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.\"
.IX Title "nbdkit-luks-filter 1"
.TH nbdkit-luks-filter 1 2024-04-21 nbdkit-1.38.1 NBDKIT
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH NAME
nbdkit\-luks\-filter \- read and write LUKS\-encrypted disks and partitions
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& nbdkit file encrypted\-disk.img \-\-filter=luks passphrase=+/tmp/secret
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\f(CW\*(C`nbdkit\-luks\-filter\*(C'\fR is a filter for \fBnbdkit\fR\|(1) which transparently
opens a LUKS-encrypted disk image.  LUKS ("Linux Unified Key Setup")
is the Full Disk Encryption (FDE) system commonly used by Linux
systems.  This filter is compatible with LUKSv1 as implemented by the
Linux kernel (dm_crypt), and by qemu.
.PP
You can place this filter on top of \fBnbdkit\-file\-plugin\fR\|(1) to
decrypt a local file:
.PP
.Vb 1
\& nbdkit file encrypted\-disk.img \-\-filter=luks passphrase=+/tmp/secret
.Ve
.PP
If LUKS is present inside a partition in the disk image then you will
have to combine this filter with \fBnbdkit\-partition\-filter\fR\|(1).  The
order of the filters is important:
.PP
.Vb 3
\& nbdkit file encrypted\-disk.img \e
\&             \-\-filter=luks passphrase=+/tmp/secret \e
\&             \-\-filter=partition partition=1
.Ve
.PP
This filter also works on top of other plugins such as
\&\fBnbdkit\-curl\-plugin\fR\|(1):
.PP
.Vb 2
\& nbdkit curl https://example.com/encrypted\-disk.img \e
\&             \-\-filter=luks passphrase=+/tmp/secret
.Ve
.PP
The web server sees only the encrypted data.  Without knowing the
passphrase, the web server cannot access the decrypted disk.  Only
encrypted data is sent over the HTTP connection.  nbdkit itself will
serve \fIunencrypted\fR disk data over the NBD connection (if this is a
problem see \fBnbdkit\-tls\fR\|(1), or use a Unix domain socket \fI\-U\fR).
.PP
The passphrase can be stored in a file (as shown), passed directly on
the command line (insecure), entered interactively, or passed to
nbdkit over a file descriptor.
.PP
This filter can read and write LUKSv1.  It cannot create disks, change
passphrases, add keyslots, etc.  To do that, you can use ordinary
Linux tools like \fBcryptsetup\fR\|(8).  Note you must force LUKSv1
(eg. using cryptsetup \fI\-\-type luks1\fR).  \fBqemu\-img\fR\|(1) can also
create compatible disk images:
.PP
.Vb 4
\& qemu\-img create \-f luks \e
\&                 \-\-object secret,data=SECRET,id=sec0 \e
\&                 \-o key\-secret=sec0 \e
\&                 encrypted\-disk.img 1G
.Ve
.SH PARAMETERS
.IX Header "PARAMETERS"
.IP \fBpassphrase=\fRSECRET 4
.IX Item "passphrase=SECRET"
Use the secret passphrase when decrypting the disk.
.Sp
Note that passing this on the command line is not secure on shared
machines.
.IP \fBpassphrase=\-\fR 4
.IX Item "passphrase=-"
Ask for the passphrase (interactively) when nbdkit starts up.
.IP \fBpassphrase=+\fRFILENAME 4
.IX Item "passphrase=+FILENAME"
Read the passphrase from the named file.  This is a secure method to
supply a passphrase, as long as you set the permissions on the file
appropriately.
.IP \fBpassphrase=\-\fRFD 4
.IX Item "passphrase=-FD"
Read the passphrase from file descriptor number \f(CW\*(C`FD\*(C'\fR, inherited from
the parent process when nbdkit starts up.  This is also a secure
method to supply a passphrase.
.SH FILES
.IX Header "FILES"
.ie n .IP \fR\fI$filterdir\fR\fI/nbdkit\-luks\-filter.so\fR 4
.el .IP \fR\f(CI$filterdir\fR\fI/nbdkit\-luks\-filter.so\fR 4
.IX Item "$filterdir/nbdkit-luks-filter.so"
The plugin.
.Sp
Use \f(CW\*(C`nbdkit \-\-dump\-config\*(C'\fR to find the location of \f(CW$filterdir\fR.
.SH VERSION
.IX Header "VERSION"
\&\f(CW\*(C`nbdkit\-luks\-filter\*(C'\fR first appeared in nbdkit 1.32.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbdkit\-curl\-plugin\fR\|(1),
\&\fBnbdkit\-file\-plugin\fR\|(1),
\&\fBnbdkit\-ip\-filter\fR\|(1),
\&\fBnbdkit\-partition\-filter\fR\|(1),
\&\fBnbdkit\fR\|(1),
\&\fBnbdkit\-tls\fR\|(1),
\&\fBnbdkit\-plugin\fR\|(3),
\&\fBcryptsetup\fR\|(8),
\&\fBqemu\-img\fR\|(1).
.SH AUTHORS
.IX Header "AUTHORS"
Richard W.M. Jones
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright Red Hat
.SH LICENSE
.IX Header "LICENSE"
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
.IP \(bu 4
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
.IP \(bu 4
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
.IP \(bu 4
Neither the name of Red Hat nor the names of its contributors may be
used to endorse or promote products derived from this software without
specific prior written permission.
.PP
THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.