diff options
author | Fernando Fernandez Mancera <ffmancera@riseup.net> | 2018-05-03 15:05:40 +0300 |
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committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2018-05-07 01:02:11 +0300 |
commit | bfb15f2a95cbbc548b59abf8007d0fdb35fdfee5 (patch) | |
tree | fc0581006bc8e19f17e77f4b116434e8450a0bc2 /net/netfilter/xt_osf.c | |
parent | 3f9c56a581b96d8117922c4fd8221687fd649f9b (diff) | |
download | linux-bfb15f2a95cbbc548b59abf8007d0fdb35fdfee5.tar.xz |
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 <ffmancera@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'net/netfilter/xt_osf.c')
-rw-r--r-- | net/netfilter/xt_osf.c | 202 |
1 files changed, 2 insertions, 200 deletions
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 <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. @@ -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 = { |