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Bug 1851458 - add AD-SUPPORT policy module to allow IPA and Samba to enable RC4 cipher
Summary: add AD-SUPPORT policy module to allow IPA and Samba to enable RC4 cipher
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: crypto-policies
Version: 8.3
Hardware: Unspecified
OS: Unspecified
high
high
Target Milestone: rc
: 8.0
Assignee: Tomas Mraz
QA Contact: Ondrej Moriš
URL:
Whiteboard:
Depends On:
Blocks: 1851139 1851442
TreeView+ depends on / blocked
 
Reported: 2020-06-26 15:01 UTC by Alexander Bokovoy
Modified: 2020-11-04 02:01 UTC (History)
4 users (show)

Fixed In Version: crypto-policies-20200629-1.git806b5d3.el8
Doc Type: No Doc Update
Doc Text:
Clone Of:
Environment:
Last Closed: 2020-11-04 01:58:45 UTC
Type: Bug
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2020:4536 0 None None None 2020-11-04 01:59:01 UTC

Description Alexander Bokovoy 2020-06-26 15:01:22 UTC 
Upstream merge request: https://gitlab.com/redhat-crypto/fedora-crypto-policies/-/merge_requests/70

Add AD-SUPPORT policy module that can be used by administrators to add RC4
ciphers back to the supported list with

   update-crypto-policies --set DEFAULT:AD-SUPPORT

There is no need to enable AD-SUPPORT by default but FreeIPA and Samba will
benefit from the presence of this policy module and handle enablement
automatically in case it is needed.

RC4 cipher is widely used in Active Directory environment.
For all AD environments since Windows Server 2008:

 - default encryption type for users and services is still RC4 despite allowing to enable AES encryption.

 - changing forest- or domain-wide policy to enable AES encryption types does not change existing user and services' Kerberos keys. They still have only RC4 unless they changed user password or machine account password.

 - when trust is established between AD domains in the same forest, default encryption type for trusted domain object (krbtgt/...) is RC4 only, unless there is a forest- or domain-wide policy to enable AES encryption type is in action.

 - removing RC4 from the policy in AD leads to situation that no Kerberos ticket can be issued at all.
Comment 2 Ondrej Moriš 2020-06-29 09:19:25 UTC 
Alexander, can your team help us to check that everything works as expected once the fix is available? Having a sign-off from you in this BZ would definitely help.
Comment 3 Alexander Bokovoy 2020-06-29 10:11:32 UTC 
Yes, we'll do the verification from IdM QA.
Comment 7 Ondrej Moriš 2020-07-13 07:45:54 UTC 
Verified SanityOnly.

NEW (crypto-policies-20200629-1.git806b5d3.el8)
===============================================
# update-crypto-policies --show
DEFAULT

# cat /etc/crypto-policies/back-ends/krb5.config 
[libdefaults]
permitted_enctypes = aes256-cts-hmac-sha1-96 aes256-cts-hmac-sha384-192 camellia256-cts-cmac aes128-cts-hmac-sha1-96 aes128-cts-hmac-sha256-128 camellia128-cts-cmac

# update-crypto-policies --set DEFAULT:AD-SUPPORT
Setting system policy to DEFAULT:AD-SUPPORT
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.

# cat /etc/crypto-policies/back-ends/krb5.config 
[libdefaults]
permitted_enctypes = aes256-cts-hmac-sha1-96 aes256-cts-hmac-sha384-192 camellia256-cts-cmac aes128-cts-hmac-sha1-96 aes128-cts-hmac-sha256-128 camellia128-cts-cmac arcfour-hmac-md5
Comment 10 errata-xmlrpc 2020-11-04 01:58:45 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (crypto-policies bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2020:4536
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