[PATCH] correct_password: Handle NULL from crypt

[Rich Felker]

On Sun, Feb 09, 2014 at 12:52:50PM +0100, Denys Vlasenko wrote:
> On Mon, Feb 3, 2014 at 5:50 PM, Lauri Kasanen <curaga at operamail.com> wrote:
> > As with many other software, busybox was also broken by the glibc >=
> > 2.17 behavior change. Now crypt() returns NULL if either salt or
> > password is invalid.
> 
> What is "invalid password"?
> 
> I just tested and crypt() returns NULL if *salt* is invalid (say, "").
> It's on glibc 2.17.
> 
> The old behavior was to return ""?
> (I have no old glibc at hand to check it quickly).
> 
> Since we have exactly one crypt() call in the entire busybox,
> the easiest fix would be to just add
>     if (NULL) return "";
> there. Are there downsides to that?

Are you sure glibc used to return "" on invalid inputs? I thought it
returned something unmatchable. Returning "" is mildly dangerous since
you could end up storing a blank password in the database and allowing
logins with no password, but if that's protected against, you should
be fine.

Rich