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Bug 1851442 - Update crypto policy to allow AD-SUPPORT when installing Samba
Summary: Update crypto policy to allow AD-SUPPORT when installing Samba
Keywords:
Status: CLOSED CURRENTRELEASE
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: Documentation
Version: 8.3
Hardware: Unspecified
OS: Unspecified
high
high
Target Milestone: rc
: 8.5
Assignee: Marc Muehlfeld
QA Contact:
URL:
Whiteboard:
Depends On: 1851458
Blocks:
TreeView+ depends on / blocked
 
Reported: 2020-06-26 14:10 UTC by Andreas Schneider
Modified: 2021-07-14 08:44 UTC (History)
11 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
.`krb5` now only requests permitted encryption types Previously, permitted encryption types specified in the `permitted_enctypes` variable in the `/etc/krb5.conf` file did not apply to the default encryption types if the `default_tgs_enctypes` or `default_tkt_enctypes` attributes were not set. Consequently, Kerberos clients were able to request deprecated cipher suites like RC4, which may cause other processes to fail. With this update, encryption types specified in the `permitted_enctypes` variable apply to the default encryption types as well, and only permitted encryption types are requested. The RC4 cipher suite, which has been deprecated in RHEL 8, is the default encryption type for users, services, and trusts between Active Directory (AD) domains in an AD forest. * To ensure support for strong AES encryption types between AD domains in an AD forest, see the link:https://support.microsoft.com/en-us/help/4492348/kerberos-unsupported-etype-error-when-authenticating-across-trust[AD DS: Security: Kerberos "Unsupported etype" error when accessing a resource in a trusted domain] Microsoft article. * To enable support for the deprecated RC4 encryption type on a Domain Member for backwards compatibility with AD, use the `update-crypto-policies --set DEFAULT:AD-SUPPORT` command.
Clone Of:
Environment:
Last Closed: 2021-07-14 08:44:37 UTC
Type: Bug
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)

Description Andreas Schneider 2020-06-26 14:10:29 UTC 
Description of problem:

When installing Samba (samba-common) we should update the crypto-policy to enable AD-SUPPORT (RC4)
Comment 3 Andreas Schneider 2020-07-27 09:19:27 UTC 
`krb5` now only requests permitted encryption types

Previously, permitted encryption types specified in the `permitted_enctypes` variable in the `/etc/krb5.conf` file did not apply to the default encryption types if the `default_tgs_enctypes` or `default_tkt_enctypes` attributes were not set. Consequently, Kerberos clients were able to request deprecated cipher suites like RC4, which may cause other processes to fail. With this update, encryption types specified in the `permitted_enctypes` variable apply to the default encryption types as well, and only permitted encryption types are requested.

The RC4 cipher suite, which has been deprecated in RHEL 8, is the default encryption type for users, services, and trusts between Active Directory (AD) domains in an AD forest.
* To ensure support for strong AES encryption types between AD domains in an AD forest, see the link:https://support.microsoft.com/en-us/help/4492348/kerberos-unsupported-etype-error-when-authenticating-across-trust[AD DS: Security: Kerberos "Unsupported etype" error when accessing a resource in a trusted domain] Microsoft article.
* To enable support for the deprecated RC4 encryption type in an IdM server for backwards compatibility with AD, use the `update-crypto-policies --set DEFAULT:AD-SUPPORT` command.
Comment 4 Andreas Schneider 2020-07-27 09:30:22 UTC 
Update:

`krb5` now only requests permitted encryption types

Previously, permitted encryption types specified in the `permitted_enctypes` variable in the `/etc/krb5.conf` file did not apply to the default encryption types if the `default_tgs_enctypes` or `default_tkt_enctypes` attributes were not set. Consequently, Kerberos clients were able to request deprecated cipher suites like RC4, which may cause other processes to fail. With this update, encryption types specified in the `permitted_enctypes` variable apply to the default encryption types as well, and only permitted encryption types are requested.

The RC4 cipher suite, which has been deprecated in RHEL 8, is the default encryption type for users, services, and trusts between Active Directory (AD) domains in an AD forest.
* To ensure support for strong AES encryption types between AD domains in an AD forest, see the link:https://support.microsoft.com/en-us/help/4492348/kerberos-unsupported-etype-error-when-authenticating-across-trust[AD DS: Security: Kerberos "Unsupported etype" error when accessing a resource in a trusted domain] Microsoft article.
* To enable support for the deprecated RC4 encryption type on a domain member for backwards compatibility with AD, use the `update-crypto-policies --set DEFAULT:AD-SUPPORT` command.
Comment 9 Andreas Schneider 2021-06-17 13:42:11 UTC 
Marc, this information needs to be added to the RHEL 8 documentation and should also be mentioned in the release notes!
Comment 12 Marc Muehlfeld 2021-06-28 08:39:18 UTC 
Andreas, I think this is already covered:

Step 1 of "Joining a RHEL system to an AD domain" mentions what do do if AD requires RC4:
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html-single/deploying_different_types_of_servers/index#proc_joining-samba-to-a-domain_assembly_setting-up-samba-as-an-ad-domain-member-server

If RC4 is not required, then users will skip this step.

Additionally, for those who currently need RC4, we link an "Additional resources" of the above section how to enable AES in AD using a GPO (it's also part of our docs).

Do we need anything else?
Comment 14 Andreas Schneider 2021-07-14 08:44:37 UTC 
Looks fine, thanks!
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