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