Re: buffer overflows in cracklib?!

From: Rick Byers (rickbat_private)
Date: Mon Dec 15 1997 - 07:23:01 PST

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    I just spoke with Alec Muffett, the author of cracklib and he pointed me
    to the new version (2.6) on his homepage:
    http://www.users.dircon.co.uk/~crypto/.  I still see a lot of strcpy's,
    but that particular one is no longer a problem, and I havn't had the time
    to check the whole thing out thoroughly.  CERT is supposed to be releasing
    and advisory about it soon...
            Rick
    
    On Sun, 14 Dec 1997, Jon Lewis wrote:
    
    > While looking at compiling the latest shadow utils with cracklib support,
    > I was kind of surprised when gcc complained about things like:
    >
    > fascist.c:220: warning: passing arg 2 of `strcpy' makes pointer from
    > integer without a cast
    >
    > strcpy in security software...hmm....so I took a look at fascist.c and was
    > pretty surprised to find:
    >
    > char gbuffer[STRINGSIZE];
    > ...
    > strcpy(gbuffer, Lowercase(pwp->pw_gecos));
    >
    > STRINGSIZE is defined in cracklib/packer.h:#define STRINGSIZE    256
    >
    > So...to test this, I used chfn on a Red Hat 4.2 system to set my full-name
    > to a string of about 300+ chars, and tried to change my passwd.
    >
    > $ chfn
    > Changing finger information for jlewis.
    > Password:
    > Name [hmm]:
    > 11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
    > Office []:
    > Office Phone []:
    > Home Phone []:
    >
    > Finger information changed.
    > $ passwd
    > Changing password for jlewis
    > (current) UNIX password:
    > New UNIX password:
    > Segmentation fault
    > $
    >
    > I took a look at Aleph One's Smashing the Stack paper, but got nowhere
    > since chfn (at least on RH 4.2) won't let me have control characters in
    > the gecos field.  Still, shouldn't cracklib be fixed?  I'm not installing
    > it without some sprintf->snprintf mods.
    >
    > ------------------------------------------------------------------
    >  Jon Lewis <jlewisat_private>  |  Unsolicited commercial e-mail will
    >  Network Administrator       |  be proof-read for $199/message.
    >  Florida Digital Turnpike    |
    > ______http://inorganic5.fdt.net/~jlewis/pgp for PGP public key____
    >
    
    =========================================================================
    Rick Byers                                      Internet Access Worldwide
    rickbat_private                                              System Admin
    University of Waterloo, Computer Science                    (905)714-1400
    http://www.iaw.on.ca/rickb/                         http://www.iaw.on.ca/
    



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