plugin-runner — Run Mandos plugins, pass data from first to succeed.
plugin-runner
[ --global-env=
| ENV
=
value
-G
...]ENV
=
value
[ --env-for=
| PLUGIN
:
ENV
=
value
-E
...]
PLUGIN
:
ENV
=
value
[ --global-options=
| OPTIONS
-g
...]
OPTIONS
[ --options-for=
| PLUGIN
:
OPTIONS
-o
...]
PLUGIN
:
OPTIONS
[ --disable=
| PLUGIN
-d
...]PLUGIN
[ --enable=
| PLUGIN
-e
...]PLUGIN
[--groupid=
]ID
[--userid=
]ID
[--plugin-dir=
]DIRECTORY
[--plugin-helper-dir=
]DIRECTORY
[--config-file=
]FILE
[--debug
]
plugin-runner
{ --help
| -?
}
plugin-runner
--usage
plugin-runner
{ --version
| -V
}
plugin-runner is a program which is meant to be specified as a “keyscript” for the root disk in crypttab(5). The aim of this program is therefore to output a password, which then cryptsetup(8) will use to unlock the root disk.
This program is not meant to be invoked directly, but can be in order to test it. Note that any password obtained will simply be output on standard output.
The purpose of this is to enable remote and unattended rebooting of client host computer with an encrypted root file system. See the section called “OVERVIEW” for details.
--global-env
ENV
=
value
, -G
ENV
=
value
This option will add an environment variable setting to all plugins. This will override any inherited environment variable.
--env-for
PLUGIN
:
ENV
=
value
, -E
PLUGIN
:
ENV
=
value
This option will add an environment variable setting to
the PLUGIN
plugin. This will
override any inherited environment variables or
environment variables specified using
--global-env
.
--global-options
OPTIONS
, -g
OPTIONS
Pass some options to all plugins.
OPTIONS
is a comma separated
list of options. This is not a very useful option, except
for specifying the “--debug
”
option to all plugins.
--options-for
PLUGIN
:
OPTION
, -o
PLUGIN
:
OPTION
Pass some options to a specific plugin. PLUGIN
is the name (file basename) of a
plugin, and OPTIONS
is a comma
separated list of options.
Note that since options are not split on whitespace, the
way to pass, to the plugin
“foo
”, the option
--bar
with the option argument
“baz” is either
--options-for=foo:--bar=baz
or
--options-for=foo:--bar,baz
. Using
--options-for="foo:--bar baz"
. will
not work.
--disable
PLUGIN
, -d
PLUGIN
Disable the plugin named
PLUGIN
. The plugin will not be
started.
--enable
PLUGIN
, -e
PLUGIN
Re-enable the plugin named
PLUGIN
. This is only useful to
undo a previous --disable
option, maybe
from the configuration file.
--groupid
ID
Change to group ID ID
on
startup. The default is 65534. All plugins will be
started using this group ID. Note:
This must be a number, not a name.
--userid
ID
Change to user ID ID
on
startup. The default is 65534. All plugins will be
started using this user ID. Note:
This must be a number, not a name.
--plugin-dir
DIRECTORY
Specify a different plugin directory. The default is
/lib/mandos/plugins.d
, which will
exist in the initial RAM disk
environment.
--plugin-helper-dir
DIRECTORY
Specify a different plugin helper directory. The default
is /lib/mandos/plugin-helpers
, which
will exist in the initial RAM disk
environment. (This will simply be passed to all plugins
via the MANDOSPLUGINHELPERDIR
environment
variable. See the section called “WRITING PLUGINS”)
--config-file
FILE
Specify a different file to read additional options from. See the section called “FILES”. Other command line options will override options specified in the file.
--debug
Enable debug mode. This will enable a lot of output to standard error about what the program is doing. The program will still perform all other functions normally. The default is to not run in debug mode.
The plugins will not be affected by
this option. Use
if complete debugging eruption is desired.
--global-options=--debug
--help
, -?
Gives a help message about options and their meanings.
--usage
Gives a short usage message.
--version
, -V
Prints the program version.
This is part of the Mandos system for allowing computers to have encrypted root file systems and at the same time be capable of remote and/or unattended reboots. The computers run a small client program in the initial RAM disk environment which will communicate with a server over a network. All network communication is encrypted using TLS. The clients are identified by the server using a TLS key; each client has one unique to it. The server sends the clients an encrypted password. The encrypted password is decrypted by the clients using a separate OpenPGP key, and the password is then used to unlock the root file system, whereupon the computers can continue booting normally.
This program will run on the client side in the initial RAM disk environment, and is responsible for getting a password. It does this by running plugins, one of which will normally be the actual client program communicating with the server.
This program will get a password by running a number of
plugins, which are executable programs in
a directory in the initial RAM disk
environment. The default directory is
/lib/mandos/plugins.d
, but this can be
changed with the --plugin-dir
option. The
plugins are started in parallel, and the first plugin to output
a password and exit with a successful exit
code will make this plugin-runner output the password from that
plugin, stop any other plugins, and exit.
A plugin is an executable program which prints a password to its standard output and then exits with a successful (zero) exit status. If the exit status is not zero, any output on standard output will be ignored by the plugin runner. Any output on its standard error channel will simply be passed to the standard error of the plugin runner, usually the system console.
If the password is a single-line, manually entered passprase, a final trailing newline character should not be printed.
The plugin will run in the initial RAM disk environment, so
care must be taken not to depend on any files or running
services not available there. Any helper executables required
by the plugin (which are not in the PATH
) can
be placed in the plugin helper directory, the name of which
will be made available to the plugin via the
MANDOSPLUGINHELPERDIR
environment variable.
The plugin must exit cleanly and free all allocated resources upon getting the TERM signal, since this is what the plugin runner uses to stop all other plugins when one plugin has output a password and exited cleanly.
The plugin must not use resources, like for instance reading from the standard input, without knowing that no other plugin is also using it.
It is useful, but not required, for the plugin to take the
--debug
option.
If no plugins succeed, this program will, as a fallback, ask for a password on the console using getpass(3), and output it. This is not meant to be the normal mode of operation, as there is a separate plugin for getting a password from the console.
Exit status of this program is zero if no errors were encountered, and otherwise not. The fallback (see the section called “FALLBACK”) may or may not have succeeded in either case.
This program does not use any environment variables itself, it
only passes on its environment to all the plugins. The
environment passed to plugins can be modified using the
--global-env
and --env-for
options. Also, the --plugin-helper-dir
option
will affect the environment variable
MANDOSPLUGINHELPERDIR
for the plugins.
/conf/conf.d/mandos/plugin-runner.conf
Since this program will be run as a keyscript, there is little to no opportunity to pass command line arguments to it. Therefore, it will also read this file and use its contents as whitespace-separated command line options. Also, everything from a “#” character to the end of a line is ignored.
This program is meant to run in the initial RAM disk environment, so that is where this file is assumed to exist. The file does not need to exist in the normal file system.
This file will be processed before the normal command line options, so the latter can override the former, if need be.
This file name is the default; the file to read for
arguments can be changed using the
--config-file
option.
/lib/mandos/plugins.d
The default plugin directory; can be changed by the
--plugin-dir
option.
/lib/mandos/plugin-helpers
The default plugin helper directory; can be changed by
the --plugin-helper-dir
option.
The --config-file
option is ignored when
specified from within a configuration file.
Please report bugs to the Mandos development mailing list:
<mandos-dev@recompile.se>
(subscription required).
Note that this list is public. The developers can be reached
privately at <mandos@recompile.se>
(OpenPGP key
fingerprint 153A 37F1 0BBA 0435 987F 2C4A 7223 2973 CA34
C2C4
for encrypted mail).
Normal invocation needs no options:
plugin-runner
Run the program, but not the plugins, in debug mode:
plugin-runner --debug
Run all plugins, but run the “foo” plugin in debug mode:
plugin-runner --options-for=foo:--debug
Run all plugins, but not the program, in debug mode:
plugin-runner --global-options=--debug
Read a different configuration file, run plugins from a different directory, specify an alternate plugin helper directory and add four options to the mandos-client(8mandos) plugin:
cd /etc/keys/mandos; plugin-runner --config-file=/etc/mandos/plugin-runner.conf --plugin-dir /usr/lib/x86_64-linux-gnu/mandos/plugins.d --plugin-helper-dir /usr/lib/x86_64-linux-gnu/mandos/plugin-helpers --options-for=mandos-client:--pubkey=pubkey.txt,--seckey=seckey.txt,--tls-pubkey=tls-pubkey.pem,--tls-privkey=tls-privkey.pem
This program will, when starting, try to switch to another user. If it is started as root, it will succeed, and will by default switch to user and group 65534, which are assumed to be non-privileged. This user and group is then what all plugins will be started as. Therefore, the only way to run a plugin as a privileged user is to have the set-user-ID or set-group-ID bit set on the plugin executable file (see execve(2)).
If this program is used as a keyscript in crypttab(5), there is a slight risk that if this program fails to work, there might be no way to boot the system except for booting from another media and editing the initial RAM disk image to not run this program. This is, however, unlikely, since the password-prompt(8mandos) plugin will read a password from the console in case of failure of the other plugins, and this plugin runner will also, in case of catastrophic failure, itself fall back to asking and outputting a password on the console (see the section called “FALLBACK”).