1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 *  SR-IPv6 implementation -- HMAC functions
  4 *
  5 *  Author:
  6 *  David Lebrun <david.lebrun@uclouvain.be>
  7 */
  8
  9#include <linux/errno.h>
 10#include <linux/kernel.h>
 11#include <linux/types.h>
 12#include <linux/socket.h>
 13#include <linux/sockios.h>
 14#include <linux/net.h>
 15#include <linux/netdevice.h>
 16#include <linux/in6.h>
 17#include <linux/icmpv6.h>
 18#include <linux/mroute6.h>
 19#include <linux/slab.h>
 20#include <linux/rhashtable.h>
 21
 22#include <linux/netfilter.h>
 23#include <linux/netfilter_ipv6.h>
 24
 25#include <net/sock.h>
 26#include <net/snmp.h>
 27
 28#include <net/ipv6.h>
 29#include <net/protocol.h>
 30#include <net/transp_v6.h>
 31#include <net/rawv6.h>
 32#include <net/ndisc.h>
 33#include <net/ip6_route.h>
 34#include <net/addrconf.h>
 35#include <net/xfrm.h>
 36
 37#include <crypto/hash.h>
 38#include <net/seg6.h>
 39#include <net/genetlink.h>
 40#include <net/seg6_hmac.h>
 41#include <linux/random.h>
 42
 43static DEFINE_PER_CPU(char [SEG6_HMAC_RING_SIZE], hmac_ring);
 44
 45static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
 46{
 47	const struct seg6_hmac_info *hinfo = obj;
 48
 49	return (hinfo->hmackeyid != *(__u32 *)arg->key);
 50}
 51
 52static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
 53{
 54	kfree_rcu(hinfo, rcu);
 55}
 56
 57static void seg6_free_hi(void *ptr, void *arg)
 58{
 59	struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;
 60
 61	if (hinfo)
 62		seg6_hinfo_release(hinfo);
 63}
 64
 65static const struct rhashtable_params rht_params = {
 66	.head_offset		= offsetof(struct seg6_hmac_info, node),
 67	.key_offset		= offsetof(struct seg6_hmac_info, hmackeyid),
 68	.key_len		= sizeof(u32),
 69	.automatic_shrinking	= true,
 70	.obj_cmpfn		= seg6_hmac_cmpfn,
 71};
 72
 73static struct seg6_hmac_algo hmac_algos[] = {
 74	{
 75		.alg_id = SEG6_HMAC_ALGO_SHA1,
 76		.name = "hmac(sha1)",
 77	},
 78	{
 79		.alg_id = SEG6_HMAC_ALGO_SHA256,
 80		.name = "hmac(sha256)",
 81	},
 82};
 83
 84static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
 85{
 86	struct sr6_tlv_hmac *tlv;
 87
 88	if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
 89		return NULL;
 90
 91	if (!sr_has_hmac(srh))
 92		return NULL;
 93
 94	tlv = (struct sr6_tlv_hmac *)
 95	      ((char *)srh + ((srh->hdrlen + 1) << 3) - 40);
 96
 97	if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
 98		return NULL;
 99
100	return tlv;
101}
102
103static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id)
104{
105	struct seg6_hmac_algo *algo;
106	int i, alg_count;
107
108	alg_count = ARRAY_SIZE(hmac_algos);
109	for (i = 0; i < alg_count; i++) {
110		algo = &hmac_algos[i];
111		if (algo->alg_id == alg_id)
112			return algo;
113	}
114
115	return NULL;
116}
117
118static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize,
119		     u8 *output, int outlen)
120{
121	struct seg6_hmac_algo *algo;
122	struct crypto_shash *tfm;
123	struct shash_desc *shash;
124	int ret, dgsize;
125
126	algo = __hmac_get_algo(hinfo->alg_id);
127	if (!algo)
128		return -ENOENT;
129
130	tfm = *this_cpu_ptr(algo->tfms);
131
132	dgsize = crypto_shash_digestsize(tfm);
133	if (dgsize > outlen) {
134		pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n",
135			 dgsize, outlen);
136		return -ENOMEM;
137	}
138
139	ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen);
140	if (ret < 0) {
141		pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret);
142		goto failed;
143	}
144
145	shash = *this_cpu_ptr(algo->shashs);
146	shash->tfm = tfm;
147
148	ret = crypto_shash_digest(shash, text, psize, output);
149	if (ret < 0) {
150		pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret);
151		goto failed;
152	}
153
154	return dgsize;
155
156failed:
157	return ret;
158}
159
160int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
161		      struct in6_addr *saddr, u8 *output)
162{
163	__be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
164	u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE];
165	int plen, i, dgsize, wrsize;
166	char *ring, *off;
167
168	/* a 160-byte buffer for digest output allows to store highest known
169	 * hash function (RadioGatun) with up to 1216 bits
170	 */
171
172	/* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */
173	plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;
174
175	/* this limit allows for 14 segments */
176	if (plen >= SEG6_HMAC_RING_SIZE)
177		return -EMSGSIZE;
178
179	/* Let's build the HMAC text on the ring buffer. The text is composed
180	 * as follows, in order:
181	 *
182	 * 1. Source IPv6 address (128 bits)
183	 * 2. first_segment value (8 bits)
184	 * 3. Flags (8 bits)
185	 * 4. HMAC Key ID (32 bits)
186	 * 5. All segments in the segments list (n * 128 bits)
187	 */
188
189	local_bh_disable();
190	ring = this_cpu_ptr(hmac_ring);
191	off = ring;
192
193	/* source address */
194	memcpy(off, saddr, 16);
195	off += 16;
196
197	/* first_segment value */
198	*off++ = hdr->first_segment;
199
200	/* flags */
201	*off++ = hdr->flags;
202
203	/* HMAC Key ID */
204	memcpy(off, &hmackeyid, 4);
205	off += 4;
206
207	/* all segments in the list */
208	for (i = 0; i < hdr->first_segment + 1; i++) {
209		memcpy(off, hdr->segments + i, 16);
210		off += 16;
211	}
212
213	dgsize = __do_hmac(hinfo, ring, plen, tmp_out,
214			   SEG6_HMAC_MAX_DIGESTSIZE);
215	local_bh_enable();
216
217	if (dgsize < 0)
218		return dgsize;
219
220	wrsize = SEG6_HMAC_FIELD_LEN;
221	if (wrsize > dgsize)
222		wrsize = dgsize;
223
224	memset(output, 0, SEG6_HMAC_FIELD_LEN);
225	memcpy(output, tmp_out, wrsize);
226
227	return 0;
228}
229EXPORT_SYMBOL(seg6_hmac_compute);
230
231/* checks if an incoming SR-enabled packet's HMAC status matches
232 * the incoming policy.
233 *
234 * called with rcu_read_lock()
235 */
236bool seg6_hmac_validate_skb(struct sk_buff *skb)
237{
238	u8 hmac_output[SEG6_HMAC_FIELD_LEN];
239	struct net *net = dev_net(skb->dev);
240	struct seg6_hmac_info *hinfo;
241	struct sr6_tlv_hmac *tlv;
242	struct ipv6_sr_hdr *srh;
243	struct inet6_dev *idev;
244
245	idev = __in6_dev_get(skb->dev);
246
247	srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
248
249	tlv = seg6_get_tlv_hmac(srh);
250
251	/* mandatory check but no tlv */
252	if (idev->cnf.seg6_require_hmac > 0 && !tlv)
253		return false;
254
255	/* no check */
256	if (idev->cnf.seg6_require_hmac < 0)
257		return true;
258
259	/* check only if present */
260	if (idev->cnf.seg6_require_hmac == 0 && !tlv)
261		return true;
262
263	/* now, seg6_require_hmac >= 0 && tlv */
264
265	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
266	if (!hinfo)
267		return false;
268
269	if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
270		return false;
271
272	if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
273		return false;
274
275	return true;
276}
277EXPORT_SYMBOL(seg6_hmac_validate_skb);
278
279/* called with rcu_read_lock() */
280struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
281{
282	struct seg6_pernet_data *sdata = seg6_pernet(net);
283	struct seg6_hmac_info *hinfo;
284
285	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
286
287	return hinfo;
288}
289EXPORT_SYMBOL(seg6_hmac_info_lookup);
290
291int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
292{
293	struct seg6_pernet_data *sdata = seg6_pernet(net);
294	int err;
295
296	err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
297					    rht_params);
298
299	return err;
300}
301EXPORT_SYMBOL(seg6_hmac_info_add);
302
303int seg6_hmac_info_del(struct net *net, u32 key)
304{
305	struct seg6_pernet_data *sdata = seg6_pernet(net);
306	struct seg6_hmac_info *hinfo;
307	int err = -ENOENT;
308
309	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
310	if (!hinfo)
311		goto out;
312
313	err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
314				     rht_params);
315	if (err)
316		goto out;
317
318	seg6_hinfo_release(hinfo);
319
320out:
321	return err;
322}
323EXPORT_SYMBOL(seg6_hmac_info_del);
324
325int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
326		   struct ipv6_sr_hdr *srh)
327{
328	struct seg6_hmac_info *hinfo;
329	struct sr6_tlv_hmac *tlv;
330	int err = -ENOENT;
331
332	tlv = seg6_get_tlv_hmac(srh);
333	if (!tlv)
334		return -EINVAL;
335
336	rcu_read_lock();
337
338	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
339	if (!hinfo)
340		goto out;
341
342	memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
343	err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
344
345out:
346	rcu_read_unlock();
347	return err;
348}
349EXPORT_SYMBOL(seg6_push_hmac);
350
351static int seg6_hmac_init_algo(void)
352{
353	struct seg6_hmac_algo *algo;
354	struct crypto_shash *tfm;
355	struct shash_desc *shash;
356	int i, alg_count, cpu;
357
358	alg_count = ARRAY_SIZE(hmac_algos);
359
360	for (i = 0; i < alg_count; i++) {
361		struct crypto_shash **p_tfm;
362		int shsize;
363
364		algo = &hmac_algos[i];
365		algo->tfms = alloc_percpu(struct crypto_shash *);
366		if (!algo->tfms)
367			return -ENOMEM;
368
369		for_each_possible_cpu(cpu) {
370			tfm = crypto_alloc_shash(algo->name, 0, 0);
371			if (IS_ERR(tfm))
372				return PTR_ERR(tfm);
373			p_tfm = per_cpu_ptr(algo->tfms, cpu);
374			*p_tfm = tfm;
375		}
376
377		p_tfm = raw_cpu_ptr(algo->tfms);
378		tfm = *p_tfm;
379
380		shsize = sizeof(*shash) + crypto_shash_descsize(tfm);
381
382		algo->shashs = alloc_percpu(struct shash_desc *);
383		if (!algo->shashs)
384			return -ENOMEM;
385
386		for_each_possible_cpu(cpu) {
387			shash = kzalloc_node(shsize, GFP_KERNEL,
388					     cpu_to_node(cpu));
389			if (!shash)
390				return -ENOMEM;
391			*per_cpu_ptr(algo->shashs, cpu) = shash;
392		}
393	}
394
395	return 0;
396}
397
398int __init seg6_hmac_init(void)
399{
400	return seg6_hmac_init_algo();
401}
402
403int __net_init seg6_hmac_net_init(struct net *net)
404{
405	struct seg6_pernet_data *sdata = seg6_pernet(net);
406
407	return rhashtable_init(&sdata->hmac_infos, &rht_params);
408}
409
410void seg6_hmac_exit(void)
411{
412	struct seg6_hmac_algo *algo = NULL;
413	int i, alg_count, cpu;
414
415	alg_count = ARRAY_SIZE(hmac_algos);
416	for (i = 0; i < alg_count; i++) {
417		algo = &hmac_algos[i];
418		for_each_possible_cpu(cpu) {
419			struct crypto_shash *tfm;
420			struct shash_desc *shash;
421
422			shash = *per_cpu_ptr(algo->shashs, cpu);
423			kfree(shash);
424			tfm = *per_cpu_ptr(algo->tfms, cpu);
425			crypto_free_shash(tfm);
426		}
427		free_percpu(algo->tfms);
428		free_percpu(algo->shashs);
429	}
430}
431EXPORT_SYMBOL(seg6_hmac_exit);
432
433void __net_exit seg6_hmac_net_exit(struct net *net)
434{
435	struct seg6_pernet_data *sdata = seg6_pernet(net);
436
437	rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
438}
439EXPORT_SYMBOL(seg6_hmac_net_exit);