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
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