net/ipv6/seg6_hmac.c

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