Bug 1685096

Summary:	In FIPS mode, during DH group exchange, OpenSSH client should validate the received moduli, making sure it is one of the known groups.
Product:	Red Hat Enterprise Linux 8	Reporter:	Jakub Jelen <jjelen>
Component:	openssh	Assignee:	Jakub Jelen <jjelen>
Status:	CLOSED ERRATA	QA Contact:	Ondrej Moriš <omoris>
Severity:	unspecified	Docs Contact:
Priority:	high
Version:	8.1	CC:	asosedki, omoris, rrelyea, szidek, tmraz
Target Milestone:	rc	Keywords:	Triaged
Target Release:	8.1
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	openssh-8.0p1-1.el8	Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2019-11-05 22:41:32 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1682500
Bug Blocks:	1701002

Description Jakub Jelen 2019-03-04 10:55:17 UTC

Description of problem:
In FIPS mode, during DH group exchange, OpenSSH client should validate the received moduli, making sure it is one of the known groups.

Version-Release number of selected component (if applicable):
openssh-7.8p1

How reproducible:
100%

Steps to Reproduce:
1. Connect to the server using dh group exchange kex mechanism

Actual results:
The client will use one of the non-approved moduli sent by server

Expected results:
The client should make sure it is one of the known groups that are offered when the moduli file is missing

Additional info:
At this moment, OpenSSH server is sending either group14, group16 or group18, depending on the negotiated parameters, when the moduli file is not available.

Comment 1 Jakub Jelen 2019-03-04 11:43:01 UTC

Additionally, we should modify the server in the FIPS mode to ignore the /etc/moduli and use only the hardcoded modulis. It is less fragile than having the file removed or renamed in the crypto-policies FIPS setup.

Comment 2 Tomas Mraz 2019-03-04 13:04:59 UTC

The alternative is to disable the dh-group-exchange in the FIPS policy completely. We would lose the compatibility with RHEL-6 this way, on the other hand the compatibility is limited anyway as the RHEL-6 has to have the /etc/moduli file removed to send group14 and not some random prime from the moduli file.

Comment 30 errata-xmlrpc 2019-11-05 22:41:32 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, 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/RHSA-2019:3702