config.c

/* Copyright 2001 Matej Pfajfar.
 * Copyright 2001-2004 Roger Dingledine.
 * Copyright 2004-2005 Roger Dingledine, Nick Mathewson. */
/* See LICENSE for licensing information */
/* $Id$ */
const char config_c_id[] = "$Id$";

/**
 * \file config.c
 * \brief Code to parse and interpret configuration files.
 **/

#include "or.h"
#ifdef MS_WINDOWS
#include <shlobj.h>
#endif
#include "../common/aes.h"

/** Enumeration of types which option values can take */
typedef enum config_type_t {
  CONFIG_TYPE_STRING = 0,   /**< An arbitrary string. */
  CONFIG_TYPE_UINT,         /**< A non-negative integer less than MAX_INT */
  CONFIG_TYPE_INTERVAL,     /**< A number of seconds, with optional units*/
  CONFIG_TYPE_MEMUNIT,      /**< A number of bytes, with optional units*/
  CONFIG_TYPE_DOUBLE,       /**< A floating-point value */
  CONFIG_TYPE_BOOL,         /**< A boolean value, expressed as 0 or 1. */
  CONFIG_TYPE_ISOTIME,      /**< An ISO-formated time relative to GMT. */
  CONFIG_TYPE_CSV,          /**< A list of strings, separated by commas and optional
                              * whitespace. */
  CONFIG_TYPE_LINELIST,     /**< Uninterpreted config lines */
  CONFIG_TYPE_LINELIST_S,   /**< Uninterpreted, context-sensitive config lines,
                             * mixed with other keywords. */
  CONFIG_TYPE_LINELIST_V,   /**< Catch-all "virtual" option to summarize
                             * context-sensitive config lines when fetching.
                             */
  CONFIG_TYPE_OBSOLETE,     /**< Obsolete (ignored) option. */
} config_type_t;

/* An abbreviation for a configuration option allowed on the command line */
typedef struct config_abbrev_t {
  const char *abbreviated;
  const char *full;
  int commandline_only;
} config_abbrev_t;

/* Handy macro for declaring "In the config file or on the command line,
 * you can abbreviate <b>tok</b>s as <b>tok</b>". */
#define PLURAL(tok) { #tok, #tok "s", 0 }

/* A list of command-line abbreviations. */
static config_abbrev_t _option_abbrevs[] = {
  PLURAL(ExitNode),
  PLURAL(EntryNode),
  PLURAL(ExcludeNode),
  PLURAL(FirewallPort),
  PLURAL(LongLivedPort),
  PLURAL(HiddenServiceNode),
  PLURAL(HiddenServiceExcludeNode),
  PLURAL(NumCpu),
  PLURAL(RendNode),
  PLURAL(RendExcludeNode),
  PLURAL(StrictEntryNode),
  PLURAL(StrictExitNode),
  { "l", "Log", 1},
  { "BandwidthRateBytes", "BandwidthRate", 0},
  { "BandwidthBurstBytes", "BandwidthBurst", 0},
  { "DirFetchPostPeriod", "StatusFetchPeriod", 0},
  { "MaxConn", "ConnLimit", 0},
  { NULL, NULL , 0},
};
#undef PLURAL

/** A variable allowed in the configuration file or on the command line. */
typedef struct config_var_t {
  const char *name; /**< The full keyword (case insensitive). */
  config_type_t type; /**< How to interpret the type and turn it into a value. */
  off_t var_offset; /**< Offset of the corresponding member of or_options_t. */
  const char *initvalue; /**< String (or null) describing initial value. */
  const char *description;
} config_var_t;

/** Return the offset of <b>member</b> within the type <b>tp</b>, in bytes */
#define STRUCT_OFFSET(tp, member) ((off_t) (((char*)&((tp*)0)->member)-(char*)0))
/** An entry for config_vars: "The option <b>name</b> has type
 * CONFIG_TYPE_<b>conftype</b>, and corresponds to
 * or_options_t.<b>member</b>"
 */
#define VAR(name,conftype,member,initvalue)                            \
  { name, CONFIG_TYPE_ ## conftype, STRUCT_OFFSET(or_options_t, member), initvalue }
/** An entry for config_vars: "The option <b>name</b> is obsolete." */
#define OBSOLETE(name) { name, CONFIG_TYPE_OBSOLETE, 0, NULL }

/** Array of configuration options.  Until we disallow nonstandard
 * abbreviations, order is significant, since the first matching option will
 * be chosen first.
 */
static config_var_t _option_vars[] = {
  VAR("Address",             STRING,   Address,              NULL),
  VAR("AccountingStart",     STRING,   AccountingStart,      NULL),
  VAR("AllowUnverifiedNodes",CSV,      AllowUnverifiedNodes, "middle,rendezvous"),
  VAR("AuthoritativeDirectory",BOOL,   AuthoritativeDir,     "0"),
  VAR("BandwidthRate",       MEMUNIT,  BandwidthRate,        "2 MB"),
  VAR("BandwidthBurst",      MEMUNIT,  BandwidthBurst,       "5 MB"),
  VAR("MaxAdvertisedBandwidth",MEMUNIT,MaxAdvertisedBandwidth,"128 TB"),
  VAR("ClientOnly",          BOOL,     ClientOnly,           "0"),
  VAR("ContactInfo",         STRING,   ContactInfo,          NULL),
  VAR("ControlPort",         UINT,     ControlPort,          "0"),
  VAR("CookieAuthentication",BOOL,     CookieAuthentication, "0"),
  VAR("DebugLogFile",        STRING,   DebugLogFile,         NULL),
  VAR("DataDirectory",       STRING,   DataDirectory,        NULL),
  VAR("DirAllowPrivateAddresses",BOOL, DirAllowPrivateAddresses, NULL),
  VAR("DirPort",             UINT,     DirPort,              "0"),
  VAR("DirBindAddress",      LINELIST, DirBindAddress,       NULL),
  /** DOCDOC **/
  VAR("DirFetchPeriod",      INTERVAL, DirFetchPeriod,       "0 seconds"),
  VAR("DirPostPeriod",       INTERVAL, DirPostPeriod,        "20 minutes"),
  VAR("RendPostPeriod",      INTERVAL, RendPostPeriod,       "20 minutes"),
  VAR("DirPolicy",           LINELIST, DirPolicy,            NULL),
  VAR("DirServer",           LINELIST, DirServers,           NULL),
  VAR("ExitNodes",           STRING,   ExitNodes,            NULL),
  VAR("EntryNodes",          STRING,   EntryNodes,           NULL),
  VAR("StrictExitNodes",     BOOL,     StrictExitNodes,      "0"),
  VAR("StrictEntryNodes",    BOOL,     StrictEntryNodes,     "0"),
  VAR("ExitPolicy",          LINELIST, ExitPolicy,           NULL),
  VAR("ExcludeNodes",        STRING,   ExcludeNodes,         NULL),
  VAR("TrackHostExits",      CSV,      TrackHostExits,       NULL),
  VAR("TrackHostExitsExpire",INTERVAL, TrackHostExitsExpire, "30 minutes"),
  VAR("MapAddress",          LINELIST, AddressMap,           NULL),
  VAR("FascistFirewall",     BOOL,     FascistFirewall,      "0"),
  VAR("FirewallPorts",       CSV,      FirewallPorts,        "80,443"),
  VAR("MyFamily",            STRING,   MyFamily,             NULL),
  VAR("NodeFamily",          LINELIST, NodeFamilies,         NULL),
  VAR("NoPublish",           BOOL,     NoPublish,            "0"),
  VAR("Group",               STRING,   Group,                NULL),
  VAR("HashedControlPassword",STRING,  HashedControlPassword, NULL),
  VAR("HttpProxy",           STRING,   HttpProxy,            NULL),
  VAR("HttpProxyAuthenticator",STRING, HttpProxyAuthenticator,NULL),
  VAR("HttpsProxy",          STRING,   HttpsProxy,           NULL),
  VAR("HttpsProxyAuthenticator",STRING,HttpsProxyAuthenticator,NULL),
  VAR("HardwareAccel",       BOOL,     HardwareAccel,        "1"),
  VAR("HiddenServiceOptions",LINELIST_V, RendConfigLines,    NULL),
  VAR("HiddenServiceDir",    LINELIST_S, RendConfigLines,    NULL),
  VAR("HiddenServicePort",   LINELIST_S, RendConfigLines,    NULL),
  VAR("HiddenServiceNodes",  LINELIST_S, RendConfigLines,    NULL),
  VAR("HiddenServiceExcludeNodes", LINELIST_S, RendConfigLines, NULL),
  VAR("IgnoreVersion",       BOOL,     IgnoreVersion,        "0"),
  VAR("KeepalivePeriod",     INTERVAL, KeepalivePeriod,      "5 minutes"),
  VAR("Log",                 LINELIST, Logs,                 NULL),
  VAR("LogLevel",            LINELIST_S, OldLogOptions,      NULL),
  VAR("LogFile",             LINELIST_S, OldLogOptions,      NULL),
  OBSOLETE("LinkPadding"),
  VAR("ConnLimit",           UINT,     ConnLimit,            "1024"),
  VAR("MaxOnionsPending",    UINT,     MaxOnionsPending,     "100"),
  VAR("MonthlyAccountingStart",UINT,   _MonthlyAccountingStart,"0"),
  VAR("AccountingMaxKB",     UINT,     _AccountingMaxKB,     "0"),
  VAR("AccountingMax",       MEMUNIT,   AccountingMax,        "0 bytes"),
  VAR("Nickname",            STRING,   Nickname,             NULL),
  VAR("NewCircuitPeriod",    INTERVAL, NewCircuitPeriod,     "30 seconds"),
  VAR("MaxCircuitDirtiness", INTERVAL, MaxCircuitDirtiness,  "10 minutes"),
  VAR("NumCpus",             UINT,     NumCpus,              "1"),
  VAR("ORPort",              UINT,     ORPort,               "0"),
  VAR("ORBindAddress",       LINELIST, ORBindAddress,        NULL),
  VAR("OutboundBindAddress", STRING,   OutboundBindAddress,  NULL),
  VAR("PidFile",             STRING,   PidFile,              NULL),
  VAR("LongLivedPorts",      CSV,      LongLivedPorts,       "21,22,706,1863,5050,5190,5222,5223,6667,8300,8888"),
  VAR("PathlenCoinWeight",   DOUBLE,   PathlenCoinWeight,    "0.3"),
  VAR("RedirectExit",        LINELIST, RedirectExit,         NULL),
  VAR("RephistTrackTime",    INTERVAL, RephistTrackTime,     "24 hours"),
  OBSOLETE("RouterFile"),
  VAR("RunAsDaemon",         BOOL,     RunAsDaemon,          "0"),
  VAR("RunTesting",          BOOL,     RunTesting,           "0"),
  VAR("RecommendedVersions", LINELIST, RecommendedVersions,  NULL),
  VAR("RendNodes",           STRING,   RendNodes,            NULL),
  VAR("RendExcludeNodes",    STRING,   RendExcludeNodes,     NULL),
  VAR("SafeLogging",         BOOL,     SafeLogging,          "1"),
  VAR("ShutdownWaitLength",  INTERVAL, ShutdownWaitLength,   "30 seconds"),
  VAR("SocksPort",           UINT,     SocksPort,            "9050"),
  VAR("SocksBindAddress",    LINELIST, SocksBindAddress,     NULL),
  VAR("SocksPolicy",         LINELIST, SocksPolicy,          NULL),
  /** DOCDOC */
  VAR("StatusFetchPeriod",   INTERVAL, StatusFetchPeriod,    "0 seconds"),
  VAR("SysLog",              LINELIST_S, OldLogOptions,      NULL),
  OBSOLETE("TrafficShaping"),
  VAR("User",                STRING,   User,                 NULL),
  VAR("UseHelperNodes",      BOOL,     UseHelperNodes,       "0"),
  VAR("NumHelperNodes",      UINT,     NumHelperNodes,       "3"),
  VAR("__LeaveStreamsUnattached", BOOL,LeaveStreamsUnattached, "0"),
  { NULL, CONFIG_TYPE_OBSOLETE, 0, NULL }
};
#undef VAR

#define VAR(name,conftype,member,initvalue) \
  { name, CONFIG_TYPE_ ## conftype, STRUCT_OFFSET(or_state_t, member), initvalue }
static config_var_t _state_vars[] = {
  VAR("LastWritten",             ISOTIME,     LastWritten,          NULL),

  VAR("AccountingIntervalStart", ISOTIME,  AccountingIntervalStart, NULL),
  VAR("AccountingBytesWrittenInInterval", MEMUNIT,
      AccountingBytesWrittenInInterval, NULL),
  VAR("AccountingBytesReadInterval", MEMUNIT, AccountingBytesReadInInterval,NULL),
  VAR("AccountingSecondsActive", INTERVAL,    AccountingSecondsActive, NULL),
  VAR("AccountingExpectedUsage", MEMUNIT,     AccountingExpectedUsage, NULL),

  VAR("HelperNodes",             LINELIST_V,  HelperNodes,          NULL),
  VAR("HelperNode",              LINELIST_S,  HelperNodes,          NULL),
  VAR("HelperNodeDownSince",     LINELIST_S,  HelperNodes,          NULL),
  VAR("HelperNodeUnlistedSince", LINELIST_S,  HelperNodes,          NULL),
  { NULL, CONFIG_TYPE_OBSOLETE, 0, NULL }
};

#undef VAR
#undef OBSOLETE

/** DOCDOC*/
typedef struct config_var_description_t {
  const char *name;
  const char *description;
} config_var_description_t;

static config_var_description_t options_description[] = {
  { "Address", "The advertised (external) address we should use." },
  // { "AccountingStart", ""},
  { NULL, NULL },
};

static config_var_description_t state_description[] = {
  { "HelperNode", "One of the nodes we have chosen as a fixed entry" },
  { "HelperNodeDownSince",
    "The last helper node has been down since this time." },
  { "HelperNodeUnlistedSince",
    "The last helper node has been unlisted since this time." },
  { NULL, NULL },
};

typedef int (*validate_fn_t)(void*);

typedef struct {
  size_t size;
  uint32_t magic;
  off_t magic_offset;
  config_abbrev_t *abbrevs;
  config_var_t *vars;
  validate_fn_t validate_fn;
  config_var_description_t *descriptions;
} config_format_t;

#define CHECK(fmt, cfg) do {                                            \
    tor_assert(fmt && cfg);                                             \
    tor_assert((fmt)->magic == *(uint32_t*)(((char*)(cfg))+fmt->magic_offset)); \
  } while (0)

/** Largest allowed config line */
#define CONFIG_LINE_T_MAXLEN 4096

static void config_line_append(config_line_t **lst,
                               const char *key, const char *val);
static void option_reset(config_format_t *fmt, or_options_t *options,
                         config_var_t *var);
static void config_free(config_format_t *fmt, void *options);
static int option_is_same(config_format_t *fmt,
                          or_options_t *o1, or_options_t *o2,const char *name);
static or_options_t *options_dup(config_format_t *fmt, or_options_t *old);
static int options_validate(or_options_t *options);
static int options_transition_allowed(or_options_t *old, or_options_t *new);
static int check_nickname_list(const char *lst, const char *name);
static void config_register_addressmaps(or_options_t *options);

static int parse_dir_server_line(const char *line, int validate_only);
static int parse_redirect_line(smartlist_t *result,
                               config_line_t *line);
static int parse_log_severity_range(const char *range, int *min_out,
                                    int *max_out);
static int convert_log_option(or_options_t *options,
                              config_line_t *level_opt,
                              config_line_t *file_opt, int isDaemon);
static int add_single_log_option(or_options_t *options, int minSeverity,
                                 int maxSeverity,
                                 const char *type, const char *fname);
static int normalize_log_options(or_options_t *options);
static int validate_data_directory(or_options_t *options);
static int write_configuration_file(const char *fname, or_options_t *options);
static config_line_t *get_assigned_option(config_format_t *fmt,
                                     or_options_t *options, const char *key);
static void config_init(config_format_t *fmt, void *options);
static int or_state_validate(or_state_t *options);

static uint64_t config_parse_memunit(const char *s, int *ok);
static int config_parse_interval(const char *s, int *ok);
static void print_cvs_version(void);
static int init_libevent(void);
#if defined(HAVE_EVENT_GET_VERSION) && defined(HAVE_EVENT_GET_METHOD)
static void check_libevent_version(const char *m, const char *v, int server);
#endif

#define OR_OPTIONS_MAGIC 9090909

static config_format_t options_format = {
  sizeof(or_options_t),
  OR_OPTIONS_MAGIC,
  STRUCT_OFFSET(or_options_t, _magic),
  _option_abbrevs,
  _option_vars,
  (validate_fn_t)options_validate,
  options_description
};

#define OR_STATE_MAGIC 0x57A73f57

static config_format_t state_format = {
  sizeof(or_state_t),
  OR_STATE_MAGIC,
  STRUCT_OFFSET(or_state_t, _magic),
  NULL,
  _state_vars,
  (validate_fn_t)or_state_validate,
  state_description
};

/*
 * Functions to read and write the global options pointer.
 */

/** Command-line and config-file options. */
static or_options_t *global_options = NULL;
/** Name of most recently read torrc file. */
static char *config_fname = NULL;
/** Persistant serialized state. */
static or_state_t *global_state = NULL;

static void *
config_alloc(config_format_t *fmt)
{
  void *opts = opts = tor_malloc_zero(fmt->size);
  *(uint32_t*)(((char*)opts)+fmt->magic_offset) = fmt->magic;
  CHECK(fmt, opts);
  return opts;
}

/** Return the currently configured options. */
or_options_t *
get_options(void)
{
  tor_assert(global_options);
  return global_options;
}

/** Change the current global options to contain <b>new_val</b> instead
 * of their current value; free the old value as necessary.
 */
void
set_options(or_options_t *new_val)
{
  if (global_options)
    config_free(&options_format, global_options);
  global_options = new_val;
}

void
config_free_all(void)
{
  config_free(&options_format, global_options);
  tor_free(config_fname);
}

/** If options->SafeLogging is on, return a not very useful string,
 * else return address.
 */
const char *
safe_str(const char *address)
{
  if (get_options()->SafeLogging)
    return "[scrubbed]";
  else
    return address;
}

/** Fetch the active option list, and take actions based on it. All
 * of the things we do should survive being done repeatedly.
 * Return 0 if all goes well, return -1 if it's time to die.
 *
 * Note 1: <b>new_val</b> must have previously been validated with
 * options_validate(), or Tor may freak out and exit.
 *
 * Note 2: We haven't moved all the "act on new configuration" logic
 * here yet.  Some is still in do_hup() and other places.
 */
int
options_act(void)
{
  config_line_t *cl;
  or_options_t *options = get_options();
  static int libevent_initialized = 0;

  if (options->RunAsDaemon) {
    start_daemon();
  }

  clear_trusted_dir_servers();
  for (cl = options->DirServers; cl; cl = cl->next) {
    if (parse_dir_server_line(cl->value, 0)<0) {
      log_fn(LOG_ERR,
             "Bug: Previously validated DirServer line could not be added!");
      return -1;
    }
  }

  if (rend_config_services(options, 0)<0) {
    log_fn(LOG_ERR,
           "Bug: Previously validated hidden services line could not be added!");
    return -1;
  }

  if (options->EntryNodes && strlen(options->EntryNodes))
    options->UseHelperNodes = 0;

  /* Setuid/setgid as appropriate */
  if (options->User || options->Group) {
    if (switch_id(options->User, options->Group) != 0) {
      return -1;
    }
  }

  /* Ensure data directory is private; create if possible. */
  if (check_private_dir(options->DataDirectory, CPD_CREATE) != 0) {
    log_fn(LOG_ERR, "Couldn't access/create private data directory %s",
           options->DataDirectory);
    return -1;
  }

  /* Bail out at this point if we're not going to be a server: we want
   * to not fork, and to log stuff to stderr. */
  if (options->command != CMD_RUN_TOR)
    return 0;

  mark_logs_temp(); /* Close current logs once new logs are open. */
  if (options_init_logs(options, 0)<0) /* Configure the log(s) */
    return -1;

  /* Close the temporary log we used while starting up, if it isn't already
   * gone. */
  close_temp_logs();
  add_callback_log(LOG_ERR, LOG_ERR, control_event_logmsg);
  control_adjust_event_log_severity();

  /* Set up libevent. */
  if (!libevent_initialized) {
    if (init_libevent())
      return -1;
    libevent_initialized = 1;
  }

  /* Load state */
  if (! global_state)
    if (or_state_load())
      return -1;

  options->_ConnLimit =
    set_max_file_descriptors((unsigned)options->ConnLimit, MAXCONNECTIONS);
  if (options->_ConnLimit < 0)
    return -1;

  {
    smartlist_t *sl = smartlist_create();
    for (cl = options->RedirectExit; cl; cl = cl->next) {
      if (parse_redirect_line(sl, cl)<0)
        return -1;
    }
    set_exit_redirects(sl);
  }

  /* Finish backgrounding the process */
  if (options->RunAsDaemon) {
    /* We may be calling this for the n'th time (on SIGHUP), but it's safe. */
    finish_daemon(options->DataDirectory);
  }

  /* Write our pid to the pid file. If we do not have write permissions we
   * will log a warning */
  if (options->PidFile)
    write_pidfile(options->PidFile);

  /* Register addressmap directives */
  config_register_addressmaps(options);

  /* Update address policies. */
  parse_socks_policy();
  parse_dir_policy();

  init_cookie_authentication(options->CookieAuthentication);

  /* reload keys as needed for rendezvous services. */
  if (rend_service_load_keys()<0) {
    log_fn(LOG_ERR,"Error loading rendezvous service keys");
    return -1;
  }

  /* Set up accounting */
  if (accounting_parse_options(options, 0)<0) {
    log_fn(LOG_ERR,"Error in accounting options");
    return -1;
  }
  if (accounting_is_enabled(options))
    configure_accounting(time(NULL));

  if (!we_are_hibernating() && retry_all_listeners(0) < 0) {
    log_fn(LOG_ERR,"Failed to bind one of the listener ports.");
    return -1;
  }

  /* Since our options changed, we might need to regenerate and upload our
   * server descriptor.  (We could probably be more clever about only calling
   * this when something significant changed.)
   */
  mark_my_descriptor_dirty();

  return 0;
}

/*
 * Functions to parse config options
 */

/** If <b>option</b> is an official abbreviation for a longer option,
 * return the longer option.  Otherwise return <b>option</b>.
 * If <b>command_line</b> is set, apply all abbreviations.  Otherwise, only
 * apply abbreviations that work for the config file and the command line. */
static const char *
expand_abbrev(config_format_t *fmt, const char *option, int command_line)
{
  int i;
  if (! fmt->abbrevs)
    return option;
  for (i=0; fmt->abbrevs[i].abbreviated; ++i) {
    /* Abbreviations aren't casei. */
    if (!strcasecmp(option,fmt->abbrevs[i].abbreviated) &&
        (command_line || !fmt->abbrevs[i].commandline_only)) {
      return fmt->abbrevs[i].full;
    }
  }
  return option;
}

/** Helper: Read a list of configuration options from the command line. */
static config_line_t *
config_get_commandlines(int argc, char **argv)
{
  config_line_t *front = NULL;
  config_line_t **new = &front;
  char *s;
  int i = 1;

  while (i < argc-1) {
    if (!strcmp(argv[i],"-f") ||
        !strcmp(argv[i],"--hash-password")) {
      i += 2; /* command-line option with argument. ignore them. */
      continue;
    } else if (!strcmp(argv[i],"--list-fingerprint")) {
      i += 1; /* command-line option. ignore it. */
      continue;
    } else if (!strcmp(argv[i],"--nt-service")) {
      i += 1;
      continue;
    }

    *new = tor_malloc_zero(sizeof(config_line_t));
    s = argv[i];

    while (*s == '-')
      s++;

    (*new)->key = tor_strdup(expand_abbrev(&options_format, s, 1));
    (*new)->value = tor_strdup(argv[i+1]);
    (*new)->next = NULL;
    log(LOG_DEBUG,"Commandline: parsed keyword '%s', value '%s'",
        (*new)->key, (*new)->value);

    new = &((*new)->next);
    i += 2;
  }
  return front;
}

/** Helper: allocate a new configuration option mapping 'key' to 'val',
 * append it to *<b>lst</b>. */
static void
config_line_append(config_line_t **lst,
                   const char *key,
                   const char *val)
{
  config_line_t *newline;

  newline = tor_malloc(sizeof(config_line_t));
  newline->key = tor_strdup(key);
  newline->value = tor_strdup(val);
  newline->next = NULL;
  while (*lst)
    lst = &((*lst)->next);

  (*lst) = newline;
}

/** Helper: parse the config string and strdup into key/value
 * strings. Set *result to the list, or NULL if parsing the string
 * failed.  Return 0 on success, -1 on failure. Warn and ignore any
 * misformatted lines. */
int
config_get_lines(char *string, config_line_t **result)
{
  config_line_t *list = NULL, **next;
  char *k, *v;

  next = &list;
  do {
    string = parse_line_from_str(string, &k, &v);
    if (!string) {
      config_free_lines(list);
      return -1;
    }
    if (k && v) {
      /* This list can get long, so we keep a pointer to the end of it
       * rather than using config_line_append over and over and getting n^2
       * performance.  This is the only really long list. */
      *next = tor_malloc(sizeof(config_line_t));
      (*next)->key = tor_strdup(k);
      (*next)->value = tor_strdup(v);
      (*next)->next = NULL;
      next = &((*next)->next);
    }
  } while (*string);

  *result = list;
  return 0;
}

/**
 * Free all the configuration lines on the linked list <b>front</b>.
 */
void
config_free_lines(config_line_t *front)
{
  config_line_t *tmp;

  while (front) {
    tmp = front;
    front = tmp->next;

    tor_free(tmp->key);
    tor_free(tmp->value);
    tor_free(tmp);
  }
}

/** DOCDOC */
static const char *
config_find_description(config_format_t *fmt, const char *name)
{
  int i;
  for (i=0; fmt->descriptions[i].name; ++i) {
    if (!strcasecmp(name, fmt->descriptions[i].name))
      return fmt->descriptions[i].description;
  }
  return NULL;
}

/** If <b>key</b> is a configuration option, return the corresponding
 * config_var_t.  Otherwise, if <b>key</b> is a non-standard abbreviation,
 * warn, and return the corresponding config_var_t.  Otherwise return NULL.
 */
static config_var_t *
config_find_option(config_format_t *fmt, const char *key)
{
  int i;
  size_t keylen = strlen(key);
  if (!keylen)
    return NULL; /* if they say "--" on the commandline, it's not an option */
  /* First, check for an exact (case-insensitive) match */
  for (i=0; fmt->vars[i].name; ++i) {
    if (!strcasecmp(key, fmt->vars[i].name)) {
      return &fmt->vars[i];
    }
  }
  /* If none, check for an abbreviated match */
  for (i=0; fmt->vars[i].name; ++i) {
    if (!strncasecmp(key, fmt->vars[i].name, keylen)) {
      log_fn(LOG_WARN, "The abbreviation '%s' is deprecated. "
          "Please use '%s' instead",
             key, fmt->vars[i].name);
      return &fmt->vars[i];
    }
  }
  /* Okay, unrecognized options */
  return NULL;
}

/** If <b>c</b> is a syntactically valid configuration line, update
 * <b>options</b> with its value and return 0.  Otherwise return -1 for bad key,
 * -2 for bad value.
 *
 * If 'reset' is set, and we get a line containing no value, restore the
 * option to its default value.
 */
static int
config_assign_line(config_format_t *fmt,
                   or_options_t *options, config_line_t *c, int reset)
{
  int i, ok;
  config_var_t *var;
  void *lvalue;

  CHECK(fmt, options);

  var = config_find_option(fmt, c->key);
  if (!var) {
    log_fn(LOG_WARN, "Unknown option '%s'.  Failing.", c->key);
    return -1;
  }
  /* Put keyword into canonical case. */
  if (strcmp(var->name, c->key)) {
    tor_free(c->key);
    c->key = tor_strdup(var->name);
  }

  if (reset && !strlen(c->value)) {
    option_reset(fmt, options, var);
    return 0;
  }

  lvalue = ((char*)options) + var->var_offset;
  switch (var->type) {

  case CONFIG_TYPE_UINT:
    i = tor_parse_long(c->value, 10, 0, INT_MAX, &ok, NULL);
    if (!ok) {
      log(LOG_WARN, "Int keyword '%s %s' is malformed or out of bounds.",
          c->key,c->value);
      return -2;
    }
    *(int *)lvalue = i;
    break;

  case CONFIG_TYPE_INTERVAL: {
    i = config_parse_interval(c->value, &ok);
    if (!ok) {
      return -2;
    }
    *(int *)lvalue = i;
    break;
  }

  case CONFIG_TYPE_MEMUNIT: {
    uint64_t u64 = config_parse_memunit(c->value, &ok);
    if (!ok) {
      return -2;
    }
    *(uint64_t *)lvalue = u64;
    break;
  }

  case CONFIG_TYPE_BOOL:
    i = tor_parse_long(c->value, 10, 0, 1, &ok, NULL);
    if (!ok) {
      log(LOG_WARN, "Boolean keyword '%s' expects 0 or 1.", c->key);
      return -2;
    }
    *(int *)lvalue = i;
    break;

  case CONFIG_TYPE_STRING:
    tor_free(*(char **)lvalue);
    *(char **)lvalue = tor_strdup(c->value);
    break;

  case CONFIG_TYPE_DOUBLE:
    *(double *)lvalue = atof(c->value);
    break;

  case CONFIG_TYPE_ISOTIME:
    if (parse_iso_time(c->value, (time_t *)lvalue)) {
      log(LOG_WARN, "Invalid time '%s' for keyword '%s'", c->value, c->key);
      return -2;
    }
    break;

  case CONFIG_TYPE_CSV:
    if (*(smartlist_t**)lvalue) {
      SMARTLIST_FOREACH(*(smartlist_t**)lvalue, char *, cp, tor_free(cp));
      smartlist_clear(*(smartlist_t**)lvalue);
    } else {
      *(smartlist_t**)lvalue = smartlist_create();
    }

    smartlist_split_string(*(smartlist_t**)lvalue, c->value, ",",
                           SPLIT_SKIP_SPACE|SPLIT_IGNORE_BLANK, 0);
    break;

  case CONFIG_TYPE_LINELIST:
  case CONFIG_TYPE_LINELIST_S:
    config_line_append((config_line_t**)lvalue, c->key, c->value);
    break;

  case CONFIG_TYPE_OBSOLETE:
    log_fn(LOG_WARN, "Skipping obsolete configuration option '%s'", c->key);
    break;
  case CONFIG_TYPE_LINELIST_V:
    log_fn(LOG_WARN, "Can't provide value for virtual option '%s'", c->key);
    return -2;
  default:
    tor_assert(0);
    break;
  }
  return 0;
}

/** restore the option named <b>key</b> in options to its default value. */
static void
config_reset_line(config_format_t *fmt, or_options_t *options, const char *key)
{
  config_var_t *var;

  CHECK(fmt, options);

  var = config_find_option(fmt, key);
  if (!var)
    return; /* give error on next pass. */

  option_reset(fmt, options, var);
}

/** Return true iff key is a valid configuration option. */
int
option_is_recognized(const char *key)
{
  config_var_t *var = config_find_option(&options_format, key);
  return (var != NULL);
}

/** Return the canonical name of a configuration option. */
const char *
option_get_canonical_name(const char *key)
{
  config_var_t *var = config_find_option(&options_format, key);
  return var->name;
}

/** Return a canonicalized list of the options assigned for key.
 */
config_line_t *
option_get_assignment(or_options_t *options, const char *key)
{
  return get_assigned_option(&options_format, options, key);
}

static config_line_t *
get_assigned_option(config_format_t *fmt, or_options_t *options, const char *key)
{
  config_var_t *var;
  const void *value;
  char buf[32];
  config_line_t *result;
  tor_assert(options && key);

  CHECK(fmt, options);

  var = config_find_option(fmt, key);
  if (!var) {
    log_fn(LOG_WARN, "Unknown option '%s'.  Failing.", key);
    return NULL;
  } else if (var->type == CONFIG_TYPE_LINELIST_S) {
    log_fn(LOG_WARN, "Can't return context-sensitive '%s' on its own", key);
    return NULL;
  }
  value = ((char*)options) + var->var_offset;

  if (var->type == CONFIG_TYPE_LINELIST ||
      var->type == CONFIG_TYPE_LINELIST_V) {
    /* Linelist requires special handling: we just copy and return it. */
    const config_line_t *next_in = *(const config_line_t**)value;
    config_line_t **next_out = &result;
    while (next_in) {
      *next_out = tor_malloc(sizeof(config_line_t));
      (*next_out)->key = tor_strdup(next_in->key);
      (*next_out)->value = tor_strdup(next_in->value);
      next_in = next_in->next;
      next_out = &((*next_out)->next);
    }
    (*next_out) = NULL;
    return result;
  }

  result = tor_malloc_zero(sizeof(config_line_t));
  result->key = tor_strdup(var->name);
  switch (var->type)
    {
    case CONFIG_TYPE_STRING:
      if (*(char**)value) {
        result->value = tor_strdup(*(char**)value);
      } else {