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Linux/net/ipv6/seg6_hmac.c

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  1 /*
  2  *  SR-IPv6 implementation -- HMAC functions
  3  *
  4  *  Author:
  5  *  David Lebrun <david.lebrun@uclouvain.be>
  6  *
  7  *
  8  *  This program is free software; you can redistribute it and/or
  9  *      modify it under the terms of the GNU General Public License
 10  *      as published by the Free Software Foundation; either version
 11  *      2 of the License, or (at your option) any later version.
 12  */
 13 
 14 #include <linux/errno.h>
 15 #include <linux/types.h>
 16 #include <linux/socket.h>
 17 #include <linux/sockios.h>
 18 #include <linux/net.h>
 19 #include <linux/netdevice.h>
 20 #include <linux/in6.h>
 21 #include <linux/icmpv6.h>
 22 #include <linux/mroute6.h>
 23 #include <linux/slab.h>
 24 
 25 #include <linux/netfilter.h>
 26 #include <linux/netfilter_ipv6.h>
 27 
 28 #include <net/sock.h>
 29 #include <net/snmp.h>
 30 
 31 #include <net/ipv6.h>
 32 #include <net/protocol.h>
 33 #include <net/transp_v6.h>
 34 #include <net/rawv6.h>
 35 #include <net/ndisc.h>
 36 #include <net/ip6_route.h>
 37 #include <net/addrconf.h>
 38 #include <net/xfrm.h>
 39 
 40 #include <linux/cryptohash.h>
 41 #include <crypto/hash.h>
 42 #include <crypto/sha.h>
 43 #include <net/seg6.h>
 44 #include <net/genetlink.h>
 45 #include <net/seg6_hmac.h>
 46 #include <linux/random.h>
 47 
 48 static DEFINE_PER_CPU(char [SEG6_HMAC_RING_SIZE], hmac_ring);
 49 
 50 static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
 51 {
 52         const struct seg6_hmac_info *hinfo = obj;
 53 
 54         return (hinfo->hmackeyid != *(__u32 *)arg->key);
 55 }
 56 
 57 static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
 58 {
 59         kfree_rcu(hinfo, rcu);
 60 }
 61 
 62 static void seg6_free_hi(void *ptr, void *arg)
 63 {
 64         struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;
 65 
 66         if (hinfo)
 67                 seg6_hinfo_release(hinfo);
 68 }
 69 
 70 static const struct rhashtable_params rht_params = {
 71         .head_offset            = offsetof(struct seg6_hmac_info, node),
 72         .key_offset             = offsetof(struct seg6_hmac_info, hmackeyid),
 73         .key_len                = sizeof(u32),
 74         .automatic_shrinking    = true,
 75         .obj_cmpfn              = seg6_hmac_cmpfn,
 76 };
 77 
 78 static struct seg6_hmac_algo hmac_algos[] = {
 79         {
 80                 .alg_id = SEG6_HMAC_ALGO_SHA1,
 81                 .name = "hmac(sha1)",
 82         },
 83         {
 84                 .alg_id = SEG6_HMAC_ALGO_SHA256,
 85                 .name = "hmac(sha256)",
 86         },
 87 };
 88 
 89 static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
 90 {
 91         struct sr6_tlv_hmac *tlv;
 92 
 93         if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
 94                 return NULL;
 95 
 96         if (!sr_has_hmac(srh))
 97                 return NULL;
 98 
 99         tlv = (struct sr6_tlv_hmac *)
100               ((char *)srh + ((srh->hdrlen + 1) << 3) - 40);
101 
102         if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
103                 return NULL;
104 
105         return tlv;
106 }
107 
108 static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id)
109 {
110         struct seg6_hmac_algo *algo;
111         int i, alg_count;
112 
113         alg_count = sizeof(hmac_algos) / sizeof(struct seg6_hmac_algo);
114         for (i = 0; i < alg_count; i++) {
115                 algo = &hmac_algos[i];
116                 if (algo->alg_id == alg_id)
117                         return algo;
118         }
119 
120         return NULL;
121 }
122 
123 static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize,
124                      u8 *output, int outlen)
125 {
126         struct seg6_hmac_algo *algo;
127         struct crypto_shash *tfm;
128         struct shash_desc *shash;
129         int ret, dgsize;
130 
131         algo = __hmac_get_algo(hinfo->alg_id);
132         if (!algo)
133                 return -ENOENT;
134 
135         tfm = *this_cpu_ptr(algo->tfms);
136 
137         dgsize = crypto_shash_digestsize(tfm);
138         if (dgsize > outlen) {
139                 pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n",
140                          dgsize, outlen);
141                 return -ENOMEM;
142         }
143 
144         ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen);
145         if (ret < 0) {
146                 pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret);
147                 goto failed;
148         }
149 
150         shash = *this_cpu_ptr(algo->shashs);
151         shash->tfm = tfm;
152 
153         ret = crypto_shash_digest(shash, text, psize, output);
154         if (ret < 0) {
155                 pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret);
156                 goto failed;
157         }
158 
159         return dgsize;
160 
161 failed:
162         return ret;
163 }
164 
165 int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
166                       struct in6_addr *saddr, u8 *output)
167 {
168         __be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
169         u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE];
170         int plen, i, dgsize, wrsize;
171         char *ring, *off;
172 
173         /* a 160-byte buffer for digest output allows to store highest known
174          * hash function (RadioGatun) with up to 1216 bits
175          */
176 
177         /* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */
178         plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;
179 
180         /* this limit allows for 14 segments */
181         if (plen >= SEG6_HMAC_RING_SIZE)
182                 return -EMSGSIZE;
183 
184         /* Let's build the HMAC text on the ring buffer. The text is composed
185          * as follows, in order:
186          *
187          * 1. Source IPv6 address (128 bits)
188          * 2. first_segment value (8 bits)
189          * 3. Flags (8 bits)
190          * 4. HMAC Key ID (32 bits)
191          * 5. All segments in the segments list (n * 128 bits)
192          */
193 
194         local_bh_disable();
195         ring = this_cpu_ptr(hmac_ring);
196         off = ring;
197 
198         /* source address */
199         memcpy(off, saddr, 16);
200         off += 16;
201 
202         /* first_segment value */
203         *off++ = hdr->first_segment;
204 
205         /* flags */
206         *off++ = hdr->flags;
207 
208         /* HMAC Key ID */
209         memcpy(off, &hmackeyid, 4);
210         off += 4;
211 
212         /* all segments in the list */
213         for (i = 0; i < hdr->first_segment + 1; i++) {
214                 memcpy(off, hdr->segments + i, 16);
215                 off += 16;
216         }
217 
218         dgsize = __do_hmac(hinfo, ring, plen, tmp_out,
219                            SEG6_HMAC_MAX_DIGESTSIZE);
220         local_bh_enable();
221 
222         if (dgsize < 0)
223                 return dgsize;
224 
225         wrsize = SEG6_HMAC_FIELD_LEN;
226         if (wrsize > dgsize)
227                 wrsize = dgsize;
228 
229         memset(output, 0, SEG6_HMAC_FIELD_LEN);
230         memcpy(output, tmp_out, wrsize);
231 
232         return 0;
233 }
234 EXPORT_SYMBOL(seg6_hmac_compute);
235 
236 /* checks if an incoming SR-enabled packet's HMAC status matches
237  * the incoming policy.
238  *
239  * called with rcu_read_lock()
240  */
241 bool seg6_hmac_validate_skb(struct sk_buff *skb)
242 {
243         u8 hmac_output[SEG6_HMAC_FIELD_LEN];
244         struct net *net = dev_net(skb->dev);
245         struct seg6_hmac_info *hinfo;
246         struct sr6_tlv_hmac *tlv;
247         struct ipv6_sr_hdr *srh;
248         struct inet6_dev *idev;
249 
250         idev = __in6_dev_get(skb->dev);
251 
252         srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
253 
254         tlv = seg6_get_tlv_hmac(srh);
255 
256         /* mandatory check but no tlv */
257         if (idev->cnf.seg6_require_hmac > 0 && !tlv)
258                 return false;
259 
260         /* no check */
261         if (idev->cnf.seg6_require_hmac < 0)
262                 return true;
263 
264         /* check only if present */
265         if (idev->cnf.seg6_require_hmac == 0 && !tlv)
266                 return true;
267 
268         /* now, seg6_require_hmac >= 0 && tlv */
269 
270         hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
271         if (!hinfo)
272                 return false;
273 
274         if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
275                 return false;
276 
277         if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
278                 return false;
279 
280         return true;
281 }
282 EXPORT_SYMBOL(seg6_hmac_validate_skb);
283 
284 /* called with rcu_read_lock() */
285 struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
286 {
287         struct seg6_pernet_data *sdata = seg6_pernet(net);
288         struct seg6_hmac_info *hinfo;
289 
290         hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
291 
292         return hinfo;
293 }
294 EXPORT_SYMBOL(seg6_hmac_info_lookup);
295 
296 int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
297 {
298         struct seg6_pernet_data *sdata = seg6_pernet(net);
299         int err;
300 
301         err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
302                                             rht_params);
303 
304         return err;
305 }
306 EXPORT_SYMBOL(seg6_hmac_info_add);
307 
308 int seg6_hmac_info_del(struct net *net, u32 key)
309 {
310         struct seg6_pernet_data *sdata = seg6_pernet(net);
311         struct seg6_hmac_info *hinfo;
312         int err = -ENOENT;
313 
314         hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
315         if (!hinfo)
316                 goto out;
317 
318         err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
319                                      rht_params);
320         if (err)
321                 goto out;
322 
323         seg6_hinfo_release(hinfo);
324 
325 out:
326         return err;
327 }
328 EXPORT_SYMBOL(seg6_hmac_info_del);
329 
330 int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
331                    struct ipv6_sr_hdr *srh)
332 {
333         struct seg6_hmac_info *hinfo;
334         struct sr6_tlv_hmac *tlv;
335         int err = -ENOENT;
336 
337         tlv = seg6_get_tlv_hmac(srh);
338         if (!tlv)
339                 return -EINVAL;
340 
341         rcu_read_lock();
342 
343         hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
344         if (!hinfo)
345                 goto out;
346 
347         memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
348         err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
349 
350 out:
351         rcu_read_unlock();
352         return err;
353 }
354 EXPORT_SYMBOL(seg6_push_hmac);
355 
356 static int seg6_hmac_init_algo(void)
357 {
358         struct seg6_hmac_algo *algo;
359         struct crypto_shash *tfm;
360         struct shash_desc *shash;
361         int i, alg_count, cpu;
362 
363         alg_count = sizeof(hmac_algos) / sizeof(struct seg6_hmac_algo);
364 
365         for (i = 0; i < alg_count; i++) {
366                 struct crypto_shash **p_tfm;
367                 int shsize;
368 
369                 algo = &hmac_algos[i];
370                 algo->tfms = alloc_percpu(struct crypto_shash *);
371                 if (!algo->tfms)
372                         return -ENOMEM;
373 
374                 for_each_possible_cpu(cpu) {
375                         tfm = crypto_alloc_shash(algo->name, 0, GFP_KERNEL);
376                         if (IS_ERR(tfm))
377                                 return PTR_ERR(tfm);
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                         return -ENOMEM;
390 
391                 for_each_possible_cpu(cpu) {
392                         shash = kzalloc_node(shsize, GFP_KERNEL,
393                                              cpu_to_node(cpu));
394                         if (!shash)
395                                 return -ENOMEM;
396                         *per_cpu_ptr(algo->shashs, cpu) = shash;
397                 }
398         }
399 
400         return 0;
401 }
402 
403 int __init seg6_hmac_init(void)
404 {
405         return seg6_hmac_init_algo();
406 }
407 EXPORT_SYMBOL(seg6_hmac_init);
408 
409 int __net_init seg6_hmac_net_init(struct net *net)
410 {
411         struct seg6_pernet_data *sdata = seg6_pernet(net);
412 
413         rhashtable_init(&sdata->hmac_infos, &rht_params);
414 
415         return 0;
416 }
417 EXPORT_SYMBOL(seg6_hmac_net_init);
418 
419 void seg6_hmac_exit(void)
420 {
421         struct seg6_hmac_algo *algo = NULL;
422         int i, alg_count, cpu;
423 
424         alg_count = sizeof(hmac_algos) / sizeof(struct seg6_hmac_algo);
425         for (i = 0; i < alg_count; i++) {
426                 algo = &hmac_algos[i];
427                 for_each_possible_cpu(cpu) {
428                         struct crypto_shash *tfm;
429                         struct shash_desc *shash;
430 
431                         shash = *per_cpu_ptr(algo->shashs, cpu);
432                         kfree(shash);
433                         tfm = *per_cpu_ptr(algo->tfms, cpu);
434                         crypto_free_shash(tfm);
435                 }
436                 free_percpu(algo->tfms);
437                 free_percpu(algo->shashs);
438         }
439 }
440 EXPORT_SYMBOL(seg6_hmac_exit);
441 
442 void __net_exit seg6_hmac_net_exit(struct net *net)
443 {
444         struct seg6_pernet_data *sdata = seg6_pernet(net);
445 
446         rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
447 }
448 EXPORT_SYMBOL(seg6_hmac_net_exit);
449 

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