Burp extension to detect alias traversal via NGINX misconfiguration at scale. Requires Burp Professional.
- git clone https://github.com/bayotop/off-by-slash/
- Burp -> Extender -> Add -> find and select
off-by-slash.py
The extension implements an active scanner check. Simply run a new scan, preferably with an "Audit checks - extensions only" configuration, on static resources identified via Burp's crawler. Alternatively, use scrape.py with a list of URLs to scrape static resources from. The results can be directly passed to a new Burp scan (Burp 2.0).
A server is assumed to be vulnerable if a request to an existing path like https://example.com/static../ returns the same response as https://example.com/. To eliminate false positives the misconfiguration has to be confirmed by successfully requesting an existing resource via path traversal. This is done as follows:
For the URL https://example.com/folder1/folder2/static/main.css it generates the following links:
https://example.com/folder1../folder1/folder2/static/main.css
https://example.com/folder1../%s/folder2/static/main.css
https://example.com/folder1/folder2../folder2/static/main.css
https://example.com/folder1/folder2../%s/static/main.css
https://example.com/folder1/folder2/static../static/main.css
https://example.com/folder1/folder2/static../%s/main.css
Where %s are common directories used in alias paths based on around 9500 nginx configuration files from GH (thanks @TomNomNom), see directories.txt.