g13: First chunk of code to support dm-crypt.

* g13/call-syshelp.c, g13/call-syshelp.h: New.
* g13/g13-syshelp.c, g13/g13-syshelp.h: New.
* g13/sh-cmd.c: New.
* g13/sh-blockdev.c: New.
* g13/sh-exectool.c: New.
* g13/sh-dmcrypt.c: New.
* g13/Makefile.am (sbin_PROGRAMS): Add g13-syshelp.c
(g13_syshelp_SOURCES): New.
(g13_syshelp_LDADD): New.

* g13/g13.c (opts): Add option --type.
(g13_deinit_default_ctrl): New.
(main): Implement that option.  Call g13_deinit_default_ctrl.
* g13/g13.h (struct call_syshelp_s): New declaration.
(server_control_s): Add field syshelp_local.
* g13/keyblob.h (KEYBLOB_TAG_CREATED): New.
(KEYBLOB_TAG_ALGOSTR): New.
(KEYBLOB_TAG_HDRCOPY): New.
* g13/backend.c (be_parse_conttype_name): New.
(be_get_detached_name): Add CONTTYPE_DM_CRYPT.

Signed-off-by: Werner Koch <wk@gnupg.org>

g13/sh-blockdev.c

@@ -0,0 +1,151 @@
+/* sh-blockdev.c - Block device functions for g13-syshelp
+ * Copyright (C) 2015 Werner Koch
+ *
+ * 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 <stdarg.h>
+#include <errno.h>
+#include <assert.h>
+#include <limits.h>
+
+#include "g13-syshelp.h"
+#include <assuan.h>
+#include "i18n.h"
+#include "keyblob.h"
+
+#ifndef HAVE_STRTOULL
+# error building this tool requires strtoull(3)
+#endif
+#ifndef ULLONG_MAX
+# error ULLONG_MAX missing
+#endif
+
+
+/* Return the size measured in the number of 512 byte sectors for the
+   block device NAME.  */
+gpg_error_t
+sh_blockdev_getsz (const char *name, unsigned long long *r_nblocks)
+{
+  gpg_error_t err;
+  const char *argv[3];
+  char *result;
+
+  *r_nblocks = 0;
+  argv[0] = "--getsz";
+  argv[1] = name;
+  argv[2] = NULL;
+  err = sh_exec_tool ("/sbin/blockdev", argv, NULL, &result, NULL);
+  if (!err)
+    {
+      gpg_err_set_errno (0);
+      *r_nblocks = strtoull (result, NULL, 10);
+      if (*r_nblocks == ULLONG_MAX && errno)
+        {
+          err = gpg_error_from_syserror ();
+          *r_nblocks = 0;
+        }
+      xfree (result);
+    }
+  return err;
+}
+
+
+/* Return 0 if the device NAME looks like an empty partition. */
+gpg_error_t
+sh_is_empty_partition (const char *name)
+{
+  gpg_error_t err;
+  const char *argv[6];
+  char *buffer;
+  estream_t fp;
+  char *p;
+  size_t nread;
+
+  argv[0] = "-o";
+  argv[1] = "value";
+  argv[2] = "-s";
+  argv[3] = "UUID";
+  argv[4] = name;
+  argv[5] = NULL;
+  err = sh_exec_tool ("/sbin/blkid", argv, NULL, &buffer, NULL);
+  if (err)
+    return gpg_error (GPG_ERR_FALSE);
+  if (*buffer)
+    {
+      /* There seems to be an UUID - thus we have a file system.  */
+      xfree (buffer);
+      return gpg_error (GPG_ERR_FALSE);
+    }
+  xfree (buffer);
+
+  argv[0] = "-o";
+  argv[1] = "value";
+  argv[2] = "-s";
+  argv[3] = "PARTUUID";
+  argv[4] = name;
+  argv[5] = NULL;
+  err = sh_exec_tool ("/sbin/blkid", argv, NULL, &buffer, NULL);
+  if (err)
+    return gpg_error (GPG_ERR_FALSE);
+  if (!*buffer)
+    {
+      /* If there is no PARTUUID we assume that name has already a
+         mapped partition.  */
+      xfree (buffer);
+      return gpg_error (GPG_ERR_FALSE);
+    }
+  xfree (buffer);
+
+  /* As a safeguard we require that the first 32k of a partition are
+     all zero before we assume the partition is empty.  */
+  buffer = xtrymalloc (32 * 1024);
+  if (!buffer)
+    return gpg_error_from_syserror ();
+  fp = es_fopen (name, "rb,samethread");
+  if (!fp)
+    {
+      err = gpg_error_from_syserror ();
+      log_error ("error opening '%s': %s\n", name, gpg_strerror (err));
+      xfree (buffer);
+      return gpg_error (GPG_ERR_FALSE);
+    }
+  if (es_read (fp, buffer, 32 * 1024, &nread))
+    err = gpg_error_from_syserror ();
+  else if (nread != 32 *1024)
+    err = gpg_error (GPG_ERR_TOO_SHORT);
+  else
+    err = 0;
+  es_fclose (fp);
+  if (err)
+    {
+      log_error ("error reading the first 32 KiB from '%s': %s\n",
+                 name, gpg_strerror (err));
+      xfree (buffer);
+      return err;
+    }
+  for (p=buffer; nread && !*p; nread--, p++)
+    ;
+  xfree (buffer);
+  if (nread)
+    return gpg_error (GPG_ERR_FALSE);  /* No all zeroes.  */
+
+  return 0;
+}