Bugzilla (bugzilla.redhat.com) will be under maintenance for infrastructure upgrades and will not be available on July 31st between 12:30 AM - 05:30 AM UTC. We appreciate your understanding and patience. You can follow status.redhat.com for details.
Bug 1575491 - ssh none cipher is used
Summary: ssh none cipher is used
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: openssh
Version: 7.4
Hardware: Unspecified
OS: Linux
Target Milestone: rc
: ---
Assignee: Jakub Jelen
QA Contact: BaseOS QE Security Team
Depends On:
Blocks: 1594286
TreeView+ depends on / blocked
Reported: 2018-05-07 05:58 UTC by Sham Antony
Modified: 2019-02-11 15:39 UTC (History)
4 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Last Closed: 2019-02-11 15:39:55 UTC
Target Upstream Version:

Attachments (Terms of Use)

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):


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
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.

Note You need to log in before you can comment on or make changes to this bug.