sbin/tcplay/tcplay.8

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.Dd April 30, 2020
.Dt TCPLAY 8
.Os
.Sh NAME
.Nm tcplay
.Nd tool to manage TrueCrypt volumes
.Sh SYNOPSIS
.Nm
.Fl c
.Fl d Ar device
.Op Fl g
.Op Fl z
.Op Fl w
.Op Fl a Ar pbkdf_hash
.Op Fl b Ar cipher
.Op Fl f Ar keyfile_hidden
.Op Fl k Ar keyfile
.Op Fl x Ar pbkdf_hash
.Op Fl y Ar cipher
.Op Fl -fde
.Nm
.Fl i
.Fl d Ar device
.Op Fl e
.Op Fl p
.Op Fl f Ar keyfile_hidden
.Op Fl k Ar keyfile
.Op Fl s Ar system_device
.Op Fl -use-backup
.Op Fl -use-hdr-file Ar hdr_file
.Op Fl -use-hidden-hdr-file Ar hdr_file
.Nm
.Fl j Ar mapping
.Nm
.Fl m Ar mapping
.Fl d Ar device
.Op Fl e
.Op Fl p
.Op Fl f Ar keyfile_hidden
.Op Fl k Ar keyfile
.Op Fl s Ar system_device
.Op Fl t
.Op Fl -fde
.Op Fl -use-backup
.Op Fl -use-hdr-file Ar hdr_file
.Op Fl -use-hidden-hdr-file Ar hdr_file
.Nm
.Fl -modify
.Fl d Ar device
.Op Fl k Ar keyfile
.Op Fl -new-keyfile Ar new_keyfile
.Op Fl -new-pbkdf-prf Ar pbkdf_hash
.Op Fl s Ar system_device
.Op Fl -fde
.Op Fl -use-backup
.Op Fl -use-hdr-file Ar hdr_file
.Op Fl -use-hidden-hdr-file Ar hdr_file
.Op Fl -save-hdr-backup Ar hdr_file
.Op Fl w
.Nm
.Fl -modify
.Fl d Ar device
.Op Fl k Ar keyfile
.Fl -restore-from-backup-hdr
.Op Fl w
.Nm
.Fl u Ar mapping
.Nm
.Fl h | v
.Sh DESCRIPTION
The
.Nm
utility provides full support for creating and opening/mapping
TrueCrypt-compatible volumes.
It supports the following commands, each with a set of options
detailed further below:
.Bl -tag -width indent
.It Fl c , Fl -create
Create a new encrypted TrueCrypt volume on the device
specified by
.Fl -device .
.It Fl h , Fl -help
Print help message and exit.
.It Fl i , Fl -info
Print out information about the encrypted device specified by
.Fl -device .
.It Fl j Ar mapping , Fl -info-mapped Ns = Ns Ar mapping
Print out information about the mapped tcplay volume specified
by
.Ar mapping .
Information such as key CRC and the PBKDF2 PRF is not available
via this command.
.It Fl -modify
Modify the volume header.
This mode allows changing passphrase, keyfiles, PBKDF2 PRF as
well as restoring from a backup header.
.It Fl m Ar mapping , Fl -map Ns = Ns Ar mapping
Map the encrypted TrueCrypt volume on the device specified by
.Fl -device
as a
.Xr dm 4
mapping called
.Ar mapping .
The
.Ar mapping
argument should not contain any spaces or special characters.
.It Fl u Ar mapping , Fl -unmap Ns = Ns Ar mapping
Removes (unmaps) the
.Xr dm 4
mapping specified by
.Ar mapping
as well as any related cascade mappings.
.It Fl v , Fl -version
Print version message and exit.
.El
.Pp
Options common to all commands are:
.Bl -tag -width indent
.It Fl d Ar device , Fl -device Ns = Ns Ar device
Specifies the disk
.Ar device
on which the TrueCrypt volume resides/will reside.
This option is mandatory for all commands.
.It Fl f Ar keyfile_hidden , Fl -keyfile-hidden Ns = Ns Ar keyfile_hidden
Specifies a keyfile
to use in addition to the passphrase when either creating a
hidden volume or when protecting a hidden volume while mapping
or querying the outer volume.
If you only intend to map a hidden volume, the
.Fl -keyfile
option has to be used.
This option can appear multiple times; if so, multiple
keyfiles will be used.
This option is not valid in the
.Fl -modify
mode.
.It Fl k Ar keyfile , Fl -keyfile Ns = Ns Ar keyfile
Specifies a
.Ar keyfile
to use in addition to the passphrase.
This option can appear multiple times; if so, multiple
keyfiles will be used.
.El
.Pp
Additional options for the
.Fl -create
command are:
.Bl -tag -width indent
.It Fl a Ar pbkdf_hash , Fl -pbkdf-prf Ns = Ns Ar pbkdf_hash
Specifies which hash algorithm to use for the PBKDF2 password
derivation.
To see which algorithms are supported, specify
.Fl -pbkdf-prf Ns = Ns Cm help .
.It Fl b Ar cipher , Fl -cipher Ns = Ns Ar cipher
Specifies which cipher algorithm or cascade of ciphers to use
to encrypt the new volume.
To see which algorithms are supported, specify
.Fl -cipher Ns = Ns Cm help .
.It Fl g , Fl -hidden
Specifies that the newly created volume will contain a hidden
volume.
The keyfiles applied to the passphrase for the hidden
volume are those specified by
.Fl -keyfile-hidden .
The user will be prompted for the size of the hidden volume
interactively.
.It Fl w , Fl -weak-keys
Use
.Xr urandom 4
for key material instead of a strong entropy source.
This is in general a really bad idea and should only be used
for testing.
.It Fl x Ar pbkdf_hash , Fl -pbkdf-prf-hidden Ns = Ns Ar pbkdf_hash
Specifies which hash algorithm to use for the PBKDF2 password
derivation for the hidden volume.
Only valid in conjunction with
.Fl -hidden .
If no algorithm is specified, the same as for the outer volume
will be used.
To see which algorithms are supported, specify
.Fl -pbkdf-prf-hidden Ns = Ns Cm help .
.It Fl y Ar cipher , Fl -cipher-hidden Ns = Ns Ar cipher
Specifies which cipher algorithm or cascade of ciphers to use
to encrypt the hidden volume on the new TrueCrypt volume.
Only valid in conjunction with
.Fl -hidden .
If no cipher is specified, the same as for the outer volume
will be used.
To see which algorithms are supported, specify
.Fl -cipher-hidden Ns = Ns Cm help .
.It Fl z , Fl -insecure-erase
Skips the secure erase of the disk.
Use this option carefully as it is a security risk!
.El
.Pp
Additional options for the
.Fl -info ,
.Fl -map
and
.Fl -modify
commands are:
.Bl -tag -width indent
.It Fl e , Fl -protect-hidden
Specifies that an outer volume will be queried or mapped, but
its reported size will be adjusted accordingly to the size of
the hidden volume contained in it.
Both the hidden volume and outer volume passphrase and keyfiles
will be required.
This option only applies to the
.Fl -info
and
.Fl -map
commands.
.It Fl p, Fl -prompt-passphrase
This option causes
.Nm
to prompt for a passphrase immediately, even if a keyfile is
provided.
Normally, if a keyfile is supplied,
.Nm
will first attempt to unlock the volume using only the keyfile,
and only prompt for a passphrase if that first unlocking attempt
fails.
However, since a failed unlocking attempt can take a non-trivial
amount of time, specifying this option can reduce the total unlocking
time if both a keyfile and passphrase are required.
This option only makes sense if
.Fl k
or
.Fl f
are used.
.It Fl s Ar system_device , Fl -system-encryption Ns = Ns Ar system_device
This option is required if you are attempting to access a device
that uses system encryption, for example an encrypted
.Tn Windows
system partition.
It does not apply to disks using full disk encryption.
The
.Fl -device
option will point at the actual encrypted partition, while the
.Ar system_device
argument will point to the parent device (i.e.\& underlying physical disk)
of the encrypted partition.
.It Fl -fde
This option is intended to be used with disks using full disk encryption (FDE).
When a disk has been encrypted using TrueCrypt's FDE, the complete disk
is encrypted except for the first 63 sectors.
The
.Fl -device
option should point to the whole disk device, not to any particular
partition.
The resultant mapping will cover the whole disk, and will not appear as
separate partitions.
.It Fl -use-backup
This option is intended to be used when the primary headers of a volume
have been corrupted.
This option will force
.Nm
to use the backup headers, which are located at the end of the device,
to access the volume.
.El
.Pp
Additional options only for the
.Fl -map
command are:
.Bl -tag -width indent
.It Fl t , Fl -allow-trim
This option enables TRIM (discard) support on the mapped volume.
.El
.Pp
Additional options only for the
.Fl -modify
command are:
.Bl -tag -width indent
.It Fl -new-pbkdf-prf Ns = Ns Ar pbkdf_hash
Specifies which hash algorithm to use for the PBKDF2 password
derivation on reencrypting the volume header.
If this option is not specified, the reencrypted header will
use the current PRF.
To see which algorithms are supported, specify
.Fl -pbkdf-prf Ns = Ns Cm help .
.It Fl -new-keyfile Ns = Ns Ar keyfile
Specifies a
.Ar keyfile
to use in addition to the new passphrase on reencrypting the
volume header.
This option can appear multiple times; if so, multiple
keyfiles will be used.
.It Fl -restore-from-backup-hdr
If this option is specified, neither
.Fl -new-pbkdf-prf
nor
.Fl -new-keyfile
should be specified.
This option implies
.Fl -use-backup .
Use this option to restore the volume headers from the backup
header.
.El
.Pp
Sending a
.Dv SIGINFO
or
.Dv SIGUSR1
signal to a running
.Nm
process makes it print progress on slower tasks
such as gathering entropy or wiping the volume.
.Sh NOTES
TrueCrypt limits passphrases to 64 characters (including the terminating
null character).
To be compatible with it,
.Nm
does the same.
All passphrases (excluding keyfiles) are trimmed to 64 characters.
Similarly, keyfiles are limited to a size of 1 MB, but up to
256 keyfiles can be used.
.Sh PLAUSIBLE DENIABILITY
.Nm
offers plausible deniability. Hidden volumes are created within an outer
volume.
Which volume is accessed solely depends on the passphrase and keyfile(s)
used.
If the passphrase and keyfiles for the outer volume are specified,
no information about the existence of the hidden volume is exposed.
Without knowledge of the passphrase and keyfile(s) of the hidden volume
its existence remains unexposed.
The hidden volume can be protected when mapping the outer volume by
using the
.Fl -protect-hidden
option and specifying the passphrase and keyfiles for both the outer
and hidden volumes.
.Sh VERACRYPT SUPPORT
.Nm
offers both legacy TrueCrypt as well as VeraCrypt support.
When creating a new volume, the selected PBKDF2 PRF determines whether
the volume will use the TrueCrypt or VeraCrypt format.
The formats are identical other than the rounds of the key derivation
functions as well as the volume signature and minver fields in the
header.
Converting volumes from one format or another using
.Nm
is simply a matter of using the
.Fl -modify
option specifying a PBKDF2 PRF hash matching the intended target format
with the
.Fl -new-pbkdf-prf
argument.
.Pp
PBKDF2 PRFs suffixed with
.Dv -VC
are VeraCrypt PRFs, whilst all others are legacy TrueCrypt PRFs.
By default, new volumes are created with a VeraCrypt PRF to offer better
security.
.Pp
NOTE: Failed unlocking attempts even for legacy TrueCrypt volumes now take
significantly longer than before, as
.Nm
will cycle through all PRFs, including the VeraCrypt PRFs with much higher
number of PRF iterations.
Successful attempts should still take the same amount of time as before, as
the legacy PRF settings are tried first.
One notable exception is if both a keyfile and a passphrase is required.
Normally,
.Nm
would first attempt an unlock attempt with just the keyfile, and only prompt
for a passphrase after that attempt failed.
If it is known in advance that both a keyfile and passphrase are required to
unlock a volume, the
.Fl p
option to
.Fl -info
and
.Fl -map
can more than halve the time required to unlock the volume.
.Sh EXAMPLES
Create a new TrueCrypt volume on
.Pa /dev/vn0
using the cipher cascade
of AES and Twofish and the Whirlpool hash algorithm for
PBKDF2 password derivation and two keyfiles,
.Pa one.key
and
.Pa two.key :
.Bd -ragged -offset indent
.Nm Fl -create
.Fl -device Ns = Ns Cm /dev/vn0
.Fl -cipher Ns = Ns Cm TWOFISH-256-XTS,AES-256-XTS
.Fl -pbkdf-prf Ns = Ns Cm whirlpool
.Fl -keyfile Ns = Ns Cm one.key
.Fl -keyfile Ns = Ns Cm two.key
.Ed
.Pp
Map the outer volume on the TrueCrypt volume on
.Pa /dev/vn0
as
.Sy truecrypt1 ,
but protect the hidden volume, using the keyfile
.Pa hidden.key ,
from being overwritten:
.Bd -ragged -offset indent
.Nm Fl -map Ns = Ns Cm truecrypt1
.Fl -device Ns = Ns Cm /dev/vn0
.Fl -protect-hidden
.Fl -keyfile-hidden Ns = Ns Cm hidden.key
.Ed
.Pp
Map the hidden volume on the TrueCrypt volume on
.Pa /dev/vn0
as
.Sy truecrypt2 ,
using the keyfile
.Pa hidden.key :
.Bd -ragged -offset indent
.Nm Fl -map Ns = Ns Cm truecrypt2
.Fl -device Ns = Ns Cm /dev/vn0
.Fl -keyfile Ns = Ns Cm hidden.key
.Ed
.Pp
Map and mount the volume in the file
.Pa secvol :
.Bd -ragged -offset indent
.Sy vnconfig Cm vn1 Cm secvol
.Ed
.Bd -ragged -offset indent
.Nm Fl -map Ns = Ns Cm secv
.Fl -device Ns = Ns Cm /dev/vn1
.Ed
.Bd -ragged -offset indent
.Sy mount Cm /dev/mapper/secv Cm /mnt
.Ed
.Pp
Unmapping the volume
.Sy truecrypt2
after unmounting:
.Bd -ragged -offset indent
.Sy dmsetup Cm remove Cm truecrypt2
.Ed
.Pp
Or alternatively:
.Bd -ragged -offset indent
.Nm Fl -unmap Ns = Ns Cm truecrypt2
.Ed
.Pp
A hidden volume whose existence can be plausibly denied and its outer volume
can for example be created with
.Bd -ragged -offset indent
.Nm Fl -create
.Fl -hidden
.Fl -device Ns = Ns Cm /dev/vn0
.Fl -cipher Ns = Ns Cm TWOFISH-256-XTS,AES-256-XTS
.Fl -pbkdf-prf Ns = Ns Cm whirlpool
.Fl -keyfile Ns = Ns Cm one.key
.Fl -cipher-hidden Ns = Ns Cm AES-256-XTS
.Fl -pbkdf-prf-hidden Ns = Ns Cm whirlpool
.Fl -keyfile-hidden Ns = Ns Cm hidden.key
.Ed
.Pp
.Nm
will prompt the user for the passphrase for both the outer and hidden volume
as well as the size of the hidden volume inside the outer volume.
The hidden volume will be created inside the area spanned by the outer volume.
The hidden volume can optionally use a different cipher and prf function
as specified by the
.Fl -cipher-hidden
and
.Fl -pbkdf-prf-hidden
options.
Which volume is later accessed depends only on which passphrase and keyfile(s)
are being used,
so that the existence of the hidden volume remains unknown without knowledge
of the passphrase and keyfile it is protected by since it is located within
the outer volume.
To map the outer volume without potentially damaging the hidden volume,
the passphrase and keyfile(s) of the hidden volume must be known and provided
alongside the
.Fl -protect-hidden
option.
.Pp
A disk encrypted using full disk encryption can be mapped using
.Bd -ragged -offset indent
.Nm Fl -map Ns = Ns Cm tcplay_da2
.Fl -device Ns = Ns Cm /dev/da2
.Fl -fde
.Ed
.Pp
To restore the main volume header from the backup header, the following
command can be used:
.Bd -ragged -offset indent
.Nm Fl -modify
.Fl -device Ns = Ns Cm /dev/da2
.Fl -restore-from-backup-hdr
.Ed
.Pp
As with most other commands, which header is saved (used as source) depends
on the passphrase and keyfiles used.
.Pp
To save a backup copy of a header, the following command can be used:
.Bd -ragged -offset indent
.Nm Fl -modify
.Fl -device Ns = Ns Cm /dev/da2
.Fl -save-hdr-backup Ns = Ns Cm /tmp/da2_backup_header.hdr
.Ed
.Pp
As with most other commands, which header is saved (used as source) depends
on the passphrase and keyfiles used.
.Pp
To restore a header from a backup header file, the following command can be
used:
.Bd -ragged -offset indent
.Nm Fl -modify
.Fl -device Ns = Ns Cm /dev/da2
.Fl -use-hdr-file Ns = Ns Cm /tmp/da2_backup_header.hdr
.Ed
.Pp
Similarly, to restore a hidden header from a backup header file:
.Bd -ragged -offset indent
.Nm Fl -modify
.Fl -device Ns = Ns Cm /dev/da2
.Fl -use-hidden-hdr-file Ns = Ns Cm /tmp/da2_backup_hidden_header.hdr
.Ed
.Pp
Which header is used as the source of the operation will still depend on the
passphrase and keyfiles used.
Even if you use the
.Fl -use-hidden-hdr-file
option, if you specify the passphrase and keyfiles for the main header, the
main header will be used instead.
.Sh SEE ALSO
.Xr crypttab 5 ,
.Xr cryptsetup 8 ,
.Xr dmsetup 8
.Sh HISTORY
The
.Nm
utility appeared in
.Dx 2.11 .
.Sh AUTHORS
.An Alex Hornung