xref: /openbmc/linux/net/ipv6/seg6_hmac.c (revision fc28ab18) 
1 /*
2  *  SR-IPv6 implementation -- HMAC functions
3  *
4  *  Author:
5  *  David Lebrun <david.lebrun@uclouvain.be>
6  *
7  *
8  *  This program is free software; you can redistribute it and/or
9  *      modify it under the terms of the GNU General Public License
10  *      as published by the Free Software Foundation; either version
11  *      2 of the License, or (at your option) any later version.
12  */
13 
14 #include <linux/errno.h>
15 #include <linux/types.h>
16 #include <linux/socket.h>
17 #include <linux/sockios.h>
18 #include <linux/net.h>
19 #include <linux/netdevice.h>
20 #include <linux/in6.h>
21 #include <linux/icmpv6.h>
22 #include <linux/mroute6.h>
23 #include <linux/slab.h>
24 
25 #include <linux/netfilter.h>
26 #include <linux/netfilter_ipv6.h>
27 
28 #include <net/sock.h>
29 #include <net/snmp.h>
30 
31 #include <net/ipv6.h>
32 #include <net/protocol.h>
33 #include <net/transp_v6.h>
34 #include <net/rawv6.h>
35 #include <net/ndisc.h>
36 #include <net/ip6_route.h>
37 #include <net/addrconf.h>
38 #include <net/xfrm.h>
39 
40 #include <linux/cryptohash.h>
41 #include <crypto/hash.h>
42 #include <crypto/sha.h>
43 #include <net/seg6.h>
44 #include <net/genetlink.h>
45 #include <net/seg6_hmac.h>
46 #include <linux/random.h>
47 
48 static char * __percpu *hmac_ring;
49 
50 static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
51 {
52 	const struct seg6_hmac_info *hinfo = obj;
53 
54 	return (hinfo->hmackeyid != *(__u32 *)arg->key);
55 }
56 
57 static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
58 {
59 	kfree_rcu(hinfo, rcu);
60 }
61 
62 static void seg6_free_hi(void *ptr, void *arg)
63 {
64 	struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;
65 
66 	if (hinfo)
67 		seg6_hinfo_release(hinfo);
68 }
69 
70 static const struct rhashtable_params rht_params = {
71 	.head_offset		= offsetof(struct seg6_hmac_info, node),
72 	.key_offset		= offsetof(struct seg6_hmac_info, hmackeyid),
73 	.key_len		= sizeof(u32),
74 	.automatic_shrinking	= true,
75 	.obj_cmpfn		= seg6_hmac_cmpfn,
76 };
77 
78 static struct seg6_hmac_algo hmac_algos[] = {
79 	{
80 		.alg_id = SEG6_HMAC_ALGO_SHA1,
81 		.name = "hmac(sha1)",
82 	},
83 	{
84 		.alg_id = SEG6_HMAC_ALGO_SHA256,
85 		.name = "hmac(sha256)",
86 	},
87 };
88 
89 static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
90 {
91 	struct sr6_tlv_hmac *tlv;
92 
93 	if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
94 		return NULL;
95 
96 	if (!sr_has_hmac(srh))
97 		return NULL;
98 
99 	tlv = (struct sr6_tlv_hmac *)
100 	      ((char *)srh + ((srh->hdrlen + 1) << 3) - 40);
101 
102 	if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
103 		return NULL;
104 
105 	return tlv;
106 }
107 
108 static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id)
109 {
110 	struct seg6_hmac_algo *algo;
111 	int i, alg_count;
112 
113 	alg_count = sizeof(hmac_algos) / sizeof(struct seg6_hmac_algo);
114 	for (i = 0; i < alg_count; i++) {
115 		algo = &hmac_algos[i];
116 		if (algo->alg_id == alg_id)
117 			return algo;
118 	}
119 
120 	return NULL;
121 }
122 
123 static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize,
124 		     u8 *output, int outlen)
125 {
126 	struct seg6_hmac_algo *algo;
127 	struct crypto_shash *tfm;
128 	struct shash_desc *shash;
129 	int ret, dgsize;
130 
131 	algo = __hmac_get_algo(hinfo->alg_id);
132 	if (!algo)
133 		return -ENOENT;
134 
135 	tfm = *this_cpu_ptr(algo->tfms);
136 
137 	dgsize = crypto_shash_digestsize(tfm);
138 	if (dgsize > outlen) {
139 		pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n",
140 			 dgsize, outlen);
141 		return -ENOMEM;
142 	}
143 
144 	ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen);
145 	if (ret < 0) {
146 		pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret);
147 		goto failed;
148 	}
149 
150 	shash = *this_cpu_ptr(algo->shashs);
151 	shash->tfm = tfm;
152 
153 	ret = crypto_shash_digest(shash, text, psize, output);
154 	if (ret < 0) {
155 		pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret);
156 		goto failed;
157 	}
158 
159 	return dgsize;
160 
161 failed:
162 	return ret;
163 }
164 
165 int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
166 		      struct in6_addr *saddr, u8 *output)
167 {
168 	__be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
169 	u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE];
170 	int plen, i, dgsize, wrsize;
171 	char *ring, *off;
172 
173 	/* a 160-byte buffer for digest output allows to store highest known
174 	 * hash function (RadioGatun) with up to 1216 bits
175 	 */
176 
177 	/* saddr(16) + first_seg(1) + cleanup(1) + keyid(4) + seglist(16n) */
178 	plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;
179 
180 	/* this limit allows for 14 segments */
181 	if (plen >= SEG6_HMAC_RING_SIZE)
182 		return -EMSGSIZE;
183 
184 	/* Let's build the HMAC text on the ring buffer. The text is composed
185 	 * as follows, in order:
186 	 *
187 	 * 1. Source IPv6 address (128 bits)
188 	 * 2. first_segment value (8 bits)
189 	 * 3. cleanup flag (8 bits: highest bit is cleanup value, others are 0)
190 	 * 4. HMAC Key ID (32 bits)
191 	 * 5. All segments in the segments list (n * 128 bits)
192 	 */
193 
194 	local_bh_disable();
195 	ring = *this_cpu_ptr(hmac_ring);
196 	off = ring;
197 
198 	/* source address */
199 	memcpy(off, saddr, 16);
200 	off += 16;
201 
202 	/* first_segment value */
203 	*off++ = hdr->first_segment;
204 
205 	/* cleanup flag */
206 	*off++ = !!(sr_has_cleanup(hdr)) << 7;
207 
208 	/* HMAC Key ID */
209 	memcpy(off, &hmackeyid, 4);
210 	off += 4;
211 
212 	/* all segments in the list */
213 	for (i = 0; i < hdr->first_segment + 1; i++) {
214 		memcpy(off, hdr->segments + i, 16);
215 		off += 16;
216 	}
217 
218 	dgsize = __do_hmac(hinfo, ring, plen, tmp_out,
219 			   SEG6_HMAC_MAX_DIGESTSIZE);
220 	local_bh_enable();
221 
222 	if (dgsize < 0)
223 		return dgsize;
224 
225 	wrsize = SEG6_HMAC_FIELD_LEN;
226 	if (wrsize > dgsize)
227 		wrsize = dgsize;
228 
229 	memset(output, 0, SEG6_HMAC_FIELD_LEN);
230 	memcpy(output, tmp_out, wrsize);
231 
232 	return 0;
233 }
234 EXPORT_SYMBOL(seg6_hmac_compute);
235 
236 /* checks if an incoming SR-enabled packet's HMAC status matches
237  * the incoming policy.
238  *
239  * called with rcu_read_lock()
240  */
241 bool seg6_hmac_validate_skb(struct sk_buff *skb)
242 {
243 	u8 hmac_output[SEG6_HMAC_FIELD_LEN];
244 	struct net *net = dev_net(skb->dev);
245 	struct seg6_hmac_info *hinfo;
246 	struct sr6_tlv_hmac *tlv;
247 	struct ipv6_sr_hdr *srh;
248 	struct inet6_dev *idev;
249 
250 	idev = __in6_dev_get(skb->dev);
251 
252 	srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
253 
254 	tlv = seg6_get_tlv_hmac(srh);
255 
256 	/* mandatory check but no tlv */
257 	if (idev->cnf.seg6_require_hmac > 0 && !tlv)
258 		return false;
259 
260 	/* no check */
261 	if (idev->cnf.seg6_require_hmac < 0)
262 		return true;
263 
264 	/* check only if present */
265 	if (idev->cnf.seg6_require_hmac == 0 && !tlv)
266 		return true;
267 
268 	/* now, seg6_require_hmac >= 0 && tlv */
269 
270 	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
271 	if (!hinfo)
272 		return false;
273 
274 	if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
275 		return false;
276 
277 	if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
278 		return false;
279 
280 	return true;
281 }
282 EXPORT_SYMBOL(seg6_hmac_validate_skb);
283 
284 /* called with rcu_read_lock() */
285 struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
286 {
287 	struct seg6_pernet_data *sdata = seg6_pernet(net);
288 	struct seg6_hmac_info *hinfo;
289 
290 	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
291 
292 	return hinfo;
293 }
294 EXPORT_SYMBOL(seg6_hmac_info_lookup);
295 
296 int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
297 {
298 	struct seg6_pernet_data *sdata = seg6_pernet(net);
299 	int err;
300 
301 	err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
302 					    rht_params);
303 
304 	return err;
305 }
306 EXPORT_SYMBOL(seg6_hmac_info_add);
307 
308 int seg6_hmac_info_del(struct net *net, u32 key)
309 {
310 	struct seg6_pernet_data *sdata = seg6_pernet(net);
311 	struct seg6_hmac_info *hinfo;
312 	int err = -ENOENT;
313 
314 	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
315 	if (!hinfo)
316 		goto out;
317 
318 	err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
319 				     rht_params);
320 	if (err)
321 		goto out;
322 
323 	seg6_hinfo_release(hinfo);
324 
325 out:
326 	return err;
327 }
328 EXPORT_SYMBOL(seg6_hmac_info_del);
329 
330 int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
331 		   struct ipv6_sr_hdr *srh)
332 {
333 	struct seg6_hmac_info *hinfo;
334 	struct sr6_tlv_hmac *tlv;
335 	int err = -ENOENT;
336 
337 	tlv = seg6_get_tlv_hmac(srh);
338 	if (!tlv)
339 		return -EINVAL;
340 
341 	rcu_read_lock();
342 
343 	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
344 	if (!hinfo)
345 		goto out;
346 
347 	memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
348 	err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
349 
350 out:
351 	rcu_read_unlock();
352 	return err;
353 }
354 EXPORT_SYMBOL(seg6_push_hmac);
355 
356 static int seg6_hmac_init_ring(void)
357 {
358 	int i;
359 
360 	hmac_ring = alloc_percpu(char *);
361 
362 	if (!hmac_ring)
363 		return -ENOMEM;
364 
365 	for_each_possible_cpu(i) {
366 		char *ring = kzalloc(SEG6_HMAC_RING_SIZE, GFP_KERNEL);
367 
368 		if (!ring)
369 			return -ENOMEM;
370 
371 		*per_cpu_ptr(hmac_ring, i) = ring;
372 	}
373 
374 	return 0;
375 }
376 
377 static int seg6_hmac_init_algo(void)
378 {
379 	struct seg6_hmac_algo *algo;
380 	struct crypto_shash *tfm;
381 	struct shash_desc *shash;
382 	int i, alg_count, cpu;
383 
384 	alg_count = sizeof(hmac_algos) / sizeof(struct seg6_hmac_algo);
385 
386 	for (i = 0; i < alg_count; i++) {
387 		struct crypto_shash **p_tfm;
388 		int shsize;
389 
390 		algo = &hmac_algos[i];
391 		algo->tfms = alloc_percpu(struct crypto_shash *);
392 		if (!algo->tfms)
393 			return -ENOMEM;
394 
395 		for_each_possible_cpu(cpu) {
396 			tfm = crypto_alloc_shash(algo->name, 0, GFP_KERNEL);
397 			if (IS_ERR(tfm))
398 				return PTR_ERR(tfm);
399 			p_tfm = per_cpu_ptr(algo->tfms, cpu);
400 			*p_tfm = tfm;
401 		}
402 
403 		p_tfm = raw_cpu_ptr(algo->tfms);
404 		tfm = *p_tfm;
405 
406 		shsize = sizeof(*shash) + crypto_shash_descsize(tfm);
407 
408 		algo->shashs = alloc_percpu(struct shash_desc *);
409 		if (!algo->shashs)
410 			return -ENOMEM;
411 
412 		for_each_possible_cpu(cpu) {
413 			shash = kzalloc(shsize, GFP_KERNEL);
414 			if (!shash)
415 				return -ENOMEM;
416 			*per_cpu_ptr(algo->shashs, cpu) = shash;
417 		}
418 	}
419 
420 	return 0;
421 }
422 
423 int __init seg6_hmac_init(void)
424 {
425 	int ret;
426 
427 	ret = seg6_hmac_init_ring();
428 	if (ret < 0)
429 		goto out;
430 
431 	ret = seg6_hmac_init_algo();
432 
433 out:
434 	return ret;
435 }
436 EXPORT_SYMBOL(seg6_hmac_init);
437 
438 int __net_init seg6_hmac_net_init(struct net *net)
439 {
440 	struct seg6_pernet_data *sdata = seg6_pernet(net);
441 
442 	rhashtable_init(&sdata->hmac_infos, &rht_params);
443 
444 	return 0;
445 }
446 EXPORT_SYMBOL(seg6_hmac_net_init);
447 
448 void seg6_hmac_exit(void)
449 {
450 	struct seg6_hmac_algo *algo = NULL;
451 	int i, alg_count, cpu;
452 
453 	for_each_possible_cpu(i) {
454 		char *ring = *per_cpu_ptr(hmac_ring, i);
455 
456 		kfree(ring);
457 	}
458 	free_percpu(hmac_ring);
459 
460 	alg_count = sizeof(hmac_algos) / sizeof(struct seg6_hmac_algo);
461 	for (i = 0; i < alg_count; i++) {
462 		algo = &hmac_algos[i];
463 		for_each_possible_cpu(cpu) {
464 			struct crypto_shash *tfm;
465 			struct shash_desc *shash;
466 
467 			shash = *per_cpu_ptr(algo->shashs, cpu);
468 			kfree(shash);
469 			tfm = *per_cpu_ptr(algo->tfms, cpu);
470 			crypto_free_shash(tfm);
471 		}
472 		free_percpu(algo->tfms);
473 		free_percpu(algo->shashs);
474 	}
475 }
476 EXPORT_SYMBOL(seg6_hmac_exit);
477 
478 void __net_exit seg6_hmac_net_exit(struct net *net)
479 {
480 	struct seg6_pernet_data *sdata = seg6_pernet(net);
481 
482 	rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
483 }
484 EXPORT_SYMBOL(seg6_hmac_net_exit);
485