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Resolve vulnerability: Insecure string processing function (strcpy)

Igor Drozdovrequested to merge
remediate/insecure-string-processing-function--strcpy-D20250312T171111 into main

MR created from vulnerability: Insecure string processing function (strcpy)

AI GENERATED FIX

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Description:

The strcpy family of functions do not provide the ability to limit or check buffer sizes before copying to a destination buffer. This can lead to buffer overflows. Consider using more secure alternatives such as strncpy and provide the correct limit to the destination buffer and ensure the string is null terminated.

For more information please see: https://linux.die.net/man/3/strncpy

If developing for C Runtime Library (CRT), more secure versions of these functions should be used, see: https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/strncpy-s-strncpy-s-l-wcsncpy-s-wcsncpy-s-l-mbsncpy-s-mbsncpy-s-l?view=msvc-170

Analysis:

The vulnerability report indicates an issue with the use of the strcpy function, which is known to be insecure due to its lack of bounds checking. This is reflected in the CWE-120 (Buffer Copy without Checking Size of Input) identifier.

The vulnerable code section highlights the use of strcpy(hello, "Hello World!\n");. While the source string "Hello World!\n" is a constant and its length is known, strcpy is still considered unsafe because it doesn't perform any bounds checking.

In this specific case, the buffer hello is declared with a size of 40 characters, which is more than enough to hold the "Hello World!\n" string (14 characters including the null terminator). However, using strcpy is still not recommended as it could lead to buffer overflows if the source string were to change in the future or if this code were to be modified without careful consideration of the buffer size.

The potential security implication is that if a longer string were to be copied into hello using strcpy, it could overflow the buffer and potentially lead to memory corruption or code execution vulnerabilities.

While this specific instance may not pose an immediate threat, it's good practice to use safer alternatives to strcpy to prevent potential future vulnerabilities.

Summary:

  1. The reported vulnerability is the use of the insecure strcpy function, which does not perform bounds checking and can lead to buffer overflows (CWE-120).

  2. The fix replaces strcpy with strncpy, which allows specifying a maximum number of characters to copy. Here's a breakdown of the changes:

    • strncpy(hello, "Hello World!\n", sizeof(hello) - 1); copies at most sizeof(hello) - 1 characters, leaving room for the null terminator.
    • hello[sizeof(hello) - 1] = '\0'; ensures that the string is null-terminated, as strncpy doesn't guarantee null-termination if the source string is as long as or longer than the size argument.

    This fix addresses the security concern by preventing potential buffer overflows, even if the source string were to change in the future. It ensures that we never write beyond the bounds of the hello array.

  3. While the original code wasn't immediately dangerous due to the known length of the string, this fix follows the principle of defensive programming. It makes the code more robust against future changes and helps prevent potential vulnerabilities that could arise from modifications to the code.

Remember to include the necessary header for strncpy:

#include <cstring>  // for strncpy

This change maintains the functionality of the original code while significantly improving its security posture.

Identifiers:

  • CWE-120
  • Flawfinder - strcpy
  • A1:2017 - Injection
  • A03:2021 - Injection
  • flawfinder.strcpy-1

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