aboutsummaryrefslogtreecommitdiff
path: root/src/or/rendmid.c
blob: 57f5b6daedd15f554b9a0e666e79dabef0258bd5 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
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
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
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
/* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
 * Copyright (c) 2007-2009, The Tor Project, Inc. */
/* See LICENSE for licensing information */

/**
 * \file rendmid.c
 * \brief Implement introductions points and rendezvous points.
 **/

#include "or.h"

/** Respond to an ESTABLISH_INTRO cell by checking the signed data and
 * setting the circuit's purpose and service pk digest.
 */
int
rend_mid_establish_intro(or_circuit_t *circ, const char *request,
                         size_t request_len)
{
  crypto_pk_env_t *pk = NULL;
  char buf[DIGEST_LEN+9];
  char expected_digest[DIGEST_LEN];
  char pk_digest[DIGEST_LEN];
  size_t asn1len;
  or_circuit_t *c;
  char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
  int reason = END_CIRC_REASON_INTERNAL;

  log_info(LD_REND,
           "Received an ESTABLISH_INTRO request on circuit %d",
           circ->p_circ_id);

  if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
    log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
         "Rejecting ESTABLISH_INTRO on non-OR or non-edge circuit.");
    reason = END_CIRC_REASON_TORPROTOCOL;
    goto err;
  }
  if (request_len < 2+DIGEST_LEN)
    goto truncated;
  /* First 2 bytes: length of asn1-encoded key. */
  asn1len = ntohs(get_uint16(request));

  /* Next asn1len bytes: asn1-encoded key. */
  if (request_len < 2+DIGEST_LEN+asn1len)
    goto truncated;
  pk = crypto_pk_asn1_decode(request+2, asn1len);
  if (!pk) {
    reason = END_CIRC_REASON_TORPROTOCOL;
    log_warn(LD_PROTOCOL, "Couldn't decode public key.");
    goto err;
  }

  /* Next 20 bytes: Hash of handshake_digest | "INTRODUCE" */
  memcpy(buf, circ->handshake_digest, DIGEST_LEN);
  memcpy(buf+DIGEST_LEN, "INTRODUCE", 9);
  if (crypto_digest(expected_digest, buf, DIGEST_LEN+9) < 0) {
    log_warn(LD_BUG, "Internal error computing digest.");
    goto err;
  }
  if (memcmp(expected_digest, request+2+asn1len, DIGEST_LEN)) {
    log_warn(LD_PROTOCOL, "Hash of session info was not as expected.");
    reason = END_CIRC_REASON_TORPROTOCOL;
    goto err;
  }
  /* Rest of body: signature of previous data */
  note_crypto_pk_op(REND_MID);
  if (crypto_pk_public_checksig_digest(pk, request, 2+asn1len+DIGEST_LEN,
                                       request+2+DIGEST_LEN+asn1len,
                                       request_len-(2+DIGEST_LEN+asn1len))<0) {
    log_warn(LD_PROTOCOL,
             "Incorrect signature on ESTABLISH_INTRO cell; rejecting.");
    reason = END_CIRC_REASON_TORPROTOCOL;
    goto err;
  }

  /* The request is valid.  First, compute the hash of Bob's PK.*/
  if (crypto_pk_get_digest(pk, pk_digest)<0) {
    log_warn(LD_BUG, "Internal error: couldn't hash public key.");
    goto err;
  }

  crypto_free_pk_env(pk); /* don't need it anymore */
  pk = NULL; /* so we don't free it again if err */

  base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
                pk_digest, REND_SERVICE_ID_LEN);

  /* Close any other intro circuits with the same pk. */
  c = NULL;
  while ((c = circuit_get_intro_point(pk_digest))) {
    log_info(LD_REND, "Replacing old circuit for service %s",
             safe_str(serviceid));
    circuit_mark_for_close(TO_CIRCUIT(c), END_CIRC_REASON_FINISHED);
    /* Now it's marked, and it won't be returned next time. */
  }

  /* Acknowledge the request. */
  if (relay_send_command_from_edge(0, TO_CIRCUIT(circ),
                                   RELAY_COMMAND_INTRO_ESTABLISHED,
                                   "", 0, NULL)<0) {
    log_info(LD_GENERAL, "Couldn't send INTRO_ESTABLISHED cell.");
    goto err;
  }

  /* Now, set up this circuit. */
  circ->_base.purpose = CIRCUIT_PURPOSE_INTRO_POINT;
  memcpy(circ->rend_token, pk_digest, DIGEST_LEN);

  log_info(LD_REND,
           "Established introduction point on circuit %d for service %s",
           circ->p_circ_id, safe_str(serviceid));

  return 0;
 truncated:
  log_warn(LD_PROTOCOL, "Rejecting truncated ESTABLISH_INTRO cell.");
  reason = END_CIRC_REASON_TORPROTOCOL;
 err:
  if (pk) crypto_free_pk_env(pk);
  circuit_mark_for_close(TO_CIRCUIT(circ), reason);
  return -1;
}

/** Process an INTRODUCE1 cell by finding the corresponding introduction
 * circuit, and relaying the body of the INTRODUCE1 cell inside an
 * INTRODUCE2 cell.
 */
int
rend_mid_introduce(or_circuit_t *circ, const char *request, size_t request_len)
{
  or_circuit_t *intro_circ;
  char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
  char nak_body[1];

  log_info(LD_REND, "Received an INTRODUCE1 request on circuit %d",
           circ->p_circ_id);

  if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
    log_warn(LD_PROTOCOL,
             "Rejecting INTRODUCE1 on non-OR or non-edge circuit %d.",
             circ->p_circ_id);
    goto err;
  }

  /* We could change this to MAX_HEX_NICKNAME_LEN now that 0.0.9.x is
   * obsolete; however, there isn't much reason to do so, and we're going
   * to revise this protocol anyway.
   */
  if (request_len < (DIGEST_LEN+(MAX_NICKNAME_LEN+1)+REND_COOKIE_LEN+
                     DH_KEY_LEN+CIPHER_KEY_LEN+PKCS1_OAEP_PADDING_OVERHEAD)) {
    log_warn(LD_PROTOCOL, "Impossibly short INTRODUCE1 cell on circuit %d; "
             "responding with nack.",
             circ->p_circ_id);
    goto err;
  }

  base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
                request, REND_SERVICE_ID_LEN);

  /* The first 20 bytes are all we look at: they have a hash of Bob's PK. */
  intro_circ = circuit_get_intro_point(request);
  if (!intro_circ) {
    log_info(LD_REND,
             "No intro circ found for INTRODUCE1 cell (%s) from circuit %d; "
             "responding with nack.",
             safe_str(serviceid), circ->p_circ_id);
    goto err;
  }

  log_info(LD_REND,
           "Sending introduction request for service %s "
           "from circ %d to circ %d",
           safe_str(serviceid), circ->p_circ_id,
           intro_circ->p_circ_id);

  /* Great.  Now we just relay the cell down the circuit. */
  if (relay_send_command_from_edge(0, TO_CIRCUIT(intro_circ),
                                   RELAY_COMMAND_INTRODUCE2,
                                   request, request_len, NULL)) {
    log_warn(LD_GENERAL,
             "Unable to send INTRODUCE2 cell to Tor client.");
    goto err;
  }
  /* And sent an ack down Alice's circuit.  Empty body means succeeded. */
  if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
                                   RELAY_COMMAND_INTRODUCE_ACK,
                                   NULL,0,NULL)) {
    log_warn(LD_GENERAL, "Unable to send INTRODUCE_ACK cell to Tor client.");
    circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
    return -1;
  }

  return 0;
 err:
  /* Send the client an NACK */
  nak_body[0] = 1;
  if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
                                   RELAY_COMMAND_INTRODUCE_ACK,
                                   nak_body, 1, NULL)) {
    log_warn(LD_GENERAL, "Unable to send NAK to Tor client.");
    /* Is this right? */
    circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
  }
  return -1;
}

/** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and
 * rendezvous cookie.
 */
int
rend_mid_establish_rendezvous(or_circuit_t *circ, const char *request,
                              size_t request_len)
{
  char hexid[9];
  int reason = END_CIRC_REASON_TORPROTOCOL;

  log_info(LD_REND, "Received an ESTABLISH_RENDEZVOUS request on circuit %d",
           circ->p_circ_id);

  if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
    log_warn(LD_PROTOCOL,
             "Tried to establish rendezvous on non-OR or non-edge circuit.");
    goto err;
  }

  if (request_len != REND_COOKIE_LEN) {
    log_warn(LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS.");
    goto err;
  }

  if (circuit_get_rendezvous(request)) {
    log_warn(LD_PROTOCOL,
             "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS.");
    goto err;
  }

  /* Acknowledge the request. */
  if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
                                   RELAY_COMMAND_RENDEZVOUS_ESTABLISHED,
                                   "", 0, NULL)<0) {
    log_warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell.");
    reason = END_CIRC_REASON_INTERNAL;
    goto err;
  }

  circ->_base.purpose = CIRCUIT_PURPOSE_REND_POINT_WAITING;
  memcpy(circ->rend_token, request, REND_COOKIE_LEN);

  base16_encode(hexid,9,request,4);

  log_info(LD_REND,
           "Established rendezvous point on circuit %d for cookie %s",
           circ->p_circ_id, hexid);

  return 0;
 err:
  circuit_mark_for_close(TO_CIRCUIT(circ), reason);
  return -1;
}

/** Process a RENDEZVOUS1 cell by looking up the correct rendezvous
 * circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and
 * connecting the two circuits.
 */
int
rend_mid_rendezvous(or_circuit_t *circ, const char *request,
                    size_t request_len)
{
  or_circuit_t *rend_circ;
  char hexid[9];
  int reason = END_CIRC_REASON_INTERNAL;
  base16_encode(hexid,9,request,request_len<4?request_len:4);

  if (request_len>=4) {
    log_info(LD_REND,
             "Got request for rendezvous from circuit %d to cookie %s.",
             circ->p_circ_id, hexid);
  }

  if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
    log_info(LD_REND,
             "Tried to complete rendezvous on non-OR or non-edge circuit %d.",
             circ->p_circ_id);
    reason = END_CIRC_REASON_TORPROTOCOL;
    goto err;
  }

  if (request_len != REND_COOKIE_LEN+DH_KEY_LEN+DIGEST_LEN) {
    log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
         "Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %d.",
         (int)request_len, circ->p_circ_id);
    reason = END_CIRC_REASON_TORPROTOCOL;
    goto err;
  }

  rend_circ = circuit_get_rendezvous(request);
  if (!rend_circ) {
    log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
         "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.",
         hexid);
    reason = END_CIRC_REASON_TORPROTOCOL;
    goto err;
  }

  /* Send the RENDEZVOUS2 cell to Alice. */
  if (relay_send_command_from_edge(0, TO_CIRCUIT(rend_circ),
                                   RELAY_COMMAND_RENDEZVOUS2,
                                   request+REND_COOKIE_LEN,
                                   request_len-REND_COOKIE_LEN, NULL)) {
    log_warn(LD_GENERAL,
             "Unable to send RENDEZVOUS2 cell to client on circuit %d.",
             rend_circ->p_circ_id);
    goto err;
  }

  /* Join the circuits. */
  log_info(LD_REND,
           "Completing rendezvous: circuit %d joins circuit %d (cookie %s)",
           circ->p_circ_id, rend_circ->p_circ_id, hexid);

  circ->_base.purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
  rend_circ->_base.purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
  memset(circ->rend_token, 0, REND_COOKIE_LEN);

  rend_circ->rend_splice = circ;
  circ->rend_splice = rend_circ;

  return 0;
 err:
  circuit_mark_for_close(TO_CIRCUIT(circ), reason);
  return -1;
}