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 <[email protected]>
   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 <crypto/hash.h>
  38 #include <net/seg6.h>
  39 #include <net/genetlink.h>
  40 #include <net/seg6_hmac.h>
  41 #include <linux/random.h>
  42
  43 static DEFINE_PER_CPU(char [SEG6_HMAC_RING_SIZE], hmac_ring);
  44
  45 static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
  46 {
  47         const struct seg6_hmac_info *hinfo = obj;
  48
  49         return (hinfo->hmackeyid != *(__u32 *)arg->key);
  50 }
  51
  52 static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
  53 {
  54         kfree_rcu(hinfo, rcu);
  55 }
  56
  57 static void seg6_free_hi(void *ptr, void *arg)
  58 {
  59         struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr;
  60
  61         if (hinfo)
  62                 seg6_hinfo_release(hinfo);
  63 }
  64
  65 static const struct rhashtable_params rht_params = {
  66         .head_offset            = offsetof(struct seg6_hmac_info, node),
  67         .key_offset             = offsetof(struct seg6_hmac_info, hmackeyid),
  68         .key_len                = sizeof(u32),
  69         .automatic_shrinking    = true,
  70         .obj_cmpfn              = seg6_hmac_cmpfn,
  71 };
  72
  73 static struct seg6_hmac_algo hmac_algos[] = {
  74         {
  75                 .alg_id = SEG6_HMAC_ALGO_SHA1,
  76                 .name = "hmac(sha1)",
  77         },
  78         {
  79                 .alg_id = SEG6_HMAC_ALGO_SHA256,
  80                 .name = "hmac(sha256)",
  81         },
  82 };
  83
  84 static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh)
  85 {
  86         struct sr6_tlv_hmac *tlv;
  87
  88         if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5)
  89                 return NULL;
  90
  91         if (!sr_has_hmac(srh))
  92                 return NULL;
  93
  94         tlv = (struct sr6_tlv_hmac *)
  95               ((char *)srh + ((srh->hdrlen + 1) << 3) - 40);
  96
  97         if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38)
  98                 return NULL;
  99
 100         return tlv;
 101 }
 102
 103 static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id)
 104 {
 105         struct seg6_hmac_algo *algo;
 106         int i, alg_count;
 107
 108         alg_count = ARRAY_SIZE(hmac_algos);
 109         for (i = 0; i < alg_count; i++) {
 110                 algo = &hmac_algos[i];
 111                 if (algo->alg_id == alg_id)
 112                         return algo;
 113         }
 114
 115         return NULL;
 116 }
 117
 118 static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize,
 119                      u8 *output, int outlen)
 120 {
 121         struct seg6_hmac_algo *algo;
 122         struct crypto_shash *tfm;
 123         struct shash_desc *shash;
 124         int ret, dgsize;
 125
 126         algo = __hmac_get_algo(hinfo->alg_id);
 127         if (!algo)
 128                 return -ENOENT;
 129
 130         tfm = *this_cpu_ptr(algo->tfms);
 131
 132         dgsize = crypto_shash_digestsize(tfm);
 133         if (dgsize > outlen) {
 134                 pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n",
 135                          dgsize, outlen);
 136                 return -ENOMEM;
 137         }
 138
 139         ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen);
 140         if (ret < 0) {
 141                 pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret);
 142                 goto failed;
 143         }
 144
 145         shash = *this_cpu_ptr(algo->shashs);
 146         shash->tfm = tfm;
 147
 148         ret = crypto_shash_digest(shash, text, psize, output);
 149         if (ret < 0) {
 150                 pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret);
 151                 goto failed;
 152         }
 153
 154         return dgsize;
 155
 156 failed:
 157         return ret;
 158 }
 159
 160 int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr,
 161                       struct in6_addr *saddr, u8 *output)
 162 {
 163         __be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid);
 164         u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE];
 165         int plen, i, dgsize, wrsize;
 166         char *ring, *off;
 167
 168         /* a 160-byte buffer for digest output allows to store highest known
 169          * hash function (RadioGatun) with up to 1216 bits
 170          */
 171
 172         /* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */
 173         plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16;
 174
 175         /* this limit allows for 14 segments */
 176         if (plen >= SEG6_HMAC_RING_SIZE)
 177                 return -EMSGSIZE;
 178
 179         /* Let's build the HMAC text on the ring buffer. The text is composed
 180          * as follows, in order:
 181          *
 182          * 1. Source IPv6 address (128 bits)
 183          * 2. first_segment value (8 bits)
 184          * 3. Flags (8 bits)
 185          * 4. HMAC Key ID (32 bits)
 186          * 5. All segments in the segments list (n * 128 bits)
 187          */
 188
 189         local_bh_disable();
 190         ring = this_cpu_ptr(hmac_ring);
 191         off = ring;
 192
 193         /* source address */
 194         memcpy(off, saddr, 16);
 195         off += 16;
 196
 197         /* first_segment value */
 198         *off++ = hdr->first_segment;
 199
 200         /* flags */
 201         *off++ = hdr->flags;
 202
 203         /* HMAC Key ID */
 204         memcpy(off, &hmackeyid, 4);
 205         off += 4;
 206
 207         /* all segments in the list */
 208         for (i = 0; i < hdr->first_segment + 1; i++) {
 209                 memcpy(off, hdr->segments + i, 16);
 210                 off += 16;
 211         }
 212
 213         dgsize = __do_hmac(hinfo, ring, plen, tmp_out,
 214                            SEG6_HMAC_MAX_DIGESTSIZE);
 215         local_bh_enable();
 216
 217         if (dgsize < 0)
 218                 return dgsize;
 219
 220         wrsize = SEG6_HMAC_FIELD_LEN;
 221         if (wrsize > dgsize)
 222                 wrsize = dgsize;
 223
 224         memset(output, 0, SEG6_HMAC_FIELD_LEN);
 225         memcpy(output, tmp_out, wrsize);
 226
 227         return 0;
 228 }
 229 EXPORT_SYMBOL(seg6_hmac_compute);
 230
 231 /* checks if an incoming SR-enabled packet's HMAC status matches
 232  * the incoming policy.
 233  *
 234  * called with rcu_read_lock()
 235  */
 236 bool seg6_hmac_validate_skb(struct sk_buff *skb)
 237 {
 238         u8 hmac_output[SEG6_HMAC_FIELD_LEN];
 239         struct net *net = dev_net(skb->dev);
 240         struct seg6_hmac_info *hinfo;
 241         struct sr6_tlv_hmac *tlv;
 242         struct ipv6_sr_hdr *srh;
 243         struct inet6_dev *idev;
 244         int require_hmac;
 245
 246         idev = __in6_dev_get(skb->dev);
 247
 248         srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
 249
 250         tlv = seg6_get_tlv_hmac(srh);
 251
 252         require_hmac = READ_ONCE(idev->cnf.seg6_require_hmac);
 253         /* mandatory check but no tlv */
 254         if (require_hmac > 0 && !tlv)
 255                 return false;
 256
 257         /* no check */
 258         if (require_hmac < 0)
 259                 return true;
 260
 261         /* check only if present */
 262         if (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         int ret = -ENOMEM;
 360
 361         alg_count = ARRAY_SIZE(hmac_algos);
 362
 363         for (i = 0; i < alg_count; i++) {
 364                 struct crypto_shash **p_tfm;
 365                 int shsize;
 366
 367                 algo = &hmac_algos[i];
 368                 algo->tfms = alloc_percpu(struct crypto_shash *);
 369                 if (!algo->tfms)
 370                         goto error_out;
 371
 372                 for_each_possible_cpu(cpu) {
 373                         tfm = crypto_alloc_shash(algo->name, 0, 0);
 374                         if (IS_ERR(tfm)) {
 375                                 ret = PTR_ERR(tfm);
 376                                 goto error_out;
 377                         }
 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                         goto error_out;
 390
 391                 for_each_possible_cpu(cpu) {
 392                         shash = kzalloc_node(shsize, GFP_KERNEL,
 393                                              cpu_to_node(cpu));
 394                         if (!shash)
 395                                 goto error_out;
 396                         *per_cpu_ptr(algo->shashs, cpu) = shash;
 397                 }
 398         }
 399
 400         return 0;
 401
 402 error_out:
 403         seg6_hmac_exit();
 404         return ret;
 405 }
 406
 407 int __init seg6_hmac_init(void)
 408 {
 409         return seg6_hmac_init_algo();
 410 }
 411
 412 int __net_init seg6_hmac_net_init(struct net *net)
 413 {
 414         struct seg6_pernet_data *sdata = seg6_pernet(net);
 415
 416         return rhashtable_init(&sdata->hmac_infos, &rht_params);
 417 }
 418
 419 void seg6_hmac_exit(void)
 420 {
 421         struct seg6_hmac_algo *algo = NULL;
 422         struct crypto_shash *tfm;
 423         struct shash_desc *shash;
 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
 430                 if (algo->shashs) {
 431                         for_each_possible_cpu(cpu) {
 432                                 shash = *per_cpu_ptr(algo->shashs, cpu);
 433                                 kfree(shash);
 434                         }
 435                         free_percpu(algo->shashs);
 436                 }
 437
 438                 if (algo->tfms) {
 439                         for_each_possible_cpu(cpu) {
 440                                 tfm = *per_cpu_ptr(algo->tfms, cpu);
 441                                 crypto_free_shash(tfm);
 442                         }
 443                         free_percpu(algo->tfms);
 444                 }
 445         }
 446 }
 447 EXPORT_SYMBOL(seg6_hmac_exit);
 448
 449 void __net_exit seg6_hmac_net_exit(struct net *net)
 450 {
 451         struct seg6_pernet_data *sdata = seg6_pernet(net);
 452
 453         rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
 454 }
 455 EXPORT_SYMBOL(seg6_hmac_net_exit);