xenial (1) plainbox-trusted-launcher-1.1.gz
NAME
plainbox-trusted-launcher-1 - execute job command as another user
SYNOPSIS
plainbox-trusted-launcher-1 [-h] (-w | -t CHECKSUM)
[-T NAME=VALUE [NAME=VALUE ...]] [-g CHECKSUM]
[-G NAME=VALUE [NAME=VALUE ...]]
DESCRIPTION
Security elevation mechanism for plainbox
This command is a part of the implementation of plainbox. It is not intended to be invoked directly and
the command line arguments and behavior may freely change between versions.
Technically this program is used to run a command associated with a job definition as another user
(typically as root). The existing technologies such as sudo (8) and pkexec (1) don't have enough
granularity to still restrict arbitrary commands but allow the commands that are inside system-wide
installed locations (thus safe as one needs root access to install those in the first place). One
additional restriction is that some commands are themselves generated by other jobs.
Execution
Warm-up Mode
If the --warmup option is specified then nothing more happens and the program exists immediately. This is
intended to 'warm-up' the tool that executes plainbox-trusted-launcher-1 itself (typically pkexec or
sudo)
Normal Execution
In normal execution mode, the launcher looks up the job with the checksum specified by --target and
executes the command embedded inside. Environment passed via --target-environment is appended to the
environment variables inherited from the parent process.
Standard output, standard error and exit code of plainbox-trusted-launcher-1 is exactly as the values
from the commands embedded into the selected job itself.
Indirect Execution
In indirect execution mode, the launcher first looks up the job with the checksum specified by
--generator, executes it, discarding stderr and re-interpreting stdout as a set of job definitions.
Environment passed via the --generator-environment is appended (but just to the generator job, the
--target job has independent environment). All of the additional job definitions are added to the global
pool of jobs the launcher knows about.
After that the launcher continues as with normal execution, returning the same stdout, stderr and exit
code.
OPTIONS
Optional arguments:
-w, --warmup
return immediately, only useful when used with pkexec(1)
-t, --target
run a job with this checksum
-T, --target-environment
environment passed to the target job
-g, --generator
also run a job with this checksum (assuming it is a local job)
-G, --generator-environment
environment passed to the generator job
ENVIRONMENT VARIABLES
The following environment variables DO NOT affect plainbox-trusted-launcher-1
PROVIDERPATH
For plainbox this would affect the set of directories where Plainbox looks for provider
definitions. The trusted launcher has a fixed list of directories that cannot be extended.
The fixed list is composed of two system-wide locations:
• /usr/local/share/plainbox-providers-1
• /usr/share/plainbox-providers-1
All the other environment variables mentioned in plainbox work the same way.
BUGS
Currently it is impossible to use plainbox-trusted-launcher-1 with a local job needs to run as root, that
generates another local job that needs to run as root, to generate any additional jobs that also need to
run as root. In other words, only one-level job generation is supported.
The launcher is somewhat inefficient, in that it has to re-run all of the dependencies of the local job
over and over. Ideally those would be cached, per-session, but that would significantly increase the
complexity of the code running as root.
SEE ALSO
plainbox
AUTHOR
Zygmunt Krynicki & Checkbox Contributors
COPYRIGHT
2012-2014 Canonical Ltd