140
140
<title>DESCRIPTION</title>
142
142
<command>&COMMANDNAME;</command> is a program which is meant to
143
be specified as a <quote>keyscript</quote> for the root disk in
144
<citerefentry><refentrytitle>crypttab</refentrytitle>
145
<manvolnum>5</manvolnum></citerefentry>. The aim of this
146
program is therefore to output a password, which then
147
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
148
<manvolnum>8</manvolnum></citerefentry> will use to unlock the
143
be specified as <quote>keyscript</quote> in <citerefentry>
144
<refentrytitle>crypttab</refentrytitle>
145
<manvolnum>5</manvolnum></citerefentry> for the root disk. The
146
aim of this program is therefore to output a password, which
147
then <citerefentry><refentrytitle>cryptsetup</refentrytitle>
148
<manvolnum>8</manvolnum></citerefentry> will use to try and
149
unlock the root disk.
152
152
This program is not meant to be invoked directly, but can be in
241
241
<option>--bar</option> with the option argument
242
242
<quote>baz</quote> is either
243
243
<userinput>--options-for=foo:--bar=baz</userinput> or
244
<userinput>--options-for=foo:--bar,baz</userinput>. Using
245
<userinput>--options-for="foo:--bar baz"</userinput>. will
246
<emphasis>not</emphasis> work.
244
<userinput>--options-for=foo:--bar,baz</userinput>, but
245
<emphasis>not</emphasis>
246
<userinput>--options-for="foo:--bar baz"</userinput>.
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
413
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 plugin
435
It is useful, but not required, for the plugin to take the
436
<option>--debug</option> option.
441
408
<refsect1 id="fallback">
513
480
<refsect1 id="bugs">
514
481
<title>BUGS</title>
516
The <option>--config-file</option> option is ignored when
517
specified from within a configuration file.
521
486
<refsect1 id="examples">
522
487
<title>EXAMPLE</title>
525
Normal invocation needs no options:
528
<userinput>&COMMANDNAME;</userinput>
533
Run the program, but not the plugins, in debug mode:
537
<!-- do not wrap this line -->
538
<userinput>&COMMANDNAME; --debug</userinput>
544
Run all plugins, but run the <quote>foo</quote> plugin in
549
<!-- do not wrap this line -->
550
<userinput>&COMMANDNAME; --options-for=foo:--debug</userinput>
556
Run all plugins, but not the program, in debug mode:
560
<!-- do not wrap this line -->
561
<userinput>&COMMANDNAME; --global-options=--debug</userinput>
567
Run plugins from a different directory, read a different
568
configuration file, and add two options to the
569
<citerefentry><refentrytitle >password-request</refentrytitle>
570
<manvolnum>8mandos</manvolnum></citerefentry> plugin:
574
<!-- do not wrap this line -->
575
<userinput>&COMMANDNAME; --config-file=/etc/mandos/plugin-runner.conf --plugin-dir /usr/lib/mandos/plugins.d --options-for=password-request:--pubkey=/etc/keys/mandos/pubkey.txt,--seckey=/etc/keys/mandos/seckey.txt</userinput>
580
492
<refsect1 id="security">
581
493
<title>SECURITY</title>
583
This program will, when starting, try to switch to another user.
584
If it is started as root, it will succeed, and will by default
585
switch to user and group 65534, which are assumed to be
586
non-privileged. This user and group is then what all plugins
587
will be started as. Therefore, the only way to run a plugin as
588
a privileged user is to have the set-user-ID or set-group-ID bit
589
set on the plugin executable file (see <citerefentry>
590
<refentrytitle>execve</refentrytitle><manvolnum>2</manvolnum>
594
If this program is used as a keyscript in <citerefentry
595
><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
596
</citerefentry>, there is a slight risk that if this program
597
fails to work, there might be no way to boot the system except
598
for booting from another media and editing the initial RAM disk
599
image to not run this program. This is, however, unlikely,
600
since the <citerefentry><refentrytitle
601
>password-prompt</refentrytitle><manvolnum>8mandos</manvolnum>
602
</citerefentry> plugin will read a password from the console in
603
case of failure of the other plugins, and this plugin runner
604
will also, in case of catastrophic failure, itself fall back to
605
asking and outputting a password on the console (see <xref
606
linkend="fallback"/>).
613
501
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
614
502
<manvolnum>8</manvolnum></citerefentry>,
615
<citerefentry><refentrytitle>crypttab</refentrytitle>
616
<manvolnum>5</manvolnum></citerefentry>,
617
<citerefentry><refentrytitle>execve</refentrytitle>
618
<manvolnum>2</manvolnum></citerefentry>,
619
503
<citerefentry><refentrytitle>mandos</refentrytitle>
620
504
<manvolnum>8</manvolnum></citerefentry>,
621
505
<citerefentry><refentrytitle>password-prompt</refentrytitle>