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Posted to dev@mina.apache.org by "Thomas Wolf (Jira)" <ji...@apache.org> on 2022/04/22 13:55:00 UTC
[jira] [Commented] (SSHD-1264) different host key algorithm used on rekey than used for the initial connection
[ https://issues.apache.org/jira/browse/SSHD-1264?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17526447#comment-17526447 ]
Thomas Wolf commented on SSHD-1264:
-----------------------------------
Hm. Can you show the client-side log, (log level DEBUG) please? I have an idea what might be going on, but without client-side log it's hard to tell.
> different host key algorithm used on rekey than used for the initial connection
> -------------------------------------------------------------------------------
>
> Key: SSHD-1264
> URL: https://issues.apache.org/jira/browse/SSHD-1264
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 2.8.0
> Reporter: James Nord
> Priority: Major
> Attachments: sshd_log.txt
>
>
> when using mina as an ssh client to connect to an open ssh server the host key algorithm that is negotiated on the initial connection can have a different algorithm than the one used in a rekey.
> This causes an issue as connections can be terminated if the initial host key type is in the known hosts, (say ecdsa) but the subsequent on (rsa) is not.
> once connected the same host key algorithm should be used in any subsequent re-key events.
> (see log attached from SSHD)
> Note: this is easyish to see by setting opensshd server config `RekeyLimit default 10` which will cause a rekey after 10 seconds on a data event.
> e.g.
> {noformat}
> debug1: kex: host key algorithm: ecdsa-sha2-nistp256 [preauth]
> debug1: kex: host key algorithm: rsa-sha2-512 {noformat}
> shows the flop from an agreed exchange of {{ecdsa-sha2-nistp256}} to {{rsa-sha2-512}}
> the end result is that if the rsa key is not known then the connection is killed
> {{o.a.s.c.k.KnownHostsServerKeyVerifier#acceptModifiedServerKey: acceptModifiedServerKey(ClientSessionImpl[jenkins@localhost/127.0.0.1:22]) mismatched keys presented by localhost/127.0.0.1:22 for entry=localhost ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBNZDNvKiE7VBVWziZUlICIpIEMhVy0nL3y2hHYRQGMOaWWPajP86ucgwgeXAWmJOxr4bqMtC9tF0vC1W2l8wYPM=: expected=ecdsa-sha2-nistp256-SHA256:x5TMcz4T6ggPxxSbx6gfTzk8US6CLuxgmqXNXedu+6w, actual=ssh-rsa-SHA256:W60YQsFuMkHf0flHrJFR31lvyYm7Y6BkEMkqHUTOpZQ}}
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