Re: Linux UID/GID 'Feature'

[scoile () PATRIOT NET (Steve \)]

On Sat, 10 May 1997, David Phillips wrote:
[...]
> While trying to make a user entry in the /etc/passwd file unrecognized
> so I could demonstrate the use of valid UIDs, I placed a # in front of
> the UID.  My theory was that this would make it an invalid number and
> cause Linux to give an authentication failure.  (This worked as expect
> on SunOS 4.1.4) But then we tried to su to that user and were rewarded by
> being dumped to UID 0.  It didn't recognize the UID so it defaulted to 0.
> Cool huh?

Sounds like the system is just using atoi() to get the UID.  atoi()
reads to the first non-numeric character (in this case, the hash) and
interprets everything up to it as the number.  Since nothing precedes
the non-numeric character in your situation, zero (no value) is returned.

--
    Steve Coile           P a t r i o t  N e t      Systems Engineering
 scoile () patriot net      Patriot Computer Group        (703) 277-7737