kernel/net/netfilter/xt_osf.c new file mode 100644 index 000000000..0778855ea --- /dev/null +++ b/kernel/net/netfilter/xt_osf.c @@ -0,0 +1,428 @@ +/* + * Copyright (c) 2003+ Evgeniy Polyakov <zbr@ioremap.net> + * + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + */ +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt +#include <linux/module.h> +#include <linux/kernel.h> + +#include <linux/if.h> +#include <linux/inetdevice.h> +#include <linux/ip.h> +#include <linux/list.h> +#include <linux/rculist.h> +#include <linux/skbuff.h> +#include <linux/slab.h> +#include <linux/tcp.h> + +#include <net/ip.h> +#include <net/tcp.h> + +#include <linux/netfilter/nfnetlink.h> +#include <linux/netfilter/x_tables.h> +#include <net/netfilter/nf_log.h> +#include <linux/netfilter/xt_osf.h> + +struct xt_osf_finger { + struct rcu_head rcu_head; + struct list_head finger_entry; + struct xt_osf_user_finger finger; +}; + +enum osf_fmatch_states { + /* Packet does not match the fingerprint */ + FMATCH_WRONG = 0, + /* Packet matches the fingerprint */ + FMATCH_OK, + /* Options do not match the fingerprint, but header does */ + FMATCH_OPT_WRONG, +}; + +/* + * Indexed by dont-fragment bit. + * It is the only constant value in the fingerprint. + */ +static struct list_head xt_osf_fingers[2]; + +static const struct nla_policy xt_osf_policy[OSF_ATTR_MAX + 1] = { + [OSF_ATTR_FINGER] = { .len = sizeof(struct xt_osf_user_finger) }, +}; + +static int xt_osf_add_callback(struct sock *ctnl, struct sk_buff *skb, + const struct nlmsghdr *nlh, + const struct nlattr * const osf_attrs[]) +{ + struct xt_osf_user_finger *f; + struct xt_osf_finger *kf = NULL, *sf; + int err = 0; + + if (!osf_attrs[OSF_ATTR_FINGER]) + return -EINVAL; + + if (!(nlh->nlmsg_flags & NLM_F_CREATE)) + return -EINVAL; + + f = nla_data(osf_attrs[OSF_ATTR_FINGER]); + + kf = kmalloc(sizeof(struct xt_osf_finger), GFP_KERNEL); + if (!kf) + return -ENOMEM; + + memcpy(&kf->finger, f, sizeof(struct xt_osf_user_finger)); + + list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) { + if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger))) + continue; + + kfree(kf); + kf = NULL; + + if (nlh->nlmsg_flags & NLM_F_EXCL) + err = -EEXIST; + break; + } + + /* + * We are protected by nfnl mutex. + */ + if (kf) + list_add_tail_rcu(&kf->finger_entry, &xt_osf_fingers[!!f->df]); + + return err; +} + +static int xt_osf_remove_callback(struct sock *ctnl, struct sk_buff *skb, + const struct nlmsghdr *nlh, + const struct nlattr * const osf_attrs[]) +{ + struct xt_osf_user_finger *f; + struct xt_osf_finger *sf; + int err = -ENOENT; + + if (!osf_attrs[OSF_ATTR_FINGER]) + return -EINVAL; + + f = nla_data(osf_attrs[OSF_ATTR_FINGER]); + + list_for_each_entry(sf, &xt_osf_fingers[!!f->df], finger_entry) { + if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger))) + continue; + + /* + * We are protected by nfnl mutex. + */ + list_del_rcu(&sf->finger_entry); + kfree_rcu(sf, rcu_head); + + err = 0; + break; + } + + return err; +} + +static const struct nfnl_callback xt_osf_nfnetlink_callbacks[OSF_MSG_MAX] = { + [OSF_MSG_ADD] = { + .call = xt_osf_add_callback, + .attr_count = OSF_ATTR_MAX, + .policy = xt_osf_policy, + }, + [OSF_MSG_REMOVE] = { + .call = xt_osf_remove_callback, + .attr_count = OSF_ATTR_MAX, + .policy = xt_osf_policy, + }, +}; + +static const struct nfnetlink_subsystem xt_osf_nfnetlink = { + .name = "osf", + .subsys_id = NFNL_SUBSYS_OSF, + .cb_count = OSF_MSG_MAX, + .cb = xt_osf_nfnetlink_callbacks, +}; + +static inline int xt_osf_ttl(const struct sk_buff *skb, const struct xt_osf_info *info, + unsigned char f_ttl) +{ + const struct iphdr *ip = ip_hdr(skb); + + if (info->flags & XT_OSF_TTL) { + if (info->ttl == XT_OSF_TTL_TRUE) + return ip->ttl == f_ttl; + if (info->ttl == XT_OSF_TTL_NOCHECK) + return 1; + else if (ip->ttl <= f_ttl) + return 1; + else { + struct in_device *in_dev = __in_dev_get_rcu(skb->dev); + int ret = 0; + + for_ifa(in_dev) { + if (inet_ifa_match(ip->saddr, ifa)) { + ret = (ip->ttl == f_ttl); + break; + } + } + endfor_ifa(in_dev); + + return ret; + } + } + + return ip->ttl == f_ttl; +} + +static bool +xt_osf_match_packet(const struct sk_buff *skb, struct xt_action_param *p) +{ + const struct xt_osf_info *info = p->matchinfo; + const struct iphdr *ip = ip_hdr(skb); + const struct tcphdr *tcp; + struct tcphdr _tcph; + int fmatch = FMATCH_WRONG, fcount = 0; + unsigned int optsize = 0, check_WSS = 0; + u16 window, totlen, mss = 0; + bool df; + const unsigned char *optp = NULL, *_optp = NULL; + unsigned char opts[MAX_IPOPTLEN]; + const struct xt_osf_finger *kf; + const struct xt_osf_user_finger *f; + struct net *net = dev_net(p->in ? p->in : p->out); + + if (!info) + return false; + + tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph); + if (!tcp) + return false; + + if (!tcp->syn) + return false; + + totlen = ntohs(ip->tot_len); + df = ntohs(ip->frag_off) & IP_DF; + window = ntohs(tcp->window); + + if (tcp->doff * 4 > sizeof(struct tcphdr)) { + optsize = tcp->doff * 4 - sizeof(struct tcphdr); + + _optp = optp = skb_header_pointer(skb, ip_hdrlen(skb) + + sizeof(struct tcphdr), optsize, opts); + } + + rcu_read_lock(); + list_for_each_entry_rcu(kf, &xt_osf_fingers[df], finger_entry) { + int foptsize, optnum; + + f = &kf->finger; + + if (!(info->flags & XT_OSF_LOG) && strcmp(info->genre, f->genre)) + continue; + + optp = _optp; + fmatch = FMATCH_WRONG; + + if (totlen != f->ss || !xt_osf_ttl(skb, info, f->ttl)) + continue; + + /* + * Should not happen if userspace parser was written correctly. + */ + if (f->wss.wc >= OSF_WSS_MAX) + continue; + + /* Check options */ + + foptsize = 0; + for (optnum = 0; optnum < f->opt_num; ++optnum) + foptsize += f->opt[optnum].length; + + if (foptsize > MAX_IPOPTLEN || + optsize > MAX_IPOPTLEN || + optsize != foptsize) + continue; + + check_WSS = f->wss.wc; + + for (optnum = 0; optnum < f->opt_num; ++optnum) { + if (f->opt[optnum].kind == (*optp)) { + __u32 len = f->opt[optnum].length; + const __u8 *optend = optp + len; + int loop_cont = 0; + + fmatch = FMATCH_OK; + + switch (*optp) { + case OSFOPT_MSS: + mss = optp[3]; + mss <<= 8; + mss |= optp[2]; + + mss = ntohs((__force __be16)mss); + break; + case OSFOPT_TS: + loop_cont = 1; + break; + } + + optp = optend; + } else + fmatch = FMATCH_OPT_WRONG; + + if (fmatch != FMATCH_OK) + break; + } + + if (fmatch != FMATCH_OPT_WRONG) { + fmatch = FMATCH_WRONG; + + switch (check_WSS) { + case OSF_WSS_PLAIN: + if (f->wss.val == 0 || window == f->wss.val) + fmatch = FMATCH_OK; + break; + case OSF_WSS_MSS: + /* + * Some smart modems decrease mangle MSS to + * SMART_MSS_2, so we check standard, decreased + * and the one provided in the fingerprint MSS + * values. + */ +#define SMART_MSS_1 1460 +#define SMART_MSS_2 1448 + if (window == f->wss.val * mss || + window == f->wss.val * SMART_MSS_1 || + window == f->wss.val * SMART_MSS_2) + fmatch = FMATCH_OK; + break; + case OSF_WSS_MTU: + if (window == f->wss.val * (mss + 40) || + window == f->wss.val * (SMART_MSS_1 + 40) || + window == f->wss.val * (SMART_MSS_2 + 40)) + fmatch = FMATCH_OK; + break; + case OSF_WSS_MODULO: + if ((window % f->wss.val) == 0) + fmatch = FMATCH_OK; + break; + } + } + + if (fmatch != FMATCH_OK) + continue; + + fcount++; + + if (info->flags & XT_OSF_LOG) + nf_log_packet(net, p->family, p->hooknum, skb, + p->in, p->out, NULL, + "%s [%s:%s] : %pI4:%d -> %pI4:%d hops=%d\n", + f->genre, f->version, f->subtype, + &ip->saddr, ntohs(tcp->source), + &ip->daddr, ntohs(tcp->dest), + f->ttl - ip->ttl); + + if ((info->flags & XT_OSF_LOG) && + info->loglevel == XT_OSF_LOGLEVEL_FIRST) + break; + } + rcu_read_unlock(); + + if (!fcount && (info->flags & XT_OSF_LOG)) + nf_log_packet(net, p->family, p->hooknum, skb, p->in, + p->out, NULL, + "Remote OS is not known: %pI4:%u -> %pI4:%u\n", + &ip->saddr, ntohs(tcp->source), + &ip->daddr, ntohs(tcp->dest)); + + if (fcount) + fmatch = FMATCH_OK; + + return fmatch == FMATCH_OK; +} + +static struct xt_match xt_osf_match = { + .name = "osf", + .revision = 0, + .family = NFPROTO_IPV4, + .proto = IPPROTO_TCP, + .hooks = (1 << NF_INET_LOCAL_IN) | + (1 << NF_INET_PRE_ROUTING) | + (1 << NF_INET_FORWARD), + .match = xt_osf_match_packet, + .matchsize = sizeof(struct xt_osf_info), + .me = THIS_MODULE, +}; + +static int __init xt_osf_init(void) +{ + int err = -EINVAL; + int i; + + for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i) + INIT_LIST_HEAD(&xt_osf_fingers[i]); + + err = nfnetlink_subsys_register(&xt_osf_nfnetlink); + if (err < 0) { + pr_err("Failed to register OSF nsfnetlink helper (%d)\n", err); + goto err_out_exit; + } + + err = xt_register_match(&xt_osf_match); + if (err) { + pr_err("Failed to register OS fingerprint " + "matching module (%d)\n", err); + goto err_out_remove; + } + + return 0; + +err_out_remove: + nfnetlink_subsys_unregister(&xt_osf_nfnetlink); +err_out_exit: + return err; +} + +static void __exit xt_osf_fini(void) +{ + struct xt_osf_finger *f; + int i; + + nfnetlink_subsys_unregister(&xt_osf_nfnetlink); + xt_unregister_match(&xt_osf_match); + + rcu_read_lock(); + for (i=0; i<ARRAY_SIZE(xt_osf_fingers); ++i) { + + list_for_each_entry_rcu(f, &xt_osf_fingers[i], finger_entry) { + list_del_rcu(&f->finger_entry); + kfree_rcu(f, rcu_head); + } + } + rcu_read_unlock(); + + rcu_barrier(); +} + +module_init(xt_osf_init); +module_exit(xt_osf_fini); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>"); +MODULE_DESCRIPTION("Passive OS fingerprint matching."); +MODULE_ALIAS("ipt_osf"); +MODULE_ALIAS("ip6t_osf"); +MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_OSF); |