gnupg/g13/mount.c

/* mount.c - Mount a crypto container
 * Copyright (C) 2009 Free Software Foundation, Inc.
 *
 * This file is part of GnuPG.
 *
 * GnuPG is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * GnuPG 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/stat.h>
#include <assert.h>

#include "g13.h"
#include "i18n.h"
#include "mount.h"

#include "keyblob.h"
#include "backend.h"
#include "g13tuple.h"
#include "mountinfo.h"
#include "runner.h"
#include "host2net.h"
#include "../common/sysutils.h"


/* Mount the container with name FILENAME at MOUNTPOINT.  */
gpg_error_t
g13_mount_container (ctrl_t ctrl, const char *filename, const char *mountpoint)
{
  gpg_error_t err;
  dotlock_t lock;
  int needs_syshelp;
  void *enckeyblob = NULL;
  size_t enckeybloblen;
  void *keyblob = NULL;
  size_t keybloblen;
  tupledesc_t tuples = NULL;
  size_t n;
  const unsigned char *value;
  int conttype;
  unsigned int rid;
  char *mountpoint_buffer = NULL;

  /* A quick check to see whether the container exists.  */
  if (access (filename, R_OK))
    return gpg_error_from_syserror ();

  /* Decide whether we need to use the g13-syshelp because we can't
     use lock files for them.  This is most likely the case for device
     files; thus we test for this.  FIXME: The correct solution would
     be to call g13-syshelp to match the file against the g13tab.  */
  needs_syshelp = !strncmp (filename, "/dev/", 5);

  if (!mountpoint)
    {
      mountpoint_buffer = xtrystrdup ("/tmp/g13-XXXXXX");
      if (!mountpoint_buffer)
        return gpg_error_from_syserror ();
      if (!gnupg_mkdtemp (mountpoint_buffer))
        {
          err = gpg_error_from_syserror ();
          log_error (_("can't create directory '%s': %s\n"),
                     "/tmp/g13-XXXXXX", gpg_strerror (err));
          xfree (mountpoint_buffer);
          return err;
        }
      mountpoint = mountpoint_buffer;
    }

  err = 0;
  if (needs_syshelp)
    lock = NULL;
  else
    {
      /* Try to take a lock.  */
      lock = dotlock_create (filename, 0);
      if (!lock)
        {
          xfree (mountpoint_buffer);
          return gpg_error_from_syserror ();
        }

      if (dotlock_take (lock, 0))
        {
          err = gpg_error_from_syserror ();
          goto leave;
        }
    }

  /* Check again that the file exists.  */
  {
    struct stat sb;

    if (stat (filename, &sb))
      {
        err = gpg_error_from_syserror ();
        goto leave;
      }
  }

  /* Read the encrypted keyblob.  */
  /* Fixme: Should we move this to syshelp for dm-crypt or do we
     assume that the encrypted device is world readable?  */
  err = g13_keyblob_read (filename, &enckeyblob, &enckeybloblen);
  if (err)
    goto leave;

  /* Decrypt that keyblob and store it in a tuple descriptor.  */
  err = g13_keyblob_decrypt (ctrl, enckeyblob, enckeybloblen,
                             &keyblob, &keybloblen);
  if (err)
    goto leave;
  xfree (enckeyblob);
  enckeyblob = NULL;

  err = create_tupledesc (&tuples, keyblob, keybloblen);
  if (!err)
    keyblob = NULL;
  else
    {
      if (gpg_err_code (err) == GPG_ERR_NOT_SUPPORTED)
        log_error ("unknown keyblob version\n");
      goto leave;
    }
  if (opt.verbose)
    dump_tupledesc (tuples);

  value = find_tuple (tuples, KEYBLOB_TAG_CONTTYPE, &n);
  if (!value || n != 2)
    conttype = 0;
  else
    conttype = (value[0] << 8 | value[1]);
  if (!be_is_supported_conttype (conttype))
    {
      log_error ("content type %d is not supported\n", conttype);
      err = gpg_error (GPG_ERR_NOT_SUPPORTED);
      goto leave;
    }
  err = be_mount_container (ctrl, conttype, filename, mountpoint, tuples, &rid);
  if (err)
    ;
  else if (conttype == CONTTYPE_DM_CRYPT)
    g13_request_shutdown ();
  else
    {
      /* Unless this is a DM-CRYPT mount we put it into our mounttable
         so that we can manage the mounts ourselves.  For dm-crypt we
         do not keep a process to monitor he mounts (for now).  */
      err = mountinfo_add_mount (filename, mountpoint, conttype, rid,
                                 !!mountpoint_buffer);
      /* Fixme: What shall we do if this fails?  Add a provisional
         mountinfo entry first and remove it on error? */
      if (!err)
        {
          char *tmp = percent_plus_escape (mountpoint);
          if (!tmp)
            err = gpg_error_from_syserror ();
          else
            {
              g13_status (ctrl, STATUS_MOUNTPOINT, tmp, NULL);
              xfree (tmp);
            }
        }
    }

 leave:
  destroy_tupledesc (tuples);
  xfree (keyblob);
  xfree (enckeyblob);
  dotlock_destroy (lock);
  xfree (mountpoint_buffer);
  return err;
}


/* Unmount the container with name FILENAME or the one mounted at
   MOUNTPOINT.  If both are given the FILENAME takes precedence.  */
gpg_error_t
g13_umount_container (ctrl_t ctrl, const char *filename, const char *mountpoint)
{
  gpg_error_t err;
  unsigned int rid;
  runner_t runner;

  (void)ctrl;

  if (!filename && !mountpoint)
    return gpg_error (GPG_ERR_ENOENT);
  err = mountinfo_find_mount (filename, mountpoint, &rid);
  if (err)
    return err;

  runner = runner_find_by_rid (rid);
  if (!runner)
    {
      log_error ("runner %u not found\n", rid);
      return gpg_error (GPG_ERR_NOT_FOUND);
    }

  runner_cancel (runner);
  runner_release (runner);

  return 0;
}