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