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Bug 1774233 - Upgrading from 8.0 to 8.1 temporarily breaks sshd due to CASignatureAlgorithms
Summary: Upgrading from 8.0 to 8.1 temporarily breaks sshd due to CASignatureAlgorithms
Keywords:
Status: CLOSED DUPLICATE of bug 1772475
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: crypto-policies
Version: 8.1
Hardware: Unspecified
OS: Linux
medium
high
Target Milestone: rc
: 8.0
Assignee: Tomas Mraz
QA Contact: BaseOS QE Security Team
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2019-11-19 20:33 UTC by Ravindra Patil
Modified: 2023-09-07 21:02 UTC (History)
1 user (show)

Fixed In Version:
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Clone Of:
Environment:
Last Closed: 2019-11-20 08:15:17 UTC
Type: Bug
Target Upstream Version:
Embargoed:

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Description Ravindra Patil 2019-11-19 20:33:14 UTC 
Description of problem:

We've started upgrading our 8.0 test systems to 8.1, and have hit the same issue on all of them with sshd crashing out with the error

command-line: line 0: Bad configuration option: CASignatureAlgorithms

In most cases, that's left systems which are being upgraded without ability to ssh for ~20 minutes while the number of packages being updated in 8.1. 

While tried to ssh its reporting following error for 'casignaturealgorithms' option 

[root@rhel8 ~]# ssh rhel8
/etc/crypto-policies/back-ends/openssh.config: line 6: Bad configuration option: casignaturealgorithms
/etc/crypto-policies/back-ends/openssh.config: terminating, 1 bad configuration options

Service was running but was not able to perform ssh.

[root@rhel8 ~]# systemctl status sshd
● sshd.service - OpenSSH server daemon
   Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2019-11-20 01:53:46 IST; 1min 48s ago
     Docs: man:sshd(8)
           man:sshd_config(5)
 Main PID: 2909 (sshd)

This is critical issue, as users should be allowed to perform ssh while the upgrade is in progress. 

That keeps happening until both libssh and crypto-policies have been updated (libssh presumably removed a CASignatureAlgorithm that crypto-policies is specifying in /etc/crypto-policies/back-ends/opensshserver.config).

Version-Release number of selected component (if applicable):
20181217-6.git9a35207.el8.noarch

How reproducible:
Start upgrade from RHEL 8.0 to 8.1
# yum update -y

Then try doing ssh from the same system to any other machine
# ssh <server-ip>

Steps to Reproduce:
1. Login to RHEL 8.0 
2. Upgrade from RHEL 8.0 to 8.1
3. Try to perform ssh

Actual results:
sshd crashes with below output

/etc/crypto-policies/back-ends/openssh.config: line 6: Bad configuration option: casignaturealgorithms
/etc/crypto-policies/back-ends/openssh.config: terminating, 1 bad configuration options


Expected results:
SSHD should work fine. 

Additional info:
Service was running but failed due to bad configuration option error for ' CASignatureAlgorithms'

After sometime was able to ssh again when both packages libssh and crypto-policies were updated.
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