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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/kernel.h>
 16 #include <linux/types.h>
 17 #include <linux/socket.h>
 18 #include <linux/sockios.h>
 19 #include <linux/net.h>
 20 #include <linux/netdevice.h>
 21 #include <linux/in6.h>
 22 #include <linux/icmpv6.h>
 23 #include <linux/mroute6.h>
 24 #include <linux/slab.h>
 25 
 26 #include <linux/netfilter.h>
 27 #include <linux/netfilter_ipv6.h>
 28 
 29 #include <net/sock.h>
 30 #include <net/snmp.h>
 31 
 32 #include <net/ipv6.h>
 33 #include <net/protocol.h>
 34 #include <net/transp_v6.h>
 35 #include <net/rawv6.h>
 36 #include <net/ndisc.h>
 37 #include <net/ip6_route.h>
 38 #include <net/addrconf.h>
 39 #include <net/xfrm.h>
 40 
 41 #include <linux/cryptohash.h>
 42 #include <crypto/hash.h>
 43 #include <crypto/sha.h>
 44 #include <net/seg6.h>
 45 #include <net/genetlink.h>
 46 #include <net/seg6_hmac.h>
 47 #include <linux/random.h>
 48 
 49 static DEFINE_PER_CPU(char [SEG6_HMAC_RING_SIZE], hmac_ring);
 50 
 51 static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
 52 {
 53         const struct seg6_hmac_info *hinfo = obj;
 54 
 55         return (hinfo->hmackeyid != *(__u32 *)arg->key);
 56 }
 57 
 58 static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
 59 {
 60         kfree_rcu(hinfo, rcu);
 61 }
 62 
 63 static void seg6_free_hi(void *ptr, void *arg)
 64 {
 65         struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;
 66 
 67         if (hinfo)
 68                 seg6_hinfo_release(hinfo);
 69 }
 70 
 71 static const struct rhashtable_params rht_params = {
 72         .head_offset            = offsetof(struct seg6_hmac_info, node),
 73         .key_offset             = offsetof(struct seg6_hmac_info, hmackeyid),
 74         .key_len                = sizeof(u32),
 75         .automatic_shrinking    = true,
 76         .obj_cmpfn              = seg6_hmac_cmpfn,
 77 };
 78 
 79 static struct seg6_hmac_algo hmac_algos[] = {
 80         {
 81                 .alg_id = SEG6_HMAC_ALGO_SHA1,
 82                 .name = "hmac(sha1)",
 83         },
 84         {
 85                 .alg_id = SEG6_HMAC_ALGO_SHA256,
 86                 .name = "hmac(sha256)",
 87         },
 88 };
 89 
 90 static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
 91 {
 92         struct sr6_tlv_hmac *tlv;
 93 
 94         if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
 95                 return NULL;
 96 
 97         if (!sr_has_hmac(srh))
 98                 return NULL;
 99 
100         tlv = (struct sr6_tlv_hmac *)
101               ((char *)srh + ((srh->hdrlen + 1) << 3) - 40);
102 
103         if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
104                 return NULL;
105 
106         return tlv;
107 }
108 
109 static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id)
110 {
111         struct seg6_hmac_algo *algo;
112         int i, alg_count;
113 
114         alg_count = ARRAY_SIZE(hmac_algos);
115         for (i = 0; i < alg_count; i++) {
116                 algo = &hmac_algos[i];
117                 if (algo->alg_id == alg_id)
118                         return algo;
119         }
120 
121         return NULL;
122 }
123 
124 static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize,
125                      u8 *output, int outlen)
126 {
127         struct seg6_hmac_algo *algo;
128         struct crypto_shash *tfm;
129         struct shash_desc *shash;
130         int ret, dgsize;
131 
132         algo = __hmac_get_algo(hinfo->alg_id);
133         if (!algo)
134                 return -ENOENT;
135 
136         tfm = *this_cpu_ptr(algo->tfms);
137 
138         dgsize = crypto_shash_digestsize(tfm);
139         if (dgsize > outlen) {
140                 pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n",
141                          dgsize, outlen);
142                 return -ENOMEM;
143         }
144 
145         ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen);
146         if (ret < 0) {
147                 pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret);
148                 goto failed;
149         }
150 
151         shash = *this_cpu_ptr(algo->shashs);
152         shash->tfm = tfm;
153 
154         ret = crypto_shash_digest(shash, text, psize, output);
155         if (ret < 0) {
156                 pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret);
157                 goto failed;
158         }
159 
160         return dgsize;
161 
162 failed:
163         return ret;
164 }
165 
166 int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
167                       struct in6_addr *saddr, u8 *output)
168 {
169         __be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
170         u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE];
171         int plen, i, dgsize, wrsize;
172         char *ring, *off;
173 
174         /* a 160-byte buffer for digest output allows to store highest known
175          * hash function (RadioGatun) with up to 1216 bits
176          */
177 
178         /* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */
179         plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;
180 
181         /* this limit allows for 14 segments */
182         if (plen >= SEG6_HMAC_RING_SIZE)
183                 return -EMSGSIZE;
184 
185         /* Let's build the HMAC text on the ring buffer. The text is composed
186          * as follows, in order:
187          *
188          * 1. Source IPv6 address (128 bits)
189          * 2. first_segment value (8 bits)
190          * 3. Flags (8 bits)
191          * 4. HMAC Key ID (32 bits)
192          * 5. All segments in the segments list (n * 128 bits)
193          */
194 
195         local_bh_disable();
196         ring = this_cpu_ptr(hmac_ring);
197         off = ring;
198 
199         /* source address */
200         memcpy(off, saddr, 16);
201         off += 16;
202 
203         /* first_segment value */
204         *off++ = hdr->first_segment;
205 
206         /* flags */
207         *off++ = hdr->flags;
208 
209         /* HMAC Key ID */
210         memcpy(off, &hmackeyid, 4);
211         off += 4;
212 
213         /* all segments in the list */
214         for (i = 0; i < hdr->first_segment + 1; i++) {
215                 memcpy(off, hdr->segments + i, 16);
216                 off += 16;
217         }
218 
219         dgsize = __do_hmac(hinfo, ring, plen, tmp_out,
220                            SEG6_HMAC_MAX_DIGESTSIZE);
221         local_bh_enable();
222 
223         if (dgsize < 0)
224                 return dgsize;
225 
226         wrsize = SEG6_HMAC_FIELD_LEN;
227         if (wrsize > dgsize)
228                 wrsize = dgsize;
229 
230         memset(output, 0, SEG6_HMAC_FIELD_LEN);
231         memcpy(output, tmp_out, wrsize);
232 
233         return 0;
234 }
235 EXPORT_SYMBOL(seg6_hmac_compute);
236 
237 /* checks if an incoming SR-enabled packet's HMAC status matches
238  * the incoming policy.
239  *
240  * called with rcu_read_lock()
241  */
242 bool seg6_hmac_validate_skb(struct sk_buff *skb)
243 {
244         u8 hmac_output[SEG6_HMAC_FIELD_LEN];
245         struct net *net = dev_net(skb->dev);
246         struct seg6_hmac_info *hinfo;
247         struct sr6_tlv_hmac *tlv;
248         struct ipv6_sr_hdr *srh;
249         struct inet6_dev *idev;
250 
251         idev = __in6_dev_get(skb->dev);
252 
253         srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
254 
255         tlv = seg6_get_tlv_hmac(srh);
256 
257         /* mandatory check but no tlv */
258         if (idev->cnf.seg6_require_hmac > 0 && !tlv)
259                 return false;
260 
261         /* no check */
262         if (idev->cnf.seg6_require_hmac < 0)
263                 return true;
264 
265         /* check only if present */
266         if (idev->cnf.seg6_require_hmac == 0 && !tlv)
267                 return true;
268 
269         /* now, seg6_require_hmac >= 0 && tlv */
270 
271         hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
272         if (!hinfo)
273                 return false;
274 
275         if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
276                 return false;
277 
278         if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
279                 return false;
280 
281         return true;
282 }
283 EXPORT_SYMBOL(seg6_hmac_validate_skb);
284 
285 /* called with rcu_read_lock() */
286 struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
287 {
288         struct seg6_pernet_data *sdata = seg6_pernet(net);
289         struct seg6_hmac_info *hinfo;
290 
291         hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
292 
293         return hinfo;
294 }
295 EXPORT_SYMBOL(seg6_hmac_info_lookup);
296 
297 int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
298 {
299         struct seg6_pernet_data *sdata = seg6_pernet(net);
300         int err;
301 
302         err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
303                                             rht_params);
304 
305         return err;
306 }
307 EXPORT_SYMBOL(seg6_hmac_info_add);
308 
309 int seg6_hmac_info_del(struct net *net, u32 key)
310 {
311         struct seg6_pernet_data *sdata = seg6_pernet(net);
312         struct seg6_hmac_info *hinfo;
313         int err = -ENOENT;
314 
315         hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
316         if (!hinfo)
317                 goto out;
318 
319         err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
320                                      rht_params);
321         if (err)
322                 goto out;
323 
324         seg6_hinfo_release(hinfo);
325 
326 out:
327         return err;
328 }
329 EXPORT_SYMBOL(seg6_hmac_info_del);
330 
331 int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
332                    struct ipv6_sr_hdr *srh)
333 {
334         struct seg6_hmac_info *hinfo;
335         struct sr6_tlv_hmac *tlv;
336         int err = -ENOENT;
337 
338         tlv = seg6_get_tlv_hmac(srh);
339         if (!tlv)
340                 return -EINVAL;
341 
342         rcu_read_lock();
343 
344         hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
345         if (!hinfo)
346                 goto out;
347 
348         memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
349         err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
350 
351 out:
352         rcu_read_unlock();
353         return err;
354 }
355 EXPORT_SYMBOL(seg6_push_hmac);
356 
357 static int seg6_hmac_init_algo(void)
358 {
359         struct seg6_hmac_algo *algo;
360         struct crypto_shash *tfm;
361         struct shash_desc *shash;
362         int i, alg_count, cpu;
363 
364         alg_count = ARRAY_SIZE(hmac_algos);
365 
366         for (i = 0; i < alg_count; i++) {
367                 struct crypto_shash **p_tfm;
368                 int shsize;
369 
370                 algo = &hmac_algos[i];
371                 algo->tfms = alloc_percpu(struct crypto_shash *);
372                 if (!algo->tfms)
373                         return -ENOMEM;
374 
375                 for_each_possible_cpu(cpu) {
376                         tfm = crypto_alloc_shash(algo->name, 0, GFP_KERNEL);
377                         if (IS_ERR(tfm))
378                                 return PTR_ERR(tfm);
379                         p_tfm = per_cpu_ptr(algo->tfms, cpu);
380                         *p_tfm = tfm;
381                 }
382 
383                 p_tfm = raw_cpu_ptr(algo->tfms);
384                 tfm = *p_tfm;
385 
386                 shsize = sizeof(*shash) + crypto_shash_descsize(tfm);
387 
388                 algo->shashs = alloc_percpu(struct shash_desc *);
389                 if (!algo->shashs)
390                         return -ENOMEM;
391 
392                 for_each_possible_cpu(cpu) {
393                         shash = kzalloc_node(shsize, GFP_KERNEL,
394                                              cpu_to_node(cpu));
395                         if (!shash)
396                                 return -ENOMEM;
397                         *per_cpu_ptr(algo->shashs, cpu) = shash;
398                 }
399         }
400 
401         return 0;
402 }
403 
404 int __init seg6_hmac_init(void)
405 {
406         return seg6_hmac_init_algo();
407 }
408 EXPORT_SYMBOL(seg6_hmac_init);
409 
410 int __net_init seg6_hmac_net_init(struct net *net)
411 {
412         struct seg6_pernet_data *sdata = seg6_pernet(net);
413 
414         rhashtable_init(&sdata->hmac_infos, &rht_params);
415 
416         return 0;
417 }
418 EXPORT_SYMBOL(seg6_hmac_net_init);
419 
420 void seg6_hmac_exit(void)
421 {
422         struct seg6_hmac_algo *algo = NULL;
423         int i, alg_count, cpu;
424 
425         alg_count = ARRAY_SIZE(hmac_algos);
426         for (i = 0; i < alg_count; i++) {
427                 algo = &hmac_algos[i];
428                 for_each_possible_cpu(cpu) {
429                         struct crypto_shash *tfm;
430                         struct shash_desc *shash;
431 
432                         shash = *per_cpu_ptr(algo->shashs, cpu);
433                         kfree(shash);
434                         tfm = *per_cpu_ptr(algo->tfms, cpu);
435                         crypto_free_shash(tfm);
436                 }
437                 free_percpu(algo->tfms);
438                 free_percpu(algo->shashs);
439         }
440 }
441 EXPORT_SYMBOL(seg6_hmac_exit);
442 
443 void __net_exit seg6_hmac_net_exit(struct net *net)
444 {
445         struct seg6_pernet_data *sdata = seg6_pernet(net);
446 
447         rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
448 }
449 EXPORT_SYMBOL(seg6_hmac_net_exit);
450 

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