New APIs: Support for opening LUKS-encrypted disks.

This adds support for opening LUKS-encrypted disks, via
three new APIs:

  luks_open:    Create a mapping for an encrypted disk.
  luks_open_ro: Same, but read-only mapping.
  luks_close:   Close a mapping.

A typical guestfish session using this functionality looks
like this:

  $ guestfish --ro -a encrypted.img
  ><fs> run
  ><fs> list-devices
  /dev/vda
  ><fs> list-partitions
  /dev/vda1
  /dev/vda2
  ><fs> vfs-type /dev/vda2
  crypto_LUKS
  ><fs> luks-open /dev/vda2 luksdev
  Enter key or passphrase ("key"):
  ><fs> vgscan
  ><fs> vg-activate-all true
  ><fs> pvs
  /dev/dm-0
  ><fs> vgs
  vg_f13x64encrypted
  ><fs> lvs
  /dev/vg_f13x64encrypted/lv_root
  /dev/vg_f13x64encrypted/lv_swap
  ><fs> mount /dev/vg_f13x64encrypted/lv_root /
  ><fs> ll /
  total 132
  dr-xr-xr-x.  24 root root  4096 Jul 21 12:01 .
  dr-xr-xr-x   20 root root     0 Jul 21 20:06 ..
  drwx------.   3 root root  4096 Jul 21 11:59 .dbus
  drwx------.   2 root root  4096 Jul 21 12:00 .pulse
  -rw-------.   1 root root   256 Jul 21 12:00 .pulse-cookie
  dr-xr-xr-x.   2 root root  4096 May 13 03:03 bin

NOT included in this patch:

 - An easier way to use this from guestfish.
 - Ability to create LUKS devices.
 - Ability to change LUKS keys on existing devices.
 - Direct access to the /dev/mapper device (eg. if it contains
   anything apart from VGs).

2 files changed, 139 insertions, 0 deletions

diff --git a/daemon/Makefile.am b/daemon/Makefile.am
index cf9f7ca3..27fca2a2 100644
--- a/daemon/Makefile.am
+++ b/daemon/Makefile.am
@@ -98,6 +98,7 @@ guestfsd_SOURCES = \
 	inotify.c \
 	link.c \
 	ls.c \
+	luks.c \
 	lvm.c \
 	lvm-filter.c \
 	mkfs.c \
diff --git a/daemon/luks.c b/daemon/luks.c
new file mode 100644
index 00000000..f5a0b9dc
--- /dev/null
+++ b/daemon/luks.c
@@ -0,0 +1,138 @@
+/* libguestfs - the guestfsd daemon
+ * Copyright (C) 2010 Red Hat Inc.
+ *
+ * This program 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "daemon.h"
+#include "c-ctype.h"
+#include "actions.h"
+#include "optgroups.h"
+
+int
+optgroup_luks_available (void)
+{
+  return prog_exists ("cryptsetup");
+}
+
+static int
+luks_open (const char *device, const char *key, const char *mapname,
+           int readonly)
+{
+  /* Sanity check: /dev/mapper/mapname must not exist already.  Note
+   * that the device-mapper control device (/dev/mapper/control) is
+   * always there, so you can't ever have mapname == "control".
+   */
+  size_t len = strlen (mapname);
+  char devmapper[len+32];
+  snprintf (devmapper, len+32, "/dev/mapper/%s", mapname);
+  if (access (devmapper, F_OK) == 0) {
+    reply_with_error ("%s: device already exists", devmapper);
+    return -1;
+  }
+
+  char tempfile[] = "/tmp/luksXXXXXX";
+  int fd = mkstemp (tempfile);
+  if (fd == -1) {
+    reply_with_perror ("mkstemp");
+    return -1;
+  }
+
+  len = strlen (key);
+  if (xwrite (fd, key, len) == -1) {
+    reply_with_perror ("write");
+    close (fd);
+    unlink (tempfile);
+    return -1;
+  }
+
+  if (close (fd) == -1) {
+    reply_with_perror ("close");
+    unlink (tempfile);
+    return -1;
+  }
+
+  const char *argv[16];
+  size_t i = 0;
+
+  argv[i++] = "cryptsetup";
+  argv[i++] = "-d";
+  argv[i++] = tempfile;
+  if (readonly) argv[i++] = "--readonly";
+  argv[i++] = "luksOpen";
+  argv[i++] = device;
+  argv[i++] = mapname;
+  argv[i++] = NULL;
+
+  char *err;
+  int r = commandv (NULL, &err, (const char * const *) argv);
+  unlink (tempfile);
+
+  if (r == -1) {
+    reply_with_error ("%s", err);
+    free (err);
+    return -1;
+  }
+
+  free (err);
+
+  udev_settle ();
+
+  return 0;
+}
+
+int
+do_luks_open (const char *device, const char *key, const char *mapname)
+{
+  return luks_open (device, key, mapname, 0);
+}
+
+int
+do_luks_open_ro (const char *device, const char *key, const char *mapname)
+{
+  return luks_open (device, key, mapname, 1);
+}
+
+int
+do_luks_close (const char *device)
+{
+  /* Must be /dev/mapper/... */
+  if (! STRPREFIX (device, "/dev/mapper/")) {
+    reply_with_error ("luks_close: you must call this on the /dev/mapper device created by luks_open");
+    return -1;
+  }
+
+  const char *mapname = &device[12];
+
+  char *err;
+  int r = command (NULL, &err, "cryptsetup", "luksClose", mapname, NULL);
+  if (r == -1) {
+    reply_with_error ("%s", err);
+    free (err);
+    return -1;
+  }
+
+  free (err);
+
+  udev_settle ();
+
+  return 0;
+}