linux/net/ipv6/seg6_hmac.c
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   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
  43static DEFINE_PER_CPU(char [SEG6_HMAC_RING_SIZE], hmac_ring);
  44
  45static 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
  52static inline void seg6_hinfo_release(struct seg6_hmac_info *hinfo)
  53{
  54        kfree_rcu(hinfo, rcu);
  55}
  56
  57static 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
  65static 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
  73static 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
  84static 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
 103static 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
 118static 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
 156failed:
 157        return ret;
 158}
 159
 160int 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}
 229EXPORT_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 */
 236bool 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
 245        idev = __in6_dev_get(skb->dev);
 246
 247        srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
 248
 249        tlv = seg6_get_tlv_hmac(srh);
 250
 251        /* mandatory check but no tlv */
 252        if (idev->cnf.seg6_require_hmac > 0 && !tlv)
 253                return false;
 254
 255        /* no check */
 256        if (idev->cnf.seg6_require_hmac < 0)
 257                return true;
 258
 259        /* check only if present */
 260        if (idev->cnf.seg6_require_hmac == 0 && !tlv)
 261                return true;
 262
 263        /* now, seg6_require_hmac >= 0 && tlv */
 264
 265        hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
 266        if (!hinfo)
 267                return false;
 268
 269        if (seg6_hmac_compute(hinfo, srh, &ipv6_hdr(skb)->saddr, hmac_output))
 270                return false;
 271
 272        if (memcmp(hmac_output, tlv->hmac, SEG6_HMAC_FIELD_LEN) != 0)
 273                return false;
 274
 275        return true;
 276}
 277EXPORT_SYMBOL(seg6_hmac_validate_skb);
 278
 279/* called with rcu_read_lock() */
 280struct seg6_hmac_info *seg6_hmac_info_lookup(struct net *net, u32 key)
 281{
 282        struct seg6_pernet_data *sdata = seg6_pernet(net);
 283        struct seg6_hmac_info *hinfo;
 284
 285        hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
 286
 287        return hinfo;
 288}
 289EXPORT_SYMBOL(seg6_hmac_info_lookup);
 290
 291int seg6_hmac_info_add(struct net *net, u32 key, struct seg6_hmac_info *hinfo)
 292{
 293        struct seg6_pernet_data *sdata = seg6_pernet(net);
 294        int err;
 295
 296        err = rhashtable_lookup_insert_fast(&sdata->hmac_infos, &hinfo->node,
 297                                            rht_params);
 298
 299        return err;
 300}
 301EXPORT_SYMBOL(seg6_hmac_info_add);
 302
 303int seg6_hmac_info_del(struct net *net, u32 key)
 304{
 305        struct seg6_pernet_data *sdata = seg6_pernet(net);
 306        struct seg6_hmac_info *hinfo;
 307        int err = -ENOENT;
 308
 309        hinfo = rhashtable_lookup_fast(&sdata->hmac_infos, &key, rht_params);
 310        if (!hinfo)
 311                goto out;
 312
 313        err = rhashtable_remove_fast(&sdata->hmac_infos, &hinfo->node,
 314                                     rht_params);
 315        if (err)
 316                goto out;
 317
 318        seg6_hinfo_release(hinfo);
 319
 320out:
 321        return err;
 322}
 323EXPORT_SYMBOL(seg6_hmac_info_del);
 324
 325int seg6_push_hmac(struct net *net, struct in6_addr *saddr,
 326                   struct ipv6_sr_hdr *srh)
 327{
 328        struct seg6_hmac_info *hinfo;
 329        struct sr6_tlv_hmac *tlv;
 330        int err = -ENOENT;
 331
 332        tlv = seg6_get_tlv_hmac(srh);
 333        if (!tlv)
 334                return -EINVAL;
 335
 336        rcu_read_lock();
 337
 338        hinfo = seg6_hmac_info_lookup(net, be32_to_cpu(tlv->hmackeyid));
 339        if (!hinfo)
 340                goto out;
 341
 342        memset(tlv->hmac, 0, SEG6_HMAC_FIELD_LEN);
 343        err = seg6_hmac_compute(hinfo, srh, saddr, tlv->hmac);
 344
 345out:
 346        rcu_read_unlock();
 347        return err;
 348}
 349EXPORT_SYMBOL(seg6_push_hmac);
 350
 351static int seg6_hmac_init_algo(void)
 352{
 353        struct seg6_hmac_algo *algo;
 354        struct crypto_shash *tfm;
 355        struct shash_desc *shash;
 356        int i, alg_count, cpu;
 357
 358        alg_count = ARRAY_SIZE(hmac_algos);
 359
 360        for (i = 0; i < alg_count; i++) {
 361                struct crypto_shash **p_tfm;
 362                int shsize;
 363
 364                algo = &hmac_algos[i];
 365                algo->tfms = alloc_percpu(struct crypto_shash *);
 366                if (!algo->tfms)
 367                        return -ENOMEM;
 368
 369                for_each_possible_cpu(cpu) {
 370                        tfm = crypto_alloc_shash(algo->name, 0, 0);
 371                        if (IS_ERR(tfm))
 372                                return PTR_ERR(tfm);
 373                        p_tfm = per_cpu_ptr(algo->tfms, cpu);
 374                        *p_tfm = tfm;
 375                }
 376
 377                p_tfm = raw_cpu_ptr(algo->tfms);
 378                tfm = *p_tfm;
 379
 380                shsize = sizeof(*shash) + crypto_shash_descsize(tfm);
 381
 382                algo->shashs = alloc_percpu(struct shash_desc *);
 383                if (!algo->shashs)
 384                        return -ENOMEM;
 385
 386                for_each_possible_cpu(cpu) {
 387                        shash = kzalloc_node(shsize, GFP_KERNEL,
 388                                             cpu_to_node(cpu));
 389                        if (!shash)
 390                                return -ENOMEM;
 391                        *per_cpu_ptr(algo->shashs, cpu) = shash;
 392                }
 393        }
 394
 395        return 0;
 396}
 397
 398int __init seg6_hmac_init(void)
 399{
 400        return seg6_hmac_init_algo();
 401}
 402EXPORT_SYMBOL(seg6_hmac_init);
 403
 404int __net_init seg6_hmac_net_init(struct net *net)
 405{
 406        struct seg6_pernet_data *sdata = seg6_pernet(net);
 407
 408        rhashtable_init(&sdata->hmac_infos, &rht_params);
 409
 410        return 0;
 411}
 412EXPORT_SYMBOL(seg6_hmac_net_init);
 413
 414void seg6_hmac_exit(void)
 415{
 416        struct seg6_hmac_algo *algo = NULL;
 417        int i, alg_count, cpu;
 418
 419        alg_count = ARRAY_SIZE(hmac_algos);
 420        for (i = 0; i < alg_count; i++) {
 421                algo = &hmac_algos[i];
 422                for_each_possible_cpu(cpu) {
 423                        struct crypto_shash *tfm;
 424                        struct shash_desc *shash;
 425
 426                        shash = *per_cpu_ptr(algo->shashs, cpu);
 427                        kfree(shash);
 428                        tfm = *per_cpu_ptr(algo->tfms, cpu);
 429                        crypto_free_shash(tfm);
 430                }
 431                free_percpu(algo->tfms);
 432                free_percpu(algo->shashs);
 433        }
 434}
 435EXPORT_SYMBOL(seg6_hmac_exit);
 436
 437void __net_exit seg6_hmac_net_exit(struct net *net)
 438{
 439        struct seg6_pernet_data *sdata = seg6_pernet(net);
 440
 441        rhashtable_free_and_destroy(&sdata->hmac_infos, seg6_free_hi, NULL);
 442}
 443EXPORT_SYMBOL(seg6_hmac_net_exit);
 444