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Chapter 5. Ensuring support for common encryption types in AD and RHEL

By default, Identity Management establishes a cross-realm trust with support for AES-128, and AES-256 Kerberos encryption types, having deprecated the less secure RC4 type. However, Active Directory (AD) user credentials and trusts between AD domains might still rely solely on RC4 encryption.

RC4 encryption has been deprecated and disabled by default, as it is considered less secure than the newer AES-128 and AES-256 encryption types. In contrast, Active Directory (AD) user credentials and trusts between AD domains support RC4 encryption and they might not support AES encryption types.

Without any common encryption types, communication between IdM and AD child domains might not work, or some AD accounts might not be able to authenticate.

Procedure

  1. To enable AES encryption support in Active Directory (recommended), see the following Microsoft article: AD DS: Security: Kerberos "Unsupported etype" error when accessing a resource in a trusted domain.

  2. To enable RC4 support in RHEL, if your Active Directory environment does not support AES encryption, set the cryptographic subpolicy to support legacy algorithms on every IdM trust controller, trust agent, and client that authenticates against AD Domain Controllers: 

    [root@host ~]# update-crypto-policies --set LEGACY:AD-SUPPORT-LEGACY
     
    Setting system policy to LEGACY:AD-SUPPORT-LEGACY
Note: System-wide crypto policies are applied on application start-up.
It is recommended to restart the system for the change of policies
to fully take place.
  3. Restart the host.
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