Files should be created with appropriate access permissions. Creating a file with insufficient file access permissions may allow unintended access to program-critical files. File permissions are heavily dependent on the underlying operating system. This recommendation offers three examples of how to specify access permissions for newly created files using standard C and POSIX functions.
Non-
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Compliant Code Example
The fopen() function does not provide a mechanism to specify file access permissions. In the example below, if the call to fopen() creates a new file, the access permissions for that file will be implementation defined. Note that on POSIX compliant systems the permissions may be influenced by the value of umask(). More information on umask() is available in the POSIX specification.
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File *fptr;
errno_t res = fopen_s(&fptr,file_name, "w");
if (res != 0) {
/* Handle Error */
}
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Non-
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Compliant Code Example (POSIX)
Using the POSIX function open() to create a file but failing to provide access permissions for that file may cause that file to be created with unintended access permissions. This omission has been known to lead to vulnerabilities; for instance, CVE-2006-1174.
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