Hi Steve,
`auditctl -D` does not make it go away (outputs `No rules`). auditd isn't
running at all and this behavior is happening purely from the kernel. These
systems were never set to enabled 2 (locked).
I went ahead and filed a Github issue for this thread:
https://github.com/linux-audit/audit-kernel/issues/146
The maintainer there suggested it's too difficult to debug due to eBPF
programs + AWS's modified kernel. I've resigned to asking Red Canary to
support eBPF mode with `audit=0` kernel parameter in their Linux EDR. Let
me know if you have any other ideas.
Regards,
Samuel Bahr
Pinterest Sr. Site Reliability Engineer
On Sun, Jul 23, 2023 at 7:17 PM Steve Grubb wrote:
> On Thursday, June 29, 2023 6:34:03 PM EDT Samuel Bahr wrote:
> > Hi linux-audit,
> >
> > I'm running a fleet of Linux hosts with Red Canary Linux EDR (Endpoint
> > Detection and Response) which uses eBPF for gathering telemetry in
> service
> > ` cfsvcd.service`. In an older configuration, it gathered data from the
> > kernel's audit system and everything was fine. However, when we switched
> > cfsvcd to gathering data from eBPF instead, we noticed that the kernel
> > ring buffer was flooded with audit messages. This is because
> > cfsvcd.service now stops auditd.service, but leaves the kernel audit
> > system enabled.
> >
> > I've mitigated this issue by manually running `# auditctl -e 0` on our
> > hosts (via Puppet). However, I'm running into a strange issue where
> _some_
> > hosts (~0.5%) are still logging all audit events to the kernel ring
> buffer
> > even after I have disabled the audit system via `# auditctl -e 0`. A `#
> > auditctl -s` run shows `enabled 0`, yet audit logs continue to flood the
> > kernel ring buffer.
> >
> > I'm running Linux kernel 5.4.0-1063-aws on Ubuntu 18.04 with auditctl
> > v2.8.2. `systemd-journald-audit.socket` is masked & inactive, `
> > auditd.service` is disabled & inactive.
> >
> > I cannot entirely disable the audit system via a kernel parameter because
> > Red Canary Linux EDR fails to start cfsvcd.service as it fails to run
> some
> > auditctl command due to no audit support in the kernel:
> >
> > Jun 28 20:41:04 systemd[1]: Started Canary Forwarder Service.
> >
> > > Jun 28 20:41:04 cfsvcd[105781]: Found config file at path
> > > '"/opt/redcanary/config.json"', continuing execution...
> > > Jun 28 20:41:12 cfsvcd[105781]: component: Sentry
> > > Jun 28 20:41:12 cfsvcd[105781]: Jun 28 20:41:12.055 INFO Initializing
> > > Sentry Config { version: "1.4.17.release.[...]", https_proxy: None,
> > > extra_tags: [("telemetry.source", "eBPF")], logging_enabled: true,
> > > metrics_enabled: true, [...]}
> > > Jun 28 20:41:12 cfsvcd[105781]: Failed to setup or configure host
> system:
> > > Linux Audit watcher failure: Netlink Error: IO Error: Protocol not
> > > supported (os error 93)
> > > Jun 28 20:41:12 cfsvcd[105781]: Received stop. Exiting
> > > unix::wait_for_signal. Signal: 0, done.is_signaled(): true
> > > Jun 28 20:41:12 cfsvcd[105781]: Joining async_agent_thread
> > > Jun 28 20:41:13 cfsvcd[105781]: Attempting to stop subscriber (Ebpf).
> > > Jun 28 20:41:13 cfsvcd[105781]: Shutting down due to termination signal
> > > [...]
> > > Jun 28 20:41:15 cfsvcd[105781]: Subscriber stopped.
> > > Jun 28 20:41:15 auditctl[106733]: Error - audit support not in kernel
> > > Jun 28 20:41:15 auditctl[106733]: Cannot open netlink audit socket
> > > Jun 28 20:41:15 systemd[1]: cfsvcd.service: Service hold-off time over,
> > > scheduling restart.
> > > Jun 28 20:41:15 systemd[1]: cfsvcd.service: Scheduled restart job,
> > > restart
> > > counter is at 301.
> > > Jun 28 20:41:15 systemd[1]: Stopped Canary Forwarder Service.
> >
> > Here's the unit file for cfsvcd.service:
> > > [Unit]
> > > Description=Canary Forwarder Service
> > >
> > > DefaultDependencies=no
> > > After=local-fs.target systemd-tmpfiles-setup.service auditd.service
> > > Before=sysinit.target shutdown.target
> > > # Replace the auditd service if it is running
> > > Conflicts=auditd.service shutdown.target
> > >
> > > [Service]
> > > WorkingDirectory=/opt/redcanary
> > > ExecStart=/opt/redcanary/cfsvcd
> > > ExecStopPost=-/sbin/auditctl -D
> > > Restart=always
> > > TimeoutSec=15
> > >
> > > [Install]
> > > WantedBy=multi-user.target
> >
> > Is this a known issue?
>
> Not really. But this is a new capability. If you run auditctl -D, does it
> go
> away? Have any of the systems been setup with auditctl -e 2? This makes
> the
> configuration immutable.
>
> -Steve
>
> > Is there a workaround to stop the logging to the
> > kernel ring buffer? Is there any more information I can provide to help
> > debug?
>
>
>
>
--
Linux-audit mailing list
Linux-audit@redhat.com
https://listman.redhat.com/mailman/listinfo/linux-audit
