src/or/rendmid.c

   1 /* Copyright 2004-2005 Roger Dingledine, Nick Mathewson. */
   2 /* See LICENSE for licensing information */
   3 /* $Id$ */
   4 const char rendmid_c_id[] =
   5   "$Id$";
   6
   7 /**
   8  * \file rendmid.c
   9  * \brief Implement introductions points and rendezvous points.
  10  **/
  11
  12 #include "or.h"
  13
  14 /** Respond to an ESTABLISH_INTRO cell by checking the signed data and
  15  * setting the circuit's purpose and service pk digest.
  16  */
  17 int
  18 rend_mid_establish_intro(circuit_t *circ, const char *request,
  19                          size_t request_len)
  20 {
  21   crypto_pk_env_t *pk = NULL;
  22   char buf[DIGEST_LEN+9];
  23   char expected_digest[DIGEST_LEN];
  24   char pk_digest[DIGEST_LEN];
  25   size_t asn1len;
  26   circuit_t *c;
  27   char serviceid[REND_SERVICE_ID_LEN+1];
  28   int reason = END_CIRC_REASON_INTERNAL;
  29
  30   info(LD_REND,
  31        "Received an ESTABLISH_INTRO request on circuit %d", circ->p_circ_id);
  32
  33   if (circ->purpose != CIRCUIT_PURPOSE_OR || circ->n_conn) {
  34     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
  35          "Rejecting ESTABLISH_INTRO on non-OR or non-edge circuit.");
  36     reason = END_CIRC_REASON_TORPROTOCOL;
  37     goto err;
  38   }
  39   if (request_len < 2+DIGEST_LEN)
  40     goto truncated;
  41   /* First 2 bytes: length of asn1-encoded key. */
  42   asn1len = ntohs(get_uint16(request));
  43
  44   /* Next asn1len bytes: asn1-encoded key. */
  45   if (request_len < 2+DIGEST_LEN+asn1len)
  46     goto truncated;
  47   pk = crypto_pk_asn1_decode(request+2, asn1len);
  48   if (!pk) {
  49     reason = END_CIRC_REASON_TORPROTOCOL;
  50     warn(LD_PROTOCOL, "Couldn't decode public key.");
  51     goto err;
  52   }
  53
  54   /* Next 20 bytes: Hash of handshake_digest | "INTRODUCE" */
  55   memcpy(buf, circ->handshake_digest, DIGEST_LEN);
  56   memcpy(buf+DIGEST_LEN, "INTRODUCE", 9);
  57   if (crypto_digest(expected_digest, buf, DIGEST_LEN+9) < 0) {
  58     warn(LD_BUG, "Internal error computing digest.");
  59     goto err;
  60   }
  61   if (memcmp(expected_digest, request+2+asn1len, DIGEST_LEN)) {
  62     warn(LD_PROTOCOL, "Hash of session info was not as expected.");
  63     reason = END_CIRC_REASON_TORPROTOCOL;
  64     goto err;
  65   }
  66   /* Rest of body: signature of previous data */
  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     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     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+1, pk_digest,10);
  86
  87   /* Close any other intro circuits with the same pk. */
  88   c = NULL;
  89   while ((c = circuit_get_next_by_pk_and_purpose(
  90                                 c,pk_digest,CIRCUIT_PURPOSE_INTRO_POINT))) {
  91     info(LD_REND, "Replacing old circuit %d for service %s",
  92          c->p_circ_id, safe_str(serviceid));
  93     circuit_mark_for_close(c, END_CIRC_REASON_REQUESTED);
  94   }
  95
  96   /* Acknowledge the request. */
  97   if (connection_edge_send_command(NULL,circ,
  98                                    RELAY_COMMAND_INTRO_ESTABLISHED,
  99                                    "", 0, NULL)<0) {
 100     info(LD_GENERAL, "Couldn't send INTRO_ESTABLISHED cell.");
 101     goto err;
 102   }
 103
 104   /* Now, set up this circuit. */
 105   circ->purpose = CIRCUIT_PURPOSE_INTRO_POINT;
 106   memcpy(circ->rend_pk_digest, pk_digest, DIGEST_LEN);
 107
 108   info(LD_REND,
 109        "Established introduction point on circuit %d for service %s",
 110        circ->p_circ_id, safe_str(serviceid));
 111
 112   return 0;
 113  truncated:
 114   warn(LD_PROTOCOL, "Rejecting truncated ESTABLISH_INTRO cell.");
 115   reason = END_CIRC_REASON_TORPROTOCOL;
 116  err:
 117   if (pk) crypto_free_pk_env(pk);
 118   circuit_mark_for_close(circ, reason);
 119   return -1;
 120 }
 121
 122 /** Process an INTRODUCE1 cell by finding the corresponding introduction
 123  * circuit, and relaying the body of the INTRODUCE1 cell inside an
 124  * INTRODUCE2 cell.
 125  */
 126 int
 127 rend_mid_introduce(circuit_t *circ, const char *request, size_t request_len)
 128 {
 129   circuit_t *intro_circ;
 130   char serviceid[REND_SERVICE_ID_LEN+1];
 131   char nak_body[1];
 132
 133   if (circ->purpose != CIRCUIT_PURPOSE_OR || circ->n_conn) {
 134     warn(LD_PROTOCOL, "Rejecting INTRODUCE1 on non-OR or non-edge circuit %d.",
 135          circ->p_circ_id);
 136     goto err;
 137   }
 138
 139   /* change to MAX_HEX_NICKNAME_LEN once 0.0.9.x is obsolete */
 140   if (request_len < (DIGEST_LEN+(MAX_NICKNAME_LEN+1)+REND_COOKIE_LEN+
 141                      DH_KEY_LEN+CIPHER_KEY_LEN+PKCS1_OAEP_PADDING_OVERHEAD)) {
 142     warn(LD_PROTOCOL, "Impossibly short INTRODUCE1 cell on circuit %d; "
 143          "responding with nack.",
 144          circ->p_circ_id);
 145     goto err;
 146   }
 147
 148   base32_encode(serviceid, REND_SERVICE_ID_LEN+1, request,10);
 149
 150   /* The first 20 bytes are all we look at: they have a hash of Bob's PK. */
 151   intro_circ = circuit_get_next_by_pk_and_purpose(
 152                              NULL, request, CIRCUIT_PURPOSE_INTRO_POINT);
 153   if (!intro_circ) {
 154     info(LD_REND,
 155          "No intro circ found for INTRODUCE1 cell (%s) from circuit %d; "
 156          "responding with nack.",
 157          safe_str(serviceid), circ->p_circ_id);
 158     goto err;
 159   }
 160
 161   info(LD_REND,
 162        "Sending introduction request for service %s from circ %d to circ %d",
 163        safe_str(serviceid), circ->p_circ_id, intro_circ->p_circ_id);
 164
 165   /* Great.  Now we just relay the cell down the circuit. */
 166   if (connection_edge_send_command(NULL, intro_circ,
 167                                    RELAY_COMMAND_INTRODUCE2,
 168                                    request, request_len, NULL)) {
 169     warn(LD_GENERAL,
 170          "Unable to send INTRODUCE2 cell to Tor client.");
 171     goto err;
 172   }
 173   /* And sent an ack down Alice's circuit.  Empty body means succeeded. */
 174   if (connection_edge_send_command(NULL,circ,RELAY_COMMAND_INTRODUCE_ACK,
 175                                    NULL,0,NULL)) {
 176     warn(LD_GENERAL, "Unable to send INTRODUCE_ACK cell to Tor client.");
 177     circuit_mark_for_close(circ, END_CIRC_REASON_INTERNAL);
 178     return -1;
 179   }
 180
 181   return 0;
 182  err:
 183   /* Send the client an NACK */
 184   nak_body[0] = 1;
 185   if (connection_edge_send_command(NULL,circ,RELAY_COMMAND_INTRODUCE_ACK,
 186                                    nak_body, 1, NULL)) {
 187     warn(LD_GENERAL, "Unable to send NAK to Tor client.");
 188     /* Is this right? */
 189     circuit_mark_for_close(circ, END_CIRC_REASON_INTERNAL);
 190   }
 191   return -1;
 192 }
 193
 194 /** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and
 195  * rendezvous cookie.
 196  */
 197 int
 198 rend_mid_establish_rendezvous(circuit_t *circ, const char *request,
 199                               size_t request_len)
 200 {
 201   char hexid[9];
 202   int reason = END_CIRC_REASON_TORPROTOCOL;
 203
 204   if (circ->purpose != CIRCUIT_PURPOSE_OR || circ->n_conn) {
 205     warn(LD_PROTOCOL,
 206          "Tried to establish rendezvous on non-OR or non-edge circuit.");
 207     goto err;
 208   }
 209
 210   if (request_len != REND_COOKIE_LEN) {
 211     warn(LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS.");
 212     goto err;
 213   }
 214
 215   if (circuit_get_rendezvous(request)) {
 216     warn(LD_PROTOCOL, "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS.");
 217     goto err;
 218   }
 219
 220   /* Acknowledge the request. */
 221   if (connection_edge_send_command(NULL,circ,
 222                                    RELAY_COMMAND_RENDEZVOUS_ESTABLISHED,
 223                                    "", 0, NULL)<0) {
 224     warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell.");
 225     reason = END_CIRC_REASON_INTERNAL;
 226     goto err;
 227   }
 228
 229   circ->purpose = CIRCUIT_PURPOSE_REND_POINT_WAITING;
 230   memcpy(circ->rend_cookie, request, REND_COOKIE_LEN);
 231
 232   base16_encode(hexid,9,request,4);
 233
 234   info(LD_REND, "Established rendezvous point on circuit %d for cookie %s",
 235        circ->p_circ_id, hexid);
 236
 237   return 0;
 238  err:
 239   circuit_mark_for_close(circ, reason);
 240   return -1;
 241 }
 242
 243 /** Process a RENDEZVOUS1 cell by looking up the correct rendezvous
 244  * circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and
 245  * connecting the two circuits.
 246  */
 247 int
 248 rend_mid_rendezvous(circuit_t *circ, const char *request, size_t request_len)
 249 {
 250   circuit_t *rend_circ;
 251   char hexid[9];
 252   int reason = END_CIRC_REASON_INTERNAL;
 253   base16_encode(hexid,9,request,request_len<4?request_len:4);
 254
 255   if (request_len>=4) {
 256     info(LD_REND, "Got request for rendezvous from circuit %d to cookie %s.",
 257          circ->p_circ_id, hexid);
 258   }
 259
 260   if (circ->purpose != CIRCUIT_PURPOSE_OR || circ->n_conn) {
 261     info(LD_REND,
 262          "Tried to complete rendezvous on non-OR or non-edge circuit %d.",
 263          circ->p_circ_id);
 264     reason = END_CIRC_REASON_TORPROTOCOL;
 265     goto err;
 266   }
 267
 268   if (request_len != REND_COOKIE_LEN+DH_KEY_LEN+DIGEST_LEN) {
 269     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 270          "Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %d.",
 271          (int)request_len, circ->p_circ_id);
 272     reason = END_CIRC_REASON_TORPROTOCOL;
 273     goto err;
 274   }
 275
 276   rend_circ = circuit_get_rendezvous(request);
 277   if (!rend_circ) {
 278     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
 279          "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.",
 280          hexid);
 281     reason = END_CIRC_REASON_TORPROTOCOL;
 282     goto err;
 283   }
 284
 285   /* Send the RENDEZVOUS2 cell to Alice. */
 286   if (connection_edge_send_command(NULL, rend_circ,
 287                                    RELAY_COMMAND_RENDEZVOUS2,
 288                                    request+REND_COOKIE_LEN,
 289                                    request_len-REND_COOKIE_LEN, NULL)) {
 290     warn(LD_GENERAL,
 291          "Unable to send RENDEZVOUS2 cell to OP on circuit %d.",
 292          rend_circ->p_circ_id);
 293     goto err;
 294   }
 295
 296   /* Join the circuits. */
 297   info(LD_REND,
 298        "Completing rendezvous: circuit %d joins circuit %d (cookie %s)",
 299        circ->p_circ_id, rend_circ->p_circ_id, hexid);
 300
 301   circ->purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
 302   rend_circ->purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
 303   memset(circ->rend_cookie, 0, REND_COOKIE_LEN);
 304
 305   rend_circ->rend_splice = circ;
 306   circ->rend_splice = rend_circ;
 307
 308   return 0;
 309  err:
 310   circuit_mark_for_close(circ, reason);
 311   return -1;
 312 }
 313