Resolve vulnerability: Insecure string processing function (strcpy)

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

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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

• Severity: high
• Location: cplusplus/src/hello.cpp:7

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 (14 characters including the newline and null terminator) is less than the destination buffer size (40 characters), the use of strcpy is still considered unsafe as a general practice.

In this specific case, the risk is minimal because:

1. The source string is a constant and its length is known.
2. The destination buffer is large enough to accommodate the source string.

However, using strcpy can lead to buffer overflows if the source string is longer than the destination buffer, which could happen if the code is modified in the future without careful consideration of buffer sizes.

To improve the security of this code and prevent potential future vulnerabilities, we should replace strcpy with a safer alternative that includes bounds checking.

Summary:

1. The reported vulnerability is the use of the insecure strcpy function, which is prone to buffer overflow issues (CWE-120).

2. The fix replaces strcpy with strncpy, which allows for specifying the 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 specified size.

   This fix addresses the security concern by preventing potential buffer overflows, even if the source string were to change in the future. It maintains the original functionality while adding bounds checking.

3. While the original code wasn't immediately dangerous due to the use of a constant string shorter than the buffer, this fix improves the overall security and robustness of the code, making it safer for potential future modifications.

Identifiers:

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