/* engine-gpgconf.c - gpg-conf engine.
 * Copyright (C) 2000 Werner Koch (dd9jn)
 * Copyright (C) 2001, 2002, 2003, 2004, 2005, 2007, 2008,
 *               2013 g10 Code GmbH
 *
 * This file is part of GPGME.
 *
 * GPGME is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * GPGME is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, see <https://gnu.org/licenses/>.
 * SPDX-License-Identifier: LGPL-2.1-or-later
 */

#if HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdlib.h>
#include <string.h>
#ifdef HAVE_SYS_TYPES_H
# include <sys/types.h>
#endif
#include <assert.h>
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif
#include <fcntl.h> /* FIXME */
#include <errno.h>

#include "gpgme.h"
#include "util.h"
#include "ops.h"
#include "wait.h"
#include "priv-io.h"
#include "sema.h"

#include "assuan.h"
#include "debug.h"

#include "engine-backend.h"



struct engine_gpgconf
{
  char *file_name;
  char *home_dir;
  char *version;
};

typedef struct engine_gpgconf *engine_gpgconf_t;


/* Return true if the engine's version is at least VERSION.  */
static int
have_gpgconf_version (engine_gpgconf_t gpgconf, const char *version)
{
  return _gpgme_compare_versions (gpgconf->version, version);
}


static char *
gpgconf_get_version (const char *file_name)
{
  return _gpgme_get_program_version (file_name ? file_name
				     : _gpgme_get_default_gpgconf_name ());
}


static const char *
gpgconf_get_req_version (void)
{
  return "2.0.4";
}


static void
gpgconf_release (void *engine)
{
  engine_gpgconf_t gpgconf = engine;

  if (!gpgconf)
    return;

  if (gpgconf->file_name)
    free (gpgconf->file_name);
  if (gpgconf->home_dir)
    free (gpgconf->home_dir);
  if (gpgconf->version)
    free (gpgconf->version);

  free (gpgconf);
}


static gpgme_error_t
gpgconf_new (void **engine, const char *file_name, const char *home_dir,
             const char *version)
{
  gpgme_error_t err = 0;
  engine_gpgconf_t gpgconf;

  gpgconf = calloc (1, sizeof *gpgconf);
  if (!gpgconf)
    return gpg_error_from_syserror ();

  gpgconf->file_name = strdup (file_name ? file_name
			       : _gpgme_get_default_gpgconf_name ());
  if (!gpgconf->file_name)
    err = gpg_error_from_syserror ();

  if (!err && home_dir)
    {
      gpgconf->home_dir = strdup (home_dir);
      if (!gpgconf->home_dir)
	err = gpg_error_from_syserror ();
    }

  if (!err && version)
    {
      gpgconf->version = strdup (version);
      if (!gpgconf->version)
        err = gpg_error_from_syserror ();
    }

  if (err)
    gpgconf_release (gpgconf);
  else
    *engine = gpgconf;

  return err;
}


static void
release_arg (gpgme_conf_arg_t arg, gpgme_conf_type_t alt_type)
{
  while (arg)
    {
      gpgme_conf_arg_t next = arg->next;

      if (alt_type == GPGME_CONF_STRING)
	free (arg->value.string);
      free (arg);
      arg = next;
    }
}


static void
release_opt (gpgme_conf_opt_t opt)
{
  if (opt->name)
    free (opt->name);
  if (opt->description)
    free (opt->description);
  if (opt->argname)
    free (opt->argname);

  release_arg (opt->default_value, opt->alt_type);
  if (opt->default_description)
    free (opt->default_description);

  release_arg (opt->no_arg_value, opt->alt_type);
  release_arg (opt->value, opt->alt_type);
  release_arg (opt->new_value, opt->alt_type);

  free (opt);
}


static void
release_comp (gpgme_conf_comp_t comp)
{
  gpgme_conf_opt_t opt;

  if (comp->name)
    free (comp->name);
  if (comp->description)
    free (comp->description);
  if (comp->program_name)
    free (comp->program_name);

  opt = comp->options;
  while (opt)
    {
      gpgme_conf_opt_t next = opt->next;
      release_opt (opt);
      opt = next;
    }

  free (comp);
}


static void
gpgconf_config_release (gpgme_conf_comp_t conf)
{
  while (conf)
    {
      gpgme_conf_comp_t next = conf->next;
      release_comp (conf);
      conf = next;
    }
}

/* Read from gpgconf and pass line after line to the hook function.
   We put a limit of 64 k on the maximum size for a line.  This should
   allow for quite a long "group" line, which is usually the longest
   line (mine is currently ~3k).  */
static gpgme_error_t
gpgconf_read (void *engine, const char *arg1, char *arg2,
	      gpgme_error_t (*cb) (void *hook, char *line),
	      void *hook)
{
  struct engine_gpgconf *gpgconf = engine;
  gpgme_error_t err = 0;
  char *linebuf;
  size_t linebufsize;
  int linelen;
  char *argv[6];
  int argc = 0;
  int rp[2];
  struct spawn_fd_item_s cfd[] = { {-1, 1 /* STDOUT_FILENO */, -1, 0},
				   {-1, -1} };
  int status;
  int nread;
  char *mark = NULL;

  /* _gpgme_engine_new guarantees that this is not NULL.  */
  argv[argc++] = gpgconf->file_name;

  if (gpgconf->home_dir && have_gpgconf_version (gpgconf, "2.1.13"))
    {
      argv[argc++] = (char*)"--homedir";
      argv[argc++] = gpgconf->home_dir;
    }

  argv[argc++] = (char*)arg1;
  argv[argc++] = arg2;
  argv[argc] = NULL;
  assert (argc < DIM (argv));

  if (_gpgme_io_pipe (rp, 1) < 0)
    return gpg_error_from_syserror ();

  cfd[0].fd = rp[1];

  status = _gpgme_io_spawn (gpgconf->file_name, argv,
                            IOSPAWN_FLAG_DETACHED, cfd, NULL, NULL, NULL);
  if (status < 0)
    {
      _gpgme_io_close (rp[0]);
      _gpgme_io_close (rp[1]);
      return gpg_error_from_syserror ();
    }

  linebufsize = 1024; /* Usually enough for conf lines.  */
  linebuf = malloc (linebufsize);
  if (!linebuf)
    {
      err = gpg_error_from_syserror ();
      goto leave;
    }
  linelen = 0;

  while ((nread = _gpgme_io_read (rp[0], linebuf + linelen,
                                  linebufsize - linelen - 1)))
    {
      char *line;
      const char *lastmark = NULL;
      size_t nused;

      if (nread < 0)
        {
          err = gpg_error_from_syserror ();
          goto leave;
        }

      linelen += nread;
      linebuf[linelen] = '\0';

      for (line=linebuf; (mark = strchr (line, '\n')); line = mark+1 )
        {
          lastmark = mark;
          if (mark > line && mark[-1] == '\r')
            mark[-1] = '\0';
          else
            mark[0] = '\0';

          /* Got a full line.  Due to the CR removal code (which
             occurs only on Windows) we might be one-off and thus
             would see empty lines.  Don't pass them to the
             callback. */
          err = *line? (*cb) (hook, line) : 0;
          if (err)
            goto leave;
        }

      nused = lastmark? (lastmark + 1 - linebuf) : 0;
      memmove (linebuf, linebuf + nused, linelen - nused);
      linelen -= nused;

      if (!(linelen < linebufsize - 1))
        {
          char *newlinebuf;

          if (linelen <  8 * 1024 - 1)
            linebufsize = 8 * 1024;
          else if (linelen < 64 * 1024 - 1)
            linebufsize = 64 * 1024;
          else
            {
              /* We reached our limit - give up.  */
              err = gpg_error (GPG_ERR_LINE_TOO_LONG);
              goto leave;
            }

          newlinebuf = realloc (linebuf, linebufsize);
          if (!newlinebuf)
            {
              err = gpg_error_from_syserror ();
              goto leave;
            }
          linebuf = newlinebuf;
        }
    }

 leave:
  free (linebuf);
  _gpgme_io_close (rp[0]);
  return err;
}


static gpgme_error_t
gpgconf_config_load_cb (void *hook, char *line)
{
  gpgme_conf_comp_t *comp_p = hook;
  gpgme_conf_comp_t comp = *comp_p;
#define NR_FIELDS 16
  char *field[NR_FIELDS];
  int fields = 0;

  while (line && fields < NR_FIELDS)
    {
      field[fields++] = line;
      line = strchr (line, ':');
      if (line)
	*(line++) = '\0';
    }

  /* We require at least the first 3 fields.  */
  if (fields < 2)
    return trace_gpg_error (GPG_ERR_INV_ENGINE);

  /* Find the pointer to the new component in the list.  */
  while (comp && comp->next)
    comp = comp->next;
  if (comp)
    comp_p = &comp->next;

  comp = calloc (1, sizeof (*comp));
  if (!comp)
    return gpg_error_from_syserror ();
  /* Prepare return value.  */
  comp->_last_opt_p = &comp->options;
  *comp_p = comp;

  comp->name = strdup (field[0]);
  if (!comp->name)
    return gpg_error_from_syserror ();

  comp->description = strdup (field[1]);
  if (!comp->description)
    return gpg_error_from_syserror ();

  if (fields >= 3)
    {
      comp->program_name = strdup (field[2]);
      if (!comp->program_name)
	return gpg_error_from_syserror ();
    }

  return 0;
}


static gpgme_error_t
gpgconf_parse_option (gpgme_conf_opt_t opt,
		      gpgme_conf_arg_t *arg_p, char *line)
{
  gpgme_error_t err;
  char *mark = NULL;

  if (!line[0])
    return 0;

  while (line)
    {
      gpgme_conf_arg_t arg;

      if (opt->type != GPGME_CONF_STRING)
        mark = strchr (line, ',');
      if (mark)
	*mark = '\0';

      arg = calloc (1, sizeof (*arg));
      if (!arg)
	return gpg_error_from_syserror ();
      *arg_p = arg;
      arg_p = &arg->next;

      if (*line == '\0')
	arg->no_arg = 1;
      else
	{
	  switch (opt->alt_type)
	    {
	      /* arg->value.count is an alias for arg->value.uint32.  */
	    case GPGME_CONF_NONE:
	    case GPGME_CONF_UINT32:
	      arg->value.uint32 = strtoul (line, NULL, 0);
	      break;

	    case GPGME_CONF_INT32:
	      arg->value.uint32 = strtol (line, NULL, 0);
	      break;

	    case GPGME_CONF_STRING:
              /* The complex types below are only here to silent the
                 compiler warning. */
            case GPGME_CONF_FILENAME:
            case GPGME_CONF_LDAP_SERVER:
            case GPGME_CONF_KEY_FPR:
            case GPGME_CONF_PUB_KEY:
            case GPGME_CONF_SEC_KEY:
            case GPGME_CONF_ALIAS_LIST:
	      /* Skip quote character.  It is required by specs but
               * technically not always needed.  */
              if (*line == '\"' && line[1])
                line++;

	      err = _gpgme_decode_percent_string (line, &arg->value.string,
						  0, 0);
	      if (err)
		return err;
	      break;
	    }
	}

      /* Find beginning of next value.  */
      if (mark++ && *mark)
	line = mark;
      else
	line = NULL;
    }

  return 0;
}


static gpgme_error_t
gpgconf_config_load_cb2 (void *hook, char *line)
{
  gpgme_error_t err;
  gpgme_conf_comp_t comp = hook;
  gpgme_conf_opt_t *opt_p = comp->_last_opt_p;
  gpgme_conf_opt_t opt;
#define NR_FIELDS 16
  char *field[NR_FIELDS];
  int fields = 0;

  while (line && fields < NR_FIELDS)
    {
      field[fields++] = line;
      line = strchr (line, ':');
      if (line)
	*(line++) = '\0';
    }

  /* We require at least the first 10 fields.  */
  if (fields < 10)
    return trace_gpg_error (GPG_ERR_INV_ENGINE);

  opt = calloc (1, sizeof (*opt));
  if (!opt)
    return gpg_error_from_syserror ();

  comp->_last_opt_p = &opt->next;
  *opt_p = opt;

  if (field[0][0])
    {
      opt->name = strdup (field[0]);
      if (!opt->name)
	return gpg_error_from_syserror ();
    }

  opt->flags = strtoul (field[1], NULL, 0);

  opt->level = strtoul (field[2], NULL, 0);

  if (field[3][0])
    {
      opt->description = strdup (field[3]);
      if (!opt->description)
	return gpg_error_from_syserror ();
    }

  opt->type = strtoul (field[4], NULL, 0);

  opt->alt_type = strtoul (field[5], NULL, 0);

  if (field[6][0])
    {
      opt->argname = strdup (field[6]);
      if (!opt->argname)
	return gpg_error_from_syserror ();
    }

  if (opt->flags & GPGME_CONF_DEFAULT)
    {
      err = gpgconf_parse_option (opt, &opt->default_value, field[7]);
      if (err)
	return err;
    }
  else if ((opt->flags & GPGME_CONF_DEFAULT_DESC) && field[7][0])
    {
      opt->default_description = strdup (field[7]);
      if (!opt->default_description)
	return gpg_error_from_syserror ();
    }

  if (opt->flags & GPGME_CONF_NO_ARG_DESC)
    {
      opt->no_arg_description = strdup (field[8]);
      if (!opt->no_arg_description)
	return gpg_error_from_syserror ();
    }
  else
    {
      err = gpgconf_parse_option (opt, &opt->no_arg_value, field[8]);
      if (err)
	return err;
    }

  err = gpgconf_parse_option (opt, &opt->value, field[9]);
  if (err)
    return err;

  return 0;
}


static gpgme_error_t
gpgconf_conf_load (void *engine, gpgme_conf_comp_t *comp_p)
{
  gpgme_error_t err;
  gpgme_conf_comp_t comp = NULL;
  gpgme_conf_comp_t cur_comp;

  *comp_p = NULL;

  err = gpgconf_read (engine, "--list-components", NULL,
		      gpgconf_config_load_cb, &comp);
  if (err)
    {
      gpgconf_release (comp);
      return err;
    }

  cur_comp = comp;
  while (!err && cur_comp)
    {
      err = gpgconf_read (engine, "--list-options", cur_comp->name,
			  gpgconf_config_load_cb2, cur_comp);
      cur_comp = cur_comp->next;
    }

  if (err)
    {
      gpgconf_release (comp);
      return err;
    }

  *comp_p = comp;
  return 0;
}



gpgme_error_t
_gpgme_conf_arg_new (gpgme_conf_arg_t *arg_p,
		     gpgme_conf_type_t type, const void *value)
{
  gpgme_conf_arg_t arg;

  arg = calloc (1, sizeof (*arg));
  if (!arg)
    return gpg_error_from_syserror ();

  if (!value)
    arg->no_arg = 1;
  else
    {
      /* We need to switch on type here because the alt-type is not
         yet known.  */
      switch (type)
	{
	case GPGME_CONF_NONE:
	case GPGME_CONF_UINT32:
	  arg->value.uint32 = *((unsigned int *) value);
	  break;

	case GPGME_CONF_INT32:
	  arg->value.int32 = *((int *) value);
	  break;

	case GPGME_CONF_STRING:
	case GPGME_CONF_FILENAME:
	case GPGME_CONF_LDAP_SERVER:
        case GPGME_CONF_KEY_FPR:
        case GPGME_CONF_PUB_KEY:
        case GPGME_CONF_SEC_KEY:
        case GPGME_CONF_ALIAS_LIST:
	  arg->value.string = strdup (value);
	  if (!arg->value.string)
	    {
	      free (arg);
	      return gpg_error_from_syserror ();
	    }
	  break;

	default:
	  free (arg);
	  return gpg_error (GPG_ERR_INV_VALUE);
	}
    }

  *arg_p = arg;
  return 0;
}


void
_gpgme_conf_arg_release (gpgme_conf_arg_t arg, gpgme_conf_type_t type)
{
  /* Lacking the alt_type we need to switch on type here.  */
  switch (type)
    {
    case GPGME_CONF_NONE:
    case GPGME_CONF_UINT32:
    case GPGME_CONF_INT32:
    case GPGME_CONF_STRING:
    default:
      break;

    case GPGME_CONF_FILENAME:
    case GPGME_CONF_LDAP_SERVER:
    case GPGME_CONF_KEY_FPR:
    case GPGME_CONF_PUB_KEY:
    case GPGME_CONF_SEC_KEY:
    case GPGME_CONF_ALIAS_LIST:
      type = GPGME_CONF_STRING;
      break;
    }

  release_arg (arg, type);
}


gpgme_error_t
_gpgme_conf_opt_change (gpgme_conf_opt_t opt, int reset, gpgme_conf_arg_t arg)
{
  if (reset)
    {
      if (opt->new_value)
	release_arg (opt->new_value, opt->alt_type);
      opt->new_value = NULL;
      opt->change_value = 0;
    }
  else
    {
      /* Support self-assignment, for example for adding an item to an
	 existing list.  */
      if (opt->new_value && arg != opt->new_value)
	release_arg (opt->new_value, opt->alt_type);
      opt->new_value = arg;
      opt->change_value = 1;
    }
  return 0;
}


/* FIXME: Major problem: We don't get errors from gpgconf.  */

static gpgme_error_t
gpgconf_write (void *engine, const char *arg1, char *arg2, gpgme_data_t conf)
{
  struct engine_gpgconf *gpgconf = engine;
  gpgme_error_t err = 0;
#define BUFLEN 1024
  char buf[BUFLEN];
  int buflen = 0;
  char *argv[7];
  int argc = 0;
  int rp[2] = { -1, -1 };
  int errp[2] = { -1, -1 };
  struct spawn_fd_item_s cfd[] = { {-1, 0 /* STDIN_FILENO */},
                                   {-1, 2 /* STDERR_FILENO */, -1},
                                   {-1, -1} };
  int status;
  int nwrite;

  /* _gpgme_engine_new guarantees that this is not NULL.  */
  argv[argc++] = gpgconf->file_name;

  if (gpgconf->home_dir && have_gpgconf_version (gpgconf, "2.1.13"))
    {
      argv[argc++] = (char*)"--homedir";
      argv[argc++] = gpgconf->home_dir;
    }

  argv[argc++] = (char*)"--runtime";
  argv[argc++] = (char*)arg1;
  argv[argc++] = arg2;
  argv[argc] = NULL;
  assert (argc < DIM (argv));

  if (_gpgme_io_pipe (rp, 0) < 0)
    {
      err = gpg_error_from_syserror ();
      goto leave;
    }

  if (_gpgme_io_pipe (errp, 1) < 0)
    {
      err = gpg_error_from_syserror ();
      goto leave;
    }

  cfd[0].fd = rp[0];
  cfd[1].fd = errp[1];

  status = _gpgme_io_spawn (gpgconf->file_name, argv,
                            IOSPAWN_FLAG_DETACHED, cfd, NULL, NULL, NULL);
  if (status < 0)
    {
      err = gpg_error_from_syserror ();
      goto leave;
    }

  rp[0] = -1;
  errp[1] = -1;

  for (;;)
    {
      if (buflen == 0)
	{
	  do
	    {
	      buflen = gpgme_data_read (conf, buf, BUFLEN);
	    }
	  while (buflen < 0 && errno == EAGAIN);

	  if (buflen < 0)
	    {
	      err = gpg_error_from_syserror ();
              goto leave;
	    }
	  else if (buflen == 0)
	    {
	      /* All is written.  */
	      _gpgme_io_close (rp[1]);
              rp[1] = -1;

              for (;;)
                {
                  do
                    {
                      buflen = _gpgme_io_read (errp[0], buf, BUFLEN);
                    }
                  while (buflen < 0 && errno == EAGAIN);

                  if (buflen == 0)
                    {
                      err = 0;
                      goto leave;
                    }
                  /* XXX: Do something useful with BUF.  */
                }
	    }
	}

      do
	{
	  nwrite = _gpgme_io_write (rp[1], buf, buflen);
	}
      while (nwrite < 0 && errno == EAGAIN);

      if (nwrite > 0)
	{
	  buflen -= nwrite;
	  if (buflen > 0)
	    memmove (&buf[0], &buf[nwrite], buflen);
	}
      else if (nwrite < 0)
	{
	  err = gpg_error_from_syserror ();
          goto leave;
	}
    }

  assert (! "reached");

 leave:
  if (rp[0] != -1)
    _gpgme_io_close (rp[0]);
  if (rp[1] != -1)
  _gpgme_io_close (rp[1]);
  if (errp[0] != -1)
    _gpgme_io_close (errp[0]);
  if (errp[1] != -1)
  _gpgme_io_close (errp[1]);

  return err;
}


static gpgme_error_t
arg_to_data (gpgme_data_t conf, gpgme_conf_opt_t option, gpgme_conf_arg_t arg)
{
  gpgme_error_t err = 0;
  int amt = 0;
  char buf[16];

  while (amt >= 0 && arg)
    {
      switch (option->alt_type)
	{
	case GPGME_CONF_NONE:
	case GPGME_CONF_UINT32:
	default:
	  snprintf (buf, sizeof (buf), "%u", arg->value.uint32);
	  buf[sizeof (buf) - 1] = '\0';
	  amt = gpgme_data_write (conf, buf, strlen (buf));
	  break;

	case GPGME_CONF_INT32:
	  snprintf (buf, sizeof (buf), "%i", arg->value.uint32);
	  buf[sizeof (buf) - 1] = '\0';
	  amt = gpgme_data_write (conf, buf, strlen (buf));
	  break;


	case GPGME_CONF_STRING:
          /* The complex types below are only here to silent the
             compiler warning. */
        case GPGME_CONF_FILENAME:
        case GPGME_CONF_LDAP_SERVER:
        case GPGME_CONF_KEY_FPR:
        case GPGME_CONF_PUB_KEY:
        case GPGME_CONF_SEC_KEY:
        case GPGME_CONF_ALIAS_LIST:
          if (arg->value.string)
            {
              /* One quote character, and three times to allow for
                 percent escaping.  */
              char *ptr = arg->value.string;
              amt = gpgme_data_write (conf, "\"", 1);
              if (amt < 0)
                break;

              while (!err && *ptr)
                {
                  switch (*ptr)
                    {
                    case '%':
                      amt = gpgme_data_write (conf, "%25", 3);
                      break;

                    case ':':
                      amt = gpgme_data_write (conf, "%3a", 3);
                      break;

                    case ',':
                      amt = gpgme_data_write (conf, "%2c", 3);
                      break;

                    default:
                      amt = gpgme_data_write (conf, ptr, 1);
                    }
                  ptr++;
                }
            }
	  break;
	}

      if (amt < 0)
	break;

      arg = arg->next;
      /* Comma separator.  */
      if (arg)
	amt = gpgme_data_write (conf, ",", 1);
    }

  if (amt < 0)
    return gpg_error_from_syserror ();

  return 0;
}


static gpgme_error_t
gpgconf_conf_save (void *engine, gpgme_conf_comp_t comp)
{
  gpgme_error_t err;
  int amt = 0;
  /* We use a data object to store the new configuration.  */
  gpgme_data_t conf;
  gpgme_conf_opt_t option;
  int something_changed = 0;

  err = gpgme_data_new (&conf);
  if (err)
    return err;

  option = comp->options;
  while (!err && amt >= 0 && option)
    {
      if (option->change_value)
	{
	  unsigned int flags = 0;
	  char buf[16];

	  something_changed = 1;

	  amt = gpgme_data_write (conf, option->name, strlen (option->name));
	  if (amt >= 0)
	    amt = gpgme_data_write (conf, ":", 1);
	  if (amt < 0)
	    break;

	  if (!option->new_value)
	    flags |= GPGME_CONF_DEFAULT;
	  snprintf (buf, sizeof (buf), "%u", flags);
	  buf[sizeof (buf) - 1] = '\0';

	  amt = gpgme_data_write (conf, buf, strlen (buf));
	  if (amt >= 0)
	    amt = gpgme_data_write (conf, ":", 1);
	  if (amt < 0)
	    break;

	  if (option->new_value)
	    {
	      err = arg_to_data (conf, option, option->new_value);
	      if (err)
		break;
	    }
	  amt = gpgme_data_write (conf, "\n", 1);
	}
      option = option->next;
    }
  if (!err && amt < 0)
    err = gpg_error_from_syserror ();
  if (err || !something_changed)
    goto bail;

  err = gpgme_data_seek (conf, 0, SEEK_SET);
  if (err)
    goto bail;

  err = gpgconf_write (engine, "--change-options", comp->name, conf);
 bail:
  gpgme_data_release (conf);
  return err;
}


struct gpgconf_config_dir_s
{
  const char *what;
  char *result;
};

/* Called for each line in the gpgconf --list-dirs output.  Searches
   for the desired line and returns the result, indicating success by
   a special error value GPG_ERR_USER_1 (which terminates the
   operation immediately).  */
static gpgme_error_t
gpgconf_config_dir_cb (void *hook, char *line)
{
  /* This is an input- and output-parameter.  */
  struct gpgconf_config_dir_s *data = (struct gpgconf_config_dir_s *) hook;
  int len = strlen(data->what);

  if (!strncmp(line, data->what, len) && line[len] == ':')
    {
      char *result = strdup(&line[len + 1]);
      if (!result)
	return gpg_error_from_syserror ();
      data->result = result;
      return gpg_error(GPG_ERR_USER_1);
    }
  return 0;
}


/* Like gpgme_get_dirinfo, but uses the home directory of ENGINE and
   does not cache the result.  */
static gpgme_error_t
gpgconf_conf_dir (void *engine, const char *what, char **result)
{
  gpgme_error_t err;
  struct gpgconf_config_dir_s data;

  data.what = what;
  data.result = NULL;
  err = gpgconf_read (engine, "--list-dirs", NULL,
		      gpgconf_config_dir_cb, &data);
  if (gpg_err_code (err) == GPG_ERR_USER_1)
    {
      /* This signals to us that a result was found.  */
      *result = data.result;
      return 0;
    }

  if (!err)
    err = gpg_error(GPG_ERR_NOT_FOUND);
  return 0;
}


/* Parse a line received from gpgconf --query-swdb.  This function may
 * modify LINE.  The result is stored at RESULT.  */
static gpg_error_t
parse_swdb_line (char *line, gpgme_query_swdb_result_t result)
{
  char *field[9];
  int fields = 0;
  gpg_err_code_t ec;

  while (line && fields < DIM (field))
    {
      field[fields++] = line;
      line = strchr (line, ':');
      if (line)
	*line++ = 0;
    }
  /* We require that all fields exists - gpgme emits all these fields
   * even on error.  They might be empty, though. */
  if (fields < 9)
    return gpg_error (GPG_ERR_INV_ENGINE);

  free (result->name);
  result->name = strdup (field[0]);
  if (!result->name)
    return gpg_error_from_syserror ();

  free (result->iversion);
  result->iversion = strdup (field[1]);
  if (!result->iversion)
    return gpg_error_from_syserror ();

  result->urgent = (strtol (field[3], NULL, 10) > 0);

  ec = gpg_err_code (strtoul (field[4], NULL, 10));

  result->created  = _gpgme_parse_timestamp (field[5], NULL);
  result->retrieved= _gpgme_parse_timestamp (field[6], NULL);

  free (result->version);
  result->version  = strdup (field[7]);
  if (!result->version)
    return gpg_error_from_syserror ();

  result->reldate  = _gpgme_parse_timestamp (field[8], NULL);

  /* Set other flags.  */
  result->warning = !!ec;
  result->update = 0;
  result->noinfo = 0;
  result->unknown = 0;
  result->tooold = 0;
  result->error = 0;

  switch (*field[2])
    {
    case '-': result->warning = 1; break;
    case '?': result->unknown = result->warning = 1; break;
    case 'u': result->update = 1; break;
    case 'c': break;
    case 'n': break;
    default:
      result->warning = 1;
      if (!ec)
        ec = GPG_ERR_INV_ENGINE;
      break;
    }

  if (ec == GPG_ERR_TOO_OLD)
    result->tooold = 1;
  else if (ec == GPG_ERR_ENOENT)
    result->noinfo = 1;
  else if (ec)
    result->error = 1;


  return 0;
}


static gpgme_error_t
gpgconf_query_swdb (void *engine,
                    const char *name, const char *iversion,
                    gpgme_query_swdb_result_t result)
{
  struct engine_gpgconf *gpgconf = engine;
  gpgme_error_t err = 0;
  char *linebuf;
  size_t linebufsize;
  int linelen;
  char *argv[7];
  int argc = 0;
  int rp[2];
  struct spawn_fd_item_s cfd[] = { {-1, 1 /* STDOUT_FILENO */, -1, 0},
				   {-1, -1} };
  int status;
  int nread;
  char *mark = NULL;

  if (!have_gpgconf_version (gpgconf, "2.1.16"))
    return gpg_error (GPG_ERR_ENGINE_TOO_OLD);

  /* _gpgme_engine_new guarantees that this is not NULL.  */
  argv[argc++] = gpgconf->file_name;

  if (gpgconf->home_dir)
    {
      argv[argc++] = (char*)"--homedir";
      argv[argc++] = gpgconf->home_dir;
    }

  argv[argc++] = (char*)"--query-swdb";
  argv[argc++] = (char*)name;
  argv[argc++] = (char*)iversion;
  argv[argc] = NULL;
  assert (argc < DIM (argv));

  if (_gpgme_io_pipe (rp, 1) < 0)
    return gpg_error_from_syserror ();

  cfd[0].fd = rp[1];

  status = _gpgme_io_spawn (gpgconf->file_name, argv,
                            IOSPAWN_FLAG_DETACHED, cfd, NULL, NULL, NULL);
  if (status < 0)
    {
      _gpgme_io_close (rp[0]);
      _gpgme_io_close (rp[1]);
      return gpg_error_from_syserror ();
    }

  linebufsize = 2048; /* Same as used by gpgconf.  */
  linebuf = malloc (linebufsize);
  if (!linebuf)
    {
      err = gpg_error_from_syserror ();
      goto leave;
    }
  linelen = 0;

  while ((nread = _gpgme_io_read (rp[0], linebuf + linelen,
                                  linebufsize - linelen - 1)))
    {
      char *line;
      const char *lastmark = NULL;
      size_t nused;

      if (nread < 0)
        {
          err = gpg_error_from_syserror ();
          goto leave;
        }

      linelen += nread;
      linebuf[linelen] = '\0';

      for (line=linebuf; (mark = strchr (line, '\n')); line = mark+1 )
        {
          lastmark = mark;
          if (mark > line && mark[-1] == '\r')
            mark[-1] = '\0';
          else
            mark[0] = '\0';

          /* Got a full line.  Due to the CR removal code (which
             occurs only on Windows) we might be one-off and thus
             would see empty lines.  */
          if (*line)
            {
              err = parse_swdb_line (line, result);
              goto leave; /* Ready.  */
            }
          else /* empty line.  */
            err = 0;
        }

      nused = lastmark? (lastmark + 1 - linebuf) : 0;
      memmove (linebuf, linebuf + nused, linelen - nused);
      linelen -= nused;

      if (!(linelen < linebufsize - 1))
        {
          char *newlinebuf;

          if (linelen <  8 * 1024 - 1)
            linebufsize = 8 * 1024;
          else if (linelen < 64 * 1024 - 1)
            linebufsize = 64 * 1024;
          else
            {
              /* We reached our limit - give up.  */
              err = gpg_error (GPG_ERR_LINE_TOO_LONG);
              goto leave;
            }

          newlinebuf = realloc (linebuf, linebufsize);
          if (!newlinebuf)
            {
              err = gpg_error_from_syserror ();
              goto leave;
            }
          linebuf = newlinebuf;
        }
    }

 leave:
  free (linebuf);
  _gpgme_io_close (rp[0]);
  return err;
}


static void
gpgconf_set_io_cbs (void *engine, gpgme_io_cbs_t io_cbs)
{
  (void)engine;
  (void)io_cbs;
  /* Nothing to do.  */
}


/* Currently, we do not use the engine interface for the various
   operations.  */
void
_gpgme_conf_release (gpgme_conf_comp_t conf)
{
  gpgconf_config_release (conf);
}


struct engine_ops _gpgme_engine_ops_gpgconf =
  {
    /* Static functions.  */
    _gpgme_get_default_gpgconf_name,
    NULL,
    gpgconf_get_version,
    gpgconf_get_req_version,
    gpgconf_new,

    /* Member functions.  */
    gpgconf_release,
    NULL,		/* reset */
    NULL,               /* set_status_cb */
    NULL,		/* set_status_handler */
    NULL,		/* set_command_handler */
    NULL,		/* set_colon_line_handler */
    NULL,		/* set_locale */
    NULL,		/* set_protocol */
    NULL,               /* set_engine_flags */
    NULL,		/* decrypt */
    NULL,		/* delete */
    NULL,		/* edit */
    NULL,		/* encrypt */
    NULL,		/* encrypt_sign */
    NULL,		/* export */
    NULL,		/* export_ext */
    NULL,		/* genkey */
    NULL,		/* import */
    NULL,		/* keylist */
    NULL,		/* keylist_ext */
    NULL,               /* keylist_data */
    NULL,               /* keysign */
    NULL,               /* revsig */
    NULL,               /* tofu_policy */
    NULL,		/* sign */
    NULL,		/* verify */
    NULL,		/* getauditlog */
    NULL,               /* setexpire */
    NULL,               /* setownertrust */
    NULL,               /* opassuan_transact */
    gpgconf_conf_load,
    gpgconf_conf_save,
    gpgconf_conf_dir,
    gpgconf_query_swdb,
    gpgconf_set_io_cbs,
    NULL,		/* io_event */
    NULL,		/* cancel */
    NULL,               /* cancel_op */
    NULL,               /* passwd */
    NULL,               /* set_pinentry_mode */
    NULL                /* opspawn */
  };
