xref: /openbmc/linux/net/ipv6/seg6_hmac.c (revision a2818ee4) 
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 #include <linux/rhashtable.h>
26 
27 #include <linux/netfilter.h>
28 #include <linux/netfilter_ipv6.h>
29 
30 #include <net/sock.h>
31 #include <net/snmp.h>
32 
33 #include <net/ipv6.h>
34 #include <net/protocol.h>
35 #include <net/transp_v6.h>
36 #include <net/rawv6.h>
37 #include <net/ndisc.h>
38 #include <net/ip6_route.h>
39 #include <net/addrconf.h>
40 #include <net/xfrm.h>
41 
42 #include <linux/cryptohash.h>
43 #include <crypto/hash.h>
44 #include <crypto/sha.h>
45 #include <net/seg6.h>
46 #include <net/genetlink.h>
47 #include <net/seg6_hmac.h>
48 #include <linux/random.h>
49 
50 static DEFINE_PER_CPU(char [SEG6_HMAC_RING_SIZE], hmac_ring);
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 	ring = this_cpu_ptr(hmac_ring);
198 	off = ring;
199 
200 	/* source address */
201 	memcpy(off, saddr, 16);
202 	off += 16;
203 
204 	/* first_segment value */
205 	*off++ = hdr->first_segment;
206 
207 	/* flags */
208 	*off++ = hdr->flags;
209 
210 	/* HMAC Key ID */
211 	memcpy(off, &hmackeyid, 4);
212 	off += 4;
213 
214 	/* all segments in the list */
215 	for (i = 0; i < hdr->first_segment + 1; i++) {
216 		memcpy(off, hdr->segments + i, 16);
217 		off += 16;
218 	}
219 
220 	dgsize = __do_hmac(hinfo, ring, plen, tmp_out,
221 			   SEG6_HMAC_MAX_DIGESTSIZE);
222 	local_bh_enable();
223 
224 	if (dgsize < 0)
225 		return dgsize;
226 
227 	wrsize = SEG6_HMAC_FIELD_LEN;
228 	if (wrsize > dgsize)
229 		wrsize = dgsize;
230 
231 	memset(output, 0, SEG6_HMAC_FIELD_LEN);
232 	memcpy(output, tmp_out, wrsize);
233 
234 	return 0;
235 }
236 EXPORT_SYMBOL(seg6_hmac_compute);
237 
238 /* checks if an incoming SR-enabled packet's HMAC status matches
239  * the incoming policy.
240  *
241  * called with rcu_read_lock()
242  */
243 bool seg6_hmac_validate_skb(struct sk_buff *skb)
244 {
245 	u8 hmac_output[SEG6_HMAC_FIELD_LEN];
246 	struct net *net = dev_net(skb->dev);
247 	struct seg6_hmac_info *hinfo;
248 	struct sr6_tlv_hmac *tlv;
249 	struct ipv6_sr_hdr *srh;
250 	struct inet6_dev *idev;
251 
252 	idev = __in6_dev_get(skb->dev);
253 
254 	srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
255 
256 	tlv = seg6_get_tlv_hmac(srh);
257 
258 	/* mandatory check but no tlv */
259 	if (idev->cnf.seg6_require_hmac > 0 && !tlv)
260 		return false;
261 
262 	/* no check */
263 	if (idev->cnf.seg6_require_hmac < 0)
264 		return true;
265 
266 	/* check only if present */
267 	if (idev->cnf.seg6_require_hmac == 0 && !tlv)
268 		return true;
269 
270 	/* now, seg6_require_hmac >= 0 && tlv */
271 
272 	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
273 	if (!hinfo)
274 		return false;
275 
276 	if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
277 		return false;
278 
279 	if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
280 		return false;
281 
282 	return true;
283 }
284 EXPORT_SYMBOL(seg6_hmac_validate_skb);
285 
286 /* called with rcu_read_lock() */
287 struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
288 {
289 	struct seg6_pernet_data *sdata = seg6_pernet(net);
290 	struct seg6_hmac_info *hinfo;
291 
292 	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
293 
294 	return hinfo;
295 }
296 EXPORT_SYMBOL(seg6_hmac_info_lookup);
297 
298 int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
299 {
300 	struct seg6_pernet_data *sdata = seg6_pernet(net);
301 	int err;
302 
303 	err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
304 					    rht_params);
305 
306 	return err;
307 }
308 EXPORT_SYMBOL(seg6_hmac_info_add);
309 
310 int seg6_hmac_info_del(struct net *net, u32 key)
311 {
312 	struct seg6_pernet_data *sdata = seg6_pernet(net);
313 	struct seg6_hmac_info *hinfo;
314 	int err = -ENOENT;
315 
316 	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
317 	if (!hinfo)
318 		goto out;
319 
320 	err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
321 				     rht_params);
322 	if (err)
323 		goto out;
324 
325 	seg6_hinfo_release(hinfo);
326 
327 out:
328 	return err;
329 }
330 EXPORT_SYMBOL(seg6_hmac_info_del);
331 
332 int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
333 		   struct ipv6_sr_hdr *srh)
334 {
335 	struct seg6_hmac_info *hinfo;
336 	struct sr6_tlv_hmac *tlv;
337 	int err = -ENOENT;
338 
339 	tlv = seg6_get_tlv_hmac(srh);
340 	if (!tlv)
341 		return -EINVAL;
342 
343 	rcu_read_lock();
344 
345 	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
346 	if (!hinfo)
347 		goto out;
348 
349 	memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
350 	err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
351 
352 out:
353 	rcu_read_unlock();
354 	return err;
355 }
356 EXPORT_SYMBOL(seg6_push_hmac);
357 
358 static int seg6_hmac_init_algo(void)
359 {
360 	struct seg6_hmac_algo *algo;
361 	struct crypto_shash *tfm;
362 	struct shash_desc *shash;
363 	int i, alg_count, cpu;
364 
365 	alg_count = ARRAY_SIZE(hmac_algos);
366 
367 	for (i = 0; i < alg_count; i++) {
368 		struct crypto_shash **p_tfm;
369 		int shsize;
370 
371 		algo = &hmac_algos[i];
372 		algo->tfms = alloc_percpu(struct crypto_shash *);
373 		if (!algo->tfms)
374 			return -ENOMEM;
375 
376 		for_each_possible_cpu(cpu) {
377 			tfm = crypto_alloc_shash(algo->name, 0, 0);
378 			if (IS_ERR(tfm))
379 				return PTR_ERR(tfm);
380 			p_tfm = per_cpu_ptr(algo->tfms, cpu);
381 			*p_tfm = tfm;
382 		}
383 
384 		p_tfm = raw_cpu_ptr(algo->tfms);
385 		tfm = *p_tfm;
386 
387 		shsize = sizeof(*shash) + crypto_shash_descsize(tfm);
388 
389 		algo->shashs = alloc_percpu(struct shash_desc *);
390 		if (!algo->shashs)
391 			return -ENOMEM;
392 
393 		for_each_possible_cpu(cpu) {
394 			shash = kzalloc_node(shsize, GFP_KERNEL,
395 					     cpu_to_node(cpu));
396 			if (!shash)
397 				return -ENOMEM;
398 			*per_cpu_ptr(algo->shashs, cpu) = shash;
399 		}
400 	}
401 
402 	return 0;
403 }
404 
405 int __init seg6_hmac_init(void)
406 {
407 	return seg6_hmac_init_algo();
408 }
409 EXPORT_SYMBOL(seg6_hmac_init);
410 
411 int __net_init seg6_hmac_net_init(struct net *net)
412 {
413 	struct seg6_pernet_data *sdata = seg6_pernet(net);
414 
415 	rhashtable_init(&sdata->hmac_infos, &rht_params);
416 
417 	return 0;
418 }
419 EXPORT_SYMBOL(seg6_hmac_net_init);
420 
421 void seg6_hmac_exit(void)
422 {
423 	struct seg6_hmac_algo *algo = NULL;
424 	int i, alg_count, cpu;
425 
426 	alg_count = ARRAY_SIZE(hmac_algos);
427 	for (i = 0; i < alg_count; i++) {
428 		algo = &hmac_algos[i];
429 		for_each_possible_cpu(cpu) {
430 			struct crypto_shash *tfm;
431 			struct shash_desc *shash;
432 
433 			shash = *per_cpu_ptr(algo->shashs, cpu);
434 			kfree(shash);
435 			tfm = *per_cpu_ptr(algo->tfms, cpu);
436 			crypto_free_shash(tfm);
437 		}
438 		free_percpu(algo->tfms);
439 		free_percpu(algo->shashs);
440 	}
441 }
442 EXPORT_SYMBOL(seg6_hmac_exit);
443 
444 void __net_exit seg6_hmac_net_exit(struct net *net)
445 {
446 	struct seg6_pernet_data *sdata = seg6_pernet(net);
447 
448 	rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
449 }
450 EXPORT_SYMBOL(seg6_hmac_net_exit);
451