src/feature/rend/rendmid.c

   1 /* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   2  * Copyright (c) 2007-2019, 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 "core/or/or.h"
  11 #include "core/or/channel.h"
  12 #include "core/or/circuitlist.h"
  13 #include "core/or/circuituse.h"
  14 #include "app/config/config.h"
  15 #include "lib/crypt_ops/crypto_cipher.h"
  16 #include "core/or/dos.h"
  17 #include "core/or/relay.h"
  18 #include "feature/rend/rendmid.h"
  19 #include "feature/stats/rephist.h"
  20 #include "feature/hs/hs_circuitmap.h"
  21 #include "feature/hs/hs_intropoint.h"
  22
  23 #include "core/or/or_circuit_st.h"
  24
  25 /** Respond to an ESTABLISH_INTRO cell by checking the signed data and
  26  * setting the circuit's purpose and service pk digest.
  27  */
  28 int
  29 rend_mid_establish_intro_legacy(or_circuit_t *circ, const uint8_t *request,
  30                                 size_t request_len)
  31 {
  32   crypto_pk_t *pk = NULL;
  33   char buf[DIGEST_LEN+9];
  34   char expected_digest[DIGEST_LEN];
  35   char pk_digest[DIGEST_LEN];
  36   size_t asn1len;
  37   or_circuit_t *c;
  38   char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
  39   int reason = END_CIRC_REASON_INTERNAL;
  40
  41   log_info(LD_REND,
  42            "Received a legacy ESTABLISH_INTRO request on circuit %u",
  43            (unsigned) circ->p_circ_id);
  44
  45   if (!hs_intro_circuit_is_suitable_for_establish_intro(circ)) {
  46     reason = END_CIRC_REASON_TORPROTOCOL;
  47     goto err;
  48   }
  49
  50   if (request_len < 2+DIGEST_LEN)
  51     goto truncated;
  52   /* First 2 bytes: length of asn1-encoded key. */
  53   asn1len = ntohs(get_uint16(request));
  54
  55   /* Next asn1len bytes: asn1-encoded key. */
  56   if (request_len < 2+DIGEST_LEN+asn1len)
  57     goto truncated;
  58   pk = crypto_pk_asn1_decode((char*)(request+2), asn1len);
  59   if (!pk) {
  60     reason = END_CIRC_REASON_TORPROTOCOL;
  61     log_warn(LD_PROTOCOL, "Couldn't decode public key.");
  62     goto err;
  63   }
  64
  65   /* Next 20 bytes: Hash of rend_circ_nonce | "INTRODUCE" */
  66   memcpy(buf, circ->rend_circ_nonce, DIGEST_LEN);
  67   memcpy(buf+DIGEST_LEN, "INTRODUCE", 9);
  68   if (crypto_digest(expected_digest, buf, DIGEST_LEN+9) < 0) {
  69     log_warn(LD_BUG, "Internal error computing digest.");
  70     goto err;
  71   }
  72   if (tor_memneq(expected_digest, request+2+asn1len, DIGEST_LEN)) {
  73     log_warn(LD_PROTOCOL, "Hash of session info was not as expected.");
  74     reason = END_CIRC_REASON_TORPROTOCOL;
  75     goto err;
  76   }
  77   /* Rest of body: signature of previous data */
  78   if (crypto_pk_public_checksig_digest(pk,
  79                                        (char*)request, 2+asn1len+DIGEST_LEN,
  80                                        (char*)(request+2+DIGEST_LEN+asn1len),
  81                                        request_len-(2+DIGEST_LEN+asn1len))<0) {
  82     log_warn(LD_PROTOCOL,
  83              "Incorrect signature on ESTABLISH_INTRO cell; rejecting.");
  84     reason = END_CIRC_REASON_TORPROTOCOL;
  85     goto err;
  86   }
  87
  88   /* The request is valid.  First, compute the hash of the service's PK.*/
  89   if (crypto_pk_get_digest(pk, pk_digest)<0) {
  90     log_warn(LD_BUG, "Internal error: couldn't hash public key.");
  91     goto err;
  92   }
  93
  94   crypto_pk_free(pk); /* don't need it anymore */
  95   pk = NULL; /* so we don't free it again if err */
  96
  97   base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
  98                 pk_digest, REND_SERVICE_ID_LEN);
  99
 100   /* Close any other intro circuits with the same pk. */
 101   c = NULL;
 102   while ((c = hs_circuitmap_get_intro_circ_v2_relay_side(
 103                                                 (const uint8_t *)pk_digest))) {
 104     log_info(LD_REND, "Replacing old circuit for service %s",
 105              safe_str(serviceid));
 106     circuit_mark_for_close(TO_CIRCUIT(c), END_CIRC_REASON_FINISHED);
 107     /* Now it's marked, and it won't be returned next time. */
 108   }
 109
 110   /* Acknowledge the request. */
 111   if (hs_intro_send_intro_established_cell(circ) < 0) {
 112     log_info(LD_GENERAL, "Couldn't send INTRO_ESTABLISHED cell.");
 113     goto err_no_close;
 114   }
 115
 116   /* Now, set up this circuit. */
 117   circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_INTRO_POINT);
 118   hs_circuitmap_register_intro_circ_v2_relay_side(circ, (uint8_t *)pk_digest);
 119
 120   log_info(LD_REND,
 121            "Established introduction point on circuit %u for service %s",
 122            (unsigned) circ->p_circ_id, safe_str(serviceid));
 123
 124   return 0;
 125  truncated:
 126   log_warn(LD_PROTOCOL, "Rejecting truncated ESTABLISH_INTRO cell.");
 127   reason = END_CIRC_REASON_TORPROTOCOL;
 128  err:
 129   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 130  err_no_close:
 131   if (pk) crypto_pk_free(pk);
 132   return -1;
 133 }
 134
 135 /** Process an INTRODUCE1 cell by finding the corresponding introduction
 136  * circuit, and relaying the body of the INTRODUCE1 cell inside an
 137  * INTRODUCE2 cell.
 138  */
 139 int
 140 rend_mid_introduce_legacy(or_circuit_t *circ, const uint8_t *request,
 141                           size_t request_len)
 142 {
 143   or_circuit_t *intro_circ;
 144   char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
 145   char nak_body[1];
 146
 147   log_info(LD_REND, "Received an INTRODUCE1 request on circuit %u",
 148            (unsigned)circ->p_circ_id);
 149
 150   /* At this point, we know that the circuit is valid for an INTRODUCE1
 151    * because the validation has been made before calling this function. */
 152   tor_assert(circ->base_.purpose == CIRCUIT_PURPOSE_OR);
 153   tor_assert(!circ->base_.n_chan);
 154
 155   /* We could change this to MAX_HEX_NICKNAME_LEN now that 0.0.9.x is
 156    * obsolete; however, there isn't much reason to do so, and we're going
 157    * to revise this protocol anyway.
 158    */
 159   if (request_len < (DIGEST_LEN+(MAX_NICKNAME_LEN+1)+REND_COOKIE_LEN+
 160                      DH1024_KEY_LEN+CIPHER_KEY_LEN+
 161                      PKCS1_OAEP_PADDING_OVERHEAD)) {
 162     log_warn(LD_PROTOCOL, "Impossibly short INTRODUCE1 cell on circuit %u; "
 163              "responding with nack.",
 164              (unsigned)circ->p_circ_id);
 165     goto err;
 166   }
 167
 168   base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
 169                 (char*)request, REND_SERVICE_ID_LEN);
 170
 171   /* The first 20 bytes are all we look at: they have a hash of the service's
 172    * PK. */
 173   intro_circ = hs_circuitmap_get_intro_circ_v2_relay_side(
 174                                                       (const uint8_t*)request);
 175   if (!intro_circ) {
 176     log_info(LD_REND,
 177              "No intro circ found for INTRODUCE1 cell (%s) from circuit %u; "
 178              "responding with nack.",
 179              safe_str(serviceid), (unsigned)circ->p_circ_id);
 180     goto err;
 181   }
 182
 183   log_info(LD_REND,
 184            "Sending introduction request for service %s "
 185            "from circ %u to circ %u",
 186            safe_str(serviceid), (unsigned)circ->p_circ_id,
 187            (unsigned)intro_circ->p_circ_id);
 188
 189   /* Great.  Now we just relay the cell down the circuit. */
 190   if (relay_send_command_from_edge(0, TO_CIRCUIT(intro_circ),
 191                                    RELAY_COMMAND_INTRODUCE2,
 192                                    (char*)request, request_len, NULL)) {
 193     log_warn(LD_GENERAL,
 194              "Unable to send INTRODUCE2 cell to Tor client.");
 195     /* Stop right now, the circuit has been closed. */
 196     return -1;
 197   }
 198   /* And send an ack down the client's circuit.  Empty body means succeeded. */
 199   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 200                                    RELAY_COMMAND_INTRODUCE_ACK,
 201                                    NULL,0,NULL)) {
 202     log_warn(LD_GENERAL, "Unable to send INTRODUCE_ACK cell to Tor client.");
 203     /* Stop right now, the circuit has been closed. */
 204     return -1;
 205   }
 206
 207   return 0;
 208  err:
 209   /* Send the client a NACK */
 210   nak_body[0] = 1;
 211   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 212                                    RELAY_COMMAND_INTRODUCE_ACK,
 213                                    nak_body, 1, NULL)) {
 214     log_warn(LD_GENERAL, "Unable to send NAK to Tor client.");
 215   }
 216   return -1;
 217 }
 218
 219 /** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and
 220  * rendezvous cookie.
 221  */
 222 int
 223 rend_mid_establish_rendezvous(or_circuit_t *circ, const uint8_t *request,
 224                               size_t request_len)
 225 {
 226   char hexid[9];
 227   int reason = END_CIRC_REASON_TORPROTOCOL;
 228
 229   log_info(LD_REND, "Received an ESTABLISH_RENDEZVOUS request on circuit %u",
 230            (unsigned)circ->p_circ_id);
 231
 232   if (circ->base_.purpose != CIRCUIT_PURPOSE_OR) {
 233     log_warn(LD_PROTOCOL,
 234              "Tried to establish rendezvous on non-OR circuit with purpose %s",
 235              circuit_purpose_to_string(circ->base_.purpose));
 236     goto err;
 237   }
 238
 239   /* Check if we are configured to defend ourselves from clients that
 240    * attempt to establish rendezvous points directly to us. */
 241   if (channel_is_client(circ->p_chan) &&
 242       dos_should_refuse_single_hop_client()) {
 243     /* Note it down for the heartbeat log purposes. */
 244     dos_note_refuse_single_hop_client();
 245     /* Silent drop so the client has to time out before moving on. */
 246     return 0;
 247   }
 248
 249   if (circ->base_.n_chan) {
 250     log_warn(LD_PROTOCOL,
 251              "Tried to establish rendezvous on non-edge circuit");
 252     goto err;
 253   }
 254
 255   if (request_len != REND_COOKIE_LEN) {
 256     log_fn(LOG_PROTOCOL_WARN,
 257            LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS.");
 258     goto err;
 259   }
 260
 261   if (hs_circuitmap_get_rend_circ_relay_side(request)) {
 262     log_warn(LD_PROTOCOL,
 263              "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS.");
 264     goto err;
 265   }
 266
 267   /* Acknowledge the request. */
 268   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 269                                    RELAY_COMMAND_RENDEZVOUS_ESTABLISHED,
 270                                    "", 0, NULL)<0) {
 271     log_warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell.");
 272     /* Stop right now, the circuit has been closed. */
 273     return -1;
 274   }
 275
 276   circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_POINT_WAITING);
 277   hs_circuitmap_register_rend_circ_relay_side(circ, request);
 278
 279   base16_encode(hexid,9,(char*)request,4);
 280
 281   log_info(LD_REND,
 282            "Established rendezvous point on circuit %u for cookie %s",
 283            (unsigned)circ->p_circ_id, hexid);
 284
 285   return 0;
 286  err:
 287   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 288   return -1;
 289 }
 290
 291 /** Process a RENDEZVOUS1 cell by looking up the correct rendezvous
 292  * circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and
 293  * connecting the two circuits.
 294  */
 295 int
 296 rend_mid_rendezvous(or_circuit_t *circ, const uint8_t *request,
 297                     size_t request_len)
 298 {
 299   const or_options_t *options = get_options();
 300   or_circuit_t *rend_circ;
 301   char hexid[9];
 302   int reason = END_CIRC_REASON_INTERNAL;
 303
 304   if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {
 305     log_info(LD_REND,
 306              "Tried to complete rendezvous on non-OR or non-edge circuit %u.",
 307              (unsigned)circ->p_circ_id);
 308     reason = END_CIRC_REASON_TORPROTOCOL;
 309     goto err;
 310   }
 311
 312   if (request_len < REND_COOKIE_LEN) {
 313     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 314          "Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %u.",
 315          (int)request_len, (unsigned)circ->p_circ_id);
 316     reason = END_CIRC_REASON_TORPROTOCOL;
 317     goto err;
 318   }
 319
 320   base16_encode(hexid, sizeof(hexid), (const char*)request, 4);
 321
 322   log_info(LD_REND,
 323            "Got request for rendezvous from circuit %u to cookie %s.",
 324            (unsigned)circ->p_circ_id, hexid);
 325
 326   rend_circ = hs_circuitmap_get_rend_circ_relay_side(request);
 327   if (!rend_circ) {
 328     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 329          "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.",
 330          hexid);
 331     reason = END_CIRC_REASON_TORPROTOCOL;
 332     goto err;
 333   }
 334
 335   /* Statistics: Mark this circuit as an RP circuit so that we collect
 336      stats from it. */
 337   if (options->HiddenServiceStatistics) {
 338     circ->circuit_carries_hs_traffic_stats = 1;
 339   }
 340
 341   /* Send the RENDEZVOUS2 cell to the client. */
 342   if (relay_send_command_from_edge(0, TO_CIRCUIT(rend_circ),
 343                                    RELAY_COMMAND_RENDEZVOUS2,
 344                                    (char*)(request+REND_COOKIE_LEN),
 345                                    request_len-REND_COOKIE_LEN, NULL)) {
 346     log_warn(LD_GENERAL,
 347              "Unable to send RENDEZVOUS2 cell to client on circuit %u.",
 348              (unsigned)rend_circ->p_circ_id);
 349     /* Stop right now, the circuit has been closed. */
 350     return -1;
 351   }
 352
 353   /* Join the circuits. */
 354   log_info(LD_REND,
 355            "Completing rendezvous: circuit %u joins circuit %u (cookie %s)",
 356            (unsigned)circ->p_circ_id, (unsigned)rend_circ->p_circ_id, hexid);
 357
 358   circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_ESTABLISHED);
 359   circuit_change_purpose(TO_CIRCUIT(rend_circ),
 360                          CIRCUIT_PURPOSE_REND_ESTABLISHED);
 361   hs_circuitmap_remove_circuit(TO_CIRCUIT(circ));
 362
 363   rend_circ->rend_splice = circ;
 364   circ->rend_splice = rend_circ;
 365
 366   return 0;
 367  err:
 368   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 369   return -1;
 370 }