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Introduction

The Falco Plugin for GitLab ingests Audit Events from GitLab and makes them available as fields in Falco. With the GitLab Audit Event fields available in Falco, you can create Falco rules to detect GitLab threats in real-time, and alert on them through your configured notification channel. You can find more about GitLab Audit Events here

What's the value in ingesting GitLab events into Falco?

Well - because Falco can perform threat detection across a number of cloud platforms in parallel, it allows you to correlate security events across multiple sources in real-time, to detect active lateral movement as it is occurring.

Prerequisites

1. The plugin needs to compile with a minimum of Go version 1.20
2. Accessing Audit Events requires a GitLab Ultimate or Premium subscription.
3. Whilst the plugin will work with SaaS or Self-managed offerings, instance-level audit events are only available in the Self-managed offering - the plugin will detect more with in the Self-managed offering
4. (Optional) Access to a Maxmind GeoLite or GeoIP2 database to enrich IP addresses with Geolocation information

Configuring Audit Event Streaming

The plugin provides a webhook server that can be configured as an Audit Event Streaming Destination in GitLab. GitLab will then forward Audit Events to Falco, which will receive them, parse them, and then alert based on rules defined in the rules/gitlab.yaml.

GitLab Audit Event Streaming Destinations can be configured at the Group or Instance Level. Configuring event streaming at the Instance Level will send all the instances audit events to Falco, whereas configuring event streaming at the Group level will only send group level audit events - more detections will apply if you send Instance level events to Falco.

When you configure a instance/group level event streaming, you will be provided with a verification token. This verification token needs to be configured in falco.yaml to allow Falco to authentication and validate the events.

Configuring Instance Level Audit Events

You can find details for configuring an instance streaming destination here - the basic steps are:

1. Access Admin Area
2. Click Monitoring -> Audit Events
3. Click on the Streams tab
4. Select Add streaming destination and click HTTP endpoint
5. Enter Name and Destination URL
6. Click Add button to create the streaming destination
7. Once the streaming destination is created, copy the verification token - we will use it in falco.yaml file

Configuring Group Level Audit Events

You can find details for configuring a group-level streaming destination here - the basic steps are:

1. On the left sidebar, select Search or go to and find your group.
2. Select Secure > Audit events.
3. On the main area, select the Streams tab.
4. Select Add streaming destination and click HTTP endpoint
5. Enter Name and Destination URL
6. Click Add button to create the streaming destination
7. Once the streaming destination is created, copy the verification token - we will use it in falco.yaml file

Download Maxmind City Database for IP Geolocation enrichment

The plugin has the ability to enrich IP addresses with geolocation information using the Maxmind GeoLite (free) or GeoIP2 (commercial) databases. You can register for Maxmind databases here. Once you have downloaded the Maxmind City Database in mmdb format, store it somewhere on the file system where Falco can access it.

You can then configure the plugin to use the database by configuring the maxmindcitydbpath option in falco.yaml. See Configuring the plugin section below.

Building the GitLab plugin

1. Download the plugin from GitHub using git
2. Change directory to falco-plugin-gitlab
3. Compile the plugin using make
4. Copy libgitlab.so to /usr/share/falco/plugins
5. Copy the rules to /etc/falco/rules.d/

git clone https://github.com/an1245/falco-plugin-gitlab
cd falco-plugin-gitlab
make
cp libgitlab.so /usr/share/falco/plugins/
cp rules/* /etc/falco/rules.d/

Configuring the plugin

Now that you have configured your streaming destination and collected your verification token, you can provide them as values in the falco.yaml file.

In the configuration file you will find the following settings:

• UseHTTPS and SecretsDir - to configure the plugin to use HTTPS for the webhook server (you should do this!)
• VerificationToken - here you put your verification token that was supplied in the destination configuration
• MaxmindCityDBPath - path to your Maxmind City DB (oiptional)
• Debug and DebugJSON - to enable plugin debugging or rule creation

- name: gitlab
    library_path: libgitlab.so
    init_config:
      SecretsDir: /path/to/ssl-cert-and-key-files
      UseHTTPS: true
      VerificationToken: {YOUR VERIFICATION TOKEN}
      MaxmindCityDBPath: /path/to/GeoLite2-City.mmdb
      Debug: false
      DebugJSON: false

Now that you've got the plugin configuration done, you can enable it by adding the plugin name to the load_plugins configuration setting.

load_plugins: [gitlab]

Now start Falco.

• If you have set the plugin UseHTTPS configuration option to true, the plugin will start a SSL enabled web server on port TCP/443.
• If you have set the plugin UseHTTPS configuration option to false, the plugin will start a SSL enabled web server on port TCP/80.

Firewalling the plugin

To ensure that only that only the GitLab server(s) can talk to the plugin, make sure that you firewall the source IPs that can access the webhook server. If you are connecting to the GitLab SaaS service, you can find information about the ip ranges that GitLab use for that service here

Debugging the Plugin

We recommend leaving Debug set to False unless you are trying to troubleshoot the plugin.

But if you need to troubleshoot the plugin, you set Debug: True and then run falco manually from the command line - this will output debug messages to STDOUT. You can also set the DebugJSON value to True to print the raw JSON message coming from GitLab.

Default Rules

You can find a number of sample Falco rules in the rules/gitlab.yaml file which will detect a number of malicious events including:

• Accessing Admin Mode from an IP address in an unknown country
• Failed user logins - both failed passwords and OTP token failures
• Disabling or 2-Factor Authentication at a user or group level
• Creation of new SSH certificates, GPG Keys or Personal/Project/Group Access tokens
• Creation of new Deploy or Cluster Agent tokens

Here are four tips for creating your own rules.

1. GitLab provides the event_type field in the streaming events which we can use as conditions in Falco rules. You can find documentation on the event_types here
2. You can view some sample JSON messages in the tests/jsonmessages/ directory
3. GitLab doesn't currently provide documentation for each events JSON response document; however, there is a rule in rules/gitlab.yaml called GitLab Catch All - it's commented out by default to reduce noise, but you can enable this rule to alert on every GitLab Event not captured by another rule and output all the mapped fields.
4. You can also set the DebugJSON to true and can see how the GitLab fields are mapped to Falco fields by observing the Falco Event JSON: log message.

Exported Fields

A number of fields are mapped across from GitLab event fields into Falco fields - these can be seen in the table below.

Note

I have also created a version of the plugin that supports polling the GitLab API to fetch Audit Events - however, currently GitLab doesn't ship the event_type field in the API delivered events so the rules don't work. So this polling approach is still a work-in-progress, but this version of the plugin is available in polling-and-webhook branch.

Feedback

Please provide me with feedback if you think there are better ways I could do things - you can do that by starting a discussion or logging an issue!

Thanks

Thanks to the folks who helped out with this plugin.