SV-225010r971545: Unauthenticated Remote Procedure Call (RPC) clients must be restricted from connecting to the RPC server. | Microsoft Windows Server 2016 STIG SCAP Benchmark

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Assessment Title

Rule Text

Unauthenticated Remote Procedure Call (RPC) clients must be restricted from connecting to the RPC server.

Description

Discussion Text

Unauthenticated RPC clients may allow anonymous access to sensitive information. Configuring RPC to restrict unauthenticated RPC clients from connecting to the RPC server will prevent anonymous connections.

How this relates to the STIG checklist: STIG vs SCAP benchmark.

IA Controls

NIST SP 800-53

Not mappedCCI-001967SV-88203V-73541

References

DPMS Target Microsoft Windows Server 2016 DISA DPMS Target Microsoft Windows Server 2016 4205

Checks

DISA STIG (Manual Reference)

This applies to member servers and standalone or nondomain-joined systems. It is NA for domain controllers.

If the following registry value does not exist or is not configured as specified, this is a finding.

Registry Hive:  HKEY_LOCAL_MACHINE
Registry Path:  \SOFTWARE\Policies\Microsoft\Windows NT\Rpc\

Value Name:  RestrictRemoteClients

Type:  REG_DWORD
Value:  0x00000001 (1)

SCC Automation Reference

The reconstructed evaluation script behind this rule's OVAL check(s) — every module a compound check combines, with this rule's own concrete values and DISA's SCC tool's real per-module mechanism curated from static teardown of SCC releases.

# Windows PowerShell
# Reconstructed from oval:mil.disa.stig.windows:def:1174
# Unauthenticated Remote Procedure Call (RPC) clients must be restricted from connecting to the RPC server.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# System is a DC
# wmi57_object (wmi57_test)
function test_1 {
  return ((((Get-CimInstance -Namespace 'root\cimv2' -Query 'SELECT DomainRole FROM win32_computersystem' | Select-Object -First 1) | Select-Object -ExpandProperty 'DomainRole') -eq '5') -or (((Get-CimInstance -Namespace 'root\cimv2' -Query 'SELECT DomainRole FROM win32_computersystem' | Select-Object -First 1) | Select-Object -ExpandProperty 'DomainRole') -eq '4'))
}
# Verifies 'Restrict Unauthenticated RPC clients' is set to 'Enabled' and 'Authenticated'
# registry_object (registry_test)
function test_2 {
  return (((@{String='reg_sz';ExpandString='reg_expand_sz';Binary='reg_binary';DWord='reg_dword';MultiString='reg_multi_sz';QWord='reg_qword';None='reg_none'}[(Get-Item -Path 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Rpc').GetValueKind('RestrictRemoteClients').ToString()]) -eq 'reg_dword') -and (((Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Rpc' -Name 'RestrictRemoteClients' -ErrorAction SilentlyContinue) | Select-Object -ExpandProperty 'RestrictRemoteClients') -eq 1))
}

if ((test_1 -or test_2)) {
  Write-Output "PASS"
} else {
  Write-Output "FAIL"
}

Assessment Script Powered by AISyntax-verified

A standalone PowerShell script to assess this control automatically. Review before running it in your environment.

Syntax-checked as valid PowerShell. Not executed here — running it for real needs the actual ms_windows_server_2016 target this check assesses.

# OVAL Definition: oval:mil.disa.stig.windows:def:1174
if (!(Get-CimInstance -ClassName Win32_ComputerSystem).DomainRole -in 4,5) { $isDC = $false } else { $isDC = $true }
if ($isDC -or (Test-Path -Path "HKLM:\SOFTWARE\Policies\Microsoft\Windows NT\Rpc\RestrictRemoteClients" -ErrorAction SilentlyContinue) -and (Get-ItemProperty -Path "HKLM:\SOFTWARE\Policies\Microsoft\Windows NT\Rpc\RestrictRemoteClients" -Name RestrictRemoteClients -ErrorAction SilentlyContinue).RestrictRemoteClients -eq 1) { Write-Output "PASS"; Exit 0 } else { Write-Output "FAIL"; Exit 1 }

Remediation

Configure the policy value for Computer Configuration >> Administrative Templates >> System >> Remote Procedure Call >> "Restrict Unauthenticated RPC clients" to "Enabled" with "Authenticated" selected.