Broken Access Control
Most computer systems are designed for use with multiple users. Privileges mean what a user is permitted to do. Common privileges include viewing and editing files, or modifying system files.
Privilege escalation means a user receives privileges they are not entitled to. These privileges can be used to delete files, view private information, or install unwanted programs such as viruses. It usually occurs when a system has a bug that allows security to be bypassed or, alternatively, has flawed design assumptions about how it will be used. Privilege escalation occurs in two forms:
- Vertical privilege escalation, also known as privilege elevation, where a lower privilege user or application accesses functions or content reserved for higher privilege users or applications (e.g. Internet Banking users can access site administrative functions or the password for a smartphone can be bypassed.)
- Horizontal privilege escalation, where a normal user accesses functions or content reserved for other normal users (e.g. Internet Banking User A accesses the Internet bank account of User B)1
Challenges covered in this chapter
|Access the administration section of the store.|
|Access someone else's basket.|
|Get rid of all 5-star customer feedback.|
|Put an additional product into another user's shopping basket.|
|Post some feedback in another users name.|
|Post a product review as another user or edit any user's existing review.|
|Change the href of the link within the O-Saft product description into http://kimminich.de.|
|Request a hidden resource on server through server.|
Access the administration section of the store
Just like the score board, the admin section was not part of your "happy path" tour because there seems to be no link to that section either. In case you were already logged in with the administrator account you might have noticed that not even for him there is a corresponding option available in the main menu.
- Knowing it exists, you can simply guess what URL the admin section might have.
- Alternatively, you can try to find a reference or clue within the parts of the application that are not usually visible in the browser
- It is probably just slightly harder to find and gain access to than the score board link
- There is some access control in place, but there are at least three ways to bypass it.
View another user's shopping basket
This horizontal privilege escalation challenge demands you to access the shopping basket of another user. Being able to do so would give an attacker the opportunity to spy on the victims shopping behaviour. He could also play a prank on the victim by manipulating the items or their quantity, hoping this will go unnoticed during checkout. This could lead to some arguments between the victim and the vendor.
- Try out all existing functionality involving the shopping basket while having an eye on the HTTP traffic.
- There might be a client-side association of user to basket that you can try to manipulate.
- In case you manage to update the database via SQL Injection so that a user is linked to another shopping basket, the application will not notice this challenge as solved.
Get rid of all 5-star customer feedback
If you successfully solved above admin section challenge deleting the 5-star feedback is very easy.
Put an additional product into another user's shopping basket
View another user's shopping basket was only about spying out other customers. For this challenge you need to get your hands dirty by putting a product into someone else's basket that cannot be already in there!
- Check the HTTP traffic while placing products into your own shopping basket to find a leverage point.
- Adding more instances of the same product to someone elses basket does not qualify as a solution. The same goes for stealing from someone elses basket.
- This challenge requires a bit more sophisticated tampering than others of the same ilk.
Post some feedback in another users name
The Juice Shop allows users to provide general feedback including a star rating and some free text comment. When logged in, the feedback will be associated with the current user. When not logged in, the feedback will be posted anonymously. This challenge is about vilifying another user by posting a (most likely negative) feedback in his or her name!
- This challenge can be solved via the user interface or by intercepting the communication with the RESTful backend.
- To find the client-side leverage point, closely analyze the HTML form used for feedback submission.
- The backend-side leverage point is similar to some of the XSS challenges found in OWASP Juice Shop.
Post a product review as another user or edit any user's existing review
Change the href of the link within the O-Saft product description
The OWASP SSL Advanced Forensic Tool (O-Saft) product has a link in its description that leads to that projects wiki page. In this challenge you are supposed to change that link so that it will send you to http://kimminich.de instead. It is important to exactly follow the challenge instruction to make it light up green on the score board:
- Original link tag in the description:
<a href="https://www.owasp.org/index.php/O-Saft" target="_blank">More...</a>
- Expected link tag in the description:
<a href="http://kimminich.de" target="_blank">More...</a>
- Theoretically there are three possible ways to beat this challenge:
- Finding an administrative functionality in the web application that lets you change product data
- Looking for possible holes in the RESTful API that would allow you to update a product
- Attempting an SQL Injection attack that sneaks in an
UPDATEstatement on product data
- In practice two of these three ways should turn out to be dead ends
Request a hidden resource on server through server