Gato-X is a FAST scanning and attack tool for GitHub Actions pipelines. You can use it to identify Pwn Requests, Actions Injection, TOCTOU Vulnerabilities, and Self-Hosted Runner takeover at scale using just a single API token. It will also analyze cross-repository workflows and reusable actions. This surfaces vulnerabilities that other scanners miss because they only scan workflows within a single repository.
Gato-X is an operator focused tool that is tuned to avoid false negatives. It will have a higher false positive rate than SAST tools like CodeQL, but Gato-X will give you everything you need to quickly determine if something is a true positive or not!
The search and enumerate modes are safe to run on all public repositories, and
you will not violate any rules by doing so.
Gato-X's attack features should only be used with authorization, and make sure to follow responsible disclosure if you find vulnerabilities with Gato-X.
Gato-X is a powerful tool and should only be used for ethical security research purposes.
Gato Extreme Edition is a tool designed to help security practitioners identify exploitable vulnerabilities in GitHub Actions workflows. It is not focused on surfacing best-practices or defense in depth measures, but instead provides users with detailed information about how someone could exploit a workflow misconfiguration.
Gato-X contains a powerful scanning engine for GitHub Actions Injection and Pwn Request vulnerabilities. As of writing, Gato-X is one of the fastest tools for the task. It is capable of scanning 35-40 thousand repositories in 1-2 hours using a single GitHub PAT. This is the most sophisticated feature in Gato-X and is the result of countless hours of development and iteration.
- Reachability Analysis
- Same and Cross-Repository Transitive Workflow AND Reusable Action Analysis
- Parsing and Simulation of "If Statements"
- Gate Check Detection (permission checks, etc.)
- Lightweight Source-Sink Analysis for Variables
- Priority Guidelines
As an operator facing tool, Gato-X is tuned with a higher false positive rate than a tool designed to generate alerts, but it provides contextual information to quickly determine if something is worth investigating or not. To aid in triage, Gato-X attempts to apply confidence ratings to its reports.
Gato-X automates the "Runner-on-Runner" (RoR) technique, which essentially means installing another GitHub Actions runner as an implant on an existing runner.
Gato-X supports deploying RoR through fork pull requests. Gato-X also supports
creating a RoR payload only, which can be used in conjunction with the push workflow
functionality to jump to internal self-hosted runners.
Under the hood, Gato-X will perform the following steps:
- Prepare RoR C2 Repository
- Prepare payload Gist files
- Deploy the RoR implantation payload.
- Confirm successful callback and runner installation.
- Provide user with an interactive webshell upon successful connection.
From the user's perspective, it's simply: run command, get shell. What more could a hacker want?
If you ever encounter a GitHub PAT, you can use Gato-X to validate it and identify what it has access to. Gato-X will identify repositories with administrative access and the names of accessible secrets (if the user has write access).
Gato-X currently only automates the self-hosted runner attack. It does not contain any features to automate the exploitation process for Pwn Requests and Injection. I plan to add a feature that will perform automated exploitation of simple Pwn Requests and Injection vulnerabilities using flexible attack templates (defined in yaml)
First, create a GitHub PAT with the repo scope. Set that PAT to the
GH_TOKEN environment variable.
Next, use the search feature to retrieve a list of candidate repositories:
gato-x s -sg -q 'count:75000 /(issue_comment|pull_request_target|issues:)/ file:.github/workflows/ lang:yaml' -oT checks.txt
Finally, run Gato-X on the list of repositories:
gato-x e -R checks.txt | tee gatox_output.txt
This will take some time depending on your computer and internet connection speed. Since the results are very long, use tee to save them to a file
for later review. Gato-X also supports JSON output, but that is intended for further machine analysis.
To perform a public repository self-hosted runner takeover attack, Gato-X requires a PAT with the following scopes:
repo, workflow, and gist.
This should be a PAT for an account that is a contributor to the target repository (i.e. submitted a typo fix).
gato-x a --runner-on-runner --target ORG/REPO --target-os [linux,osx,windows] --target-arch [arm,arm64,x64]
It is very rare that maintainers select allowing workflows on pull request from all external users without approval, but it has happened.
Next, Gato-X will automatically prepare a C2 repository and begin the operation. Gato-X will monitor each step as the attack continues, exiting as gracefully as possible at each phase in case of a failure. If workflow approval is required, Gato-X will wait a short period of time before exiting.
If the full chain succeeds, Gato-X will drop to an interactive prompt. This will execute shell commands on the self-hosted runner.
If the target runner is non-ephemeral, use the --keep-alive flag. This will keep the workflow running. GitHub
Actions allows workflow runs on self-hosted runners to run for up to 5 days (as of writing, this might change - it was 30 days).
These automated attacks only scratch the surface of the kinds of post-compromise attacks paths that a red teamer may encounter within large GitHub Enterprise tenants. See the wiki for complex cases and how Gato-X may help.
- Deploying RoR using custom workflow via the push trigger.
- Deploying RoR using a PAT that only has the
reposcope but can obtain execution viaworkflow_dispatch/pushtriggers. - Leveraging a
reposcoped token to bypass external contributor approval requirements, but leveraging Gato-X for RoR infrastructure setup. - Using a
GITHUB_TOKENwithactions: writefrom a Pwn Request to approve a fork PR from an external contributor.
Gato supports OS X and Linux with at least Python 3.10.
Gato-X is published on PyPi, so you can simply install it with pip install gato-x
In order to install the tool from source, simply clone the repository and use pip install.
We recommend performing this within a virtual environment.
git clone https://github.com/AdnaneKhan/gato-x
cd gato-x
python3 -m venv venv
source venv/bin/activate
pip install .
OR You can use pipx
git clone https://github.com/AdnaneKhan/gato-x
cd gato-x
pipx install .
If you need to make on-the-fly modifications, then install it in editable mode with pip install -e.
After installing the tool, it can be launched by running gato-x.
We recommend viewing the parameters for the base tool using gato -h, and the
parameters for each of the tool's modules by running the following:
gato-x search -hgato-x enum -hgato-x attack -h
The tool requires a GitHub classic PAT in order to function. To create one, log
in to GitHub, go to GitHub Developer Settings
and select Generate New Token and then Generate new token (classic).
After creating this token set the GH_TOKEN environment variable within your
shell by running export GH_TOKEN=<YOUR_CREATED_TOKEN>. Alternatively, enter it when the application
prompts you.
For troubleshooting and additional details, such as installing in developer mode or running unit tests, please see the wiki.
As an operator facing tool with rapidly developed features, Gato-X will have bugs. Typically, these are related to edge cases with run log formatting or YAML files.
If you believe you have identified a bug within the software, please open an issue containing the tool's output, along with the actions you were trying to conduct.
Contributions are welcome! Please review the design methodology before working on a new feature!
Additionally, if you are proposing significant changes to the tool, please open an issue open an issue to start a conversation about the motivation for the changes.
Gato-X is licensed under the Apache License, Version 2.0.
Gato-X:
Copyright 2024, Adnan Khan
Original Gato Implementation:
Copyright 2023 Praetorian Security, Inc
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.