src/or/rendmid.c

   1 /* Copyright 2004 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 #include "or.h"
  12
  13 /** Respond to an ESTABLISH_INTRO cell by checking the signed data and
  14  * setting the circuit's purpose and service pk digest.
  15  */
  16 int
  17 rend_mid_establish_intro(circuit_t *circ, const char *request, 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   circuit_t *c;
  25   char serviceid[REND_SERVICE_ID_LEN+1];
  26
  27   log_fn(LOG_INFO,
  28          "Received an ESTABLISH_INTRO request on circuit %d", circ->p_circ_id);
  29
  30   if (circ->purpose != CIRCUIT_PURPOSE_OR || circ->n_conn) {
  31     log_fn(LOG_WARN, "Rejecting ESTABLISH_INTRO on non-OR or non-edge circuit");
  32     goto err;
  33   }
  34   if (request_len < 2+DIGEST_LEN)
  35     goto truncated;
  36   /* First 2 bytes: length of asn1-encoded key. */
  37   asn1len = ntohs(get_uint16(request));
  38
  39   /* Next asn1len bytes: asn1-encoded key. */
  40   if (request_len < 2+DIGEST_LEN+asn1len)
  41     goto truncated;
  42   pk = crypto_pk_asn1_decode(request+2, asn1len);
  43   if (!pk) {
  44     log_fn(LOG_WARN, "Couldn't decode public key");
  45     goto err;
  46   }
  47
  48   /* Next 20 bytes: Hash of handshake_digest | "INTRODUCE" */
  49   memcpy(buf, circ->handshake_digest, DIGEST_LEN);
  50   memcpy(buf+DIGEST_LEN, "INTRODUCE", 9);
  51   if (crypto_digest(expected_digest, buf, DIGEST_LEN+9) < 0) {
  52     log_fn(LOG_WARN, "Error computing digest");
  53     goto err;
  54   }
  55   if (memcmp(expected_digest, request+2+asn1len, DIGEST_LEN)) {
  56     log_fn(LOG_WARN, "Hash of session info was not as expected");
  57     goto err;
  58   }
  59   /* Rest of body: signature of previous data */
  60   if (crypto_pk_public_checksig_digest(pk, request, 2+asn1len+DIGEST_LEN,
  61                                        request+2+DIGEST_LEN+asn1len,
  62                                        request_len-(2+DIGEST_LEN+asn1len))<0) {
  63     log_fn(LOG_WARN, "Incorrect signature on ESTABLISH_INTRO cell; rejecting");
  64     goto err;
  65   }
  66
  67   /* The request is valid.  First, compute the hash of Bob's PK.*/
  68   if (crypto_pk_get_digest(pk, pk_digest)<0) {
  69     log_fn(LOG_WARN, "Couldn't hash public key.");
  70     goto err;
  71   }
  72
  73   base32_encode(serviceid, REND_SERVICE_ID_LEN+1, pk_digest,10);
  74
  75   /* Close any other intro circuits with the same pk. */
  76   c = NULL;
  77   while ((c = circuit_get_next_by_pk_and_purpose(
  78                                 c,pk_digest,CIRCUIT_PURPOSE_INTRO_POINT))) {
  79     log_fn(LOG_INFO, "Replacing old circuit %d for service %s",
  80            c->p_circ_id, serviceid);
  81     circuit_mark_for_close(c);
  82   }
  83
  84   /* Acknowledge the request. */
  85   if (connection_edge_send_command(NULL,circ,
  86                                    RELAY_COMMAND_INTRO_ESTABLISHED,
  87                                    "", 0, NULL)<0) {
  88     log_fn(LOG_WARN, "Couldn't send INTRO_ESTABLISHED cell");
  89     goto err;
  90   }
  91
  92   /* Now, set up this circuit. */
  93   circ->purpose = CIRCUIT_PURPOSE_INTRO_POINT;
  94   memcpy(circ->rend_pk_digest, pk_digest, DIGEST_LEN);
  95
  96   log_fn(LOG_INFO,
  97          "Established introduction point on circuit %d for service %s",
  98          circ->p_circ_id, serviceid);
  99
 100   return 0;
 101  truncated:
 102   log_fn(LOG_WARN, "Rejecting truncated ESTABLISH_INTRO cell");
 103  err:
 104   if (pk) crypto_free_pk_env(pk);
 105   circuit_mark_for_close(circ);
 106   return -1;
 107 }
 108
 109 /** Process an INTRODUCE1 cell by finding the corresponding introduction
 110  * circuit, and relaying the body of the INTRODUCE1 cell inside an
 111  * INTRODUCE2 cell.
 112  */
 113 int
 114 rend_mid_introduce(circuit_t *circ, const char *request, size_t request_len)
 115 {
 116   circuit_t *intro_circ;
 117   char serviceid[REND_SERVICE_ID_LEN+1];
 118   char nak_body[1];
 119
 120   if (circ->purpose != CIRCUIT_PURPOSE_OR || circ->n_conn) {
 121     log_fn(LOG_WARN, "Rejecting INTRODUCE1 on non-OR or non-edge circuit %d",
 122            circ->p_circ_id);
 123     goto err;
 124   }
 125
 126   /* change to MAX_HEX_NICKNAME_LEN once 0.0.9.x is obsolete */
 127   if (request_len < (DIGEST_LEN+(MAX_NICKNAME_LEN+1)+REND_COOKIE_LEN+
 128                      DH_KEY_LEN+CIPHER_KEY_LEN+PKCS1_OAEP_PADDING_OVERHEAD)) {
 129     log_fn(LOG_WARN,
 130            "Impossibly short INTRODUCE1 cell on circuit %d; responding with nack.",
 131            circ->p_circ_id);
 132     goto err;
 133   }
 134
 135   base32_encode(serviceid, REND_SERVICE_ID_LEN+1, request,10);
 136
 137   /* The first 20 bytes are all we look at: they have a hash of Bob's PK. */
 138   intro_circ = circuit_get_next_by_pk_and_purpose(
 139                              NULL, request, CIRCUIT_PURPOSE_INTRO_POINT);
 140   if (!intro_circ) {
 141     log_fn(LOG_WARN,
 142            "No intro circ found for INTRODUCE1 cell (%s) from circuit %d; responding with nack",
 143            serviceid, circ->p_circ_id);
 144     goto err;
 145   }
 146
 147   log_fn(LOG_INFO,
 148          "Sending introduction request for service %s from circ %d to circ %d",
 149          serviceid, circ->p_circ_id, intro_circ->p_circ_id);
 150
 151   /* Great.  Now we just relay the cell down the circuit. */
 152   if (connection_edge_send_command(NULL, intro_circ,
 153                                    RELAY_COMMAND_INTRODUCE2,
 154                                    request, request_len, NULL)) {
 155     log_fn(LOG_WARN, "Unable to send INTRODUCE2 cell to OP.");
 156     goto err;
 157   }
 158   /* And sent an ack down Alice's circuit.  Empty body means succeeded. */
 159   if (connection_edge_send_command(NULL,circ,RELAY_COMMAND_INTRODUCE_ACK,
 160                                    NULL,0,NULL)) {
 161     log_fn(LOG_WARN, "Unable to send INTRODUCE_ACK cell to OP.");
 162     circuit_mark_for_close(circ);
 163     return -1;
 164   }
 165
 166   return 0;
 167  err:
 168   /* Send the client an NACK */
 169   nak_body[0] = 1;
 170   if (connection_edge_send_command(NULL,circ,RELAY_COMMAND_INTRODUCE_ACK,
 171                                    nak_body, 1, NULL)) {
 172     log_fn(LOG_WARN, "Unable to send NAK to OP");
 173     circuit_mark_for_close(circ); /* Is this right? */
 174   }
 175   return -1;
 176 }
 177
 178 /** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and
 179  * rendezvous cookie.
 180  */
 181 int
 182 rend_mid_establish_rendezvous(circuit_t *circ, const char *request, size_t request_len)
 183 {
 184   char hexid[9];
 185
 186   if (circ->purpose != CIRCUIT_PURPOSE_OR || circ->n_conn) {
 187     log_fn(LOG_WARN, "Tried to establish rendezvous on non-OR or non-edge circuit");
 188     goto err;
 189   }
 190
 191   if (request_len != REND_COOKIE_LEN) {
 192     log_fn(LOG_WARN, "Invalid length on ESTABLISH_RENDEZVOUS");
 193     goto err;
 194   }
 195
 196   if (circuit_get_rendezvous(request)) {
 197     log_fn(LOG_WARN, "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS");
 198     goto err;
 199   }
 200
 201   /* Acknowledge the request. */
 202   if (connection_edge_send_command(NULL,circ,
 203                                    RELAY_COMMAND_RENDEZVOUS_ESTABLISHED,
 204                                    "", 0, NULL)<0) {
 205     log_fn(LOG_WARN, "Couldn't send RENDEZVOUS_ESTABLISHED cell");
 206     goto err;
 207   }
 208
 209   circ->purpose = CIRCUIT_PURPOSE_REND_POINT_WAITING;
 210   memcpy(circ->rend_cookie, request, REND_COOKIE_LEN);
 211
 212   base16_encode(hexid,9,request,4);
 213
 214   log_fn(LOG_INFO, "Established rendezvous point on circuit %d for cookie %s",
 215          circ->p_circ_id, hexid);
 216
 217   return 0;
 218  err:
 219   circuit_mark_for_close(circ);
 220   return -1;
 221 }
 222
 223 /** Process a RENDEZVOUS1 cell by looking up the correct rendezvous
 224  * circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and
 225  * connecting the two circuits.
 226  */
 227 int
 228 rend_mid_rendezvous(circuit_t *circ, const char *request, size_t request_len)
 229 {
 230   circuit_t *rend_circ;
 231   char hexid[9];
 232
 233   base16_encode(hexid,9,request,request_len<4?request_len:4);
 234
 235   if (request_len>=4) {
 236     log_fn(LOG_INFO, "Got request for rendezvous from circuit %d to cookie %s",
 237            circ->p_circ_id, hexid);
 238   }
 239
 240   if (circ->purpose != CIRCUIT_PURPOSE_OR || circ->n_conn) {
 241     log_fn(LOG_WARN,
 242            "Tried to complete rendezvous on non-OR or non-edge circuit %d",
 243            circ->p_circ_id);
 244     goto err;
 245   }
 246
 247   if (request_len != REND_COOKIE_LEN+DH_KEY_LEN+DIGEST_LEN) {
 248     log_fn(LOG_WARN,
 249            "Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %d",
 250            (int)request_len, circ->p_circ_id);
 251     goto err;
 252   }
 253
 254   rend_circ = circuit_get_rendezvous(request);
 255   if (!rend_circ) {
 256     log_fn(LOG_WARN,
 257            "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s",
 258            hexid);
 259     goto err;
 260   }
 261
 262   /* Send the RENDEZVOUS2 cell to Alice. */
 263   if (connection_edge_send_command(NULL, rend_circ,
 264                                    RELAY_COMMAND_RENDEZVOUS2,
 265                                    request+REND_COOKIE_LEN,
 266                                    request_len-REND_COOKIE_LEN, NULL)) {
 267     log_fn(LOG_WARN, "Unable to send RENDEZVOUS2 cell to OP on circuit %d",
 268            rend_circ->p_circ_id);
 269     goto err;
 270   }
 271
 272   /* Join the circuits. */
 273   log_fn(LOG_INFO,
 274          "Completing rendezvous: circuit %d joins circuit %d (cookie %s)",
 275          circ->p_circ_id, rend_circ->p_circ_id, hexid);
 276
 277   circ->purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
 278   rend_circ->purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
 279   memset(circ->rend_cookie, 0, REND_COOKIE_LEN);
 280
 281   rend_circ->rend_splice = circ;
 282   circ->rend_splice = rend_circ;
 283
 284   return 0;
 285  err:
 286   circuit_mark_for_close(circ);
 287   return -1;
 288 }
 289