Since the server also accepts logical and arithmetic functions, you can manipulate its operations too, as illustrated below. You can exploit this flaw to bypass restrictions, read unauthorized data from the resources, and a lot more. System administrators can prevent the exploitation of these types of vulnerabilities by splitting access to the system between different user roles. Additionally, limiting their abilities and rights to only specific or required operations at the system level prevents the execution of tasks with system-wide impact.
The more notorious and pervasive injection vulnerabilities are, the more attractive they are for attackers looking to exploit them. Note: Daniel Bechenea , penetration tester at Pentest-Tools. Save my name, email, and website in this browser for the next time I comment. Home Platform tutorials How to detect injection flaws with Pentest-Tools. Platform tutorials. Last updated on March 19, Reading time 9 minutes.
What are injection vulnerabilities? The root cause for injection attacks The underlying cause of injection attacks is the lack of data validation and data sanitization while taking and processing user input generated data at both application level and server-side. Why is code injection so pervasive? Log into your Pentest-Tools. How to create re-usable templates for future engagements that include SQL Injection vulnerabilities 1. Under the Reporting menu, select Finding templates. OS Operating System Injection You can detect this issue when the application makes an insecure call as an operating system command based on a user-provided input to execute it on the system level.
First and foremost, make sure to include data validation mechanisms within your application. Try to move your assets using a safe API. It will avoid the use of the interpreter entirely and would provide you with an interface whose parameters are already defined by the server, thus blocking attackers from making any changes to the data or sliding a malicious piece of code. Since URLs are limited in size, they cannot be used directly to inject a lot of content.
But there is enough space to inject a frame into the page and to point the frame to a server controlled by an attacker. A large injected frame can cover the content that would normally appear on the page or push it outside the visible browser area.
When a successful deception attack takes place, the user will see a trusted location in the location bar and read the content supplied by the attacker a handy way of publishing false news on the Internet. This may lead to a successful phishing attack. If an XSS attack is performed against a web site where users keep confidential information, a piece of JavaScript code can gain access to the displayed pages and forms and can collect the data and send it to a remote evil server.
Sometimes a user's browser can go places the attacker's browser cannot. This is often the case when the user is accessing a password-protected web site or accessing a web site where access is restricted based on an IP address. Execution of malicious requests on behalf of the user. This is an extension from the previous point. Not only can the attacker access privileged information, but he can also perform requests without the user knowing. This can prove to be difficult in the case of an internal and well-guarded application, but a determined attacker can pull it off.
It's a dangerous type of attack because, unlike XSS where the attacker must interact with the original application directly, CSRF attacks are carried out from the user's IP address and the attacker becomes untraceable. Successful activation of an ActiveX object, for example, would allow the attacker to take full control over the workstation.
If the browser is not maintained and regularly patched, it may be possible for malicious code to compromise it. An unpatched browser is a flaw of its own, the XSS attack only helps to achieve the compromise. The most dangerous consequence of an XSS attack is having a session token stolen. Session management mechanics were discussed earlier in this chapter. A person with a stolen session token has as much power as the user the token belongs to. Imagine an e-commerce system that works with two classes of users: buyers and administrators.
Anyone can be a buyer the more the better but only company employees can work as administrators. A cunning criminal may register with the site as a buyer and smuggle a fragment of JavaScript code in the registration details in the name field, for example.
Sooner or later the attacker may place a small order to speed things up, especially if it is a smaller shop one of the administrators will access her registration details, and the session token will be transmitted to the attacker.
Notified about the token, the attacker will effortlessly log into the application as the administrator. If written well, the malicious code will be difficult to detect. It will probably be reused many times as the attacker explores the administration module.
In our first XSS example, we displayed the contents of the document. The value of the cookie is stored in document. To steal a cookie, you must be able to send the value somewhere else. An attacker can do that with the following code:. If embedding of the JavaScript code proves to be too difficult because single quotes and double quotes are escaped, the attacker can always invoke the script remotely:. Though these examples show how a session token is stolen when it is stored in a cookie, nothing in cookies makes them inherently insecure.
All session token transport mechanisms are equally vulnerable to session hijacking via XSS. XSS attacks can be difficult to detect because most action takes place at the browser, and there are no traces at the server. Usually, only the initial attack can be found in server logs. One way of mitigating XSS attacks is to turn off browser scripting capabilities.
However, this may prove to be difficult for typical web applications because most rely heavily on client-side JavaScript. Internet Explorer supports a proprietary extension to the Cookie standard, called HttpOnly , which allows developers to mark cookies used for session management only.
Such cookies cannot be accessed from JavaScript later. This enhancement, though not a complete solution, is an example of a small change that can result in large benefits. Unfortunately, only Internet Explorer supports this feature. XSS attacks can be prevented by designing applications to properly validate input data and escape all output. Users should never be allowed to submit HTML markup to the application. But if you have to allow it, do not rely on simple text replacement operations and regular expressions to sanitize input.
Instead, use a proper HTML parser to deconstruct input data, and then extract from it only the parts you know are safe. Command execution attacks take place when the attacker succeeds in manipulating script parameters to execute arbitrary system commands.
These problems occur when scripts execute external commands using input parameters to construct the command lines but fail to sanitize the input data. Command executions are frequently found in Perl and PHP programs. These programming environments encourage programmers to reuse operating system binaries.
For example, executing an operating system command in Perl and PHP is as easy as surrounding the command with backtick operators. Look at this sample PHP code:.
This code is meant to display a list of files in a folder. If a semicolon is used in the input, it will mark the end of the first command, and the beginning of the second. The second command can be anything you want. The invocation:. Once the attacker compromises the server this way, he will have many opportunities to take advantage of it:.
Start a Telnet server and log into the server with privileges of the web server user. The most commonly used attack vector for command execution is mail sending in form-to-email scripts. These scripts are typically written in Perl.
They are written to accept data from a POST request, construct the email message, and use sendmail to send it. A vulnerable code segment in Perl could look like this:. Since the value of the parameter is used directly on the command line an attacker could terminate the email address using a semicolon, and execute any other command on the system.
Code execution is a variation of command execution. It refers to execution of the code script that runs in the web server rather than direct execution of operating system commands. There are various kinds of injection flaws out there that serve different purposes. Injection flaws are a group of attack vectors aimed at causing malfunction or compromise the primary purpose of any given web application or website.
These attacks are implemented using user input to a system. Largely, this causes disrepute between the organization and its customers, resulting in great financial loss.
It is also known as SQLi. Attackers use this database language in input controls to gain unauthorized access to web applications, thus compromising their integrity and confidentiality.
SQL Injection can be prevented by strongly validating input fields such that user input is filtered before it is submitted or by the use of online software tools that scan your web application for injection vulnerabilities. Other prevention techniques include using password encryption and managing the error messages revealed to users so that they only show that there has been an error, but the internal details are not revealed.
Example of validation: Command Injection Command Injection is when the attacker injects operating system commands on a user input field. The attacker may inject malicious commands to the host's operating system and get sensitive information from the webserver. These languages encourage programmers to reuse operating system binaries. Command Injection requires the attacker to manipulate script parameters that execute arbitrary system commands.
These problems occur when scripts execute external commands using input parameters to construct command lines, but fail to filter the input data. This means that the attacker will have compromised the host operating system and he may proceed to start a Telnet server and log into the server as a user, try to gain root access, try to download and compile the source code of the application, and execute any binary on the server.
Another common Command injection attack is through the email sending in form-to-email scripts. These scripts are usually written in Perl. Using validation on all untrusted user inputs. Usually, this is used to gain trust from an unsuspecting user.
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