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09c434b8 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
bfb15f2a FFM |
2 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
3 | #include <linux/module.h> | |
4 | #include <linux/kernel.h> | |
5 | ||
6 | #include <linux/capability.h> | |
7 | #include <linux/if.h> | |
8 | #include <linux/inetdevice.h> | |
9 | #include <linux/ip.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> | |
15 | ||
16 | #include <net/ip.h> | |
17 | #include <net/tcp.h> | |
18 | ||
19 | #include <linux/netfilter/nfnetlink.h> | |
20 | #include <linux/netfilter/x_tables.h> | |
21 | #include <net/netfilter/nf_log.h> | |
ddba40be | 22 | #include <linux/netfilter/nfnetlink_osf.h> |
bfb15f2a | 23 | |
f9324952 FFM |
24 | /* |
25 | * Indexed by dont-fragment bit. | |
26 | * It is the only constant value in the fingerprint. | |
27 | */ | |
28 | struct list_head nf_osf_fingers[2]; | |
29 | EXPORT_SYMBOL_GPL(nf_osf_fingers); | |
30 | ||
bfb15f2a | 31 | static inline int nf_osf_ttl(const struct sk_buff *skb, |
06ff4aa2 | 32 | int ttl_check, unsigned char f_ttl) |
bfb15f2a | 33 | { |
a218dc82 | 34 | struct in_device *in_dev = __in_dev_get_rcu(skb->dev); |
bfb15f2a | 35 | const struct iphdr *ip = ip_hdr(skb); |
b8d19572 | 36 | const struct in_ifaddr *ifa; |
a218dc82 FFM |
37 | int ret = 0; |
38 | ||
39 | if (ttl_check == NF_OSF_TTL_TRUE) | |
40 | return ip->ttl == f_ttl; | |
41 | if (ttl_check == NF_OSF_TTL_NOCHECK) | |
42 | return 1; | |
43 | else if (ip->ttl <= f_ttl) | |
44 | return 1; | |
45 | ||
b8d19572 | 46 | in_dev_for_each_ifa_rcu(ifa, in_dev) { |
a218dc82 FFM |
47 | if (inet_ifa_match(ip->saddr, ifa)) { |
48 | ret = (ip->ttl == f_ttl); | |
49 | break; | |
bfb15f2a FFM |
50 | } |
51 | } | |
52 | ||
a218dc82 | 53 | return ret; |
bfb15f2a FFM |
54 | } |
55 | ||
31a9c292 PNA |
56 | struct nf_osf_hdr_ctx { |
57 | bool df; | |
58 | u16 window; | |
59 | u16 totlen; | |
60 | const unsigned char *optp; | |
61 | unsigned int optsize; | |
62 | }; | |
63 | ||
06ff4aa2 PNA |
64 | static bool nf_osf_match_one(const struct sk_buff *skb, |
65 | const struct nf_osf_user_finger *f, | |
31a9c292 PNA |
66 | int ttl_check, |
67 | struct nf_osf_hdr_ctx *ctx) | |
06ff4aa2 | 68 | { |
1a6a0951 | 69 | const __u8 *optpinit = ctx->optp; |
06ff4aa2 PNA |
70 | unsigned int check_WSS = 0; |
71 | int fmatch = FMATCH_WRONG; | |
72 | int foptsize, optnum; | |
73 | u16 mss = 0; | |
74 | ||
31a9c292 | 75 | if (ctx->totlen != f->ss || !nf_osf_ttl(skb, ttl_check, f->ttl)) |
06ff4aa2 PNA |
76 | return false; |
77 | ||
78 | /* | |
79 | * Should not happen if userspace parser was written correctly. | |
80 | */ | |
81 | if (f->wss.wc >= OSF_WSS_MAX) | |
82 | return false; | |
83 | ||
84 | /* Check options */ | |
85 | ||
86 | foptsize = 0; | |
87 | for (optnum = 0; optnum < f->opt_num; ++optnum) | |
88 | foptsize += f->opt[optnum].length; | |
89 | ||
90 | if (foptsize > MAX_IPOPTLEN || | |
31a9c292 PNA |
91 | ctx->optsize > MAX_IPOPTLEN || |
92 | ctx->optsize != foptsize) | |
06ff4aa2 PNA |
93 | return false; |
94 | ||
95 | check_WSS = f->wss.wc; | |
96 | ||
97 | for (optnum = 0; optnum < f->opt_num; ++optnum) { | |
31a9c292 | 98 | if (f->opt[optnum].kind == *ctx->optp) { |
06ff4aa2 | 99 | __u32 len = f->opt[optnum].length; |
31a9c292 | 100 | const __u8 *optend = ctx->optp + len; |
06ff4aa2 PNA |
101 | |
102 | fmatch = FMATCH_OK; | |
103 | ||
31a9c292 | 104 | switch (*ctx->optp) { |
06ff4aa2 | 105 | case OSFOPT_MSS: |
31a9c292 | 106 | mss = ctx->optp[3]; |
06ff4aa2 | 107 | mss <<= 8; |
31a9c292 | 108 | mss |= ctx->optp[2]; |
06ff4aa2 PNA |
109 | |
110 | mss = ntohs((__force __be16)mss); | |
111 | break; | |
112 | case OSFOPT_TS: | |
113 | break; | |
114 | } | |
115 | ||
31a9c292 | 116 | ctx->optp = optend; |
06ff4aa2 PNA |
117 | } else |
118 | fmatch = FMATCH_OPT_WRONG; | |
119 | ||
120 | if (fmatch != FMATCH_OK) | |
121 | break; | |
122 | } | |
123 | ||
124 | if (fmatch != FMATCH_OPT_WRONG) { | |
125 | fmatch = FMATCH_WRONG; | |
126 | ||
127 | switch (check_WSS) { | |
128 | case OSF_WSS_PLAIN: | |
31a9c292 | 129 | if (f->wss.val == 0 || ctx->window == f->wss.val) |
06ff4aa2 PNA |
130 | fmatch = FMATCH_OK; |
131 | break; | |
132 | case OSF_WSS_MSS: | |
133 | /* | |
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 | |
137 | * values. | |
138 | */ | |
139 | #define SMART_MSS_1 1460 | |
140 | #define SMART_MSS_2 1448 | |
31a9c292 PNA |
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) | |
06ff4aa2 PNA |
144 | fmatch = FMATCH_OK; |
145 | break; | |
146 | case OSF_WSS_MTU: | |
31a9c292 PNA |
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)) | |
06ff4aa2 PNA |
150 | fmatch = FMATCH_OK; |
151 | break; | |
152 | case OSF_WSS_MODULO: | |
31a9c292 | 153 | if ((ctx->window % f->wss.val) == 0) |
06ff4aa2 PNA |
154 | fmatch = FMATCH_OK; |
155 | break; | |
156 | } | |
157 | } | |
158 | ||
1a6a0951 FFM |
159 | if (fmatch != FMATCH_OK) |
160 | ctx->optp = optpinit; | |
161 | ||
06ff4aa2 PNA |
162 | return fmatch == FMATCH_OK; |
163 | } | |
164 | ||
31a9c292 PNA |
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, | |
168 | unsigned char *opts) | |
169 | { | |
170 | const struct tcphdr *tcp; | |
171 | struct tcphdr _tcph; | |
172 | ||
173 | tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph); | |
174 | if (!tcp) | |
175 | return NULL; | |
176 | ||
177 | if (!tcp->syn) | |
178 | return NULL; | |
179 | ||
180 | ctx->totlen = ntohs(ip->tot_len); | |
181 | ctx->df = ntohs(ip->frag_off) & IP_DF; | |
182 | ctx->window = ntohs(tcp->window); | |
183 | ||
184 | if (tcp->doff * 4 > sizeof(struct tcphdr)) { | |
185 | ctx->optsize = tcp->doff * 4 - sizeof(struct tcphdr); | |
186 | ||
187 | ctx->optp = skb_header_pointer(skb, ip_hdrlen(skb) + | |
188 | sizeof(struct tcphdr), ctx->optsize, opts); | |
189 | } | |
190 | ||
191 | return tcp; | |
192 | } | |
193 | ||
bfb15f2a FFM |
194 | bool |
195 | nf_osf_match(const struct sk_buff *skb, u_int8_t family, | |
196 | int hooknum, struct net_device *in, struct net_device *out, | |
197 | const struct nf_osf_info *info, struct net *net, | |
198 | const struct list_head *nf_osf_fingers) | |
199 | { | |
bfb15f2a FFM |
200 | const struct iphdr *ip = ip_hdr(skb); |
201 | const struct nf_osf_user_finger *f; | |
202 | unsigned char opts[MAX_IPOPTLEN]; | |
203 | const struct nf_osf_finger *kf; | |
06ff4aa2 PNA |
204 | int fcount = 0, ttl_check; |
205 | int fmatch = FMATCH_WRONG; | |
31a9c292 | 206 | struct nf_osf_hdr_ctx ctx; |
bfb15f2a | 207 | const struct tcphdr *tcp; |
bfb15f2a | 208 | |
31a9c292 | 209 | memset(&ctx, 0, sizeof(ctx)); |
bfb15f2a | 210 | |
31a9c292 PNA |
211 | tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts); |
212 | if (!tcp) | |
bfb15f2a FFM |
213 | return false; |
214 | ||
a218dc82 | 215 | ttl_check = (info->flags & NF_OSF_TTL) ? info->ttl : 0; |
06ff4aa2 | 216 | |
31a9c292 | 217 | list_for_each_entry_rcu(kf, &nf_osf_fingers[ctx.df], finger_entry) { |
bfb15f2a FFM |
218 | |
219 | f = &kf->finger; | |
220 | ||
221 | if (!(info->flags & NF_OSF_LOG) && strcmp(info->genre, f->genre)) | |
222 | continue; | |
223 | ||
31a9c292 | 224 | if (!nf_osf_match_one(skb, f, ttl_check, &ctx)) |
bfb15f2a FFM |
225 | continue; |
226 | ||
06ff4aa2 | 227 | fmatch = FMATCH_OK; |
bfb15f2a FFM |
228 | |
229 | fcount++; | |
230 | ||
231 | if (info->flags & NF_OSF_LOG) | |
232 | nf_log_packet(net, family, hooknum, skb, | |
233 | in, out, NULL, | |
234 | "%s [%s:%s] : %pI4:%d -> %pI4:%d hops=%d\n", | |
235 | f->genre, f->version, f->subtype, | |
236 | &ip->saddr, ntohs(tcp->source), | |
237 | &ip->daddr, ntohs(tcp->dest), | |
238 | f->ttl - ip->ttl); | |
239 | ||
240 | if ((info->flags & NF_OSF_LOG) && | |
241 | info->loglevel == NF_OSF_LOGLEVEL_FIRST) | |
242 | break; | |
243 | } | |
244 | ||
245 | if (!fcount && (info->flags & NF_OSF_LOG)) | |
246 | nf_log_packet(net, family, hooknum, skb, in, out, NULL, | |
247 | "Remote OS is not known: %pI4:%u -> %pI4:%u\n", | |
248 | &ip->saddr, ntohs(tcp->source), | |
249 | &ip->daddr, ntohs(tcp->dest)); | |
250 | ||
251 | if (fcount) | |
252 | fmatch = FMATCH_OK; | |
253 | ||
254 | return fmatch == FMATCH_OK; | |
255 | } | |
256 | EXPORT_SYMBOL_GPL(nf_osf_match); | |
257 | ||
22c7652c FFM |
258 | bool nf_osf_find(const struct sk_buff *skb, |
259 | const struct list_head *nf_osf_fingers, | |
260 | const int ttl_check, struct nf_osf_data *data) | |
51c23b47 PNA |
261 | { |
262 | const struct iphdr *ip = ip_hdr(skb); | |
263 | const struct nf_osf_user_finger *f; | |
264 | unsigned char opts[MAX_IPOPTLEN]; | |
265 | const struct nf_osf_finger *kf; | |
266 | struct nf_osf_hdr_ctx ctx; | |
267 | const struct tcphdr *tcp; | |
51c23b47 PNA |
268 | |
269 | memset(&ctx, 0, sizeof(ctx)); | |
270 | ||
271 | tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts); | |
272 | if (!tcp) | |
22c7652c | 273 | return false; |
51c23b47 PNA |
274 | |
275 | list_for_each_entry_rcu(kf, &nf_osf_fingers[ctx.df], finger_entry) { | |
276 | f = &kf->finger; | |
a218dc82 | 277 | if (!nf_osf_match_one(skb, f, ttl_check, &ctx)) |
51c23b47 PNA |
278 | continue; |
279 | ||
22c7652c FFM |
280 | data->genre = f->genre; |
281 | data->version = f->version; | |
51c23b47 PNA |
282 | break; |
283 | } | |
284 | ||
22c7652c | 285 | return true; |
51c23b47 PNA |
286 | } |
287 | EXPORT_SYMBOL_GPL(nf_osf_find); | |
288 | ||
f9324952 FFM |
289 | static const struct nla_policy nfnl_osf_policy[OSF_ATTR_MAX + 1] = { |
290 | [OSF_ATTR_FINGER] = { .len = sizeof(struct nf_osf_user_finger) }, | |
291 | }; | |
292 | ||
293 | static int nfnl_osf_add_callback(struct net *net, struct sock *ctnl, | |
294 | struct sk_buff *skb, const struct nlmsghdr *nlh, | |
295 | const struct nlattr * const osf_attrs[], | |
296 | struct netlink_ext_ack *extack) | |
297 | { | |
298 | struct nf_osf_user_finger *f; | |
299 | struct nf_osf_finger *kf = NULL, *sf; | |
300 | int err = 0; | |
301 | ||
302 | if (!capable(CAP_NET_ADMIN)) | |
303 | return -EPERM; | |
304 | ||
305 | if (!osf_attrs[OSF_ATTR_FINGER]) | |
306 | return -EINVAL; | |
307 | ||
308 | if (!(nlh->nlmsg_flags & NLM_F_CREATE)) | |
309 | return -EINVAL; | |
310 | ||
311 | f = nla_data(osf_attrs[OSF_ATTR_FINGER]); | |
312 | ||
313 | kf = kmalloc(sizeof(struct nf_osf_finger), GFP_KERNEL); | |
314 | if (!kf) | |
315 | return -ENOMEM; | |
316 | ||
317 | memcpy(&kf->finger, f, sizeof(struct nf_osf_user_finger)); | |
318 | ||
319 | list_for_each_entry(sf, &nf_osf_fingers[!!f->df], finger_entry) { | |
320 | if (memcmp(&sf->finger, f, sizeof(struct nf_osf_user_finger))) | |
321 | continue; | |
322 | ||
323 | kfree(kf); | |
324 | kf = NULL; | |
325 | ||
326 | if (nlh->nlmsg_flags & NLM_F_EXCL) | |
327 | err = -EEXIST; | |
328 | break; | |
329 | } | |
330 | ||
331 | /* | |
332 | * We are protected by nfnl mutex. | |
333 | */ | |
334 | if (kf) | |
335 | list_add_tail_rcu(&kf->finger_entry, &nf_osf_fingers[!!f->df]); | |
336 | ||
337 | return err; | |
338 | } | |
339 | ||
340 | static int nfnl_osf_remove_callback(struct net *net, struct sock *ctnl, | |
341 | struct sk_buff *skb, | |
342 | const struct nlmsghdr *nlh, | |
343 | const struct nlattr * const osf_attrs[], | |
344 | struct netlink_ext_ack *extack) | |
345 | { | |
346 | struct nf_osf_user_finger *f; | |
347 | struct nf_osf_finger *sf; | |
348 | int err = -ENOENT; | |
349 | ||
350 | if (!capable(CAP_NET_ADMIN)) | |
351 | return -EPERM; | |
352 | ||
353 | if (!osf_attrs[OSF_ATTR_FINGER]) | |
354 | return -EINVAL; | |
355 | ||
356 | f = nla_data(osf_attrs[OSF_ATTR_FINGER]); | |
357 | ||
358 | list_for_each_entry(sf, &nf_osf_fingers[!!f->df], finger_entry) { | |
359 | if (memcmp(&sf->finger, f, sizeof(struct nf_osf_user_finger))) | |
360 | continue; | |
361 | ||
362 | /* | |
363 | * We are protected by nfnl mutex. | |
364 | */ | |
365 | list_del_rcu(&sf->finger_entry); | |
366 | kfree_rcu(sf, rcu_head); | |
367 | ||
368 | err = 0; | |
369 | break; | |
370 | } | |
371 | ||
372 | return err; | |
373 | } | |
374 | ||
375 | static const struct nfnl_callback nfnl_osf_callbacks[OSF_MSG_MAX] = { | |
376 | [OSF_MSG_ADD] = { | |
377 | .call = nfnl_osf_add_callback, | |
378 | .attr_count = OSF_ATTR_MAX, | |
379 | .policy = nfnl_osf_policy, | |
380 | }, | |
381 | [OSF_MSG_REMOVE] = { | |
382 | .call = nfnl_osf_remove_callback, | |
383 | .attr_count = OSF_ATTR_MAX, | |
384 | .policy = nfnl_osf_policy, | |
385 | }, | |
386 | }; | |
387 | ||
388 | static const struct nfnetlink_subsystem nfnl_osf_subsys = { | |
389 | .name = "osf", | |
390 | .subsys_id = NFNL_SUBSYS_OSF, | |
391 | .cb_count = OSF_MSG_MAX, | |
392 | .cb = nfnl_osf_callbacks, | |
393 | }; | |
394 | ||
395 | static int __init nfnl_osf_init(void) | |
396 | { | |
397 | int err = -EINVAL; | |
398 | int i; | |
399 | ||
400 | for (i = 0; i < ARRAY_SIZE(nf_osf_fingers); ++i) | |
401 | INIT_LIST_HEAD(&nf_osf_fingers[i]); | |
402 | ||
403 | err = nfnetlink_subsys_register(&nfnl_osf_subsys); | |
404 | if (err < 0) { | |
405 | pr_err("Failed to register OSF nsfnetlink helper (%d)\n", err); | |
406 | goto err_out_exit; | |
407 | } | |
408 | return 0; | |
409 | ||
410 | err_out_exit: | |
411 | return err; | |
412 | } | |
413 | ||
414 | static void __exit nfnl_osf_fini(void) | |
415 | { | |
416 | struct nf_osf_finger *f; | |
417 | int i; | |
418 | ||
419 | nfnetlink_subsys_unregister(&nfnl_osf_subsys); | |
420 | ||
421 | rcu_read_lock(); | |
422 | for (i = 0; i < ARRAY_SIZE(nf_osf_fingers); ++i) { | |
423 | list_for_each_entry_rcu(f, &nf_osf_fingers[i], finger_entry) { | |
424 | list_del_rcu(&f->finger_entry); | |
425 | kfree_rcu(f, rcu_head); | |
426 | } | |
427 | } | |
428 | rcu_read_unlock(); | |
429 | ||
430 | rcu_barrier(); | |
431 | } | |
432 | ||
433 | module_init(nfnl_osf_init); | |
434 | module_exit(nfnl_osf_fini); | |
435 | ||
bfb15f2a | 436 | MODULE_LICENSE("GPL"); |