You can consider a stack as a pile of trays put together, one on top of the other. Objects in the stack obey the LIFO rule, i.e., Last in First out. Stacks are data structures of a fixed size where you can store a collection of objects. But first, we need to know various terms related to memory and buffer. Here, we will walk through a common type of buffer overflow attack called Stack Overflow. To protect against buffer overflow attacks, we should know how buffer overflow attacks are performed. Protecting Against Buffer Overflow Attacks Even attackers with less experience in buffer overflow attacks can make use of the publicly disclosed exploits and compromise the vulnerable software. Like this, every year, tons of exploits and vulnerabilities are publicly disclosed on platforms such as Exploit-db, PacketstormSecurity, and more. This results in a complete compromise of the application. If an attacker can control the location of where overflowed characters (i.e., ORD) got written, they can store these characters where the correct password was written, causing the new password to become ORD. To check whether the password is correct or not, you compare it with the initially configured password, stored in a memory location of the program. ORD will be written in a different, adjacent location, possibly overwriting existing data. However, if a user uses PASSWORD as their password, only PASSW will be stored in the initialized buffer. A password like PASS would be acceptable. You estimated that the password would not be longer than five characters and allocated space accordingly. Suppose you have developed an application that protects users’ files with passwords, but your password checking functionality has a buffer overflow vulnerability. What if the person causing the buffer overflow is not just an uninformed user but an infamous hacker who is trying to compromise your application? With precision, it is possible to control the behavior of the buffer overflow. This crash would cause a DOS, i.e., Denial of Service attack, resulting in the server becoming unavailable to everyone. However, when this happens to production-level software, which is supposed to run seamlessly without any maintenance for an extended period, such as a web server, it will immediately crash. Usually, this would not seem like much of a big deal. In simple cases, the overwritten space does not belong to the user, resulting in a segmentation fault, and the program will crash. If a user enters an input larger than 25 characters, the spillover of 5 characters will be written in memory locations adjacent to the allocated buffer, overwriting any data that was initially stored there. However, the developer forgets to implement a check to assert that the user input id is less than 20 characters. The same goes for the buffer overflow attacks.Ī programmer implements a function that initializes a buffer space in memory with the capacity to store 20 characters, thinking that users will only enter up to 20 characters. If you do not stop, water will spill on the floor, a place where you did not intend to fill water. You start filling the bucket with water, and after a while, that bucket will be full. You want to fill that bucket with water and keep the floor dry. Due to this, user-supplied input is written into the wrong memory space.įor example, consider a bucket with a capacity of 1 liter. The main reason behind them is poorly implemented bound checking on user input. Since then, various buffer overflow vulnerabilities have been discovered and reported.īuffer overflow attacks generally occur when you try to write to a memory location you do not own. Since the issue of “ Smashing the stack for fun and profit ” by Alp1 in 1960, buffer overflows continue to be one of the most crucial vulnerabilities in the Information Security Domain. However, even if it were possible to write bugless software, the modular nature of software development makes it impossible to do so because of the libraries and legacy code snippets used during development that may create bugs and open security vulnerabilities. When writing software code, the ideal best practice is to write it without any bugs.
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