xref: /openbmc/linux/net/ipv6/seg6_hmac.c (revision 2f190ac2) 
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 
245 	idev = __in6_dev_get(skb->dev);
246 
247 	srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
248 
249 	tlv = seg6_get_tlv_hmac(srh);
250 
251 	/* mandatory check but no tlv */
252 	if (idev->cnf.seg6_require_hmac > 0 && !tlv)
253 		return false;
254 
255 	/* no check */
256 	if (idev->cnf.seg6_require_hmac < 0)
257 		return true;
258 
259 	/* check only if present */
260 	if (idev->cnf.seg6_require_hmac == 0 && !tlv)
261 		return true;
262 
263 	/* now, seg6_require_hmac >= 0 && tlv */
264 
265 	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
266 	if (!hinfo)
267 		return false;
268 
269 	if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
270 		return false;
271 
272 	if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
273 		return false;
274 
275 	return true;
276 }
277 EXPORT_SYMBOL(seg6_hmac_validate_skb);
278 
279 /* called with rcu_read_lock() */
280 struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
281 {
282 	struct seg6_pernet_data *sdata = seg6_pernet(net);
283 	struct seg6_hmac_info *hinfo;
284 
285 	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
286 
287 	return hinfo;
288 }
289 EXPORT_SYMBOL(seg6_hmac_info_lookup);
290 
291 int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
292 {
293 	struct seg6_pernet_data *sdata = seg6_pernet(net);
294 	int err;
295 
296 	err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
297 					    rht_params);
298 
299 	return err;
300 }
301 EXPORT_SYMBOL(seg6_hmac_info_add);
302 
303 int seg6_hmac_info_del(struct net *net, u32 key)
304 {
305 	struct seg6_pernet_data *sdata = seg6_pernet(net);
306 	struct seg6_hmac_info *hinfo;
307 	int err = -ENOENT;
308 
309 	hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
310 	if (!hinfo)
311 		goto out;
312 
313 	err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
314 				     rht_params);
315 	if (err)
316 		goto out;
317 
318 	seg6_hinfo_release(hinfo);
319 
320 out:
321 	return err;
322 }
323 EXPORT_SYMBOL(seg6_hmac_info_del);
324 
325 int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
326 		   struct ipv6_sr_hdr *srh)
327 {
328 	struct seg6_hmac_info *hinfo;
329 	struct sr6_tlv_hmac *tlv;
330 	int err = -ENOENT;
331 
332 	tlv = seg6_get_tlv_hmac(srh);
333 	if (!tlv)
334 		return -EINVAL;
335 
336 	rcu_read_lock();
337 
338 	hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
339 	if (!hinfo)
340 		goto out;
341 
342 	memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
343 	err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
344 
345 out:
346 	rcu_read_unlock();
347 	return err;
348 }
349 EXPORT_SYMBOL(seg6_push_hmac);
350 
351 static int seg6_hmac_init_algo(void)
352 {
353 	struct seg6_hmac_algo *algo;
354 	struct crypto_shash *tfm;
355 	struct shash_desc *shash;
356 	int i, alg_count, cpu;
357 
358 	alg_count = ARRAY_SIZE(hmac_algos);
359 
360 	for (i = 0; i < alg_count; i++) {
361 		struct crypto_shash **p_tfm;
362 		int shsize;
363 
364 		algo = &hmac_algos[i];
365 		algo->tfms = alloc_percpu(struct crypto_shash *);
366 		if (!algo->tfms)
367 			return -ENOMEM;
368 
369 		for_each_possible_cpu(cpu) {
370 			tfm = crypto_alloc_shash(algo->name, 0, 0);
371 			if (IS_ERR(tfm))
372 				return PTR_ERR(tfm);
373 			p_tfm = per_cpu_ptr(algo->tfms, cpu);
374 			*p_tfm = tfm;
375 		}
376 
377 		p_tfm = raw_cpu_ptr(algo->tfms);
378 		tfm = *p_tfm;
379 
380 		shsize = sizeof(*shash) + crypto_shash_descsize(tfm);
381 
382 		algo->shashs = alloc_percpu(struct shash_desc *);
383 		if (!algo->shashs)
384 			return -ENOMEM;
385 
386 		for_each_possible_cpu(cpu) {
387 			shash = kzalloc_node(shsize, GFP_KERNEL,
388 					     cpu_to_node(cpu));
389 			if (!shash)
390 				return -ENOMEM;
391 			*per_cpu_ptr(algo->shashs, cpu) = shash;
392 		}
393 	}
394 
395 	return 0;
396 }
397 
398 int __init seg6_hmac_init(void)
399 {
400 	return seg6_hmac_init_algo();
401 }
402 
403 int __net_init seg6_hmac_net_init(struct net *net)
404 {
405 	struct seg6_pernet_data *sdata = seg6_pernet(net);
406 
407 	return rhashtable_init(&sdata->hmac_infos, &rht_params);
408 }
409 
410 void seg6_hmac_exit(void)
411 {
412 	struct seg6_hmac_algo *algo = NULL;
413 	int i, alg_count, cpu;
414 
415 	alg_count = ARRAY_SIZE(hmac_algos);
416 	for (i = 0; i < alg_count; i++) {
417 		algo = &hmac_algos[i];
418 		for_each_possible_cpu(cpu) {
419 			struct crypto_shash *tfm;
420 			struct shash_desc *shash;
421 
422 			shash = *per_cpu_ptr(algo->shashs, cpu);
423 			kfree(shash);
424 			tfm = *per_cpu_ptr(algo->tfms, cpu);
425 			crypto_free_shash(tfm);
426 		}
427 		free_percpu(algo->tfms);
428 		free_percpu(algo->shashs);
429 	}
430 }
431 EXPORT_SYMBOL(seg6_hmac_exit);
432 
433 void __net_exit seg6_hmac_net_exit(struct net *net)
434 {
435 	struct seg6_pernet_data *sdata = seg6_pernet(net);
436 
437 	rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
438 }
439 EXPORT_SYMBOL(seg6_hmac_net_exit);
440