rendmid.c 12 KB

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  1. /* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
  2. * Copyright (c) 2007-2015, The Tor Project, Inc. */
  3. /* See LICENSE for licensing information */
  4. /**
  5. * \file rendmid.c
  6. * \brief Implement introductions points and rendezvous points.
  7. **/
  8. #include "or.h"
  9. #include "circuitlist.h"
  10. #include "circuituse.h"
  11. #include "config.h"
  12. #include "relay.h"
  13. #include "rendmid.h"
  14. #include "rephist.h"
  15. /** Respond to an ESTABLISH_INTRO cell by checking the signed data and
  16. * setting the circuit's purpose and service pk digest.
  17. */
  18. int
  19. rend_mid_establish_intro(or_circuit_t *circ, const uint8_t *request,
  20. size_t request_len)
  21. {
  22. crypto_pk_t *pk = NULL;
  23. char buf[DIGEST_LEN+9];
  24. char expected_digest[DIGEST_LEN];
  25. char pk_digest[DIGEST_LEN];
  26. size_t asn1len;
  27. or_circuit_t *c;
  28. char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
  29. int reason = END_CIRC_REASON_INTERNAL;
  30. log_info(LD_REND,
  31. "Received an ESTABLISH_INTRO request on circuit %u",
  32. (unsigned) circ->p_circ_id);
  33. if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {
  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. /* Next asn1len bytes: asn1-encoded key. */
  44. if (request_len < 2+DIGEST_LEN+asn1len)
  45. goto truncated;
  46. pk = crypto_pk_asn1_decode((char*)(request+2), asn1len);
  47. if (!pk) {
  48. reason = END_CIRC_REASON_TORPROTOCOL;
  49. log_warn(LD_PROTOCOL, "Couldn't decode public key.");
  50. goto err;
  51. }
  52. /* Next 20 bytes: Hash of rend_circ_nonce | "INTRODUCE" */
  53. memcpy(buf, circ->rend_circ_nonce, DIGEST_LEN);
  54. memcpy(buf+DIGEST_LEN, "INTRODUCE", 9);
  55. if (crypto_digest(expected_digest, buf, DIGEST_LEN+9) < 0) {
  56. log_warn(LD_BUG, "Internal error computing digest.");
  57. goto err;
  58. }
  59. if (tor_memneq(expected_digest, request+2+asn1len, DIGEST_LEN)) {
  60. log_warn(LD_PROTOCOL, "Hash of session info was not as expected.");
  61. reason = END_CIRC_REASON_TORPROTOCOL;
  62. goto err;
  63. }
  64. /* Rest of body: signature of previous data */
  65. note_crypto_pk_op(REND_MID);
  66. if (crypto_pk_public_checksig_digest(pk,
  67. (char*)request, 2+asn1len+DIGEST_LEN,
  68. (char*)(request+2+DIGEST_LEN+asn1len),
  69. request_len-(2+DIGEST_LEN+asn1len))<0) {
  70. log_warn(LD_PROTOCOL,
  71. "Incorrect signature on ESTABLISH_INTRO cell; rejecting.");
  72. reason = END_CIRC_REASON_TORPROTOCOL;
  73. goto err;
  74. }
  75. /* The request is valid. First, compute the hash of Bob's PK.*/
  76. if (crypto_pk_get_digest(pk, pk_digest)<0) {
  77. log_warn(LD_BUG, "Internal error: couldn't hash public key.");
  78. goto err;
  79. }
  80. crypto_pk_free(pk); /* don't need it anymore */
  81. pk = NULL; /* so we don't free it again if err */
  82. base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
  83. pk_digest, REND_SERVICE_ID_LEN);
  84. /* Close any other intro circuits with the same pk. */
  85. c = NULL;
  86. while ((c = circuit_get_intro_point((const uint8_t *)pk_digest))) {
  87. log_info(LD_REND, "Replacing old circuit for service %s",
  88. safe_str(serviceid));
  89. circuit_mark_for_close(TO_CIRCUIT(c), END_CIRC_REASON_FINISHED);
  90. /* Now it's marked, and it won't be returned next time. */
  91. }
  92. /* Acknowledge the request. */
  93. if (relay_send_command_from_edge(0, TO_CIRCUIT(circ),
  94. RELAY_COMMAND_INTRO_ESTABLISHED,
  95. "", 0, NULL)<0) {
  96. log_info(LD_GENERAL, "Couldn't send INTRO_ESTABLISHED cell.");
  97. goto err;
  98. }
  99. /* Now, set up this circuit. */
  100. circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_INTRO_POINT);
  101. circuit_set_intro_point_digest(circ, (uint8_t *)pk_digest);
  102. log_info(LD_REND,
  103. "Established introduction point on circuit %u for service %s",
  104. (unsigned) circ->p_circ_id, safe_str(serviceid));
  105. return 0;
  106. truncated:
  107. log_warn(LD_PROTOCOL, "Rejecting truncated ESTABLISH_INTRO cell.");
  108. reason = END_CIRC_REASON_TORPROTOCOL;
  109. err:
  110. if (pk) crypto_pk_free(pk);
  111. circuit_mark_for_close(TO_CIRCUIT(circ), reason);
  112. return -1;
  113. }
  114. /** Process an INTRODUCE1 cell by finding the corresponding introduction
  115. * circuit, and relaying the body of the INTRODUCE1 cell inside an
  116. * INTRODUCE2 cell.
  117. */
  118. int
  119. rend_mid_introduce(or_circuit_t *circ, const uint8_t *request,
  120. size_t request_len)
  121. {
  122. or_circuit_t *intro_circ;
  123. char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
  124. char nak_body[1];
  125. log_info(LD_REND, "Received an INTRODUCE1 request on circuit %u",
  126. (unsigned)circ->p_circ_id);
  127. if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {
  128. log_warn(LD_PROTOCOL,
  129. "Rejecting INTRODUCE1 on non-OR or non-edge circuit %u.",
  130. (unsigned)circ->p_circ_id);
  131. goto err;
  132. }
  133. /* We have already done an introduction on this circuit but we just
  134. received a request for another one. We block it since this might
  135. be an attempt to DoS a hidden service (#15515). */
  136. if (circ->already_received_introduce1) {
  137. log_fn(LOG_PROTOCOL_WARN, LD_REND,
  138. "Blocking multiple introductions on the same circuit. "
  139. "Someone might be trying to attack a hidden service through "
  140. "this relay.");
  141. circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_TORPROTOCOL);
  142. return -1;
  143. }
  144. circ->already_received_introduce1 = 1;
  145. /* We could change this to MAX_HEX_NICKNAME_LEN now that 0.0.9.x is
  146. * obsolete; however, there isn't much reason to do so, and we're going
  147. * to revise this protocol anyway.
  148. */
  149. if (request_len < (DIGEST_LEN+(MAX_NICKNAME_LEN+1)+REND_COOKIE_LEN+
  150. DH_KEY_LEN+CIPHER_KEY_LEN+PKCS1_OAEP_PADDING_OVERHEAD)) {
  151. log_warn(LD_PROTOCOL, "Impossibly short INTRODUCE1 cell on circuit %u; "
  152. "responding with nack.",
  153. (unsigned)circ->p_circ_id);
  154. goto err;
  155. }
  156. base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
  157. (char*)request, REND_SERVICE_ID_LEN);
  158. /* The first 20 bytes are all we look at: they have a hash of Bob's PK. */
  159. intro_circ = circuit_get_intro_point((const uint8_t*)request);
  160. if (!intro_circ) {
  161. log_info(LD_REND,
  162. "No intro circ found for INTRODUCE1 cell (%s) from circuit %u; "
  163. "responding with nack.",
  164. safe_str(serviceid), (unsigned)circ->p_circ_id);
  165. goto err;
  166. }
  167. log_info(LD_REND,
  168. "Sending introduction request for service %s "
  169. "from circ %u to circ %u",
  170. safe_str(serviceid), (unsigned)circ->p_circ_id,
  171. (unsigned)intro_circ->p_circ_id);
  172. /* Great. Now we just relay the cell down the circuit. */
  173. if (relay_send_command_from_edge(0, TO_CIRCUIT(intro_circ),
  174. RELAY_COMMAND_INTRODUCE2,
  175. (char*)request, request_len, NULL)) {
  176. log_warn(LD_GENERAL,
  177. "Unable to send INTRODUCE2 cell to Tor client.");
  178. goto err;
  179. }
  180. /* And send an ack down Alice's circuit. Empty body means succeeded. */
  181. if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
  182. RELAY_COMMAND_INTRODUCE_ACK,
  183. NULL,0,NULL)) {
  184. log_warn(LD_GENERAL, "Unable to send INTRODUCE_ACK cell to Tor client.");
  185. circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
  186. return -1;
  187. }
  188. return 0;
  189. err:
  190. /* Send the client a NACK */
  191. nak_body[0] = 1;
  192. if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
  193. RELAY_COMMAND_INTRODUCE_ACK,
  194. nak_body, 1, NULL)) {
  195. log_warn(LD_GENERAL, "Unable to send NAK to Tor client.");
  196. /* Is this right? */
  197. circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
  198. }
  199. return -1;
  200. }
  201. /** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and
  202. * rendezvous cookie.
  203. */
  204. int
  205. rend_mid_establish_rendezvous(or_circuit_t *circ, const uint8_t *request,
  206. size_t request_len)
  207. {
  208. char hexid[9];
  209. int reason = END_CIRC_REASON_TORPROTOCOL;
  210. log_info(LD_REND, "Received an ESTABLISH_RENDEZVOUS request on circuit %u",
  211. (unsigned)circ->p_circ_id);
  212. if (circ->base_.purpose != CIRCUIT_PURPOSE_OR) {
  213. log_warn(LD_PROTOCOL,
  214. "Tried to establish rendezvous on non-OR circuit with purpose %s",
  215. circuit_purpose_to_string(circ->base_.purpose));
  216. goto err;
  217. }
  218. if (circ->base_.n_chan) {
  219. log_warn(LD_PROTOCOL,
  220. "Tried to establish rendezvous on non-edge circuit");
  221. goto err;
  222. }
  223. if (request_len != REND_COOKIE_LEN) {
  224. log_fn(LOG_PROTOCOL_WARN,
  225. LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS.");
  226. goto err;
  227. }
  228. if (circuit_get_rendezvous(request)) {
  229. log_warn(LD_PROTOCOL,
  230. "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS.");
  231. goto err;
  232. }
  233. /* Acknowledge the request. */
  234. if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
  235. RELAY_COMMAND_RENDEZVOUS_ESTABLISHED,
  236. "", 0, NULL)<0) {
  237. log_warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell.");
  238. reason = END_CIRC_REASON_INTERNAL;
  239. goto err;
  240. }
  241. circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_POINT_WAITING);
  242. circuit_set_rendezvous_cookie(circ, request);
  243. base16_encode(hexid,9,(char*)request,4);
  244. log_info(LD_REND,
  245. "Established rendezvous point on circuit %u for cookie %s",
  246. (unsigned)circ->p_circ_id, hexid);
  247. return 0;
  248. err:
  249. circuit_mark_for_close(TO_CIRCUIT(circ), reason);
  250. return -1;
  251. }
  252. /** Process a RENDEZVOUS1 cell by looking up the correct rendezvous
  253. * circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and
  254. * connecting the two circuits.
  255. */
  256. int
  257. rend_mid_rendezvous(or_circuit_t *circ, const uint8_t *request,
  258. size_t request_len)
  259. {
  260. const or_options_t *options = get_options();
  261. or_circuit_t *rend_circ;
  262. char hexid[9];
  263. int reason = END_CIRC_REASON_INTERNAL;
  264. if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {
  265. log_info(LD_REND,
  266. "Tried to complete rendezvous on non-OR or non-edge circuit %u.",
  267. (unsigned)circ->p_circ_id);
  268. reason = END_CIRC_REASON_TORPROTOCOL;
  269. goto err;
  270. }
  271. if (request_len != REND_COOKIE_LEN+DH_KEY_LEN+DIGEST_LEN) {
  272. log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
  273. "Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %u.",
  274. (int)request_len, (unsigned)circ->p_circ_id);
  275. reason = END_CIRC_REASON_TORPROTOCOL;
  276. goto err;
  277. }
  278. base16_encode(hexid, sizeof(hexid), (const char*)request, 4);
  279. log_info(LD_REND,
  280. "Got request for rendezvous from circuit %u to cookie %s.",
  281. (unsigned)circ->p_circ_id, hexid);
  282. rend_circ = circuit_get_rendezvous(request);
  283. if (!rend_circ) {
  284. log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
  285. "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.",
  286. hexid);
  287. reason = END_CIRC_REASON_TORPROTOCOL;
  288. goto err;
  289. }
  290. /* Statistics: Mark this circuit as an RP circuit so that we collect
  291. stats from it. */
  292. if (options->HiddenServiceStatistics) {
  293. circ->circuit_carries_hs_traffic_stats = 1;
  294. }
  295. /* Send the RENDEZVOUS2 cell to Alice. */
  296. if (relay_send_command_from_edge(0, TO_CIRCUIT(rend_circ),
  297. RELAY_COMMAND_RENDEZVOUS2,
  298. (char*)(request+REND_COOKIE_LEN),
  299. request_len-REND_COOKIE_LEN, NULL)) {
  300. log_warn(LD_GENERAL,
  301. "Unable to send RENDEZVOUS2 cell to client on circuit %u.",
  302. (unsigned)rend_circ->p_circ_id);
  303. goto err;
  304. }
  305. /* Join the circuits. */
  306. log_info(LD_REND,
  307. "Completing rendezvous: circuit %u joins circuit %u (cookie %s)",
  308. (unsigned)circ->p_circ_id, (unsigned)rend_circ->p_circ_id, hexid);
  309. circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_ESTABLISHED);
  310. circuit_change_purpose(TO_CIRCUIT(rend_circ),
  311. CIRCUIT_PURPOSE_REND_ESTABLISHED);
  312. circuit_set_rendezvous_cookie(circ, NULL);
  313. rend_circ->rend_splice = circ;
  314. circ->rend_splice = rend_circ;
  315. return 0;
  316. err:
  317. circuit_mark_for_close(TO_CIRCUIT(circ), reason);
  318. return -1;
  319. }