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Configure SSH with the Linux Auditing System

You can configure Teleport's SSH Service to integrate with the Linux Auditing System (auditd).

Prerequisites​

  • A running Teleport cluster version 15.4.22 or above. If you want to get started with Teleport, sign up for a free trial or set up a demo environment.

  • The tctl admin tool and tsh client tool.

    On Teleport Enterprise, you must use the Enterprise version of tctl, which you can download from your Teleport account workspace. Otherwise, visit Installation for instructions on downloading tctl and tsh for Teleport Community Edition.

  • A running Teleport Node. See the Server Access Getting Started Guide for how to add a Node to your Teleport cluster. On the Node, teleport must be running as a systemd service with root permissions.
  • Linux kernel 2.6.6+ compiled with CONFIG_AUDIT. Most Linux distributions have this option enabled by default.
  • auditctl to check auditd status (optional).
  • To check that you can connect to your Teleport cluster, sign in with tsh login, then verify that you can run tctl commands using your current credentials. tctl is supported on macOS and Linux machines. For example: 
    $ tsh login --proxy=teleport.example.com --user=email@example.com
    $ tctl status
    # Cluster  teleport.example.com
    # Version  15.4.22
    # CA pin   sha256:abdc1245efgh5678abdc1245efgh5678abdc1245efgh5678abdc1245efgh5678
    If you can connect to the cluster and run the tctl status command, you can use your current credentials to run subsequent tctl commands from your workstation. If you host your own Teleport cluster, you can also run tctl commands on the computer that hosts the Teleport Auth Service for full permissions.

Step 1/4. Check system configuration​

Teleport automatically sends auditd events when it discovers that auditd is enabled in the system. You can verify that by calling auditctl -s as root.

Here is an example output from that command:

$ sudo auditctl -s
enabled 1
failure 1
pid 879
rate_limit 0
backlog_limit 8192
lost 0
backlog 0
backlog_wait_time 60000
backlog_wait_time_actual 0
loginuid_immutable 0 unlocked

The first line enabled 1 indicates that auditd is enabled, and Teleport will send events.

All events are generated on a Teleport Node. invalid user events are also generated on the Proxy Service when a Teleport user fails to authenticate.

Step 2/4. Start Teleport​

It's important to run Teleport as a system service (systemd service, for example) with root permissions. Otherwise, Teleport won't send any events to auditd due to lack of permissions.

warning

Make sure that the Teleport process has its login UID unset. Otherwise, a session ID won't be set correctly in the emitted events. You can verify that by calling cat /proc/$(pidof teleport)/loginuid. The value should be set to 4294967295.

Step 3/4. Enable the PAM integration (optional)​

Auditd can generate additional events when PAM (Pluggable Authentication Modules) is enabled. To enable the PAM integration in Teleport, add the following pam section to the configuration file on your Teleport Node (/etc/teleport.yaml by default):

ssh_service:
  # Enabled SSH Service
  enabled: true
  # Enable PAM integration
  pam:
    # "no" by default
    enabled: true
    # use /etc/pam.d/sshd configuration (the default)
    service_name: "sshd"

PAM-generated events depend on your sshd configuration when the integration is enabled. Most system generates events like USER_ACCT or USER_START. Additionally, TTY input can be logged by enabling the pam_tty_audit.so module.

For more details please refer to PAM or your operating system documentation.

When PAM integration is enabled, auditd events should closely match events generated by OpenSSH.

Step 4/4. Trace SSH sessions with auditd​

There are a few ways to trace SSH sessions in Teleport. To interact with auditd events, we will use ausearch. If your system is missing that tool, consult your distribution documentation to check how to install it.

Search by a system user​

You can search events when logging in as a system user by using the -ua switch. You can check the UID of a user by using the id command:

$ id bob
uid=1000(bob) gid=1000(bob) groups=1000(bob)

Then you can use uid to search auditd logs:

ausearch -ua 1000 -m USER_LOGIN

Search by Teleport user​

Events sent to auditd by Teleport are augmented by the teleportUser field, which contains the name of the Teleport user. ausearch doesn't let you search by custom fields, but you can use grep for that:

ausearch -m USER_LOGIN | grep teleportUser=bob

Search by session ID​

If you want to find all events generated by a specific session, first, you need to find the session ID. You can do that by using:

ausearch  -m USER_LOGIN -x teleport --just-one

Then search events only related to that one session:

ausearch --session 42