From Fedora Project Wiki

File Permissions

Permissions on files MUST be set properly. Inside of /usr, files should be owned by root:root unless a more specific user or group is needed for security . They MUST be universally readable (and executable if appropriate). Outside of /usr, non-config and non-state files SHOULD be owned by root:root, universally readable (and executable if appropriate) unless circumstances require otherwise.

The default file mode is 0644 or 0755. Directories SHOULD be mode 0755. Most well behaved build scripts and rpm will use these defaults. If the directory needs to be group writable, it SHOULD also have the setgid bit set so that files written there are owned by that group. These directories SHOULD have mode 2775.

The %defattr directive in the %files list SHOULD ONLY be used when setting a non-default value, or to reset to the default value after having set a non-default value.