ksu: Remove ENABLE_SUID_K5SU

[cy]

Summary

ksu without setuid is useless. This affects binary-only (traditional
install and pkgbass) users.

Reported by: Dan Mahoney <[e-mail]>
MFC after: 3 days
MFC to: 15/stable

Test Plan

Running here.

[ivy]

can we just remove this entirely in favour of su(1) with pam_ksu(8)? i believe this provides the same functionality, with the benefit of removing a setuid executable and allowing the user to easily configure whether they want this enabled or not.

otherwise, we're adding another unconfigurable setuid executable to the base system, which is not ideal from a security standpoint.

[cy]

In D52463#1198005, @ivy wrote:

can we just remove this entirely in favour of su(1) with pam_ksu(8)? i believe this provides the same functionality, with the benefit of removing a setuid executable and allowing the user to easily configure whether they want this enabled or not.

otherwise, we're adding another unconfigurable setuid executable to the base system, which is not ideal from a security standpoint.

No. Because ksu is,

a) Provided by Kerberos (MIT and Heimdal). Any users and scripts that expect the file to be there must now be FreeBSD-ized.

b) ksu is a different application than su.

c) su(1) never did work with kerberos.

[cy]

Dan Mahoney <[e-mail]> has notified me they use a puppet script to chmod ksu. As long as people know to do this fine by me.