[systemd-devel] [PATCH 3/3 (rebased)] cryptsetup: Add tcrypt support
Jan Janssen
medhefgo at web.de
Tue Jul 9 12:15:05 PDT 2013
Tcrypt uses a different approach to passphrases/key files. The
passphrase and all key files are incorporated into the "password"
to open the volume. So, the idea of slots that provide a way to
open the volume with different passphrases/key files that are
independent from each other like with LUKS does not apply.
Therefore, we use the key file from /etc/crypttab as the source
for the passphrase. The actual key files that are combined with
the passphrase into a password are provided as a new option in
/etc/crypttab and can be given multiple times if more than one
key file is used by a volume.
---
Hi,
this is just a rebase so this patch applies cleanly. The other two
patches still work.
I would really like to see this one get in. I've been using this
to mount my system encrypted truecrypt partition ever since I
cooked this up and it works very nicely.
Anyone who wants to test system encryption mode should probably
get themselves the latest git version of cryptsetup since it
contains a few fixes for that mode (mainly making this mode work
on a drive with other patitions already mounted/in use). But as long
as you don't use system mode (removeable media, truecrypt container
files, or non-system encrypted partitions) you'd only need
cryptsetup 1.6.0.
Thanks,
Jan
man/crypttab.xml | 300 +++++++++++++++++++++++++++-----------------
src/cryptsetup/cryptsetup.c | 81 +++++++++++-
2 files changed, 259 insertions(+), 122 deletions(-)
diff --git a/man/crypttab.xml b/man/crypttab.xml
index e52b7e6..298f39e 100644
--- a/man/crypttab.xml
+++ b/man/crypttab.xml
@@ -75,23 +75,29 @@
fields are mandatory, the remaining two are
optional.</para>
+ <para>Setting up encrypted block devices using this file
+ supports three encryption modes: LUKS, TrueCrypt and plain.
+ See <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ for more information about each mode. When no mode is specified
+ in the options field and the block device contains a LUKS
+ signature, it is opened as a LUKS device; otherwise, it is
+ assumed to be in raw dm-crypt (plain mode) format.</para>
+
<para>The first field contains the name of the
resulting encrypted block device; the device is set up
within <filename>/dev/mapper/</filename>.</para>
<para>The second field contains a path to the
- underlying block device, or a specification of a block
+ underlying block device or file, or a specification of a block
device via <literal>UUID=</literal> followed by the
- UUID. If the block device contains a LUKS signature,
- it is opened as a LUKS encrypted partition; otherwise,
- it is assumed to be a raw dm-crypt partition.</para>
+ UUID.</para>
<para>The third field specifies the encryption
password. If the field is not present or the password
- is set to none, the password has to be manually
- entered during system boot. Otherwise, the field is
- interpreted as a path to a file containing the
- encryption password. For swap encryption,
+ is set to <literal>none</literal> or <literal>-</literal>,
+ the password has to be manually entered during system boot.
+ Otherwise, the field is interpreted as a absolute path to
+ a file containing the encryption password. For swap encryption,
<filename>/dev/urandom</filename> or the hardware
device <filename>/dev/hw_random</filename> can be used
as the password file; using
@@ -104,181 +110,237 @@
options are recognized:</para>
<variablelist class='crypttab-options'>
+
+ <varlistentry>
+ <term><varname>allow-discards</varname></term>
+
+ <listitem><para>Allow discard requests to be
+ passed through the encrypted block device. This
+ improves performance on SSD storage but has
+ security implications.</para></listitem>
+ </varlistentry>
+
<varlistentry>
<term><varname>cipher=</varname></term>
- <listitem><para>Specifies the cipher
- to use; see
+ <listitem><para>Specifies the cipher to use. See
<citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
- for possible values and the default
- value of this option. A cipher with
- unpredictable IV values, such as
- <literal>aes-cbc-essiv:sha256</literal>,
- is recommended. </para></listitem>
+ for possible values and the default value of
+ this option. A cipher with unpredictable IV
+ values, such as <literal>aes-cbc-essiv:sha256</literal>,
+ is recommended.</para></listitem>
</varlistentry>
-
<varlistentry>
- <term><varname>size=</varname></term>
+ <term><varname>hash=</varname></term>
- <listitem><para>Specifies the key size
- in bits; see
+ <listitem><para>Specifies the hash to use for
+ password hashing. See
<citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
- for possible values and the default
- value of this
- option. </para></listitem>
+ for possible values and the default value of
+ this option.</para></listitem>
</varlistentry>
+ <varlistentry>
+ <term><varname>keyfile-offset=</varname></term>
+
+ <listitem><para>Specifies the number of bytes to
+ skip at the start of the key file. See
+ <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ for possible values and the default value of
+ this option.</para></listitem>
+ </varlistentry>
<varlistentry>
<term><varname>keyfile-size=</varname></term>
<listitem><para>Specifies the maximum number
- of bytes to read from the keyfile; see
+ of bytes to read from the key file. See
<citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
- for possible values and the default
- value of this option. This option is ignored
- in plain encryption mode, as the keyfile-size is then given by the key size.</para></listitem>
+ for possible values and the default value of
+ this option. This option is ignored in plain
+ encryption mode, as the key file size is then
+ given by the key size.</para></listitem>
</varlistentry>
-
<varlistentry>
- <term><varname>keyfile-offset=</varname></term>
+ <term><varname>luks</varname></term>
- <listitem><para>Specifies the number
- of bytes to skip at the start of
- the keyfile; see
- <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
- for possible values and the default
- value of this option.</para></listitem>
+ <listitem><para>Force LUKS mode. When this mode
+ is used the following options are ignored since
+ they are provided by the LUKS header on the
+ device: <varname>cipher=</varname>,
+ <varname>hash=</varname>,
+ <varname>size=</varname>.</para></listitem>
</varlistentry>
-
<varlistentry>
- <term><varname>hash=</varname></term>
+ <term><varname>noauto</varname></term>
- <listitem><para>Specifies the hash to
- use for password hashing; see
- <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> for possible values and
- the default value of this
- option. </para></listitem>
+ <listitem><para>This device will not be
+ automatically unlocked on boot.</para></listitem>
</varlistentry>
<varlistentry>
- <term><varname>tries=</varname></term>
+ <term><varname>nofail</varname></term>
- <listitem><para>Specifies the maximum
- number of times the user is queried
- for a password.</para></listitem>
+ <listitem><para>The system will not wait for the
+ device to show up and be unlocked at boot, and
+ not fail the boot if it does not show up.</para></listitem>
</varlistentry>
<varlistentry>
- <term><varname>verify</varname></term>
+ <term><varname>plain</varname></term>
- <listitem><para> If the encryption
- password is read from console, it has
- to be entered twice (to prevent
- typos). </para></listitem>
+ <listitem><para>Force plain encryption mode.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>read-only</varname></term><term><varname>readonly</varname></term>
- <listitem><para>Set up the encrypted
- block device in read-only
- mode.</para></listitem>
+ <listitem><para>Set up the encrypted block
+ device in read-only mode.</para></listitem>
</varlistentry>
<varlistentry>
- <term><varname>allow-discards</varname></term>
+ <term><varname>size=</varname></term>
- <listitem><para>Allow discard requests
- to be passed through the encrypted
- block device. This improves
- performance on SSD storage but has
- security
- implications.</para></listitem>
+ <listitem><para>Specifies the key size
+ in bits. See
+ <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ for possible values and the default value of
+ this option.</para></listitem>
</varlistentry>
<varlistentry>
- <term><varname>luks</varname></term>
+ <term><varname>swap</varname></term>
- <listitem><para>Force LUKS mode.</para></listitem>
+ <listitem><para>The encrypted block device will
+ be used as a swap device, and will be formatted
+ accordingly after setting up the encrypted
+ block device, with
+ <citerefentry><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
+ This option implies <varname>plain</varname>.</para>
+
+ <para>WARNING: Using the <varname>swap</varname>
+ option will destroy the contents of the named
+ partition during every boot, so make sure the
+ underlying block device is specified correctly.</para></listitem>
</varlistentry>
<varlistentry>
- <term><varname>plain</varname></term>
+ <term><varname>tcrypt</varname></term>
+
+ <listitem><para>Use TrueCrypt encryption mode.
+ When this mode is used the following options are
+ ignored since they are provided by the TrueCrypt
+ header on the device or do not apply:
+ <varname>cipher=</varname>,
+ <varname>hash=</varname>,
+ <varname>keyfile-offset=</varname>,
+ <varname>keyfile-size=</varname>,
+ <varname>size=</varname>.</para>
+
+ <para>When this mode is used, the passphrase is
+ read from the key file given in the third field.
+ Only the first line of this file is read,
+ excluding the new line character.</para>
+
+ <para>Note that the TrueCrypt format uses both
+ passphrase and key files to derive a password
+ for the volume. Therefore, the passphrase and
+ all key files need to be provided. Use
+ <varname>tcrypt-keyfile=</varname> to provide
+ the absolute path to all key files. When using
+ an empty passphrase in combination with one or
+ more key files, use <literal>/dev/null</literal>
+ as the password file in the third field.</para></listitem>
+ </varlistentry>
- <listitem><para>Force plain encryption
- mode.</para></listitem>
+ <varlistentry>
+ <term><varname>tcrypt-hidden</varname></term>
+
+ <listitem><para>Use the hidden TrueCrypt volume.
+ This implies <varname>tcrypt</varname>.</para>
+
+ <para>This will map the hidden volume that is
+ inside of the volume provided in the second
+ field. Please note that there is no protection
+ for the hidden volume if the outer volume is
+ mounted instead. See
+ <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ for more information on this limitation.</para></listitem>
</varlistentry>
<varlistentry>
- <term><varname>timeout=</varname></term>
+ <term><varname>tcrypt-keyfile=</varname></term>
+
+ <listitem><para>Specifies the absolute path to a
+ key file to use for a TrueCrypt volume. This
+ implies <varname>tcrypt</varname> and can be
+ used more than once to provide several key
+ files.</para>
- <listitem><para>Specify the timeout
- for querying for a password. If no
- unit is specified seconds is used.
- Supported units are s, ms, us, min, h,
- d. A timeout of 0 waits indefinitely
- (which is the
- default).</para></listitem>
+ <para>See the entry for <varname>tcrypt</varname>
+ on the behavior of the passphrase and key files
+ when using TrueCrypt encryption mode.</para></listitem>
</varlistentry>
<varlistentry>
- <term><varname>noauto</varname></term>
+ <term><varname>tcrypt-system</varname></term>
+
+ <listitem><para>Use TrueCrypt in system
+ encryption mode. This implies
+ <varname>tcrypt</varname>.</para>
+
+ <para>Please note that when using this mode, the
+ whole device needs to be given in the second
+ field instead of the partition. For example: if
+ <literal>/dev/sda2</literal> is the system
+ encrypted TrueCrypt patition, <literal>/dev/sda</literal>
+ has to be given.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>timeout=</varname></term>
- <listitem><para> This device will not
- be automatically unlocked on
- boot. </para></listitem>
+ <listitem><para>Specifies the timeout for
+ querying for a password. If no unit is
+ specified, seconds is used. Supported units are
+ s, ms, us, min, h, d. A timeout of 0 waits
+ indefinitely (which is the default).</para></listitem>
</varlistentry>
<varlistentry>
- <term><varname>nofail</varname></term>
+ <term><varname>tmp</varname></term>
+
+ <listitem><para>The encrypted block device will
+ be prepared for using it as <filename>/tmp</filename>;
+ it will be formatted using
+ <citerefentry><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
+ This option implies <varname>plain</varname>.</para>
- <listitem><para>The system will not
- wait for the device to show up and be
- unlocked at boot, and not fail the
- boot if it does not show
- up.</para></listitem>
+ <para>WARNING: Using the <varname>tmp</varname>
+ option will destroy the contents of the named
+ partition during every boot, so make sure the
+ underlying block device is specified correctly.</para></listitem>
</varlistentry>
<varlistentry>
- <term><varname>swap</varname></term>
+ <term><varname>tries=</varname></term>
- <listitem><para> The encrypted block
- device will be used as a swap
- partition, and will be formatted as a
- swap partition after setting up the
- encrypted block device, with
- <citerefentry><refentrytitle>mkswap</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
-
- <para>WARNING: Using the
- <varname>swap</varname> option will
- destroy the contents of the named
- partition during every boot, so make
- sure the underlying block device is
- specified
- correctly. </para></listitem>
+ <listitem><para>Specifies the maximum number of
+ times the user is queried for a password.</para></listitem>
</varlistentry>
<varlistentry>
- <term><varname>tmp</varname></term>
+ <term><varname>verify</varname></term>
- <listitem><para>The encrypted block
- device will be prepared for using it
- as <filename>/tmp</filename>
- partition: it will be formatted using
- <citerefentry><refentrytitle>mke2fs</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
-
- <para>WARNING: Using the
- <varname>tmp</varname> option will
- destroy the contents of the named
- partition during every boot, so make
- sure the underlying block device is
- specified
- correctly. </para></listitem>
+ <listitem><para> If the encryption password is
+ read from console, it has to be entered twice to
+ prevent typos.</para></listitem>
</varlistentry>
+
</variablelist>
<para>At early boot and when the system manager
@@ -291,12 +353,14 @@
<title>Example</title>
<example>
<title>/etc/crypttab example</title>
- <para>Set up two encrypted block devices with
- LUKS: one normal one for storage, and another
- one for usage as swap device.</para>
-
- <programlisting>luks-2505567a-9e27-4efe-a4d5-15ad146c258b UUID=2505567a-9e27-4efe-a4d5-15ad146c258b - timeout=0
-swap /dev/sda7 /dev/urandom swap</programlisting>
+ <para>Set up four encrypted block devices. One using
+ LUKS for normal storage, another one for usage as a swap
+ device and two TrueCrypt volumes.</para>
+
+ <programlisting>luks UUID=2505567a-9e27-4efe-a4d5-15ad146c258b
+swap /dev/sda7 /dev/urandom swap
+truecrypt /dev/sda2 /etc/container_password tcrypt
+hidden /mnt/tc_hidden /null tcrypt-hidden,tcrypt-keyfile=/etc/keyfile</programlisting>
</example>
</refsect1>
diff --git a/src/cryptsetup/cryptsetup.c b/src/cryptsetup/cryptsetup.c
index cb48009..168936d 100644
--- a/src/cryptsetup/cryptsetup.c
+++ b/src/cryptsetup/cryptsetup.c
@@ -27,6 +27,7 @@
#include <libcryptsetup.h>
#include <libudev.h>
+#include "fileio.h"
#include "log.h"
#include "util.h"
#include "path-util.h"
@@ -34,7 +35,7 @@
#include "ask-password-api.h"
#include "def.h"
-static const char *opt_type = NULL; /* LUKS1 or PLAIN */
+static const char *opt_type = NULL; /* CRYPT_LUKS1, CRYPT_TCRYPT or CRYPT_PLAIN */
static char *opt_cipher = NULL;
static unsigned opt_key_size = 0;
static unsigned opt_keyfile_size = 0;
@@ -44,6 +45,9 @@ static unsigned opt_tries = 0;
static bool opt_readonly = false;
static bool opt_verify = false;
static bool opt_discards = false;
+static bool opt_tcrypt_hidden = false;
+static bool opt_tcrypt_system = false;
+static char **opt_tcrypt_keyfiles = NULL;
static usec_t opt_timeout = 0;
/* Options Debian's crypttab knows we don't:
@@ -82,6 +86,14 @@ static int parse_one_option(const char *option) {
return 0;
}
+ } else if (startswith(option, "tcrypt-keyfile=")) {
+
+ opt_type = CRYPT_TCRYPT;
+ if (path_is_absolute(option+15))
+ opt_tcrypt_keyfiles = strv_append(opt_tcrypt_keyfiles, strdup(option+15));
+ else
+ log_error("Key file path '%s' is not absolute. Ignoring.", option+15);
+
} else if (startswith(option, "keyfile-size=")) {
if (safe_atou(option+13, &opt_keyfile_size) < 0) {
@@ -121,7 +133,15 @@ static int parse_one_option(const char *option) {
opt_discards = true;
else if (streq(option, "luks"))
opt_type = CRYPT_LUKS1;
- else if (streq(option, "plain") ||
+ else if (streq(option, "tcrypt"))
+ opt_type = CRYPT_TCRYPT;
+ else if (streq(option, "tcrypt-hidden")) {
+ opt_type = CRYPT_TCRYPT;
+ opt_tcrypt_hidden = true;
+ } else if (streq(option, "tcrypt-system")) {
+ opt_type = CRYPT_TCRYPT;
+ opt_tcrypt_system = true;
+ } else if (streq(option, "plain") ||
streq(option, "swap") ||
streq(option, "tmp"))
opt_type = CRYPT_PLAIN;
@@ -301,6 +321,55 @@ static int get_password(const char *name, usec_t until, bool accept_cached, char
return 0;
}
+static int attach_tcrypt(struct crypt_device *cd,
+ const char *name,
+ const char **key_file,
+ char **passwords,
+ uint32_t flags) {
+ int r = 0;
+ _cleanup_free_ char *passphrase = NULL;
+ struct crypt_params_tcrypt params = {
+ .flags = CRYPT_TCRYPT_LEGACY_MODES,
+ .keyfiles = (const char **)opt_tcrypt_keyfiles,
+ .keyfiles_count = strv_length(opt_tcrypt_keyfiles)
+ };
+
+ assert(cd);
+ assert(name);
+ assert(key_file);
+
+ if (opt_tcrypt_hidden)
+ params.flags |= CRYPT_TCRYPT_HIDDEN_HEADER;
+
+ if (opt_tcrypt_system)
+ params.flags |= CRYPT_TCRYPT_SYSTEM_HEADER;
+
+ if (*key_file) {
+ r = read_one_line_file(*key_file, &passphrase);
+ if (r < 0) {
+ log_error("Failed to read key file: %s", strerror(-r));
+ *key_file = NULL;
+ return -EAGAIN;
+ }
+
+ params.passphrase = passphrase;
+ } else
+ params.passphrase = passwords[0];
+ params.passphrase_size = strlen(params.passphrase);
+
+ r = crypt_load(cd, CRYPT_TCRYPT, ¶ms);
+ if (r < 0) {
+ if (*key_file && r == -EPERM) {
+ log_error("Failed to activate using password file '%s'.", *key_file);
+ *key_file = NULL;
+ return -EAGAIN;
+ }
+ return r;
+ }
+
+ return crypt_activate_by_volume_key(cd, name, NULL, 0, flags);;
+}
+
static int attach_luks_or_plain(struct crypt_device *cd,
const char *name,
const char **key_file,
@@ -456,7 +525,7 @@ int main(int argc, char *argv[]) {
!streq(argv[4], "none")) {
if (!path_is_absolute(argv[4]))
- log_error("Password file path %s is not absolute. Ignoring.", argv[4]);
+ log_error("Password file path '%s' is not absolute. Ignoring.", argv[4]);
else
key_file = argv[4];
}
@@ -540,7 +609,10 @@ int main(int argc, char *argv[]) {
goto finish;
}
- k = attach_luks_or_plain(cd, argv[2], &key_file, passwords, flags);
+ if (streq_ptr(opt_type, CRYPT_TCRYPT))
+ k = attach_tcrypt(cd, argv[2], &key_file, passwords, flags);
+ else
+ k = attach_luks_or_plain(cd, argv[2], &key_file, passwords, flags);
if (k >= 0)
break;
else if (k == -EAGAIN)
@@ -590,6 +662,7 @@ finish:
free(opt_cipher);
free(opt_hash);
+ strv_free(opt_tcrypt_keyfiles);
return r;
}
--
1.8.3.2
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