drivers/net/wireguard/noise.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
   4  */
   5
   6 #include "noise.h"
   7 #include "device.h"
   8 #include "peer.h"
   9 #include "messages.h"
  10 #include "queueing.h"
  11 #include "peerlookup.h"
  12
  13 #include <linux/rcupdate.h>
  14 #include <linux/slab.h>
  15 #include <linux/bitmap.h>
  16 #include <linux/scatterlist.h>
  17 #include <linux/highmem.h>
  18 #include <crypto/algapi.h>
  19
  20 /* This implements Noise_IKpsk2:
  21  *
  22  * <- s
  23  * ******
  24  * -> e, es, s, ss, {t}
  25  * <- e, ee, se, psk, {}
  26  */
  27
  28 static const u8 handshake_name[37] = "Noise_IKpsk2_25519_ChaChaPoly_BLAKE2s";
  29 static const u8 identifier_name[34] = "WireGuard v1 zx2c4 Jason@zx2c4.com";
  30 static u8 handshake_init_hash[NOISE_HASH_LEN] __ro_after_init;
  31 static u8 handshake_init_chaining_key[NOISE_HASH_LEN] __ro_after_init;
  32 static atomic64_t keypair_counter = ATOMIC64_INIT(0);
  33
  34 void __init wg_noise_init(void)
  35 {
  36         struct blake2s_state blake;
  37
  38         blake2s(handshake_init_chaining_key, handshake_name, NULL,
  39                 NOISE_HASH_LEN, sizeof(handshake_name), 0);
  40         blake2s_init(&blake, NOISE_HASH_LEN);
  41         blake2s_update(&blake, handshake_init_chaining_key, NOISE_HASH_LEN);
  42         blake2s_update(&blake, identifier_name, sizeof(identifier_name));
  43         blake2s_final(&blake, handshake_init_hash);
  44 }
  45
  46 /* Must hold peer->handshake.static_identity->lock */
  47 bool wg_noise_precompute_static_static(struct wg_peer *peer)
  48 {
  49         bool ret = true;
  50
  51         down_write(&peer->handshake.lock);
  52         if (peer->handshake.static_identity->has_identity)
  53                 ret = curve25519(
  54                         peer->handshake.precomputed_static_static,
  55                         peer->handshake.static_identity->static_private,
  56                         peer->handshake.remote_static);
  57         else
  58                 memset(peer->handshake.precomputed_static_static, 0,
  59                        NOISE_PUBLIC_KEY_LEN);
  60         up_write(&peer->handshake.lock);
  61         return ret;
  62 }
  63
  64 bool wg_noise_handshake_init(struct noise_handshake *handshake,
  65                            struct noise_static_identity *static_identity,
  66                            const u8 peer_public_key[NOISE_PUBLIC_KEY_LEN],
  67                            const u8 peer_preshared_key[NOISE_SYMMETRIC_KEY_LEN],
  68                            struct wg_peer *peer)
  69 {
  70         memset(handshake, 0, sizeof(*handshake));
  71         init_rwsem(&handshake->lock);
  72         handshake->entry.type = INDEX_HASHTABLE_HANDSHAKE;
  73         handshake->entry.peer = peer;
  74         memcpy(handshake->remote_static, peer_public_key, NOISE_PUBLIC_KEY_LEN);
  75         if (peer_preshared_key)
  76                 memcpy(handshake->preshared_key, peer_preshared_key,
  77                        NOISE_SYMMETRIC_KEY_LEN);
  78         handshake->static_identity = static_identity;
  79         handshake->state = HANDSHAKE_ZEROED;
  80         return wg_noise_precompute_static_static(peer);
  81 }
  82
  83 static void handshake_zero(struct noise_handshake *handshake)
  84 {
  85         memset(&handshake->ephemeral_private, 0, NOISE_PUBLIC_KEY_LEN);
  86         memset(&handshake->remote_ephemeral, 0, NOISE_PUBLIC_KEY_LEN);
  87         memset(&handshake->hash, 0, NOISE_HASH_LEN);
  88         memset(&handshake->chaining_key, 0, NOISE_HASH_LEN);
  89         handshake->remote_index = 0;
  90         handshake->state = HANDSHAKE_ZEROED;
  91 }
  92
  93 void wg_noise_handshake_clear(struct noise_handshake *handshake)
  94 {
  95         wg_index_hashtable_remove(
  96                         handshake->entry.peer->device->index_hashtable,
  97                         &handshake->entry);
  98         down_write(&handshake->lock);
  99         handshake_zero(handshake);
 100         up_write(&handshake->lock);
 101         wg_index_hashtable_remove(
 102                         handshake->entry.peer->device->index_hashtable,
 103                         &handshake->entry);
 104 }
 105
 106 static struct noise_keypair *keypair_create(struct wg_peer *peer)
 107 {
 108         struct noise_keypair *keypair = kzalloc(sizeof(*keypair), GFP_KERNEL);
 109
 110         if (unlikely(!keypair))
 111                 return NULL;
 112         keypair->internal_id = atomic64_inc_return(&keypair_counter);
 113         keypair->entry.type = INDEX_HASHTABLE_KEYPAIR;
 114         keypair->entry.peer = peer;
 115         kref_init(&keypair->refcount);
 116         return keypair;
 117 }
 118
 119 static void keypair_free_rcu(struct rcu_head *rcu)
 120 {
 121         kzfree(container_of(rcu, struct noise_keypair, rcu));
 122 }
 123
 124 static void keypair_free_kref(struct kref *kref)
 125 {
 126         struct noise_keypair *keypair =
 127                 container_of(kref, struct noise_keypair, refcount);
 128
 129         net_dbg_ratelimited("%s: Keypair %llu destroyed for peer %llu\n",
 130                             keypair->entry.peer->device->dev->name,
 131                             keypair->internal_id,
 132                             keypair->entry.peer->internal_id);
 133         wg_index_hashtable_remove(keypair->entry.peer->device->index_hashtable,
 134                                   &keypair->entry);
 135         call_rcu(&keypair->rcu, keypair_free_rcu);
 136 }
 137
 138 void wg_noise_keypair_put(struct noise_keypair *keypair, bool unreference_now)
 139 {
 140         if (unlikely(!keypair))
 141                 return;
 142         if (unlikely(unreference_now))
 143                 wg_index_hashtable_remove(
 144                         keypair->entry.peer->device->index_hashtable,
 145                         &keypair->entry);
 146         kref_put(&keypair->refcount, keypair_free_kref);
 147 }
 148
 149 struct noise_keypair *wg_noise_keypair_get(struct noise_keypair *keypair)
 150 {
 151         RCU_LOCKDEP_WARN(!rcu_read_lock_bh_held(),
 152                 "Taking noise keypair reference without holding the RCU BH read lock");
 153         if (unlikely(!keypair || !kref_get_unless_zero(&keypair->refcount)))
 154                 return NULL;
 155         return keypair;
 156 }
 157
 158 void wg_noise_keypairs_clear(struct noise_keypairs *keypairs)
 159 {
 160         struct noise_keypair *old;
 161
 162         spin_lock_bh(&keypairs->keypair_update_lock);
 163
 164         /* We zero the next_keypair before zeroing the others, so that
 165          * wg_noise_received_with_keypair returns early before subsequent ones
 166          * are zeroed.
 167          */
 168         old = rcu_dereference_protected(keypairs->next_keypair,
 169                 lockdep_is_held(&keypairs->keypair_update_lock));
 170         RCU_INIT_POINTER(keypairs->next_keypair, NULL);
 171         wg_noise_keypair_put(old, true);
 172
 173         old = rcu_dereference_protected(keypairs->previous_keypair,
 174                 lockdep_is_held(&keypairs->keypair_update_lock));
 175         RCU_INIT_POINTER(keypairs->previous_keypair, NULL);
 176         wg_noise_keypair_put(old, true);
 177
 178         old = rcu_dereference_protected(keypairs->current_keypair,
 179                 lockdep_is_held(&keypairs->keypair_update_lock));
 180         RCU_INIT_POINTER(keypairs->current_keypair, NULL);
 181         wg_noise_keypair_put(old, true);
 182
 183         spin_unlock_bh(&keypairs->keypair_update_lock);
 184 }
 185
 186 void wg_noise_expire_current_peer_keypairs(struct wg_peer *peer)
 187 {
 188         struct noise_keypair *keypair;
 189
 190         wg_noise_handshake_clear(&peer->handshake);
 191         wg_noise_reset_last_sent_handshake(&peer->last_sent_handshake);
 192
 193         spin_lock_bh(&peer->keypairs.keypair_update_lock);
 194         keypair = rcu_dereference_protected(peer->keypairs.next_keypair,
 195                         lockdep_is_held(&peer->keypairs.keypair_update_lock));
 196         if (keypair)
 197                 keypair->sending.is_valid = false;
 198         keypair = rcu_dereference_protected(peer->keypairs.current_keypair,
 199                         lockdep_is_held(&peer->keypairs.keypair_update_lock));
 200         if (keypair)
 201                 keypair->sending.is_valid = false;
 202         spin_unlock_bh(&peer->keypairs.keypair_update_lock);
 203 }
 204
 205 static void add_new_keypair(struct noise_keypairs *keypairs,
 206                             struct noise_keypair *new_keypair)
 207 {
 208         struct noise_keypair *previous_keypair, *next_keypair, *current_keypair;
 209
 210         spin_lock_bh(&keypairs->keypair_update_lock);
 211         previous_keypair = rcu_dereference_protected(keypairs->previous_keypair,
 212                 lockdep_is_held(&keypairs->keypair_update_lock));
 213         next_keypair = rcu_dereference_protected(keypairs->next_keypair,
 214                 lockdep_is_held(&keypairs->keypair_update_lock));
 215         current_keypair = rcu_dereference_protected(keypairs->current_keypair,
 216                 lockdep_is_held(&keypairs->keypair_update_lock));
 217         if (new_keypair->i_am_the_initiator) {
 218                 /* If we're the initiator, it means we've sent a handshake, and
 219                  * received a confirmation response, which means this new
 220                  * keypair can now be used.
 221                  */
 222                 if (next_keypair) {
 223                         /* If there already was a next keypair pending, we
 224                          * demote it to be the previous keypair, and free the
 225                          * existing current. Note that this means KCI can result
 226                          * in this transition. It would perhaps be more sound to
 227                          * always just get rid of the unused next keypair
 228                          * instead of putting it in the previous slot, but this
 229                          * might be a bit less robust. Something to think about
 230                          * for the future.
 231                          */
 232                         RCU_INIT_POINTER(keypairs->next_keypair, NULL);
 233                         rcu_assign_pointer(keypairs->previous_keypair,
 234                                            next_keypair);
 235                         wg_noise_keypair_put(current_keypair, true);
 236                 } else /* If there wasn't an existing next keypair, we replace
 237                         * the previous with the current one.
 238                         */
 239                         rcu_assign_pointer(keypairs->previous_keypair,
 240                                            current_keypair);
 241                 /* At this point we can get rid of the old previous keypair, and
 242                  * set up the new keypair.
 243                  */
 244                 wg_noise_keypair_put(previous_keypair, true);
 245                 rcu_assign_pointer(keypairs->current_keypair, new_keypair);
 246         } else {
 247                 /* If we're the responder, it means we can't use the new keypair
 248                  * until we receive confirmation via the first data packet, so
 249                  * we get rid of the existing previous one, the possibly
 250                  * existing next one, and slide in the new next one.
 251                  */
 252                 rcu_assign_pointer(keypairs->next_keypair, new_keypair);
 253                 wg_noise_keypair_put(next_keypair, true);
 254                 RCU_INIT_POINTER(keypairs->previous_keypair, NULL);
 255                 wg_noise_keypair_put(previous_keypair, true);
 256         }
 257         spin_unlock_bh(&keypairs->keypair_update_lock);
 258 }
 259
 260 bool wg_noise_received_with_keypair(struct noise_keypairs *keypairs,
 261                                     struct noise_keypair *received_keypair)
 262 {
 263         struct noise_keypair *old_keypair;
 264         bool key_is_new;
 265
 266         /* We first check without taking the spinlock. */
 267         key_is_new = received_keypair ==
 268                      rcu_access_pointer(keypairs->next_keypair);
 269         if (likely(!key_is_new))
 270                 return false;
 271
 272         spin_lock_bh(&keypairs->keypair_update_lock);
 273         /* After locking, we double check that things didn't change from
 274          * beneath us.
 275          */
 276         if (unlikely(received_keypair !=
 277                     rcu_dereference_protected(keypairs->next_keypair,
 278                             lockdep_is_held(&keypairs->keypair_update_lock)))) {
 279                 spin_unlock_bh(&keypairs->keypair_update_lock);
 280                 return false;
 281         }
 282
 283         /* When we've finally received the confirmation, we slide the next
 284          * into the current, the current into the previous, and get rid of
 285          * the old previous.
 286          */
 287         old_keypair = rcu_dereference_protected(keypairs->previous_keypair,
 288                 lockdep_is_held(&keypairs->keypair_update_lock));
 289         rcu_assign_pointer(keypairs->previous_keypair,
 290                 rcu_dereference_protected(keypairs->current_keypair,
 291                         lockdep_is_held(&keypairs->keypair_update_lock)));
 292         wg_noise_keypair_put(old_keypair, true);
 293         rcu_assign_pointer(keypairs->current_keypair, received_keypair);
 294         RCU_INIT_POINTER(keypairs->next_keypair, NULL);
 295
 296         spin_unlock_bh(&keypairs->keypair_update_lock);
 297         return true;
 298 }
 299
 300 /* Must hold static_identity->lock */
 301 void wg_noise_set_static_identity_private_key(
 302         struct noise_static_identity *static_identity,
 303         const u8 private_key[NOISE_PUBLIC_KEY_LEN])
 304 {
 305         memcpy(static_identity->static_private, private_key,
 306                NOISE_PUBLIC_KEY_LEN);
 307         curve25519_clamp_secret(static_identity->static_private);
 308         static_identity->has_identity = curve25519_generate_public(
 309                 static_identity->static_public, private_key);
 310 }
 311
 312 /* This is Hugo Krawczyk's HKDF:
 313  *  - https://eprint.iacr.org/2010/264.pdf
 314  *  - https://tools.ietf.org/html/rfc5869
 315  */
 316 static void kdf(u8 *first_dst, u8 *second_dst, u8 *third_dst, const u8 *data,
 317                 size_t first_len, size_t second_len, size_t third_len,
 318                 size_t data_len, const u8 chaining_key[NOISE_HASH_LEN])
 319 {
 320         u8 output[BLAKE2S_HASH_SIZE + 1];
 321         u8 secret[BLAKE2S_HASH_SIZE];
 322
 323         WARN_ON(IS_ENABLED(DEBUG) &&
 324                 (first_len > BLAKE2S_HASH_SIZE ||
 325                  second_len > BLAKE2S_HASH_SIZE ||
 326                  third_len > BLAKE2S_HASH_SIZE ||
 327                  ((second_len || second_dst || third_len || third_dst) &&
 328                   (!first_len || !first_dst)) ||
 329                  ((third_len || third_dst) && (!second_len || !second_dst))));
 330
 331         /* Extract entropy from data into secret */
 332         blake2s256_hmac(secret, data, chaining_key, data_len, NOISE_HASH_LEN);
 333
 334         if (!first_dst || !first_len)
 335                 goto out;
 336
 337         /* Expand first key: key = secret, data = 0x1 */
 338         output[0] = 1;
 339         blake2s256_hmac(output, output, secret, 1, BLAKE2S_HASH_SIZE);
 340         memcpy(first_dst, output, first_len);
 341
 342         if (!second_dst || !second_len)
 343                 goto out;
 344
 345         /* Expand second key: key = secret, data = first-key || 0x2 */
 346         output[BLAKE2S_HASH_SIZE] = 2;
 347         blake2s256_hmac(output, output, secret, BLAKE2S_HASH_SIZE + 1,
 348                         BLAKE2S_HASH_SIZE);
 349         memcpy(second_dst, output, second_len);
 350
 351         if (!third_dst || !third_len)
 352                 goto out;
 353
 354         /* Expand third key: key = secret, data = second-key || 0x3 */
 355         output[BLAKE2S_HASH_SIZE] = 3;
 356         blake2s256_hmac(output, output, secret, BLAKE2S_HASH_SIZE + 1,
 357                         BLAKE2S_HASH_SIZE);
 358         memcpy(third_dst, output, third_len);
 359
 360 out:
 361         /* Clear sensitive data from stack */
 362         memzero_explicit(secret, BLAKE2S_HASH_SIZE);
 363         memzero_explicit(output, BLAKE2S_HASH_SIZE + 1);
 364 }
 365
 366 static void symmetric_key_init(struct noise_symmetric_key *key)
 367 {
 368         spin_lock_init(&key->counter.receive.lock);
 369         atomic64_set(&key->counter.counter, 0);
 370         memset(key->counter.receive.backtrack, 0,
 371                sizeof(key->counter.receive.backtrack));
 372         key->birthdate = ktime_get_coarse_boottime_ns();
 373         key->is_valid = true;
 374 }
 375
 376 static void derive_keys(struct noise_symmetric_key *first_dst,
 377                         struct noise_symmetric_key *second_dst,
 378                         const u8 chaining_key[NOISE_HASH_LEN])
 379 {
 380         kdf(first_dst->key, second_dst->key, NULL, NULL,
 381             NOISE_SYMMETRIC_KEY_LEN, NOISE_SYMMETRIC_KEY_LEN, 0, 0,
 382             chaining_key);
 383         symmetric_key_init(first_dst);
 384         symmetric_key_init(second_dst);
 385 }
 386
 387 static bool __must_check mix_dh(u8 chaining_key[NOISE_HASH_LEN],
 388                                 u8 key[NOISE_SYMMETRIC_KEY_LEN],
 389                                 const u8 private[NOISE_PUBLIC_KEY_LEN],
 390                                 const u8 public[NOISE_PUBLIC_KEY_LEN])
 391 {
 392         u8 dh_calculation[NOISE_PUBLIC_KEY_LEN];
 393
 394         if (unlikely(!curve25519(dh_calculation, private, public)))
 395                 return false;
 396         kdf(chaining_key, key, NULL, dh_calculation, NOISE_HASH_LEN,
 397             NOISE_SYMMETRIC_KEY_LEN, 0, NOISE_PUBLIC_KEY_LEN, chaining_key);
 398         memzero_explicit(dh_calculation, NOISE_PUBLIC_KEY_LEN);
 399         return true;
 400 }
 401
 402 static void mix_hash(u8 hash[NOISE_HASH_LEN], const u8 *src, size_t src_len)
 403 {
 404         struct blake2s_state blake;
 405
 406         blake2s_init(&blake, NOISE_HASH_LEN);
 407         blake2s_update(&blake, hash, NOISE_HASH_LEN);
 408         blake2s_update(&blake, src, src_len);
 409         blake2s_final(&blake, hash);
 410 }
 411
 412 static void mix_psk(u8 chaining_key[NOISE_HASH_LEN], u8 hash[NOISE_HASH_LEN],
 413                     u8 key[NOISE_SYMMETRIC_KEY_LEN],
 414                     const u8 psk[NOISE_SYMMETRIC_KEY_LEN])
 415 {
 416         u8 temp_hash[NOISE_HASH_LEN];
 417
 418         kdf(chaining_key, temp_hash, key, psk, NOISE_HASH_LEN, NOISE_HASH_LEN,
 419             NOISE_SYMMETRIC_KEY_LEN, NOISE_SYMMETRIC_KEY_LEN, chaining_key);
 420         mix_hash(hash, temp_hash, NOISE_HASH_LEN);
 421         memzero_explicit(temp_hash, NOISE_HASH_LEN);
 422 }
 423
 424 static void handshake_init(u8 chaining_key[NOISE_HASH_LEN],
 425                            u8 hash[NOISE_HASH_LEN],
 426                            const u8 remote_static[NOISE_PUBLIC_KEY_LEN])
 427 {
 428         memcpy(hash, handshake_init_hash, NOISE_HASH_LEN);
 429         memcpy(chaining_key, handshake_init_chaining_key, NOISE_HASH_LEN);
 430         mix_hash(hash, remote_static, NOISE_PUBLIC_KEY_LEN);
 431 }
 432
 433 static void message_encrypt(u8 *dst_ciphertext, const u8 *src_plaintext,
 434                             size_t src_len, u8 key[NOISE_SYMMETRIC_KEY_LEN],
 435                             u8 hash[NOISE_HASH_LEN])
 436 {
 437         chacha20poly1305_encrypt(dst_ciphertext, src_plaintext, src_len, hash,
 438                                  NOISE_HASH_LEN,
 439                                  0 /* Always zero for Noise_IK */, key);
 440         mix_hash(hash, dst_ciphertext, noise_encrypted_len(src_len));
 441 }
 442
 443 static bool message_decrypt(u8 *dst_plaintext, const u8 *src_ciphertext,
 444                             size_t src_len, u8 key[NOISE_SYMMETRIC_KEY_LEN],
 445                             u8 hash[NOISE_HASH_LEN])
 446 {
 447         if (!chacha20poly1305_decrypt(dst_plaintext, src_ciphertext, src_len,
 448                                       hash, NOISE_HASH_LEN,
 449                                       0 /* Always zero for Noise_IK */, key))
 450                 return false;
 451         mix_hash(hash, src_ciphertext, src_len);
 452         return true;
 453 }
 454
 455 static void message_ephemeral(u8 ephemeral_dst[NOISE_PUBLIC_KEY_LEN],
 456                               const u8 ephemeral_src[NOISE_PUBLIC_KEY_LEN],
 457                               u8 chaining_key[NOISE_HASH_LEN],
 458                               u8 hash[NOISE_HASH_LEN])
 459 {
 460         if (ephemeral_dst != ephemeral_src)
 461                 memcpy(ephemeral_dst, ephemeral_src, NOISE_PUBLIC_KEY_LEN);
 462         mix_hash(hash, ephemeral_src, NOISE_PUBLIC_KEY_LEN);
 463         kdf(chaining_key, NULL, NULL, ephemeral_src, NOISE_HASH_LEN, 0, 0,
 464             NOISE_PUBLIC_KEY_LEN, chaining_key);
 465 }
 466
 467 static void tai64n_now(u8 output[NOISE_TIMESTAMP_LEN])
 468 {
 469         struct timespec64 now;
 470
 471         ktime_get_real_ts64(&now);
 472
 473         /* In order to prevent some sort of infoleak from precise timers, we
 474          * round down the nanoseconds part to the closest rounded-down power of
 475          * two to the maximum initiations per second allowed anyway by the
 476          * implementation.
 477          */
 478         now.tv_nsec = ALIGN_DOWN(now.tv_nsec,
 479                 rounddown_pow_of_two(NSEC_PER_SEC / INITIATIONS_PER_SECOND));
 480
 481         /* https://cr.yp.to/libtai/tai64.html */
 482         *(__be64 *)output = cpu_to_be64(0x400000000000000aULL + now.tv_sec);
 483         *(__be32 *)(output + sizeof(__be64)) = cpu_to_be32(now.tv_nsec);
 484 }
 485
 486 bool
 487 wg_noise_handshake_create_initiation(struct message_handshake_initiation *dst,
 488                                      struct noise_handshake *handshake)
 489 {
 490         u8 timestamp[NOISE_TIMESTAMP_LEN];
 491         u8 key[NOISE_SYMMETRIC_KEY_LEN];
 492         bool ret = false;
 493
 494         /* We need to wait for crng _before_ taking any locks, since
 495          * curve25519_generate_secret uses get_random_bytes_wait.
 496          */
 497         wait_for_random_bytes();
 498
 499         down_read(&handshake->static_identity->lock);
 500         down_write(&handshake->lock);
 501
 502         if (unlikely(!handshake->static_identity->has_identity))
 503                 goto out;
 504
 505         dst->header.type = cpu_to_le32(MESSAGE_HANDSHAKE_INITIATION);
 506
 507         handshake_init(handshake->chaining_key, handshake->hash,
 508                        handshake->remote_static);
 509
 510         /* e */
 511         curve25519_generate_secret(handshake->ephemeral_private);
 512         if (!curve25519_generate_public(dst->unencrypted_ephemeral,
 513                                         handshake->ephemeral_private))
 514                 goto out;
 515         message_ephemeral(dst->unencrypted_ephemeral,
 516                           dst->unencrypted_ephemeral, handshake->chaining_key,
 517                           handshake->hash);
 518
 519         /* es */
 520         if (!mix_dh(handshake->chaining_key, key, handshake->ephemeral_private,
 521                     handshake->remote_static))
 522                 goto out;
 523
 524         /* s */
 525         message_encrypt(dst->encrypted_static,
 526                         handshake->static_identity->static_public,
 527                         NOISE_PUBLIC_KEY_LEN, key, handshake->hash);
 528
 529         /* ss */
 530         kdf(handshake->chaining_key, key, NULL,
 531             handshake->precomputed_static_static, NOISE_HASH_LEN,
 532             NOISE_SYMMETRIC_KEY_LEN, 0, NOISE_PUBLIC_KEY_LEN,
 533             handshake->chaining_key);
 534
 535         /* {t} */
 536         tai64n_now(timestamp);
 537         message_encrypt(dst->encrypted_timestamp, timestamp,
 538                         NOISE_TIMESTAMP_LEN, key, handshake->hash);
 539
 540         dst->sender_index = wg_index_hashtable_insert(
 541                 handshake->entry.peer->device->index_hashtable,
 542                 &handshake->entry);
 543
 544         handshake->state = HANDSHAKE_CREATED_INITIATION;
 545         ret = true;
 546
 547 out:
 548         up_write(&handshake->lock);
 549         up_read(&handshake->static_identity->lock);
 550         memzero_explicit(key, NOISE_SYMMETRIC_KEY_LEN);
 551         return ret;
 552 }
 553
 554 struct wg_peer *
 555 wg_noise_handshake_consume_initiation(struct message_handshake_initiation *src,
 556                                       struct wg_device *wg)
 557 {
 558         struct wg_peer *peer = NULL, *ret_peer = NULL;
 559         struct noise_handshake *handshake;
 560         bool replay_attack, flood_attack;
 561         u8 key[NOISE_SYMMETRIC_KEY_LEN];
 562         u8 chaining_key[NOISE_HASH_LEN];
 563         u8 hash[NOISE_HASH_LEN];
 564         u8 s[NOISE_PUBLIC_KEY_LEN];
 565         u8 e[NOISE_PUBLIC_KEY_LEN];
 566         u8 t[NOISE_TIMESTAMP_LEN];
 567         u64 initiation_consumption;
 568
 569         down_read(&wg->static_identity.lock);
 570         if (unlikely(!wg->static_identity.has_identity))
 571                 goto out;
 572
 573         handshake_init(chaining_key, hash, wg->static_identity.static_public);
 574
 575         /* e */
 576         message_ephemeral(e, src->unencrypted_ephemeral, chaining_key, hash);
 577
 578         /* es */
 579         if (!mix_dh(chaining_key, key, wg->static_identity.static_private, e))
 580                 goto out;
 581
 582         /* s */
 583         if (!message_decrypt(s, src->encrypted_static,
 584                              sizeof(src->encrypted_static), key, hash))
 585                 goto out;
 586
 587         /* Lookup which peer we're actually talking to */
 588         peer = wg_pubkey_hashtable_lookup(wg->peer_hashtable, s);
 589         if (!peer)
 590                 goto out;
 591         handshake = &peer->handshake;
 592
 593         /* ss */
 594         kdf(chaining_key, key, NULL, handshake->precomputed_static_static,
 595             NOISE_HASH_LEN, NOISE_SYMMETRIC_KEY_LEN, 0, NOISE_PUBLIC_KEY_LEN,
 596             chaining_key);
 597
 598         /* {t} */
 599         if (!message_decrypt(t, src->encrypted_timestamp,
 600                              sizeof(src->encrypted_timestamp), key, hash))
 601                 goto out;
 602
 603         down_read(&handshake->lock);
 604         replay_attack = memcmp(t, handshake->latest_timestamp,
 605                                NOISE_TIMESTAMP_LEN) <= 0;
 606         flood_attack = (s64)handshake->last_initiation_consumption +
 607                                NSEC_PER_SEC / INITIATIONS_PER_SECOND >
 608                        (s64)ktime_get_coarse_boottime_ns();
 609         up_read(&handshake->lock);
 610         if (replay_attack || flood_attack)
 611                 goto out;
 612
 613         /* Success! Copy everything to peer */
 614         down_write(&handshake->lock);
 615         memcpy(handshake->remote_ephemeral, e, NOISE_PUBLIC_KEY_LEN);
 616         if (memcmp(t, handshake->latest_timestamp, NOISE_TIMESTAMP_LEN) > 0)
 617                 memcpy(handshake->latest_timestamp, t, NOISE_TIMESTAMP_LEN);
 618         memcpy(handshake->hash, hash, NOISE_HASH_LEN);
 619         memcpy(handshake->chaining_key, chaining_key, NOISE_HASH_LEN);
 620         handshake->remote_index = src->sender_index;
 621         if ((s64)(handshake->last_initiation_consumption -
 622             (initiation_consumption = ktime_get_coarse_boottime_ns())) < 0)
 623                 handshake->last_initiation_consumption = initiation_consumption;
 624         handshake->state = HANDSHAKE_CONSUMED_INITIATION;
 625         up_write(&handshake->lock);
 626         ret_peer = peer;
 627
 628 out:
 629         memzero_explicit(key, NOISE_SYMMETRIC_KEY_LEN);
 630         memzero_explicit(hash, NOISE_HASH_LEN);
 631         memzero_explicit(chaining_key, NOISE_HASH_LEN);
 632         up_read(&wg->static_identity.lock);
 633         if (!ret_peer)
 634                 wg_peer_put(peer);
 635         return ret_peer;
 636 }
 637
 638 bool wg_noise_handshake_create_response(struct message_handshake_response *dst,
 639                                         struct noise_handshake *handshake)
 640 {
 641         u8 key[NOISE_SYMMETRIC_KEY_LEN];
 642         bool ret = false;
 643
 644         /* We need to wait for crng _before_ taking any locks, since
 645          * curve25519_generate_secret uses get_random_bytes_wait.
 646          */
 647         wait_for_random_bytes();
 648
 649         down_read(&handshake->static_identity->lock);
 650         down_write(&handshake->lock);
 651
 652         if (handshake->state != HANDSHAKE_CONSUMED_INITIATION)
 653                 goto out;
 654
 655         dst->header.type = cpu_to_le32(MESSAGE_HANDSHAKE_RESPONSE);
 656         dst->receiver_index = handshake->remote_index;
 657
 658         /* e */
 659         curve25519_generate_secret(handshake->ephemeral_private);
 660         if (!curve25519_generate_public(dst->unencrypted_ephemeral,
 661                                         handshake->ephemeral_private))
 662                 goto out;
 663         message_ephemeral(dst->unencrypted_ephemeral,
 664                           dst->unencrypted_ephemeral, handshake->chaining_key,
 665                           handshake->hash);
 666
 667         /* ee */
 668         if (!mix_dh(handshake->chaining_key, NULL, handshake->ephemeral_private,
 669                     handshake->remote_ephemeral))
 670                 goto out;
 671
 672         /* se */
 673         if (!mix_dh(handshake->chaining_key, NULL, handshake->ephemeral_private,
 674                     handshake->remote_static))
 675                 goto out;
 676
 677         /* psk */
 678         mix_psk(handshake->chaining_key, handshake->hash, key,
 679                 handshake->preshared_key);
 680
 681         /* {} */
 682         message_encrypt(dst->encrypted_nothing, NULL, 0, key, handshake->hash);
 683
 684         dst->sender_index = wg_index_hashtable_insert(
 685                 handshake->entry.peer->device->index_hashtable,
 686                 &handshake->entry);
 687
 688         handshake->state = HANDSHAKE_CREATED_RESPONSE;
 689         ret = true;
 690
 691 out:
 692         up_write(&handshake->lock);
 693         up_read(&handshake->static_identity->lock);
 694         memzero_explicit(key, NOISE_SYMMETRIC_KEY_LEN);
 695         return ret;
 696 }
 697
 698 struct wg_peer *
 699 wg_noise_handshake_consume_response(struct message_handshake_response *src,
 700                                     struct wg_device *wg)
 701 {
 702         enum noise_handshake_state state = HANDSHAKE_ZEROED;
 703         struct wg_peer *peer = NULL, *ret_peer = NULL;
 704         struct noise_handshake *handshake;
 705         u8 key[NOISE_SYMMETRIC_KEY_LEN];
 706         u8 hash[NOISE_HASH_LEN];
 707         u8 chaining_key[NOISE_HASH_LEN];
 708         u8 e[NOISE_PUBLIC_KEY_LEN];
 709         u8 ephemeral_private[NOISE_PUBLIC_KEY_LEN];
 710         u8 static_private[NOISE_PUBLIC_KEY_LEN];
 711
 712         down_read(&wg->static_identity.lock);
 713
 714         if (unlikely(!wg->static_identity.has_identity))
 715                 goto out;
 716
 717         handshake = (struct noise_handshake *)wg_index_hashtable_lookup(
 718                 wg->index_hashtable, INDEX_HASHTABLE_HANDSHAKE,
 719                 src->receiver_index, &peer);
 720         if (unlikely(!handshake))
 721                 goto out;
 722
 723         down_read(&handshake->lock);
 724         state = handshake->state;
 725         memcpy(hash, handshake->hash, NOISE_HASH_LEN);
 726         memcpy(chaining_key, handshake->chaining_key, NOISE_HASH_LEN);
 727         memcpy(ephemeral_private, handshake->ephemeral_private,
 728                NOISE_PUBLIC_KEY_LEN);
 729         up_read(&handshake->lock);
 730
 731         if (state != HANDSHAKE_CREATED_INITIATION)
 732                 goto fail;
 733
 734         /* e */
 735         message_ephemeral(e, src->unencrypted_ephemeral, chaining_key, hash);
 736
 737         /* ee */
 738         if (!mix_dh(chaining_key, NULL, ephemeral_private, e))
 739                 goto fail;
 740
 741         /* se */
 742         if (!mix_dh(chaining_key, NULL, wg->static_identity.static_private, e))
 743                 goto fail;
 744
 745         /* psk */
 746         mix_psk(chaining_key, hash, key, handshake->preshared_key);
 747
 748         /* {} */
 749         if (!message_decrypt(NULL, src->encrypted_nothing,
 750                              sizeof(src->encrypted_nothing), key, hash))
 751                 goto fail;
 752
 753         /* Success! Copy everything to peer */
 754         down_write(&handshake->lock);
 755         /* It's important to check that the state is still the same, while we
 756          * have an exclusive lock.
 757          */
 758         if (handshake->state != state) {
 759                 up_write(&handshake->lock);
 760                 goto fail;
 761         }
 762         memcpy(handshake->remote_ephemeral, e, NOISE_PUBLIC_KEY_LEN);
 763         memcpy(handshake->hash, hash, NOISE_HASH_LEN);
 764         memcpy(handshake->chaining_key, chaining_key, NOISE_HASH_LEN);
 765         handshake->remote_index = src->sender_index;
 766         handshake->state = HANDSHAKE_CONSUMED_RESPONSE;
 767         up_write(&handshake->lock);
 768         ret_peer = peer;
 769         goto out;
 770
 771 fail:
 772         wg_peer_put(peer);
 773 out:
 774         memzero_explicit(key, NOISE_SYMMETRIC_KEY_LEN);
 775         memzero_explicit(hash, NOISE_HASH_LEN);
 776         memzero_explicit(chaining_key, NOISE_HASH_LEN);
 777         memzero_explicit(ephemeral_private, NOISE_PUBLIC_KEY_LEN);
 778         memzero_explicit(static_private, NOISE_PUBLIC_KEY_LEN);
 779         up_read(&wg->static_identity.lock);
 780         return ret_peer;
 781 }
 782
 783 bool wg_noise_handshake_begin_session(struct noise_handshake *handshake,
 784                                       struct noise_keypairs *keypairs)
 785 {
 786         struct noise_keypair *new_keypair;
 787         bool ret = false;
 788
 789         down_write(&handshake->lock);
 790         if (handshake->state != HANDSHAKE_CREATED_RESPONSE &&
 791             handshake->state != HANDSHAKE_CONSUMED_RESPONSE)
 792                 goto out;
 793
 794         new_keypair = keypair_create(handshake->entry.peer);
 795         if (!new_keypair)
 796                 goto out;
 797         new_keypair->i_am_the_initiator = handshake->state ==
 798                                           HANDSHAKE_CONSUMED_RESPONSE;
 799         new_keypair->remote_index = handshake->remote_index;
 800
 801         if (new_keypair->i_am_the_initiator)
 802                 derive_keys(&new_keypair->sending, &new_keypair->receiving,
 803                             handshake->chaining_key);
 804         else
 805                 derive_keys(&new_keypair->receiving, &new_keypair->sending,
 806                             handshake->chaining_key);
 807
 808         handshake_zero(handshake);
 809         rcu_read_lock_bh();
 810         if (likely(!READ_ONCE(container_of(handshake, struct wg_peer,
 811                                            handshake)->is_dead))) {
 812                 add_new_keypair(keypairs, new_keypair);
 813                 net_dbg_ratelimited("%s: Keypair %llu created for peer %llu\n",
 814                                     handshake->entry.peer->device->dev->name,
 815                                     new_keypair->internal_id,
 816                                     handshake->entry.peer->internal_id);
 817                 ret = wg_index_hashtable_replace(
 818                         handshake->entry.peer->device->index_hashtable,
 819                         &handshake->entry, &new_keypair->entry);
 820         } else {
 821                 kzfree(new_keypair);
 822         }
 823         rcu_read_unlock_bh();
 824
 825 out:
 826         up_write(&handshake->lock);
 827         return ret;
 828 }