net/ipv6/seg6_hmac.c

   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);