10 Essential Tips for Writing Secure C++ Code

10 Essential Tips for Writing Secure C++ Code

Best Practices and Safer Alternatives

C++ is a powerful programming language that has been in use for many years, but it’s not without its risks. Writing secure C++ code is important to avoid vulnerabilities that can be exploited by attackers. Here are ten tips to help you write secure C++ code.

  1. Avoid Buffer Overflows: Buffer overflows occur when more data is written to a buffer than it can hold. This can cause data to be overwritten, leading to security vulnerabilities. Use the appropriate C++ data types and functions to avoid buffer overflows.

  2. Use RAII: RAII stands for Resource Acquisition Is Initialization. This means that resources are automatically acquired when an object is created, and automatically released when the object is destroyed. Use RAII to avoid resource leaks and memory errors.

  3. Use Smart Pointers: Smart pointers are a type of RAII that automatically manages memory allocation and deallocation. Use smart pointers to avoid memory leaks and dangling pointers.

  4. Use Exception Handling: Exception handling is a way to handle errors and exceptions in your code. Use exception handling to catch and handle errors and prevent your program from crashing.

  5. Sanitize User Input: Always sanitize user input to prevent injection attacks, buffer overflows, and other security vulnerabilities. Use regular expressions, input validation, and other techniques to sanitize user input.

  6. Use the Latest C++ Standards: The latest C++ standards include many security improvements over earlier versions. Always use the latest standards to take advantage of these improvements.

  7. Use Safe Libraries: Use safe libraries that have been tested and verified for security. Avoid using third-party libraries that have not been vetted for security vulnerabilities.

  8. Use Strong Typing: Strong typing ensures that variables are only used for their intended purpose. Use strong typing to prevent type confusion attacks and other security vulnerabilities.

  9. Use Static Analysis Tools: Static analysis tools can help you find security vulnerabilities in your code. Use these tools to identify and fix potential security issues.

  10. Follow the Principle of Least Privilege: The principle of least privilege means that code should only have access to the resources it needs to perform its task. Use this principle to minimize the risk of security vulnerabilities and prevent unauthorized access.

Here are a few less secure functions in C++ along with their safer alternatives:

  1. strcpy() and strncpy() — These functions can easily result in buffer overflows if the destination buffer is not large enough to hold the source string. Safer alternatives are strncpy_s() and strcpy_s() which take the size of the destination buffer as an argument and limit the number of characters copied.

  2. scanf() and gets() — These functions do not perform any bounds checking, which can result in buffer overflows. Safer alternatives are fgets() and scanf_s() which allow you to specify the size of the input buffer.

  3. rand() — This function generates pseudo-random numbers, which can be predictable and easily guessed by attackers. Safer alternatives are the C++11 standard library random number generators such as std::mt19937 and std::uniform_int_distribution.

  4. printf() — This function can be used to perform format string attacks, which can allow attackers to execute arbitrary code. Safer alternatives are snprintf() and fprintf_s() which limit the amount of data that can be printed and provide bounds checking.

By using these safer alternatives, you can greatly reduce the risk of security vulnerabilities in your C++ code.

Writing secure C++ code is crucial in today’s software development landscape. Security vulnerabilities can be costly and damaging to both the end-users and the reputation of the software developer. By following the tips outlined in this article, including using smart pointers, strong typing, exception handling, and following the principle of least privilege, you can minimize the risk of security vulnerabilities and improve the overall security of your C++ code.

It is also important to use secure coding standards, such as the CERT C++ Secure Coding Standard, and to keep up with the latest security updates and patches. Regularly testing your code with static analysis tools and vulnerability scanners can also help identify and fix potential security issues.

References:

  1. Secure Coding in C and C++, 2nd Edition by Robert C. Seacord

  2. Safe C++ Libraries. (2022). https://en.cppreference.com/w/cpp/header

  3. OWASP Top 10 Project. (2022). https://owasp.org/Top10/

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