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/sha.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
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
53 static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
54 {
55 kfree_rcu(hinfo, rcu);
56 }
57
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
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
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
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
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 */
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
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 /* mandatory check but no tlv */
253 if (idev->cnf.seg6_require_hmac > 0 && !tlv)
254 return false;
255
256 /* no check */
257 if (idev->cnf.seg6_require_hmac < 0)
258 return true;
259
260 /* check only if present */
261 if (idev->cnf.seg6_require_hmac == 0 && !tlv)
262 return true;
263
264 /* now, seg6_require_hmac >= 0 && tlv */
265
266 hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
267 if (!hinfo)
268 return false;
269
270 if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
271 return false;
272
273 if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
274 return false;
275
276 return true;
277 }
278 EXPORT_SYMBOL(seg6_hmac_validate_skb);
279
280 /* called with rcu_read_lock() */
281 struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
282 {
283 struct seg6_pernet_data *sdata = seg6_pernet(net);
284 struct seg6_hmac_info *hinfo;
285
286 hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
287
288 return hinfo;
289 }
290 EXPORT_SYMBOL(seg6_hmac_info_lookup);
291
292 int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
293 {
294 struct seg6_pernet_data *sdata = seg6_pernet(net);
295 int err;
296
297 err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
298 rht_params);
299
300 return err;
301 }
302 EXPORT_SYMBOL(seg6_hmac_info_add);
303
304 int seg6_hmac_info_del(struct net *net, u32 key)
305 {
306 struct seg6_pernet_data *sdata = seg6_pernet(net);
307 struct seg6_hmac_info *hinfo;
308 int err = -ENOENT;
309
310 hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
311 if (!hinfo)
312 goto out;
313
314 err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
315 rht_params);
316 if (err)
317 goto out;
318
319 seg6_hinfo_release(hinfo);
320
321 out:
322 return err;
323 }
324 EXPORT_SYMBOL(seg6_hmac_info_del);
325
326 int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
327 struct ipv6_sr_hdr *srh)
328 {
329 struct seg6_hmac_info *hinfo;
330 struct sr6_tlv_hmac *tlv;
331 int err = -ENOENT;
332
333 tlv = seg6_get_tlv_hmac(srh);
334 if (!tlv)
335 return -EINVAL;
336
337 rcu_read_lock();
338
339 hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
340 if (!hinfo)
341 goto out;
342
343 memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
344 err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
345
346 out:
347 rcu_read_unlock();
348 return err;
349 }
350 EXPORT_SYMBOL(seg6_push_hmac);
351
352 static int seg6_hmac_init_algo(void)
353 {
354 struct seg6_hmac_algo *algo;
355 struct crypto_shash *tfm;
356 struct shash_desc *shash;
357 int i, alg_count, cpu;
358
359 alg_count = ARRAY_SIZE(hmac_algos);
360
361 for (i = 0; i < alg_count; i++) {
362 struct crypto_shash **p_tfm;
363 int shsize;
364
365 algo = &hmac_algos[i];
366 algo->tfms = alloc_percpu(struct crypto_shash *);
367 if (!algo->tfms)
368 return -ENOMEM;
369
370 for_each_possible_cpu(cpu) {
371 tfm = crypto_alloc_shash(algo->name, 0, 0);
372 if (IS_ERR(tfm))
373 return PTR_ERR(tfm);
374 p_tfm = per_cpu_ptr(algo->tfms, cpu);
375 *p_tfm = tfm;
376 }
377
378 p_tfm = raw_cpu_ptr(algo->tfms);
379 tfm = *p_tfm;
380
381 shsize = sizeof(*shash) + crypto_shash_descsize(tfm);
382
383 algo->shashs = alloc_percpu(struct shash_desc *);
384 if (!algo->shashs)
385 return -ENOMEM;
386
387 for_each_possible_cpu(cpu) {
388 shash = kzalloc_node(shsize, GFP_KERNEL,
389 cpu_to_node(cpu));
390 if (!shash)
391 return -ENOMEM;
392 *per_cpu_ptr(algo->shashs, cpu) = shash;
393 }
394 }
395
396 return 0;
397 }
398
399 int __init seg6_hmac_init(void)
400 {
401 return seg6_hmac_init_algo();
402 }
403 EXPORT_SYMBOL(seg6_hmac_init);
404
405 int __net_init seg6_hmac_net_init(struct net *net)
406 {
407 struct seg6_pernet_data *sdata = seg6_pernet(net);
408
409 rhashtable_init(&sdata->hmac_infos, &rht_params);
410
411 return 0;
412 }
413 EXPORT_SYMBOL(seg6_hmac_net_init);
414
415 void seg6_hmac_exit(void)
416 {
417 struct seg6_hmac_algo *algo = NULL;
418 int i, alg_count, cpu;
419
420 alg_count = ARRAY_SIZE(hmac_algos);
421 for (i = 0; i < alg_count; i++) {
422 algo = &hmac_algos[i];
423 for_each_possible_cpu(cpu) {
424 struct crypto_shash *tfm;
425 struct shash_desc *shash;
426
427 shash = *per_cpu_ptr(algo->shashs, cpu);
428 kfree(shash);
429 tfm = *per_cpu_ptr(algo->tfms, cpu);
430 crypto_free_shash(tfm);
431 }
432 free_percpu(algo->tfms);
433 free_percpu(algo->shashs);
434 }
435 }
436 EXPORT_SYMBOL(seg6_hmac_exit);
437
438 void __net_exit seg6_hmac_net_exit(struct net *net)
439 {
440 struct seg6_pernet_data *sdata = seg6_pernet(net);
441
442 rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
443 }
444 EXPORT_SYMBOL(seg6_hmac_net_exit);
445
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