Don’t allow other users to connect by default

[Demi-Marie]

This is the most secure default configuration, and prevents local
privilege escalation vulnerabilities. On Unix, permissions are set to
0o600, while on Windows, the DACL of the process’s token is used.

[NikVolf]

Thanks @demimarie-parity

I am not sure this should be default.

Have you researched how other libraries are organised and what users expect to be default (deny or allow all)?

[Demi-Marie]

@NikVolf Personally, I expect the default to be to deny access. Furthermore, overly strict permissions will be caught during testing, while overly loose permissions will not unless explicitly checked for.

[Demi-Marie]

@NikVolf I looked at permissions and found:

• Connecting to an AF_UNIX socket requires write access to the socket. Since default umasks deny write access to other users, this is safe. It also means that using 0o600 permissions does not change anything in normal situations.
• On Windows, default permissions for a named pipe give read access to everyone, and full control to the creator of the pipe, LocalSystem, and administrators. LocalSystem and Administrators can do anything, so that is fine. Read-only access is useless in most cases.

[dlon]

Could you release a new version including these changes on crates.io? It will allow us to get rid of some workarounds.