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tor/src/or/rendmid.c

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/* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2015, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file rendmid.c
* \brief Implement introductions points and rendezvous points.
**/
#include "or.h"
#include "circuitlist.h"
#include "circuituse.h"
#include "config.h"
#include "relay.h"
#include "rendmid.h"
#include "rephist.h"
/** Respond to an ESTABLISH_INTRO cell by checking the signed data and
* setting the circuit's purpose and service pk digest.
*/
int
rend_mid_establish_intro(or_circuit_t *circ, const uint8_t *request,
size_t request_len)
{
crypto_pk_t *pk = NULL;
char buf[DIGEST_LEN+9];
char expected_digest[DIGEST_LEN];
char pk_digest[DIGEST_LEN];
size_t asn1len;
or_circuit_t *c;
char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
int reason = END_CIRC_REASON_INTERNAL;
log_info(LD_REND,
"Received an ESTABLISH_INTRO request on circuit %u",
(unsigned) circ->p_circ_id);
if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {
log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
"Rejecting ESTABLISH_INTRO on non-OR or non-edge circuit.");
reason = END_CIRC_REASON_TORPROTOCOL;
goto err;
}
if (request_len < 2+DIGEST_LEN)
goto truncated;
/* First 2 bytes: length of asn1-encoded key. */
asn1len = ntohs(get_uint16(request));
/* Next asn1len bytes: asn1-encoded key. */
if (request_len < 2+DIGEST_LEN+asn1len)
goto truncated;
pk = crypto_pk_asn1_decode((char*)(request+2), asn1len);
if (!pk) {
reason = END_CIRC_REASON_TORPROTOCOL;
log_warn(LD_PROTOCOL, "Couldn't decode public key.");
goto err;
}
/* Next 20 bytes: Hash of rend_circ_nonce | "INTRODUCE" */
memcpy(buf, circ->rend_circ_nonce, DIGEST_LEN);
memcpy(buf+DIGEST_LEN, "INTRODUCE", 9);
if (crypto_digest(expected_digest, buf, DIGEST_LEN+9) < 0) {
log_warn(LD_BUG, "Internal error computing digest.");
goto err;
}
if (tor_memneq(expected_digest, request+2+asn1len, DIGEST_LEN)) {
log_warn(LD_PROTOCOL, "Hash of session info was not as expected.");
reason = END_CIRC_REASON_TORPROTOCOL;
goto err;
}
/* Rest of body: signature of previous data */
note_crypto_pk_op(REND_MID);
if (crypto_pk_public_checksig_digest(pk,
(char*)request, 2+asn1len+DIGEST_LEN,
(char*)(request+2+DIGEST_LEN+asn1len),
request_len-(2+DIGEST_LEN+asn1len))<0) {
log_warn(LD_PROTOCOL,
"Incorrect signature on ESTABLISH_INTRO cell; rejecting.");
reason = END_CIRC_REASON_TORPROTOCOL;
goto err;
}
/* The request is valid. First, compute the hash of Bob's PK.*/
if (crypto_pk_get_digest(pk, pk_digest)<0) {
log_warn(LD_BUG, "Internal error: couldn't hash public key.");
goto err;
}
crypto_pk_free(pk); /* don't need it anymore */
pk = NULL; /* so we don't free it again if err */
base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
pk_digest, REND_SERVICE_ID_LEN);
/* Close any other intro circuits with the same pk. */
c = NULL;
while ((c = circuit_get_intro_point((const uint8_t *)pk_digest))) {
log_info(LD_REND, "Replacing old circuit for service %s",
safe_str(serviceid));
circuit_mark_for_close(TO_CIRCUIT(c), END_CIRC_REASON_FINISHED);
/* Now it's marked, and it won't be returned next time. */
}
/* Acknowledge the request. */
if (relay_send_command_from_edge(0, TO_CIRCUIT(circ),
RELAY_COMMAND_INTRO_ESTABLISHED,
"", 0, NULL)<0) {
log_info(LD_GENERAL, "Couldn't send INTRO_ESTABLISHED cell.");
goto err;
}
/* Now, set up this circuit. */
circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_INTRO_POINT);
circuit_set_intro_point_digest(circ, (uint8_t *)pk_digest);
log_info(LD_REND,
"Established introduction point on circuit %u for service %s",
(unsigned) circ->p_circ_id, safe_str(serviceid));
return 0;
truncated:
log_warn(LD_PROTOCOL, "Rejecting truncated ESTABLISH_INTRO cell.");
reason = END_CIRC_REASON_TORPROTOCOL;
err:
if (pk) crypto_pk_free(pk);
circuit_mark_for_close(TO_CIRCUIT(circ), reason);
return -1;
}
/** Process an INTRODUCE1 cell by finding the corresponding introduction
* circuit, and relaying the body of the INTRODUCE1 cell inside an
* INTRODUCE2 cell.
*/
int
rend_mid_introduce(or_circuit_t *circ, const uint8_t *request,
size_t request_len)
{
or_circuit_t *intro_circ;
char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
char nak_body[1];
log_info(LD_REND, "Received an INTRODUCE1 request on circuit %u",
(unsigned)circ->p_circ_id);
if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {
log_warn(LD_PROTOCOL,
"Rejecting INTRODUCE1 on non-OR or non-edge circuit %u.",
(unsigned)circ->p_circ_id);
goto err;
}
/* We have already done an introduction on this circuit but we just
received a request for another one. We block it since this might
be an attempt to DoS a hidden service (#15515). */
if (circ->already_received_introduce1) {
log_fn(LOG_PROTOCOL_WARN, LD_REND,
"Blocking multiple introductions on the same circuit. "
"Someone might be trying to attack a hidden service through "
"this relay.");
circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_TORPROTOCOL);
return -1;
}
circ->already_received_introduce1 = 1;
/* We could change this to MAX_HEX_NICKNAME_LEN now that 0.0.9.x is
* obsolete; however, there isn't much reason to do so, and we're going
* to revise this protocol anyway.
*/
if (request_len < (DIGEST_LEN+(MAX_NICKNAME_LEN+1)+REND_COOKIE_LEN+
DH_KEY_LEN+CIPHER_KEY_LEN+PKCS1_OAEP_PADDING_OVERHEAD)) {
log_warn(LD_PROTOCOL, "Impossibly short INTRODUCE1 cell on circuit %u; "
"responding with nack.",
(unsigned)circ->p_circ_id);
goto err;
}
base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
(char*)request, REND_SERVICE_ID_LEN);
/* The first 20 bytes are all we look at: they have a hash of Bob's PK. */
intro_circ = circuit_get_intro_point((const uint8_t*)request);
if (!intro_circ) {
log_info(LD_REND,
"No intro circ found for INTRODUCE1 cell (%s) from circuit %u; "
"responding with nack.",
safe_str(serviceid), (unsigned)circ->p_circ_id);
goto err;
}
log_info(LD_REND,
"Sending introduction request for service %s "
"from circ %u to circ %u",
safe_str(serviceid), (unsigned)circ->p_circ_id,
(unsigned)intro_circ->p_circ_id);
/* Great. Now we just relay the cell down the circuit. */
if (relay_send_command_from_edge(0, TO_CIRCUIT(intro_circ),
RELAY_COMMAND_INTRODUCE2,
(char*)request, request_len, NULL)) {
log_warn(LD_GENERAL,
"Unable to send INTRODUCE2 cell to Tor client.");
goto err;
}
/* And send an ack down Alice's circuit. Empty body means succeeded. */
if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
RELAY_COMMAND_INTRODUCE_ACK,
NULL,0,NULL)) {
log_warn(LD_GENERAL, "Unable to send INTRODUCE_ACK cell to Tor client.");
circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
return -1;
}
return 0;
err:
/* Send the client a NACK */
nak_body[0] = 1;
if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
RELAY_COMMAND_INTRODUCE_ACK,
nak_body, 1, NULL)) {
log_warn(LD_GENERAL, "Unable to send NAK to Tor client.");
/* Is this right? */
circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
}
return -1;
}
/** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and
* rendezvous cookie.
*/
int
rend_mid_establish_rendezvous(or_circuit_t *circ, const uint8_t *request,
size_t request_len)
{
char hexid[9];
int reason = END_CIRC_REASON_TORPROTOCOL;
log_info(LD_REND, "Received an ESTABLISH_RENDEZVOUS request on circuit %u",
(unsigned)circ->p_circ_id);
if (circ->base_.purpose != CIRCUIT_PURPOSE_OR) {
log_warn(LD_PROTOCOL,
"Tried to establish rendezvous on non-OR circuit with purpose %s",
circuit_purpose_to_string(circ->base_.purpose));
goto err;
}
if (circ->base_.n_chan) {
log_warn(LD_PROTOCOL,
"Tried to establish rendezvous on non-edge circuit");
goto err;
}
if (request_len != REND_COOKIE_LEN) {
log_fn(LOG_PROTOCOL_WARN,
LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS.");
goto err;
}
if (circuit_get_rendezvous(request)) {
log_warn(LD_PROTOCOL,
"Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS.");
goto err;
}
/* Acknowledge the request. */
if (relay_send_command_from_edge(0,TO_CIRCUIT(circ),
RELAY_COMMAND_RENDEZVOUS_ESTABLISHED,
"", 0, NULL)<0) {
log_warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell.");
reason = END_CIRC_REASON_INTERNAL;
goto err;
}
circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_POINT_WAITING);
circuit_set_rendezvous_cookie(circ, request);
base16_encode(hexid,9,(char*)request,4);
log_info(LD_REND,
"Established rendezvous point on circuit %u for cookie %s",
(unsigned)circ->p_circ_id, hexid);
return 0;
err:
circuit_mark_for_close(TO_CIRCUIT(circ), reason);
return -1;
}
/** Process a RENDEZVOUS1 cell by looking up the correct rendezvous
* circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and
* connecting the two circuits.
*/
int
rend_mid_rendezvous(or_circuit_t *circ, const uint8_t *request,
size_t request_len)
{
const or_options_t *options = get_options();
or_circuit_t *rend_circ;
char hexid[9];
int reason = END_CIRC_REASON_INTERNAL;
if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) {
log_info(LD_REND,
"Tried to complete rendezvous on non-OR or non-edge circuit %u.",
(unsigned)circ->p_circ_id);
reason = END_CIRC_REASON_TORPROTOCOL;
goto err;
}
if (request_len != REND_COOKIE_LEN+DH_KEY_LEN+DIGEST_LEN) {
log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
"Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %u.",
(int)request_len, (unsigned)circ->p_circ_id);
reason = END_CIRC_REASON_TORPROTOCOL;
goto err;
}
base16_encode(hexid, sizeof(hexid), (const char*)request, 4);
log_info(LD_REND,
"Got request for rendezvous from circuit %u to cookie %s.",
(unsigned)circ->p_circ_id, hexid);
rend_circ = circuit_get_rendezvous(request);
if (!rend_circ) {
log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
"Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.",
hexid);
reason = END_CIRC_REASON_TORPROTOCOL;
goto err;
}
/* Statistics: Mark this circuit as an RP circuit so that we collect
stats from it. */
if (options->HiddenServiceStatistics) {
circ->circuit_carries_hs_traffic_stats = 1;
}
/* Send the RENDEZVOUS2 cell to Alice. */
if (relay_send_command_from_edge(0, TO_CIRCUIT(rend_circ),
RELAY_COMMAND_RENDEZVOUS2,
(char*)(request+REND_COOKIE_LEN),
request_len-REND_COOKIE_LEN, NULL)) {
log_warn(LD_GENERAL,
"Unable to send RENDEZVOUS2 cell to client on circuit %u.",
(unsigned)rend_circ->p_circ_id);
goto err;
}
/* Join the circuits. */
log_info(LD_REND,
"Completing rendezvous: circuit %u joins circuit %u (cookie %s)",
(unsigned)circ->p_circ_id, (unsigned)rend_circ->p_circ_id, hexid);
circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_ESTABLISHED);
circuit_change_purpose(TO_CIRCUIT(rend_circ),
CIRCUIT_PURPOSE_REND_ESTABLISHED);
circuit_set_rendezvous_cookie(circ, NULL);
rend_circ->rend_splice = circ;
circ->rend_splice = rend_circ;
return 0;
err:
circuit_mark_for_close(TO_CIRCUIT(circ), reason);
return -1;
}
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