Red Hat Bugzilla – Bug 1360973
Support of HostKeyAlgorithms for sshd
Last modified: 2017-08-01 14:42:47 EDT
Description of problem: Under openssh 6.6 it it not possible to set the server host key algorithms. Version-Release number of selected component (if applicable): openssh-server-6.6.1p1-25.el7_2.x86_64 How reproducible: Every time Steps to Reproduce: 1. add HostKeyAlgorithms to the sshd config file 2. restart sshd Actual results: /etc/ssh/sshd_config: line 157: Bad configuration option: HostKeyAlgorithms Expected results: That this is known Additional info: The option was introduced with OpenSSH 7.0. See: http://www.openssh.com/txt/release-7.0
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This can be resolved by rebase to upstream openssh, or by backporting several patches: https://github.com/openssh/openssh-portable/commit/3a1638d (change) https://github.com/openssh/openssh-portable/commit/6310f60 (fixes) https://github.com/openssh/openssh-portable/commit/60a9247 (fixes) https://github.com/openssh/openssh-portable/commit/5bf0933 (test cases modifications) This change is also deprecating DSA keys from the server and client side, which we should not break, unless we have a good reason to and it is well documented (in either case).
This is expected behavior as described in upstream mailing list thread: http://lists.mindrot.org/pipermail/openssh-unix-dev/2017-April/035927.html In short, the extension is still a draft and there is no reasonable way to "overwrite" the standard ssh-rsa with this extension. At some point, we will certainly want to address this issue and do not use SHA1 altogether, but so far there is no way how to do that (mainly because the SHA2 hashes are extensions to the standard ssh-rsa).
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-2017:2029