Fixed ringtone saving

[nijel]

Potential fix for https://github.com/gammu/python-gammu/security/code-scanning/25

In general, to avoid creating world-writable files you should not rely on the process umask. Instead, when creating new files, use APIs that accept an explicit mode (such as open with O_CREAT) and specify restrictive permissions, typically S_IRUSR | S_IWUSR (read/write only for the owner). If you need a FILE * stream, you can then wrap the file descriptor with fdopen.

For this specific case in gammu/src/gammu.c, the problematic path is when value is a Unicode string and the code calls f = fopen(name, "wb");. Replace this with a sequence that:

1. Opens the file descriptor with open(name, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);.
2. Wraps it in a FILE * using fdopen(fd, "wb");.
3. Handles errors by closing the descriptor on failure and setting the same Python exception as today.

We also need to ensure the required headers are present. The file currently includes standard C and project headers, but not the POSIX ones for open and permission constants. Add #include <fcntl.h> and #include <sys/stat.h> near the other system includes at the top of the file. This preserves existing functionality: the file is still opened for binary write and truncated/created as before, but with explicitly owner-only read/write permissions.

Suggested fixes powered by Copilot Autofix. Review carefully before merging.

[Copilot]

Pull request overview

This pull request attempts to fix a code scanning alert about file creation without restricting permissions by replacing fopen() with POSIX open() + fdopen() to explicitly set file permissions to owner-only read/write.

Changes:

• Added includes for <fcntl.h> and <sys/stat.h> for POSIX file creation APIs
• Modified file opening logic in gammu_SaveRingtone() to use open() with explicit permissions (S_IRUSR | S_IWUSR) instead of fopen()
• Added proper error handling for the file descriptor and cleanup on failure

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[Copilot]

The headers <fcntl.h> and <sys/stat.h> are POSIX headers that are not available on Windows. Since this project supports Windows builds (as evidenced by the CI workflows), these includes should be wrapped in platform-specific guards or replaced with Windows-compatible alternatives.

For Windows compatibility, consider using <io.h> and <sys/stat.h> (Windows has a limited version) with appropriate #ifdef _WIN32 guards.

Suggested change

	/* File creation and permissions */
	#include <fcntl.h>
	#include <sys/stat.h>
	/* File creation and permissions */
	#ifdef _WIN32
	#include <io.h>
	#include <sys/stat.h>
	#else
	#include <fcntl.h>
	#include <sys/stat.h>
	#endif

[Copilot]

The POSIX open() function and the permission constants S_IRUSR and S_IWUSR are not directly available on Windows. This code will fail to compile on Windows, which is a supported platform according to the CI configuration in .github/workflows/test.yml and .github/workflows/setup.yml.

On Windows, you should either:

1. Use _open() with _S_IREAD | _S_IWRITE and include <io.h>, or
2. Add platform-specific compilation guards with #ifdef _WIN32 to use different approaches for Windows vs POSIX systems, or
3. Use a cross-platform abstraction.

The same issue applies to the close() function at line 6108, which should be _close() on Windows.

[Copilot]

The function parameter parsing uses &file to receive the first argument "Filename" (line 6070), but then the code checks PyUnicode_Check(value) and PyObject_AsFileDescriptor(value) instead of checking file. The variable value contains the second parameter "Ringtone" (a dictionary), not the filename.

This means the file opening logic at line 6100 will never be reached for string filenames, because value is always a dictionary (enforced by the PyDict_Type check in line 6070). The code should be checking and using the file variable instead of value for file descriptor and Unicode string checks.

[nijel]

@copilot Please address review comments and fix compilation on Windows.

[Copilot]

@nijel I've opened a new pull request, #198, to work on those changes. Once the pull request is ready, I'll request review from you.