Bug 1575491

Summary:	ssh none cipher is used
Product:	Red Hat Enterprise Linux 7	Reporter:	Sham Antony <santony>
Component:	openssh	Assignee:	Jakub Jelen <jjelen>
Status:	CLOSED WONTFIX	QA Contact:	BaseOS QE Security Team <qe-baseos-security>
Severity:	low	Docs Contact:
Priority:	low
Version:	7.4	CC:	billycychan, cww, mgrepl, pasik
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Linux
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Fixed In Version:		Doc Type:	If docs needed, set a value
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Last Closed:	2019-02-11 15:39:55 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	1594286

Description Sham Antony 2018-05-07 05:58:14 UTC

Description of problem:

ssh allows 'none' cipher, same is not specified neither in ssh_config nor sshd_config

# ssh -c none user@server-ip


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

openssh-7.4p1-11.el7.x86_64

How reproducible:

# ssh -c none user@server-ip

Steps to Reproduce:

# ssh -c none user@server-ip

Actual results:

Initiating connection, using any other supported Ciphers after negotiation between client and server 

Expected results:

Unknown cipher type 'none'

Comment 2 Jakub Jelen 2018-05-07 07:51:35 UTC

Hello,
this is a problem of SSH1 and SSH2 protocol mixture, since both of them can be configured using the -c switch in ssh, but as already said in the case, the none method will NEVER be used for SSH2 protocol. Setting this value will fall back to the default ciphers list.

This is very minor issue, since it can be encountered only while listing the cipher on command line, while it will be rejected if it would be configured in the configuration files using Ciphers option:

  # ssh -oCiphers=none localhost
  command-line line 0: Bad SSH2 cipher spec 'none'.

Comment 3 Jakub Jelen 2018-05-07 07:53:29 UTC

Anyway, if we update OpenSSH, the fix should be trivial, emitting the similar error message in case this cipher is attempted.

Comment 4 Simo Sorce 2019-02-11 15:39:55 UTC

This issue was not selected to be included either in Red Hat Enterprise Linux 7.7 because it is seen either as low or moderate impact to a small amount of use-cases. The next release will be in Maintenance Support 1 Phase, which means that qualified Critical and Important Security errata advisories (RHSAs) and Urgent Priority Bug Fix errata advisories (RHBAs) may be released as they become available. We will now close this issue, but if you believe that it qualifies for the Maintenance Support 1 Phase, please re-open; otherwise we recommend moving the request to Red Hat Enterprise Linux 8 if applicable.