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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 <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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