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
  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);