Uncovering Template Injection: Protect Yourself
By Tom Seest
At BestCybersecurityNews, we help entrepreneurs, solopreneurs, young learners, and seniors learn more about cybersecurity.
In this article, we’ll cover server-side template injection (SSTI) vulnerabilities and how to prevent them. We’ll also discuss how to identify SSTI attacks with invalid syntax, how to protect against remote code execution flaws, and the best open-source vulnerability scanners.
Table Of Contents
- Can Logic-less Templates Protect Your Website from Template Injection?
- How Can You Detect and Prevent SSTI Exploits?
- Are Your Templates at Risk? Exploring Remote Code Execution Flaws
- Are You Using the Best Tools for Template Injection Vulnerabilities?
- Ready to Hack: Unleashing the Power of Template Injection?
The best way to prevent server-side template injection vulnerabilities and attacks is to use logic-less templates. By using logic-less templates, developers can isolate the presentation logic from the data that is presented. Logic-less templates can also prevent template changes from occurring on the server.
This prevents the use of user-controlled input to create template engines. Instead, input should be passed to templates through template parameters. To minimize vulnerabilities to malicious probing, users should sanitize the input before passing it to templates. For example, they should avoid using risky characters in template attributes. Additionally, developers can sandbox the template environment in a docker container, which can limit malicious activities.
In addition to logic-less templates, developers should use templates that separate the visual rendering of code from the underlying code. One popular logic-less template is Mustache, which isolates the application logic from the visual rendering. This technique greatly reduces the risk of RCE attacks. Logic-less templates can also reduce the impact of SSTI attacks. However, they are complex to implement and require testing to ensure that they are effective.
While logic-less templates don’t prevent all server-side template injection attacks, a template engine may be used to present dynamic data. For example, the server-side evaluation of a mathematical operation can result in a string that looks like Hello 49 but actually says “Hello Carlos.” These attacks are common and can cause a web server to display an error message or flag an exception.
Server-side template injection attacks can be devastating. In most cases, an attacker will inject malicious code into a template engine in order to control the server. These attacks can lead to the release of sensitive information, the upload of malicious files, and remote code execution. This is a potentially disastrous security flaw for any organization.
Submitting invalid syntax is a simple yet effective technique for identifying SSTI compromises in web applications. This technique exploits common template expressions to construct a payload that can fetch a blank response or an error response. To do so, the tester inserts an HTTP GET parameter into a variable within a template statement. Then, after using the payload, he injects an HTML tag to make the response invalid.
SSTI is a vulnerability in applications that do not sanitize user inputs. It can lead to remote code execution and read/write access to sensitive data and arbitrary files on the server. This attack can also be triggered by the presence of user input embedded directly in a template.
The SSTI vulnerability affects web applications that allow users to manage email templates. In these web applications, a basic template for an email is defined, and the user can edit some fields. The template engine then generates a final email based on these changes. The template engine evaluates user expressions in the template, which could lead to a server compromise.
While sanitization is a great way to minimize the risk of SSTI attacks, it is not foolproof. It is still important to implement the best practices and perform testing to ensure their effectiveness. For example, it is recommended to run a regex to identify invalid syntax before submitting it. This is a simple but effective way to reduce the likelihood of an SSTI attack.
Tplmap is a Python tool for detecting Server Side Template Injection (SSTI) vulnerabilities and exploits. It uses sandbox escape techniques to exploit vulnerable template engines and can also run code remotely. The exploitation of these vulnerabilities can lead to unauthorized access to the target file system and operating system.
To secure your website from this type of attack, template engines must not be created using user-controlled input. Instead, these elements should be passed to templates using template parameters. This reduces the vulnerabilities of malicious probing. For example, if the template includes a script element, an attacker may attempt to inject arbitrary code into the code.
Using a fuzzing approach, a tester can test whether a template engine is vulnerable to SSTI by using a polyglot payload at a user input parameter. The server’s response may show an error message or flag an exception. If the payload is malformed, the test can identify the underlying template engine.
A server-side template injection vulnerability can be caused by an improper template design or by a web application that allows privileged users to edit templates. This poses a huge security risk, and some websites deliberately allow privileged users to edit templates. These privileged users have access to sensitive information and are prime candidates for server-side template injection attacks. In some cases, successful attacks may involve arbitrary remote code execution.
To test a web application for template injection vulnerabilities, you can use tools like Skipfish. It is free and makes an interactive sitemap of the target web application. The tool also runs dictionary-based and repetitive crawls and annotates the sitemap with the results of several active scans. Another free vulnerability scanner is Wapiti, which crawls web pages of the target web application and looks for forms that allow data injection. It functions much like a fuzzer.
While free vulnerability scanners are not without their flaws, they do have their own benefits. For example, you can use one of them to identify and remediate template injection attacks. You can also use them to set up scheduled scans and create compliance policies. They can also show you how many vulnerabilities your site has been exposed to over time.
One free vulnerability scanner for template injection attacks is Skipfish. This tool automatically detects template injection vulnerabilities by crawling through the web pages of a target web application. It uses dictionary-based attacks and repetitive crawls to find vulnerabilities. This vulnerability scanner also provides an interactive sitemap of the target web application, annotated with the output of several active scans. Another free vulnerability scanner is Wapiti, which crawls the web pages of the target web application to look for forms that can be exploited to inject data. Similar to a fuzzer, this tool is able to detect many common template injection attacks.
Free and open-source vulnerability scanners for these attacks are available for download. These tools are part of software composition analysis (SCA) tools, which detect and analyze open-source components within software projects. They then compare these components to vulnerability databases and alert you to vulnerabilities, suggesting a course of action to fix them.
These scanners are designed to find code injection and server side template injection vulnerabilities. They can exploit sandbox escape techniques and use SSTI (Server Side Template Injection) to gain access to the target file system or operating system. These vulnerabilities are common, especially in unsandboxed environments.
Injection attacks are a type of web application vulnerability in which an attacker injects malicious content into a website. They can take advantage of the lack of protection provided by the server side of the application by inserting malicious code into the template. Such an attack is a powerful exploitation vector in an organization, resulting in the disclosure of sensitive information, upload of malicious files, or even remote code execution.
The first step to exploitation is to identify the vulnerabilities. This is often done by fuzzing a template. This technique involves injecting special characters into a template to see whether it raises an exception. If a server-side template injection vulnerability exists, the test script can be modified to exploit it.
Using nested properties in templates is also a powerful attack technique. By hiding a variable in a place holder, an attacker can inject arbitrary data into the template, thereby modifying the content. This is similar to how SQL injection attacks are executed by inserting malicious code into a prepared statement. In addition, some websites deliberately allow privileged users to edit templates, which poses a massive security risk.
A successful template injection attack will inject a malicious URL into the target website. This technique will allow an attacker to inject malicious code into the template, either locally or remotely. The malicious template will then execute arbitrary code on the web server. Once successfully injected, the attacker will be able to take control of the web server. To craft a successful template injection attack, first determine the type of template engine that the target site is using. Review its documentation to understand the basic syntax and security considerations. Next, map out the attack surface and audit every exposed object.
An injection attack is similar to an XSS attack in that it alters the displayed page of a website. It can steal user information and alter the website’s appearance. Moreover, a successful injection attack can also change the identity of another user. For example, a malicious user can inject an entire page or create a fake login page in order to steal login data from the final user.
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