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