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Linux/net/ipv6/seg6_hmac.c

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  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 EXPORT_SYMBOL(seg6_hmac_init);
403 
404 int __net_init seg6_hmac_net_init(struct net *net)
405 {
406         struct seg6_pernet_data *sdata = seg6_pernet(net);
407 
408         rhashtable_init(&sdata->hmac_infos, &rht_params);
409 
410         return 0;
411 }
412 EXPORT_SYMBOL(seg6_hmac_net_init);
413 
414 void seg6_hmac_exit(void)
415 {
416         struct seg6_hmac_algo *algo = NULL;
417         int i, alg_count, cpu;
418 
419         alg_count = ARRAY_SIZE(hmac_algos);
420         for (i = 0; i < alg_count; i++) {
421                 algo = &hmac_algos[i];
422                 for_each_possible_cpu(cpu) {
423                         struct crypto_shash *tfm;
424                         struct shash_desc *shash;
425 
426                         shash = *per_cpu_ptr(algo->shashs, cpu);
427                         kfree(shash);
428                         tfm = *per_cpu_ptr(algo->tfms, cpu);
429                         crypto_free_shash(tfm);
430                 }
431                 free_percpu(algo->tfms);
432                 free_percpu(algo->shashs);
433         }
434 }
435 EXPORT_SYMBOL(seg6_hmac_exit);
436 
437 void __net_exit seg6_hmac_net_exit(struct net *net)
438 {
439         struct seg6_pernet_data *sdata = seg6_pernet(net);
440 
441         rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
442 }
443 EXPORT_SYMBOL(seg6_hmac_net_exit);
444 

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