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/types.h> 16 #include <linux/socket.h> 17 #include <linux/sockios.h> 18 #include <linux/net.h> 19 #include <linux/netdevice.h> 20 #include <linux/in6.h> 21 #include <linux/icmpv6.h> 22 #include <linux/mroute6.h> 23 #include <linux/slab.h> 24 25 #include <linux/netfilter.h> 26 #include <linux/netfilter_ipv6.h> 27 28 #include <net/sock.h> 29 #include <net/snmp.h> 30 31 #include <net/ipv6.h> 32 #include <net/protocol.h> 33 #include <net/transp_v6.h> 34 #include <net/rawv6.h> 35 #include <net/ndisc.h> 36 #include <net/ip6_route.h> 37 #include <net/addrconf.h> 38 #include <net/xfrm.h> 39 40 #include <linux/cryptohash.h> 41 #include <crypto/hash.h> 42 #include <crypto/sha.h> 43 #include <net/seg6.h> 44 #include <net/genetlink.h> 45 #include <net/seg6_hmac.h> 46 #include <linux/random.h> 47 48 static DEFINE_PER_CPU(char [SEG6_HMAC_RING_SIZE], hmac_ring); 49 50 static int seg6_hmac_cmpfn(struct rhashtable_compare_arg *arg, const void *obj) 51 { 52 const struct seg6_hmac_info *hinfo = obj; 53 54 return (hinfo->hmackeyid != *(__u32 *)arg->key); 55 } 56 57 static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo) 58 { 59 kfree_rcu(hinfo, rcu); 60 } 61 62 static void seg6_free_hi(void *ptr, void *arg) 63 { 64 struct seg6_hmac_info *hinfo = (struct seg6_hmac_info *)ptr; 65 66 if (hinfo) 67 seg6_hinfo_release(hinfo); 68 } 69 70 static const struct rhashtable_params rht_params = { 71 .head_offset = offsetof(struct seg6_hmac_info, node), 72 .key_offset = offsetof(struct seg6_hmac_info, hmackeyid), 73 .key_len = sizeof(u32), 74 .automatic_shrinking = true, 75 .obj_cmpfn = seg6_hmac_cmpfn, 76 }; 77 78 static struct seg6_hmac_algo hmac_algos[] = { 79 { 80 .alg_id = SEG6_HMAC_ALGO_SHA1, 81 .name = "hmac(sha1)", 82 }, 83 { 84 .alg_id = SEG6_HMAC_ALGO_SHA256, 85 .name = "hmac(sha256)", 86 }, 87 }; 88 89 static struct sr6_tlv_hmac *seg6_get_tlv_hmac(struct ipv6_sr_hdr *srh) 90 { 91 struct sr6_tlv_hmac *tlv; 92 93 if (srh->hdrlen < (srh->first_segment + 1) * 2 + 5) 94 return NULL; 95 96 if (!sr_has_hmac(srh)) 97 return NULL; 98 99 tlv = (struct sr6_tlv_hmac *) 100 ((char *)srh + ((srh->hdrlen + 1) << 3) - 40); 101 102 if (tlv->tlvhdr.type != SR6_TLV_HMAC || tlv->tlvhdr.len != 38) 103 return NULL; 104 105 return tlv; 106 } 107 108 static struct seg6_hmac_algo *__hmac_get_algo(u8 alg_id) 109 { 110 struct seg6_hmac_algo *algo; 111 int i, alg_count; 112 113 alg_count = sizeof(hmac_algos) / sizeof(struct seg6_hmac_algo); 114 for (i = 0; i < alg_count; i++) { 115 algo = &hmac_algos[i]; 116 if (algo->alg_id == alg_id) 117 return algo; 118 } 119 120 return NULL; 121 } 122 123 static int __do_hmac(struct seg6_hmac_info *hinfo, const char *text, u8 psize, 124 u8 *output, int outlen) 125 { 126 struct seg6_hmac_algo *algo; 127 struct crypto_shash *tfm; 128 struct shash_desc *shash; 129 int ret, dgsize; 130 131 algo = __hmac_get_algo(hinfo->alg_id); 132 if (!algo) 133 return -ENOENT; 134 135 tfm = *this_cpu_ptr(algo->tfms); 136 137 dgsize = crypto_shash_digestsize(tfm); 138 if (dgsize > outlen) { 139 pr_debug("sr-ipv6: __do_hmac: digest size too big (%d / %d)\n", 140 dgsize, outlen); 141 return -ENOMEM; 142 } 143 144 ret = crypto_shash_setkey(tfm, hinfo->secret, hinfo->slen); 145 if (ret < 0) { 146 pr_debug("sr-ipv6: crypto_shash_setkey failed: err %d\n", ret); 147 goto failed; 148 } 149 150 shash = *this_cpu_ptr(algo->shashs); 151 shash->tfm = tfm; 152 153 ret = crypto_shash_digest(shash, text, psize, output); 154 if (ret < 0) { 155 pr_debug("sr-ipv6: crypto_shash_digest failed: err %d\n", ret); 156 goto failed; 157 } 158 159 return dgsize; 160 161 failed: 162 return ret; 163 } 164 165 int seg6_hmac_compute(struct seg6_hmac_info *hinfo, struct ipv6_sr_hdr *hdr, 166 struct in6_addr *saddr, u8 *output) 167 { 168 __be32 hmackeyid = cpu_to_be32(hinfo->hmackeyid); 169 u8 tmp_out[SEG6_HMAC_MAX_DIGESTSIZE]; 170 int plen, i, dgsize, wrsize; 171 char *ring, *off; 172 173 /* a 160-byte buffer for digest output allows to store highest known 174 * hash function (RadioGatun) with up to 1216 bits 175 */ 176 177 /* saddr(16) + first_seg(1) + flags(1) + keyid(4) + seglist(16n) */ 178 plen = 16 + 1 + 1 + 4 + (hdr->first_segment + 1) * 16; 179 180 /* this limit allows for 14 segments */ 181 if (plen >= SEG6_HMAC_RING_SIZE) 182 return -EMSGSIZE; 183 184 /* Let's build the HMAC text on the ring buffer. The text is composed 185 * as follows, in order: 186 * 187 * 1. Source IPv6 address (128 bits) 188 * 2. first_segment value (8 bits) 189 * 3. Flags (8 bits) 190 * 4. HMAC Key ID (32 bits) 191 * 5. All segments in the segments list (n * 128 bits) 192 */ 193 194 local_bh_disable(); 195 ring = this_cpu_ptr(hmac_ring); 196 off = ring; 197 198 /* source address */ 199 memcpy(off, saddr, 16); 200 off += 16; 201 202 /* first_segment value */ 203 *off++ = hdr->first_segment; 204 205 /* flags */ 206 *off++ = hdr->flags; 207 208 /* HMAC Key ID */ 209 memcpy(off, &hmackeyid, 4); 210 off += 4; 211 212 /* all segments in the list */ 213 for (i = 0; i < hdr->first_segment + 1; i++) { 214 memcpy(off, hdr->segments + i, 16); 215 off += 16; 216 } 217 218 dgsize = __do_hmac(hinfo, ring, plen, tmp_out, 219 SEG6_HMAC_MAX_DIGESTSIZE); 220 local_bh_enable(); 221 222 if (dgsize < 0) 223 return dgsize; 224 225 wrsize = SEG6_HMAC_FIELD_LEN; 226 if (wrsize > dgsize) 227 wrsize = dgsize; 228 229 memset(output, 0, SEG6_HMAC_FIELD_LEN); 230 memcpy(output, tmp_out, wrsize); 231 232 return 0; 233 } 234 EXPORT_SYMBOL(seg6_hmac_compute); 235 236 /* checks if an incoming SR-enabled packet's HMAC status matches 237 * the incoming policy. 238 * 239 * called with rcu_read_lock() 240 */ 241 bool seg6_hmac_validate_skb(struct sk_buff *skb) 242 { 243 u8 hmac_output[SEG6_HMAC_FIELD_LEN]; 244 struct net *net = dev_net(skb->dev); 245 struct seg6_hmac_info *hinfo; 246 struct sr6_tlv_hmac *tlv; 247 struct ipv6_sr_hdr *srh; 248 struct inet6_dev *idev; 249 250 idev = __in6_dev_get(skb->dev); 251 252 srh = (struct ipv6_sr_hdr *)skb_transport_header(skb); 253 254 tlv = seg6_get_tlv_hmac(srh); 255 256 /* mandatory check but no tlv */ 257 if (idev->cnf.seg6_require_hmac > 0 && !tlv) 258 return false; 259 260 /* no check */ 261 if (idev->cnf.seg6_require_hmac < 0) 262 return true; 263 264 /* check only if present */ 265 if (idev->cnf.seg6_require_hmac == 0 && !tlv) 266 return true; 267 268 /* now, seg6_require_hmac >= 0 && tlv */ 269 270 hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid)); 271 if (!hinfo) 272 return false; 273 274 if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output)) 275 return false; 276 277 if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0) 278 return false; 279 280 return true; 281 } 282 EXPORT_SYMBOL(seg6_hmac_validate_skb); 283 284 /* called with rcu_read_lock() */ 285 struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key) 286 { 287 struct seg6_pernet_data *sdata = seg6_pernet(net); 288 struct seg6_hmac_info *hinfo; 289 290 hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params); 291 292 return hinfo; 293 } 294 EXPORT_SYMBOL(seg6_hmac_info_lookup); 295 296 int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo) 297 { 298 struct seg6_pernet_data *sdata = seg6_pernet(net); 299 int err; 300 301 err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node, 302 rht_params); 303 304 return err; 305 } 306 EXPORT_SYMBOL(seg6_hmac_info_add); 307 308 int seg6_hmac_info_del(struct net *net, u32 key) 309 { 310 struct seg6_pernet_data *sdata = seg6_pernet(net); 311 struct seg6_hmac_info *hinfo; 312 int err = -ENOENT; 313 314 hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params); 315 if (!hinfo) 316 goto out; 317 318 err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node, 319 rht_params); 320 if (err) 321 goto out; 322 323 seg6_hinfo_release(hinfo); 324 325 out: 326 return err; 327 } 328 EXPORT_SYMBOL(seg6_hmac_info_del); 329 330 int seg6_push_hmac(struct net *net, struct in6_addr *saddr, 331 struct ipv6_sr_hdr *srh) 332 { 333 struct seg6_hmac_info *hinfo; 334 struct sr6_tlv_hmac *tlv; 335 int err = -ENOENT; 336 337 tlv = seg6_get_tlv_hmac(srh); 338 if (!tlv) 339 return -EINVAL; 340 341 rcu_read_lock(); 342 343 hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid)); 344 if (!hinfo) 345 goto out; 346 347 memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN); 348 err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac); 349 350 out: 351 rcu_read_unlock(); 352 return err; 353 } 354 EXPORT_SYMBOL(seg6_push_hmac); 355 356 static int seg6_hmac_init_algo(void) 357 { 358 struct seg6_hmac_algo *algo; 359 struct crypto_shash *tfm; 360 struct shash_desc *shash; 361 int i, alg_count, cpu; 362 363 alg_count = sizeof(hmac_algos) / sizeof(struct seg6_hmac_algo); 364 365 for (i = 0; i < alg_count; i++) { 366 struct crypto_shash **p_tfm; 367 int shsize; 368 369 algo = &hmac_algos[i]; 370 algo->tfms = alloc_percpu(struct crypto_shash *); 371 if (!algo->tfms) 372 return -ENOMEM; 373 374 for_each_possible_cpu(cpu) { 375 tfm = crypto_alloc_shash(algo->name, 0, GFP_KERNEL); 376 if (IS_ERR(tfm)) 377 return PTR_ERR(tfm); 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 return -ENOMEM; 390 391 for_each_possible_cpu(cpu) { 392 shash = kzalloc_node(shsize, GFP_KERNEL, 393 cpu_to_node(cpu)); 394 if (!shash) 395 return -ENOMEM; 396 *per_cpu_ptr(algo->shashs, cpu) = shash; 397 } 398 } 399 400 return 0; 401 } 402 403 int __init seg6_hmac_init(void) 404 { 405 return seg6_hmac_init_algo(); 406 } 407 EXPORT_SYMBOL(seg6_hmac_init); 408 409 int __net_init seg6_hmac_net_init(struct net *net) 410 { 411 struct seg6_pernet_data *sdata = seg6_pernet(net); 412 413 rhashtable_init(&sdata->hmac_infos, &rht_params); 414 415 return 0; 416 } 417 EXPORT_SYMBOL(seg6_hmac_net_init); 418 419 void seg6_hmac_exit(void) 420 { 421 struct seg6_hmac_algo *algo = NULL; 422 int i, alg_count, cpu; 423 424 alg_count = sizeof(hmac_algos) / sizeof(struct seg6_hmac_algo); 425 for (i = 0; i < alg_count; i++) { 426 algo = &hmac_algos[i]; 427 for_each_possible_cpu(cpu) { 428 struct crypto_shash *tfm; 429 struct shash_desc *shash; 430 431 shash = *per_cpu_ptr(algo->shashs, cpu); 432 kfree(shash); 433 tfm = *per_cpu_ptr(algo->tfms, cpu); 434 crypto_free_shash(tfm); 435 } 436 free_percpu(algo->tfms); 437 free_percpu(algo->shashs); 438 } 439 } 440 EXPORT_SYMBOL(seg6_hmac_exit); 441 442 void __net_exit seg6_hmac_net_exit(struct net *net) 443 { 444 struct seg6_pernet_data *sdata = seg6_pernet(net); 445 446 rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL); 447 } 448 EXPORT_SYMBOL(seg6_hmac_net_exit); 449