control_cmd.c 82.7 KB
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/* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
 * Copyright (c) 2007-2019, The Tor Project, Inc. */
/* See LICENSE for licensing information */

/**
 * \file control_cmd.c
 * \brief Implement various commands for Tor's control-socket interface.
 **/

#define CONTROL_MODULE_PRIVATE
#define CONTROL_CMD_PRIVATE
#define CONTROL_EVENTS_PRIVATE

#include "core/or/or.h"
#include "app/config/config.h"
#include "app/config/confparse.h"
#include "app/main/main.h"
#include "core/mainloop/connection.h"
#include "core/or/circuitbuild.h"
#include "core/or/circuitlist.h"
#include "core/or/circuituse.h"
#include "core/or/connection_edge.h"
#include "feature/client/addressmap.h"
#include "feature/client/dnsserv.h"
#include "feature/client/entrynodes.h"
#include "feature/control/control.h"
#include "feature/control/control_auth.h"
#include "feature/control/control_cmd.h"
#include "feature/control/control_events.h"
#include "feature/control/control_fmt.h"
#include "feature/control/control_getinfo.h"
#include "feature/hs/hs_control.h"
#include "feature/nodelist/nodelist.h"
#include "feature/nodelist/routerinfo.h"
#include "feature/nodelist/routerlist.h"
#include "feature/rend/rendclient.h"
#include "feature/rend/rendcommon.h"
#include "feature/rend/rendparse.h"
#include "feature/rend/rendservice.h"
#include "lib/crypt_ops/crypto_rand.h"
#include "lib/crypt_ops/crypto_util.h"
#include "lib/encoding/confline.h"
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#include "lib/encoding/kvline.h"
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#include "core/or/cpath_build_state_st.h"
#include "core/or/entry_connection_st.h"
#include "core/or/origin_circuit_st.h"
#include "core/or/socks_request_st.h"
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#include "feature/control/control_cmd_args_st.h"
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#include "feature/control/control_connection_st.h"
#include "feature/nodelist/node_st.h"
#include "feature/nodelist/routerinfo_st.h"
#include "feature/rend/rend_authorized_client_st.h"
#include "feature/rend/rend_encoded_v2_service_descriptor_st.h"
#include "feature/rend/rend_service_descriptor_st.h"

static int control_setconf_helper(control_connection_t *conn, uint32_t len,
                                  char *body,
                                  int use_defaults);

/** Yield true iff <b>s</b> is the state of a control_connection_t that has
 * finished authentication and is accepting commands. */
#define STATE_IS_OPEN(s) ((s) == CONTROL_CONN_STATE_OPEN)

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/**
 * Release all storage held in <b>args</b>
 **/
void
control_cmd_args_free_(control_cmd_args_t *args)
{
  if (! args)
    return;

  if (args->args) {
    SMARTLIST_FOREACH(args->args, char *, c, tor_free(c));
    smartlist_free(args->args);
  }
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  config_free_lines(args->kwargs);
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  tor_free(args->object);

  tor_free(args);
}

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/**
 * Return true iff any element of the NULL-terminated <b>array</b> matches
 * <b>kwd</b>. Case-insensitive.
 **/
static bool
string_array_contains_keyword(const char **array, const char *kwd)
{
  for (unsigned i = 0; array[i]; ++i) {
    if (! strcasecmp(array[i], kwd))
      return true;
  }
  return false;
}


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/**
 * Helper: parse the arguments to a command according to <b>syntax</b>.  On
 * success, set *<b>error_out</b> to NULL and return a newly allocated
 * control_cmd_args_t.  On failure, set *<b>error_out</b> to newly allocated
 * error string, and return NULL.
 **/
STATIC control_cmd_args_t *
control_cmd_parse_args(const char *command,
                       const control_cmd_syntax_t *syntax,
                       size_t body_len,
                       const char *body,
                       char **error_out)
{
  *error_out = NULL;
  control_cmd_args_t *result = tor_malloc_zero(sizeof(control_cmd_args_t));
  const char *cmdline;
  char *cmdline_alloc = NULL;
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  tor_assert(syntax->max_args < INT_MAX || syntax->max_args == UINT_MAX);
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  result->command = command;

  const char *eol = memchr(body, '\n', body_len);
  if (syntax->want_object) {
    if (! eol || (eol+1) == body+body_len) {
      *error_out = tor_strdup("Empty body");
      goto err;
    }
    cmdline_alloc = tor_memdup_nulterm(body, eol-body);
    cmdline = cmdline_alloc;
    ++eol;
    result->object_len = read_escaped_data(eol, (body+body_len)-eol,
                                           &result->object);
  } else {
    if (eol && (eol+1) != body+body_len) {
      *error_out = tor_strdup("Unexpected body");
      goto err;
    }
    cmdline = body;
  }

  result->args = smartlist_new();
  smartlist_split_string(result->args, cmdline, " ",
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                         SPLIT_SKIP_SPACE|SPLIT_IGNORE_BLANK,
                         (int)(syntax->max_args+1));
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  size_t n_args = smartlist_len(result->args);
  if (n_args < syntax->min_args) {
    tor_asprintf(error_out, "Need at least %u argument(s)",
                 syntax->min_args);
    goto err;
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  } else if (n_args > syntax->max_args && ! syntax->accept_keywords) {
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    tor_asprintf(error_out, "Cannot accept more than %u argument(s)",
                 syntax->max_args);
    goto err;
  }

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  if (n_args > syntax->max_args) {
    tor_assert(n_args == syntax->max_args + 1);
    tor_assert(syntax->accept_keywords);
    char *remainder = smartlist_pop_last(result->args);
    result->kwargs = kvline_parse(remainder, syntax->kvline_flags);
    tor_free(remainder);
    if (result->kwargs == NULL) {
      tor_asprintf(error_out, "Cannot parse keyword argument(s)");
      goto err;
    }
    if (syntax->allowed_keywords) {
      /* Check for unpermitted arguments */
      const config_line_t *line;
      for (line = result->kwargs; line; line = line->next) {
        if (! string_array_contains_keyword(syntax->allowed_keywords,
                                            line->key)) {
          tor_asprintf(error_out, "Unrecognized keyword argument %s",
                       escaped(line->key));
        }
      }
    }
  }

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  tor_assert_nonfatal(*error_out == NULL);
  goto done;
 err:
  tor_assert_nonfatal(*error_out != NULL);
  control_cmd_args_free(result);
 done:
  tor_free(cmdline_alloc);
  return result;
}

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/** Called when we receive a SETCONF message: parse the body and try
 * to update our configuration.  Reply with a DONE or ERROR message.
 * Modifies the contents of body.*/
static int
handle_control_setconf(control_connection_t *conn, uint32_t len, char *body)
{
  return control_setconf_helper(conn, len, body, 0);
}

/** Called when we receive a RESETCONF message: parse the body and try
 * to update our configuration.  Reply with a DONE or ERROR message.
 * Modifies the contents of body. */
static int
handle_control_resetconf(control_connection_t *conn, uint32_t len, char *body)
{
  return control_setconf_helper(conn, len, body, 1);
}

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static const control_cmd_syntax_t getconf_syntax = {
  .max_args=UINT_MAX
};

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/** Called when we receive a GETCONF message.  Parse the request, and
 * reply with a CONFVALUE or an ERROR message */
static int
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handle_control_getconf(control_connection_t *conn,
                       const control_cmd_args_t *args)
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{
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  const smartlist_t *questions = args->args;
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  smartlist_t *answers = smartlist_new();
  smartlist_t *unrecognized = smartlist_new();
  char *msg = NULL;
  size_t msg_len;
  const or_options_t *options = get_options();
  int i, len;

  SMARTLIST_FOREACH_BEGIN(questions, const char *, q) {
    if (!option_is_recognized(q)) {
      smartlist_add(unrecognized, (char*) q);
    } else {
      config_line_t *answer = option_get_assignment(options,q);
      if (!answer) {
        const char *name = option_get_canonical_name(q);
        smartlist_add_asprintf(answers, "250-%s\r\n", name);
      }

      while (answer) {
        config_line_t *next;
        smartlist_add_asprintf(answers, "250-%s=%s\r\n",
                     answer->key, answer->value);

        next = answer->next;
        tor_free(answer->key);
        tor_free(answer->value);
        tor_free(answer);
        answer = next;
      }
    }
  } SMARTLIST_FOREACH_END(q);

  if ((len = smartlist_len(unrecognized))) {
    for (i=0; i < len-1; ++i)
      connection_printf_to_buf(conn,
                               "552-Unrecognized configuration key \"%s\"\r\n",
                               (char*)smartlist_get(unrecognized, i));
    connection_printf_to_buf(conn,
                             "552 Unrecognized configuration key \"%s\"\r\n",
                             (char*)smartlist_get(unrecognized, len-1));
  } else if ((len = smartlist_len(answers))) {
    char *tmp = smartlist_get(answers, len-1);
    tor_assert(strlen(tmp)>4);
    tmp[3] = ' ';
    msg = smartlist_join_strings(answers, "", 0, &msg_len);
    connection_buf_add(msg, msg_len, TO_CONN(conn));
  } else {
    connection_write_str_to_buf("250 OK\r\n", conn);
  }

  SMARTLIST_FOREACH(answers, char *, cp, tor_free(cp));
  smartlist_free(answers);
  smartlist_free(unrecognized);

  tor_free(msg);

  return 0;
}

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static const control_cmd_syntax_t loadconf_syntax = {
  .want_object = true
};

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/** Called when we get a +LOADCONF message. */
static int
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handle_control_loadconf(control_connection_t *conn,
                        const control_cmd_args_t *args)
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{
  setopt_err_t retval;
  char *errstring = NULL;
  const char *msg = NULL;

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  retval = options_init_from_string(NULL, args->object,
                                    CMD_RUN_TOR, NULL, &errstring);
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  if (retval != SETOPT_OK)
    log_warn(LD_CONTROL,
             "Controller gave us config file that didn't validate: %s",
             errstring);

  switch (retval) {
  case SETOPT_ERR_PARSE:
    msg = "552 Invalid config file";
    break;
  case SETOPT_ERR_TRANSITION:
    msg = "553 Transition not allowed";
    break;
  case SETOPT_ERR_SETTING:
    msg = "553 Unable to set option";
    break;
  case SETOPT_ERR_MISC:
  default:
    msg = "550 Unable to load config";
    break;
  case SETOPT_OK:
    break;
  }
  if (msg) {
    if (errstring)
      connection_printf_to_buf(conn, "%s: %s\r\n", msg, errstring);
    else
      connection_printf_to_buf(conn, "%s\r\n", msg);
  } else {
    send_control_done(conn);
  }
  tor_free(errstring);
  return 0;
}

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static const control_cmd_syntax_t setevents_syntax = {
  .max_args = UINT_MAX
};

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/** Called when we get a SETEVENTS message: update conn->event_mask,
 * and reply with DONE or ERROR. */
static int
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handle_control_setevents(control_connection_t *conn,
                         const control_cmd_args_t *args)
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{
  int event_code;
  event_mask_t event_mask = 0;
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  const smartlist_t *events = args->args;
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  SMARTLIST_FOREACH_BEGIN(events, const char *, ev)
    {
      if (!strcasecmp(ev, "EXTENDED") ||
          !strcasecmp(ev, "AUTHDIR_NEWDESCS")) {
        log_warn(LD_CONTROL, "The \"%s\" SETEVENTS argument is no longer "
                 "supported.", ev);
        continue;
      } else {
        int i;
        event_code = -1;

        for (i = 0; control_event_table[i].event_name != NULL; ++i) {
          if (!strcasecmp(ev, control_event_table[i].event_name)) {
            event_code = control_event_table[i].event_code;
            break;
          }
        }

        if (event_code == -1) {
          connection_printf_to_buf(conn, "552 Unrecognized event \"%s\"\r\n",
                                   ev);
          return 0;
        }
      }
      event_mask |= (((event_mask_t)1) << event_code);
    }
  SMARTLIST_FOREACH_END(ev);

  conn->event_mask = event_mask;

  control_update_global_event_mask();
  send_control_done(conn);
  return 0;
}

/** Called when we get a SAVECONF command. Try to flush the current options to
 * disk, and report success or failure. */
static int
handle_control_saveconf(control_connection_t *conn, uint32_t len,
                        const char *body)
{
  (void) len;

  int force = !strcmpstart(body, "FORCE");
  const or_options_t *options = get_options();
  if ((!force && options->IncludeUsed) || options_save_current() < 0) {
    connection_write_str_to_buf(
      "551 Unable to write configuration to disk.\r\n", conn);
  } else {
    send_control_done(conn);
  }
  return 0;
}

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static const control_cmd_syntax_t signal_syntax = {
  .min_args = 1,
  .max_args = 1,
};

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/** Called when we get a SIGNAL command. React to the provided signal, and
 * report success or failure. (If the signal results in a shutdown, success
 * may not be reported.) */
static int
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handle_control_signal(control_connection_t *conn,
                      const control_cmd_args_t *args)
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{
  int sig = -1;
  int i;

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  tor_assert(smartlist_len(args->args) == 1);
  const char *s = smartlist_get(args->args, 0);
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  for (i = 0; signal_table[i].signal_name != NULL; ++i) {
    if (!strcasecmp(s, signal_table[i].signal_name)) {
      sig = signal_table[i].sig;
      break;
    }
  }

  if (sig < 0)
    connection_printf_to_buf(conn, "552 Unrecognized signal code \"%s\"\r\n",
                             s);
  if (sig < 0)
    return 0;

  send_control_done(conn);
  /* Flush the "done" first if the signal might make us shut down. */
  if (sig == SIGTERM || sig == SIGINT)
    connection_flush(TO_CONN(conn));

  activate_signal(sig);

  return 0;
}

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static const control_cmd_syntax_t takeownership_syntax = {
  .max_args = UINT_MAX, // This should probably become zero. XXXXX
};

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/** Called when we get a TAKEOWNERSHIP command.  Mark this connection
 * as an owning connection, so that we will exit if the connection
 * closes. */
static int
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handle_control_takeownership(control_connection_t *conn,
                             const control_cmd_args_t *args)
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{
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  (void)args;
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  conn->is_owning_control_connection = 1;

  log_info(LD_CONTROL, "Control connection %d has taken ownership of this "
           "Tor instance.",
           (int)(conn->base_.s));

  send_control_done(conn);
  return 0;
}

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static const control_cmd_syntax_t dropownership_syntax = {
  .max_args = UINT_MAX, // This should probably become zero. XXXXX
};

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/** Called when we get a DROPOWNERSHIP command.  Mark this connection
 * as a non-owning connection, so that we will not exit if the connection
 * closes. */
static int
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handle_control_dropownership(control_connection_t *conn,
                             const control_cmd_args_t *args)
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{
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  (void)args;
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1000

  conn->is_owning_control_connection = 0;

  log_info(LD_CONTROL, "Control connection %d has dropped ownership of this "
           "Tor instance.",
           (int)(conn->base_.s));

  send_control_done(conn);
  return 0;
}

/** Given a text circuit <b>id</b>, return the corresponding circuit. */
static origin_circuit_t *
get_circ(const char *id)
{
  uint32_t n_id;
  int ok;
  n_id = (uint32_t) tor_parse_ulong(id, 10, 0, UINT32_MAX, &ok, NULL);
  if (!ok)
    return NULL;
  return circuit_get_by_global_id(n_id);
}

/** Given a text stream <b>id</b>, return the corresponding AP connection. */
static entry_connection_t *
get_stream(const char *id)
{
  uint64_t n_id;
  int ok;
  connection_t *conn;
  n_id = tor_parse_uint64(id, 10, 0, UINT64_MAX, &ok, NULL);
  if (!ok)
    return NULL;
  conn = connection_get_by_global_id(n_id);
  if (!conn || conn->type != CONN_TYPE_AP || conn->marked_for_close)
    return NULL;
  return TO_ENTRY_CONN(conn);
}

/** Helper for setconf and resetconf. Acts like setconf, except
 * it passes <b>use_defaults</b> on to options_trial_assign().  Modifies the
 * contents of body.
 */
static int
control_setconf_helper(control_connection_t *conn, uint32_t len, char *body,
                       int use_defaults)
{
  setopt_err_t opt_err;
  config_line_t *lines=NULL;
  char *start = body;
  char *errstring = NULL;
  const unsigned flags =
    CAL_CLEAR_FIRST | (use_defaults ? CAL_USE_DEFAULTS : 0);

  char *config;
  smartlist_t *entries = smartlist_new();

  /* We have a string, "body", of the format '(key(=val|="val")?)' entries
   * separated by space.  break it into a list of configuration entries. */
  while (*body) {
    char *eq = body;
    char *key;
    char *entry;
    while (!TOR_ISSPACE(*eq) && *eq != '=')
      ++eq;
    key = tor_strndup(body, eq-body);
    body = eq+1;
    if (*eq == '=') {
      char *val=NULL;
      size_t val_len=0;
      if (*body != '\"') {
        char *val_start = body;
        while (!TOR_ISSPACE(*body))
          body++;
        val = tor_strndup(val_start, body-val_start);
        val_len = strlen(val);
      } else {
        body = (char*)extract_escaped_string(body, (len - (body-start)),
                                             &val, &val_len);
        if (!body) {
          connection_write_str_to_buf("551 Couldn't parse string\r\n", conn);
          SMARTLIST_FOREACH(entries, char *, cp, tor_free(cp));
          smartlist_free(entries);
          tor_free(key);
          return 0;
        }
      }
      tor_asprintf(&entry, "%s %s", key, val);
      tor_free(key);
      tor_free(val);
    } else {
      entry = key;
    }
    smartlist_add(entries, entry);
    while (TOR_ISSPACE(*body))
      ++body;
  }

  smartlist_add_strdup(entries, "");
  config = smartlist_join_strings(entries, "\n", 0, NULL);
  SMARTLIST_FOREACH(entries, char *, cp, tor_free(cp));
  smartlist_free(entries);

  if (config_get_lines(config, &lines, 0) < 0) {
    log_warn(LD_CONTROL,"Controller gave us config lines we can't parse.");
    connection_write_str_to_buf("551 Couldn't parse configuration\r\n",
                                conn);
    tor_free(config);
    return 0;
  }
  tor_free(config);

  opt_err = options_trial_assign(lines, flags, &errstring);
  {
    const char *msg;
    switch (opt_err) {
      case SETOPT_ERR_MISC:
        msg = "552 Unrecognized option";
        break;
      case SETOPT_ERR_PARSE:
        msg = "513 Unacceptable option value";
        break;
      case SETOPT_ERR_TRANSITION:
        msg = "553 Transition not allowed";
        break;
      case SETOPT_ERR_SETTING:
      default:
        msg = "553 Unable to set option";
        break;
      case SETOPT_OK:
        config_free_lines(lines);
        send_control_done(conn);
        return 0;
    }
    log_warn(LD_CONTROL,
             "Controller gave us config lines that didn't validate: %s",
             errstring);
    connection_printf_to_buf(conn, "%s: %s\r\n", msg, errstring);
    config_free_lines(lines);
    tor_free(errstring);
    return 0;
  }
}

/** Return true iff <b>addr</b> is unusable as a mapaddress target because of
 * containing funny characters. */
static int
address_is_invalid_mapaddress_target(const char *addr)
{
  if (!strcmpstart(addr, "*."))
    return address_is_invalid_destination(addr+2, 1);
  else
    return address_is_invalid_destination(addr, 1);
}

/** Called when we get a MAPADDRESS command; try to bind all listed addresses,
 * and report success or failure. */
static int
handle_control_mapaddress(control_connection_t *conn, uint32_t len,
                          const char *body)
{
  smartlist_t *elts;
  smartlist_t *lines;
  smartlist_t *reply;
  char *r;
  size_t sz;
  (void) len; /* body is NUL-terminated, so it's safe to ignore the length. */

  lines = smartlist_new();
  elts = smartlist_new();
  reply = smartlist_new();
  smartlist_split_string(lines, body, " ",
                         SPLIT_SKIP_SPACE|SPLIT_IGNORE_BLANK, 0);
  SMARTLIST_FOREACH_BEGIN(lines, char *, line) {
    tor_strlower(line);
    smartlist_split_string(elts, line, "=", 0, 2);
    if (smartlist_len(elts) == 2) {
      const char *from = smartlist_get(elts,0);
      const char *to = smartlist_get(elts,1);
      if (address_is_invalid_mapaddress_target(to)) {
        smartlist_add_asprintf(reply,
                     "512-syntax error: invalid address '%s'", to);
        log_warn(LD_CONTROL,
                 "Skipping invalid argument '%s' in MapAddress msg", to);
      } else if (!strcmp(from, ".") || !strcmp(from, "0.0.0.0") ||
                 !strcmp(from, "::")) {
        const char type =
          !strcmp(from,".") ? RESOLVED_TYPE_HOSTNAME :
          (!strcmp(from, "0.0.0.0") ? RESOLVED_TYPE_IPV4 : RESOLVED_TYPE_IPV6);
        const char *address = addressmap_register_virtual_address(
                                                     type, tor_strdup(to));
        if (!address) {
          smartlist_add_asprintf(reply,
                       "451-resource exhausted: skipping '%s'", line);
          log_warn(LD_CONTROL,
                   "Unable to allocate address for '%s' in MapAddress msg",
                   safe_str_client(line));
        } else {
          smartlist_add_asprintf(reply, "250-%s=%s", address, to);
        }
      } else {
        const char *msg;
        if (addressmap_register_auto(from, to, 1,
                                     ADDRMAPSRC_CONTROLLER, &msg) < 0) {
          smartlist_add_asprintf(reply,
                                 "512-syntax error: invalid address mapping "
                                 " '%s': %s", line, msg);
          log_warn(LD_CONTROL,
                   "Skipping invalid argument '%s' in MapAddress msg: %s",
                   line, msg);
        } else {
          smartlist_add_asprintf(reply, "250-%s", line);
        }
      }
    } else {
      smartlist_add_asprintf(reply, "512-syntax error: mapping '%s' is "
                   "not of expected form 'foo=bar'.", line);
      log_info(LD_CONTROL, "Skipping MapAddress '%s': wrong "
                           "number of items.",
                           safe_str_client(line));
    }
    SMARTLIST_FOREACH(elts, char *, cp, tor_free(cp));
    smartlist_clear(elts);
  } SMARTLIST_FOREACH_END(line);
  SMARTLIST_FOREACH(lines, char *, cp, tor_free(cp));
  smartlist_free(lines);
  smartlist_free(elts);

  if (smartlist_len(reply)) {
    ((char*)smartlist_get(reply,smartlist_len(reply)-1))[3] = ' ';
    r = smartlist_join_strings(reply, "\r\n", 1, &sz);
    connection_buf_add(r, sz, TO_CONN(conn));
    tor_free(r);
  } else {
    const char *response =
      "512 syntax error: not enough arguments to mapaddress.\r\n";
    connection_buf_add(response, strlen(response), TO_CONN(conn));
  }

  SMARTLIST_FOREACH(reply, char *, cp, tor_free(cp));
  smartlist_free(reply);
  return 0;
}

/** Given a string, convert it to a circuit purpose. */
static uint8_t
circuit_purpose_from_string(const char *string)
{
  if (!strcasecmpstart(string, "purpose="))
    string += strlen("purpose=");

  if (!strcasecmp(string, "general"))
    return CIRCUIT_PURPOSE_C_GENERAL;
  else if (!strcasecmp(string, "controller"))
    return CIRCUIT_PURPOSE_CONTROLLER;
  else
    return CIRCUIT_PURPOSE_UNKNOWN;
}

/** Return a newly allocated smartlist containing the arguments to the command
 * waiting in <b>body</b>. If there are fewer than <b>min_args</b> arguments,
 * or if <b>max_args</b> is nonnegative and there are more than
 * <b>max_args</b> arguments, send a 512 error to the controller, using
 * <b>command</b> as the command name in the error message. */
static smartlist_t *
getargs_helper(const char *command, control_connection_t *conn,
               const char *body, int min_args, int max_args)
{
  smartlist_t *args = smartlist_new();
  smartlist_split_string(args, body, " ",
                         SPLIT_SKIP_SPACE|SPLIT_IGNORE_BLANK, 0);
  if (smartlist_len(args) < min_args) {
    connection_printf_to_buf(conn, "512 Missing argument to %s\r\n",command);
    goto err;
  } else if (max_args >= 0 && smartlist_len(args) > max_args) {
    connection_printf_to_buf(conn, "512 Too many arguments to %s\r\n",command);
    goto err;
  }
  return args;
 err:
  SMARTLIST_FOREACH(args, char *, s, tor_free(s));
  smartlist_free(args);
  return NULL;
}

/** Helper.  Return the first element of <b>sl</b> at index <b>start_at</b> or
 * higher that starts with <b>prefix</b>, case-insensitive.  Return NULL if no
 * such element exists. */
static const char *
find_element_starting_with(smartlist_t *sl, int start_at, const char *prefix)
{
  int i;
  for (i = start_at; i < smartlist_len(sl); ++i) {
    const char *elt = smartlist_get(sl, i);
    if (!strcasecmpstart(elt, prefix))
      return elt;
  }
  return NULL;
}

/** Helper.  Return true iff s is an argument that we should treat as a
 * key-value pair. */
static int
is_keyval_pair(const char *s)
{
  /* An argument is a key-value pair if it has an =, and it isn't of the form
   * $fingeprint=name */
  return strchr(s, '=') && s[0] != '$';
}

/** Called when we get an EXTENDCIRCUIT message.  Try to extend the listed
 * circuit, and report success or failure. */
static int
handle_control_extendcircuit(control_connection_t *conn, uint32_t len,
                             const char *body)
{
  smartlist_t *router_nicknames=NULL, *nodes=NULL;
  origin_circuit_t *circ = NULL;
  int zero_circ;
  uint8_t intended_purpose = CIRCUIT_PURPOSE_C_GENERAL;
  smartlist_t *args;
  (void) len;

  router_nicknames = smartlist_new();

  args = getargs_helper("EXTENDCIRCUIT", conn, body, 1, -1);
  if (!args)
    goto done;

  zero_circ = !strcmp("0", (char*)smartlist_get(args,0));

  if (zero_circ) {
    const char *purp = find_element_starting_with(args, 1, "PURPOSE=");

    if (purp) {
      intended_purpose = circuit_purpose_from_string(purp);
      if (intended_purpose == CIRCUIT_PURPOSE_UNKNOWN) {
        connection_printf_to_buf(conn, "552 Unknown purpose \"%s\"\r\n", purp);
        SMARTLIST_FOREACH(args, char *, cp, tor_free(cp));
        smartlist_free(args);
        goto done;
      }
    }

    if ((smartlist_len(args) == 1) ||
        (smartlist_len(args) >= 2 && is_keyval_pair(smartlist_get(args, 1)))) {
      // "EXTENDCIRCUIT 0" || EXTENDCIRCUIT 0 foo=bar"
      circ = circuit_launch(intended_purpose, CIRCLAUNCH_NEED_CAPACITY);
      if (!circ) {
        connection_write_str_to_buf("551 Couldn't start circuit\r\n", conn);
      } else {
        connection_printf_to_buf(conn, "250 EXTENDED %lu\r\n",
                  (unsigned long)circ->global_identifier);
      }
      SMARTLIST_FOREACH(args, char *, cp, tor_free(cp));
      smartlist_free(args);
      goto done;
    }
    // "EXTENDCIRCUIT 0 router1,router2" ||
    // "EXTENDCIRCUIT 0 router1,router2 PURPOSE=foo"
  }

  if (!zero_circ && !(circ = get_circ(smartlist_get(args,0)))) {
    connection_printf_to_buf(conn, "552 Unknown circuit \"%s\"\r\n",
                             (char*)smartlist_get(args, 0));
    SMARTLIST_FOREACH(args, char *, cp, tor_free(cp));
    smartlist_free(args);
    goto done;
  }

  if (smartlist_len(args) < 2) {
    connection_printf_to_buf(conn,
                             "512 syntax error: not enough arguments.\r\n");
    SMARTLIST_FOREACH(args, char *, cp, tor_free(cp));
    smartlist_free(args);
    goto done;
  }

  smartlist_split_string(router_nicknames, smartlist_get(args,1), ",", 0, 0);

  SMARTLIST_FOREACH(args, char *, cp, tor_free(cp));
  smartlist_free(args);

  nodes = smartlist_new();
  int first_node = zero_circ;
  SMARTLIST_FOREACH_BEGIN(router_nicknames, const char *, n) {
    const node_t *node = node_get_by_nickname(n, 0);
    if (!node) {
      connection_printf_to_buf(conn, "552 No such router \"%s\"\r\n", n);
      goto done;
    }
    if (!node_has_preferred_descriptor(node, first_node)) {
      connection_printf_to_buf(conn, "552 No descriptor for \"%s\"\r\n", n);
      goto done;
    }
    smartlist_add(nodes, (void*)node);
    first_node = 0;
  } SMARTLIST_FOREACH_END(n);
  if (!smartlist_len(nodes)) {
    connection_write_str_to_buf("512 No router names provided\r\n", conn);
    goto done;
  }

  if (zero_circ) {
    /* start a new circuit */
    circ = origin_circuit_init(intended_purpose, 0);
  }

  /* now circ refers to something that is ready to be extended */
  first_node = zero_circ;
  SMARTLIST_FOREACH(nodes, const node_t *, node,
  {
    extend_info_t *info = extend_info_from_node(node, first_node);
    if (!info) {
      tor_assert_nonfatal(first_node);
      log_warn(LD_CONTROL,
               "controller tried to connect to a node that lacks a suitable "
               "descriptor, or which doesn't have any "
               "addresses that are allowed by the firewall configuration; "
               "circuit marked for closing.");
      circuit_mark_for_close(TO_CIRCUIT(circ), -END_CIRC_REASON_CONNECTFAILED);
      connection_write_str_to_buf("551 Couldn't start circuit\r\n", conn);
      goto done;
    }
    circuit_append_new_exit(circ, info);
    if (circ->build_state->desired_path_len > 1) {
      circ->build_state->onehop_tunnel = 0;
    }
    extend_info_free(info);
    first_node = 0;
  });

  /* now that we've populated the cpath, start extending */
  if (zero_circ) {
    int err_reason = 0;
    if ((err_reason = circuit_handle_first_hop(circ)) < 0) {
      circuit_mark_for_close(TO_CIRCUIT(circ), -err_reason);
      connection_write_str_to_buf("551 Couldn't start circuit\r\n", conn);
      goto done;
    }
  } else {
    if (circ->base_.state == CIRCUIT_STATE_OPEN ||
        circ->base_.state == CIRCUIT_STATE_GUARD_WAIT) {
      int err_reason = 0;
      circuit_set_state(TO_CIRCUIT(circ), CIRCUIT_STATE_BUILDING);
      if ((err_reason = circuit_send_next_onion_skin(circ)) < 0) {
        log_info(LD_CONTROL,
                 "send_next_onion_skin failed; circuit marked for closing.");
        circuit_mark_for_close(TO_CIRCUIT(circ), -err_reason);
        connection_write_str_to_buf("551 Couldn't send onion skin\r\n", conn);
        goto done;
      }
    }
  }

  connection_printf_to_buf(conn, "250 EXTENDED %lu\r\n",
                             (unsigned long)circ->global_identifier);
  if (zero_circ) /* send a 'launched' event, for completeness */
    circuit_event_status(circ, CIRC_EVENT_LAUNCHED, 0);
 done:
  SMARTLIST_FOREACH(router_nicknames, char *, n, tor_free(n));
  smartlist_free(router_nicknames);
  smartlist_free(nodes);
  return 0;
}

/** Called when we get a SETCIRCUITPURPOSE message. If we can find the
 * circuit and it's a valid purpose, change it. */
static int
handle_control_setcircuitpurpose(control_connection_t *conn,
                                 uint32_t len, const char *body)
{
  origin_circuit_t *circ = NULL;
  uint8_t new_purpose;
  smartlist_t *args;
  (void) len; /* body is NUL-terminated, so it's safe to ignore the length. */

  args = getargs_helper("SETCIRCUITPURPOSE", conn, body, 2, -1);
  if (!args)
    goto done;

  if (!(circ = get_circ(smartlist_get(args,0)))) {
    connection_printf_to_buf(conn, "552 Unknown circuit \"%s\"\r\n",
                             (char*)smartlist_get(args, 0));
    goto done;
  }

  {
    const char *purp = find_element_starting_with(args,1,"PURPOSE=");
    if (!purp) {
      connection_write_str_to_buf("552 No purpose given\r\n", conn);
      goto done;
    }
    new_purpose = circuit_purpose_from_string(purp);
    if (new_purpose == CIRCUIT_PURPOSE_UNKNOWN) {
      connection_printf_to_buf(conn, "552 Unknown purpose \"%s\"\r\n", purp);
      goto done;
    }
  }

  circuit_change_purpose(TO_CIRCUIT(circ), new_purpose);
  connection_write_str_to_buf("250 OK\r\n", conn);

 done:
  if (args) {
    SMARTLIST_FOREACH(args, char *, cp, tor_free(cp));
    smartlist_free(args);
  }
  return 0;
}

/** Called when we get an ATTACHSTREAM message.  Try to attach the requested
 * stream, and report success or failure. */
static int
handle_control_attachstream(control_connection_t *conn, uint32_t len,
                            const char *body)
{
  entry_connection_t *ap_conn = NULL;
  origin_circuit_t *circ = NULL;
  int zero_circ;
  smartlist_t *args;
  crypt_path_t *cpath=NULL;
  int hop=0, hop_line_ok=1;
  (void) len;

  args = getargs_helper("ATTACHSTREAM", conn, body, 2, -1);
  if (!args)
    return 0;

  zero_circ = !strcmp("0", (char*)smartlist_get(args,1));

  if (!(ap_conn = get_stream(smartlist_get(args, 0)))) {
    connection_printf_to_buf(conn, "552 Unknown stream \"%s\"\r\n",
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