#Python flask cheat sheet code
If you happen to have the source code of the application, look for the flask.render_template_string(source, **context) function. From there you can crawl up to the root object class using _mro_, then crawl back down to every new-style object in the Python environment using _subclasses_. The usual exploitation starts with the following: from a simple empty string "" you will create a new-type object, type str. Read the docs for more.īasically, you can crawl up the inheritance tree of the known objects using mro, thus accessing every class loaded in the current python environment (!). In python _mro_ or mro() allows us to go back up the tree of inherited objects in the current Python environment, and _subclasses_ lets us come back down.
This guide will specifically focus on Jinja2. Tplmap or its Burp Suite Plugin will do the trick. Note that there are other methods to identify more template engines. This step is sometimes as trivial as submitting invalid syntax, as template engines may identify themselves in the resulting error messages. It would result in 49 in Twig, 7777777 in Jinja2, and neither if no template language is in use. You can try to probe to see if the target is vulnerable. Assuming this, I’m not going to explore in detail how does Flask/Jinja work, neither python internals. RTFMĪs everything in this field, explore the docs of Jinja, Flask & Python and learn them by heart. This cheatsheet will introduce the basics of SSTI, along with some evasion techniques we gathered along the way from talks, blog posts, hackerone reports and direct experience. While SSTI in Flask are nothing new, we recently stumbled upon several articles covering the subject in more or less detail because of a challenge in the recent TokyoWesterns CTF.
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