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Bug 1816253 - Weak GSSAPI key exchange methods enabled by default [crypto-policies]
Summary: Weak GSSAPI key exchange methods enabled by default [crypto-policies]
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: crypto-policies
Version: 8.4
Hardware: Unspecified
OS: Unspecified
medium
medium
Target Milestone: rc
: 8.0
Assignee: Tomas Mraz
QA Contact: Ondrej Moriš
URL:
Whiteboard:
Depends On: 1666781 1816226
Blocks:
TreeView+ depends on / blocked
 
Reported: 2020-03-23 16:35 UTC by Jakub Jelen
Modified: 2020-11-04 02:00 UTC (History)
8 users (show)

Fixed In Version: crypto-policies-20200527-1.git63fc906.el8
Doc Type: No Doc Update
Doc Text:
Clone Of: 1816226
Environment:
Last Closed: 2020-11-04 01:58:27 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 01:58:40 UTC

Description Jakub Jelen 2020-03-23 16:35:31 UTC 
The defaults in RHEL 8 are handled by crypto policies, which needs to be updated for this change to have some effect.

+++ This bug was initially created as a clone of Bug #1816226 +++

+++ This bug was initially created as a clone of Bug #1666781 +++

The build of OpenSSH in Fedora carries patches to enable GSSAPI key exchange.  Hurrah, when this is used, the need to manually verify host keys is removed.

The manual says that the default value for setting GSSAPIKexAlgorithms is “gss-gex-sha1-,gss-group14-sha1-”.  However, https://datatracker.ietf.org/doc/draft-ietf-curdle-ssh-kex-sha2/ says that gss-gex-sha1- is weak and "SHOULD NOT be used".  I suggest that it be disabled by default, and that some of the newer methods such as gss-curve25519-sha256-, gss-nistp256-sha256-, gss-group14-sha256-
be enabled by default instead.

--- Additional comment from Jakub Jelen on 2019-01-16 16:28:20 CET ---

Hello and thank you for your interest. This is indeed planned, but we are waiting for finalizing and approving the draft defining the new gssapi key exchange methods before enabling them to the world:

https://tools.ietf.org/html/draft-ietf-curdle-gss-keyex-sha2-08

Generally, the GEX methods are not advised these days and once we will have something better, we will certainly try to disable them.

Actually I am not quite sure if I saw your referenced draft before, but it looks like it is stalled, the current version expired and it does not look like moving forward to be accepted as a RDC any time soon. Actually it does not say anything new to me.

I will leave this bug open to keep track of things and make sure I will update the list when the drafts will get approved.

--- Additional comment from Jakub Jelen on 2020-03-23 15:27:14 CET ---

FYI, the RFC 8732 was published so I would like to enable these soon in Fedora.

[1] https://tools.ietf.org/html/rfc8732

--- Additional comment from Jakub Jelen on 2020-03-23 16:24:34 CET ---

First step is enabling them in Crypto policy. The issue was filled here as it does not look like completely straight-forward:

https://gitlab.com/redhat-crypto/fedora-crypto-policies/-/issues/19
Comment 8 errata-xmlrpc 2020-11-04 01:58:27 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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