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[Libguestfs] [PATCH 2/2] New APIs: Support for opening LUKS-encrypted disks.



-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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>From 637f8df83726ab9b50e8a6d2181bd1e0e93ec13e Mon Sep 17 00:00:00 2001
From: Richard Jones <rjones redhat com>
Date: Wed, 21 Jul 2010 19:50:06 +0100
Subject: [PATCH 2/2] 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).
---
 TODO                        |   13 ++++
 appliance/kmod.whitelist.in |   15 +++++
 appliance/packagelist.in    |    2 +
 daemon/Makefile.am          |    1 +
 daemon/luks.c               |  138 +++++++++++++++++++++++++++++++++++++++++++
 fish/guestfish.pod          |   33 ++++++++++
 po/POTFILES.in              |    1 +
 src/MAX_PROC_NR             |    2 +-
 src/generator.ml            |   37 ++++++++++++
 src/guestfs.pod             |   31 ++++++++++
 10 files changed, 272 insertions(+), 1 deletions(-)
 create mode 100644 daemon/luks.c

diff --git a/TODO b/TODO
index fc6b3fd..d0196c8 100644
--- a/TODO
+++ b/TODO
@@ -356,3 +356,16 @@ Progress of long-running operations
 For example, copying in virt-resize.  How can we display the progress
 of these operations?  This is a basic usability requirement, and
 frequently requested.
+
+Better support for encrypted devices
+------------------------------------
+
+Currently LUKS support only works if the device contains volume
+groups.  If it contains, eg., partitions, you cannot access them.
+We would like to add:
+
+  - 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).
diff --git a/appliance/kmod.whitelist.in b/appliance/kmod.whitelist.in
index 0a92122..850b7b8 100644
--- a/appliance/kmod.whitelist.in
+++ b/appliance/kmod.whitelist.in
@@ -69,3 +69,18 @@ loop.ko
 gfs2.ko
 dlm.ko
 configfs.ko
+
+# Used by dm-crypt.  Probably many more crypto modules
+# should be added here.
+aes*.ko
+blkcipher.ko
+cbc.ko
+cryptd.ko
+crypto_blkcipher.ko
+gf128mul.ko
+padlock-aes.ko
+sha256*.ko
+sha512*.ko
+xor.ko
+xts.ko
+zlib.ko
diff --git a/appliance/packagelist.in b/appliance/packagelist.in
index 16dc88d..4d45963 100644
--- a/appliance/packagelist.in
+++ b/appliance/packagelist.in
@@ -11,6 +11,7 @@
 #if REDHAT == 1
   augeas-libs
   btrfs-progs
+  cryptsetup-luks
   diffutils
   e2fsprogs
   /* e4fsprogs only exists on RHEL 5, will be ignored everywhere else. */
@@ -34,6 +35,7 @@
 #elif DEBIAN == 1
   bsdmainutils
   btrfs-tools
+  cryptsetup
   /* Dependency problem prevents installation of these two:
   gfs-tools
   gfs2-tools
diff --git a/daemon/Makefile.am b/daemon/Makefile.am
index cf9f7ca..27fca2a 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 0000000..f5a0b9d
--- /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;
+}
diff --git a/fish/guestfish.pod b/fish/guestfish.pod
index 86dcf58..bfcec5c 100644
--- a/fish/guestfish.pod
+++ b/fish/guestfish.pod
@@ -530,6 +530,39 @@ it, eg:
 
  echo "~"
 
+=head1 ENCRYPTED DISKS
+
+Libguestfs has some support for Linux guests encrypted according to
+the Linux Unified Key Setup (LUKS) standard, which includes nearly all
+whole disk encryption systems used by modern Linux guests.  Currently
+only LVM-on-LUKS is supported.
+
+Identify encrypted block devices and partitions using L</vfs-type>:
+
+ ><fs> vfs-type /dev/sda2
+ crypto_LUKS
+
+Then open those devices using L</luks-open>.  This creates a
+device-mapper device called C</dev/mapper/luksdev>.
+
+ ><fs> luks-open /dev/sda2 luksdev
+ Enter key or passphrase ("key"): <enter the passphrase>
+
+Finally you have to tell LVM to scan for volume groups on
+the newly created mapper device:
+
+ ><fs> vgscan
+ ><fs> vg-activate-all true
+
+The logical volume(s) can now be mounted in the usual way.
+
+Before closing a LUKS device you must unmount any logical volumes on
+it and deactivate the volume groups by calling C<vg-activate false VG>
+on each one.  Then you can close the mapper device:
+
+ ><fs> vg-activate false /dev/VG
+ ><fs> luks-close /dev/mapper/luksdev
+
 =head1 WINDOWS PATHS
 
 If a path is prefixed with C<win:> then you can use Windows-style
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 62df1fd..4a27d87 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -33,6 +33,7 @@ daemon/initrd.c
 daemon/inotify.c
 daemon/link.c
 daemon/ls.c
+daemon/luks.c
 daemon/lvm-filter.c
 daemon/lvm.c
 daemon/mkfs.c
diff --git a/src/MAX_PROC_NR b/src/MAX_PROC_NR
index 9183bf0..98ecf58 100644
--- a/src/MAX_PROC_NR
+++ b/src/MAX_PROC_NR
@@ -1 +1 @@
-256
+259
diff --git a/src/generator.ml b/src/generator.ml
index 0df77a3..71421bc 100755
--- a/src/generator.ml
+++ b/src/generator.ml
@@ -4881,6 +4881,43 @@ will be able to see every block device.
 This command also clears the LVM cache and performs a volume
 group scan.");
 
+  ("luks_open", (RErr, [Device "device"; Key "key"; String "mapname"]), 257, [Optional "luks"],
+   [],
+   "open a LUKS-encrypted block device",
+   "\
+This command opens a block device which has been encrypted
+according to the Linux Unified Key Setup (LUKS) standard.
+
+C<device> is the encrypted block device or partition.
+
+The caller must supply one of the keys associated with the
+LUKS block device, in the C<key> parameter.
+
+This creates a new block device called C</dev/mapper/mapname>.
+Reads and writes to this block device are decrypted from and
+encrypted to the underlying C<device> respectively.
+
+If this block device contains LVM volume groups, then
+calling C<guestfs_vgscan> followed by C<guestfs_vg_activate_all>
+will make them visible.");
+
+  ("luks_open_ro", (RErr, [Device "device"; Key "key"; String "mapname"]), 258, [Optional "luks"],
+   [],
+   "open a LUKS-encrypted block device read-only",
+   "\
+This is the same as C<guestfs_luks_open> except that a read-only
+mapping is created.");
+
+  ("luks_close", (RErr, [Device "device"]), 259, [Optional "luks"],
+   [],
+   "close a LUKS device",
+   "\
+This closes a LUKS device that was created earlier by
+C<guestfs_luks_open> or C<guestfs_luks_open_ro>.  The
+C<device> parameter must be the name of the LUKS mapping
+device (ie. C</dev/mapper/mapname>) and I<not> the name
+of the underlying block device.");
+
 ]
 
 let all_functions = non_daemon_functions @ daemon_functions
diff --git a/src/guestfs.pod b/src/guestfs.pod
index 8e3d07c..5a2e7a5 100644
--- a/src/guestfs.pod
+++ b/src/guestfs.pod
@@ -450,6 +450,37 @@ L</guestfs_chmod> after creating each file or directory.
 
 For more information about umask, see L<umask(2)>.
 
+=head2 ENCRYPTED DISKS
+
+Libguestfs allows you to access Linux guests which have been
+encrypted using whole disk encryption that conforms to the
+Linux Unified Key Setup (LUKS) standard.  This includes
+nearly all whole disk encryption systems used by modern
+Linux guests.
+
+Use L</guestfs_vfs_type> to identify LUKS-encrypted block
+devices (it returns the string C<crypto_LUKS>).
+
+Then open these devices by calling L</guestfs_luks_open>.
+Obviously you will require the passphrase!
+
+Opening a LUKS device creates a new device mapper device
+called C</dev/mapper/mapname> (where C<mapname> is the
+string you supply to L</guestfs_luks_open>).
+Reads and writes to this mapper device are decrypted from and
+encrypted to the underlying block device respectively.
+
+LVM volume groups on the device can be made visible by calling
+L</guestfs_vgscan> followed by L</guestfs_vg_activate_all>.
+The logical volume(s) can now be mounted in the usual way.
+
+Use the reverse process to close a LUKS device.  Unmount
+any logical volumes on it, deactivate the volume groups
+by caling C<guestfs_vg_activate (g, 0, ["/dev/VG"])>.
+Then close the mapper device by calling
+L</guestfs_luks_close> on the C</dev/mapper/mapname>
+device (I<not> the underlying encrypted block device).
+
 =head2 SPECIAL CONSIDERATIONS FOR WINDOWS GUESTS
 
 Libguestfs can mount NTFS partitions.  It does this using the
-- 
1.7.1


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