src/or/rendmid.c

   1 /* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   2  * Copyright (c) 2007-2009, 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 char *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(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, request, 2+asn1len+DIGEST_LEN,
  68                                        request+2+DIGEST_LEN+asn1len,
  69                                        request_len-(2+DIGEST_LEN+asn1len))<0) {
  70     log_warn(LD_PROTOCOL,
  71              "Incorrect signature on ESTABLISH_INTRO cell; rejecting.");
  72     reason = END_CIRC_REASON_TORPROTOCOL;
  73     goto err;
  74   }
  75
  76   /* The request is valid.  First, compute the hash of Bob's PK.*/
  77   if (crypto_pk_get_digest(pk, pk_digest)<0) {
  78     log_warn(LD_BUG, "Internal error: couldn't hash public key.");
  79     goto err;
  80   }
  81
  82   crypto_free_pk_env(pk); /* don't need it anymore */
  83   pk = NULL; /* so we don't free it again if err */
  84
  85   base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
  86                 pk_digest, REND_SERVICE_ID_LEN);
  87
  88   /* Close any other intro circuits with the same pk. */
  89   c = NULL;
  90   while ((c = circuit_get_intro_point(pk_digest))) {
  91     log_info(LD_REND, "Replacing old circuit for service %s",
  92              safe_str(serviceid));
  93     circuit_mark_for_close(TO_CIRCUIT(c), END_CIRC_REASON_FINISHED);
  94     /* Now it's marked, and it won't be returned next time. */
  95   }
  96
  97   /* Acknowledge the request. */
  98   if (relay_send_command_from_edge(0, TO_CIRCUIT(circ),
  99                                    RELAY_COMMAND_INTRO_ESTABLISHED,
 100                                    "", 0, NULL)<0) {
 101     log_info(LD_GENERAL, "Couldn't send INTRO_ESTABLISHED cell.");
 102     goto err;
 103   }
 104
 105   /* Now, set up this circuit. */
 106   circ->_base.purpose = CIRCUIT_PURPOSE_INTRO_POINT;
 107   memcpy(circ->rend_token, pk_digest, DIGEST_LEN);
 108
 109   log_info(LD_REND,
 110            "Established introduction point on circuit %d for service %s",
 111            circ->p_circ_id, safe_str(serviceid));
 112
 113   return 0;
 114  truncated:
 115   log_warn(LD_PROTOCOL, "Rejecting truncated ESTABLISH_INTRO cell.");
 116   reason = END_CIRC_REASON_TORPROTOCOL;
 117  err:
 118   if (pk) crypto_free_pk_env(pk);
 119   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 120   return -1;
 121 }
 122
 123 /** Process an INTRODUCE1 cell by finding the corresponding introduction
 124  * circuit, and relaying the body of the INTRODUCE1 cell inside an
 125  * INTRODUCE2 cell.
 126  */
 127 int
 128 rend_mid_introduce(or_circuit_t *circ, const char *request, size_t request_len)
 129 {
 130   or_circuit_t *intro_circ;
 131   char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
 132   char nak_body[1];
 133
 134   log_info(LD_REND, "Received an INTRODUCE1 request on circuit %d",
 135            circ->p_circ_id);
 136
 137   if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
 138     log_warn(LD_PROTOCOL,
 139              "Rejecting INTRODUCE1 on non-OR or non-edge circuit %d.",
 140              circ->p_circ_id);
 141     goto err;
 142   }
 143
 144   /* We could change this to MAX_HEX_NICKNAME_LEN now that 0.0.9.x is
 145    * obsolete; however, there isn't much reason to do so, and we're going
 146    * to revise this protocol anyway.
 147    */
 148   if (request_len < (DIGEST_LEN+(MAX_NICKNAME_LEN+1)+REND_COOKIE_LEN+
 149                      DH_KEY_LEN+CIPHER_KEY_LEN+PKCS1_OAEP_PADDING_OVERHEAD)) {
 150     log_warn(LD_PROTOCOL, "Impossibly short INTRODUCE1 cell on circuit %d; "
 151              "responding with nack.",
 152              circ->p_circ_id);
 153     goto err;
 154   }
 155
 156   base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
 157                 request, REND_SERVICE_ID_LEN);
 158
 159   /* The first 20 bytes are all we look at: they have a hash of Bob's PK. */
 160   intro_circ = circuit_get_intro_point(request);
 161   if (!intro_circ) {
 162     log_info(LD_REND,
 163              "No intro circ found for INTRODUCE1 cell (%s) from circuit %d; "
 164              "responding with nack.",
 165              safe_str(serviceid), circ->p_circ_id);
 166     goto err;
 167   }
 168
 169   log_info(LD_REND,
 170            "Sending introduction request for service %s "
 171            "from circ %d to circ %d",
 172            safe_str(serviceid), circ->p_circ_id,
 173            intro_circ->p_circ_id);
 174
 175   /* Great.  Now we just relay the cell down the circuit. */
 176   if (relay_send_command_from_edge(0, TO_CIRCUIT(intro_circ),
 177                                    RELAY_COMMAND_INTRODUCE2,
 178                                    request, request_len, NULL)) {
 179     log_warn(LD_GENERAL,
 180              "Unable to send INTRODUCE2 cell to Tor client.");
 181     goto err;
 182   }
 183   /* And sent an ack down Alice's circuit.  Empty body means succeeded. */
 184   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 185                                    RELAY_COMMAND_INTRODUCE_ACK,
 186                                    NULL,0,NULL)) {
 187     log_warn(LD_GENERAL, "Unable to send INTRODUCE_ACK cell to Tor client.");
 188     circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
 189     return -1;
 190   }
 191
 192   return 0;
 193  err:
 194   /* Send the client an NACK */
 195   nak_body[0] = 1;
 196   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 197                                    RELAY_COMMAND_INTRODUCE_ACK,
 198                                    nak_body, 1, NULL)) {
 199     log_warn(LD_GENERAL, "Unable to send NAK to Tor client.");
 200     /* Is this right? */
 201     circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
 202   }
 203   return -1;
 204 }
 205
 206 /** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and
 207  * rendezvous cookie.
 208  */
 209 int
 210 rend_mid_establish_rendezvous(or_circuit_t *circ, const char *request,
 211                               size_t request_len)
 212 {
 213   char hexid[9];
 214   int reason = END_CIRC_REASON_TORPROTOCOL;
 215
 216   log_info(LD_REND, "Received an ESTABLISH_RENDEZVOUS request on circuit %d",
 217            circ->p_circ_id);
 218
 219   if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
 220     log_warn(LD_PROTOCOL,
 221              "Tried to establish rendezvous on non-OR or non-edge circuit.");
 222     goto err;
 223   }
 224
 225   if (request_len != REND_COOKIE_LEN) {
 226     log_warn(LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS.");
 227     goto err;
 228   }
 229
 230   if (circuit_get_rendezvous(request)) {
 231     log_warn(LD_PROTOCOL,
 232              "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS.");
 233     goto err;
 234   }
 235
 236   /* Acknowledge the request. */
 237   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 238                                    RELAY_COMMAND_RENDEZVOUS_ESTABLISHED,
 239                                    "", 0, NULL)<0) {
 240     log_warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell.");
 241     reason = END_CIRC_REASON_INTERNAL;
 242     goto err;
 243   }
 244
 245   circ->_base.purpose = CIRCUIT_PURPOSE_REND_POINT_WAITING;
 246   memcpy(circ->rend_token, request, REND_COOKIE_LEN);
 247
 248   base16_encode(hexid,9,request,4);
 249
 250   log_info(LD_REND,
 251            "Established rendezvous point on circuit %d for cookie %s",
 252            circ->p_circ_id, hexid);
 253
 254   return 0;
 255  err:
 256   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 257   return -1;
 258 }
 259
 260 /** Process a RENDEZVOUS1 cell by looking up the correct rendezvous
 261  * circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and
 262  * connecting the two circuits.
 263  */
 264 int
 265 rend_mid_rendezvous(or_circuit_t *circ, const char *request,
 266                     size_t request_len)
 267 {
 268   or_circuit_t *rend_circ;
 269   char hexid[9];
 270   int reason = END_CIRC_REASON_INTERNAL;
 271   base16_encode(hexid,9,request,request_len<4?request_len:4);
 272
 273   if (request_len>=4) {
 274     log_info(LD_REND,
 275              "Got request for rendezvous from circuit %d to cookie %s.",
 276              circ->p_circ_id, hexid);
 277   }
 278
 279   if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
 280     log_info(LD_REND,
 281              "Tried to complete rendezvous on non-OR or non-edge circuit %d.",
 282              circ->p_circ_id);
 283     reason = END_CIRC_REASON_TORPROTOCOL;
 284     goto err;
 285   }
 286
 287   if (request_len != REND_COOKIE_LEN+DH_KEY_LEN+DIGEST_LEN) {
 288     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 289          "Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %d.",
 290          (int)request_len, circ->p_circ_id);
 291     reason = END_CIRC_REASON_TORPROTOCOL;
 292     goto err;
 293   }
 294
 295   rend_circ = circuit_get_rendezvous(request);
 296   if (!rend_circ) {
 297     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 298          "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.",
 299          hexid);
 300     reason = END_CIRC_REASON_TORPROTOCOL;
 301     goto err;
 302   }
 303
 304   /* Send the RENDEZVOUS2 cell to Alice. */
 305   if (relay_send_command_from_edge(0, TO_CIRCUIT(rend_circ),
 306                                    RELAY_COMMAND_RENDEZVOUS2,
 307                                    request+REND_COOKIE_LEN,
 308                                    request_len-REND_COOKIE_LEN, NULL)) {
 309     log_warn(LD_GENERAL,
 310              "Unable to send RENDEZVOUS2 cell to client on circuit %d.",
 311              rend_circ->p_circ_id);
 312     goto err;
 313   }
 314
 315   /* Join the circuits. */
 316   log_info(LD_REND,
 317            "Completing rendezvous: circuit %d joins circuit %d (cookie %s)",
 318            circ->p_circ_id, rend_circ->p_circ_id, hexid);
 319
 320   circ->_base.purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
 321   rend_circ->_base.purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
 322   memset(circ->rend_token, 0, REND_COOKIE_LEN);
 323
 324   rend_circ->rend_splice = circ;
 325   circ->rend_splice = rend_circ;
 326
 327   return 0;
 328  err:
 329   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 330   return -1;
 331 }
 332