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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 <linux/cryptohash.h>
 38 #include <crypto/hash.h>
 39 #include <crypto/sha.h>
 40 #include <net/seg6.h>
 41 #include <net/genetlink.h>
 42 #include <net/seg6_hmac.h>
 43 #include <linux/random.h>
 44 
 45 static DEFINE_PER_CPU(char [SEG6_HMAC_RING_SIZE], hmac_ring);
 46 
 47 static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
 48 {
 49         const struct seg6_hmac_info *hinfo = obj;
 50 
 51         return (hinfo->hmackeyid != *(__u32 *)arg->key);
 52 }
 53 
 54 static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
 55 {
 56         kfree_rcu(hinfo, rcu);
 57 }
 58 
 59 static void seg6_free_hi(void *ptr, void *arg)
 60 {
 61         struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;
 62 
 63         if (hinfo)
 64                 seg6_hinfo_release(hinfo);
 65 }
 66 
 67 static const struct rhashtable_params rht_params = {
 68         .head_offset            = offsetof(struct seg6_hmac_info, node),
 69         .key_offset             = offsetof(struct seg6_hmac_info, hmackeyid),
 70         .key_len                = sizeof(u32),
 71         .automatic_shrinking    = true,
 72         .obj_cmpfn              = seg6_hmac_cmpfn,
 73 };
 74 
 75 static struct seg6_hmac_algo hmac_algos[] = {
 76         {
 77                 .alg_id = SEG6_HMAC_ALGO_SHA1,
 78                 .name = "hmac(sha1)",
 79         },
 80         {
 81                 .alg_id = SEG6_HMAC_ALGO_SHA256,
 82                 .name = "hmac(sha256)",
 83         },
 84 };
 85 
 86 static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
 87 {
 88         struct sr6_tlv_hmac *tlv;
 89 
 90         if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
 91                 return NULL;
 92 
 93         if (!sr_has_hmac(srh))
 94                 return NULL;
 95 
 96         tlv = (struct sr6_tlv_hmac *)
 97               ((char *)srh + ((srh->hdrlen + 1) << 3) - 40);
 98 
 99         if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
100                 return NULL;
101 
102         return tlv;
103 }
104 
105 static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id)
106 {
107         struct seg6_hmac_algo *algo;
108         int i, alg_count;
109 
110         alg_count = ARRAY_SIZE(hmac_algos);
111         for (i = 0; i < alg_count; i++) {
112                 algo = &hmac_algos[i];
113                 if (algo->alg_id == alg_id)
114                         return algo;
115         }
116 
117         return NULL;
118 }
119 
120 static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize,
121                      u8 *output, int outlen)
122 {
123         struct seg6_hmac_algo *algo;
124         struct crypto_shash *tfm;
125         struct shash_desc *shash;
126         int ret, dgsize;
127 
128         algo = __hmac_get_algo(hinfo->alg_id);
129         if (!algo)
130                 return -ENOENT;
131 
132         tfm = *this_cpu_ptr(algo->tfms);
133 
134         dgsize = crypto_shash_digestsize(tfm);
135         if (dgsize > outlen) {
136                 pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n",
137                          dgsize, outlen);
138                 return -ENOMEM;
139         }
140 
141         ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen);
142         if (ret < 0) {
143                 pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret);
144                 goto failed;
145         }
146 
147         shash = *this_cpu_ptr(algo->shashs);
148         shash->tfm = tfm;
149 
150         ret = crypto_shash_digest(shash, text, psize, output);
151         if (ret < 0) {
152                 pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret);
153                 goto failed;
154         }
155 
156         return dgsize;
157 
158 failed:
159         return ret;
160 }
161 
162 int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
163                       struct in6_addr *saddr, u8 *output)
164 {
165         __be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
166         u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE];
167         int plen, i, dgsize, wrsize;
168         char *ring, *off;
169 
170         /* a 160-byte buffer for digest output allows to store highest known
171          * hash function (RadioGatun) with up to 1216 bits
172          */
173 
174         /* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */
175         plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;
176 
177         /* this limit allows for 14 segments */
178         if (plen >= SEG6_HMAC_RING_SIZE)
179                 return -EMSGSIZE;
180 
181         /* Let's build the HMAC text on the ring buffer. The text is composed
182          * as follows, in order:
183          *
184          * 1. Source IPv6 address (128 bits)
185          * 2. first_segment value (8 bits)
186          * 3. Flags (8 bits)
187          * 4. HMAC Key ID (32 bits)
188          * 5. All segments in the segments list (n * 128 bits)
189          */
190 
191         local_bh_disable();
192         ring = this_cpu_ptr(hmac_ring);
193         off = ring;
194 
195         /* source address */
196         memcpy(off, saddr, 16);
197         off += 16;
198 
199         /* first_segment value */
200         *off++ = hdr->first_segment;
201 
202         /* flags */
203         *off++ = hdr->flags;
204 
205         /* HMAC Key ID */
206         memcpy(off, &hmackeyid, 4);
207         off += 4;
208 
209         /* all segments in the list */
210         for (i = 0; i < hdr->first_segment + 1; i++) {
211                 memcpy(off, hdr->segments + i, 16);
212                 off += 16;
213         }
214 
215         dgsize = __do_hmac(hinfo, ring, plen, tmp_out,
216                            SEG6_HMAC_MAX_DIGESTSIZE);
217         local_bh_enable();
218 
219         if (dgsize < 0)
220                 return dgsize;
221 
222         wrsize = SEG6_HMAC_FIELD_LEN;
223         if (wrsize > dgsize)
224                 wrsize = dgsize;
225 
226         memset(output, 0, SEG6_HMAC_FIELD_LEN);
227         memcpy(output, tmp_out, wrsize);
228 
229         return 0;
230 }
231 EXPORT_SYMBOL(seg6_hmac_compute);
232 
233 /* checks if an incoming SR-enabled packet's HMAC status matches
234  * the incoming policy.
235  *
236  * called with rcu_read_lock()
237  */
238 bool seg6_hmac_validate_skb(struct sk_buff *skb)
239 {
240         u8 hmac_output[SEG6_HMAC_FIELD_LEN];
241         struct net *net = dev_net(skb->dev);
242         struct seg6_hmac_info *hinfo;
243         struct sr6_tlv_hmac *tlv;
244         struct ipv6_sr_hdr *srh;
245         struct inet6_dev *idev;
246 
247         idev = __in6_dev_get(skb->dev);
248 
249         srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
250 
251         tlv = seg6_get_tlv_hmac(srh);
252 
253         /* mandatory check but no tlv */
254         if (idev->cnf.seg6_require_hmac > 0 && !tlv)
255                 return false;
256 
257         /* no check */
258         if (idev->cnf.seg6_require_hmac < 0)
259                 return true;
260 
261         /* check only if present */
262         if (idev->cnf.seg6_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 
360         alg_count = ARRAY_SIZE(hmac_algos);
361 
362         for (i = 0; i < alg_count; i++) {
363                 struct crypto_shash **p_tfm;
364                 int shsize;
365 
366                 algo = &hmac_algos[i];
367                 algo->tfms = alloc_percpu(struct crypto_shash *);
368                 if (!algo->tfms)
369                         return -ENOMEM;
370 
371                 for_each_possible_cpu(cpu) {
372                         tfm = crypto_alloc_shash(algo->name, 0, 0);
373                         if (IS_ERR(tfm))
374                                 return PTR_ERR(tfm);
375                         p_tfm = per_cpu_ptr(algo->tfms, cpu);
376                         *p_tfm = tfm;
377                 }
378 
379                 p_tfm = raw_cpu_ptr(algo->tfms);
380                 tfm = *p_tfm;
381 
382                 shsize = sizeof(*shash) + crypto_shash_descsize(tfm);
383 
384                 algo->shashs = alloc_percpu(struct shash_desc *);
385                 if (!algo->shashs)
386                         return -ENOMEM;
387 
388                 for_each_possible_cpu(cpu) {
389                         shash = kzalloc_node(shsize, GFP_KERNEL,
390                                              cpu_to_node(cpu));
391                         if (!shash)
392                                 return -ENOMEM;
393                         *per_cpu_ptr(algo->shashs, cpu) = shash;
394                 }
395         }
396 
397         return 0;
398 }
399 
400 int __init seg6_hmac_init(void)
401 {
402         return seg6_hmac_init_algo();
403 }
404 EXPORT_SYMBOL(seg6_hmac_init);
405 
406 int __net_init seg6_hmac_net_init(struct net *net)
407 {
408         struct seg6_pernet_data *sdata = seg6_pernet(net);
409 
410         rhashtable_init(&sdata->hmac_infos, &rht_params);
411 
412         return 0;
413 }
414 EXPORT_SYMBOL(seg6_hmac_net_init);
415 
416 void seg6_hmac_exit(void)
417 {
418         struct seg6_hmac_algo *algo = NULL;
419         int i, alg_count, cpu;
420 
421         alg_count = ARRAY_SIZE(hmac_algos);
422         for (i = 0; i < alg_count; i++) {
423                 algo = &hmac_algos[i];
424                 for_each_possible_cpu(cpu) {
425                         struct crypto_shash *tfm;
426                         struct shash_desc *shash;
427 
428                         shash = *per_cpu_ptr(algo->shashs, cpu);
429                         kfree(shash);
430                         tfm = *per_cpu_ptr(algo->tfms, cpu);
431                         crypto_free_shash(tfm);
432                 }
433                 free_percpu(algo->tfms);
434                 free_percpu(algo->shashs);
435         }
436 }
437 EXPORT_SYMBOL(seg6_hmac_exit);
438 
439 void __net_exit seg6_hmac_net_exit(struct net *net)
440 {
441         struct seg6_pernet_data *sdata = seg6_pernet(net);
442 
443         rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
444 }
445 EXPORT_SYMBOL(seg6_hmac_net_exit);
446 

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