Setting the default umask

Modern Mac computers have inherited the concept of a umask from Unix computers. The umask is used to determine what permissions files and directories should be created with by default.

I've never known how to set the umask on a Mac in such a way that it effects the entire login session (eg. Finder, Apps and shell). I haven't yet confirmed the below but I will soon.

There's a poorly documented feature we've found to set a umask for the entire login session. Create a dir under the home account called .MacOSX. Inside there make a text file called environment.plist. Inside the file, place the following:
   <?xml version="1.0" encoding="UTF-8"?>
   <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
   <plist version="1.0">
   <dict>
       <key>umask</key>
       <integer>000</integer>
   </dict>
   </plist>
This works for most things, including the finder. Some apps seem to ignore it and set their own permissions anyways, like Maya and Photoshop, but this will at least work for Finder and most Apple apps... Hope this is helpful.

With much thanks to the Studio SysAdmin list.