What are the pros and cons of using non-executable memory regions to prevent buffer overflow attacks?

1 What is a buffer overflow attack?

A buffer is a fixed-size area of memory that stores data temporarily. A buffer overflow attack occurs when a malicious input exceeds the size of the buffer and overwrites the adjacent memory locations. This can cause unpredictable behavior, such as crashing the program, corrupting data, or executing arbitrary code. Buffer overflow attacks can exploit vulnerabilities in various types of software, such as web servers, operating systems, or network applications.

2 How does a buffer overflow attack work?

A buffer overflow attack typically involves two steps: finding a vulnerable buffer and injecting malicious code. The attacker first needs to identify a buffer that does not properly check the length or validity of the input. For example, a buffer that uses the unsafe function strcpy() to copy a user input without checking its size. The attacker then needs to craft a malicious input that contains the code they want to execute and some padding bytes to fill the rest of the buffer. The malicious input also needs to overwrite the return address of the function that contains the buffer, so that when the function returns, it jumps to the location of the injected code.

3 What are non-executable memory regions?

One of the mitigation strategies that can prevent buffer overflow attacks is to use non-executable memory regions. This technique marks certain regions of memory as non-executable, meaning that they cannot be used to store or run code. This way, even if the attacker manages to inject code into a buffer, they cannot execute it. Non-executable memory regions can be implemented at different levels, such as hardware, operating system, or compiler.

4 What are the pros of using non-executable memory regions?

Using non-executable memory regions can provide several benefits for preventing buffer overflow attacks, such as stopping code injection attacks without requiring source code changes or recompilation. This technique can also be combined with other mitigation techniques, like stack canaries or address space layout randomization, to further enhance security. In addition, it is supported by most modern hardware and operating systems, which provide features to enable non-executable memory regions.

5 What are the cons of using non-executable memory regions?

Using non-executable memory regions to prevent buffer overflow attacks can have some drawbacks. For example, it cannot stop all types of attacks, such as data or control flow modifications. Additionally, it may cause performance overhead due to extra memory protection checks and switches. Moreover, compatibility issues may arise if software relies on executable memory regions for legitimate purposes. Finally, advanced techniques such as return-oriented programming or jump-oriented programming can bypass this method of attack prevention.