1 // SPDX-License-Identifier: GPL-2.0-only
2 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
3 #include <linux/module.h>
4 #include <linux/kernel.h>
6 #include <linux/capability.h>
8 #include <linux/inetdevice.h>
10 #include <linux/list.h>
11 #include <linux/rculist.h>
12 #include <linux/skbuff.h>
13 #include <linux/slab.h>
14 #include <linux/tcp.h>
19 #include <linux/netfilter/nfnetlink.h>
20 #include <linux/netfilter/x_tables.h>
21 #include <net/netfilter/nf_log.h>
22 #include <linux/netfilter/nfnetlink_osf.h>
25 * Indexed by dont-fragment bit.
26 * It is the only constant value in the fingerprint.
28 struct list_head nf_osf_fingers[2];
29 EXPORT_SYMBOL_GPL(nf_osf_fingers);
31 static inline int nf_osf_ttl(const struct sk_buff *skb,
32 int ttl_check, unsigned char f_ttl)
34 struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
35 const struct iphdr *ip = ip_hdr(skb);
36 const struct in_ifaddr *ifa;
39 if (ttl_check == NF_OSF_TTL_TRUE)
40 return ip->ttl == f_ttl;
41 if (ttl_check == NF_OSF_TTL_NOCHECK)
43 else if (ip->ttl <= f_ttl)
46 in_dev_for_each_ifa_rcu(ifa, in_dev) {
47 if (inet_ifa_match(ip->saddr, ifa)) {
48 ret = (ip->ttl == f_ttl);
56 struct nf_osf_hdr_ctx {
60 const unsigned char *optp;
64 static bool nf_osf_match_one(const struct sk_buff *skb,
65 const struct nf_osf_user_finger *f,
67 struct nf_osf_hdr_ctx *ctx)
69 const __u8 *optpinit = ctx->optp;
70 unsigned int check_WSS = 0;
71 int fmatch = FMATCH_WRONG;
75 if (ctx->totlen != f->ss || !nf_osf_ttl(skb, ttl_check, f->ttl))
79 * Should not happen if userspace parser was written correctly.
81 if (f->wss.wc >= OSF_WSS_MAX)
87 for (optnum = 0; optnum < f->opt_num; ++optnum)
88 foptsize += f->opt[optnum].length;
90 if (foptsize > MAX_IPOPTLEN ||
91 ctx->optsize > MAX_IPOPTLEN ||
92 ctx->optsize != foptsize)
95 check_WSS = f->wss.wc;
97 for (optnum = 0; optnum < f->opt_num; ++optnum) {
98 if (f->opt[optnum].kind == *ctx->optp) {
99 __u32 len = f->opt[optnum].length;
100 const __u8 *optend = ctx->optp + len;
104 switch (*ctx->optp) {
110 mss = ntohs((__force __be16)mss);
118 fmatch = FMATCH_OPT_WRONG;
120 if (fmatch != FMATCH_OK)
124 if (fmatch != FMATCH_OPT_WRONG) {
125 fmatch = FMATCH_WRONG;
129 if (f->wss.val == 0 || ctx->window == f->wss.val)
134 * Some smart modems decrease mangle MSS to
135 * SMART_MSS_2, so we check standard, decreased
136 * and the one provided in the fingerprint MSS
139 #define SMART_MSS_1 1460
140 #define SMART_MSS_2 1448
141 if (ctx->window == f->wss.val * mss ||
142 ctx->window == f->wss.val * SMART_MSS_1 ||
143 ctx->window == f->wss.val * SMART_MSS_2)
147 if (ctx->window == f->wss.val * (mss + 40) ||
148 ctx->window == f->wss.val * (SMART_MSS_1 + 40) ||
149 ctx->window == f->wss.val * (SMART_MSS_2 + 40))
153 if ((ctx->window % f->wss.val) == 0)
159 if (fmatch != FMATCH_OK)
160 ctx->optp = optpinit;
162 return fmatch == FMATCH_OK;
165 static const struct tcphdr *nf_osf_hdr_ctx_init(struct nf_osf_hdr_ctx *ctx,
166 const struct sk_buff *skb,
167 const struct iphdr *ip,
169 struct tcphdr *_tcph)
171 const struct tcphdr *tcp;
173 tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), _tcph);
180 ctx->totlen = ntohs(ip->tot_len);
181 ctx->df = ntohs(ip->frag_off) & IP_DF;
182 ctx->window = ntohs(tcp->window);
184 if (tcp->doff * 4 > sizeof(struct tcphdr)) {
185 ctx->optsize = tcp->doff * 4 - sizeof(struct tcphdr);
187 ctx->optp = skb_header_pointer(skb, ip_hdrlen(skb) +
188 sizeof(struct tcphdr), ctx->optsize, opts);
197 nf_osf_match(const struct sk_buff *skb, u_int8_t family,
198 int hooknum, struct net_device *in, struct net_device *out,
199 const struct nf_osf_info *info, struct net *net,
200 const struct list_head *nf_osf_fingers)
202 const struct iphdr *ip = ip_hdr(skb);
203 const struct nf_osf_user_finger *f;
204 unsigned char opts[MAX_IPOPTLEN];
205 const struct nf_osf_finger *kf;
206 int fcount = 0, ttl_check;
207 int fmatch = FMATCH_WRONG;
208 struct nf_osf_hdr_ctx ctx;
209 const struct tcphdr *tcp;
212 memset(&ctx, 0, sizeof(ctx));
214 tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts, &_tcph);
218 ttl_check = (info->flags & NF_OSF_TTL) ? info->ttl : 0;
220 list_for_each_entry_rcu(kf, &nf_osf_fingers[ctx.df], finger_entry) {
224 if (!(info->flags & NF_OSF_LOG) && strcmp(info->genre, f->genre))
227 if (!nf_osf_match_one(skb, f, ttl_check, &ctx))
234 if (info->flags & NF_OSF_LOG)
235 nf_log_packet(net, family, hooknum, skb,
237 "%s [%s:%s] : %pI4:%d -> %pI4:%d hops=%d\n",
238 f->genre, f->version, f->subtype,
239 &ip->saddr, ntohs(tcp->source),
240 &ip->daddr, ntohs(tcp->dest),
243 if ((info->flags & NF_OSF_LOG) &&
244 info->loglevel == NF_OSF_LOGLEVEL_FIRST)
248 if (!fcount && (info->flags & NF_OSF_LOG))
249 nf_log_packet(net, family, hooknum, skb, in, out, NULL,
250 "Remote OS is not known: %pI4:%u -> %pI4:%u\n",
251 &ip->saddr, ntohs(tcp->source),
252 &ip->daddr, ntohs(tcp->dest));
257 return fmatch == FMATCH_OK;
259 EXPORT_SYMBOL_GPL(nf_osf_match);
261 bool nf_osf_find(const struct sk_buff *skb,
262 const struct list_head *nf_osf_fingers,
263 const int ttl_check, struct nf_osf_data *data)
265 const struct iphdr *ip = ip_hdr(skb);
266 const struct nf_osf_user_finger *f;
267 unsigned char opts[MAX_IPOPTLEN];
268 const struct nf_osf_finger *kf;
269 struct nf_osf_hdr_ctx ctx;
270 const struct tcphdr *tcp;
273 memset(&ctx, 0, sizeof(ctx));
275 tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts, &_tcph);
279 list_for_each_entry_rcu(kf, &nf_osf_fingers[ctx.df], finger_entry) {
281 if (!nf_osf_match_one(skb, f, ttl_check, &ctx))
284 data->genre = f->genre;
285 data->version = f->version;
291 EXPORT_SYMBOL_GPL(nf_osf_find);
293 static const struct nla_policy nfnl_osf_policy[OSF_ATTR_MAX + 1] = {
294 [OSF_ATTR_FINGER] = { .len = sizeof(struct nf_osf_user_finger) },
297 static int nfnl_osf_add_callback(struct sk_buff *skb,
298 const struct nfnl_info *info,
299 const struct nlattr * const osf_attrs[])
301 struct nf_osf_user_finger *f;
302 struct nf_osf_finger *kf = NULL, *sf;
305 if (!capable(CAP_NET_ADMIN))
308 if (!osf_attrs[OSF_ATTR_FINGER])
311 if (!(info->nlh->nlmsg_flags & NLM_F_CREATE))
314 f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
316 kf = kmalloc(sizeof(struct nf_osf_finger), GFP_KERNEL);
320 memcpy(&kf->finger, f, sizeof(struct nf_osf_user_finger));
322 list_for_each_entry(sf, &nf_osf_fingers[!!f->df], finger_entry) {
323 if (memcmp(&sf->finger, f, sizeof(struct nf_osf_user_finger)))
329 if (info->nlh->nlmsg_flags & NLM_F_EXCL)
335 * We are protected by nfnl mutex.
338 list_add_tail_rcu(&kf->finger_entry, &nf_osf_fingers[!!f->df]);
343 static int nfnl_osf_remove_callback(struct sk_buff *skb,
344 const struct nfnl_info *info,
345 const struct nlattr * const osf_attrs[])
347 struct nf_osf_user_finger *f;
348 struct nf_osf_finger *sf;
351 if (!capable(CAP_NET_ADMIN))
354 if (!osf_attrs[OSF_ATTR_FINGER])
357 f = nla_data(osf_attrs[OSF_ATTR_FINGER]);
359 list_for_each_entry(sf, &nf_osf_fingers[!!f->df], finger_entry) {
360 if (memcmp(&sf->finger, f, sizeof(struct nf_osf_user_finger)))
364 * We are protected by nfnl mutex.
366 list_del_rcu(&sf->finger_entry);
367 kfree_rcu(sf, rcu_head);
376 static const struct nfnl_callback nfnl_osf_callbacks[OSF_MSG_MAX] = {
378 .call = nfnl_osf_add_callback,
379 .type = NFNL_CB_MUTEX,
380 .attr_count = OSF_ATTR_MAX,
381 .policy = nfnl_osf_policy,
384 .call = nfnl_osf_remove_callback,
385 .type = NFNL_CB_MUTEX,
386 .attr_count = OSF_ATTR_MAX,
387 .policy = nfnl_osf_policy,
391 static const struct nfnetlink_subsystem nfnl_osf_subsys = {
393 .subsys_id = NFNL_SUBSYS_OSF,
394 .cb_count = OSF_MSG_MAX,
395 .cb = nfnl_osf_callbacks,
398 static int __init nfnl_osf_init(void)
403 for (i = 0; i < ARRAY_SIZE(nf_osf_fingers); ++i)
404 INIT_LIST_HEAD(&nf_osf_fingers[i]);
406 err = nfnetlink_subsys_register(&nfnl_osf_subsys);
408 pr_err("Failed to register OSF nsfnetlink helper (%d)\n", err);
417 static void __exit nfnl_osf_fini(void)
419 struct nf_osf_finger *f;
422 nfnetlink_subsys_unregister(&nfnl_osf_subsys);
425 for (i = 0; i < ARRAY_SIZE(nf_osf_fingers); ++i) {
426 list_for_each_entry_rcu(f, &nf_osf_fingers[i], finger_entry) {
427 list_del_rcu(&f->finger_entry);
428 kfree_rcu(f, rcu_head);
436 module_init(nfnl_osf_init);
437 module_exit(nfnl_osf_fini);
439 MODULE_LICENSE("GPL");