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
 48static char * __percpu *hmac_ring;
 49
 50static 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
 57static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
 58{
 59	kfree_rcu(hinfo, rcu);
 60}
 61
 62static 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
 70static 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
 78static 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
 89static 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
108static 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
123static 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
161failed:
162	return ret;
163}
164
165int 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) + flags(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. Flags (8 bits)
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	/* flags */
206	*off++ = hdr->flags;
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}
234EXPORT_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 */
241bool 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}
282EXPORT_SYMBOL(seg6_hmac_validate_skb);
283
284/* called with rcu_read_lock() */
285struct 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}
294EXPORT_SYMBOL(seg6_hmac_info_lookup);
295
296int 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}
306EXPORT_SYMBOL(seg6_hmac_info_add);
307
308int 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
325out:
326	return err;
327}
328EXPORT_SYMBOL(seg6_hmac_info_del);
329
330int 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
350out:
351	rcu_read_unlock();
352	return err;
353}
354EXPORT_SYMBOL(seg6_push_hmac);
355
356static 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
377static 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
423int __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
433out:
434	return ret;
435}
436EXPORT_SYMBOL(seg6_hmac_init);
437
438int __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}
446EXPORT_SYMBOL(seg6_hmac_net_init);
447
448void 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}
476EXPORT_SYMBOL(seg6_hmac_exit);
477
478void __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}
484EXPORT_SYMBOL(seg6_hmac_net_exit);