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<manvolnum>5</manvolnum></citerefentry> for the root disk. The
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aim of this program is therefore to output a password, which
147
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then <citerefentry><refentrytitle>cryptsetup</refentrytitle>
148
<manvolnum>8</manvolnum></citerefentry> will use to try and
149
unlock the root disk.
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<manvolnum>8</manvolnum></citerefentry> will use to unlock the
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This program is not meant to be invoked directly, but can be in
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<option>--bar</option> with the option argument
242
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<quote>baz</quote> is either
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<userinput>--options-for=foo:--bar=baz</userinput> or
244
<userinput>--options-for=foo:--bar,baz</userinput>, but
245
<emphasis>not</emphasis>
246
<userinput>--options-for="foo:--bar baz"</userinput>.
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<userinput>--options-for=foo:--bar,baz</userinput>. Using
245
<userinput>--options-for="foo:--bar baz"</userinput>. will
246
<emphasis>not</emphasis> work.
403
403
code will make this plugin-runner output the password from that
404
404
plugin, stop any other plugins, and exit.
407
<refsect2 id="writing_plugins">
408
<title>WRITING PLUGINS</title>
410
A plugin is simply a program which prints a password to its
411
standard output and then exits with a successful (zero) exit
412
status. If the exit status is not zero, any output on
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standard output will be ignored by the plugin runner. Any
414
output on its standard error channel will simply be passed to
415
the standard error of the plugin runner, usually the system
419
The plugin will run in the initial RAM disk environment, so
420
care must be taken not to depend on any files or running
421
services not available there.
424
The plugin must exit cleanly and free all allocated resources
425
upon getting the TERM signal, since this is what the plugin
426
runner uses to stop all other plugins when one plugin has
427
output a password and exited cleanly.
430
The plugin must not use resources, like for instance reading
431
from the standard input, without knowing that no other plugins
435
It is useful, but not required, for the plugin to take the
436
<option>--debug</option> option.
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441
<refsect1 id="fallback">
513
<!-- <refsect1 id="bugs"> -->
514
<!-- <title>BUGS</title> -->
486
519
<refsect1 id="examples">
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520
<title>EXAMPLE</title>
523
Normal invocation needs no options:
526
<userinput>&COMMANDNAME;</userinput>
531
Run the program, but not the plugins, in debug mode:
535
<!-- do not wrap this line -->
536
<userinput>&COMMANDNAME; --debug</userinput>
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Run all plugins, but run the <quote>foo</quote> plugin in
547
<!-- do not wrap this line -->
548
<userinput>&COMMANDNAME; --options-for=foo:--debug</userinput>
554
Run all plugins, but not the program, in debug mode:
558
<!-- do not wrap this line -->
559
<userinput>&COMMANDNAME; --global-options=--debug</userinput>
565
Run plugins from a different directory and add a special
566
option to the <citerefentry><refentrytitle
567
>password-request</refentrytitle>
568
<manvolnum>8mandos</manvolnum></citerefentry> plugin:
572
<!-- do not wrap this line -->
573
<userinput>&COMMANDNAME; --plugin-dir=plugins.d --options-for=password-request:--keydir=keydir</userinput>
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578
<refsect1 id="security">
493
579
<title>SECURITY</title>
581
This program will, when starting, try to switch to another user.
582
If it is started as root, it will succeed, and will by default
583
switch to user and group 65534, which are assumed to be
584
non-privileged. This user and group is then what all plugins
585
will be started as. Therefore, the only way to run a plugin as
586
a privileged user is to have the set-user-ID or set-group-ID bit
587
set on the plugin executable files (see <citerefentry>
588
<refentrytitle>execve</refentrytitle><manvolnum>2</manvolnum>
592
If this program is used as a keyscript in <citerefentry
593
><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
594
</citerefentry>, there is a risk that if this program fails to
595
work, there might be no way to boot the system except for
596
booting from another media and editing the initial RAM disk
597
image to not run this program. This is, however, unlikely,
598
since the <citerefentry><refentrytitle
599
>password-prompt</refentrytitle><manvolnum>8mandos</manvolnum>
600
</citerefentry> plugin will read a password from the console in
601
case of failure of the other plugins, and this plugin runner
602
will also, in case of catastrophic failure, itself fall back to
603
asking and outputting a password on the console (see <xref
604
linkend="fallback"/>).
501
611
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
502
612
<manvolnum>8</manvolnum></citerefentry>,
613
<citerefentry><refentrytitle>crypttab</refentrytitle>
614
<manvolnum>5</manvolnum></citerefentry>,
615
<citerefentry><refentrytitle>execve</refentrytitle>
616
<manvolnum>2</manvolnum></citerefentry>,
503
617
<citerefentry><refentrytitle>mandos</refentrytitle>
504
618
<manvolnum>8</manvolnum></citerefentry>,
505
619
<citerefentry><refentrytitle>password-prompt</refentrytitle>