xref: /linux/net/ipv6/seg6_hmac.c (revision b4ada0618eed0fbd1b1630f73deb048c592b06a1) 
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 <crypto/utils.h>
39 #include <net/seg6.h>
40 #include <net/genetlink.h>
41 #include <net/seg6_hmac.h>
42 #include <linux/random.h>
43 
44 struct hmac_storage {
45 	local_lock_t bh_lock;
46 	char hmac_ring[SEG6_HMAC_RING_SIZE];
47 };
48 
49 static DEFINE_PER_CPU(struct hmac_storage, hmac_storage) = {
50 	.bh_lock = INIT_LOCAL_LOCK(bh_lock),
51 };
52 
53 static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
54 {
55 	const struct seg6_hmac_info *hinfo = obj;
56 
57 	return (hinfo->hmackeyid != *(__u32 *)arg->key);
58 }
59 
60 static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
61 {
62 	kfree_rcu(hinfo, rcu);
63 }
64 
65 static void seg6_free_hi(void *ptr, void *arg)
66 {
67 	struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;
68 
69 	if (hinfo)
70 		seg6_hinfo_release(hinfo);
71 }
72 
73 static const struct rhashtable_params rht_params = {
74 	.head_offset		= offsetof(struct seg6_hmac_info, node),
75 	.key_offset		= offsetof(struct seg6_hmac_info, hmackeyid),
76 	.key_len		= sizeof(u32),
77 	.automatic_shrinking	= true,
78 	.obj_cmpfn		= seg6_hmac_cmpfn,
79 };
80 
81 static struct seg6_hmac_algo hmac_algos[] = {
82 	{
83 		.alg_id = SEG6_HMAC_ALGO_SHA1,
84 		.name = "hmac(sha1)",
85 	},
86 	{
87 		.alg_id = SEG6_HMAC_ALGO_SHA256,
88 		.name = "hmac(sha256)",
89 	},
90 };
91 
92 static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
93 {
94 	struct sr6_tlv_hmac *tlv;
95 
96 	if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
97 		return NULL;
98 
99 	if (!sr_has_hmac(srh))
100 		return NULL;
101 
102 	tlv = (struct sr6_tlv_hmac *)
103 	      ((char *)srh + ((srh->hdrlen + 1) << 3) - 40);
104 
105 	if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
106 		return NULL;
107 
108 	return tlv;
109 }
110 
111 static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id)
112 {
113 	struct seg6_hmac_algo *algo;
114 	int i, alg_count;
115 
116 	alg_count = ARRAY_SIZE(hmac_algos);
117 	for (i = 0; i < alg_count; i++) {
118 		algo = &hmac_algos[i];
119 		if (algo->alg_id == alg_id)
120 			return algo;
121 	}
122 
123 	return NULL;
124 }
125 
126 static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize,
127 		     u8 *output, int outlen)
128 {
129 	struct seg6_hmac_algo *algo;
130 	struct crypto_shash *tfm;
131 	struct shash_desc *shash;
132 	int ret, dgsize;
133 
134 	algo = __hmac_get_algo(hinfo->alg_id);
135 	if (!algo)
136 		return -ENOENT;
137 
138 	tfm = *this_cpu_ptr(algo->tfms);
139 
140 	dgsize = crypto_shash_digestsize(tfm);
141 	if (dgsize > outlen) {
142 		pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n",
143 			 dgsize, outlen);
144 		return -ENOMEM;
145 	}
146 
147 	ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen);
148 	if (ret < 0) {
149 		pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret);
150 		goto failed;
151 	}
152 
153 	shash = *this_cpu_ptr(algo->shashs);
154 	shash->tfm = tfm;
155 
156 	ret = crypto_shash_digest(shash, text, psize, output);
157 	if (ret < 0) {
158 		pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret);
159 		goto failed;
160 	}
161 
162 	return dgsize;
163 
164 failed:
165 	return ret;
166 }
167 
168 int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
169 		      struct in6_addr *saddr, u8 *output)
170 {
171 	__be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
172 	u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE];
173 	int plen, i, dgsize, wrsize;
174 	char *ring, *off;
175 
176 	/* a 160-byte buffer for digest output allows to store highest known
177 	 * hash function (RadioGatun) with up to 1216 bits
178 	 */
179 
180 	/* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */
181 	plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;
182 
183 	/* this limit allows for 14 segments */
184 	if (plen >= SEG6_HMAC_RING_SIZE)
185 		return -EMSGSIZE;
186 
187 	/* Let's build the HMAC text on the ring buffer. The text is composed
188 	 * as follows, in order:
189 	 *
190 	 * 1. Source IPv6 address (128 bits)
191 	 * 2. first_segment value (8 bits)
192 	 * 3. Flags (8 bits)
193 	 * 4. HMAC Key ID (32 bits)
194 	 * 5. All segments in the segments list (n * 128 bits)
195 	 */
196 
197 	local_bh_disable();
198 	local_lock_nested_bh(&hmac_storage.bh_lock);
199 	ring = this_cpu_ptr(hmac_storage.hmac_ring);
200 	off = ring;
201 
202 	/* source address */
203 	memcpy(off, saddr, 16);
204 	off += 16;
205 
206 	/* first_segment value */
207 	*off++ = hdr->first_segment;
208 
209 	/* flags */
210 	*off++ = hdr->flags;
211 
212 	/* HMAC Key ID */
213 	memcpy(off, &hmackeyid, 4);
214 	off += 4;
215 
216 	/* all segments in the list */
217 	for (i = 0; i < hdr->first_segment + 1; i++) {
218 		memcpy(off, hdr->segments + i, 16);
219 		off += 16;
220 	}
221 
222 	dgsize = __do_hmac(hinfo, ring, plen, tmp_out,
223 			   SEG6_HMAC_MAX_DIGESTSIZE);
224 	local_unlock_nested_bh(&hmac_storage.bh_lock);
225 	local_bh_enable();
226 
227 	if (dgsize < 0)
228 		return dgsize;
229 
230 	wrsize = SEG6_HMAC_FIELD_LEN;
231 	if (wrsize > dgsize)
232 		wrsize = dgsize;
233 
234 	memset(output, 0, SEG6_HMAC_FIELD_LEN);
235 	memcpy(output, tmp_out, wrsize);
236 
237 	return 0;
238 }
239 EXPORT_SYMBOL(seg6_hmac_compute);
240 
241 /* checks if an incoming SR-enabled packet's HMAC status matches
242  * the incoming policy.
243  *
244  * called with rcu_read_lock()
245  */
246 bool seg6_hmac_validate_skb(struct sk_buff *skb)
247 {
248 	u8 hmac_output[SEG6_HMAC_FIELD_LEN];
249 	struct net *net = dev_net(skb->dev);
250 	struct seg6_hmac_info *hinfo;
251 	struct sr6_tlv_hmac *tlv;
252 	struct ipv6_sr_hdr *srh;
253 	struct inet6_dev *idev;
254 	int require_hmac;
255 
256 	idev = __in6_dev_get(skb->dev);
257 
258 	srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
259 
260 	tlv = seg6_get_tlv_hmac(srh);
261 
262 	require_hmac = READ_ONCE(idev->cnf.seg6_require_hmac);
263 	/* mandatory check but no tlv */
264 	if (require_hmac > 0 && !tlv)
265 		return false;
266 
267 	/* no check */
268 	if (require_hmac < 0)
269 		return true;
270 
271 	/* check only if present */
272 	if (require_hmac == 0 && !tlv)
273 		return true;
274 
275 	/* now, seg6_require_hmac >= 0 && tlv */
276 
277 	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
278 	if (!hinfo)
279 		return false;
280 
281 	if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
282 		return false;
283 
284 	if (crypto_memneq(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN))
285 		return false;
286 
287 	return true;
288 }
289 EXPORT_SYMBOL(seg6_hmac_validate_skb);
290 
291 /* called with rcu_read_lock() */
292 struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
293 {
294 	struct seg6_pernet_data *sdata = seg6_pernet(net);
295 	struct seg6_hmac_info *hinfo;
296 
297 	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
298 
299 	return hinfo;
300 }
301 EXPORT_SYMBOL(seg6_hmac_info_lookup);
302 
303 int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
304 {
305 	struct seg6_pernet_data *sdata = seg6_pernet(net);
306 	int err;
307 
308 	if (!__hmac_get_algo(hinfo->alg_id))
309 		return -EINVAL;
310 
311 	err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
312 					    rht_params);
313 
314 	return err;
315 }
316 EXPORT_SYMBOL(seg6_hmac_info_add);
317 
318 int seg6_hmac_info_del(struct net *net, u32 key)
319 {
320 	struct seg6_pernet_data *sdata = seg6_pernet(net);
321 	struct seg6_hmac_info *hinfo;
322 	int err = -ENOENT;
323 
324 	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
325 	if (!hinfo)
326 		goto out;
327 
328 	err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
329 				     rht_params);
330 	if (err)
331 		goto out;
332 
333 	seg6_hinfo_release(hinfo);
334 
335 out:
336 	return err;
337 }
338 EXPORT_SYMBOL(seg6_hmac_info_del);
339 
340 int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
341 		   struct ipv6_sr_hdr *srh)
342 {
343 	struct seg6_hmac_info *hinfo;
344 	struct sr6_tlv_hmac *tlv;
345 	int err = -ENOENT;
346 
347 	tlv = seg6_get_tlv_hmac(srh);
348 	if (!tlv)
349 		return -EINVAL;
350 
351 	rcu_read_lock();
352 
353 	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
354 	if (!hinfo)
355 		goto out;
356 
357 	memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
358 	err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
359 
360 out:
361 	rcu_read_unlock();
362 	return err;
363 }
364 EXPORT_SYMBOL(seg6_push_hmac);
365 
366 static int seg6_hmac_init_algo(void)
367 {
368 	struct seg6_hmac_algo *algo;
369 	struct crypto_shash *tfm;
370 	struct shash_desc *shash;
371 	int i, alg_count, cpu;
372 	int ret = -ENOMEM;
373 
374 	alg_count = ARRAY_SIZE(hmac_algos);
375 
376 	for (i = 0; i < alg_count; i++) {
377 		struct crypto_shash **p_tfm;
378 		int shsize;
379 
380 		algo = &hmac_algos[i];
381 		algo->tfms = alloc_percpu(struct crypto_shash *);
382 		if (!algo->tfms)
383 			goto error_out;
384 
385 		for_each_possible_cpu(cpu) {
386 			tfm = crypto_alloc_shash(algo->name, 0, 0);
387 			if (IS_ERR(tfm)) {
388 				ret = PTR_ERR(tfm);
389 				goto error_out;
390 			}
391 			p_tfm = per_cpu_ptr(algo->tfms, cpu);
392 			*p_tfm = tfm;
393 		}
394 
395 		p_tfm = raw_cpu_ptr(algo->tfms);
396 		tfm = *p_tfm;
397 
398 		shsize = sizeof(*shash) + crypto_shash_descsize(tfm);
399 
400 		algo->shashs = alloc_percpu(struct shash_desc *);
401 		if (!algo->shashs)
402 			goto error_out;
403 
404 		for_each_possible_cpu(cpu) {
405 			shash = kzalloc_node(shsize, GFP_KERNEL,
406 					     cpu_to_node(cpu));
407 			if (!shash)
408 				goto error_out;
409 			*per_cpu_ptr(algo->shashs, cpu) = shash;
410 		}
411 	}
412 
413 	return 0;
414 
415 error_out:
416 	seg6_hmac_exit();
417 	return ret;
418 }
419 
420 int __init seg6_hmac_init(void)
421 {
422 	return seg6_hmac_init_algo();
423 }
424 
425 int __net_init seg6_hmac_net_init(struct net *net)
426 {
427 	struct seg6_pernet_data *sdata = seg6_pernet(net);
428 
429 	return rhashtable_init(&sdata->hmac_infos, &rht_params);
430 }
431 
432 void seg6_hmac_exit(void)
433 {
434 	struct seg6_hmac_algo *algo = NULL;
435 	struct crypto_shash *tfm;
436 	struct shash_desc *shash;
437 	int i, alg_count, cpu;
438 
439 	alg_count = ARRAY_SIZE(hmac_algos);
440 	for (i = 0; i < alg_count; i++) {
441 		algo = &hmac_algos[i];
442 
443 		if (algo->shashs) {
444 			for_each_possible_cpu(cpu) {
445 				shash = *per_cpu_ptr(algo->shashs, cpu);
446 				kfree(shash);
447 			}
448 			free_percpu(algo->shashs);
449 		}
450 
451 		if (algo->tfms) {
452 			for_each_possible_cpu(cpu) {
453 				tfm = *per_cpu_ptr(algo->tfms, cpu);
454 				crypto_free_shash(tfm);
455 			}
456 			free_percpu(algo->tfms);
457 		}
458 	}
459 }
460 EXPORT_SYMBOL(seg6_hmac_exit);
461 
462 void __net_exit seg6_hmac_net_exit(struct net *net)
463 {
464 	struct seg6_pernet_data *sdata = seg6_pernet(net);
465 
466 	rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
467 }
468 EXPORT_SYMBOL(seg6_hmac_net_exit);
469