bfb15f2a95
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>
219 lines
5 KiB
C
219 lines
5 KiB
C
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/capability.h>
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#include <linux/if.h>
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#include <linux/inetdevice.h>
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#include <linux/ip.h>
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#include <linux/list.h>
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#include <linux/rculist.h>
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#include <linux/skbuff.h>
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#include <linux/slab.h>
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#include <linux/tcp.h>
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#include <net/ip.h>
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#include <net/tcp.h>
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#include <linux/netfilter/nfnetlink.h>
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#include <linux/netfilter/x_tables.h>
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#include <net/netfilter/nf_log.h>
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#include <linux/netfilter/nf_osf.h>
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static inline int nf_osf_ttl(const struct sk_buff *skb,
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const struct nf_osf_info *info,
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unsigned char f_ttl)
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{
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const struct iphdr *ip = ip_hdr(skb);
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if (info->flags & NF_OSF_TTL) {
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if (info->ttl == NF_OSF_TTL_TRUE)
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return ip->ttl == f_ttl;
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if (info->ttl == NF_OSF_TTL_NOCHECK)
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return 1;
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else if (ip->ttl <= f_ttl)
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return 1;
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else {
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struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
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int ret = 0;
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for_ifa(in_dev) {
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if (inet_ifa_match(ip->saddr, ifa)) {
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ret = (ip->ttl == f_ttl);
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break;
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}
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}
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endfor_ifa(in_dev);
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return ret;
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}
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}
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return ip->ttl == f_ttl;
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}
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bool
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nf_osf_match(const struct sk_buff *skb, u_int8_t family,
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int hooknum, struct net_device *in, struct net_device *out,
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const struct nf_osf_info *info, struct net *net,
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const struct list_head *nf_osf_fingers)
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{
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const unsigned char *optp = NULL, *_optp = NULL;
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unsigned int optsize = 0, check_WSS = 0;
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int fmatch = FMATCH_WRONG, fcount = 0;
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const struct iphdr *ip = ip_hdr(skb);
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const struct nf_osf_user_finger *f;
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unsigned char opts[MAX_IPOPTLEN];
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const struct nf_osf_finger *kf;
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u16 window, totlen, mss = 0;
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const struct tcphdr *tcp;
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struct tcphdr _tcph;
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bool df;
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tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);
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if (!tcp)
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return false;
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if (!tcp->syn)
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return false;
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totlen = ntohs(ip->tot_len);
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df = ntohs(ip->frag_off) & IP_DF;
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window = ntohs(tcp->window);
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if (tcp->doff * 4 > sizeof(struct tcphdr)) {
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optsize = tcp->doff * 4 - sizeof(struct tcphdr);
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_optp = optp = skb_header_pointer(skb, ip_hdrlen(skb) +
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sizeof(struct tcphdr), optsize, opts);
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}
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list_for_each_entry_rcu(kf, &nf_osf_fingers[df], finger_entry) {
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int foptsize, optnum;
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f = &kf->finger;
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if (!(info->flags & NF_OSF_LOG) && strcmp(info->genre, f->genre))
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continue;
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optp = _optp;
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fmatch = FMATCH_WRONG;
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if (totlen != f->ss || !nf_osf_ttl(skb, info, f->ttl))
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continue;
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/*
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* Should not happen if userspace parser was written correctly.
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*/
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if (f->wss.wc >= OSF_WSS_MAX)
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continue;
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/* Check options */
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foptsize = 0;
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for (optnum = 0; optnum < f->opt_num; ++optnum)
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foptsize += f->opt[optnum].length;
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if (foptsize > MAX_IPOPTLEN ||
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optsize > MAX_IPOPTLEN ||
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optsize != foptsize)
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continue;
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check_WSS = f->wss.wc;
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for (optnum = 0; optnum < f->opt_num; ++optnum) {
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if (f->opt[optnum].kind == (*optp)) {
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__u32 len = f->opt[optnum].length;
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const __u8 *optend = optp + len;
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fmatch = FMATCH_OK;
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switch (*optp) {
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case OSFOPT_MSS:
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mss = optp[3];
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mss <<= 8;
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mss |= optp[2];
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mss = ntohs((__force __be16)mss);
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break;
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case OSFOPT_TS:
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break;
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}
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optp = optend;
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} else
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fmatch = FMATCH_OPT_WRONG;
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if (fmatch != FMATCH_OK)
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break;
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}
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if (fmatch != FMATCH_OPT_WRONG) {
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fmatch = FMATCH_WRONG;
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switch (check_WSS) {
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case OSF_WSS_PLAIN:
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if (f->wss.val == 0 || window == f->wss.val)
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fmatch = FMATCH_OK;
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break;
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case OSF_WSS_MSS:
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/*
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* Some smart modems decrease mangle MSS to
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* SMART_MSS_2, so we check standard, decreased
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* and the one provided in the fingerprint MSS
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* values.
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*/
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#define SMART_MSS_1 1460
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#define SMART_MSS_2 1448
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if (window == f->wss.val * mss ||
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window == f->wss.val * SMART_MSS_1 ||
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window == f->wss.val * SMART_MSS_2)
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fmatch = FMATCH_OK;
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break;
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case OSF_WSS_MTU:
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if (window == f->wss.val * (mss + 40) ||
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window == f->wss.val * (SMART_MSS_1 + 40) ||
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window == f->wss.val * (SMART_MSS_2 + 40))
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fmatch = FMATCH_OK;
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break;
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case OSF_WSS_MODULO:
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if ((window % f->wss.val) == 0)
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fmatch = FMATCH_OK;
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break;
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}
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}
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if (fmatch != FMATCH_OK)
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continue;
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fcount++;
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if (info->flags & NF_OSF_LOG)
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nf_log_packet(net, family, hooknum, skb,
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in, out, NULL,
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"%s [%s:%s] : %pI4:%d -> %pI4:%d hops=%d\n",
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f->genre, f->version, f->subtype,
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&ip->saddr, ntohs(tcp->source),
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&ip->daddr, ntohs(tcp->dest),
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f->ttl - ip->ttl);
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if ((info->flags & NF_OSF_LOG) &&
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info->loglevel == NF_OSF_LOGLEVEL_FIRST)
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break;
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}
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if (!fcount && (info->flags & NF_OSF_LOG))
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nf_log_packet(net, family, hooknum, skb, in, out, NULL,
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"Remote OS is not known: %pI4:%u -> %pI4:%u\n",
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&ip->saddr, ntohs(tcp->source),
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&ip->daddr, ntohs(tcp->dest));
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if (fcount)
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fmatch = FMATCH_OK;
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return fmatch == FMATCH_OK;
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}
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EXPORT_SYMBOL_GPL(nf_osf_match);
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MODULE_LICENSE("GPL");
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