summaryrefslogtreecommitdiff
path: root/net/ipv6/seg6_hmac.c
blob: 861e0366f549d523f20dc92c79bef1be8805e0c7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  SR-IPv6 implementation -- HMAC functions
 *
 *  Author:
 *  David Lebrun <david.lebrun@uclouvain.be>
 */

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/in6.h>
#include <linux/icmpv6.h>
#include <linux/mroute6.h>
#include <linux/slab.h>
#include <linux/rhashtable.h>

#include <linux/netfilter.h>
#include <linux/netfilter_ipv6.h>

#include <net/sock.h>
#include <net/snmp.h>

#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/transp_v6.h>
#include <net/rawv6.h>
#include <net/ndisc.h>
#include <net/ip6_route.h>
#include <net/addrconf.h>
#include <net/xfrm.h>

#include <crypto/hash.h>
#include <net/seg6.h>
#include <net/genetlink.h>
#include <net/seg6_hmac.h>
#include <linux/random.h>

static DEFINE_PER_CPU(char [SEG6_HMAC_RING_SIZE], hmac_ring);

static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
{
	const struct seg6_hmac_info *hinfo = obj;

	return (hinfo->hmackeyid != *(__u32 *)arg->key);
}

static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
{
	kfree_rcu(hinfo, rcu);
}

static void seg6_free_hi(void *ptr, void *arg)
{
	struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;

	if (hinfo)
		seg6_hinfo_release(hinfo);
}

static const struct rhashtable_params rht_params = {
	.head_offset		= offsetof(struct seg6_hmac_info, node),
	.key_offset		= offsetof(struct seg6_hmac_info, hmackeyid),
	.key_len		= sizeof(u32),
	.automatic_shrinking	= true,
	.obj_cmpfn		= seg6_hmac_cmpfn,
};

static struct seg6_hmac_algo hmac_algos[] = {
	{
		.alg_id = SEG6_HMAC_ALGO_SHA1,
		.name = "hmac(sha1)",
	},
	{
		.alg_id = SEG6_HMAC_ALGO_SHA256,
		.name = "hmac(sha256)",
	},
};

static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
{
	struct sr6_tlv_hmac *tlv;

	if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
		return NULL;

	if (!sr_has_hmac(srh))
		return NULL;

	tlv = (struct sr6_tlv_hmac *)
	      ((char *)srh + ((srh->hdrlen + 1) << 3) - 40);

	if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
		return NULL;

	return tlv;
}

static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id)
{
	struct seg6_hmac_algo *algo;
	int i, alg_count;

	alg_count = ARRAY_SIZE(hmac_algos);
	for (i = 0; i < alg_count; i++) {
		algo = &hmac_algos[i];
		if (algo->alg_id == alg_id)
			return algo;
	}

	return NULL;
}

static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize,
		     u8 *output, int outlen)
{
	struct seg6_hmac_algo *algo;
	struct crypto_shash *tfm;
	struct shash_desc *shash;
	int ret, dgsize;

	algo = __hmac_get_algo(hinfo->alg_id);
	if (!algo)
		return -ENOENT;

	tfm = *this_cpu_ptr(algo->tfms);

	dgsize = crypto_shash_digestsize(tfm);
	if (dgsize > outlen) {
		pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n",
			 dgsize, outlen);
		return -ENOMEM;
	}

	ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen);
	if (ret < 0) {
		pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret);
		goto failed;
	}

	shash = *this_cpu_ptr(algo->shashs);
	shash->tfm = tfm;

	ret = crypto_shash_digest(shash, text, psize, output);
	if (ret < 0) {
		pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret);
		goto failed;
	}

	return dgsize;

failed:
	return ret;
}

int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
		      struct in6_addr *saddr, u8 *output)
{
	__be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
	u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE];
	int plen, i, dgsize, wrsize;
	char *ring, *off;

	/* a 160-byte buffer for digest output allows to store highest known
	 * hash function (RadioGatun) with up to 1216 bits
	 */

	/* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */
	plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;

	/* this limit allows for 14 segments */
	if (plen >= SEG6_HMAC_RING_SIZE)
		return -EMSGSIZE;

	/* Let's build the HMAC text on the ring buffer. The text is composed
	 * as follows, in order:
	 *
	 * 1. Source IPv6 address (128 bits)
	 * 2. first_segment value (8 bits)
	 * 3. Flags (8 bits)
	 * 4. HMAC Key ID (32 bits)
	 * 5. All segments in the segments list (n * 128 bits)
	 */

	local_bh_disable();
	ring = this_cpu_ptr(hmac_ring);
	off = ring;

	/* source address */
	memcpy(off, saddr, 16);
	off += 16;

	/* first_segment value */
	*off++ = hdr->first_segment;

	/* flags */
	*off++ = hdr->flags;

	/* HMAC Key ID */
	memcpy(off, &hmackeyid, 4);
	off += 4;

	/* all segments in the list */
	for (i = 0; i < hdr->first_segment + 1; i++) {
		memcpy(off, hdr->segments + i, 16);
		off += 16;
	}

	dgsize = __do_hmac(hinfo, ring, plen, tmp_out,
			   SEG6_HMAC_MAX_DIGESTSIZE);
	local_bh_enable();

	if (dgsize < 0)
		return dgsize;

	wrsize = SEG6_HMAC_FIELD_LEN;
	if (wrsize > dgsize)
		wrsize = dgsize;

	memset(output, 0, SEG6_HMAC_FIELD_LEN);
	memcpy(output, tmp_out, wrsize);

	return 0;
}
EXPORT_SYMBOL(seg6_hmac_compute);

/* checks if an incoming SR-enabled packet's HMAC status matches
 * the incoming policy.
 *
 * called with rcu_read_lock()
 */
bool seg6_hmac_validate_skb(struct sk_buff *skb)
{
	u8 hmac_output[SEG6_HMAC_FIELD_LEN];
	struct net *net = dev_net(skb->dev);
	struct seg6_hmac_info *hinfo;
	struct sr6_tlv_hmac *tlv;
	struct ipv6_sr_hdr *srh;
	struct inet6_dev *idev;
	int require_hmac;

	idev = __in6_dev_get(skb->dev);

	srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);

	tlv = seg6_get_tlv_hmac(srh);

	require_hmac = READ_ONCE(idev->cnf.seg6_require_hmac);
	/* mandatory check but no tlv */
	if (require_hmac > 0 && !tlv)
		return false;

	/* no check */
	if (require_hmac < 0)
		return true;

	/* check only if present */
	if (require_hmac == 0 && !tlv)
		return true;

	/* now, seg6_require_hmac >= 0 && tlv */

	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
	if (!hinfo)
		return false;

	if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
		return false;

	if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
		return false;

	return true;
}
EXPORT_SYMBOL(seg6_hmac_validate_skb);

/* called with rcu_read_lock() */
struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
{
	struct seg6_pernet_data *sdata = seg6_pernet(net);
	struct seg6_hmac_info *hinfo;

	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);

	return hinfo;
}
EXPORT_SYMBOL(seg6_hmac_info_lookup);

int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
{
	struct seg6_pernet_data *sdata = seg6_pernet(net);
	int err;

	err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
					    rht_params);

	return err;
}
EXPORT_SYMBOL(seg6_hmac_info_add);

int seg6_hmac_info_del(struct net *net, u32 key)
{
	struct seg6_pernet_data *sdata = seg6_pernet(net);
	struct seg6_hmac_info *hinfo;
	int err = -ENOENT;

	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
	if (!hinfo)
		goto out;

	err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
				     rht_params);
	if (err)
		goto out;

	seg6_hinfo_release(hinfo);

out:
	return err;
}
EXPORT_SYMBOL(seg6_hmac_info_del);

int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
		   struct ipv6_sr_hdr *srh)
{
	struct seg6_hmac_info *hinfo;
	struct sr6_tlv_hmac *tlv;
	int err = -ENOENT;

	tlv = seg6_get_tlv_hmac(srh);
	if (!tlv)
		return -EINVAL;

	rcu_read_lock();

	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
	if (!hinfo)
		goto out;

	memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
	err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);

out:
	rcu_read_unlock();
	return err;
}
EXPORT_SYMBOL(seg6_push_hmac);

static int seg6_hmac_init_algo(void)
{
	struct seg6_hmac_algo *algo;
	struct crypto_shash *tfm;
	struct shash_desc *shash;
	int i, alg_count, cpu;

	alg_count = ARRAY_SIZE(hmac_algos);

	for (i = 0; i < alg_count; i++) {
		struct crypto_shash **p_tfm;
		int shsize;

		algo = &hmac_algos[i];
		algo->tfms = alloc_percpu(struct crypto_shash *);
		if (!algo->tfms)
			return -ENOMEM;

		for_each_possible_cpu(cpu) {
			tfm = crypto_alloc_shash(algo->name, 0, 0);
			if (IS_ERR(tfm))
				return PTR_ERR(tfm);
			p_tfm = per_cpu_ptr(algo->tfms, cpu);
			*p_tfm = tfm;
		}

		p_tfm = raw_cpu_ptr(algo->tfms);
		tfm = *p_tfm;

		shsize = sizeof(*shash) + crypto_shash_descsize(tfm);

		algo->shashs = alloc_percpu(struct shash_desc *);
		if (!algo->shashs)
			return -ENOMEM;

		for_each_possible_cpu(cpu) {
			shash = kzalloc_node(shsize, GFP_KERNEL,
					     cpu_to_node(cpu));
			if (!shash)
				return -ENOMEM;
			*per_cpu_ptr(algo->shashs, cpu) = shash;
		}
	}

	return 0;
}

int __init seg6_hmac_init(void)
{
	return seg6_hmac_init_algo();
}

int __net_init seg6_hmac_net_init(struct net *net)
{
	struct seg6_pernet_data *sdata = seg6_pernet(net);

	return rhashtable_init(&sdata->hmac_infos, &rht_params);
}

void seg6_hmac_exit(void)
{
	struct seg6_hmac_algo *algo = NULL;
	int i, alg_count, cpu;

	alg_count = ARRAY_SIZE(hmac_algos);
	for (i = 0; i < alg_count; i++) {
		algo = &hmac_algos[i];
		for_each_possible_cpu(cpu) {
			struct crypto_shash *tfm;
			struct shash_desc *shash;

			shash = *per_cpu_ptr(algo->shashs, cpu);
			kfree(shash);
			tfm = *per_cpu_ptr(algo->tfms, cpu);
			crypto_free_shash(tfm);
		}
		free_percpu(algo->tfms);
		free_percpu(algo->shashs);
	}
}
EXPORT_SYMBOL(seg6_hmac_exit);

void __net_exit seg6_hmac_net_exit(struct net *net)
{
	struct seg6_pernet_data *sdata = seg6_pernet(net);

	rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
}
EXPORT_SYMBOL(seg6_hmac_net_exit);