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