plainbox-trusted-launcher-1¶
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 (1). 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 (1) 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 (1) 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.