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