One of the oldest and most common security vulnerabilities in software is buffer overflow vulnerabilities.
They are produced in all types of software, from operating systems to client/server applications and desktop software.
This often happens due to poor programming and a lack of input or poor validation on the application side.
In this article, we will see what exactly a buffer overflow is, how they work, and how they can turn into serious security vulnerabilities. We will also look at what happens when one occurs and mitigation techniques to minimize its harmful effects.
What Exactly Is a Buffer Overflow (Real-Life Examples)?
A memory buffer is an area in computer memory (RAM) intended to temporarily store data.
These types of buffers can be found in all programs and are used to store data for input, output, and processing.
Therefore, a buffer overflow is a situation in which a running program tries to write data out of the memory buffer that is not intended to store this data. An example of data stored in buffers is the login credentials or the hostname for an FTP server.
Furthermore, other data stored temporarily before processing may be stored in buffers.
This could literally be anything from user input fields, such as username and password fields, to input files used to import certain configuration files.
When a memory buffer overflow occurs and data is written out of the buffer, the running program may become unstable, hang, or return corrupted information.
The overwritten portions of memory may have contained other data important to the running application that is now overwritten and no longer available to the program.
They can even execute other (malicious) programs or commands and cause arbitrary code to be executed.
Different Types of Buffer Overflows (Including Most Vulnerable)
There are several different buffer overflow attacks that employ different strategies and target different pieces of code.
Below are some of the best known.
- Stack Overflow Attack – This is the most common type of attack and involves overflowing a buffer in the call stack.
- Heap Overflow Attack: This type of attack targets data in the open memory pool known as the heap.
- Integer Overflow: In an integer overflow, an arithmetic operation returns an integer (integer) that is too large for the type of integer intended to store it. This can cause a buffer overflow.
- Unicode Overflow – generated by inserting Unicodes into an input that expects ASCII characters (ASCII and Unicode are encoding standards that allow computers to render text).
Certain coding languages are more susceptible to buffer overflow than others.
C and C ++ are two popular languages with high vulnerability, as they do not contain built-in protection against accessing or overwriting data in their memory.
Windows, Mac OSX, and Linux contain code written in one or both languages.
Newer languages such as Java, PERL, and C # have built-in features that help reduce the chances of buffer overflows, but they cannot avoid it entirely.
Fortunately, buffer overflows in software can be prevented or mitigated in a number of ways.
Ways to Prevent & Mitigate Buffer Overflow
Mitigation is the process of minimizing the impact of a threat before or after the threat occurs.
This is exactly what we should do when it comes to buffer overflows. You can prevent them from happening before they happen (proactive).
But, since buffer overflows continue to occur, despite proactive actions to avoid them, we need mechanisms to minimize the impact when they do occur (reactive countermeasures).
Let’s take a look at how buffer overflow prevention and mitigation work.
- Prevention – The best and most effective solution is to prevent buffer overflow conditions from occurring in your code.
For example, when a maximum of 8 bytes is expected as input data, the amount of data that can be written to the buffer will be limited to 8 bytes at any one time.
In addition, programmers should use save functions, test code, and correct errors accordingly. Proactive buffer overflow prevention methods such as these should be used whenever possible to limit buffer overflow vulnerabilities.
Let’s explore 2 common protections that help mitigate the risk of exploitation:
- Address space randomization: Randomly reorders the address space locations of key data areas of a process. Buffer overflow attacks generally rely on knowing the exact location of important executable code, randomizing the address spaces makes this nearly impossible.
- Data execution prevention: marks certain areas of memory as executable or non-executable, preventing an exploit from executing the code found in a non-executable area.
2. Mitigation – This is a reactive approach and focuses on minimizing the harmful impact. An example of effective mitigation is a modern operating system that protects certain areas of memory against writing or executing.
This will prevent an attacker from writing arbitrary code into memory when a buffer overflow occurs. Implementations like DEP, ASLR, SEHOP, and executable space and pointer protection try to minimize the negative impact of a buffer overflow.
This does not prevent this from occurring, but it does minimize the impact. Another form of passive buffer overflow detection is to use intrusion detection systems (IDS) to analyze network traffic.
Memory corruption failures, like other types of weaknesses, are caused by human errors that can exist at any stage in the development process of computer systems.
It is important to make engineers aware of non-functional requirements and good programming practices that help reduce the risk of experiencing vulnerabilities in systems.
When developing applications it is important to consider the first line of defense.
The analysis of security requirements, good design and implementation practices, and adequate quality control with an adequate set of tests, is essential to reduce the risk of experiencing this type of failure.