Title

Kerberos encryption types must be configured to prevent the use of DES and RC4 encryption suites. (Cat II impact)

Discussion

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.

Check Content

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.

Fix Text

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.

Additional Identifiers

Rule ID: SV-225504r569185_rule

Vulnerability ID: V-225504

Group Title: SRG-OS-000120-GPOS-00061

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.