NAME

       nbdkit-protect-filter - write-protect parts of a plugin

SYNOPSIS

        nbdkit --filter=protect plugin protect=START-END [protect=...]

DESCRIPTION

       "nbdkit-protect-filter" is a filter for nbdkit(1) that lets you write-protect parts of the underlying
       plugin.  This prevents clients from modifying ranges of the plugin, while still allowing the NBD
       connection to be writable in general.

       One use for this is to prevent clients from adding a phony header to the data to make it look like a non-
       raw disk format (like adding a qcow2 header), since that can be used in some exploits.

       To make the whole plugin readonly, use the nbdkit -r option on the command line.  To give selective
       access to the server, use nbdkit-ip-filter(1).  To serve only a subset of the plugin use
       nbdkit-offset-filter(1) or nbdkit-partition-filter(1).

EXAMPLES

   Protect the boot sector
       Protect the first part of the boot sector from writes, but allow the MBR partition table to be updated:

        nbdkit --filter=protect file disk.img protect=0-0x1bd

   Protect everything except a single partition
       Allow clients to write to a single partition on the disk, but prevent modifications to the partition
       table, boot sector, other partitions, or any other metadata outside the partition:

        $ fdisk -l disk.img
        Device    Boot  Start       End  Sectors Size Id Type
        disk.img1 *      2048  12580863 12578816   6G 83 Linux
        $ start=$((2048*512))
        $ end=$((12580863*512+511))
        $ nbdkit --filter=protect file disk.img protect=~$start-$end

       Notes:

       •   Data in other partitions and parts of the disk is still readable.

       •   The  '~' character complements the range protected.  You might need to escape it from the shell using
           quotes or backslash.

       •   This is different from nbdkit-partition-filter(1) — that filter exposes  the  partition  as  a  whole
           device.

PARAMETERS

       protect=START-END
           Protect  the  bytes  starting  at  offset  "START"  through  to  offset "END" (inclusive).  Reads are
           permitted.  Writes to the protected range are only permitted if they do not change the  content.   If
           an  attempt  is  made  to change the content, then the error "NBD_EPERM" (Operation not permitted) is
           returned to the client.

           "START" and "END" can be expressed in decimal, octal ("0NN") or  hexadecimal  ("0xNN").   If  omitted
           then they default to the start and end of the underlying plugin respectively.

           This parameter can be given multiple times to protect several ranges.

       protect=~START-END
           This protects the complement of the range "START" to "END".

FILES

       $filterdir/nbdkit-protect-filter.so
           The filter.

           Use "nbdkit --dump-config" to find the location of $filterdir.

VERSION

       "nbdkit-protect-filter" first appeared in nbdkit 1.30.

SEE ALSO

       nbdkit(1),          nbdkit-file-plugin(1),          nbdkit-ip-filter(1),         nbdkit-offset-filter(1),
       nbdkit-partition-filter(1), nbdkit-filter(3).

AUTHORS

       Richard W.M. Jones

COPYRIGHT

       Copyright Red Hat

LICENSE

       Redistribution and use in source and binary forms, with or without modification, are  permitted  provided
       that the following conditions are met:

       •   Redistributions  of  source  code must retain the above copyright notice, this list of conditions and
           the following disclaimer.

       •   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.

       •   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.

       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
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       DAMAGE.

nbdkit-1.36.3                                      2024-03-31                           nbdkit-protect-filter(1)