xref: /openbmc/linux/net/ipv6/seg6_hmac.c (revision ddc141e5) 
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 
26 #include <linux/netfilter.h>
27 #include <linux/netfilter_ipv6.h>
28 
29 #include <net/sock.h>
30 #include <net/snmp.h>
31 
32 #include <net/ipv6.h>
33 #include <net/protocol.h>
34 #include <net/transp_v6.h>
35 #include <net/rawv6.h>
36 #include <net/ndisc.h>
37 #include <net/ip6_route.h>
38 #include <net/addrconf.h>
39 #include <net/xfrm.h>
40 
41 #include <linux/cryptohash.h>
42 #include <crypto/hash.h>
43 #include <crypto/sha.h>
44 #include <net/seg6.h>
45 #include <net/genetlink.h>
46 #include <net/seg6_hmac.h>
47 #include <linux/random.h>
48 
49 static DEFINE_PER_CPU(char [SEG6_HMAC_RING_SIZE], hmac_ring);
50 
51 static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
52 {
53 	const struct seg6_hmac_info *hinfo = obj;
54 
55 	return (hinfo->hmackeyid != *(__u32 *)arg->key);
56 }
57 
58 static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
59 {
60 	kfree_rcu(hinfo, rcu);
61 }
62 
63 static void seg6_free_hi(void *ptr, void *arg)
64 {
65 	struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;
66 
67 	if (hinfo)
68 		seg6_hinfo_release(hinfo);
69 }
70 
71 static const struct rhashtable_params rht_params = {
72 	.head_offset		= offsetof(struct seg6_hmac_info, node),
73 	.key_offset		= offsetof(struct seg6_hmac_info, hmackeyid),
74 	.key_len		= sizeof(u32),
75 	.automatic_shrinking	= true,
76 	.obj_cmpfn		= seg6_hmac_cmpfn,
77 };
78 
79 static struct seg6_hmac_algo hmac_algos[] = {
80 	{
81 		.alg_id = SEG6_HMAC_ALGO_SHA1,
82 		.name = "hmac(sha1)",
83 	},
84 	{
85 		.alg_id = SEG6_HMAC_ALGO_SHA256,
86 		.name = "hmac(sha256)",
87 	},
88 };
89 
90 static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
91 {
92 	struct sr6_tlv_hmac *tlv;
93 
94 	if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
95 		return NULL;
96 
97 	if (!sr_has_hmac(srh))
98 		return NULL;
99 
100 	tlv = (struct sr6_tlv_hmac *)
101 	      ((char *)srh + ((srh->hdrlen + 1) << 3) - 40);
102 
103 	if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
104 		return NULL;
105 
106 	return tlv;
107 }
108 
109 static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id)
110 {
111 	struct seg6_hmac_algo *algo;
112 	int i, alg_count;
113 
114 	alg_count = ARRAY_SIZE(hmac_algos);
115 	for (i = 0; i < alg_count; i++) {
116 		algo = &hmac_algos[i];
117 		if (algo->alg_id == alg_id)
118 			return algo;
119 	}
120 
121 	return NULL;
122 }
123 
124 static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize,
125 		     u8 *output, int outlen)
126 {
127 	struct seg6_hmac_algo *algo;
128 	struct crypto_shash *tfm;
129 	struct shash_desc *shash;
130 	int ret, dgsize;
131 
132 	algo = __hmac_get_algo(hinfo->alg_id);
133 	if (!algo)
134 		return -ENOENT;
135 
136 	tfm = *this_cpu_ptr(algo->tfms);
137 
138 	dgsize = crypto_shash_digestsize(tfm);
139 	if (dgsize > outlen) {
140 		pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n",
141 			 dgsize, outlen);
142 		return -ENOMEM;
143 	}
144 
145 	ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen);
146 	if (ret < 0) {
147 		pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret);
148 		goto failed;
149 	}
150 
151 	shash = *this_cpu_ptr(algo->shashs);
152 	shash->tfm = tfm;
153 
154 	ret = crypto_shash_digest(shash, text, psize, output);
155 	if (ret < 0) {
156 		pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret);
157 		goto failed;
158 	}
159 
160 	return dgsize;
161 
162 failed:
163 	return ret;
164 }
165 
166 int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
167 		      struct in6_addr *saddr, u8 *output)
168 {
169 	__be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
170 	u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE];
171 	int plen, i, dgsize, wrsize;
172 	char *ring, *off;
173 
174 	/* a 160-byte buffer for digest output allows to store highest known
175 	 * hash function (RadioGatun) with up to 1216 bits
176 	 */
177 
178 	/* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */
179 	plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;
180 
181 	/* this limit allows for 14 segments */
182 	if (plen >= SEG6_HMAC_RING_SIZE)
183 		return -EMSGSIZE;
184 
185 	/* Let's build the HMAC text on the ring buffer. The text is composed
186 	 * as follows, in order:
187 	 *
188 	 * 1. Source IPv6 address (128 bits)
189 	 * 2. first_segment value (8 bits)
190 	 * 3. Flags (8 bits)
191 	 * 4. HMAC Key ID (32 bits)
192 	 * 5. All segments in the segments list (n * 128 bits)
193 	 */
194 
195 	local_bh_disable();
196 	ring = this_cpu_ptr(hmac_ring);
197 	off = ring;
198 
199 	/* source address */
200 	memcpy(off, saddr, 16);
201 	off += 16;
202 
203 	/* first_segment value */
204 	*off++ = hdr->first_segment;
205 
206 	/* flags */
207 	*off++ = hdr->flags;
208 
209 	/* HMAC Key ID */
210 	memcpy(off, &hmackeyid, 4);
211 	off += 4;
212 
213 	/* all segments in the list */
214 	for (i = 0; i < hdr->first_segment + 1; i++) {
215 		memcpy(off, hdr->segments + i, 16);
216 		off += 16;
217 	}
218 
219 	dgsize = __do_hmac(hinfo, ring, plen, tmp_out,
220 			   SEG6_HMAC_MAX_DIGESTSIZE);
221 	local_bh_enable();
222 
223 	if (dgsize < 0)
224 		return dgsize;
225 
226 	wrsize = SEG6_HMAC_FIELD_LEN;
227 	if (wrsize > dgsize)
228 		wrsize = dgsize;
229 
230 	memset(output, 0, SEG6_HMAC_FIELD_LEN);
231 	memcpy(output, tmp_out, wrsize);
232 
233 	return 0;
234 }
235 EXPORT_SYMBOL(seg6_hmac_compute);
236 
237 /* checks if an incoming SR-enabled packet's HMAC status matches
238  * the incoming policy.
239  *
240  * called with rcu_read_lock()
241  */
242 bool seg6_hmac_validate_skb(struct sk_buff *skb)
243 {
244 	u8 hmac_output[SEG6_HMAC_FIELD_LEN];
245 	struct net *net = dev_net(skb->dev);
246 	struct seg6_hmac_info *hinfo;
247 	struct sr6_tlv_hmac *tlv;
248 	struct ipv6_sr_hdr *srh;
249 	struct inet6_dev *idev;
250 
251 	idev = __in6_dev_get(skb->dev);
252 
253 	srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
254 
255 	tlv = seg6_get_tlv_hmac(srh);
256 
257 	/* mandatory check but no tlv */
258 	if (idev->cnf.seg6_require_hmac > 0 && !tlv)
259 		return false;
260 
261 	/* no check */
262 	if (idev->cnf.seg6_require_hmac < 0)
263 		return true;
264 
265 	/* check only if present */
266 	if (idev->cnf.seg6_require_hmac == 0 && !tlv)
267 		return true;
268 
269 	/* now, seg6_require_hmac >= 0 && tlv */
270 
271 	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
272 	if (!hinfo)
273 		return false;
274 
275 	if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
276 		return false;
277 
278 	if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
279 		return false;
280 
281 	return true;
282 }
283 EXPORT_SYMBOL(seg6_hmac_validate_skb);
284 
285 /* called with rcu_read_lock() */
286 struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
287 {
288 	struct seg6_pernet_data *sdata = seg6_pernet(net);
289 	struct seg6_hmac_info *hinfo;
290 
291 	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
292 
293 	return hinfo;
294 }
295 EXPORT_SYMBOL(seg6_hmac_info_lookup);
296 
297 int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
298 {
299 	struct seg6_pernet_data *sdata = seg6_pernet(net);
300 	int err;
301 
302 	err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
303 					    rht_params);
304 
305 	return err;
306 }
307 EXPORT_SYMBOL(seg6_hmac_info_add);
308 
309 int seg6_hmac_info_del(struct net *net, u32 key)
310 {
311 	struct seg6_pernet_data *sdata = seg6_pernet(net);
312 	struct seg6_hmac_info *hinfo;
313 	int err = -ENOENT;
314 
315 	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
316 	if (!hinfo)
317 		goto out;
318 
319 	err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
320 				     rht_params);
321 	if (err)
322 		goto out;
323 
324 	seg6_hinfo_release(hinfo);
325 
326 out:
327 	return err;
328 }
329 EXPORT_SYMBOL(seg6_hmac_info_del);
330 
331 int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
332 		   struct ipv6_sr_hdr *srh)
333 {
334 	struct seg6_hmac_info *hinfo;
335 	struct sr6_tlv_hmac *tlv;
336 	int err = -ENOENT;
337 
338 	tlv = seg6_get_tlv_hmac(srh);
339 	if (!tlv)
340 		return -EINVAL;
341 
342 	rcu_read_lock();
343 
344 	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
345 	if (!hinfo)
346 		goto out;
347 
348 	memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
349 	err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
350 
351 out:
352 	rcu_read_unlock();
353 	return err;
354 }
355 EXPORT_SYMBOL(seg6_push_hmac);
356 
357 static int seg6_hmac_init_algo(void)
358 {
359 	struct seg6_hmac_algo *algo;
360 	struct crypto_shash *tfm;
361 	struct shash_desc *shash;
362 	int i, alg_count, cpu;
363 
364 	alg_count = ARRAY_SIZE(hmac_algos);
365 
366 	for (i = 0; i < alg_count; i++) {
367 		struct crypto_shash **p_tfm;
368 		int shsize;
369 
370 		algo = &hmac_algos[i];
371 		algo->tfms = alloc_percpu(struct crypto_shash *);
372 		if (!algo->tfms)
373 			return -ENOMEM;
374 
375 		for_each_possible_cpu(cpu) {
376 			tfm = crypto_alloc_shash(algo->name, 0, GFP_KERNEL);
377 			if (IS_ERR(tfm))
378 				return PTR_ERR(tfm);
379 			p_tfm = per_cpu_ptr(algo->tfms, cpu);
380 			*p_tfm = tfm;
381 		}
382 
383 		p_tfm = raw_cpu_ptr(algo->tfms);
384 		tfm = *p_tfm;
385 
386 		shsize = sizeof(*shash) + crypto_shash_descsize(tfm);
387 
388 		algo->shashs = alloc_percpu(struct shash_desc *);
389 		if (!algo->shashs)
390 			return -ENOMEM;
391 
392 		for_each_possible_cpu(cpu) {
393 			shash = kzalloc_node(shsize, GFP_KERNEL,
394 					     cpu_to_node(cpu));
395 			if (!shash)
396 				return -ENOMEM;
397 			*per_cpu_ptr(algo->shashs, cpu) = shash;
398 		}
399 	}
400 
401 	return 0;
402 }
403 
404 int __init seg6_hmac_init(void)
405 {
406 	return seg6_hmac_init_algo();
407 }
408 EXPORT_SYMBOL(seg6_hmac_init);
409 
410 int __net_init seg6_hmac_net_init(struct net *net)
411 {
412 	struct seg6_pernet_data *sdata = seg6_pernet(net);
413 
414 	rhashtable_init(&sdata->hmac_infos, &rht_params);
415 
416 	return 0;
417 }
418 EXPORT_SYMBOL(seg6_hmac_net_init);
419 
420 void seg6_hmac_exit(void)
421 {
422 	struct seg6_hmac_algo *algo = NULL;
423 	int i, alg_count, cpu;
424 
425 	alg_count = ARRAY_SIZE(hmac_algos);
426 	for (i = 0; i < alg_count; i++) {
427 		algo = &hmac_algos[i];
428 		for_each_possible_cpu(cpu) {
429 			struct crypto_shash *tfm;
430 			struct shash_desc *shash;
431 
432 			shash = *per_cpu_ptr(algo->shashs, cpu);
433 			kfree(shash);
434 			tfm = *per_cpu_ptr(algo->tfms, cpu);
435 			crypto_free_shash(tfm);
436 		}
437 		free_percpu(algo->tfms);
438 		free_percpu(algo->shashs);
439 	}
440 }
441 EXPORT_SYMBOL(seg6_hmac_exit);
442 
443 void __net_exit seg6_hmac_net_exit(struct net *net)
444 {
445 	struct seg6_pernet_data *sdata = seg6_pernet(net);
446 
447 	rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
448 }
449 EXPORT_SYMBOL(seg6_hmac_net_exit);
450