src/or/rendmid.c

   1 /* Copyright 2004 Roger Dingledine */
   2 /* See LICENSE for licensing information */
   3 /* $Id$ */
   4
   5 #include "or.h"
   6
   7 /* Respond to an ESTABLISH_INTRO cell by setting the circuit's purpose and
   8  * rendevous service.
   9  */
  10 int
  11 rend_mid_establish_intro(circuit_t *circ, char *request, int request_len)
  12 {
  13   crypto_pk_env_t *pk = NULL;
  14   char buf[20+9];
  15   char expected_digest[20];
  16   char pk_digest[20];
  17   int asn1len;
  18   circuit_t *c;
  19
  20   if (circ->purpose != CIRCUIT_PURPOSE_INTERMEDIATE) {
  21     log_fn(LOG_WARN, "Rejecting ESTABLISH_INTRO on non-intermediate circuit");
  22     goto err;
  23   }
  24   if (request_len < 22)
  25     goto truncated;
  26   /* First 2 bytes: length of asn1-encoded key. */
  27   asn1len = get_uint16(request);
  28
  29   /* Next asn1len bytes: asn1-encoded key. */
  30   if (request_len < 22+asn1len)
  31     goto truncated;
  32   pk = crypto_pk_asn1_decode(request+2, asn1len);
  33   if (!pk) {
  34     log_fn(LOG_WARN, "Couldn't decode public key");
  35     goto err;
  36   }
  37
  38   /* Next 20 bytes: Hash of handshake_digest | "INTRODUCE" */
  39   memcpy(buf, circ->handshake_digest, 20);
  40   memcpy(buf+20, "INTRODUCE", 9);
  41   if (crypto_SHA_digest(buf, 29, expected_digest)<0) {
  42     log_fn(LOG_WARN, "Error computing digest");
  43     goto err;
  44   }
  45   if (memcmp(expected_digest, buf+2+asn1len, 20)) {
  46     log_fn(LOG_WARN, "Hash of session info was not as expected");
  47     goto err;
  48   }
  49
  50   /* Rest of body: signature of previous data */
  51   if (crypto_pk_public_checksig_digest(pk, buf, 22+asn1len,
  52                           buf+22+asn1len, request_len-(22+asn1len))<0) {
  53     log_fn(LOG_WARN, "Incorrect signature on ESTABLISH_INTRO cell; rejecting");
  54     goto err;
  55   }
  56
  57   /* The request is valid.  First, compute the hash of Bob's PK.*/
  58   if (crypto_pk_get_digest(pk, pk_digest)<0) {
  59     log_fn(LOG_WARN, "Couldn't hash public key.");
  60     goto err;
  61   }
  62
  63   /* Close any other intro circuits with the same pk. */
  64   c = NULL;
  65   while ((c = circuit_get_next_by_service_and_purpose(
  66                                 c,pk_digest,CIRCUIT_PURPOSE_INTRO_POINT))) {
  67     circuit_mark_for_close(c);
  68   }
  69
  70   /* Now, set up this circuit. */
  71   circ->purpose = CIRCUIT_PURPOSE_INTRO_POINT;
  72   memcpy(circ->rend_service, pk_digest, 20);
  73
  74   return 0;
  75  truncated:
  76   log_fn(LOG_WARN, "Rejecting truncated ESTABLISH_INTRO cell");
  77  err:
  78   if (pk) crypto_free_pk_env(pk);
  79   circuit_mark_for_close(circ);
  80   return -1;
  81 }
  82
  83 /* Process an INTRODUCE1 cell by finding the corresponding introduction
  84  * circuit, and relaying the body of the INTRODUCE1 cell inside an
  85  * INTRODUCE2 cell.
  86  */
  87 int
  88 rend_mid_introduce(circuit_t *circ, char *request, int request_len)
  89 {
  90   circuit_t *intro_circ;
  91
  92   if (request_len < 276) {
  93     log_fn(LOG_WARN, "Impossibly short INTRODUCE2 cell; dropping.");
  94     goto err;
  95   }
  96
  97   /* The first 20 bytes are all we look at: they have a hash of Bob's PK. */
  98   intro_circ = circuit_get_next_by_service_and_purpose(
  99                              NULL, request, CIRCUIT_PURPOSE_INTRO_POINT);
 100   if (!intro_circ) {
 101     log_fn(LOG_WARN,
 102            "No introduction circuit matching INTRODUCE2 cell; dropping");
 103     goto err;
 104   }
 105
 106   /* Great.  Now we just relay the cell down the circuit. */
 107   if (connection_edge_send_command(NULL, intro_circ,
 108                                    RELAY_COMMAND_INTRODUCE2,
 109                                    request, request_len, NULL)) {
 110     log_fn(LOG_WARN, "Unable to send INTRODUCE2 cell to OP.");
 111     goto err;
 112   }
 113
 114   return 0;
 115  err:
 116   circuit_mark_for_close(circ); /* Is this right? */
 117   return -1;
 118 }
 119
 120 /* Process an ESTABLISH_RENDEZVOUS cell by settingthe circuit's purpose and
 121  * rendezvous cookie.
 122  */
 123 int
 124 rend_mid_establish_rendezvous(circuit_t *circ, char *request, int request_len)
 125 {
 126   if (circ->purpose != CIRCUIT_PURPOSE_INTERMEDIATE) {
 127     log_fn(LOG_WARN, "Tried to establish rendezvous on non-intermediate circuit");
 128     goto err;
 129   }
 130
 131   if (request_len != REND_COOKIE_LEN) {
 132     log_fn(LOG_WARN, "Invalid length on ESTABLISH_RENDEZVOUS");
 133     goto err;
 134   }
 135
 136   if (circuit_get_rendezvous(request)) {
 137     log_fn(LOG_WARN, "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS");
 138     goto err;
 139   }
 140
 141   circ->purpose = CIRCUIT_PURPOSE_REND_POINT_WAITING;
 142   memcpy(circ->rend_cookie, request, REND_COOKIE_LEN);
 143
 144   return 0;
 145  err:
 146   circuit_mark_for_close(circ);
 147   return -1;
 148 }
 149
 150 /* Process a RENDEZVOUS1 cell by looking up the correct rendezvous circuit by its
 151  * relaying the cell's body in a RENDEZVOUS2 cell, and connecting the two circuits.
 152  */
 153 int
 154 rend_mid_rendezvous(circuit_t *circ, char *request, int request_len)
 155 {
 156   circuit_t *rend_circ;
 157
 158   if (circ->purpose != CIRCUIT_PURPOSE_INTERMEDIATE) {
 159     log_fn(LOG_WARN, "Tried to complete rendezvous on non-intermediate circuit");
 160     goto err;
 161   }
 162
 163   if (request_len < 20+128+20) {
 164     log_fn(LOG_WARN, "Rejecting impossibly short RENDEZVOUS1 cell");
 165     goto err;
 166   }
 167
 168   rend_circ = circuit_get_rendezvous(request);
 169   if (!rend_circ) {
 170     log_fn(LOG_WARN, "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie");
 171     goto err;
 172   }
 173
 174   /* Send the RENDEZVOUS2 cell to Alice. */
 175   if (connection_edge_send_command(NULL, rend_circ,
 176                                    RELAY_COMMAND_RENDEZVOUS2,
 177                                    request+20, request_len-20, NULL)) {
 178     log_fn(LOG_WARN, "Unable to send RENDEZVOUS2 cell to OP.");
 179     goto err;
 180   }
 181
 182   /* Join the circuits. */
 183   circ->purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
 184   rend_circ->purpose = CIRCUIT_PURPOSE_REND_ESTABLISHED;
 185   memset(circ->rend_cookie, 0, 20);
 186
 187   rend_circ->rend_splice = circ;
 188   circ->rend_splice = rend_circ;
 189
 190   return 0;
 191  err:
 192   circuit_mark_for_close(circ);
 193   return -1;
 194 }
 195
 196 /*
 197   Local Variables:
 198   mode:c
 199   indent-tabs-mode:nil
 200   c-basic-offset:2
 201   End:
 202 */