auditbeat: system/process module backed by quark

[haesbaert]

Proposed commit message

This introduces a new provider for the sytem/process module in linux.

The main motivation is to address some of the limitations of the current implementation. The gosysinfo provider sends state reports by scraping /proc from time to time, so it loses all short lived processes. Some customers also would like to have full telemetry but can't run auditd for various reasons.

As a bonus we get some extra ECS fields that were not available before.

MAIN DIFFERENCES:

• Publishes every process in the system, regardless of lifespan.
• Publishes exec events for an existing process (without a fork).
• Aggregates fork+exec+exit within one event.
• Adds event.exit_code for processes that exited, can't express exit_time in ECS?
• Include the original process.args, sysinfo reports args that were fetched when it parsed /proc, so a userland process can masquerade itself. For the initial /proc scraping we report the current value like sysinfo. We can't get the original value since the kernel overwrites it, if you wanna have fun: https://github.com/systemd/systemd/blob/main/src/basic/argv-util.c#L165
• Adds process.args_count.
• Adds process.interactive and if true, process.tty.char_device.{major,minor}
• Attempts to hash all processes, not just long lived ones.
• Hashing is not rate-limited anymore, but it's cached and refreshed based on metadata. It's a LRU keyed by path and refreshed if the metadata of the file changes, statx(2) if the kernel supports, stat(2) otherwise.
• No more periodic state reports, only initial batch.
• No more saving the timestamp of the last state-report in disk.
• No more /proc parsing during runtime, only on boot.

MISSING:

• Unify entity id with sessionview.
• Publish metrics from quark.Stats().
• Docs.
• Properly define config options and names.

EXTRA CHANGES:

• Added statx(2) to seccomp_linux so we can properly use CachedHasher.
• Updated quark to 0.3 so we have namespace inode numbers.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

How to test this PR locally

Run auditbeat on linux with the following configuration:

auditbeat.modules:

- module: system
  datasets:
    - process
  process.backend: "quark"

Related issues

• https://github.com/elastic/security-integrations/issues/438
• https://github.com/elastic/security-integrations/pull/417

Integrated PRs related to this

List of previous work done to minimize the size of this PR

• helper/hasher general improvements #41863
• auditbeat: split system process module #41868
• auditbeat: Add a cached file hasher for auditbeat #41952
• auditbeat: Split common tty definitions #42004

Screenshots

Non interactive SSH

Below is a shot of a non interactive ssh session, done with ssh fc39vm /bin/echo hi from quarkio.
It shows the intermediary processes of sshd until we fork the shell and echo, the interesting bits is that we can see a process that forked+execed and then execs again: sshd forks+execs mksh,, which in turn execs /bin/echo, without forking.

Comparison against the sysinfo provider for a long lived process:

Here we run a long sleep and just compare the events against the existing provider on 8.14.3:

On event.type, event.action and others

I've tried to keep things as close as possible to the old provider, but it's really just a suggestion at this point and it's likely we want to change things

event.type	gosysinfo	quark
fork	start	start
fork+exec	start	[start, change]
short fork+exec+exit	N/A	[start, change, end]
short fork+exit	N/A	[start, end]
existing processes	info	info
exec only	N/A	change
exec+exit	end	[change, end]

event.action	gosysinfo	quark
fork	process_started	process_started
fork+exec	process_started	process_started
short fork+exec+exit	N/A	process_ran
short fork+exit	N/A	process_ran
existing processes	existing_process	existing_process
exec only	N/A	process_changed_image
exec+exit	end	process_stopped

As you can see, expressing things in event.action is not great, I'm
all open to suggestions, life would be easier if it could be an
array. I've tried to compromise more states into fewer words.
process_changed_image might look a bit weird, but it's less ambiguous
than "executed". Again really open to suggestions here and I have no
strong feelings about it.

event.kind is now always event as there is no more state reports every X seconds.
The initial state report at init remains, but it's also event.

On the state of this PR

This doesn't include the documentation bits, I'd like to do this in a subsequent PR once the naming, config and whatnot is decided.
We should unify process.entity_id with sessionviewer, and we can do it in this PR, worth noting that the gosysinfo backend calculates things differently as well, so this is no worse than that.

I'm going out on holidays, but I'm taking this PR out of draft so that we can start the discussion and interested parties can test it.

[mergify]

This pull request does not have a backport label.
If this is a bug or security fix, could you label this PR @haesbaert? 🙏.
For such, you'll need to label your PR with:

• The upcoming major version of the Elastic Stack
• The upcoming minor version of the Elastic Stack (if you're not pushing a breaking change)

To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit

[mergify]

backport-8.x has been added to help with the transition to the new branch 8.x.
If you don't need it please use backport-skip label and remove the backport-8.x label.

[elasticmachine]

Pinging @elastic/sec-linux-platform (Team:Security-Linux Platform)

[andrewkroh]

We should be consistent with add_session_metadata in terms of backend option names.