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[] = "$Id$";
   5
   6 /**
   7  * \file rendmid.c
   8  * \brief Implement introductions points and rendezvous points.
   9  **/
  10
  11 #define NEW_LOG_INTERFACE
  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, size_t request_len)
  19 {
  20   crypto_pk_env_t *pk = NULL;
  21   char buf[DIGEST_LEN+9];
  22   char expected_digest[DIGEST_LEN];
  23   char pk_digest[DIGEST_LEN];
  24   size_t asn1len;
  25   circuit_t *c;
  26   char serviceid[REND_SERVICE_ID_LEN+1];
  27
  28   info(LD_REND,
  29        "Received an ESTABLISH_INTRO request on circuit %d", circ->p_circ_id);
  30
  31   if (circ->purpose != CIRCUIT_PURPOSE_OR || circ->n_conn) {
  32     warn(LD_PROTOCOL, "Rejecting ESTABLISH_INTRO on non-OR or non-edge circuit.");
  33     goto err;
  34   }
  35   if (request_len < 2+DIGEST_LEN)
  36     goto truncated;
  37   /* First 2 bytes: length of asn1-encoded key. */
  38   asn1len = ntohs(get_uint16(request));
  39
  40   /* Next asn1len bytes: asn1-encoded key. */
  41   if (request_len < 2+DIGEST_LEN+asn1len)
  42     goto truncated;
  43   pk = crypto_pk_asn1_decode(request+2, asn1len);
  44   if (!pk) {
  45     warn(LD_PROTOCOL, "Couldn't decode public key.");
  46     goto err;
  47   }
  48
  49   /* Next 20 bytes: Hash of handshake_digest | "INTRODUCE" */
  50   memcpy(buf, circ->handshake_digest, DIGEST_LEN);
  51   memcpy(buf+DIGEST_LEN, "INTRODUCE", 9);
  52   if (crypto_digest(expected_digest, buf, DIGEST_LEN+9) < 0) {
  53     warn(LD_BUG, "Internal error computing digest.");
  54     goto err;
  55   }
  56   if (memcmp(expected_digest, request+2+asn1len, DIGEST_LEN)) {
  57     warn(LD_PROTOCOL, "Hash of session info was not as expected.");
  58     goto err;
  59   }
  60   /* Rest of body: signature of previous data */
  61   if (crypto_pk_public_checksig_digest(pk, request, 2+asn1len+DIGEST_LEN,
  62                                        request+2+DIGEST_LEN+asn1len,
  63                                        request_len-(2+DIGEST_LEN+asn1len))<0) {
  64     warn(LD_PROTOCOL, "Incorrect signature on ESTABLISH_INTRO cell; rejecting.");
  65     goto err;
  66   }
  67
  68   /* The request is valid.  First, compute the hash of Bob's PK.*/
  69   if (crypto_pk_get_digest(pk, pk_digest)<0) {
  70     warn(LD_BUG, "Internal error: couldn't hash public key.");
  71     goto err;
  72   }
  73
  74   crypto_free_pk_env(pk); /* don't need it anymore */
  75   pk = NULL; /* so we don't free it again if err */
  76
  77   base32_encode(serviceid, REND_SERVICE_ID_LEN+1, pk_digest,10);
  78
  79   /* Close any other intro circuits with the same pk. */
  80   c = NULL;
  81   while ((c = circuit_get_next_by_pk_and_purpose(
  82                                 c,pk_digest,CIRCUIT_PURPOSE_INTRO_POINT))) {
  83     info(LD_REND, "Replacing old circuit %d for service %s",
  84            c->p_circ_id, safe_str(serviceid));
  85     circuit_mark_for_close(c);
  86   }
  87
  88   /* Acknowledge the request. */
  89   if (connection_edge_send_command(NULL,circ,
  90                                    RELAY_COMMAND_INTRO_ESTABLISHED,
  91                                    "", 0, NULL)<0) {
  92     info(LD_GENERAL, "Couldn't send INTRO_ESTABLISHED cell.");
  93     goto err;
  94   }
  95
  96   /* Now, set up this circuit. */
  97   circ->purpose = CIRCUIT_PURPOSE_INTRO_POINT;
  98   memcpy(circ->rend_pk_digest, pk_digest, DIGEST_LEN);
  99
 100   info(LD_REND,
 101        "Established introduction point on circuit %d for service %s",
 102        circ->p_circ_id, safe_str(serviceid));
 103
 104   return 0;
 105  truncated:
 106   warn(LD_PROTOCOL, "Rejecting truncated ESTABLISH_INTRO cell.");
 107  err:
 108   if (pk) crypto_free_pk_env(pk);
 109   circuit_mark_for_close(circ);
 110   return -1;
 111 }
 112
 113 /** Process an INTRODUCE1 cell by finding the corresponding introduction
 114  * circuit, and relaying the body of the INTRODUCE1 cell inside an
 115  * INTRODUCE2 cell.
 116  */
 117 int
 118 rend_mid_introduce(circuit_t *circ, const char *request, size_t request_len)
 119 {
 120   circuit_t *intro_circ;
 121   char serviceid[REND_SERVICE_ID_LEN+1];
 122   char nak_body[1];
 123
 124   if (circ->purpose != CIRCUIT_PURPOSE_OR || circ->n_conn) {
 125     warn(LD_PROTOCOL, "Rejecting INTRODUCE1 on non-OR or non-edge circuit %d.",
 126            circ->p_circ_id);
 127     goto err;
 128   }
 129
 130   /* change to MAX_HEX_NICKNAME_LEN once 0.0.9.x is obsolete */
 131   if (request_len < (DIGEST_LEN+(MAX_NICKNAME_LEN+1)+REND_COOKIE_LEN+
 132                      DH_KEY_LEN+CIPHER_KEY_LEN+PKCS1_OAEP_PADDING_OVERHEAD)) {
 133     warn(LD_PROTOCOL,
 134          "Impossibly short INTRODUCE1 cell on circuit %d; responding with nack.",
 135          circ->p_circ_id);
 136     goto err;
 137   }
 138
 139   base32_encode(serviceid, REND_SERVICE_ID_LEN+1, request,10);
 140
 141   /* The first 20 bytes are all we look at: they have a hash of Bob's PK. */
 142   intro_circ = circuit_get_next_by_pk_and_purpose(
 143                              NULL, request, CIRCUIT_PURPOSE_INTRO_POINT);
 144   if (!intro_circ) {
 145     info(LD_REND,
 146          "No intro circ found for INTRODUCE1 cell (%s) from circuit %d; responding with nack.",
 147          safe_str(serviceid), circ->p_circ_id);
 148     goto err;
 149   }
 150
 151   info(LD_REND,
 152        "Sending introduction request for service %s from circ %d to circ %d",
 153        safe_str(serviceid), circ->p_circ_id, intro_circ->p_circ_id);
 154
 155   /* Great.  Now we just relay the cell down the circuit. */
 156   if (connection_edge_send_command(NULL, intro_circ,
 157                                    RELAY_COMMAND_INTRODUCE2,
 158                                    request, request_len, NULL)) {
 159     warn(LD_GENERAL,
 160          "Unable to send INTRODUCE2 cell to Tor client.");
 161     goto err;
 162   }
 163   /* And sent an ack down Alice's circuit.  Empty body means succeeded. */
 164   if (connection_edge_send_command(NULL,circ,RELAY_COMMAND_INTRODUCE_ACK,
 165                                    NULL,0,NULL)) {
 166     warn(LD_GENERAL, "Unable to send INTRODUCE_ACK cell to Tor client.");
 167     circuit_mark_for_close(circ);
 168     return -1;
 169   }
 170
 171   return 0;
 172  err:
 173   /* Send the client an NACK */
 174   nak_body[0] = 1;
 175   if (connection_edge_send_command(NULL,circ,RELAY_COMMAND_INTRODUCE_ACK,
 176                                    nak_body, 1, NULL)) {
 177     warn(LD_GENERAL, "Unable to send NAK to Tor client.");
 178     circuit_mark_for_close(circ); /* Is this right? */
 179   }
 180   return -1;
 181 }
 182
 183 /** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and
 184  * rendezvous cookie.
 185  */
 186 int
 187 rend_mid_establish_rendezvous(circuit_t *circ, const char *request, size_t request_len)
 188 {
 189   char hexid[9];
 190
 191   if (circ->purpose != CIRCUIT_PURPOSE_OR || circ->n_conn) {
 192     warn(LD_PROTOCOL, "Tried to establish rendezvous on non-OR or non-edge circuit.");
 193     goto err;
 194   }
 195
 196   if (request_len != REND_COOKIE_LEN) {
 197     warn(LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS.");
 198     goto err;
 199   }
 200
 201   if (circuit_get_rendezvous(request)) {
 202     warn(LD_PROTOCOL, "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS.");
 203     goto err;
 204   }
 205
 206   /* Acknowledge the request. */
 207   if (connection_edge_send_command(NULL,circ,
 208                                    RELAY_COMMAND_RENDEZVOUS_ESTABLISHED,
 209                                    "", 0, NULL)<0) {
 210     warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell.");
 211     goto err;
 212   }
 213
 214   circ->purpose = CIRCUIT_PURPOSE_REND_POINT_WAITING;
 215   memcpy(circ->rend_cookie, request, REND_COOKIE_LEN);
 216
 217   base16_encode(hexid,9,request,4);
 218
 219   info(LD_REND, "Established rendezvous point on circuit %d for cookie %s",
 220          circ->p_circ_id, hexid);
 221
 222   return 0;
 223  err:
 224   circuit_mark_for_close(circ);
 225   return -1;
 226 }
 227
 228 /** Process a RENDEZVOUS1 cell by looking up the correct rendezvous
 229  * circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and
 230  * connecting the two circuits.
 231  */
 232 int
 233 rend_mid_rendezvous(circuit_t *circ, const char *request, size_t request_len)
 234 {
 235   circuit_t *rend_circ;
 236   char hexid[9];
 237
 238   base16_encode(hexid,9,request,request_len<4?request_len:4);
 239
 240   if (request_len>=4) {
 241     info(LD_REND, "Got request for rendezvous from circuit %d to cookie %s.",
 242            circ->p_circ_id, hexid);
 243   }
 244
 245   if (circ->purpose != CIRCUIT_PURPOSE_OR || circ->n_conn) {
 246     info(LD_REND,
 247          "Tried to complete rendezvous on non-OR or non-edge circuit %d.",
 248          circ->p_circ_id);
 249     goto err;
 250   }
 251
 252   if (request_len != REND_COOKIE_LEN+DH_KEY_LEN+DIGEST_LEN) {
 253     warn(LD_PROTOCOL,
 254          "Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %d.",
 255          (int)request_len, circ->p_circ_id);
 256     goto err;
 257   }
 258
 259   rend_circ = circuit_get_rendezvous(request);
 260   if (!rend_circ) {
 261     warn(LD_PROTOCOL,
 262          "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.",
 263          hexid);
 264     goto err;
 265   }
 266
 267   /* Send the RENDEZVOUS2 cell to Alice. */
 268   if (connection_edge_send_command(NULL, rend_circ,
 269                                    RELAY_COMMAND_RENDEZVOUS2,
 270                                    request+REND_COOKIE_LEN,
 271                                    request_len-REND_COOKIE_LEN, NULL)) {
 272     warn(LD_GENERAL,
 273          "Unable to send RENDEZVOUS2 cell to OP on circuit %d.",
 274          rend_circ->p_circ_id);
 275     goto err;
 276   }
 277
 278   /* Join the circuits. */
 279   info(LD_REND,
 280        "Completing rendezvous: circuit %d joins circuit %d (cookie %s)",
 281        circ->p_circ_id, rend_circ->p_circ_id, hexid);
 282
 283   circ->purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
 284   rend_circ->purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
 285   memset(circ->rend_cookie, 0, REND_COOKIE_LEN);
 286
 287   rend_circ->rend_splice = circ;
 288   circ->rend_splice = rend_circ;
 289
 290   return 0;
 291  err:
 292   circuit_mark_for_close(circ);
 293   return -1;
 294 }
 295