directory.c

关于tor匿名通信的源代码

  log_debug(LD_DIR, "anonymized %d, use_begindir %d.",
            anonymized_connection, use_begindir);

  log_debug(LD_DIR, "Initiating %s", dir_conn_purpose_to_string(dir_purpose));

  conn = TO_DIR_CONN(connection_new(CONN_TYPE_DIR, AF_INET));

  /* set up conn so it's got all the data we need to remember */
  conn->_base.addr = addr;
  conn->_base.port = use_begindir ? or_port : dir_port;
  conn->_base.address = tor_strdup(address);
  memcpy(conn->identity_digest, digest, DIGEST_LEN);

  conn->_base.purpose = dir_purpose;
  conn->router_purpose = router_purpose;

  /* give it an initial state */
  conn->_base.state = DIR_CONN_STATE_CONNECTING;

  /* decide whether we can learn our IP address from this conn */
  conn->dirconn_direct = !anonymized_connection;

  if (!anonymized_connection && !use_begindir) {
    /* then we want to connect to dirport directly */

    if (options->HttpProxy) {
      addr = options->HttpProxyAddr;
      dir_port = options->HttpProxyPort;
    }

    switch (connection_connect(TO_CONN(conn), conn->_base.address, addr,
                               dir_port)) {
      case -1:
        connection_dir_request_failed(conn); /* retry if we want */
        /* XXX we only pass 'conn' above, not 'resource', 'payload',
         * etc. So in many situations it can't retry! -RD */
        connection_free(TO_CONN(conn));
        return;
      case 1:
        /* start flushing conn */
        conn->_base.state = DIR_CONN_STATE_CLIENT_SENDING;
        /* fall through */
      case 0:
        /* queue the command on the outbuf */
        directory_send_command(conn, dir_purpose, 1, resource,
                               payload, payload_len,
                               supports_conditional_consensus,
                               if_modified_since);
        connection_watch_events(TO_CONN(conn), EV_READ | EV_WRITE);
        /* writable indicates finish, readable indicates broken link,
           error indicates broken link in windowsland. */
    }
  } else { /* we want to connect via a tor connection */
    edge_connection_t *linked_conn;

    /* If it's an anonymized connection, remember the fact that we
     * wanted it for later: maybe we'll want it again soon. */
    if (anonymized_connection && use_begindir)
      rep_hist_note_used_internal(time(NULL), 0, 1);
    else if (anonymized_connection && !use_begindir)
      rep_hist_note_used_port(time(NULL), conn->_base.port);

    /* make an AP connection
     * populate it and add it at the right state
     * hook up both sides
     */
    linked_conn =
      connection_ap_make_link(conn->_base.address, conn->_base.port,
                              digest, use_begindir, conn->dirconn_direct);
    if (!linked_conn) {
      log_warn(LD_NET,"Making tunnel to dirserver failed.");
      connection_mark_for_close(TO_CONN(conn));
      return;
    }
    connection_link_connections(TO_CONN(conn), TO_CONN(linked_conn));

    if (connection_add(TO_CONN(conn)) < 0) {
      log_warn(LD_NET,"Unable to add connection for link to dirserver.");
      connection_mark_for_close(TO_CONN(conn));
      return;
    }
    conn->_base.state = DIR_CONN_STATE_CLIENT_SENDING;
    /* queue the command on the outbuf */
    directory_send_command(conn, dir_purpose, 0, resource,
                           payload, payload_len,
                           supports_conditional_consensus,
                           if_modified_since);
    connection_watch_events(TO_CONN(conn), EV_READ | EV_WRITE);
    connection_start_reading(TO_CONN(linked_conn));
  }
}

/** Return true iff anything we say on <b>conn</b> is being encrypted before
 * we send it to the client/server. */
int
connection_dir_is_encrypted(dir_connection_t *conn)
{
  /* Right now it's sufficient to see if conn is or has been linked, since
   * the only thing it could be linked to is an edge connection on a
   * circuit, and the only way it could have been unlinked is at the edge
   * connection getting closed.
   */
  return TO_CONN(conn)->linked;
}

/** Helper for sorting
 *
 * sort strings alphabetically
 */
static int
_compare_strs(const void **a, const void **b)
{
  const char *s1 = *a, *s2 = *b;
  return strcmp(s1, s2);
}

/** Return the URL we should use for a consensus download.
 *
 * This url depends on whether or not the server we go to
 * is sufficiently new to support conditional consensus downloading,
 * i.e. GET .../consensus/<b>fpr</b>+<b>fpr</b>+<b>fpr</b>
 */
#define CONDITIONAL_CONSENSUS_FPR_LEN 3
#if (CONDITIONAL_CONSENSUS_FPR_LEN > DIGEST_LEN)
#error "conditional consensus fingerprint length is larger than digest length"
#endif
static char *
directory_get_consensus_url(int supports_conditional_consensus)
{
  char *url;
  int len;

  if (supports_conditional_consensus) {
    char *authority_id_list;
    smartlist_t *authority_digets = smartlist_create();

    SMARTLIST_FOREACH(router_get_trusted_dir_servers(),
                      trusted_dir_server_t *, ds,
      {
        char *hex;
        if (!(ds->type & V3_AUTHORITY))
          continue;

        hex = tor_malloc(2*CONDITIONAL_CONSENSUS_FPR_LEN+1);
        base16_encode(hex, 2*CONDITIONAL_CONSENSUS_FPR_LEN+1,
                      ds->v3_identity_digest, CONDITIONAL_CONSENSUS_FPR_LEN);
        smartlist_add(authority_digets, hex);
      });
    smartlist_sort(authority_digets, _compare_strs);
    authority_id_list = smartlist_join_strings(authority_digets,
                                               "+", 0, NULL);

    len = strlen(authority_id_list)+64;
    url = tor_malloc(len);
    tor_snprintf(url, len, "/tor/status-vote/current/consensus/%s.z",
                 authority_id_list);

    SMARTLIST_FOREACH(authority_digets, char *, cp, tor_free(cp));
    smartlist_free(authority_digets);
    tor_free(authority_id_list);
  } else {
    url = tor_strdup("/tor/status-vote/current/consensus.z");
  }
  return url;
}

/** Queue an appropriate HTTP command on conn-\>outbuf.  The other args
 * are as in directory_initiate_command.
 */
static void
directory_send_command(dir_connection_t *conn,
                       int purpose, int direct, const char *resource,
                       const char *payload, size_t payload_len,
                       int supports_conditional_consensus,
                       time_t if_modified_since)
{
  char proxystring[256];
  char proxyauthstring[256];
  char hoststring[128];
  char imsstring[RFC1123_TIME_LEN+32];
  char *url;
  char request[8192];
  const char *httpcommand = NULL;
  size_t len;

  tor_assert(conn);
  tor_assert(conn->_base.type == CONN_TYPE_DIR);

  tor_free(conn->requested_resource);
  if (resource)
    conn->requested_resource = tor_strdup(resource);

  /* come up with a string for which Host: we want */
  if (conn->_base.port == 80) {
    strlcpy(hoststring, conn->_base.address, sizeof(hoststring));
  } else {
    tor_snprintf(hoststring, sizeof(hoststring),"%s:%d",
                 conn->_base.address, conn->_base.port);
  }

  /* Format if-modified-since */
  if (!if_modified_since) {
    imsstring[0] = '\0';
  } else {
    char b[RFC1123_TIME_LEN+1];
    format_rfc1123_time(b, if_modified_since);
    tor_snprintf(imsstring, sizeof(imsstring), "\r\nIf-Modified-Since: %s", b);
  }

  /* come up with some proxy lines, if we're using one. */
  if (direct && get_options()->HttpProxy) {
    char *base64_authenticator=NULL;
    const char *authenticator = get_options()->HttpProxyAuthenticator;

    tor_snprintf(proxystring, sizeof(proxystring),"http://%s", hoststring);
    if (authenticator) {
      base64_authenticator = alloc_http_authenticator(authenticator);
      if (!base64_authenticator)
        log_warn(LD_BUG, "Encoding http authenticator failed");
    }
    if (base64_authenticator) {
      tor_snprintf(proxyauthstring, sizeof(proxyauthstring),
                   "\r\nProxy-Authorization: Basic %s",
                   base64_authenticator);
      tor_free(base64_authenticator);
    } else {
      proxyauthstring[0] = 0;
    }
  } else {
    proxystring[0] = 0;
    proxyauthstring[0] = 0;
  }

  switch (purpose) {
    case DIR_PURPOSE_FETCH_DIR:
      tor_assert(!resource);
      tor_assert(!payload);
      httpcommand = "GET";
      url = tor_strdup("/tor/dir.z");
      break;
    case DIR_PURPOSE_FETCH_RUNNING_LIST:
      tor_assert(!resource);
      tor_assert(!payload);
      httpcommand = "GET";
      url = tor_strdup("/tor/running-routers");
      break;
    case DIR_PURPOSE_FETCH_NETWORKSTATUS:
      httpcommand = "GET";
      len = strlen(resource)+32;
      url = tor_malloc(len);
      tor_snprintf(url, len, "/tor/status/%s", resource);
      break;
    case DIR_PURPOSE_FETCH_CONSENSUS:
      tor_assert(!resource);
      tor_assert(!payload);
      httpcommand = "GET";
      url = directory_get_consensus_url(supports_conditional_consensus);
      /* XXX021: downgrade/remove once done with conditional consensus fu */
      log_notice(LD_DIR, "Downloading consensus from %s using %s",
                 hoststring, url);
      break;
    case DIR_PURPOSE_FETCH_CERTIFICATE:
      tor_assert(resource);
      tor_assert(!payload);
      httpcommand = "GET";
      len = strlen(resource)+32;
      url = tor_malloc(len);
      tor_snprintf(url, len, "/tor/keys/%s", resource);
      break;
    case DIR_PURPOSE_FETCH_STATUS_VOTE:
      tor_assert(resource);
      tor_assert(!payload);
      httpcommand = "GET";
      len = strlen(resource)+32;
      url = tor_malloc(len);
      tor_snprintf(url, len, "/tor/status-vote/next/%s.z", resource);
      break;
    case DIR_PURPOSE_FETCH_DETACHED_SIGNATURES:
      tor_assert(!resource);
      tor_assert(!payload);
      httpcommand = "GET";
      url = tor_strdup("/tor/status-vote/next/consensus-signatures.z");
      break;
    case DIR_PURPOSE_FETCH_SERVERDESC:
      httpcommand = "GET";
      len = strlen(resource)+32;
      url = tor_malloc(len);
      tor_snprintf(url, len, "/tor/server/%s", resource);
      break;
    case DIR_PURPOSE_FETCH_EXTRAINFO:
      httpcommand = "GET";
      len = strlen(resource)+32;
      url = tor_malloc(len);
      tor_snprintf(url, len, "/tor/extra/%s", resource);
      break;
    case DIR_PURPOSE_UPLOAD_DIR:
      tor_assert(!resource);
      tor_assert(payload);
      httpcommand = "POST";
      url = tor_strdup("/tor/");
      break;
    case DIR_PURPOSE_UPLOAD_VOTE:
      tor_assert(!resource);
      tor_assert(payload);
      httpcommand = "POST";
      url = tor_strdup("/tor/post/vote");
      break;
    case DIR_PURPOSE_UPLOAD_SIGNATURES:
      tor_assert(!resource);
      tor_assert(payload);
      httpcommand = "POST";
      url = tor_strdup("/tor/post/consensus-signature");
      break;
    case DIR_PURPOSE_FETCH_RENDDESC:
      tor_assert(resource);
      tor_assert(!payload);

      /* this must be true or we wouldn't be doing the lookup */
      tor_assert(strlen(resource) <= REND_SERVICE_ID_LEN_BASE32);
      /* This breaks the function abstraction. */
      strlcpy(conn->rend_query, resource, sizeof(conn->rend_query));
      conn->rend_version = 0;

      httpcommand = "GET";
      /* Request the most recent versioned descriptor. */
      // (XXXX We were going to switch this to fetch rendezvous1 descriptors,
      // but that never got testing, and it wasn't a good design.)
      len = strlen(resource)+32;
      url = tor_malloc(len);
      tor_snprintf(url, len, "/tor/rendezvous/%s", resource);
      break;
    case DIR_PURPOSE_FETCH_RENDDESC_V2:
      tor_assert(resource);
      tor_assert(strlen(resource) <= REND_DESC_ID_V2_LEN_BASE32);
      /* Remember the query to refer to it when a response arrives. */