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.

See Also

plainbox (1)

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