what are the implications of shell doing setuid(getuid())?

[BALDWIN]

[ what would break if /bin/sh did setuid(getuid()), setgid(getgid())? ]

> Well, shell scripts invoked by someone who was su'ed to someone else could
> fail, couldn't they, in this situation?  (The resulting spawned shells would
> not have the proper uid and gid.)

Nope, because su(1) sets both the effective *and* the real [ug]id.  The only
way to run the shell with real != effective is to exec it from a set[ug]id
C program (e.g., system(3C) or popen(3S)) or use #!/bin/sh in BSD (but it's
*real* easy to break set[ug]id #!/bin/sh files).
-- 
						Michael Baldwin
						AT&T Bell Labs
						{at&t}!whuxl!mike