SV-226327r794539: Kerberos encryption types must be configured to prevent the use of DES and RC4 encryption suites. | Microsoft Windows Server 2012/2012 R2 Domain Controller STIG SCAP Benchmark

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Assessment Title

Rule Text

Kerberos encryption types must be configured to prevent the use of DES and RC4 encryption suites.

Description

Discussion Text

Certain encryption types are no longer considered secure. The DES and RC4 encryption suites must not be used for Kerberos encryption. Note: Removing the previously allowed RC4_HMAC_MD5 encryption suite may have operational impacts and must be thoroughly tested for the environment before changing. This includes but is not limited to parent\child trusts where RC4 is still enabled; selecting "The other domain supports Kerberos AES Encryption" may be required on the domain trusts to allow client communication across the trust relationship.

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

IA Controls

NIST SP 800-53

Not mappedCCI-000803CCE-24147-1V-21954SV-53179

References

DPMS Target Microsoft Windows Server 2012-2012 R2 DC DISA DPMS Target Microsoft Windows Server 2012-2012 R2 DC 4217

Checks

DISA STIG (Manual Reference)

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\Microsoft\Windows\CurrentVersion\Policies\System\Kerberos\Parameters\

Value Name: SupportedEncryptionTypes

Value Type: REG_DWORD
Value: 0x7ffffff8 (2147483640)

Note: Removing the previously allowed RC4_HMAC_MD5 encryption suite may have operational impacts and must be thoroughly tested for the environment before changing. This includes but is not limited to parent\child trusts where RC4 is still enabled; selecting "The other domain supports Kerberos AES Encryption" may be required on the domain trusts to allow client communication across the trust relationship.

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.fso.windows:def:4590
# Kerberos encryption types must be configured to prevent the use of DES and RC4 encryption suites.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# Verifies 'Network Security: Configure encryption types allowed for Kerberos' is set to 'Enabled' with 'AES128_HMAC_SHA1', 'AES256_HMAC_SHA1', 'Future encryption types' selected
# registry_object (registry_test)
function test_1 {
  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\Microsoft\Windows\CurrentVersion\Policies\System\Kerberos\Parameters').GetValueKind('SupportedEncryptionTypes').ToString()]) -eq 'reg_dword') -and (((Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\System\Kerberos\Parameters' -Name 'SupportedEncryptionTypes' -ErrorAction SilentlyContinue) | Select-Object -ExpandProperty 'SupportedEncryptionTypes') -eq 2147483640))
}

if (test_1) {
  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_2012_and_2012_r2_dc target this check assesses.

# OVAL Definition: oval:mil.disa.fso.windows:def:4590
$regPath = "HKLM:\Software\Microsoft\Windows\CurrentVersion\Policies\System\Kerberos\Parameters"
if (Test-Path $regPath) {
    $regValue = (Get-ItemProperty -Path $regPath -Name SupportedEncryptionTypes).SupportedEncryptionTypes
    if ($regValue -band 2147483640 -eq 2147483640 -and $regValue -band 4 -eq 0) {
        Write-Output "PASS"; exit 0
    }
}
Write-Output "FAIL"; exit 1

Remediation

Configure the policy value for Computer Configuration >> Windows Settings >> Security Settings >> Local Policies >> Security Options >> "Network security: Configure encryption types allowed for Kerberos" to "Enabled" with only the following selected:

AES128_HMAC_SHA1
AES256_HMAC_SHA1
Future encryption types

Note: Removing the previously allowed RC4_HMAC_MD5 encryption suite may have operational impacts and must be thoroughly tested for the environment before changing. This includes but is not limited to parent\child trusts where RC4 is still enabled; selecting "The other domain supports Kerberos AES Encryption" may be required on the domain trusts to allow client communication across the trust relationship.