Which commands (in /bin & /usr/bin) must have set user ID (for root)

[Ray Moody]

>> What surprised me about the list Jim replied with was that most of the
>> commands
>> were -rws......!  Why should a setuid command *ever* be writeable? - it's just
>> *inviting* attempts to find a bug and convince the command to write
>> over itself.
>
>First off, root can overwrite any file regardless of perms, yes/no?  Second,
>ever see "error:  text busy" ?  You cannot remove or write over a file that
>is running somewhere on the system (or, to be picky, has the sticky bit set
>and has been run)

    Anyway, if a setuid program overwrites itself, it is no longer setuid!
It says in the manual page for write (2):

     If the real user is not the super-user, then _w_r_i_t_e clears
     the set-user-id bit on a file.  This prevents penetration of
     system security by a user who "captures" a writable set-
     user-id file owned by the super-user.

>> What irks me more, though, is that the "lp" commands all run setuid-lp
>> setgid-bin; this means that in a directory which lp can't access ( e.g. 700),
>> 	lp foo
>> fails, though
>> 	lp <foo
>
>then make lp suid root :-)

   There shouldn't be any smiley face here.  This is a perfectly reasonable
suggestion.  Just MAKE SURE IT CALLES ACCESS (2)!  Out lpr program runs setuid.

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array                                                 Ray Moody
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