src/or/rendmid.c

   1 /* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   2  * Copyright (c) 2007-2017, 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 "channel.h"
  12 #include "circuitlist.h"
  13 #include "circuituse.h"
  14 #include "config.h"
  15 #include "crypto.h"
  16 #include "dos.h"
  17 #include "relay.h"
  18 #include "rendmid.h"
  19 #include "rephist.h"
  20 #include "hs_circuitmap.h"
  21 #include "hs_intropoint.h"
  22
  23 /** Respond to an ESTABLISH_INTRO cell by checking the signed data and
  24  * setting the circuit's purpose and service pk digest.
  25  */
  26 int
  27 rend_mid_establish_intro_legacy(or_circuit_t *circ, const uint8_t *request,
  28                                 size_t request_len)
  29 {
  30   crypto_pk_t *pk = NULL;
  31   char buf[DIGEST_LEN+9];
  32   char expected_digest[DIGEST_LEN];
  33   char pk_digest[DIGEST_LEN];
  34   size_t asn1len;
  35   or_circuit_t *c;
  36   char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
  37   int reason = END_CIRC_REASON_INTERNAL;
  38
  39   log_info(LD_REND,
  40            "Received a legacy ESTABLISH_INTRO request on circuit %u",
  41            (unsigned) circ->p_circ_id);
  42
  43   if (!hs_intro_circuit_is_suitable_for_establish_intro(circ)) {
  44     reason = END_CIRC_REASON_TORPROTOCOL;
  45     goto err;
  46   }
  47
  48   if (request_len < 2+DIGEST_LEN)
  49     goto truncated;
  50   /* First 2 bytes: length of asn1-encoded key. */
  51   asn1len = ntohs(get_uint16(request));
  52
  53   /* Next asn1len bytes: asn1-encoded key. */
  54   if (request_len < 2+DIGEST_LEN+asn1len)
  55     goto truncated;
  56   pk = crypto_pk_asn1_decode((char*)(request+2), asn1len);
  57   if (!pk) {
  58     reason = END_CIRC_REASON_TORPROTOCOL;
  59     log_warn(LD_PROTOCOL, "Couldn't decode public key.");
  60     goto err;
  61   }
  62
  63   /* Next 20 bytes: Hash of rend_circ_nonce | "INTRODUCE" */
  64   memcpy(buf, circ->rend_circ_nonce, DIGEST_LEN);
  65   memcpy(buf+DIGEST_LEN, "INTRODUCE", 9);
  66   if (crypto_digest(expected_digest, buf, DIGEST_LEN+9) < 0) {
  67     log_warn(LD_BUG, "Internal error computing digest.");
  68     goto err;
  69   }
  70   if (tor_memneq(expected_digest, request+2+asn1len, DIGEST_LEN)) {
  71     log_warn(LD_PROTOCOL, "Hash of session info was not as expected.");
  72     reason = END_CIRC_REASON_TORPROTOCOL;
  73     goto err;
  74   }
  75   /* Rest of body: signature of previous data */
  76   if (crypto_pk_public_checksig_digest(pk,
  77                                        (char*)request, 2+asn1len+DIGEST_LEN,
  78                                        (char*)(request+2+DIGEST_LEN+asn1len),
  79                                        request_len-(2+DIGEST_LEN+asn1len))<0) {
  80     log_warn(LD_PROTOCOL,
  81              "Incorrect signature on ESTABLISH_INTRO cell; rejecting.");
  82     reason = END_CIRC_REASON_TORPROTOCOL;
  83     goto err;
  84   }
  85
  86   /* The request is valid.  First, compute the hash of the service's PK.*/
  87   if (crypto_pk_get_digest(pk, pk_digest)<0) {
  88     log_warn(LD_BUG, "Internal error: couldn't hash public key.");
  89     goto err;
  90   }
  91
  92   crypto_pk_free(pk); /* don't need it anymore */
  93   pk = NULL; /* so we don't free it again if err */
  94
  95   base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
  96                 pk_digest, REND_SERVICE_ID_LEN);
  97
  98   /* Close any other intro circuits with the same pk. */
  99   c = NULL;
 100   while ((c = hs_circuitmap_get_intro_circ_v2_relay_side(
 101                                                 (const uint8_t *)pk_digest))) {
 102     log_info(LD_REND, "Replacing old circuit for service %s",
 103              safe_str(serviceid));
 104     circuit_mark_for_close(TO_CIRCUIT(c), END_CIRC_REASON_FINISHED);
 105     /* Now it's marked, and it won't be returned next time. */
 106   }
 107
 108   /* Acknowledge the request. */
 109   if (hs_intro_send_intro_established_cell(circ) < 0) {
 110     log_info(LD_GENERAL, "Couldn't send INTRO_ESTABLISHED cell.");
 111     goto err_no_close;
 112   }
 113
 114   /* Now, set up this circuit. */
 115   circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_INTRO_POINT);
 116   hs_circuitmap_register_intro_circ_v2_relay_side(circ, (uint8_t *)pk_digest);
 117
 118   log_info(LD_REND,
 119            "Established introduction point on circuit %u for service %s",
 120            (unsigned) circ->p_circ_id, safe_str(serviceid));
 121
 122   return 0;
 123  truncated:
 124   log_warn(LD_PROTOCOL, "Rejecting truncated ESTABLISH_INTRO cell.");
 125   reason = END_CIRC_REASON_TORPROTOCOL;
 126  err:
 127   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 128  err_no_close:
 129   if (pk) crypto_pk_free(pk);
 130   return -1;
 131 }
 132
 133 /** Process an INTRODUCE1 cell by finding the corresponding introduction
 134  * circuit, and relaying the body of the INTRODUCE1 cell inside an
 135  * INTRODUCE2 cell.
 136  */
 137 int
 138 rend_mid_introduce_legacy(or_circuit_t *circ, const uint8_t *request,
 139                           size_t request_len)
 140 {
 141   or_circuit_t *intro_circ;
 142   char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
 143   char nak_body[1];
 144
 145   log_info(LD_REND, "Received an INTRODUCE1 request on circuit %u",
 146            (unsigned)circ->p_circ_id);
 147
 148   /* At this point, we know that the circuit is valid for an INTRODUCE1
 149    * because the validation has been made before calling this function. */
 150   tor_assert(circ->base_.purpose == CIRCUIT_PURPOSE_OR);
 151   tor_assert(!circ->base_.n_chan);
 152
 153   /* We could change this to MAX_HEX_NICKNAME_LEN now that 0.0.9.x is
 154    * obsolete; however, there isn't much reason to do so, and we're going
 155    * to revise this protocol anyway.
 156    */
 157   if (request_len < (DIGEST_LEN+(MAX_NICKNAME_LEN+1)+REND_COOKIE_LEN+
 158                      DH_KEY_LEN+CIPHER_KEY_LEN+PKCS1_OAEP_PADDING_OVERHEAD)) {
 159     log_warn(LD_PROTOCOL, "Impossibly short INTRODUCE1 cell on circuit %u; "
 160              "responding with nack.",
 161              (unsigned)circ->p_circ_id);
 162     goto err;
 163   }
 164
 165   base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
 166                 (char*)request, REND_SERVICE_ID_LEN);
 167
 168   /* The first 20 bytes are all we look at: they have a hash of the service's
 169    * PK. */
 170   intro_circ = hs_circuitmap_get_intro_circ_v2_relay_side(
 171                                                       (const uint8_t*)request);
 172   if (!intro_circ) {
 173     log_info(LD_REND,
 174              "No intro circ found for INTRODUCE1 cell (%s) from circuit %u; "
 175              "responding with nack.",
 176              safe_str(serviceid), (unsigned)circ->p_circ_id);
 177     goto err;
 178   }
 179
 180   log_info(LD_REND,
 181            "Sending introduction request for service %s "
 182            "from circ %u to circ %u",
 183            safe_str(serviceid), (unsigned)circ->p_circ_id,
 184            (unsigned)intro_circ->p_circ_id);
 185
 186   /* Great.  Now we just relay the cell down the circuit. */
 187   if (relay_send_command_from_edge(0, TO_CIRCUIT(intro_circ),
 188                                    RELAY_COMMAND_INTRODUCE2,
 189                                    (char*)request, request_len, NULL)) {
 190     log_warn(LD_GENERAL,
 191              "Unable to send INTRODUCE2 cell to Tor client.");
 192     /* Stop right now, the circuit has been closed. */
 193     return -1;
 194   }
 195   /* And send an ack down the client's circuit.  Empty body means succeeded. */
 196   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 197                                    RELAY_COMMAND_INTRODUCE_ACK,
 198                                    NULL,0,NULL)) {
 199     log_warn(LD_GENERAL, "Unable to send INTRODUCE_ACK cell to Tor client.");
 200     /* Stop right now, the circuit has been closed. */
 201     return -1;
 202   }
 203
 204   return 0;
 205  err:
 206   /* Send the client a NACK */
 207   nak_body[0] = 1;
 208   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 209                                    RELAY_COMMAND_INTRODUCE_ACK,
 210                                    nak_body, 1, NULL)) {
 211     log_warn(LD_GENERAL, "Unable to send NAK to Tor client.");
 212   }
 213   return -1;
 214 }
 215
 216 /** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and
 217  * rendezvous cookie.
 218  */
 219 int
 220 rend_mid_establish_rendezvous(or_circuit_t *circ, const uint8_t *request,
 221                               size_t request_len)
 222 {
 223   char hexid[9];
 224   int reason = END_CIRC_REASON_TORPROTOCOL;
 225
 226   log_info(LD_REND, "Received an ESTABLISH_RENDEZVOUS request on circuit %u",
 227            (unsigned)circ->p_circ_id);
 228
 229   if (circ->base_.purpose != CIRCUIT_PURPOSE_OR) {
 230     log_warn(LD_PROTOCOL,
 231              "Tried to establish rendezvous on non-OR circuit with purpose %s",
 232              circuit_purpose_to_string(circ->base_.purpose));
 233     goto err;
 234   }
 235
 236   /* Check if we are configured to accept established rendezvous cells from
 237    * client or in other words tor2web clients. */
 238   if (channel_is_client(circ->p_chan) &&
 239       dos_should_refuse_single_hop_client()) {
 240     /* Note it down for the heartbeat log purposes. */
 241     dos_note_refuse_single_hop_client();
 242     /* Silent drop so the client has to time out before moving on. */
 243     return 0;
 244   }
 245
 246   if (circ->base_.n_chan) {
 247     log_warn(LD_PROTOCOL,
 248              "Tried to establish rendezvous on non-edge circuit");
 249     goto err;
 250   }
 251
 252   if (request_len != REND_COOKIE_LEN) {
 253     log_fn(LOG_PROTOCOL_WARN,
 254            LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS.");
 255     goto err;
 256   }
 257
 258   if (hs_circuitmap_get_rend_circ_relay_side(request)) {
 259     log_warn(LD_PROTOCOL,
 260              "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS.");
 261     goto err;
 262   }
 263
 264   /* Acknowledge the request. */
 265   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 266                                    RELAY_COMMAND_RENDEZVOUS_ESTABLISHED,
 267                                    "", 0, NULL)<0) {
 268     log_warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell.");
 269     /* Stop right now, the circuit has been closed. */
 270     return -1;
 271   }
 272
 273   circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_POINT_WAITING);
 274   hs_circuitmap_register_rend_circ_relay_side(circ, request);
 275
 276   base16_encode(hexid,9,(char*)request,4);
 277
 278   log_info(LD_REND,
 279            "Established rendezvous point on circuit %u for cookie %s",
 280            (unsigned)circ->p_circ_id, hexid);
 281
 282   return 0;
 283  err:
 284   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 285   return -1;
 286 }
 287
 288 /** Process a RENDEZVOUS1 cell by looking up the correct rendezvous
 289  * circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and
 290  * connecting the two circuits.
 291  */
 292 int
 293 rend_mid_rendezvous(or_circuit_t *circ, const uint8_t *request,
 294                     size_t request_len)
 295 {
 296   const or_options_t *options = get_options();
 297   or_circuit_t *rend_circ;
 298   char hexid[9];
 299   int reason = END_CIRC_REASON_INTERNAL;
 300
 301   if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {
 302     log_info(LD_REND,
 303              "Tried to complete rendezvous on non-OR or non-edge circuit %u.",
 304              (unsigned)circ->p_circ_id);
 305     reason = END_CIRC_REASON_TORPROTOCOL;
 306     goto err;
 307   }
 308
 309   if (request_len < REND_COOKIE_LEN) {
 310     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 311          "Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %u.",
 312          (int)request_len, (unsigned)circ->p_circ_id);
 313     reason = END_CIRC_REASON_TORPROTOCOL;
 314     goto err;
 315   }
 316
 317   base16_encode(hexid, sizeof(hexid), (const char*)request, 4);
 318
 319   log_info(LD_REND,
 320            "Got request for rendezvous from circuit %u to cookie %s.",
 321            (unsigned)circ->p_circ_id, hexid);
 322
 323   rend_circ = hs_circuitmap_get_rend_circ_relay_side(request);
 324   if (!rend_circ) {
 325     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 326          "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.",
 327          hexid);
 328     reason = END_CIRC_REASON_TORPROTOCOL;
 329     goto err;
 330   }
 331
 332   /* Statistics: Mark this circuit as an RP circuit so that we collect
 333      stats from it. */
 334   if (options->HiddenServiceStatistics) {
 335     circ->circuit_carries_hs_traffic_stats = 1;
 336   }
 337
 338   /* Send the RENDEZVOUS2 cell to the client. */
 339   if (relay_send_command_from_edge(0, TO_CIRCUIT(rend_circ),
 340                                    RELAY_COMMAND_RENDEZVOUS2,
 341                                    (char*)(request+REND_COOKIE_LEN),
 342                                    request_len-REND_COOKIE_LEN, NULL)) {
 343     log_warn(LD_GENERAL,
 344              "Unable to send RENDEZVOUS2 cell to client on circuit %u.",
 345              (unsigned)rend_circ->p_circ_id);
 346     /* Stop right now, the circuit has been closed. */
 347     return -1;
 348   }
 349
 350   /* Join the circuits. */
 351   log_info(LD_REND,
 352            "Completing rendezvous: circuit %u joins circuit %u (cookie %s)",
 353            (unsigned)circ->p_circ_id, (unsigned)rend_circ->p_circ_id, hexid);
 354
 355   circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_ESTABLISHED);
 356   circuit_change_purpose(TO_CIRCUIT(rend_circ),
 357                          CIRCUIT_PURPOSE_REND_ESTABLISHED);
 358   hs_circuitmap_remove_circuit(TO_CIRCUIT(circ));
 359
 360   rend_circ->rend_splice = circ;
 361   circ->rend_splice = rend_circ;
 362
 363   return 0;
 364  err:
 365   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 366   return -1;
 367 }
 368