xref: /linux/net/ipv6/seg6_hmac.c (revision c532de5a67a70f8533d495f8f2aaa9a0491c3ad0) 
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 static DEFINE_PER_CPU(char [SEG6_HMAC_RING_SIZE], hmac_ring);
44 
45 static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
46 {
47 	const struct seg6_hmac_info *hinfo = obj;
48 
49 	return (hinfo->hmackeyid != *(__u32 *)arg->key);
50 }
51 
52 static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
53 {
54 	kfree_rcu(hinfo, rcu);
55 }
56 
57 static void seg6_free_hi(void *ptr, void *arg)
58 {
59 	struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;
60 
61 	if (hinfo)
62 		seg6_hinfo_release(hinfo);
63 }
64 
65 static const struct rhashtable_params rht_params = {
66 	.head_offset		= offsetof(struct seg6_hmac_info, node),
67 	.key_offset		= offsetof(struct seg6_hmac_info, hmackeyid),
68 	.key_len		= sizeof(u32),
69 	.automatic_shrinking	= true,
70 	.obj_cmpfn		= seg6_hmac_cmpfn,
71 };
72 
73 static struct seg6_hmac_algo hmac_algos[] = {
74 	{
75 		.alg_id = SEG6_HMAC_ALGO_SHA1,
76 		.name = "hmac(sha1)",
77 	},
78 	{
79 		.alg_id = SEG6_HMAC_ALGO_SHA256,
80 		.name = "hmac(sha256)",
81 	},
82 };
83 
84 static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
85 {
86 	struct sr6_tlv_hmac *tlv;
87 
88 	if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
89 		return NULL;
90 
91 	if (!sr_has_hmac(srh))
92 		return NULL;
93 
94 	tlv = (struct sr6_tlv_hmac *)
95 	      ((char *)srh + ((srh->hdrlen + 1) << 3) - 40);
96 
97 	if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
98 		return NULL;
99 
100 	return tlv;
101 }
102 
103 static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id)
104 {
105 	struct seg6_hmac_algo *algo;
106 	int i, alg_count;
107 
108 	alg_count = ARRAY_SIZE(hmac_algos);
109 	for (i = 0; i < alg_count; i++) {
110 		algo = &hmac_algos[i];
111 		if (algo->alg_id == alg_id)
112 			return algo;
113 	}
114 
115 	return NULL;
116 }
117 
118 static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize,
119 		     u8 *output, int outlen)
120 {
121 	struct seg6_hmac_algo *algo;
122 	struct crypto_shash *tfm;
123 	struct shash_desc *shash;
124 	int ret, dgsize;
125 
126 	algo = __hmac_get_algo(hinfo->alg_id);
127 	if (!algo)
128 		return -ENOENT;
129 
130 	tfm = *this_cpu_ptr(algo->tfms);
131 
132 	dgsize = crypto_shash_digestsize(tfm);
133 	if (dgsize > outlen) {
134 		pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n",
135 			 dgsize, outlen);
136 		return -ENOMEM;
137 	}
138 
139 	ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen);
140 	if (ret < 0) {
141 		pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret);
142 		goto failed;
143 	}
144 
145 	shash = *this_cpu_ptr(algo->shashs);
146 	shash->tfm = tfm;
147 
148 	ret = crypto_shash_digest(shash, text, psize, output);
149 	if (ret < 0) {
150 		pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret);
151 		goto failed;
152 	}
153 
154 	return dgsize;
155 
156 failed:
157 	return ret;
158 }
159 
160 int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
161 		      struct in6_addr *saddr, u8 *output)
162 {
163 	__be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
164 	u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE];
165 	int plen, i, dgsize, wrsize;
166 	char *ring, *off;
167 
168 	/* a 160-byte buffer for digest output allows to store highest known
169 	 * hash function (RadioGatun) with up to 1216 bits
170 	 */
171 
172 	/* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */
173 	plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;
174 
175 	/* this limit allows for 14 segments */
176 	if (plen >= SEG6_HMAC_RING_SIZE)
177 		return -EMSGSIZE;
178 
179 	/* Let's build the HMAC text on the ring buffer. The text is composed
180 	 * as follows, in order:
181 	 *
182 	 * 1. Source IPv6 address (128 bits)
183 	 * 2. first_segment value (8 bits)
184 	 * 3. Flags (8 bits)
185 	 * 4. HMAC Key ID (32 bits)
186 	 * 5. All segments in the segments list (n * 128 bits)
187 	 */
188 
189 	local_bh_disable();
190 	ring = this_cpu_ptr(hmac_ring);
191 	off = ring;
192 
193 	/* source address */
194 	memcpy(off, saddr, 16);
195 	off += 16;
196 
197 	/* first_segment value */
198 	*off++ = hdr->first_segment;
199 
200 	/* flags */
201 	*off++ = hdr->flags;
202 
203 	/* HMAC Key ID */
204 	memcpy(off, &hmackeyid, 4);
205 	off += 4;
206 
207 	/* all segments in the list */
208 	for (i = 0; i < hdr->first_segment + 1; i++) {
209 		memcpy(off, hdr->segments + i, 16);
210 		off += 16;
211 	}
212 
213 	dgsize = __do_hmac(hinfo, ring, plen, tmp_out,
214 			   SEG6_HMAC_MAX_DIGESTSIZE);
215 	local_bh_enable();
216 
217 	if (dgsize < 0)
218 		return dgsize;
219 
220 	wrsize = SEG6_HMAC_FIELD_LEN;
221 	if (wrsize > dgsize)
222 		wrsize = dgsize;
223 
224 	memset(output, 0, SEG6_HMAC_FIELD_LEN);
225 	memcpy(output, tmp_out, wrsize);
226 
227 	return 0;
228 }
229 EXPORT_SYMBOL(seg6_hmac_compute);
230 
231 /* checks if an incoming SR-enabled packet's HMAC status matches
232  * the incoming policy.
233  *
234  * called with rcu_read_lock()
235  */
236 bool seg6_hmac_validate_skb(struct sk_buff *skb)
237 {
238 	u8 hmac_output[SEG6_HMAC_FIELD_LEN];
239 	struct net *net = dev_net(skb->dev);
240 	struct seg6_hmac_info *hinfo;
241 	struct sr6_tlv_hmac *tlv;
242 	struct ipv6_sr_hdr *srh;
243 	struct inet6_dev *idev;
244 	int require_hmac;
245 
246 	idev = __in6_dev_get(skb->dev);
247 
248 	srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
249 
250 	tlv = seg6_get_tlv_hmac(srh);
251 
252 	require_hmac = READ_ONCE(idev->cnf.seg6_require_hmac);
253 	/* mandatory check but no tlv */
254 	if (require_hmac > 0 && !tlv)
255 		return false;
256 
257 	/* no check */
258 	if (require_hmac < 0)
259 		return true;
260 
261 	/* check only if present */
262 	if (require_hmac == 0 && !tlv)
263 		return true;
264 
265 	/* now, seg6_require_hmac >= 0 && tlv */
266 
267 	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
268 	if (!hinfo)
269 		return false;
270 
271 	if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
272 		return false;
273 
274 	if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
275 		return false;
276 
277 	return true;
278 }
279 EXPORT_SYMBOL(seg6_hmac_validate_skb);
280 
281 /* called with rcu_read_lock() */
282 struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
283 {
284 	struct seg6_pernet_data *sdata = seg6_pernet(net);
285 	struct seg6_hmac_info *hinfo;
286 
287 	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
288 
289 	return hinfo;
290 }
291 EXPORT_SYMBOL(seg6_hmac_info_lookup);
292 
293 int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
294 {
295 	struct seg6_pernet_data *sdata = seg6_pernet(net);
296 	int err;
297 
298 	err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
299 					    rht_params);
300 
301 	return err;
302 }
303 EXPORT_SYMBOL(seg6_hmac_info_add);
304 
305 int seg6_hmac_info_del(struct net *net, u32 key)
306 {
307 	struct seg6_pernet_data *sdata = seg6_pernet(net);
308 	struct seg6_hmac_info *hinfo;
309 	int err = -ENOENT;
310 
311 	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
312 	if (!hinfo)
313 		goto out;
314 
315 	err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
316 				     rht_params);
317 	if (err)
318 		goto out;
319 
320 	seg6_hinfo_release(hinfo);
321 
322 out:
323 	return err;
324 }
325 EXPORT_SYMBOL(seg6_hmac_info_del);
326 
327 int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
328 		   struct ipv6_sr_hdr *srh)
329 {
330 	struct seg6_hmac_info *hinfo;
331 	struct sr6_tlv_hmac *tlv;
332 	int err = -ENOENT;
333 
334 	tlv = seg6_get_tlv_hmac(srh);
335 	if (!tlv)
336 		return -EINVAL;
337 
338 	rcu_read_lock();
339 
340 	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
341 	if (!hinfo)
342 		goto out;
343 
344 	memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
345 	err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
346 
347 out:
348 	rcu_read_unlock();
349 	return err;
350 }
351 EXPORT_SYMBOL(seg6_push_hmac);
352 
353 static int seg6_hmac_init_algo(void)
354 {
355 	struct seg6_hmac_algo *algo;
356 	struct crypto_shash *tfm;
357 	struct shash_desc *shash;
358 	int i, alg_count, cpu;
359 	int ret = -ENOMEM;
360 
361 	alg_count = ARRAY_SIZE(hmac_algos);
362 
363 	for (i = 0; i < alg_count; i++) {
364 		struct crypto_shash **p_tfm;
365 		int shsize;
366 
367 		algo = &hmac_algos[i];
368 		algo->tfms = alloc_percpu(struct crypto_shash *);
369 		if (!algo->tfms)
370 			goto error_out;
371 
372 		for_each_possible_cpu(cpu) {
373 			tfm = crypto_alloc_shash(algo->name, 0, 0);
374 			if (IS_ERR(tfm)) {
375 				ret = PTR_ERR(tfm);
376 				goto error_out;
377 			}
378 			p_tfm = per_cpu_ptr(algo->tfms, cpu);
379 			*p_tfm = tfm;
380 		}
381 
382 		p_tfm = raw_cpu_ptr(algo->tfms);
383 		tfm = *p_tfm;
384 
385 		shsize = sizeof(*shash) + crypto_shash_descsize(tfm);
386 
387 		algo->shashs = alloc_percpu(struct shash_desc *);
388 		if (!algo->shashs)
389 			goto error_out;
390 
391 		for_each_possible_cpu(cpu) {
392 			shash = kzalloc_node(shsize, GFP_KERNEL,
393 					     cpu_to_node(cpu));
394 			if (!shash)
395 				goto error_out;
396 			*per_cpu_ptr(algo->shashs, cpu) = shash;
397 		}
398 	}
399 
400 	return 0;
401 
402 error_out:
403 	seg6_hmac_exit();
404 	return ret;
405 }
406 
407 int __init seg6_hmac_init(void)
408 {
409 	return seg6_hmac_init_algo();
410 }
411 
412 int __net_init seg6_hmac_net_init(struct net *net)
413 {
414 	struct seg6_pernet_data *sdata = seg6_pernet(net);
415 
416 	return rhashtable_init(&sdata->hmac_infos, &rht_params);
417 }
418 
419 void seg6_hmac_exit(void)
420 {
421 	struct seg6_hmac_algo *algo = NULL;
422 	struct crypto_shash *tfm;
423 	struct shash_desc *shash;
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 
430 		if (algo->shashs) {
431 			for_each_possible_cpu(cpu) {
432 				shash = *per_cpu_ptr(algo->shashs, cpu);
433 				kfree(shash);
434 			}
435 			free_percpu(algo->shashs);
436 		}
437 
438 		if (algo->tfms) {
439 			for_each_possible_cpu(cpu) {
440 				tfm = *per_cpu_ptr(algo->tfms, cpu);
441 				crypto_free_shash(tfm);
442 			}
443 			free_percpu(algo->tfms);
444 		}
445 	}
446 }
447 EXPORT_SYMBOL(seg6_hmac_exit);
448 
449 void __net_exit seg6_hmac_net_exit(struct net *net)
450 {
451 	struct seg6_pernet_data *sdata = seg6_pernet(net);
452 
453 	rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
454 }
455 EXPORT_SYMBOL(seg6_hmac_net_exit);
456