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 <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; 359 360 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 } 404 405 int __net_init seg6_hmac_net_init(struct net *net) 406 { 407 struct seg6_pernet_data *sdata = seg6_pernet(net); 408 409 return rhashtable_init(&sdata->hmac_infos, &rht_params); 410 } 411 412 void seg6_hmac_exit(void) 413 { 414 struct seg6_hmac_algo *algo = NULL; 415 int i, alg_count, cpu; 416 417 alg_count = ARRAY_SIZE(hmac_algos); 418 for (i = 0; i < alg_count; i++) { 419 algo = &hmac_algos[i]; 420 for_each_possible_cpu(cpu) { 421 struct crypto_shash *tfm; 422 struct shash_desc *shash; 423 424 shash = *per_cpu_ptr(algo->shashs, cpu); 425 kfree(shash); 426 tfm = *per_cpu_ptr(algo->tfms, cpu); 427 crypto_free_shash(tfm); 428 } 429 free_percpu(algo->tfms); 430 free_percpu(algo->shashs); 431 } 432 } 433 EXPORT_SYMBOL(seg6_hmac_exit); 434 435 void __net_exit seg6_hmac_net_exit(struct net *net) 436 { 437 struct seg6_pernet_data *sdata = seg6_pernet(net); 438 439 rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL); 440 } 441 EXPORT_SYMBOL(seg6_hmac_net_exit); 442