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 <crypto/utils.h>
39 #include <net/seg6.h>
40 #include <net/genetlink.h>
41 #include <net/seg6_hmac.h>
42 #include <linux/random.h>
43
44 static DEFINE_PER_CPU(char [SEG6_HMAC_RING_SIZE], hmac_ring);
45
seg6_hmac_cmpfn(struct rhashtable_compare_arg * arg,const void * obj)46 static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
47 {
48 const struct seg6_hmac_info *hinfo = obj;
49
50 return (hinfo->hmackeyid != *(__u32 *)arg->key);
51 }
52
seg6_hinfo_release(struct seg6_hmac_info * hinfo)53 static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
54 {
55 kfree_rcu(hinfo, rcu);
56 }
57
seg6_free_hi(void * ptr,void * arg)58 static void seg6_free_hi(void *ptr, void *arg)
59 {
60 struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;
61
62 if (hinfo)
63 seg6_hinfo_release(hinfo);
64 }
65
66 static const struct rhashtable_params rht_params = {
67 .head_offset = offsetof(struct seg6_hmac_info, node),
68 .key_offset = offsetof(struct seg6_hmac_info, hmackeyid),
69 .key_len = sizeof(u32),
70 .automatic_shrinking = true,
71 .obj_cmpfn = seg6_hmac_cmpfn,
72 };
73
74 static struct seg6_hmac_algo hmac_algos[] = {
75 {
76 .alg_id = SEG6_HMAC_ALGO_SHA1,
77 .name = "hmac(sha1)",
78 },
79 {
80 .alg_id = SEG6_HMAC_ALGO_SHA256,
81 .name = "hmac(sha256)",
82 },
83 };
84
seg6_get_tlv_hmac(struct ipv6_sr_hdr * srh)85 static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
86 {
87 struct sr6_tlv_hmac *tlv;
88
89 if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
90 return NULL;
91
92 if (!sr_has_hmac(srh))
93 return NULL;
94
95 tlv = (struct sr6_tlv_hmac *)
96 ((char *)srh + ((srh->hdrlen + 1) << 3) - 40);
97
98 if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
99 return NULL;
100
101 return tlv;
102 }
103
__hmac_get_algo(u8 alg_id)104 static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id)
105 {
106 struct seg6_hmac_algo *algo;
107 int i, alg_count;
108
109 alg_count = ARRAY_SIZE(hmac_algos);
110 for (i = 0; i < alg_count; i++) {
111 algo = &hmac_algos[i];
112 if (algo->alg_id == alg_id)
113 return algo;
114 }
115
116 return NULL;
117 }
118
__do_hmac(struct seg6_hmac_info * hinfo,const char * text,u8 psize,u8 * output,int outlen)119 static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize,
120 u8 *output, int outlen)
121 {
122 struct seg6_hmac_algo *algo;
123 struct crypto_shash *tfm;
124 struct shash_desc *shash;
125 int ret, dgsize;
126
127 algo = __hmac_get_algo(hinfo->alg_id);
128 if (!algo)
129 return -ENOENT;
130
131 tfm = *this_cpu_ptr(algo->tfms);
132
133 dgsize = crypto_shash_digestsize(tfm);
134 if (dgsize > outlen) {
135 pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n",
136 dgsize, outlen);
137 return -ENOMEM;
138 }
139
140 ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen);
141 if (ret < 0) {
142 pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret);
143 goto failed;
144 }
145
146 shash = *this_cpu_ptr(algo->shashs);
147 shash->tfm = tfm;
148
149 ret = crypto_shash_digest(shash, text, psize, output);
150 if (ret < 0) {
151 pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret);
152 goto failed;
153 }
154
155 return dgsize;
156
157 failed:
158 return ret;
159 }
160
seg6_hmac_compute(struct seg6_hmac_info * hinfo,struct ipv6_sr_hdr * hdr,struct in6_addr * saddr,u8 * output)161 int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
162 struct in6_addr *saddr, u8 *output)
163 {
164 __be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
165 u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE];
166 int plen, i, dgsize, wrsize;
167 char *ring, *off;
168
169 /* a 160-byte buffer for digest output allows to store highest known
170 * hash function (RadioGatun) with up to 1216 bits
171 */
172
173 /* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */
174 plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;
175
176 /* this limit allows for 14 segments */
177 if (plen >= SEG6_HMAC_RING_SIZE)
178 return -EMSGSIZE;
179
180 /* Let's build the HMAC text on the ring buffer. The text is composed
181 * as follows, in order:
182 *
183 * 1. Source IPv6 address (128 bits)
184 * 2. first_segment value (8 bits)
185 * 3. Flags (8 bits)
186 * 4. HMAC Key ID (32 bits)
187 * 5. All segments in the segments list (n * 128 bits)
188 */
189
190 local_bh_disable();
191 ring = this_cpu_ptr(hmac_ring);
192 off = ring;
193
194 /* source address */
195 memcpy(off, saddr, 16);
196 off += 16;
197
198 /* first_segment value */
199 *off++ = hdr->first_segment;
200
201 /* flags */
202 *off++ = hdr->flags;
203
204 /* HMAC Key ID */
205 memcpy(off, &hmackeyid, 4);
206 off += 4;
207
208 /* all segments in the list */
209 for (i = 0; i < hdr->first_segment + 1; i++) {
210 memcpy(off, hdr->segments + i, 16);
211 off += 16;
212 }
213
214 dgsize = __do_hmac(hinfo, ring, plen, tmp_out,
215 SEG6_HMAC_MAX_DIGESTSIZE);
216 local_bh_enable();
217
218 if (dgsize < 0)
219 return dgsize;
220
221 wrsize = SEG6_HMAC_FIELD_LEN;
222 if (wrsize > dgsize)
223 wrsize = dgsize;
224
225 memset(output, 0, SEG6_HMAC_FIELD_LEN);
226 memcpy(output, tmp_out, wrsize);
227
228 return 0;
229 }
230 EXPORT_SYMBOL(seg6_hmac_compute);
231
232 /* checks if an incoming SR-enabled packet's HMAC status matches
233 * the incoming policy.
234 *
235 * called with rcu_read_lock()
236 */
seg6_hmac_validate_skb(struct sk_buff * skb)237 bool seg6_hmac_validate_skb(struct sk_buff *skb)
238 {
239 u8 hmac_output[SEG6_HMAC_FIELD_LEN];
240 struct net *net = dev_net(skb->dev);
241 struct seg6_hmac_info *hinfo;
242 struct sr6_tlv_hmac *tlv;
243 struct ipv6_sr_hdr *srh;
244 struct inet6_dev *idev;
245 int require_hmac;
246
247 idev = __in6_dev_get(skb->dev);
248
249 srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
250
251 tlv = seg6_get_tlv_hmac(srh);
252
253 require_hmac = READ_ONCE(idev->cnf.seg6_require_hmac);
254 /* mandatory check but no tlv */
255 if (require_hmac > 0 && !tlv)
256 return false;
257
258 /* no check */
259 if (require_hmac < 0)
260 return true;
261
262 /* check only if present */
263 if (require_hmac == 0 && !tlv)
264 return true;
265
266 /* now, seg6_require_hmac >= 0 && tlv */
267
268 hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
269 if (!hinfo)
270 return false;
271
272 if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
273 return false;
274
275 if (crypto_memneq(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN))
276 return false;
277
278 return true;
279 }
280 EXPORT_SYMBOL(seg6_hmac_validate_skb);
281
282 /* called with rcu_read_lock() */
seg6_hmac_info_lookup(struct net * net,u32 key)283 struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
284 {
285 struct seg6_pernet_data *sdata = seg6_pernet(net);
286 struct seg6_hmac_info *hinfo;
287
288 hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
289
290 return hinfo;
291 }
292 EXPORT_SYMBOL(seg6_hmac_info_lookup);
293
seg6_hmac_info_add(struct net * net,u32 key,struct seg6_hmac_info * hinfo)294 int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
295 {
296 struct seg6_pernet_data *sdata = seg6_pernet(net);
297 int err;
298
299 if (!__hmac_get_algo(hinfo->alg_id))
300 return -EINVAL;
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
seg6_hmac_info_del(struct net * net,u32 key)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
seg6_push_hmac(struct net * net,struct in6_addr * saddr,struct ipv6_sr_hdr * srh)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
seg6_hmac_init_algo(void)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 int ret = -ENOMEM;
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 goto error_out;
375
376 for_each_possible_cpu(cpu) {
377 tfm = crypto_alloc_shash(algo->name, 0, 0);
378 if (IS_ERR(tfm)) {
379 ret = PTR_ERR(tfm);
380 goto error_out;
381 }
382 p_tfm = per_cpu_ptr(algo->tfms, cpu);
383 *p_tfm = tfm;
384 }
385
386 p_tfm = raw_cpu_ptr(algo->tfms);
387 tfm = *p_tfm;
388
389 shsize = sizeof(*shash) + crypto_shash_descsize(tfm);
390
391 algo->shashs = alloc_percpu(struct shash_desc *);
392 if (!algo->shashs)
393 goto error_out;
394
395 for_each_possible_cpu(cpu) {
396 shash = kzalloc_node(shsize, GFP_KERNEL,
397 cpu_to_node(cpu));
398 if (!shash)
399 goto error_out;
400 *per_cpu_ptr(algo->shashs, cpu) = shash;
401 }
402 }
403
404 return 0;
405
406 error_out:
407 seg6_hmac_exit();
408 return ret;
409 }
410
seg6_hmac_init(void)411 int __init seg6_hmac_init(void)
412 {
413 return seg6_hmac_init_algo();
414 }
415
seg6_hmac_net_init(struct net * net)416 int __net_init seg6_hmac_net_init(struct net *net)
417 {
418 struct seg6_pernet_data *sdata = seg6_pernet(net);
419
420 return rhashtable_init(&sdata->hmac_infos, &rht_params);
421 }
422
seg6_hmac_exit(void)423 void seg6_hmac_exit(void)
424 {
425 struct seg6_hmac_algo *algo = NULL;
426 struct crypto_shash *tfm;
427 struct shash_desc *shash;
428 int i, alg_count, cpu;
429
430 alg_count = ARRAY_SIZE(hmac_algos);
431 for (i = 0; i < alg_count; i++) {
432 algo = &hmac_algos[i];
433
434 if (algo->shashs) {
435 for_each_possible_cpu(cpu) {
436 shash = *per_cpu_ptr(algo->shashs, cpu);
437 kfree(shash);
438 }
439 free_percpu(algo->shashs);
440 }
441
442 if (algo->tfms) {
443 for_each_possible_cpu(cpu) {
444 tfm = *per_cpu_ptr(algo->tfms, cpu);
445 crypto_free_shash(tfm);
446 }
447 free_percpu(algo->tfms);
448 }
449 }
450 }
451 EXPORT_SYMBOL(seg6_hmac_exit);
452
seg6_hmac_net_exit(struct net * net)453 void __net_exit seg6_hmac_net_exit(struct net *net)
454 {
455 struct seg6_pernet_data *sdata = seg6_pernet(net);
456
457 rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
458 }
459 EXPORT_SYMBOL(seg6_hmac_net_exit);
460