src/or/rendmid.c

   1 /* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   2  * Copyright (c) 2007-2011, 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
  12 /** Respond to an ESTABLISH_INTRO cell by checking the signed data and
  13  * setting the circuit's purpose and service pk digest.
  14  */
  15 int
  16 rend_mid_establish_intro(or_circuit_t *circ, const uint8_t *request,
  17                          size_t request_len)
  18 {
  19   crypto_pk_env_t *pk = NULL;
  20   char buf[DIGEST_LEN+9];
  21   char expected_digest[DIGEST_LEN];
  22   char pk_digest[DIGEST_LEN];
  23   size_t asn1len;
  24   or_circuit_t *c;
  25   char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
  26   int reason = END_CIRC_REASON_INTERNAL;
  27
  28   log_info(LD_REND,
  29            "Received an ESTABLISH_INTRO request on circuit %d",
  30            circ->p_circ_id);
  31
  32   if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
  33     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
  34          "Rejecting ESTABLISH_INTRO on non-OR or non-edge circuit.");
  35     reason = END_CIRC_REASON_TORPROTOCOL;
  36     goto err;
  37   }
  38   if (request_len < 2+DIGEST_LEN)
  39     goto truncated;
  40   /* First 2 bytes: length of asn1-encoded key. */
  41   asn1len = ntohs(get_uint16(request));
  42
  43   /* Next asn1len bytes: asn1-encoded key. */
  44   if (request_len < 2+DIGEST_LEN+asn1len)
  45     goto truncated;
  46   pk = crypto_pk_asn1_decode((char*)(request+2), asn1len);
  47   if (!pk) {
  48     reason = END_CIRC_REASON_TORPROTOCOL;
  49     log_warn(LD_PROTOCOL, "Couldn't decode public key.");
  50     goto err;
  51   }
  52
  53   /* Next 20 bytes: Hash of handshake_digest | "INTRODUCE" */
  54   memcpy(buf, circ->handshake_digest, DIGEST_LEN);
  55   memcpy(buf+DIGEST_LEN, "INTRODUCE", 9);
  56   if (crypto_digest(expected_digest, buf, DIGEST_LEN+9) < 0) {
  57     log_warn(LD_BUG, "Internal error computing digest.");
  58     goto err;
  59   }
  60   if (memcmp(expected_digest, request+2+asn1len, DIGEST_LEN)) {
  61     log_warn(LD_PROTOCOL, "Hash of session info was not as expected.");
  62     reason = END_CIRC_REASON_TORPROTOCOL;
  63     goto err;
  64   }
  65   /* Rest of body: signature of previous data */
  66   note_crypto_pk_op(REND_MID);
  67   if (crypto_pk_public_checksig_digest(pk,
  68                                        (char*)request, 2+asn1len+DIGEST_LEN,
  69                                        (char*)(request+2+DIGEST_LEN+asn1len),
  70                                        request_len-(2+DIGEST_LEN+asn1len))<0) {
  71     log_warn(LD_PROTOCOL,
  72              "Incorrect signature on ESTABLISH_INTRO cell; rejecting.");
  73     reason = END_CIRC_REASON_TORPROTOCOL;
  74     goto err;
  75   }
  76
  77   /* The request is valid.  First, compute the hash of Bob's PK.*/
  78   if (crypto_pk_get_digest(pk, pk_digest)<0) {
  79     log_warn(LD_BUG, "Internal error: couldn't hash public key.");
  80     goto err;
  81   }
  82
  83   crypto_free_pk_env(pk); /* don't need it anymore */
  84   pk = NULL; /* so we don't free it again if err */
  85
  86   base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
  87                 pk_digest, REND_SERVICE_ID_LEN);
  88
  89   /* Close any other intro circuits with the same pk. */
  90   c = NULL;
  91   while ((c = circuit_get_intro_point(pk_digest))) {
  92     log_info(LD_REND, "Replacing old circuit for service %s",
  93              safe_str(serviceid));
  94     circuit_mark_for_close(TO_CIRCUIT(c), END_CIRC_REASON_FINISHED);
  95     /* Now it's marked, and it won't be returned next time. */
  96   }
  97
  98   /* Acknowledge the request. */
  99   if (relay_send_command_from_edge(0, TO_CIRCUIT(circ),
 100                                    RELAY_COMMAND_INTRO_ESTABLISHED,
 101                                    "", 0, NULL)<0) {
 102     log_info(LD_GENERAL, "Couldn't send INTRO_ESTABLISHED cell.");
 103     goto err;
 104   }
 105
 106   /* Now, set up this circuit. */
 107   circ->_base.purpose = CIRCUIT_PURPOSE_INTRO_POINT;
 108   memcpy(circ->rend_token, pk_digest, DIGEST_LEN);
 109
 110   log_info(LD_REND,
 111            "Established introduction point on circuit %d for service %s",
 112            circ->p_circ_id, safe_str(serviceid));
 113
 114   return 0;
 115  truncated:
 116   log_warn(LD_PROTOCOL, "Rejecting truncated ESTABLISH_INTRO cell.");
 117   reason = END_CIRC_REASON_TORPROTOCOL;
 118  err:
 119   if (pk) crypto_free_pk_env(pk);
 120   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 121   return -1;
 122 }
 123
 124 /** Process an INTRODUCE1 cell by finding the corresponding introduction
 125  * circuit, and relaying the body of the INTRODUCE1 cell inside an
 126  * INTRODUCE2 cell.
 127  */
 128 int
 129 rend_mid_introduce(or_circuit_t *circ, const uint8_t *request,
 130                    size_t request_len)
 131 {
 132   or_circuit_t *intro_circ;
 133   char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
 134   char nak_body[1];
 135
 136   log_info(LD_REND, "Received an INTRODUCE1 request on circuit %d",
 137            circ->p_circ_id);
 138
 139   if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
 140     log_warn(LD_PROTOCOL,
 141              "Rejecting INTRODUCE1 on non-OR or non-edge circuit %d.",
 142              circ->p_circ_id);
 143     goto err;
 144   }
 145
 146   /* We could change this to MAX_HEX_NICKNAME_LEN now that 0.0.9.x is
 147    * obsolete; however, there isn't much reason to do so, and we're going
 148    * to revise this protocol anyway.
 149    */
 150   if (request_len < (DIGEST_LEN+(MAX_NICKNAME_LEN+1)+REND_COOKIE_LEN+
 151                      DH_KEY_LEN+CIPHER_KEY_LEN+PKCS1_OAEP_PADDING_OVERHEAD)) {
 152     log_warn(LD_PROTOCOL, "Impossibly short INTRODUCE1 cell on circuit %d; "
 153              "responding with nack.",
 154              circ->p_circ_id);
 155     goto err;
 156   }
 157
 158   base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
 159                 (char*)request, REND_SERVICE_ID_LEN);
 160
 161   /* The first 20 bytes are all we look at: they have a hash of Bob's PK. */
 162   intro_circ = circuit_get_intro_point((char*)request);
 163   if (!intro_circ) {
 164     log_info(LD_REND,
 165              "No intro circ found for INTRODUCE1 cell (%s) from circuit %d; "
 166              "responding with nack.",
 167              safe_str(serviceid), circ->p_circ_id);
 168     goto err;
 169   }
 170
 171   log_info(LD_REND,
 172            "Sending introduction request for service %s "
 173            "from circ %d to circ %d",
 174            safe_str(serviceid), circ->p_circ_id,
 175            intro_circ->p_circ_id);
 176
 177   /* Great.  Now we just relay the cell down the circuit. */
 178   if (relay_send_command_from_edge(0, TO_CIRCUIT(intro_circ),
 179                                    RELAY_COMMAND_INTRODUCE2,
 180                                    (char*)request, request_len, NULL)) {
 181     log_warn(LD_GENERAL,
 182              "Unable to send INTRODUCE2 cell to Tor client.");
 183     goto err;
 184   }
 185   /* And sent an ack down Alice's circuit.  Empty body means succeeded. */
 186   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 187                                    RELAY_COMMAND_INTRODUCE_ACK,
 188                                    NULL,0,NULL)) {
 189     log_warn(LD_GENERAL, "Unable to send INTRODUCE_ACK cell to Tor client.");
 190     circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
 191     return -1;
 192   }
 193
 194   return 0;
 195  err:
 196   /* Send the client an NACK */
 197   nak_body[0] = 1;
 198   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 199                                    RELAY_COMMAND_INTRODUCE_ACK,
 200                                    nak_body, 1, NULL)) {
 201     log_warn(LD_GENERAL, "Unable to send NAK to Tor client.");
 202     /* Is this right? */
 203     circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
 204   }
 205   return -1;
 206 }
 207
 208 /** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and
 209  * rendezvous cookie.
 210  */
 211 int
 212 rend_mid_establish_rendezvous(or_circuit_t *circ, const uint8_t *request,
 213                               size_t request_len)
 214 {
 215   char hexid[9];
 216   int reason = END_CIRC_REASON_TORPROTOCOL;
 217
 218   log_info(LD_REND, "Received an ESTABLISH_RENDEZVOUS request on circuit %d",
 219            circ->p_circ_id);
 220
 221   if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
 222     log_warn(LD_PROTOCOL,
 223              "Tried to establish rendezvous on non-OR or non-edge circuit.");
 224     goto err;
 225   }
 226
 227   if (request_len != REND_COOKIE_LEN) {
 228     log_warn(LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS.");
 229     goto err;
 230   }
 231
 232   if (circuit_get_rendezvous((char*)request)) {
 233     log_warn(LD_PROTOCOL,
 234              "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS.");
 235     goto err;
 236   }
 237
 238   /* Acknowledge the request. */
 239   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 240                                    RELAY_COMMAND_RENDEZVOUS_ESTABLISHED,
 241                                    "", 0, NULL)<0) {
 242     log_warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell.");
 243     reason = END_CIRC_REASON_INTERNAL;
 244     goto err;
 245   }
 246
 247   circ->_base.purpose = CIRCUIT_PURPOSE_REND_POINT_WAITING;
 248   memcpy(circ->rend_token, request, REND_COOKIE_LEN);
 249
 250   base16_encode(hexid,9,(char*)request,4);
 251
 252   log_info(LD_REND,
 253            "Established rendezvous point on circuit %d for cookie %s",
 254            circ->p_circ_id, hexid);
 255
 256   return 0;
 257  err:
 258   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 259   return -1;
 260 }
 261
 262 /** Process a RENDEZVOUS1 cell by looking up the correct rendezvous
 263  * circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and
 264  * connecting the two circuits.
 265  */
 266 int
 267 rend_mid_rendezvous(or_circuit_t *circ, const uint8_t *request,
 268                     size_t request_len)
 269 {
 270   or_circuit_t *rend_circ;
 271   char hexid[9];
 272   int reason = END_CIRC_REASON_INTERNAL;
 273   base16_encode(hexid,9,(char*)request,request_len<4?request_len:4);
 274
 275   if (request_len>=4) {
 276     log_info(LD_REND,
 277              "Got request for rendezvous from circuit %d to cookie %s.",
 278              circ->p_circ_id, hexid);
 279   }
 280
 281   if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
 282     log_info(LD_REND,
 283              "Tried to complete rendezvous on non-OR or non-edge circuit %d.",
 284              circ->p_circ_id);
 285     reason = END_CIRC_REASON_TORPROTOCOL;
 286     goto err;
 287   }
 288
 289   if (request_len != REND_COOKIE_LEN+DH_KEY_LEN+DIGEST_LEN) {
 290     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 291          "Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %d.",
 292          (int)request_len, circ->p_circ_id);
 293     reason = END_CIRC_REASON_TORPROTOCOL;
 294     goto err;
 295   }
 296
 297   rend_circ = circuit_get_rendezvous((char*)request);
 298   if (!rend_circ) {
 299     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 300          "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.",
 301          hexid);
 302     reason = END_CIRC_REASON_TORPROTOCOL;
 303     goto err;
 304   }
 305
 306   /* Send the RENDEZVOUS2 cell to Alice. */
 307   if (relay_send_command_from_edge(0, TO_CIRCUIT(rend_circ),
 308                                    RELAY_COMMAND_RENDEZVOUS2,
 309                                    (char*)(request+REND_COOKIE_LEN),
 310                                    request_len-REND_COOKIE_LEN, NULL)) {
 311     log_warn(LD_GENERAL,
 312              "Unable to send RENDEZVOUS2 cell to client on circuit %d.",
 313              rend_circ->p_circ_id);
 314     goto err;
 315   }
 316
 317   /* Join the circuits. */
 318   log_info(LD_REND,
 319            "Completing rendezvous: circuit %d joins circuit %d (cookie %s)",
 320            circ->p_circ_id, rend_circ->p_circ_id, hexid);
 321
 322   circ->_base.purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
 323   rend_circ->_base.purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
 324   memset(circ->rend_token, 0, REND_COOKIE_LEN);
 325
 326   rend_circ->rend_splice = circ;
 327   circ->rend_splice = rend_circ;
 328
 329   return 0;
 330  err:
 331   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 332   return -1;
 333 }
 334