[UNIX] ncpfs Buffer Overflow

From: SecuriTeam (support_at_securiteam.com)
Date: 09/08/05

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Date: 8 Sep 2005 13:51:34 +0200

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      ncpfs Buffer Overflow
    ------------------------------------------------------------------------

    SUMMARY

    The <http://www.gsp.com/cgi-bin/man.cgi?section=1&topic=ncplogin>
    ncplogin command is used to create a permanent connection to a NetWare
    server. Permanent connections will stay connected even if no applications
    use them.

    By passing a long tree parameter to ncplogin and ncpmap, it is possible to
    crash the program and possibly gain higher privileges.

    DETAILS

    Vulnerable Systems:
     * ncpfs version 2.2.4-1 from fedora core 2

    Both ncplogin and ncpmap are installed setuid by default, thus
    exploitation allows privilege escalation.

    Vulnerable Code:
    From nwclient.c:
    static void strcpy_cw(wchar_t *w, const char* s) {
        while ((*w++ = *(const nuint8*)s++) != 0);
    }

    NWDSCCODE NWDSCreateContextHandleMnt(NWDSContextHandle* ctx, const
    NWDSChar * treeName){
    ..
    wchar_t wc_treeName[MAX_DN_CHARS+1];

        if (!treeName)
            return ERR_NULL_POINTER;

        strcpy_cw (wc_treeName,treeName);

    Proof of Concept:
    The following two command lines will cause the triggering of the
    vulnerability:
    ncplogin -T `perl -e '{print"a"x"330"}'`
    ncpmap -T `perl -e '{print"a"x"330"}'` /

    ADDITIONAL INFORMATION

    The information has been provided by <mailto:appelast@drumnbass.art.pl>
    Karol Wi sek.

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