| Message ID | 20090511095343.GA30778@ioremap.net |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | David Miller |
| Headers | show |
Evgeniy Polyakov wrote: > Example usage: > # modrpobe xt_osf > # ./nfnl_osf -f ./pf.os > -d switch removes fingerprints > # iptables -I INPUT -j ACCEPT -p tcp -m osf --genre Linux --log 0 --ttl 2 > > You will find something like this in the syslog: > Windows [2000:SP3:Windows XP Pro SP1, 2000 SP3]: 11.22.33.55:4024 -> 11.22.33.44:139 hops=4 > Linux [2.5:]: 1.2.3.4:44448 -> 11.22.33.44:22 hops=4 Please convert this to use nf_log_packet(). > diff --git a/include/linux/netfilter/nfnetlink.h b/include/linux/netfilter/nfnetlink.h > index c600083..bb9c9ae 100644 > --- a/include/linux/netfilter/nfnetlink.h > +++ b/include/linux/netfilter/nfnetlink.h > @@ -46,7 +46,8 @@ struct nfgenmsg { > #define NFNL_SUBSYS_CTNETLINK_EXP 2 > #define NFNL_SUBSYS_QUEUE 3 > #define NFNL_SUBSYS_ULOG 4 > -#define NFNL_SUBSYS_COUNT 5 > +#define NFNL_SUBSYS_OSF 5 > +#define NFNL_SUBSYS_COUNT 6 > > #ifdef __KERNEL__ > > diff --git a/include/linux/netfilter/xt_osf.h b/include/linux/netfilter/xt_osf.h > new file mode 100644 > index 0000000..11903a9 > --- /dev/null > +++ b/include/linux/netfilter/xt_osf.h > +#ifndef _XT_OSF_H > +#define _XT_OSF_H > + > +#define MAXGENRELEN 32 > +#define MAXDETLEN 64 ^ Unused > + > +#define XT_OSF_GENRE (1<<0) > +#define XT_OSF_TTL (1<<1) > +#define XT_OSF_LOG (1<<2) > +#define XT_OSF_UNUSED (1<<3) ^ Unused? :) > +#define XT_OSF_CONNECTOR (1<<4) > +#define XT_OSF_INVERT (1<<5) > + > +#define XT_OSF_LOGLEVEL_ALL 0 > +#define XT_OSF_LOGLEVEL_FIRST 1 > +#define XT_OSF_LOGLEVEL_ALL_KNOWN 2 What does this do? > +#define XT_OSF_TTL_TRUE 0 /* True ip and fingerprint TTL comparison */ > +#define XT_OSF_TTL_LESS 1 /* Check if ip TTL is less than fingerprint one */ > +#define XT_OSF_TTL_NOCHECK 2 /* Do not compare ip and fingerprint TTL at all */ These seem redundant - having neither of TRUE or LESS seems equivalent to NOCHECK. Perhaps thats the reason why its not used at all :) Looking at the code, "TRUE" would be better named as "EQUAL". > +struct xt_osf_info { > + char genre[MAXGENRELEN]; > + __u32 len; > + __u32 flags; > + __u32 loglevel; > + __u32 ttl; > +}; Unless you're really really sure that this is not going to change, please use netlink attributes. Similar for the other ABI structures. > + > +/* > + * Wildcard MSS (kind of). > + * It is used to implement a state machine for the different wildcard values > + * of the MSS and window sizes. > + */ > +struct xt_osf_wc { > + __u32 wc; > + __u32 val; > +}; > + > +/* > + * This struct represents IANA options > + * http://www.iana.org/assignments/tcp-parameters > + */ > +struct xt_osf_opt { > + __u16 kind, length; > + struct xt_osf_wc wc; > +}; > + > +struct xt_osf_user_finger { > + struct xt_osf_wc wss; > + > + __u8 ttl, df; > + __u16 ss, mss; > + __u16 opt_num; > + > + char genre[MAXGENRELEN]; > + char version[MAXGENRELEN]; > + char subtype[MAXGENRELEN]; > + > + /* MAX_IPOPTLEN is maximum if all options are NOPs or EOLs */ > + struct xt_osf_opt opt[MAX_IPOPTLEN]; This really looks like you should use nested attributes. > +}; > + > +struct xt_osf_nlmsg { > + struct xt_osf_user_finger f; > + struct iphdr ip; > + struct tcphdr tcp; > +}; > + > +/* Defines for IANA option kinds */ > + > +enum iana_options { > + OSFOPT_EOL = 0, /* End of options */ > + OSFOPT_NOP, /* NOP */ > + OSFOPT_MSS, /* Maximum segment size */ > + OSFOPT_WSO, /* Window scale option */ > + OSFOPT_SACKP, /* SACK permitted */ > + OSFOPT_SACK, /* SACK */ > + OSFOPT_ECHO, > + OSFOPT_ECHOREPLY, > + OSFOPT_TS, /* Timestamp option */ > + OSFOPT_POCP, /* Partial Order Connection Permitted */ > + OSFOPT_POSP, /* Partial Order Service Profile */ > + > + /* Others are not used in the current OSF */ > + OSFOPT_EMPTY = 255, > +}; Why do we need to duplicate these? > + > +enum xt_osf_msg_types { > + OSF_MSG_SETUP, > + OSF_MSG_MAX, > +}; > + > +enum xt_osf_attr_type { > + OSF_ATTR_UNSPEC, > + OSF_ATTR_FINGER, > + OSF_ATTR_MAX, > +}; > + > +#endif /* _XT_OSF_H */ > diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig > index 2329c5f..b0273f9 100644 > --- a/net/netfilter/Kconfig > +++ b/net/netfilter/Kconfig > @@ -916,6 +916,19 @@ config NETFILTER_XT_MATCH_U32 > > Details and examples are in the kernel module source. > > +config NETFILTER_XT_MATCH_OSF > + tristate '"osf" Passive OS fingerprint match' > + depends on NETFILTER_ADVANCED && NFNETLINK > --- /dev/null > +++ b/net/netfilter/xt_osf.c > @@ -0,0 +1,469 @@ > +/* > + * 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, write to the Free Software > + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA > + */ > + > +#include <linux/module.h> > +#include <linux/kernel.h> > + > +#include <linux/connector.h> Not needed. The remaining ones look like some (percpu?) could be removed as well. > +#include <linux/if.h> > +#include <linux/inetdevice.h> > +#include <linux/ip.h> > +#include <linux/list.h> > +#include <linux/percpu.h> > +#include <linux/rculist.h> > +#include <linux/smp.h> > +#include <linux/skbuff.h> > +#include <linux/slab.h> > +#include <linux/spinlock.h> > +#include <linux/tcp.h> > +#include <linux/types.h> > + > +#include <net/ip.h> > +#include <net/tcp.h> > + > +#include <linux/netfilter/nfnetlink.h> > +#include <linux/netfilter/x_tables.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, > +}; > + > +struct xt_osf_finger_storage > +{ Please place the opening bracket consistently with the other structure definitions. > + struct list_head finger_list; > + spinlock_t finger_lock; > +}; > + > +/* > + * Indexed by dont-fragment bit. > + * It is the only constant value in the fingerprint. > + */ > +struct xt_osf_finger_storage xt_osf_fingers[2]; static > + > +struct xt_osf_message { > + struct cn_msg cmsg; > + struct xt_osf_nlmsg nlmsg; > +}; Unused. > +static int xt_osf_setup_callback(struct sock *ctnl, struct sk_buff *skb, > + struct nlmsghdr *nlh, struct nlattr *osf_attrs[]) > +{ > + struct xt_osf_user_finger *f; > + struct nfgenmsg *nfmsg = NLMSG_DATA(nlh); > + u16 delete = ntohs(nfmsg->res_id); This looks like abuse, we use message types to distinguish between additions and deletions, alternative NLM_F_REPLACE. > + struct xt_osf_finger *kf = NULL, *sf; > + struct xt_osf_finger_storage *st; > + int err; > + > + if (!osf_attrs[OSF_ATTR_FINGER]) > + return -EINVAL; > + > + f = nla_data(osf_attrs[OSF_ATTR_FINGER]); > + st = &xt_osf_fingers[!!f->df]; > + > + /* > + * If 'delete' is set to 0 then we add attached fingerprint, > + * otherwise remove, and in this case we do not need to allocate data. > + */ > + if (!delete) { > + kf = kmalloc(sizeof(struct xt_osf_finger), GFP_KERNEL); > + if (!kf) > + return -ENOMEM; > + > + memcpy(&kf->finger, f, sizeof(struct xt_osf_user_finger)); > + } > + > + err = -ENOENT; > + > + rcu_read_lock(); > + list_for_each_entry_rcu(sf, &st->finger_list, finger_entry) { > + if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger))) > + continue; > + > + if (delete) { > + spin_lock_bh(&st->finger_lock); This lock looks useless, all changes are done in netlink context under the nfnl mutex. > + list_del_rcu(&sf->finger_entry); > + spin_unlock_bh(&st->finger_lock); > + call_rcu(&sf->rcu_head, xt_osf_finger_free_rcu); > + } else { > + kfree(kf); > + kf = NULL; > + } > + > + err = 0; > + break; > + } > + > + if (kf) { > + spin_lock_bh(&st->finger_lock); > + list_add_tail_rcu(&kf->finger_entry, &st->finger_list); > + spin_unlock_bh(&st->finger_lock); > +#if 0 > + printk(KERN_INFO "Added rule for %s:%s:%s.\n", > + kf->finger.genre, kf->finger.version, kf->finger.subtype); > +#endif > + } > + rcu_read_unlock(); > + > + return 0; > +} > + > +static const struct nfnl_callback xt_osf_nfnetlink_callbacks[OSF_MSG_MAX] = { > + [OSF_MSG_SETUP] = { > + .call = xt_osf_setup_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(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); > + > + in_dev_put(in_dev); > + return ret; > + } > + } > + > + return ip->ttl == f_ttl; > +} > + > +static bool xt_osf_match_packet(const struct sk_buff *skb, > + const struct xt_match_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; > + const struct xt_osf_finger_storage *st; > + > + 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); > + > + if (optsize > sizeof(opts)) > + optsize = sizeof(opts); > + > + _optp = optp = skb_header_pointer(skb, ip_hdrlen(skb) + sizeof(struct tcphdr), Please break the line at 80 characters > + optsize, opts); > + } > + > + st = &xt_osf_fingers[df]; > + > + rcu_read_lock(); > + list_for_each_entry_rcu(kf, &st->finger_list, finger_entry) { > + 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)) { > + int foptsize, optnum; > + > + check_WSS = 0; > + > + switch (f->wss.wc) { > + case 0: > + check_WSS = 0; > + break; > + case 'S': > + check_WSS = 1; > + break; > + case 'T': > + check_WSS = 2; > + break; > + case '%': > + check_WSS = 3; > + break; > + default: > + check_WSS = 4; > + break; > + } This is really pushing my taste-buds. Whatever this does, please at use symbolic constants so the reader at least has a chance to understand it. > + if (check_WSS == 4) > + 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; > + > + 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(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 0: > + if (f->wss.val == 0 || window == f->wss.val) > + fmatch = FMATCH_OK; > + break; > + case 1: /* MSS */ > +#define SMART_MSS_1 1460 > +#define SMART_MSS_2 1448 Sigh. This entire function is completely unreadable and full of unexplained magic. I'll stop here, please clean this before resubmitting. > + 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 2: /* 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 3: /* MOD */ > + if ((window % f->wss.val) == 0) > + fmatch = FMATCH_OK; > + break; > + } > + } > + > + if (fmatch != FMATCH_OK) > + continue; > + > + fcount++; > + if (info->flags & XT_OSF_LOG) > + printk(KERN_INFO "%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 | XT_OSF_CONNECTOR))) { > + unsigned int i; > + struct xt_osf_user_finger fg; > + > + memset(&fg, 0, sizeof(fg)); > +#if 1 > + if (info->flags & XT_OSF_LOG) { > + if (info->loglevel != XT_OSF_LOGLEVEL_ALL_KNOWN) > + printk(KERN_INFO "Unknown: win: %u, mss: %u, " > + "totlen: %u, df: %d, ttl: %u : ", > + window, mss, totlen, df, ip->ttl); > + else > + printk(KERN_INFO ""); > + if (_optp) { > + optp = _optp; > + for (i = 0; i < optsize; i++) > + printk("%02X ", optp[i]); > + } > + > + printk("%pi4:%u -> %pi4:%u\n", > + &ip->saddr, ntohs(tcp->source), > + &ip->daddr, ntohs(tcp->dest)); > + } > +#endif > + } > + > + if (fcount) > + fmatch = FMATCH_OK; > + > + return fmatch == FMATCH_OK; > +} > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Patrick. Thanks for your comments. On Wed, May 27, 2009 at 06:28:16PM +0200, Patrick McHardy (kaber@trash.net) wrote: > >You will find something like this in the syslog: > >Windows [2000:SP3:Windows XP Pro SP1, 2000 SP3]: 11.22.33.55:4024 -> > >11.22.33.44:139 hops=4 > >Linux [2.5:]: 1.2.3.4:44448 -> 11.22.33.44:22 hops=4 > > Please convert this to use nf_log_packet(). Ok, will use. > >--- /dev/null > >+++ b/include/linux/netfilter/xt_osf.h > >+#ifndef _XT_OSF_H > >+#define _XT_OSF_H > >+ > >+#define MAXGENRELEN 32 > >+#define MAXDETLEN 64 > > ^ Unused > > >+ > >+#define XT_OSF_GENRE (1<<0) > >+#define XT_OSF_TTL (1<<1) > >+#define XT_OSF_LOG (1<<2) > >+#define XT_OSF_UNUSED (1<<3) > > ^ Unused? :) I will drop those constants. > >+#define XT_OSF_CONNECTOR (1<<4) > >+#define XT_OSF_INVERT (1<<5) > >+ > >+#define XT_OSF_LOGLEVEL_ALL 0 > >+#define XT_OSF_LOGLEVEL_FIRST 1 > >+#define XT_OSF_LOGLEVEL_ALL_KNOWN 2 > > What does this do? There are 3 log levels - dump all matched entries, only the first matched and dump unknown packet data if needed. > >+#define XT_OSF_TTL_TRUE 0 /* True ip and fingerprint > >TTL comparison */ > >+#define XT_OSF_TTL_LESS 1 /* Check if ip TTL is less > >than fingerprint one */ > >+#define XT_OSF_TTL_NOCHECK 2 /* Do not compare ip and fingerprint > >TTL at all */ > > These seem redundant - having neither of TRUE or LESS seems > equivalent to NOCHECK. Perhaps thats the reason why its not > used at all :) Looking at the code, "TRUE" would be better > named as "EQUAL". There are only three types of TTL check - equal (for true), less than fingerprint one and when no check is performed at all. NOCHECK is actually used, but LESS one does not have a special check, but a default clause when neither TRUE or NOCHECK is specified. > >+struct xt_osf_info { > >+ char genre[MAXGENRELEN]; > >+ __u32 len; > >+ __u32 flags; > >+ __u32 loglevel; > >+ __u32 ttl; > >+}; > > Unless you're really really sure that this is not going to > change, please use netlink attributes. Similar for the other > ABI structures. It was not changed for the last 5 years, maybe even more. There are no other fields in the tcp header to match against :) > >+struct xt_osf_user_finger { > >+ struct xt_osf_wc wss; > >+ > >+ __u8 ttl, df; > >+ __u16 ss, mss; > >+ __u16 opt_num; > >+ > >+ char genre[MAXGENRELEN]; > >+ char version[MAXGENRELEN]; > >+ char subtype[MAXGENRELEN]; > >+ > >+ /* MAX_IPOPTLEN is maximum if all options are NOPs or EOLs */ > >+ struct xt_osf_opt opt[MAX_IPOPTLEN]; > > This really looks like you should use nested attributes. This will be an unneded complication - we should provide an option sequence, and maximum number of options is strickly determined by the protocol specification. How does having separate attributes for each option simplify the process? > >+/* Defines for IANA option kinds */ > >+ > >+enum iana_options { > >+ OSFOPT_EOL = 0, /* End of options */ > >+ OSFOPT_NOP, /* NOP */ > >+ OSFOPT_MSS, /* Maximum segment size */ > >+ OSFOPT_WSO, /* Window scale option */ > >+ OSFOPT_SACKP, /* SACK permitted */ > >+ OSFOPT_SACK, /* SACK */ > >+ OSFOPT_ECHO, > >+ OSFOPT_ECHOREPLY, > >+ OSFOPT_TS, /* Timestamp option */ > >+ OSFOPT_POCP, /* Partial Order Connection Permitted */ > >+ OSFOPT_POSP, /* Partial Order Service Profile */ > >+ > >+ /* Others are not used in the current OSF */ > >+ OSFOPT_EMPTY = 255, > >+}; > > Why do we need to duplicate these? Why duplicate? It is the only place of the constants describing used option numbers. include/net/tcp.h does not have 'partial order' options in particular. > >+config NETFILTER_XT_MATCH_OSF > >+ tristate '"osf" Passive OS fingerprint match' > >+ depends on NETFILTER_ADVANCED > > && NFNETLINK Will add. > >--- /dev/null > >+++ b/net/netfilter/xt_osf.c > >@@ -0,0 +1,469 @@ > >+/* > >+ * 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, write to the Free Software > >+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA > >+ */ > >+ > >+#include <linux/module.h> > >+#include <linux/kernel.h> > >+ > >+#include <linux/connector.h> > > Not needed. The remaining ones look like some (percpu?) could be > removed as well. Yup. > >+struct xt_osf_finger_storage > >+{ > > Please place the opening bracket consistently with the other > structure definitions. I.e. always on the new line? :) > >+ struct list_head finger_list; > >+ spinlock_t finger_lock; > >+}; > >+ > >+/* > >+ * Indexed by dont-fragment bit. > >+ * It is the only constant value in the fingerprint. > >+ */ > >+struct xt_osf_finger_storage xt_osf_fingers[2]; > > static Ok. > >+ > >+struct xt_osf_message { > >+ struct cn_msg cmsg; > >+ struct xt_osf_nlmsg nlmsg; > >+}; > > Unused. Yes. > >+static int xt_osf_setup_callback(struct sock *ctnl, struct sk_buff *skb, > >+ struct nlmsghdr *nlh, struct nlattr *osf_attrs[]) > >+{ > >+ struct xt_osf_user_finger *f; > >+ struct nfgenmsg *nfmsg = NLMSG_DATA(nlh); > >+ u16 delete = ntohs(nfmsg->res_id); > > This looks like abuse, we use message types to distinguish between > additions and deletions, alternative NLM_F_REPLACE. Why to introduce the whole new callback function and attribute when the only difference is to add or remove a processed entry? > >+ struct xt_osf_finger *kf = NULL, *sf; > >+ struct xt_osf_finger_storage *st; > >+ int err; > >+ > >+ if (!osf_attrs[OSF_ATTR_FINGER]) > >+ return -EINVAL; > >+ > >+ f = nla_data(osf_attrs[OSF_ATTR_FINGER]); > >+ st = &xt_osf_fingers[!!f->df]; > >+ > >+ /* > >+ * If 'delete' is set to 0 then we add attached fingerprint, > >+ * otherwise remove, and in this case we do not need to allocate > >data. > >+ */ > >+ if (!delete) { > >+ kf = kmalloc(sizeof(struct xt_osf_finger), GFP_KERNEL); > >+ if (!kf) > >+ return -ENOMEM; > >+ > >+ memcpy(&kf->finger, f, sizeof(struct xt_osf_user_finger)); > >+ } > >+ > >+ err = -ENOENT; > >+ > >+ rcu_read_lock(); > >+ list_for_each_entry_rcu(sf, &st->finger_list, finger_entry) { > >+ if (memcmp(&sf->finger, f, sizeof(struct > >xt_osf_user_finger))) > >+ continue; > >+ > >+ if (delete) { > >+ spin_lock_bh(&st->finger_lock); > > This lock looks useless, all changes are done in netlink context under > the nfnl mutex. Agree. > >+ list_del_rcu(&sf->finger_entry); > >+ spin_unlock_bh(&st->finger_lock); > >+ call_rcu(&sf->rcu_head, xt_osf_finger_free_rcu); > >+ } else { > >+ kfree(kf); > >+ kf = NULL; > >+ } > >+ > >+ err = 0; > >+ break; > >+ } > >+ > >+ if (kf) { > >+ spin_lock_bh(&st->finger_lock); Here too. > >+ list_add_tail_rcu(&kf->finger_entry, &st->finger_list); > >+ spin_unlock_bh(&st->finger_lock); > >+#if 0 > >+ printk(KERN_INFO "Added rule for %s:%s:%s.\n", > >+ kf->finger.genre, kf->finger.version, > >kf->finger.subtype); > >+#endif > >+ } > >+ rcu_read_unlock(); > >+ > >+ return 0; > >+} ... > >+static bool xt_osf_match_packet(const struct sk_buff *skb, > >+ const struct xt_match_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; > >+ const struct xt_osf_finger_storage *st; > >+ > >+ 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); > >+ > >+ if (optsize > sizeof(opts)) > >+ optsize = sizeof(opts); > >+ > >+ _optp = optp = skb_header_pointer(skb, ip_hdrlen(skb) + > >sizeof(struct tcphdr), > > Please break the line at 80 characters Will do. > >+ optsize, opts); > >+ } > >+ > >+ st = &xt_osf_fingers[df]; > >+ > >+ rcu_read_lock(); > >+ list_for_each_entry_rcu(kf, &st->finger_list, finger_entry) { > >+ 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)) { > >+ int foptsize, optnum; > >+ > >+ check_WSS = 0; > >+ > >+ switch (f->wss.wc) { > >+ case 0: > >+ check_WSS = 0; > >+ break; > >+ case 'S': > >+ check_WSS = 1; > >+ break; > >+ case 'T': > >+ check_WSS = 2; > >+ break; > >+ case '%': > >+ check_WSS = 3; > >+ break; > >+ default: > >+ check_WSS = 4; > >+ break; > >+ } > > This is really pushing my taste-buds. Whatever this does, please at > use symbolic constants so the reader at least has a chance to understand > it. That's a bit unlcear window size processing state machine. It links together knowledge about window-size, mss, mtu dependancy on plain size numbers and modulo operations (like window size is multiple of x bytes). > >+ if (check_WSS == 4) > >+ 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; > >+ > >+ 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(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 0: > >+ if (f->wss.val == 0 || window == > >f->wss.val) > >+ fmatch = FMATCH_OK; > >+ break; > >+ case 1: /* MSS */ > >+#define SMART_MSS_1 1460 > >+#define SMART_MSS_2 1448 > > Sigh. This entire function is completely unreadable and full of > unexplained magic. I'll stop here, please clean this before > resubmitting. This is a special hack for special modems, which can decrease mss, and since there is no common knowledge on how to differentiate them, there is a check against different types. This function is a core processing state machine, which checks received packet parameters and compares them against prebuilt set of rules, which include not only simple equal/not-equal, but also a bit more complex, like multiple of (various parameter, mss, window-size, plain number).
On Friday 2009-05-29 10:59, Evgeniy Polyakov wrote: >> >+/* Defines for IANA option kinds */ >> >+ >> >+enum iana_options { >> >+ OSFOPT_EOL = 0, /* End of options */ >> >+ OSFOPT_NOP, /* NOP */ >> >+ OSFOPT_MSS, /* Maximum segment size */ >> >+ OSFOPT_WSO, /* Window scale option */ >> >+ OSFOPT_SACKP, /* SACK permitted */ >> >+ OSFOPT_SACK, /* SACK */ >> >+ OSFOPT_ECHO, >> >+ OSFOPT_ECHOREPLY, >> >+ OSFOPT_TS, /* Timestamp option */ >> >+ OSFOPT_POCP, /* Partial Order Connection Permitted */ >> >+ OSFOPT_POSP, /* Partial Order Service Profile */ >> >+ >> >+ /* Others are not used in the current OSF */ >> >+ OSFOPT_EMPTY = 255, >> >+}; >> >> Why do we need to duplicate these? > >Why duplicate? It is the only place of the constants describing used >option numbers. include/net/tcp.h does not have 'partial order' options >in particular. Then you do one of these: 1. add TCPOPT_POCP/POSP to tcp.h or 2. define it locally: #include <net/tcp.h> enum { TCPOPT_POCP = 9, TCPOPT_POSP = 10, }; >> >+config NETFILTER_XT_MATCH_OSF >> >+ tristate '"osf" Passive OS fingerprint match' >> >+ depends on NETFILTER_ADVANCED >> >> && NFNETLINK > >Will add. Does it really need to depend on nfnetlink? Even if I just want to have it dumped to syslog? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Jan. On Fri, May 29, 2009 at 11:49:51AM +0200, Jan Engelhardt (jengelh@medozas.de) wrote: > >> >+config NETFILTER_XT_MATCH_OSF > >> >+ tristate '"osf" Passive OS fingerprint match' > >> >+ depends on NETFILTER_ADVANCED > >> > >> && NFNETLINK > > > >Will add. > > Does it really need to depend on nfnetlink? Even if I just want to > have it dumped to syslog? OSF is configured by nfnetlink now.
Evgeniy Polyakov wrote: > Hi Patrick. > > Thanks for your comments. > > On Wed, May 27, 2009 at 06:28:16PM +0200, Patrick McHardy (kaber@trash.net) wrote: >>> +#define XT_OSF_TTL_TRUE 0 /* True ip and fingerprint >>> TTL comparison */ >>> +#define XT_OSF_TTL_LESS 1 /* Check if ip TTL is less >>> than fingerprint one */ >>> +#define XT_OSF_TTL_NOCHECK 2 /* Do not compare ip and fingerprint >>> TTL at all */ >> These seem redundant - having neither of TRUE or LESS seems >> equivalent to NOCHECK. Perhaps thats the reason why its not >> used at all :) Looking at the code, "TRUE" would be better >> named as "EQUAL". > > There are only three types of TTL check - equal (for true), less than > fingerprint one and when no check is performed at all. NOCHECK is > actually used, but LESS one does not have a special check, but a default > clause when neither TRUE or NOCHECK is specified. OK, thanks for the explanation. >>> +struct xt_osf_user_finger { >>> + struct xt_osf_wc wss; >>> + >>> + __u8 ttl, df; >>> + __u16 ss, mss; >>> + __u16 opt_num; >>> + >>> + char genre[MAXGENRELEN]; >>> + char version[MAXGENRELEN]; >>> + char subtype[MAXGENRELEN]; >>> + >>> + /* MAX_IPOPTLEN is maximum if all options are NOPs or EOLs */ >>> + struct xt_osf_opt opt[MAX_IPOPTLEN]; >> This really looks like you should use nested attributes. > > This will be an unneded complication - we should provide an option > sequence, and maximum number of options is strickly determined by > the protocol specification. How does having separate attributes for each > option simplify the process? It doesn't, but it provides more flexibility which might make things easier in case someone decides to add IPv6 support. >>> +/* Defines for IANA option kinds */ >>> + >>> +enum iana_options { >>> + OSFOPT_EOL = 0, /* End of options */ >>> + OSFOPT_NOP, /* NOP */ >>> + OSFOPT_MSS, /* Maximum segment size */ >>> + OSFOPT_WSO, /* Window scale option */ >>> + OSFOPT_SACKP, /* SACK permitted */ >>> + OSFOPT_SACK, /* SACK */ >>> + OSFOPT_ECHO, >>> + OSFOPT_ECHOREPLY, >>> + OSFOPT_TS, /* Timestamp option */ >>> + OSFOPT_POCP, /* Partial Order Connection Permitted */ >>> + OSFOPT_POSP, /* Partial Order Service Profile */ >>> + >>> + /* Others are not used in the current OSF */ >>> + OSFOPT_EMPTY = 255, >>> +}; >> Why do we need to duplicate these? > > Why duplicate? It is the only place of the constants describing used > option numbers. include/net/tcp.h does not have 'partial order' options > in particular. Indeed, I noticed this after sending my mail. >>> +struct xt_osf_finger_storage >>> +{ >> Please place the opening bracket consistently with the other >> structure definitions. > > I.e. always on the new line? :) Just keep it consistent within your file, though I personally prefer to keep it inconsistent with some of the other netfilter files and not use a new line :) >>> +static int xt_osf_setup_callback(struct sock *ctnl, struct sk_buff *skb, >>> + struct nlmsghdr *nlh, struct nlattr *osf_attrs[]) >>> +{ >>> + struct xt_osf_user_finger *f; >>> + struct nfgenmsg *nfmsg = NLMSG_DATA(nlh); >>> + u16 delete = ntohs(nfmsg->res_id); >> This looks like abuse, we use message types to distinguish between >> additions and deletions, alternative NLM_F_REPLACE. > > Why to introduce the whole new callback function and attribute when the > only difference is to add or remove a processed entry? Sticking to the defined semantics avoids the need for special-casing in generic code like libnl. A new function also doesn't seem like a loss at all, the only common part between addition and removal appears to be the iteration. >>> + if (totlen == f->ss && xt_osf_ttl(skb, info, f->ttl)) { >>> + int foptsize, optnum; >>> + >>> + check_WSS = 0; >>> + >>> + switch (f->wss.wc) { >>> + case 0: >>> + check_WSS = 0; >>> + break; >>> + case 'S': >>> + check_WSS = 1; >>> + break; >>> + case 'T': >>> + check_WSS = 2; >>> + break; >>> + case '%': >>> + check_WSS = 3; >>> + break; >>> + default: >>> + check_WSS = 4; >>> + break; >>> + } >> This is really pushing my taste-buds. Whatever this does, please at >> use symbolic constants so the reader at least has a chance to understand >> it. > > That's a bit unlcear window size processing state machine. > It links together knowledge about window-size, mss, mtu dependancy on > plain size numbers and modulo operations (like window size is multiple > of x bytes). It very much reminds me of iptables userspace option parsing :| Please at least use symbolic names for the different cases. Why does it have to be mapped in the kernel at all? The raw value of f->wss.wc doesn't seem to be used anywhere else. >>> +#define SMART_MSS_1 1460 >>> +#define SMART_MSS_2 1448 >> Sigh. This entire function is completely unreadable and full of >> unexplained magic. I'll stop here, please clean this before >> resubmitting. > > This is a special hack for special modems, which can decrease mss, and > since there is no common knowledge on how to differentiate them, there > is a check against different types. Please explain what exactly it does in a comment. Would it make sense to have the exact values supplied by userspace? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi. On Wed, May 27, 2009 at 06:28:16PM +0200, Patrick McHardy (kaber@trash.net) wrote: > >You will find something like this in the syslog: > >Windows [2000:SP3:Windows XP Pro SP1, 2000 SP3]: 11.22.33.55:4024 -> > >11.22.33.44:139 hops=4 > >Linux [2.5:]: 1.2.3.4:44448 -> 11.22.33.44:22 hops=4 > > Please convert this to use nf_log_packet(). That's hard - there is no hook number in the match function, so we do not really know if it is forward, input or prerouting. In the version I'm about to send I fixed all rised issues except multiple attributes - if there will be a need to extend attribute list we can always switch them into new attribute except current all-in-one.
Evgeniy Polyakov wrote: > Hi. > > On Wed, May 27, 2009 at 06:28:16PM +0200, Patrick McHardy (kaber@trash.net) wrote: >>> You will find something like this in the syslog: >>> Windows [2000:SP3:Windows XP Pro SP1, 2000 SP3]: 11.22.33.55:4024 -> >>> 11.22.33.44:139 hops=4 >>> Linux [2.5:]: 1.2.3.4:44448 -> 11.22.33.44:22 hops=4 >> Please convert this to use nf_log_packet(). > > That's hard - there is no hook number in the match function, so we do > not really know if it is forward, input or prerouting. This is really needed, spamming the ring buffer is not a good option. I'd say just add the hook number to xt_match_param. Its a bit inconsistent anyways that we're handing it to checkentry for validation, but not to the match function. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Jun 04, 2009 at 01:53:05PM +0200, Patrick McHardy (kaber@trash.net) wrote: > >That's hard - there is no hook number in the match function, so we do > >not really know if it is forward, input or prerouting. > > This is really needed, spamming the ring buffer is not a good option. > > I'd say just add the hook number to xt_match_param. Its a bit > inconsistent anyways that we're handing it to checkentry for > validation, but not to the match function. Doesn't checkentry receive a mask of all possible hooks? There is still no per-packet hook number. Although we can always use INPUT hook since its the most widely used one. And drop a comment about this abuse.
Evgeniy Polyakov wrote: > On Thu, Jun 04, 2009 at 01:53:05PM +0200, Patrick McHardy (kaber@trash.net) wrote: >>> That's hard - there is no hook number in the match function, so we do >>> not really know if it is forward, input or prerouting. >> This is really needed, spamming the ring buffer is not a good option. >> >> I'd say just add the hook number to xt_match_param. Its a bit >> inconsistent anyways that we're handing it to checkentry for >> validation, but not to the match function. > > Doesn't checkentry receive a mask of all possible hooks? There is still > no per-packet hook number. Although we can always use INPUT hook since > its the most widely used one. And drop a comment about this abuse. Thats not what I meant. struct xt_match_param is passed to the ->match() callbacks from *t_do_table(). This is where you can add the real hook number to have it available in ->match(). (Forgot to mention earlier: please in a seperate patch and adjusting all *tables copies) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/netfilter/nfnetlink.h b/include/linux/netfilter/nfnetlink.h index c600083..bb9c9ae 100644 --- a/include/linux/netfilter/nfnetlink.h +++ b/include/linux/netfilter/nfnetlink.h @@ -46,7 +46,8 @@ struct nfgenmsg { #define NFNL_SUBSYS_CTNETLINK_EXP 2 #define NFNL_SUBSYS_QUEUE 3 #define NFNL_SUBSYS_ULOG 4 -#define NFNL_SUBSYS_COUNT 5 +#define NFNL_SUBSYS_OSF 5 +#define NFNL_SUBSYS_COUNT 6 #ifdef __KERNEL__ diff --git a/include/linux/netfilter/xt_osf.h b/include/linux/netfilter/xt_osf.h new file mode 100644 index 0000000..11903a9 --- /dev/null +++ b/include/linux/netfilter/xt_osf.h @@ -0,0 +1,119 @@ +/* + * Copyright (c) 2003+ Evgeniy Polyakov <johnpol@2ka.mxt.ru> + * + * + * 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, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ + +#ifndef _XT_OSF_H +#define _XT_OSF_H + +#define MAXGENRELEN 32 +#define MAXDETLEN 64 + +#define XT_OSF_GENRE (1<<0) +#define XT_OSF_TTL (1<<1) +#define XT_OSF_LOG (1<<2) +#define XT_OSF_UNUSED (1<<3) +#define XT_OSF_CONNECTOR (1<<4) +#define XT_OSF_INVERT (1<<5) + +#define XT_OSF_LOGLEVEL_ALL 0 +#define XT_OSF_LOGLEVEL_FIRST 1 +#define XT_OSF_LOGLEVEL_ALL_KNOWN 2 + +#define XT_OSF_TTL_TRUE 0 /* True ip and fingerprint TTL comparison */ +#define XT_OSF_TTL_LESS 1 /* Check if ip TTL is less than fingerprint one */ +#define XT_OSF_TTL_NOCHECK 2 /* Do not compare ip and fingerprint TTL at all */ + +struct xt_osf_info { + char genre[MAXGENRELEN]; + __u32 len; + __u32 flags; + __u32 loglevel; + __u32 ttl; +}; + +/* + * Wildcard MSS (kind of). + * It is used to implement a state machine for the different wildcard values + * of the MSS and window sizes. + */ +struct xt_osf_wc { + __u32 wc; + __u32 val; +}; + +/* + * This struct represents IANA options + * http://www.iana.org/assignments/tcp-parameters + */ +struct xt_osf_opt { + __u16 kind, length; + struct xt_osf_wc wc; +}; + +struct xt_osf_user_finger { + struct xt_osf_wc wss; + + __u8 ttl, df; + __u16 ss, mss; + __u16 opt_num; + + char genre[MAXGENRELEN]; + char version[MAXGENRELEN]; + char subtype[MAXGENRELEN]; + + /* MAX_IPOPTLEN is maximum if all options are NOPs or EOLs */ + struct xt_osf_opt opt[MAX_IPOPTLEN]; +}; + +struct xt_osf_nlmsg { + struct xt_osf_user_finger f; + struct iphdr ip; + struct tcphdr tcp; +}; + +/* Defines for IANA option kinds */ + +enum iana_options { + OSFOPT_EOL = 0, /* End of options */ + OSFOPT_NOP, /* NOP */ + OSFOPT_MSS, /* Maximum segment size */ + OSFOPT_WSO, /* Window scale option */ + OSFOPT_SACKP, /* SACK permitted */ + OSFOPT_SACK, /* SACK */ + OSFOPT_ECHO, + OSFOPT_ECHOREPLY, + OSFOPT_TS, /* Timestamp option */ + OSFOPT_POCP, /* Partial Order Connection Permitted */ + OSFOPT_POSP, /* Partial Order Service Profile */ + + /* Others are not used in the current OSF */ + OSFOPT_EMPTY = 255, +}; + +enum xt_osf_msg_types { + OSF_MSG_SETUP, + OSF_MSG_MAX, +}; + +enum xt_osf_attr_type { + OSF_ATTR_UNSPEC, + OSF_ATTR_FINGER, + OSF_ATTR_MAX, +}; + +#endif /* _XT_OSF_H */ diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig index 2329c5f..b0273f9 100644 --- a/net/netfilter/Kconfig +++ b/net/netfilter/Kconfig @@ -916,6 +916,19 @@ config NETFILTER_XT_MATCH_U32 Details and examples are in the kernel module source. +config NETFILTER_XT_MATCH_OSF + tristate '"osf" Passive OS fingerprint match' + depends on NETFILTER_ADVANCED + help + This option selects the Passive OS Fingerprinting match module + that allows to passively match the remote operating system by + analyzing incoming TCP SYN packets. + + Rules and loading software can be downloaded from + http://www.ioremap.net/projects/osf + + To compile it as a module, choose M here. If unsure, say N. + endif # NETFILTER_XTABLES endmenu diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile index 6282060..49f62ee 100644 --- a/net/netfilter/Makefile +++ b/net/netfilter/Makefile @@ -77,6 +77,7 @@ obj-$(CONFIG_NETFILTER_XT_MATCH_LIMIT) += xt_limit.o obj-$(CONFIG_NETFILTER_XT_MATCH_MAC) += xt_mac.o obj-$(CONFIG_NETFILTER_XT_MATCH_MARK) += xt_mark.o obj-$(CONFIG_NETFILTER_XT_MATCH_MULTIPORT) += xt_multiport.o +obj-$(CONFIG_NETFILTER_XT_MATCH_OSF) += xt_osf.o obj-$(CONFIG_NETFILTER_XT_MATCH_OWNER) += xt_owner.o obj-$(CONFIG_NETFILTER_XT_MATCH_PHYSDEV) += xt_physdev.o obj-$(CONFIG_NETFILTER_XT_MATCH_PKTTYPE) += xt_pkttype.o diff --git a/net/netfilter/xt_osf.c b/net/netfilter/xt_osf.c new file mode 100644 index 0000000..71b5eac --- /dev/null +++ b/net/netfilter/xt_osf.c @@ -0,0 +1,469 @@ +/* + * 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, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ + +#include <linux/module.h> +#include <linux/kernel.h> + +#include <linux/connector.h> +#include <linux/if.h> +#include <linux/inetdevice.h> +#include <linux/ip.h> +#include <linux/list.h> +#include <linux/percpu.h> +#include <linux/rculist.h> +#include <linux/smp.h> +#include <linux/skbuff.h> +#include <linux/slab.h> +#include <linux/spinlock.h> +#include <linux/tcp.h> +#include <linux/types.h> + +#include <net/ip.h> +#include <net/tcp.h> + +#include <linux/netfilter/nfnetlink.h> +#include <linux/netfilter/x_tables.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, +}; + +struct xt_osf_finger_storage +{ + struct list_head finger_list; + spinlock_t finger_lock; +}; + +/* + * Indexed by dont-fragment bit. + * It is the only constant value in the fingerprint. + */ +struct xt_osf_finger_storage xt_osf_fingers[2]; + +struct xt_osf_message { + struct cn_msg cmsg; + struct xt_osf_nlmsg nlmsg; +}; + +static const struct nla_policy xt_osf_policy[OSF_ATTR_MAX + 1] = { + [OSF_ATTR_FINGER] = { .len = sizeof(struct xt_osf_user_finger) }, +}; + +static void xt_osf_finger_free_rcu(struct rcu_head *rcu_head) +{ + struct xt_osf_finger *f = container_of(rcu_head, struct xt_osf_finger, rcu_head); + + kfree(f); +} + +static int xt_osf_setup_callback(struct sock *ctnl, struct sk_buff *skb, + struct nlmsghdr *nlh, struct nlattr *osf_attrs[]) +{ + struct xt_osf_user_finger *f; + struct nfgenmsg *nfmsg = NLMSG_DATA(nlh); + u16 delete = ntohs(nfmsg->res_id); + struct xt_osf_finger *kf = NULL, *sf; + struct xt_osf_finger_storage *st; + int err; + + if (!osf_attrs[OSF_ATTR_FINGER]) + return -EINVAL; + + f = nla_data(osf_attrs[OSF_ATTR_FINGER]); + st = &xt_osf_fingers[!!f->df]; + + /* + * If 'delete' is set to 0 then we add attached fingerprint, + * otherwise remove, and in this case we do not need to allocate data. + */ + if (!delete) { + kf = kmalloc(sizeof(struct xt_osf_finger), GFP_KERNEL); + if (!kf) + return -ENOMEM; + + memcpy(&kf->finger, f, sizeof(struct xt_osf_user_finger)); + } + + err = -ENOENT; + + rcu_read_lock(); + list_for_each_entry_rcu(sf, &st->finger_list, finger_entry) { + if (memcmp(&sf->finger, f, sizeof(struct xt_osf_user_finger))) + continue; + + if (delete) { + spin_lock_bh(&st->finger_lock); + list_del_rcu(&sf->finger_entry); + spin_unlock_bh(&st->finger_lock); + call_rcu(&sf->rcu_head, xt_osf_finger_free_rcu); + } else { + kfree(kf); + kf = NULL; + } + + err = 0; + break; + } + + if (kf) { + spin_lock_bh(&st->finger_lock); + list_add_tail_rcu(&kf->finger_entry, &st->finger_list); + spin_unlock_bh(&st->finger_lock); +#if 0 + printk(KERN_INFO "Added rule for %s:%s:%s.\n", + kf->finger.genre, kf->finger.version, kf->finger.subtype); +#endif + } + rcu_read_unlock(); + + return 0; +} + +static const struct nfnl_callback xt_osf_nfnetlink_callbacks[OSF_MSG_MAX] = { + [OSF_MSG_SETUP] = { + .call = xt_osf_setup_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(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); + + in_dev_put(in_dev); + return ret; + } + } + + return ip->ttl == f_ttl; +} + +static bool xt_osf_match_packet(const struct sk_buff *skb, + const struct xt_match_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; + const struct xt_osf_finger_storage *st; + + 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); + + if (optsize > sizeof(opts)) + optsize = sizeof(opts); + + _optp = optp = skb_header_pointer(skb, ip_hdrlen(skb) + sizeof(struct tcphdr), + optsize, opts); + } + + st = &xt_osf_fingers[df]; + + rcu_read_lock(); + list_for_each_entry_rcu(kf, &st->finger_list, finger_entry) { + 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)) { + int foptsize, optnum; + + check_WSS = 0; + + switch (f->wss.wc) { + case 0: + check_WSS = 0; + break; + case 'S': + check_WSS = 1; + break; + case 'T': + check_WSS = 2; + break; + case '%': + check_WSS = 3; + break; + default: + check_WSS = 4; + break; + } + if (check_WSS == 4) + 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; + + 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(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 0: + if (f->wss.val == 0 || window == f->wss.val) + fmatch = FMATCH_OK; + break; + case 1: /* MSS */ +#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 2: /* 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 3: /* MOD */ + if ((window % f->wss.val) == 0) + fmatch = FMATCH_OK; + break; + } + } + + if (fmatch != FMATCH_OK) + continue; + + fcount++; + if (info->flags & XT_OSF_LOG) + printk(KERN_INFO "%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 | XT_OSF_CONNECTOR))) { + unsigned int i; + struct xt_osf_user_finger fg; + + memset(&fg, 0, sizeof(fg)); +#if 1 + if (info->flags & XT_OSF_LOG) { + if (info->loglevel != XT_OSF_LOGLEVEL_ALL_KNOWN) + printk(KERN_INFO "Unknown: win: %u, mss: %u, " + "totlen: %u, df: %d, ttl: %u : ", + window, mss, totlen, df, ip->ttl); + else + printk(KERN_INFO ""); + if (_optp) { + optp = _optp; + for (i = 0; i < optsize; i++) + printk("%02X ", optp[i]); + } + + printk("%pi4:%u -> %pi4:%u\n", + &ip->saddr, ntohs(tcp->source), + &ip->daddr, ntohs(tcp->dest)); + } +#endif + } + + 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) { + struct xt_osf_finger_storage *st = &xt_osf_fingers[i]; + + INIT_LIST_HEAD(&st->finger_list); + spin_lock_init(&st->finger_lock); + } + + err = nfnetlink_subsys_register(&xt_osf_nfnetlink); + if (err < 0) { + printk(KERN_ERR "Failed (%d) to register OSF nsfnetlink helper.\n", err); + goto err_out_exit; + } + + err = xt_register_match(&xt_osf_match); + if (err) { + printk(KERN_ERR "Failed (%d) to register OS fingerprint " + "matching module.\n", err); + goto err_out_remove; + } + + printk(KERN_INFO "Started passive OS fingerprint matching module.\n"); + + 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) { + struct xt_osf_finger_storage *st = &xt_osf_fingers[i]; + + list_for_each_entry_rcu(f, &st->finger_list, finger_entry) { + list_del_rcu(&f->finger_entry); + call_rcu(&f->rcu_head, xt_osf_finger_free_rcu); + } + } + rcu_read_unlock(); + + rcu_barrier(); + + printk(KERN_INFO "Passive OS fingerprint matching module finished.\n"); +} + +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_NFNL_SUBSYS(NFNL_SUBSYS_OSF);
Hi. Passive OS fingerprinting netfilter module allows to passively detect remote OS and perform various netfilter actions based on that knowledge. This module compares some data (WS, MSS, options and it's order, ttl, df and others) from packets with SYN bit set with dynamically loaded OS fingerprints. Fingerprint matching rules can be downloaded from OpenBSD source tree and loaded via netfilter netlink subsystem into the kernel via special util found in archive. Archive contains library file (also attached), which was shipped with iptables extensions some time ago (at least when ipt_osf existed in patch-o-matic). Both patch and library (attached) incorporated all requested features and extensions, namely nfnetlink implementation, codying style cleanups, RCU issues and others. Attached patch was rebased against current vanilla tree. Fingerprints can be downloaded from http://www.openbsd.org/cgi-bin/cvsweb/src/etc/pf.os Example usage: # modrpobe xt_osf # ./nfnl_osf -f ./pf.os -d switch removes fingerprints # iptables -I INPUT -j ACCEPT -p tcp -m osf --genre Linux --log 0 --ttl 2 You will find something like this in the syslog: Windows [2000:SP3:Windows XP Pro SP1, 2000 SP3]: 11.22.33.55:4024 -> 11.22.33.44:139 hops=4 Linux [2.5:]: 1.2.3.4:44448 -> 11.22.33.44:22 hops=4 Please consider for inclusion. Thank you. Passive OS fingerprint homepage (archives, examples): http://www.ioremap.net/projects/osf Signed-off-by: Evgeniy Polyakov <zbr@ioremap.net> include/linux/netfilter/nfnetlink.h | 3 +- include/linux/netfilter/xt_osf.h | 119 +++++++++ net/netfilter/Kconfig | 13 + net/netfilter/Makefile | 1 + net/netfilter/xt_osf.c | 469 +++++++++++++++++++++++++++++++++++ 5 files changed, 604 insertions(+), 1 deletions(-)