From bfb15f2a95cbbc548b59abf8007d0fdb35fdfee5 Mon Sep 17 00:00:00 2001 From: Fernando Fernandez Mancera Date: Thu, 3 May 2018 14:05:40 +0200 Subject: netfilter: extract Passive OS fingerprint infrastructure from xt_osf Add nf_osf_ttl() and nf_osf_match() into nf_osf.c to prepare for nf_tables support. Signed-off-by: Fernando Fernandez Mancera Signed-off-by: Pablo Neira Ayuso --- net/netfilter/Kconfig | 4 + net/netfilter/Makefile | 1 + net/netfilter/nf_osf.c | 218 +++++++++++++++++++++++++++++++++++++++++++++++++ net/netfilter/xt_osf.c | 202 +-------------------------------------------- 4 files changed, 225 insertions(+), 200 deletions(-) create mode 100644 net/netfilter/nf_osf.c (limited to 'net') diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig index f66586fb41cd..e25cdb3d51cb 100644 --- a/net/netfilter/Kconfig +++ b/net/netfilter/Kconfig @@ -444,6 +444,9 @@ config NETFILTER_SYNPROXY endif # NF_CONNTRACK +config NF_OSF + tristate 'Passive OS fingerprint infrastructure' + config NF_TABLES select NETFILTER_NETLINK tristate "Netfilter nf_tables support" @@ -1358,6 +1361,7 @@ config NETFILTER_XT_MATCH_NFACCT config NETFILTER_XT_MATCH_OSF tristate '"osf" Passive OS fingerprint match' depends on NETFILTER_ADVANCED && NETFILTER_NETLINK + select NF_OSF help This option selects the Passive OS Fingerprinting match module that allows to passively match the remote operating system by diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile index b37ce0bc9ab7..1aa710b5d384 100644 --- a/net/netfilter/Makefile +++ b/net/netfilter/Makefile @@ -101,6 +101,7 @@ obj-$(CONFIG_NFT_HASH) += nft_hash.o obj-$(CONFIG_NFT_FIB) += nft_fib.o obj-$(CONFIG_NFT_FIB_INET) += nft_fib_inet.o obj-$(CONFIG_NFT_FIB_NETDEV) += nft_fib_netdev.o +obj-$(CONFIG_NF_OSF) += nf_osf.o # nf_tables netdev obj-$(CONFIG_NFT_DUP_NETDEV) += nft_dup_netdev.o diff --git a/net/netfilter/nf_osf.c b/net/netfilter/nf_osf.c new file mode 100644 index 000000000000..5ba5c7bef2f9 --- /dev/null +++ b/net/netfilter/nf_osf.c @@ -0,0 +1,218 @@ +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt +#include +#include + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include + +#include +#include +#include +#include + +static inline int nf_osf_ttl(const struct sk_buff *skb, + const struct nf_osf_info *info, + unsigned char f_ttl) +{ + const struct iphdr *ip = ip_hdr(skb); + + if (info->flags & NF_OSF_TTL) { + if (info->ttl == NF_OSF_TTL_TRUE) + return ip->ttl == f_ttl; + if (info->ttl == NF_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; +} + +bool +nf_osf_match(const struct sk_buff *skb, u_int8_t family, + int hooknum, struct net_device *in, struct net_device *out, + const struct nf_osf_info *info, struct net *net, + const struct list_head *nf_osf_fingers) +{ + const unsigned char *optp = NULL, *_optp = NULL; + unsigned int optsize = 0, check_WSS = 0; + int fmatch = FMATCH_WRONG, fcount = 0; + const struct iphdr *ip = ip_hdr(skb); + const struct nf_osf_user_finger *f; + unsigned char opts[MAX_IPOPTLEN]; + const struct nf_osf_finger *kf; + u16 window, totlen, mss = 0; + const struct tcphdr *tcp; + struct tcphdr _tcph; + bool df; + + 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); + } + + list_for_each_entry_rcu(kf, &nf_osf_fingers[df], finger_entry) { + int foptsize, optnum; + + f = &kf->finger; + + if (!(info->flags & NF_OSF_LOG) && strcmp(info->genre, f->genre)) + continue; + + optp = _optp; + fmatch = FMATCH_WRONG; + + if (totlen != f->ss || !nf_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; + + 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: + 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 & NF_OSF_LOG) + nf_log_packet(net, family, hooknum, skb, + in, 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 & NF_OSF_LOG) && + info->loglevel == NF_OSF_LOGLEVEL_FIRST) + break; + } + + if (!fcount && (info->flags & NF_OSF_LOG)) + nf_log_packet(net, family, hooknum, skb, in, 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; +} +EXPORT_SYMBOL_GPL(nf_osf_match); + +MODULE_LICENSE("GPL"); diff --git a/net/netfilter/xt_osf.c b/net/netfilter/xt_osf.c index a34f314a8c23..9cfef73b4107 100644 --- a/net/netfilter/xt_osf.c +++ b/net/netfilter/xt_osf.c @@ -37,21 +37,6 @@ #include #include -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. @@ -164,200 +149,17 @@ static const struct nfnetlink_subsystem xt_osf_nfnetlink = { .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 = xt_net(p); 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); - } - - 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; - - 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: - 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, xt_family(p), xt_hooknum(p), skb, - xt_in(p), xt_out(p), 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; - } - - if (!fcount && (info->flags & XT_OSF_LOG)) - nf_log_packet(net, xt_family(p), xt_hooknum(p), skb, xt_in(p), - xt_out(p), 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; + return nf_osf_match(skb, xt_family(p), xt_hooknum(p), xt_in(p), + xt_out(p), info, net, xt_osf_fingers); } static struct xt_match xt_osf_match = { -- cgit v1.2.3