Private file permissions by default

[hinto-janai]

Feature

cuprated creates files with global read/execute permissions (rwxr-xr-x), any other process running on the machine can read these files.

Certain libraries that create files (e.g. LMDB) may set their own umask although cuprated does not. It would be prudent to set a private global umask before creating files:

umask	file permissions
027	rwxr-x---
007	rwx------

Implementation

Windows will need a separate impl.

fn main() {
    // SAFETY: calling C.
    unsafe {
        libc::umask(0o027);
    }

    /* ... */
}