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); 451