xref: /linux/net/ipv6/seg6_hmac.c (revision bc1a59cff9f797bfbf8f3104507584d89e9ecf2e) 
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 
43 struct hmac_storage {
44 	local_lock_t bh_lock;
45 	char hmac_ring[SEG6_HMAC_RING_SIZE];
46 };
47 
48 static DEFINE_PER_CPU(struct hmac_storage, hmac_storage) = {
49 	.bh_lock = INIT_LOCAL_LOCK(bh_lock),
50 };
51 
52 static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
53 {
54 	const struct seg6_hmac_info *hinfo = obj;
55 
56 	return (hinfo->hmackeyid != *(__u32 *)arg->key);
57 }
58 
59 static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
60 {
61 	kfree_rcu(hinfo, rcu);
62 }
63 
64 static void seg6_free_hi(void *ptr, void *arg)
65 {
66 	struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;
67 
68 	if (hinfo)
69 		seg6_hinfo_release(hinfo);
70 }
71 
72 static const struct rhashtable_params rht_params = {
73 	.head_offset		= offsetof(struct seg6_hmac_info, node),
74 	.key_offset		= offsetof(struct seg6_hmac_info, hmackeyid),
75 	.key_len		= sizeof(u32),
76 	.automatic_shrinking	= true,
77 	.obj_cmpfn		= seg6_hmac_cmpfn,
78 };
79 
80 static struct seg6_hmac_algo hmac_algos[] = {
81 	{
82 		.alg_id = SEG6_HMAC_ALGO_SHA1,
83 		.name = "hmac(sha1)",
84 	},
85 	{
86 		.alg_id = SEG6_HMAC_ALGO_SHA256,
87 		.name = "hmac(sha256)",
88 	},
89 };
90 
91 static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
92 {
93 	struct sr6_tlv_hmac *tlv;
94 
95 	if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
96 		return NULL;
97 
98 	if (!sr_has_hmac(srh))
99 		return NULL;
100 
101 	tlv = (struct sr6_tlv_hmac *)
102 	      ((char *)srh + ((srh->hdrlen + 1) << 3) - 40);
103 
104 	if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
105 		return NULL;
106 
107 	return tlv;
108 }
109 
110 static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id)
111 {
112 	struct seg6_hmac_algo *algo;
113 	int i, alg_count;
114 
115 	alg_count = ARRAY_SIZE(hmac_algos);
116 	for (i = 0; i < alg_count; i++) {
117 		algo = &hmac_algos[i];
118 		if (algo->alg_id == alg_id)
119 			return algo;
120 	}
121 
122 	return NULL;
123 }
124 
125 static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize,
126 		     u8 *output, int outlen)
127 {
128 	struct seg6_hmac_algo *algo;
129 	struct crypto_shash *tfm;
130 	struct shash_desc *shash;
131 	int ret, dgsize;
132 
133 	algo = __hmac_get_algo(hinfo->alg_id);
134 	if (!algo)
135 		return -ENOENT;
136 
137 	tfm = *this_cpu_ptr(algo->tfms);
138 
139 	dgsize = crypto_shash_digestsize(tfm);
140 	if (dgsize > outlen) {
141 		pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n",
142 			 dgsize, outlen);
143 		return -ENOMEM;
144 	}
145 
146 	ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen);
147 	if (ret < 0) {
148 		pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret);
149 		goto failed;
150 	}
151 
152 	shash = *this_cpu_ptr(algo->shashs);
153 	shash->tfm = tfm;
154 
155 	ret = crypto_shash_digest(shash, text, psize, output);
156 	if (ret < 0) {
157 		pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret);
158 		goto failed;
159 	}
160 
161 	return dgsize;
162 
163 failed:
164 	return ret;
165 }
166 
167 int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
168 		      struct in6_addr *saddr, u8 *output)
169 {
170 	__be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
171 	u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE];
172 	int plen, i, dgsize, wrsize;
173 	char *ring, *off;
174 
175 	/* a 160-byte buffer for digest output allows to store highest known
176 	 * hash function (RadioGatun) with up to 1216 bits
177 	 */
178 
179 	/* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */
180 	plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;
181 
182 	/* this limit allows for 14 segments */
183 	if (plen >= SEG6_HMAC_RING_SIZE)
184 		return -EMSGSIZE;
185 
186 	/* Let's build the HMAC text on the ring buffer. The text is composed
187 	 * as follows, in order:
188 	 *
189 	 * 1. Source IPv6 address (128 bits)
190 	 * 2. first_segment value (8 bits)
191 	 * 3. Flags (8 bits)
192 	 * 4. HMAC Key ID (32 bits)
193 	 * 5. All segments in the segments list (n * 128 bits)
194 	 */
195 
196 	local_bh_disable();
197 	local_lock_nested_bh(&hmac_storage.bh_lock);
198 	ring = this_cpu_ptr(hmac_storage.hmac_ring);
199 	off = ring;
200 
201 	/* source address */
202 	memcpy(off, saddr, 16);
203 	off += 16;
204 
205 	/* first_segment value */
206 	*off++ = hdr->first_segment;
207 
208 	/* flags */
209 	*off++ = hdr->flags;
210 
211 	/* HMAC Key ID */
212 	memcpy(off, &hmackeyid, 4);
213 	off += 4;
214 
215 	/* all segments in the list */
216 	for (i = 0; i < hdr->first_segment + 1; i++) {
217 		memcpy(off, hdr->segments + i, 16);
218 		off += 16;
219 	}
220 
221 	dgsize = __do_hmac(hinfo, ring, plen, tmp_out,
222 			   SEG6_HMAC_MAX_DIGESTSIZE);
223 	local_unlock_nested_bh(&hmac_storage.bh_lock);
224 	local_bh_enable();
225 
226 	if (dgsize < 0)
227 		return dgsize;
228 
229 	wrsize = SEG6_HMAC_FIELD_LEN;
230 	if (wrsize > dgsize)
231 		wrsize = dgsize;
232 
233 	memset(output, 0, SEG6_HMAC_FIELD_LEN);
234 	memcpy(output, tmp_out, wrsize);
235 
236 	return 0;
237 }
238 EXPORT_SYMBOL(seg6_hmac_compute);
239 
240 /* checks if an incoming SR-enabled packet's HMAC status matches
241  * the incoming policy.
242  *
243  * called with rcu_read_lock()
244  */
245 bool seg6_hmac_validate_skb(struct sk_buff *skb)
246 {
247 	u8 hmac_output[SEG6_HMAC_FIELD_LEN];
248 	struct net *net = dev_net(skb->dev);
249 	struct seg6_hmac_info *hinfo;
250 	struct sr6_tlv_hmac *tlv;
251 	struct ipv6_sr_hdr *srh;
252 	struct inet6_dev *idev;
253 	int require_hmac;
254 
255 	idev = __in6_dev_get(skb->dev);
256 
257 	srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
258 
259 	tlv = seg6_get_tlv_hmac(srh);
260 
261 	require_hmac = READ_ONCE(idev->cnf.seg6_require_hmac);
262 	/* mandatory check but no tlv */
263 	if (require_hmac > 0 && !tlv)
264 		return false;
265 
266 	/* no check */
267 	if (require_hmac < 0)
268 		return true;
269 
270 	/* check only if present */
271 	if (require_hmac == 0 && !tlv)
272 		return true;
273 
274 	/* now, seg6_require_hmac >= 0 && tlv */
275 
276 	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
277 	if (!hinfo)
278 		return false;
279 
280 	if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
281 		return false;
282 
283 	if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
284 		return false;
285 
286 	return true;
287 }
288 EXPORT_SYMBOL(seg6_hmac_validate_skb);
289 
290 /* called with rcu_read_lock() */
291 struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
292 {
293 	struct seg6_pernet_data *sdata = seg6_pernet(net);
294 	struct seg6_hmac_info *hinfo;
295 
296 	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
297 
298 	return hinfo;
299 }
300 EXPORT_SYMBOL(seg6_hmac_info_lookup);
301 
302 int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
303 {
304 	struct seg6_pernet_data *sdata = seg6_pernet(net);
305 	int err;
306 
307 	if (!__hmac_get_algo(hinfo->alg_id))
308 		return -EINVAL;
309 
310 	err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
311 					    rht_params);
312 
313 	return err;
314 }
315 EXPORT_SYMBOL(seg6_hmac_info_add);
316 
317 int seg6_hmac_info_del(struct net *net, u32 key)
318 {
319 	struct seg6_pernet_data *sdata = seg6_pernet(net);
320 	struct seg6_hmac_info *hinfo;
321 	int err = -ENOENT;
322 
323 	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
324 	if (!hinfo)
325 		goto out;
326 
327 	err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
328 				     rht_params);
329 	if (err)
330 		goto out;
331 
332 	seg6_hinfo_release(hinfo);
333 
334 out:
335 	return err;
336 }
337 EXPORT_SYMBOL(seg6_hmac_info_del);
338 
339 int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
340 		   struct ipv6_sr_hdr *srh)
341 {
342 	struct seg6_hmac_info *hinfo;
343 	struct sr6_tlv_hmac *tlv;
344 	int err = -ENOENT;
345 
346 	tlv = seg6_get_tlv_hmac(srh);
347 	if (!tlv)
348 		return -EINVAL;
349 
350 	rcu_read_lock();
351 
352 	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
353 	if (!hinfo)
354 		goto out;
355 
356 	memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
357 	err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
358 
359 out:
360 	rcu_read_unlock();
361 	return err;
362 }
363 EXPORT_SYMBOL(seg6_push_hmac);
364 
365 static int seg6_hmac_init_algo(void)
366 {
367 	struct seg6_hmac_algo *algo;
368 	struct crypto_shash *tfm;
369 	struct shash_desc *shash;
370 	int i, alg_count, cpu;
371 	int ret = -ENOMEM;
372 
373 	alg_count = ARRAY_SIZE(hmac_algos);
374 
375 	for (i = 0; i < alg_count; i++) {
376 		struct crypto_shash **p_tfm;
377 		int shsize;
378 
379 		algo = &hmac_algos[i];
380 		algo->tfms = alloc_percpu(struct crypto_shash *);
381 		if (!algo->tfms)
382 			goto error_out;
383 
384 		for_each_possible_cpu(cpu) {
385 			tfm = crypto_alloc_shash(algo->name, 0, 0);
386 			if (IS_ERR(tfm)) {
387 				ret = PTR_ERR(tfm);
388 				goto error_out;
389 			}
390 			p_tfm = per_cpu_ptr(algo->tfms, cpu);
391 			*p_tfm = tfm;
392 		}
393 
394 		p_tfm = raw_cpu_ptr(algo->tfms);
395 		tfm = *p_tfm;
396 
397 		shsize = sizeof(*shash) + crypto_shash_descsize(tfm);
398 
399 		algo->shashs = alloc_percpu(struct shash_desc *);
400 		if (!algo->shashs)
401 			goto error_out;
402 
403 		for_each_possible_cpu(cpu) {
404 			shash = kzalloc_node(shsize, GFP_KERNEL,
405 					     cpu_to_node(cpu));
406 			if (!shash)
407 				goto error_out;
408 			*per_cpu_ptr(algo->shashs, cpu) = shash;
409 		}
410 	}
411 
412 	return 0;
413 
414 error_out:
415 	seg6_hmac_exit();
416 	return ret;
417 }
418 
419 int __init seg6_hmac_init(void)
420 {
421 	return seg6_hmac_init_algo();
422 }
423 
424 int __net_init seg6_hmac_net_init(struct net *net)
425 {
426 	struct seg6_pernet_data *sdata = seg6_pernet(net);
427 
428 	return rhashtable_init(&sdata->hmac_infos, &rht_params);
429 }
430 
431 void seg6_hmac_exit(void)
432 {
433 	struct seg6_hmac_algo *algo = NULL;
434 	struct crypto_shash *tfm;
435 	struct shash_desc *shash;
436 	int i, alg_count, cpu;
437 
438 	alg_count = ARRAY_SIZE(hmac_algos);
439 	for (i = 0; i < alg_count; i++) {
440 		algo = &hmac_algos[i];
441 
442 		if (algo->shashs) {
443 			for_each_possible_cpu(cpu) {
444 				shash = *per_cpu_ptr(algo->shashs, cpu);
445 				kfree(shash);
446 			}
447 			free_percpu(algo->shashs);
448 		}
449 
450 		if (algo->tfms) {
451 			for_each_possible_cpu(cpu) {
452 				tfm = *per_cpu_ptr(algo->tfms, cpu);
453 				crypto_free_shash(tfm);
454 			}
455 			free_percpu(algo->tfms);
456 		}
457 	}
458 }
459 EXPORT_SYMBOL(seg6_hmac_exit);
460 
461 void __net_exit seg6_hmac_net_exit(struct net *net)
462 {
463 	struct seg6_pernet_data *sdata = seg6_pernet(net);
464 
465 	rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
466 }
467 EXPORT_SYMBOL(seg6_hmac_net_exit);
468