If callback_url equals file:///home/*/.aws/credentials , urlopen will read the local file (assuming the wildcard is resolved or the file exists). The content is then exfiltrated.
Alex grinned. "Hey, that's what makes life interesting, right?"
Exposing this file circumvents all perimeter defenses. Attackers gain the exact permissions assigned to that local user profile, allowing them to extract database snapshots, delete infrastructure, or spin up unauthorized resources for cryptomining. Technical Prevention and Remediations callback-url-file-3A-2F-2F-2Fhome-2F-2A-2F.aws-2Fcredentials
Ensure the library handling the "callback" (e.g., cURL, Python Requests) is explicitly configured to disallow the file:// , gopher:// , or php:// protocols. 3. Long-Term Security (Best Practices)
: The researchers identified that certain AWS-related integrations or local applications used a callback-url parameter that did not properly validate the scheme or path. If callback_url equals file:///home/*/
During an OAuth 2.0 authorization code flow, an application redirects users back to a trusted path ( redirect_uri or callback_url ). If the application fails to restrict these URLs to specific domains, an attacker can substitute the intended web domain with a file:/// handler.
: This is a classic example of SSRF where the server is coerced into making a request to its own local filesystem. "Hey, that's what makes life interesting, right
: If successful, the attacker gains the same permissions as your server's AWS IAM role, which could lead to data breaches, resource deletion, or unauthorized infrastructure costs. 🛠️ Immediate Protection Steps
To mitigate these risks, it is essential to:
If you’re building an application that handles callback URLs, follow this checklist: