onion.c 32.7 KB
Newer Older
Roger Dingledine's avatar
Roger Dingledine committed
1
2
/* Copyright (c) 2001 Matej Pfajfar.
 * Copyright (c) 2001-2004, Roger Dingledine.
3
 * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
4
 * Copyright (c) 2007-2012, The Tor Project, Inc. */
5
/* See LICENSE for licensing information */
Roger Dingledine's avatar
Roger Dingledine committed
6

7
8
/**
 * \file onion.c
9
10
 * \brief Functions to queue create cells, wrap the various onionskin types,
 * and parse and create the CREATE cell and its allies.
11
12
 **/

Roger Dingledine's avatar
Roger Dingledine committed
13
#include "or.h"
Sebastian Hahn's avatar
Sebastian Hahn committed
14
#include "circuitlist.h"
Sebastian Hahn's avatar
Sebastian Hahn committed
15
#include "config.h"
16
#include "cpuworker.h"
Sebastian Hahn's avatar
Sebastian Hahn committed
17
#include "onion.h"
18
19
20
#include "onion_fast.h"
#include "onion_ntor.h"
#include "onion_tap.h"
21
#include "relay.h"
Sebastian Hahn's avatar
Sebastian Hahn committed
22
#include "rephist.h"
23
#include "router.h"
Roger Dingledine's avatar
Roger Dingledine committed
24

25
26
/** Type for a linked list of circuits that are waiting for a free CPU worker
 * to process a waiting onion handshake. */
27
typedef struct onion_queue_t {
28
  or_circuit_t *circ;
29
  create_cell_t *onionskin;
30
  time_t when_added;
Roger Dingledine's avatar
Roger Dingledine committed
31
  struct onion_queue_t *next;
32
} onion_queue_t;
Roger Dingledine's avatar
Roger Dingledine committed
33

34
35
36
/** 5 seconds on the onion queue til we just send back a destroy */
#define ONIONQUEUE_WAIT_CUTOFF 5

Roger Dingledine's avatar
Roger Dingledine committed
37
/** First and last elements in the linked list of circuits waiting for CPU
38
39
 * workers, or NULL if the list is empty.
 * @{ */
40
41
static onion_queue_t *ol_list=NULL;
static onion_queue_t *ol_tail=NULL;
42
/**@}*/
43

44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
/** Number of entries of each type currently in ol_list. */
static int ol_entries[MAX_ONION_HANDSHAKE_TYPE+1];

/* XXXX024 Check lengths vs MAX_ONIONSKIN_{CHALLENGE,REPLY}_LEN.
 *
 * (By which I think I meant, "make sure that no
 * X_ONIONSKIN_CHALLENGE/REPLY_LEN is greater than
 * MAX_ONIONSKIN_CHALLENGE/REPLY_LEN."  Also, make sure that we can pass
 * over-large values via EXTEND2/EXTENDED2, for future-compatibility.*/

/** Return true iff we have room to queue another oninoskin of type
 * <b>type</b>. */
static int
have_room_for_onionskin(uint16_t type)
{
  const or_options_t *options = get_options();
  int num_cpus;
  uint64_t tap_usec, ntor_usec;
  /* If we've got fewer than 50 entries, we always have room for one more. */
  if (ol_entries[ONION_HANDSHAKE_TYPE_TAP] +
      ol_entries[ONION_HANDSHAKE_TYPE_NTOR] < 50)
    return 1;
  num_cpus = get_num_cpus(options);
  /* Compute how many microseconds we'd expect to need to clear all
   * onionskins in the current queue. */
  tap_usec  = estimated_usec_for_onionskins(
                                    ol_entries[ONION_HANDSHAKE_TYPE_TAP],
                                    ONION_HANDSHAKE_TYPE_TAP) / num_cpus;
  ntor_usec = estimated_usec_for_onionskins(
                                    ol_entries[ONION_HANDSHAKE_TYPE_NTOR],
                                    ONION_HANDSHAKE_TYPE_NTOR) / num_cpus;
  /* See whether that exceeds MaxOnionQueueDelay. If so, we can't queue
   * this. */
  if ((tap_usec + ntor_usec) / 1000 > (uint64_t)options->MaxOnionQueueDelay)
    return 0;
#ifdef CURVE25519_ENABLED
  /* If we support the ntor handshake, then don't let TAP handshakes use
   * more than 2/3 of the space on the queue. */
  if (type == ONION_HANDSHAKE_TYPE_TAP &&
      tap_usec / 1000 > (uint64_t)options->MaxOnionQueueDelay * 2 / 3)
    return 0;
#endif

  return 1;
}
89

90
91
92
/** Add <b>circ</b> to the end of ol_list and return 0, except
 * if ol_list is too long, in which case do nothing and return -1.
 */
93
int
94
onion_pending_add(or_circuit_t *circ, create_cell_t *onionskin)
95
{
96
  onion_queue_t *tmp;
97
  time_t now = time(NULL);
98

99
  tmp = tor_malloc_zero(sizeof(onion_queue_t));
100
  tmp->circ = circ;
101
  tmp->onionskin = onionskin;
102
  tmp->when_added = now;
103

104
  if (!ol_tail) {
Roger Dingledine's avatar
Roger Dingledine committed
105
    tor_assert(!ol_list);
106
107
    ol_list = tmp;
    ol_tail = tmp;
108
    ++ol_entries[onionskin->handshake_type];
109
110
111
    return 0;
  }

Roger Dingledine's avatar
Roger Dingledine committed
112
113
  tor_assert(ol_list);
  tor_assert(!ol_tail->next);
114

115
  if (!have_room_for_onionskin(onionskin->handshake_type)) {
Karsten Loesing's avatar
Karsten Loesing committed
116
#define WARN_TOO_MANY_CIRC_CREATIONS_INTERVAL (60)
117
118
119
120
    static ratelim_t last_warned =
      RATELIM_INIT(WARN_TOO_MANY_CIRC_CREATIONS_INTERVAL);
    char *m;
    if ((m = rate_limit_log(&last_warned, approx_time()))) {
Karsten Loesing's avatar
Karsten Loesing committed
121
122
123
124
      log_warn(LD_GENERAL,
               "Your computer is too slow to handle this many circuit "
               "creation requests! Please consider using the "
               "MaxAdvertisedBandwidth config option or choosing a more "
125
126
               "restricted exit policy.%s",m);
      tor_free(m);
Karsten Loesing's avatar
Karsten Loesing committed
127
    }
Roger Dingledine's avatar
Roger Dingledine committed
128
    tor_free(tmp);
129
130
131
    return -1;
  }

132
  ++ol_entries[onionskin->handshake_type];
133
134
  ol_tail->next = tmp;
  ol_tail = tmp;
135
136
137
138
  while ((int)(now - ol_list->when_added) >= ONIONQUEUE_WAIT_CUTOFF) {
    /* cull elderly requests. */
    circ = ol_list->circ;
    onion_pending_remove(ol_list->circ);
139
    log_info(LD_CIRC,
Nick Mathewson's avatar
Nick Mathewson committed
140
             "Circuit create request is too old; canceling due to overload.");
141
    circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_RESOURCELIMIT);
142
  }
143
144
145
  return 0;
}

146
147
148
/** Remove the first item from ol_list and return it, or return
 * NULL if the list is empty.
 */
149
or_circuit_t *
150
onion_next_task(create_cell_t **onionskin_out)
151
{
152
  or_circuit_t *circ;
153

154
  if (!ol_list)
Roger Dingledine's avatar
Roger Dingledine committed
155
    return NULL; /* no onions pending, we're done */
156

Roger Dingledine's avatar
Roger Dingledine committed
157
  tor_assert(ol_list->circ);
158
  tor_assert(ol_list->circ->p_chan); /* make sure it's still valid */
159
  circ = ol_list->circ;
160
161
162
  if (ol_list->onionskin &&
      ol_list->onionskin->handshake_type <= MAX_ONION_HANDSHAKE_TYPE)
    --ol_entries[ol_list->onionskin->handshake_type];
163
164
  *onionskin_out = ol_list->onionskin;
  ol_list->onionskin = NULL; /* prevent free. */
165
166
  onion_pending_remove(ol_list->circ);
  return circ;
167
168
}

169
170
/** Go through ol_list, find the onion_queue_t element which points to
 * circ, remove and free that element. Leave circ itself alone.
171
 */
172
void
173
onion_pending_remove(or_circuit_t *circ)
174
{
175
  onion_queue_t *tmpo, *victim;
176

177
  if (!ol_list)
178
179
180
181
    return; /* nothing here. */

  /* first check to see if it's the first entry */
  tmpo = ol_list;
182
  if (tmpo->circ == circ) {
183
184
    /* it's the first one. remove it from the list. */
    ol_list = tmpo->next;
185
    if (!ol_list)
186
187
188
      ol_tail = NULL;
    victim = tmpo;
  } else { /* we need to hunt through the rest of the list */
189
190
    for ( ;tmpo->next && tmpo->next->circ != circ; tmpo=tmpo->next) ;
    if (!tmpo->next) {
191
192
193
      log_debug(LD_GENERAL,
                "circ (p_circ_id %d) not in list, probably at cpuworker.",
                circ->p_circ_id);
194
195
196
197
198
      return;
    }
    /* now we know tmpo->next->circ == circ */
    victim = tmpo->next;
    tmpo->next = victim->next;
199
    if (ol_tail == victim)
200
201
202
      ol_tail = tmpo;
  }

203
204
205
206
  if (victim->onionskin &&
      victim->onionskin->handshake_type <= MAX_ONION_HANDSHAKE_TYPE)
    --ol_entries[victim->onionskin->handshake_type];

207
208
  /* now victim points to the element that needs to be removed */

209
  tor_free(victim->onionskin);
Roger Dingledine's avatar
Roger Dingledine committed
210
  tor_free(victim);
211
212
}

213
214
215
216
217
/** Remove all circuits from the pending list.  Called from tor_free_all. */
void
clear_pending_onions(void)
{
  while (ol_list) {
218
    onion_queue_t *victim = ol_list;
219
    ol_list = victim->next;
220
    tor_free(victim->onionskin);
221
222
223
    tor_free(victim);
  }
  ol_list = ol_tail = NULL;
224
  memset(ol_entries, 0, sizeof(ol_entries));
225
}
226

227
228
229
230
231
232
233
234
235
236
237
238
239
240
/* ============================================================ */

/** Fill in a server_onion_keys_t object at <b>keys</b> with all of the keys
 * and other info we might need to do onion handshakes.  (We make a copy of
 * our keys for each cpuworker to avoid race conditions with the main thread,
 * and to avoid locking) */
void
setup_server_onion_keys(server_onion_keys_t *keys)
{
  memset(keys, 0, sizeof(server_onion_keys_t));
  memcpy(keys->my_identity, router_get_my_id_digest(), DIGEST_LEN);
  dup_onion_keys(&keys->onion_key, &keys->last_onion_key);
#ifdef CURVE25519_ENABLED
  keys->curve25519_key_map = construct_ntor_key_map();
241
242
  keys->junk_keypair = tor_malloc_zero(sizeof(curve25519_keypair_t));
  curve25519_keypair_generate(keys->junk_keypair, 0);
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
#endif
}

/** Release all storage held in <b>keys</b>, but do not free <b>keys</b>
 * itself (as it's likely to be stack-allocated.) */
void
release_server_onion_keys(server_onion_keys_t *keys)
{
  if (! keys)
    return;

  crypto_pk_free(keys->onion_key);
  crypto_pk_free(keys->last_onion_key);
#ifdef CURVE25519_ENABLED
  ntor_key_map_free(keys->curve25519_key_map);
258
  tor_free(keys->junk_keypair);
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
#endif
  memset(keys, 0, sizeof(server_onion_keys_t));
}

/** Release whatever storage is held in <b>state</b>, depending on its
 * type, and clear its pointer. */
void
onion_handshake_state_release(onion_handshake_state_t *state)
{
  switch (state->tag) {
  case ONION_HANDSHAKE_TYPE_TAP:
    crypto_dh_free(state->u.tap);
    state->u.tap = NULL;
    break;
  case ONION_HANDSHAKE_TYPE_FAST:
    fast_handshake_state_free(state->u.fast);
    state->u.fast = NULL;
    break;
#ifdef CURVE25519_ENABLED
  case ONION_HANDSHAKE_TYPE_NTOR:
    ntor_handshake_state_free(state->u.ntor);
    state->u.ntor = NULL;
    break;
#endif
  default:
    log_warn(LD_BUG, "called with unknown handshake state type %d",
             (int)state->tag);
    tor_fragile_assert();
  }
}

/** Perform the first step of a circuit-creation handshake of type <b>type</b>
 * (one of ONION_HANDSHAKE_TYPE_*): generate the initial "onion skin" in
 * <b>onion_skin_out</b>, and store any state information in <b>state_out</b>.
 * Return -1 on failure, and the length of the onionskin on acceptance.
 */
int
onion_skin_create(int type,
                  const extend_info_t *node,
                  onion_handshake_state_t *state_out,
                  uint8_t *onion_skin_out)
{
  int r = -1;

  switch (type) {
  case ONION_HANDSHAKE_TYPE_TAP:
    if (!node->onion_key)
      return -1;

    if (onion_skin_TAP_create(node->onion_key,
                              &state_out->u.tap,
                              (char*)onion_skin_out) < 0)
      return -1;

    r = TAP_ONIONSKIN_CHALLENGE_LEN;
    break;
  case ONION_HANDSHAKE_TYPE_FAST:
    if (fast_onionskin_create(&state_out->u.fast, onion_skin_out) < 0)
      return -1;

    r = CREATE_FAST_LEN;
    break;
  case ONION_HANDSHAKE_TYPE_NTOR:
#ifdef CURVE25519_ENABLED
    if (tor_mem_is_zero((const char*)node->curve25519_onion_key.public_key,
                        CURVE25519_PUBKEY_LEN))
      return -1;
    if (onion_skin_ntor_create((const uint8_t*)node->identity_digest,
                               &node->curve25519_onion_key,
                               &state_out->u.ntor,
                               onion_skin_out) < 0)
      return -1;

    r = NTOR_ONIONSKIN_LEN;
#else
    return -1;
#endif
    break;
  default:
    log_warn(LD_BUG, "called with unknown handshake state type %d", type);
    tor_fragile_assert();
    r = -1;
  }

  if (r > 0)
    state_out->tag = (uint16_t) type;

  return r;
}

/** Perform the second (server-side) step of a circuit-creation handshake of
 * type <b>type</b>, responding to the client request in <b>onion_skin</b>
 * using the keys in <b>keys</b>.  On success, write our response into
 * <b>reply_out</b>, generate <b>keys_out_len</b> bytes worth of key material
353
354
 * in <b>keys_out_len</b>, a hidden service nonce to <b>rend_nonce_out</b>,
 * and return the length of the reply. On failure, return -1.
355
 */
356
357
int
onion_skin_server_handshake(int type,
358
                      const uint8_t *onion_skin, size_t onionskin_len,
359
360
                      const server_onion_keys_t *keys,
                      uint8_t *reply_out,
361
362
                      uint8_t *keys_out, size_t keys_out_len,
                      uint8_t *rend_nonce_out)
363
364
365
366
367
{
  int r = -1;

  switch (type) {
  case ONION_HANDSHAKE_TYPE_TAP:
368
369
    if (onionskin_len != TAP_ONIONSKIN_CHALLENGE_LEN)
      return -1;
370
371
372
373
374
375
    if (onion_skin_TAP_server_handshake((const char*)onion_skin,
                                        keys->onion_key, keys->last_onion_key,
                                        (char*)reply_out,
                                        (char*)keys_out, keys_out_len)<0)
      return -1;
    r = TAP_ONIONSKIN_REPLY_LEN;
376
    memcpy(rend_nonce_out, reply_out+DH_KEY_LEN, DIGEST_LEN);
377
378
    break;
  case ONION_HANDSHAKE_TYPE_FAST:
379
380
    if (onionskin_len != CREATE_FAST_LEN)
      return -1;
381
382
383
    if (fast_server_handshake(onion_skin, reply_out, keys_out, keys_out_len)<0)
      return -1;
    r = CREATED_FAST_LEN;
384
    memcpy(rend_nonce_out, reply_out+DIGEST_LEN, DIGEST_LEN);
385
386
387
    break;
  case ONION_HANDSHAKE_TYPE_NTOR:
#ifdef CURVE25519_ENABLED
388
    if (onionskin_len < NTOR_ONIONSKIN_LEN)
389
      return -1;
390
391
392
393
394
395
    {
      size_t keys_tmp_len = keys_out_len + DIGEST_LEN;
      uint8_t *keys_tmp = tor_malloc(keys_out_len + DIGEST_LEN);

      if (onion_skin_ntor_server_handshake(
                                   onion_skin, keys->curve25519_key_map,
396
                                   keys->junk_keypair,
397
398
399
400
401
402
403
404
405
406
407
                                   keys->my_identity,
                                   reply_out, keys_tmp, keys_tmp_len)<0) {
        tor_free(keys_tmp);
        return -1;
      }
      memcpy(keys_out, keys_tmp, keys_out_len);
      memcpy(rend_nonce_out, keys_tmp+keys_out_len, DIGEST_LEN);
      memwipe(keys_tmp, 0, keys_tmp_len);
      tor_free(keys_tmp);
      r = NTOR_REPLY_LEN;
    }
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
#else
    return -1;
#endif
    break;
  default:
    log_warn(LD_BUG, "called with unknown handshake state type %d", type);
    tor_fragile_assert();
    return -1;
  }

  return r;
}

/** Perform the final (client-side) step of a circuit-creation handshake of
 * type <b>type</b>, using our state in <b>handshake_state</b> and the
 * server's response in <b>reply</b> On success, generate <b>keys_out_len</b>
 * bytes worth of key material in <b>keys_out_len</b>, set
 * <b>rend_authenticator_out</b> to the "KH" field that can be used to
 * establish introduction points at this hop, and return 0.  On failure,
 * return -1. */
int
onion_skin_client_handshake(int type,
                      const onion_handshake_state_t *handshake_state,
431
                      const uint8_t *reply, size_t reply_len,
432
433
434
435
436
437
438
439
                      uint8_t *keys_out, size_t keys_out_len,
                      uint8_t *rend_authenticator_out)
{
  if (handshake_state->tag != type)
    return -1;

  switch (type) {
  case ONION_HANDSHAKE_TYPE_TAP:
440
441
    if (reply_len != TAP_ONIONSKIN_REPLY_LEN)
      return -1;
442
443
444
445
446
447
448
449
450
    if (onion_skin_TAP_client_handshake(handshake_state->u.tap,
                                        (const char*)reply,
                                        (char *)keys_out, keys_out_len) < 0)
      return -1;

    memcpy(rend_authenticator_out, reply+DH_KEY_LEN, DIGEST_LEN);

    return 0;
  case ONION_HANDSHAKE_TYPE_FAST:
451
452
    if (reply_len != CREATED_FAST_LEN)
      return -1;
453
454
455
456
457
458
459
460
    if (fast_client_handshake(handshake_state->u.fast, reply,
                              keys_out, keys_out_len) < 0)
      return -1;

    memcpy(rend_authenticator_out, reply+DIGEST_LEN, DIGEST_LEN);
    return 0;
#ifdef CURVE25519_ENABLED
  case ONION_HANDSHAKE_TYPE_NTOR:
461
    if (reply_len < NTOR_REPLY_LEN)
462
      return -1;
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
    {
      size_t keys_tmp_len = keys_out_len + DIGEST_LEN;
      uint8_t *keys_tmp = tor_malloc(keys_tmp_len);
      if (onion_skin_ntor_client_handshake(handshake_state->u.ntor,
                                           reply,
                                           keys_tmp, keys_tmp_len) < 0) {
        tor_free(keys_tmp);
        return -1;
      }
      memcpy(keys_out, keys_tmp, keys_out_len);
      memcpy(rend_authenticator_out, keys_tmp + keys_out_len, DIGEST_LEN);
      memwipe(keys_tmp, 0, keys_tmp_len);
      tor_free(keys_tmp);
    }
    return 0;
#endif
  default:
    log_warn(LD_BUG, "called with unknown handshake state type %d", type);
    tor_fragile_assert();
    return -1;
  }
}

486
487
488
489
490
491
492
493
/** Helper: return 0 if <b>cell</b> appears valid, -1 otherwise. If
 * <b>unknown_ok</b> is true, allow cells with handshake types we don't
 * recognize. */
static int
check_create_cell(const create_cell_t *cell, int unknown_ok)
{
  switch (cell->cell_type) {
  case CELL_CREATE:
494
495
    if (cell->handshake_type != ONION_HANDSHAKE_TYPE_TAP &&
        cell->handshake_type != ONION_HANDSHAKE_TYPE_NTOR)
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
      return -1;
    break;
  case CELL_CREATE_FAST:
    if (cell->handshake_type != ONION_HANDSHAKE_TYPE_FAST)
      return -1;
    break;
  case CELL_CREATE2:
    break;
  default:
    return -1;
  }

  switch (cell->handshake_type) {
  case ONION_HANDSHAKE_TYPE_TAP:
    if (cell->handshake_len != TAP_ONIONSKIN_CHALLENGE_LEN)
      return -1;
    break;
  case ONION_HANDSHAKE_TYPE_FAST:
    if (cell->handshake_len != CREATE_FAST_LEN)
      return -1;
    break;
#ifdef CURVE25519_ENABLED
  case ONION_HANDSHAKE_TYPE_NTOR:
    if (cell->handshake_len != NTOR_ONIONSKIN_LEN)
      return -1;
    break;
#endif
  default:
    if (! unknown_ok)
      return -1;
  }

  return 0;
}

/** Helper: parse the CREATE2 payload at <b>p</b>, which could be up to
 * <b>p_len</b> bytes long, and use it to fill the fields of
 * <b>cell_out</b>. Return 0 on success and -1 on failure.
 *
 * Note that part of the body of an EXTEND2 cell is a CREATE2 payload, so
 * this function is also used for parsing those.
 */
static int
parse_create2_payload(create_cell_t *cell_out, const uint8_t *p, size_t p_len)
{
  if (p_len < 4)
    return -1;
  cell_out->cell_type = CELL_CREATE2;
  cell_out->handshake_type = ntohs(get_uint16(p));
  cell_out->handshake_len = ntohs(get_uint16(p+2));
  if (cell_out->handshake_len > CELL_PAYLOAD_SIZE - 4 ||
      cell_out->handshake_len > p_len - 4)
    return -1;
549
550
  if (cell_out->handshake_type == ONION_HANDSHAKE_TYPE_FAST)
    return -1;
551
552
553
554
  memcpy(cell_out->onionskin, p+4, cell_out->handshake_len);
  return 0;
}

555
556
557
558
559
560
561
562
/** Magic string which, in a CREATE or EXTEND cell, indicates that a seeming
 * TAP payload is really an ntor payload.  We'd do away with this if every
 * relay supported EXTEND2, but we want to be able to extend from A to B with
 * ntor even when A doesn't understand EXTEND2 and so can't generate a
 * CREATE2 cell.
 **/
#define NTOR_CREATE_MAGIC "ntorNTORntorNTOR"

563
564
565
566
567
568
569
570
571
572
573
/** Parse a CREATE, CREATE_FAST, or CREATE2 cell from <b>cell_in</b> into
 * <b>cell_out</b>. Return 0 on success, -1 on failure. (We reject some
 * syntactically valid CREATE2 cells that we can't generate or react to.) */
int
create_cell_parse(create_cell_t *cell_out, const cell_t *cell_in)
{
  memset(cell_out, 0, sizeof(*cell_out));

  switch (cell_in->command) {
  case CELL_CREATE:
    cell_out->cell_type = CELL_CREATE;
574
575
576
577
578
579
580
581
582
583
    if (tor_memeq(cell_in->payload, NTOR_CREATE_MAGIC, 16)) {
      cell_out->handshake_type = ONION_HANDSHAKE_TYPE_NTOR;
      cell_out->handshake_len = NTOR_ONIONSKIN_LEN;
      memcpy(cell_out->onionskin, cell_in->payload+16, NTOR_ONIONSKIN_LEN);
    } else {
      cell_out->handshake_type = ONION_HANDSHAKE_TYPE_TAP;
      cell_out->handshake_len = TAP_ONIONSKIN_CHALLENGE_LEN;
      memcpy(cell_out->onionskin, cell_in->payload,
             TAP_ONIONSKIN_CHALLENGE_LEN);
    }
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
    break;
  case CELL_CREATE_FAST:
    cell_out->cell_type = CELL_CREATE_FAST;
    cell_out->handshake_type = ONION_HANDSHAKE_TYPE_FAST;
    cell_out->handshake_len = CREATE_FAST_LEN;
    memcpy(cell_out->onionskin, cell_in->payload, CREATE_FAST_LEN);
    break;
  case CELL_CREATE2:
    if (parse_create2_payload(cell_out, cell_in->payload,
                              CELL_PAYLOAD_SIZE) < 0)
      return -1;
    break;
  default:
    return -1;
  }

  return check_create_cell(cell_out, 0);
}

/** Helper: return 0 if <b>cell</b> appears valid, -1 otherwise. */
static int
check_created_cell(const created_cell_t *cell)
{
  switch (cell->cell_type) {
  case CELL_CREATED:
    if (cell->handshake_len != TAP_ONIONSKIN_REPLY_LEN)
      return -1;
    break;
  case CELL_CREATED_FAST:
    if (cell->handshake_len != CREATED_FAST_LEN)
      return -1;
    break;
  case CELL_CREATED2:
    if (cell->handshake_len > RELAY_PAYLOAD_SIZE-2)
      return -1;
    break;
  }

  return 0;
}

/** Parse a CREATED, CREATED_FAST, or CREATED2 cell from <b>cell_in</b> into
 * <b>cell_out</b>. Return 0 on success, -1 on failure. */
int
created_cell_parse(created_cell_t *cell_out, const cell_t *cell_in)
{
  memset(cell_out, 0, sizeof(*cell_out));

  switch (cell_in->command) {
  case CELL_CREATED:
    cell_out->cell_type = CELL_CREATED;
    cell_out->handshake_len = TAP_ONIONSKIN_REPLY_LEN;
    memcpy(cell_out->reply, cell_in->payload, TAP_ONIONSKIN_REPLY_LEN);
    break;
  case CELL_CREATED_FAST:
    cell_out->cell_type = CELL_CREATED_FAST;
    cell_out->handshake_len = CREATED_FAST_LEN;
    memcpy(cell_out->reply, cell_in->payload, CREATED_FAST_LEN);
    break;
  case CELL_CREATED2:
    {
      const uint8_t *p = cell_in->payload;
      cell_out->cell_type = CELL_CREATED2;
      cell_out->handshake_len = ntohs(get_uint16(p));
      if (cell_out->handshake_len > CELL_PAYLOAD_SIZE - 2)
        return -1;
      memcpy(cell_out->reply, p+2, cell_out->handshake_len);
      break;
    }
  }

  return check_created_cell(cell_out);
}

/** Helper: return 0 if <b>cell</b> appears valid, -1 otherwise. */
static int
check_extend_cell(const extend_cell_t *cell)
{
  if (tor_digest_is_zero((const char*)cell->node_id))
    return -1;
  /* We don't currently allow EXTEND2 cells without an IPv4 address */
  if (tor_addr_family(&cell->orport_ipv4.addr) == AF_UNSPEC)
    return -1;
  if (cell->create_cell.cell_type == CELL_CREATE) {
    if (cell->cell_type != RELAY_COMMAND_EXTEND)
      return -1;
  } else if (cell->create_cell.cell_type == CELL_CREATE2) {
671
672
    if (cell->cell_type != RELAY_COMMAND_EXTEND2 &&
        cell->cell_type != RELAY_COMMAND_EXTEND)
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
      return -1;
  } else {
    /* In particular, no CREATE_FAST cells are allowed */
    return -1;
  }
  if (cell->create_cell.handshake_type == ONION_HANDSHAKE_TYPE_FAST)
    return -1;

  return check_create_cell(&cell->create_cell, 1);
}

/** Protocol constants for specifier types in EXTEND2
 * @{
 */
#define SPECTYPE_IPV4 0
#define SPECTYPE_IPV6 1
#define SPECTYPE_LEGACY_ID 2
/** @} */

/** Parse an EXTEND or EXTEND2 cell (according to <b>command</b>) from the
 * <b>payload_length</b> bytes of <b>payload</b> into <b>cell_out</b>. Return
 * 0 on success, -1 on failure. */
int
extend_cell_parse(extend_cell_t *cell_out, const uint8_t command,
                  const uint8_t *payload, size_t payload_length)
{
  const uint8_t *eop;

  memset(cell_out, 0, sizeof(*cell_out));
  if (payload_length > RELAY_PAYLOAD_SIZE)
    return -1;
  eop = payload + payload_length;

  switch (command) {
  case RELAY_COMMAND_EXTEND:
    {
      if (payload_length != 6 + TAP_ONIONSKIN_CHALLENGE_LEN + DIGEST_LEN)
        return -1;

      cell_out->cell_type = RELAY_COMMAND_EXTEND;
      tor_addr_from_ipv4n(&cell_out->orport_ipv4.addr, get_uint32(payload));
      cell_out->orport_ipv4.port = ntohs(get_uint16(payload+4));
      tor_addr_make_unspec(&cell_out->orport_ipv6.addr);
716
717
718
719
720
721
722
723
724
725
726
727
728
      if (tor_memeq(payload + 6, NTOR_CREATE_MAGIC, 16)) {
        cell_out->create_cell.cell_type = CELL_CREATE2;
        cell_out->create_cell.handshake_type = ONION_HANDSHAKE_TYPE_NTOR;
        cell_out->create_cell.handshake_len = NTOR_ONIONSKIN_LEN;
        memcpy(cell_out->create_cell.onionskin, payload + 22,
               NTOR_ONIONSKIN_LEN);
      } else {
        cell_out->create_cell.cell_type = CELL_CREATE;
        cell_out->create_cell.handshake_type = ONION_HANDSHAKE_TYPE_TAP;
        cell_out->create_cell.handshake_len = TAP_ONIONSKIN_CHALLENGE_LEN;
        memcpy(cell_out->create_cell.onionskin, payload + 6,
               TAP_ONIONSKIN_CHALLENGE_LEN);
      }
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
      memcpy(cell_out->node_id, payload + 6 + TAP_ONIONSKIN_CHALLENGE_LEN,
             DIGEST_LEN);
      break;
    }
  case RELAY_COMMAND_EXTEND2:
    {
      uint8_t n_specs = *payload, spectype, speclen;
      int i;
      int found_ipv4 = 0, found_ipv6 = 0, found_id = 0;
      tor_addr_make_unspec(&cell_out->orport_ipv4.addr);
      tor_addr_make_unspec(&cell_out->orport_ipv6.addr);

      cell_out->cell_type = RELAY_COMMAND_EXTEND2;
      ++payload;
      /* Parse the specifiers. We'll only take the first IPv4 and first IPv6
       * addres, and the node ID, and ignore everything else */
      for (i = 0; i < n_specs; ++i) {
        if (eop - payload < 2)
          return -1;
        spectype = payload[0];
        speclen = payload[1];
        payload += 2;
        if (eop - payload < speclen)
          return -1;
        switch (spectype) {
        case SPECTYPE_IPV4:
          if (speclen != 6)
            return -1;
          if (!found_ipv4) {
            tor_addr_from_ipv4n(&cell_out->orport_ipv4.addr,
                                get_uint32(payload));
            cell_out->orport_ipv4.port = ntohs(get_uint16(payload+4));
            found_ipv4 = 1;
          }
          break;
        case SPECTYPE_IPV6:
          if (speclen != 18)
            return -1;
          if (!found_ipv6) {
            tor_addr_from_ipv6_bytes(&cell_out->orport_ipv6.addr,
                                     (const char*)payload);
            cell_out->orport_ipv6.port = ntohs(get_uint16(payload+16));
            found_ipv6 = 1;
          }
          break;
        case SPECTYPE_LEGACY_ID:
          if (speclen != 20)
            return -1;
          if (found_id)
            return -1;
          memcpy(cell_out->node_id, payload, 20);
          found_id = 1;
          break;
        }
        payload += speclen;
      }
      if (!found_id || !found_ipv4)
        return -1;
      if (parse_create2_payload(&cell_out->create_cell,payload,eop-payload)<0)
        return -1;
      break;
    }
  default:
    return -1;
  }

  return check_extend_cell(cell_out);
}

/** Helper: return 0 if <b>cell</b> appears valid, -1 otherwise. */
static int
check_extended_cell(const extended_cell_t *cell)
{
  if (cell->created_cell.cell_type == CELL_CREATED) {
    if (cell->cell_type != RELAY_COMMAND_EXTENDED)
      return -1;
  } else if (cell->created_cell.cell_type == CELL_CREATED2) {
    if (cell->cell_type != RELAY_COMMAND_EXTENDED2)
      return -1;
  } else {
    return -1;
  }

  return check_created_cell(&cell->created_cell);
}

/** Parse an EXTENDED or EXTENDED2 cell (according to <b>command</b>) from the
 * <b>payload_length</b> bytes of <b>payload</b> into <b>cell_out</b>. Return
 * 0 on success, -1 on failure. */
int
extended_cell_parse(extended_cell_t *cell_out,
                    const uint8_t command, const uint8_t *payload,
                    size_t payload_len)
{
  memset(cell_out, 0, sizeof(*cell_out));
  if (payload_len > RELAY_PAYLOAD_SIZE)
    return -1;

  switch (command) {
  case RELAY_COMMAND_EXTENDED:
    if (payload_len != TAP_ONIONSKIN_REPLY_LEN)
      return -1;
    cell_out->cell_type = RELAY_COMMAND_EXTENDED;
    cell_out->created_cell.cell_type = CELL_CREATED;
    cell_out->created_cell.handshake_len = TAP_ONIONSKIN_REPLY_LEN;
    memcpy(cell_out->created_cell.reply, payload, TAP_ONIONSKIN_REPLY_LEN);
    break;
  case RELAY_COMMAND_EXTENDED2:
    {
      cell_out->cell_type = RELAY_COMMAND_EXTENDED2;
      cell_out->created_cell.cell_type = CELL_CREATED2;
      cell_out->created_cell.handshake_len = ntohs(get_uint16(payload));
      if (cell_out->created_cell.handshake_len > RELAY_PAYLOAD_SIZE - 2 ||
          cell_out->created_cell.handshake_len > payload_len - 2)
        return -1;
      memcpy(cell_out->created_cell.reply, payload+2,
             cell_out->created_cell.handshake_len);
    }
    break;
  default:
    return -1;
  }

  return check_extended_cell(cell_out);
}

/** Fill <b>cell_out</b> with a correctly formatted version of the
 * CREATE{,_FAST,2} cell in <b>cell_in</b>. Return 0 on success, -1 on
857
858
859
860
 * failure.  This is a cell we didn't originate if <b>relayed</b> is true. */
static int
create_cell_format_impl(cell_t *cell_out, const create_cell_t *cell_in,
                        int relayed)
861
{
862
863
  uint8_t *p;
  size_t space;
864
  if (check_create_cell(cell_in, relayed) < 0)
865
866
867
868
869
    return -1;

  memset(cell_out->payload, 0, sizeof(cell_out->payload));
  cell_out->command = cell_in->cell_type;

870
871
872
  p = cell_out->payload;
  space = sizeof(cell_out->payload);

873
874
  switch (cell_in->cell_type) {
  case CELL_CREATE:
875
876
877
878
879
880
    if (cell_in->handshake_type == ONION_HANDSHAKE_TYPE_NTOR) {
      memcpy(p, NTOR_CREATE_MAGIC, 16);
      p += 16;
      space -= 16;
    }
    /* Fall through */
881
  case CELL_CREATE_FAST:
882
883
    tor_assert(cell_in->handshake_len <= space);
    memcpy(p, cell_in->onionskin, cell_in->handshake_len);
884
885
886
887
888
889
890
891
892
893
894
895
896
897
    break;
  case CELL_CREATE2:
    tor_assert(cell_in->handshake_len <= sizeof(cell_out->payload)-4);
    set_uint16(cell_out->payload, htons(cell_in->handshake_type));
    set_uint16(cell_out->payload+2, htons(cell_in->handshake_len));
    memcpy(cell_out->payload + 4, cell_in->onionskin, cell_in->handshake_len);
    break;
  default:
    return -1;
  }

  return 0;
}

898
899
900
901
902
903
904
905
906
907
908
909
int
create_cell_format(cell_t *cell_out, const create_cell_t *cell_in)
{
  return create_cell_format_impl(cell_out, cell_in, 0);
}

int
create_cell_format_relayed(cell_t *cell_out, const create_cell_t *cell_in)
{
  return create_cell_format_impl(cell_out, cell_in, 1);
}

910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
/** Fill <b>cell_out</b> with a correctly formatted version of the
 * CREATED{,_FAST,2} cell in <b>cell_in</b>. Return 0 on success, -1 on
 * failure. */
int
created_cell_format(cell_t *cell_out, const created_cell_t *cell_in)
{
  if (check_created_cell(cell_in) < 0)
    return -1;

  memset(cell_out->payload, 0, sizeof(cell_out->payload));
  cell_out->command = cell_in->cell_type;

  switch (cell_in->cell_type) {
  case CELL_CREATED:
  case CELL_CREATED_FAST:
    tor_assert(cell_in->handshake_len <= sizeof(cell_out->payload));
    memcpy(cell_out->payload, cell_in->reply, cell_in->handshake_len);
    break;
  case CELL_CREATED2:
    tor_assert(cell_in->handshake_len <= sizeof(cell_out->payload)-2);
    set_uint16(cell_out->payload, htons(cell_in->handshake_len));
    memcpy(cell_out->payload + 2, cell_in->reply, cell_in->handshake_len);
    break;
  default:
    return -1;
  }
  return 0;
}

/** Format the EXTEND{,2} cell in <b>cell_in</b>, storing its relay payload in
 * <b>payload_out</b>, the number of bytes used in *<b>len_out</b>, and the
 * relay command in *<b>command_out</b>. The <b>payload_out</b> must have
 * RELAY_PAYLOAD_SIZE bytes available.  Return 0 on success, -1 on failure. */
int
extend_cell_format(uint8_t *command_out, uint16_t *len_out,
                   uint8_t *payload_out, const extend_cell_t *cell_in)
{
  uint8_t *p, *eop;
  if (check_extend_cell(cell_in) < 0)
    return -1;

  p = payload_out;
  eop = payload_out + RELAY_PAYLOAD_SIZE;

  memset(p, 0, RELAY_PAYLOAD_SIZE);

  switch (cell_in->cell_type) {
  case RELAY_COMMAND_EXTEND:
    {
      *command_out = RELAY_COMMAND_EXTEND;
      *len_out = 6 + TAP_ONIONSKIN_CHALLENGE_LEN + DIGEST_LEN;
      set_uint32(p, tor_addr_to_ipv4n(&cell_in->orport_ipv4.addr));
      set_uint16(p+4, ntohs(cell_in->orport_ipv4.port));
963
964
965
966
967
968
969
      if (cell_in->create_cell.handshake_type == ONION_HANDSHAKE_TYPE_NTOR) {
        memcpy(p+6, NTOR_CREATE_MAGIC, 16);
        memcpy(p+22, cell_in->create_cell.onionskin, NTOR_ONIONSKIN_LEN);
      } else {
        memcpy(p+6, cell_in->create_cell.onionskin,
               TAP_ONIONSKIN_CHALLENGE_LEN);
      }
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
      memcpy(p+6+TAP_ONIONSKIN_CHALLENGE_LEN, cell_in->node_id, DIGEST_LEN);
    }
    break;
  case RELAY_COMMAND_EXTEND2:
    {
      uint8_t n = 2;
      *command_out = RELAY_COMMAND_EXTEND2;

      *p++ = n; /* 2 identifiers */
      *p++ = SPECTYPE_IPV4; /* First is IPV4. */
      *p++ = 6; /* It's 6 bytes long. */
      set_uint32(p, tor_addr_to_ipv4n(&cell_in->orport_ipv4.addr));
      set_uint16(p+4, htons(cell_in->orport_ipv4.port));
      p += 6;
      *p++ = SPECTYPE_LEGACY_ID; /* Next is an identity digest. */
      *p++ = 20; /* It's 20 bytes long */
      memcpy(p, cell_in->node_id, DIGEST_LEN);
      p += 20;

      /* Now we can send the handshake */
      set_uint16(p, htons(cell_in->create_cell.handshake_type));
      set_uint16(p+2, htons(cell_in->create_cell.handshake_len));
      p += 4;

      if (cell_in->create_cell.handshake_len > eop - p)
        return -1;

      memcpy(p, cell_in->create_cell.onionskin,
             cell_in->create_cell.handshake_len);

      p += cell_in->create_cell.handshake_len;
For faster browsing, not all history is shown. View entire blame