src/or/rendmid.c

   1 /* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   2  * Copyright (c) 2007-2010, 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 "config.h"
  13 #include "relay.h"
  14 #include "rendmid.h"
  15 #include "rephist.h"
  16
  17 /** Respond to an ESTABLISH_INTRO cell by checking the signed data and
  18  * setting the circuit's purpose and service pk digest.
  19  */
  20 int
  21 rend_mid_establish_intro(or_circuit_t *circ, const char *request,
  22                          size_t request_len)
  23 {
  24   crypto_pk_env_t *pk = NULL;
  25   char buf[DIGEST_LEN+9];
  26   char expected_digest[DIGEST_LEN];
  27   char pk_digest[DIGEST_LEN];
  28   size_t asn1len;
  29   or_circuit_t *c;
  30   char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
  31   int reason = END_CIRC_REASON_INTERNAL;
  32
  33   log_info(LD_REND,
  34            "Received an ESTABLISH_INTRO request on circuit %d",
  35            circ->p_circ_id);
  36
  37   if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
  38     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
  39          "Rejecting ESTABLISH_INTRO on non-OR or non-edge circuit.");
  40     reason = END_CIRC_REASON_TORPROTOCOL;
  41     goto err;
  42   }
  43   if (request_len < 2+DIGEST_LEN)
  44     goto truncated;
  45   /* First 2 bytes: length of asn1-encoded key. */
  46   asn1len = ntohs(get_uint16(request));
  47
  48   /* Next asn1len bytes: asn1-encoded key. */
  49   if (request_len < 2+DIGEST_LEN+asn1len)
  50     goto truncated;
  51   pk = crypto_pk_asn1_decode(request+2, asn1len);
  52   if (!pk) {
  53     reason = END_CIRC_REASON_TORPROTOCOL;
  54     log_warn(LD_PROTOCOL, "Couldn't decode public key.");
  55     goto err;
  56   }
  57
  58   /* Next 20 bytes: Hash of handshake_digest | "INTRODUCE" */
  59   memcpy(buf, circ->handshake_digest, DIGEST_LEN);
  60   memcpy(buf+DIGEST_LEN, "INTRODUCE", 9);
  61   if (crypto_digest(expected_digest, buf, DIGEST_LEN+9) < 0) {
  62     log_warn(LD_BUG, "Internal error computing digest.");
  63     goto err;
  64   }
  65   if (memcmp(expected_digest, request+2+asn1len, DIGEST_LEN)) {
  66     log_warn(LD_PROTOCOL, "Hash of session info was not as expected.");
  67     reason = END_CIRC_REASON_TORPROTOCOL;
  68     goto err;
  69   }
  70   /* Rest of body: signature of previous data */
  71   note_crypto_pk_op(REND_MID);
  72   if (crypto_pk_public_checksig_digest(pk, request, 2+asn1len+DIGEST_LEN,
  73                                        request+2+DIGEST_LEN+asn1len,
  74                                        request_len-(2+DIGEST_LEN+asn1len))<0) {
  75     log_warn(LD_PROTOCOL,
  76              "Incorrect signature on ESTABLISH_INTRO cell; rejecting.");
  77     reason = END_CIRC_REASON_TORPROTOCOL;
  78     goto err;
  79   }
  80
  81   /* The request is valid.  First, compute the hash of Bob's PK.*/
  82   if (crypto_pk_get_digest(pk, pk_digest)<0) {
  83     log_warn(LD_BUG, "Internal error: couldn't hash public key.");
  84     goto err;
  85   }
  86
  87   crypto_free_pk_env(pk); /* don't need it anymore */
  88   pk = NULL; /* so we don't free it again if err */
  89
  90   base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
  91                 pk_digest, REND_SERVICE_ID_LEN);
  92
  93   /* Close any other intro circuits with the same pk. */
  94   c = NULL;
  95   while ((c = circuit_get_intro_point(pk_digest))) {
  96     log_info(LD_REND, "Replacing old circuit for service %s",
  97              safe_str(serviceid));
  98     circuit_mark_for_close(TO_CIRCUIT(c), END_CIRC_REASON_FINISHED);
  99     /* Now it's marked, and it won't be returned next time. */
 100   }
 101
 102   /* Acknowledge the request. */
 103   if (relay_send_command_from_edge(0, TO_CIRCUIT(circ),
 104                                    RELAY_COMMAND_INTRO_ESTABLISHED,
 105                                    "", 0, NULL)<0) {
 106     log_info(LD_GENERAL, "Couldn't send INTRO_ESTABLISHED cell.");
 107     goto err;
 108   }
 109
 110   /* Now, set up this circuit. */
 111   circ->_base.purpose = CIRCUIT_PURPOSE_INTRO_POINT;
 112   memcpy(circ->rend_token, pk_digest, DIGEST_LEN);
 113
 114   log_info(LD_REND,
 115            "Established introduction point on circuit %d for service %s",
 116            circ->p_circ_id, safe_str(serviceid));
 117
 118   return 0;
 119  truncated:
 120   log_warn(LD_PROTOCOL, "Rejecting truncated ESTABLISH_INTRO cell.");
 121   reason = END_CIRC_REASON_TORPROTOCOL;
 122  err:
 123   if (pk) crypto_free_pk_env(pk);
 124   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 125   return -1;
 126 }
 127
 128 /** Process an INTRODUCE1 cell by finding the corresponding introduction
 129  * circuit, and relaying the body of the INTRODUCE1 cell inside an
 130  * INTRODUCE2 cell.
 131  */
 132 int
 133 rend_mid_introduce(or_circuit_t *circ, const char *request, size_t request_len)
 134 {
 135   or_circuit_t *intro_circ;
 136   char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
 137   char nak_body[1];
 138
 139   log_info(LD_REND, "Received an INTRODUCE1 request on circuit %d",
 140            circ->p_circ_id);
 141
 142   if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
 143     log_warn(LD_PROTOCOL,
 144              "Rejecting INTRODUCE1 on non-OR or non-edge circuit %d.",
 145              circ->p_circ_id);
 146     goto err;
 147   }
 148
 149   /* We could change this to MAX_HEX_NICKNAME_LEN now that 0.0.9.x is
 150    * obsolete; however, there isn't much reason to do so, and we're going
 151    * to revise this protocol anyway.
 152    */
 153   if (request_len < (DIGEST_LEN+(MAX_NICKNAME_LEN+1)+REND_COOKIE_LEN+
 154                      DH_KEY_LEN+CIPHER_KEY_LEN+PKCS1_OAEP_PADDING_OVERHEAD)) {
 155     log_warn(LD_PROTOCOL, "Impossibly short INTRODUCE1 cell on circuit %d; "
 156              "responding with nack.",
 157              circ->p_circ_id);
 158     goto err;
 159   }
 160
 161   base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
 162                 request, REND_SERVICE_ID_LEN);
 163
 164   /* The first 20 bytes are all we look at: they have a hash of Bob's PK. */
 165   intro_circ = circuit_get_intro_point(request);
 166   if (!intro_circ) {
 167     log_info(LD_REND,
 168              "No intro circ found for INTRODUCE1 cell (%s) from circuit %d; "
 169              "responding with nack.",
 170              safe_str(serviceid), circ->p_circ_id);
 171     goto err;
 172   }
 173
 174   log_info(LD_REND,
 175            "Sending introduction request for service %s "
 176            "from circ %d to circ %d",
 177            safe_str(serviceid), circ->p_circ_id,
 178            intro_circ->p_circ_id);
 179
 180   /* Great.  Now we just relay the cell down the circuit. */
 181   if (relay_send_command_from_edge(0, TO_CIRCUIT(intro_circ),
 182                                    RELAY_COMMAND_INTRODUCE2,
 183                                    request, request_len, NULL)) {
 184     log_warn(LD_GENERAL,
 185              "Unable to send INTRODUCE2 cell to Tor client.");
 186     goto err;
 187   }
 188   /* And sent an ack down Alice's circuit.  Empty body means succeeded. */
 189   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 190                                    RELAY_COMMAND_INTRODUCE_ACK,
 191                                    NULL,0,NULL)) {
 192     log_warn(LD_GENERAL, "Unable to send INTRODUCE_ACK cell to Tor client.");
 193     circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
 194     return -1;
 195   }
 196
 197   return 0;
 198  err:
 199   /* Send the client an NACK */
 200   nak_body[0] = 1;
 201   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 202                                    RELAY_COMMAND_INTRODUCE_ACK,
 203                                    nak_body, 1, NULL)) {
 204     log_warn(LD_GENERAL, "Unable to send NAK to Tor client.");
 205     /* Is this right? */
 206     circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
 207   }
 208   return -1;
 209 }
 210
 211 /** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and
 212  * rendezvous cookie.
 213  */
 214 int
 215 rend_mid_establish_rendezvous(or_circuit_t *circ, const char *request,
 216                               size_t request_len)
 217 {
 218   char hexid[9];
 219   int reason = END_CIRC_REASON_TORPROTOCOL;
 220
 221   log_info(LD_REND, "Received an ESTABLISH_RENDEZVOUS request on circuit %d",
 222            circ->p_circ_id);
 223
 224   if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
 225     log_warn(LD_PROTOCOL,
 226              "Tried to establish rendezvous on non-OR or non-edge circuit.");
 227     goto err;
 228   }
 229
 230   if (request_len != REND_COOKIE_LEN) {
 231     log_warn(LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS.");
 232     goto err;
 233   }
 234
 235   if (circuit_get_rendezvous(request)) {
 236     log_warn(LD_PROTOCOL,
 237              "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS.");
 238     goto err;
 239   }
 240
 241   /* Acknowledge the request. */
 242   if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
 243                                    RELAY_COMMAND_RENDEZVOUS_ESTABLISHED,
 244                                    "", 0, NULL)<0) {
 245     log_warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell.");
 246     reason = END_CIRC_REASON_INTERNAL;
 247     goto err;
 248   }
 249
 250   circ->_base.purpose = CIRCUIT_PURPOSE_REND_POINT_WAITING;
 251   memcpy(circ->rend_token, request, REND_COOKIE_LEN);
 252
 253   base16_encode(hexid,9,request,4);
 254
 255   log_info(LD_REND,
 256            "Established rendezvous point on circuit %d for cookie %s",
 257            circ->p_circ_id, hexid);
 258
 259   return 0;
 260  err:
 261   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 262   return -1;
 263 }
 264
 265 /** Process a RENDEZVOUS1 cell by looking up the correct rendezvous
 266  * circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and
 267  * connecting the two circuits.
 268  */
 269 int
 270 rend_mid_rendezvous(or_circuit_t *circ, const char *request,
 271                     size_t request_len)
 272 {
 273   or_circuit_t *rend_circ;
 274   char hexid[9];
 275   int reason = END_CIRC_REASON_INTERNAL;
 276   base16_encode(hexid,9,request,request_len<4?request_len:4);
 277
 278   if (request_len>=4) {
 279     log_info(LD_REND,
 280              "Got request for rendezvous from circuit %d to cookie %s.",
 281              circ->p_circ_id, hexid);
 282   }
 283
 284   if (circ->_base.purpose != CIRCUIT_PURPOSE_OR || circ->_base.n_conn) {
 285     log_info(LD_REND,
 286              "Tried to complete rendezvous on non-OR or non-edge circuit %d.",
 287              circ->p_circ_id);
 288     reason = END_CIRC_REASON_TORPROTOCOL;
 289     goto err;
 290   }
 291
 292   if (request_len != REND_COOKIE_LEN+DH_KEY_LEN+DIGEST_LEN) {
 293     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 294          "Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %d.",
 295          (int)request_len, circ->p_circ_id);
 296     reason = END_CIRC_REASON_TORPROTOCOL;
 297     goto err;
 298   }
 299
 300   rend_circ = circuit_get_rendezvous(request);
 301   if (!rend_circ) {
 302     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 303          "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.",
 304          hexid);
 305     reason = END_CIRC_REASON_TORPROTOCOL;
 306     goto err;
 307   }
 308
 309   /* Send the RENDEZVOUS2 cell to Alice. */
 310   if (relay_send_command_from_edge(0, TO_CIRCUIT(rend_circ),
 311                                    RELAY_COMMAND_RENDEZVOUS2,
 312                                    request+REND_COOKIE_LEN,
 313                                    request_len-REND_COOKIE_LEN, NULL)) {
 314     log_warn(LD_GENERAL,
 315              "Unable to send RENDEZVOUS2 cell to client on circuit %d.",
 316              rend_circ->p_circ_id);
 317     goto err;
 318   }
 319
 320   /* Join the circuits. */
 321   log_info(LD_REND,
 322            "Completing rendezvous: circuit %d joins circuit %d (cookie %s)",
 323            circ->p_circ_id, rend_circ->p_circ_id, hexid);
 324
 325   circ->_base.purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
 326   rend_circ->_base.purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
 327   memset(circ->rend_token, 0, REND_COOKIE_LEN);
 328
 329   rend_circ->rend_splice = circ;
 330   circ->rend_splice = rend_circ;
 331
 332   return 0;
 333  err:
 334   circuit_mark_for_close(TO_CIRCUIT(circ), reason);
 335   return -1;
 336 }
 337