Re: URGENT SECURITY ADVISORY FOR SSH SECURE SHELL 3.0.0

[Casper Dik <Casper.Dik () Sun COM>]

> On 21 Jul 2001, Dale Southard wrote:
>
> > Sshd should probably be constraining its match to the length of the
> > crypt() output rather than the length of the password file entry.  [I
> > say ``probably'' here because some systems (AIX) seem to produce null
> > password file hashes when `passwd` is given a null password.  If that
> > behavior is due to the underlying crypt() function, then the
> > ``probably'' suggestion I just made yields remote root on those
> > systems.]
>
> What's wrong with just using `strcmp' (i.e. no constraint at all)?  After
> all, what you want to know is just whether the two strings are identical,
> period.  And unless crypt() and /etc/shadow are both broken, it will stop 
> at the right place.  I realize it goes against the reflexive "only strn*
> functions are safe" idea, but that shouldn't substitute for thinking...

It does look a knee-jerk str* is bad, use strn* type of code change.

strcmp() is *never* dangerous.  strncmp() is really only useful
for prefix checking and should not be introduced as part of "security fixes".

Casper