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
43static DEFINE_PER_CPU(char [SEG6_HMAC_RING_SIZE], hmac_ring);
44
45static 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
52static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
53{
54 kfree_rcu(hinfo, rcu);
55}
56
57static 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
65static 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
73static 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
84static 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
103static 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
118static 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(alg_id: 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, key: hinfo->secret, keylen: 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(desc: shash, data: text, len: psize, out: 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
156failed:
157 return ret;
158}
159
160int 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, text: ring, psize: plen, output: 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}
229EXPORT_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 */
236bool seg6_hmac_validate_skb(struct sk_buff *skb)
237{
238 u8 hmac_output[SEG6_HMAC_FIELD_LEN];
239 struct net *net = dev_net(dev: 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(dev: 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(p: hmac_output, q: tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
273 return false;
274
275 return true;
276}
277EXPORT_SYMBOL(seg6_hmac_validate_skb);
278
279/* called with rcu_read_lock() */
280struct 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(ht: &sdata->hmac_infos, key: &key, params: rht_params);
286
287 return hinfo;
288}
289EXPORT_SYMBOL(seg6_hmac_info_lookup);
290
291int 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(ht: &sdata->hmac_infos, obj: &hinfo->node,
297 params: rht_params);
298
299 return err;
300}
301EXPORT_SYMBOL(seg6_hmac_info_add);
302
303int 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(ht: &sdata->hmac_infos, key: &key, params: rht_params);
310 if (!hinfo)
311 goto out;
312
313 err = rhashtable_remove_fast(ht: &sdata->hmac_infos, obj: &hinfo->node,
314 params: rht_params);
315 if (err)
316 goto out;
317
318 seg6_hinfo_release(hinfo);
319
320out:
321 return err;
322}
323EXPORT_SYMBOL(seg6_hmac_info_del);
324
325int 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
345out:
346 rcu_read_unlock();
347 return err;
348}
349EXPORT_SYMBOL(seg6_push_hmac);
350
351static 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(alg_name: algo->name, type: 0, mask: 0);
371 if (IS_ERR(ptr: tfm))
372 return PTR_ERR(ptr: 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(size: 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
398int __init seg6_hmac_init(void)
399{
400 return seg6_hmac_init_algo();
401}
402
403int __net_init seg6_hmac_net_init(struct net *net)
404{
405 struct seg6_pernet_data *sdata = seg6_pernet(net);
406
407 return rhashtable_init(ht: &sdata->hmac_infos, params: &rht_params);
408}
409
410void 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(objp: shash);
424 tfm = *per_cpu_ptr(algo->tfms, cpu);
425 crypto_free_shash(tfm);
426 }
427 free_percpu(pdata: algo->tfms);
428 free_percpu(pdata: algo->shashs);
429 }
430}
431EXPORT_SYMBOL(seg6_hmac_exit);
432
433void __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(ht: &sdata->hmac_infos, free_fn: seg6_free_hi, NULL);
438}
439EXPORT_SYMBOL(seg6_hmac_net_exit);
440

source code of linux/net/ipv6/seg6_hmac.c