Is the deb installation process protected against Man In The Middle Attacks that would alter the install script?
It seems if not, then it would be possible for a Man In The Middle Attack to place code that fundamentally alters the system in the deb install script. Because all installations require root privileges, the invitation is wide open for exploits.
Would we be better off not using custom deb installing scripts as root? I know that links, shortcuts, and app directories need to be copied as root. This could be done by a script already residing on Ubuntu and shipping with Ubuntu. The deb should fit it's expected protocol. It would simply hand it places to move files from the package and appropriate shortcut creation locations, etc. It would have restrictions to never delete, rename, without explicit approval (for updating apps).
If the deb file never asked to be run as root, then an installation could never compromise fundamental parts of the system.
apt-getwill warn you if you try to download an unsecured package. It is part of a security mechanism specifically in place to handle man-in-the-middle attacks.