OSEC

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From: Markus Hallströ (tubbsfreebsd.se)
Date: Fri Apr 19 2002 - 17:43:33 CDT

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    This just showed up on vuln-dev

    On Fri, 2002-04-19 at 15:48, Marcell Fodor wrote:
    >
    >
    > The bug affects servers offering Kerberos TGT
    > and/or AFS Token passing. The vulnerability can lead
    > to a root compromise.
    >
    > more : mantra.freeweb.hu
    >
    > Marcell Fodor
    >
     
    on http://mantra.freeweb.hu I get the following information

    18.04.2002
    security bug report:

    OpenSSH 2.2.0 - 3.1.0 server contains a locally exploitable buffer overflow.
    The bug affects servers offering Kerberos TGT and/or AFS Token passing.
    The vulnerability can lead to a root compromise.

     bug details:
     
        radix.c
        GETSTRING macro in radix_to_creds function may cause buffer overflow.
        affected buffers:
        
            creds->service
            creds->instance
            creds->realm
            creds->pinst

        user can exploit the vulnerability by sending malformed request for:
        
            1. pass Kerberos IV TGT
            2. pass AFS Token

     For security considerations the CREDENTIALS structure is erased at the end of
     the auth_krb4_tgt function (auth_krb4.c). This makes code injection impossible at
     the first look, since the user supplied code is cleared.
     Well, it's all there! Check the temp[] buffer in radix_to_creds() function. This is
     the place, where the server decoded the ticket.
                   
     It should be considered in further versions to clear the temp buffer prior
     returning from the radix_to_creds function.

     Is this known? should I worry?

    --
    /Markus
    

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