src/or/rendmid.c

   1 /* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   2  * Copyright (c) 2007-2015, The Tor Project, Inc. */
   3 /* See LICENSE for licensing information */
   4
   5 /**
   6  * \file rendmid.c
   7  * \brief Implement introductions points and rendezvous points.
   8  **/
   9
  10 #include "or.h"
  11 #include "circuitlist.h"
  12 #include "circuituse.h"
  13 #include "config.h"
  14 #include "relay.h"
  15 #include "rendmid.h"
  16 #include "rephist.h"
  17
  18 /** Respond to an ESTABLISH_INTRO cell by checking the signed data and
  19  * setting the circuit's purpose and service pk digest.
  20  */
  21 int
  22 rend_mid_establish_intro(or_circuit_t *circ, const uint8_t *request,
  23                          size_t request_len)
  24 {
  25   crypto_pk_t *pk = NULL;
  26   char buf[DIGEST_LEN+9];
  27   char expected_digest[DIGEST_LEN];
  28   char pk_digest[DIGEST_LEN];
  29   size_t asn1len;
  30   or_circuit_t *c;
  31   char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
  32   int reason = END_CIRC_REASON_INTERNAL;
  33
  34   log_info(LD_REND,
  35            "Received an ESTABLISH_INTRO request on circuit %u",
  36            (unsigned) circ->p_circ_id);
  37
  38   if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {
  39     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
  40          "Rejecting ESTABLISH_INTRO on non-OR or non-edge circuit.");
  41     reason = END_CIRC_REASON_TORPROTOCOL;
  42     goto err;
  43   }
  44   if (request_len < 2+DIGEST_LEN)
  45     goto truncated;
  46   /* First 2 bytes: length of asn1-encoded key. */
  47   asn1len = ntohs(get_uint16(request));
  48
  49   /* Next asn1len bytes: asn1-encoded key. */
  50   if (request_len < 2+DIGEST_LEN+asn1len)
  51     goto truncated;
  52   pk = crypto_pk_asn1_decode((char*)(request+2), asn1len);
  53   if (!pk) {
  54     reason = END_CIRC_REASON_TORPROTOCOL;
  55     log_warn(LD_PROTOCOL, "Couldn't decode public key.");
  56     goto err;
  57   }
  58
  59   /* Next 20 bytes: Hash of rend_circ_nonce | "INTRODUCE" */
  60   memcpy(buf, circ->rend_circ_nonce, DIGEST_LEN);
  61   memcpy(buf+DIGEST_LEN, "INTRODUCE", 9);
  62   if (crypto_digest(expected_digest, buf, DIGEST_LEN+9) < 0) {
  63     log_warn(LD_BUG, "Internal error computing digest.");
  64     goto err;
  65   }
  66   if (tor_memneq(expected_digest, request+2+asn1len, DIGEST_LEN)) {
  67     log_warn(LD_PROTOCOL, "Hash of session info was not as expected.");
  68     reason = END_CIRC_REASON_TORPROTOCOL;
  69     goto err;
  70   }
  71   /* Rest of body: signature of previous data */
  72   note_crypto_pk_op(REND_MID);
  73   if (crypto_pk_public_checksig_digest(pk,
  74                                        (char*)request, 2+asn1len+DIGEST_LEN,
  75                                        (char*)(request+2+DIGEST_LEN+asn1len),
  76                                        request_len-(2+DIGEST_LEN+asn1len))<0) {
  77     log_warn(LD_PROTOCOL,
  78              "Incorrect signature on ESTABLISH_INTRO cell; rejecting.");
  79     reason = END_CIRC_REASON_TORPROTOCOL;
  80     goto err;
  81   }
  82
  83   /* The request is valid.  First, compute the hash of Bob's PK.*/
  84   if (crypto_pk_get_digest(pk, pk_digest)<0) {
  85     log_warn(LD_BUG, "Internal error: couldn't hash public key.");
  86     goto err;
  87   }
  88
  89   crypto_pk_free(pk); /* don't need it anymore */
  90   pk = NULL; /* so we don't free it again if err */
  91
  92   base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
  93                 pk_digest, REND_SERVICE_ID_LEN);
  94
  95   /* Close any other intro circuits with the same pk. */
  96   c = NULL;
  97   while ((c = circuit_get_intro_point((const uint8_t *)pk_digest))) {
  98     log_info(LD_REND, "Replacing old circuit for service %s",
  99              safe_str(serviceid));
 100     circuit_mark_for_close(TO_CIRCUIT(c), END_CIRC_REASON_FINISHED);
 101     /* Now it's marked, and it won't be returned next time. */
 102   }
 103
 104   /* Acknowledge the request. */
 105   if (relay_send_command_from_edge(0, TO_CIRCUIT(circ),
 106                                    RELAY_COMMAND_INTRO_ESTABLISHED,
 107                                    "", 0, NULL)<0) {
 108     log_info(LD_GENERAL, "Couldn't send INTRO_ESTABLISHED cell.");
 109     goto err;
 110   }
 111
 112   /* Now, set up this circuit. */
 113   circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_INTRO_POINT);
 114   circuit_set_intro_point_digest(circ, (uint8_t *)pk_digest);
 115
 116   log_info(LD_REND,
 117            "Established introduction point on circuit %u for service %s",
 118            (unsigned) circ->p_circ_id, safe_str(serviceid));
 119
 120   return 0;
 121  truncated:
 122   log_warn(LD_PROTOCOL, "Rejecting truncated ESTABLISH_INTRO cell.");
 123   reason = END_CIRC_REASON_TORPROTOCOL;
 124  err:
 125   if (pk) crypto_pk_free(pk);
 126   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 127   return -1;
 128 }
 129
 130 /** Process an INTRODUCE1 cell by finding the corresponding introduction
 131  * circuit, and relaying the body of the INTRODUCE1 cell inside an
 132  * INTRODUCE2 cell.
 133  */
 134 int
 135 rend_mid_introduce(or_circuit_t *circ, const uint8_t *request,
 136                    size_t request_len)
 137 {
 138   or_circuit_t *intro_circ;
 139   char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
 140   char nak_body[1];
 141
 142   log_info(LD_REND, "Received an INTRODUCE1 request on circuit %u",
 143            (unsigned)circ->p_circ_id);
 144
 145   if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {
 146     log_warn(LD_PROTOCOL,
 147              "Rejecting INTRODUCE1 on non-OR or non-edge circuit %u.",
 148              (unsigned)circ->p_circ_id);
 149     goto err;
 150   }
 151
 152   /* We have already done an introduction on this circuit but we just
 153      received a request for another one. We block it since this might
 154      be an attempt to DoS a hidden service (#15515). */
 155   if (circ->already_received_introduce1) {
 156     log_fn(LOG_PROTOCOL_WARN, LD_REND,
 157            "Blocking multiple introductions on the same circuit. "
 158            "Someone might be trying to attack a hidden service through "
 159            "this relay.");
 160     circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_TORPROTOCOL);
 161     return -1;
 162   }
 163
 164   circ->already_received_introduce1 = 1;
 165
 166   /* We could change this to MAX_HEX_NICKNAME_LEN now that 0.0.9.x is
 167    * obsolete; however, there isn't much reason to do so, and we're going
 168    * to revise this protocol anyway.
 169    */
 170   if (request_len < (DIGEST_LEN+(MAX_NICKNAME_LEN+1)+REND_COOKIE_LEN+
 171                      DH_KEY_LEN+CIPHER_KEY_LEN+PKCS1_OAEP_PADDING_OVERHEAD)) {
 172     log_warn(LD_PROTOCOL, "Impossibly short INTRODUCE1 cell on circuit %u; "
 173              "responding with nack.",
 174              (unsigned)circ->p_circ_id);
 175     goto err;
 176   }
 177
 178   base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
 179                 (char*)request, REND_SERVICE_ID_LEN);
 180
 181   /* The first 20 bytes are all we look at: they have a hash of Bob's PK. */
 182   intro_circ = circuit_get_intro_point((const uint8_t*)request);
 183   if (!intro_circ) {
 184     log_info(LD_REND,
 185              "No intro circ found for INTRODUCE1 cell (%s) from circuit %u; "
 186              "responding with nack.",
 187              safe_str(serviceid), (unsigned)circ->p_circ_id);
 188     goto err;
 189   }
 190
 191   log_info(LD_REND,
 192            "Sending introduction request for service %s "
 193            "from circ %u to circ %u",
 194            safe_str(serviceid), (unsigned)circ->p_circ_id,
 195            (unsigned)intro_circ->p_circ_id);
 196
 197   /* Great.  Now we just relay the cell down the circuit. */
 198   if (relay_send_command_from_edge(0, TO_CIRCUIT(intro_circ),
 199                                    RELAY_COMMAND_INTRODUCE2,
 200                                    (char*)request, request_len, NULL)) {
 201     log_warn(LD_GENERAL,
 202              "Unable to send INTRODUCE2 cell to Tor client.");
 203     goto err;
 204   }
 205   /* And send an ack down Alice's circuit.  Empty body means succeeded. */
 206   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 207                                    RELAY_COMMAND_INTRODUCE_ACK,
 208                                    NULL,0,NULL)) {
 209     log_warn(LD_GENERAL, "Unable to send INTRODUCE_ACK cell to Tor client.");
 210     circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
 211     return -1;
 212   }
 213
 214   return 0;
 215  err:
 216   /* Send the client a NACK */
 217   nak_body[0] = 1;
 218   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 219                                    RELAY_COMMAND_INTRODUCE_ACK,
 220                                    nak_body, 1, NULL)) {
 221     log_warn(LD_GENERAL, "Unable to send NAK to Tor client.");
 222     /* Is this right? */
 223     circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
 224   }
 225   return -1;
 226 }
 227
 228 /** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and
 229  * rendezvous cookie.
 230  */
 231 int
 232 rend_mid_establish_rendezvous(or_circuit_t *circ, const uint8_t *request,
 233                               size_t request_len)
 234 {
 235   char hexid[9];
 236   int reason = END_CIRC_REASON_TORPROTOCOL;
 237
 238   log_info(LD_REND, "Received an ESTABLISH_RENDEZVOUS request on circuit %u",
 239            (unsigned)circ->p_circ_id);
 240
 241   if (circ->base_.purpose != CIRCUIT_PURPOSE_OR) {
 242     log_warn(LD_PROTOCOL,
 243              "Tried to establish rendezvous on non-OR circuit with purpose %s",
 244              circuit_purpose_to_string(circ->base_.purpose));
 245     goto err;
 246   }
 247
 248   if (circ->base_.n_chan) {
 249     log_warn(LD_PROTOCOL,
 250              "Tried to establish rendezvous on non-edge circuit");
 251     goto err;
 252   }
 253
 254   if (request_len != REND_COOKIE_LEN) {
 255     log_fn(LOG_PROTOCOL_WARN,
 256            LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS.");
 257     goto err;
 258   }
 259
 260   if (circuit_get_rendezvous(request)) {
 261     log_warn(LD_PROTOCOL,
 262              "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS.");
 263     goto err;
 264   }
 265
 266   /* Acknowledge the request. */
 267   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 268                                    RELAY_COMMAND_RENDEZVOUS_ESTABLISHED,
 269                                    "", 0, NULL)<0) {
 270     log_warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell.");
 271     reason = END_CIRC_REASON_INTERNAL;
 272     goto err;
 273   }
 274
 275   circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_POINT_WAITING);
 276   circuit_set_rendezvous_cookie(circ, request);
 277
 278   base16_encode(hexid,9,(char*)request,4);
 279
 280   log_info(LD_REND,
 281            "Established rendezvous point on circuit %u for cookie %s",
 282            (unsigned)circ->p_circ_id, hexid);
 283
 284   return 0;
 285  err:
 286   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 287   return -1;
 288 }
 289
 290 /** Process a RENDEZVOUS1 cell by looking up the correct rendezvous
 291  * circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and
 292  * connecting the two circuits.
 293  */
 294 int
 295 rend_mid_rendezvous(or_circuit_t *circ, const uint8_t *request,
 296                     size_t request_len)
 297 {
 298   const or_options_t *options = get_options();
 299   or_circuit_t *rend_circ;
 300   char hexid[9];
 301   int reason = END_CIRC_REASON_INTERNAL;
 302
 303   if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {
 304     log_info(LD_REND,
 305              "Tried to complete rendezvous on non-OR or non-edge circuit %u.",
 306              (unsigned)circ->p_circ_id);
 307     reason = END_CIRC_REASON_TORPROTOCOL;
 308     goto err;
 309   }
 310
 311   if (request_len != REND_COOKIE_LEN+DH_KEY_LEN+DIGEST_LEN) {
 312     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 313          "Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %u.",
 314          (int)request_len, (unsigned)circ->p_circ_id);
 315     reason = END_CIRC_REASON_TORPROTOCOL;
 316     goto err;
 317   }
 318
 319   base16_encode(hexid, sizeof(hexid), (const char*)request, 4);
 320
 321   log_info(LD_REND,
 322            "Got request for rendezvous from circuit %u to cookie %s.",
 323            (unsigned)circ->p_circ_id, hexid);
 324
 325   rend_circ = circuit_get_rendezvous(request);
 326   if (!rend_circ) {
 327     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 328          "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.",
 329          hexid);
 330     reason = END_CIRC_REASON_TORPROTOCOL;
 331     goto err;
 332   }
 333
 334   /* Statistics: Mark this circuit as an RP circuit so that we collect
 335      stats from it. */
 336   if (options->HiddenServiceStatistics) {
 337     circ->circuit_carries_hs_traffic_stats = 1;
 338   }
 339
 340   /* Send the RENDEZVOUS2 cell to Alice. */
 341   if (relay_send_command_from_edge(0, TO_CIRCUIT(rend_circ),
 342                                    RELAY_COMMAND_RENDEZVOUS2,
 343                                    (char*)(request+REND_COOKIE_LEN),
 344                                    request_len-REND_COOKIE_LEN, NULL)) {
 345     log_warn(LD_GENERAL,
 346              "Unable to send RENDEZVOUS2 cell to client on circuit %u.",
 347              (unsigned)rend_circ->p_circ_id);
 348     goto err;
 349   }
 350
 351   /* Join the circuits. */
 352   log_info(LD_REND,
 353            "Completing rendezvous: circuit %u joins circuit %u (cookie %s)",
 354            (unsigned)circ->p_circ_id, (unsigned)rend_circ->p_circ_id, hexid);
 355
 356   circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_ESTABLISHED);
 357   circuit_change_purpose(TO_CIRCUIT(rend_circ),
 358                          CIRCUIT_PURPOSE_REND_ESTABLISHED);
 359   circuit_set_rendezvous_cookie(circ, NULL);
 360
 361   rend_circ->rend_splice = circ;
 362   circ->rend_splice = rend_circ;
 363
 364   return 0;
 365  err:
 366   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 367   return -1;
 368 }
 369