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https://issues.apache.org/jira/browse/SSHD-1141?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17317087#comment-17317087
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Thomas Wolf commented on SSHD-1141:
-----------------------------------
Client-side this appears to be fixed:
* Use all configured signature algorithms (SSHD-1105).
* If a server announces server-sig-algs, try the announced algorithms first.
(Changes done for this issue 1141.)
* If neither helps, the client would need to re-order signature algorithms,
placing ssh-rsa first. In openSSH (and in JGit) this can be done via ssh config
{{PubkeyAcceptedKeyTypes}} (or {{PubkeyAcceptedAlgorithms}} since openSSH 8.5).
Closing this now. [~iwienand], did you have more in mind?
> Implement server-sig-algs
> -------------------------
>
> Key: SSHD-1141
> URL: https://issues.apache.org/jira/browse/SSHD-1141
> Project: MINA SSHD
> Issue Type: Improvement
> Reporter: Ian Wienand
> Assignee: Thomas Wolf
> Priority: Major
> Time Spent: 4h 40m
> Remaining Estimate: 0h
>
> Mina sshd should implement server-sig-algs to report signature algorithms.
> Without the daemon sending server-sig-algs, clients fall back to ssh-rsa per
> RFC8332
> {quote}When authenticating with an RSA key against a server that does not
> implement the "server-sig-algs" extension, clients MAY default to an
> "ssh-rsa" signature to avoid authentication penalties.
> {quote}
> Some distributions, notably Fedora 33, have set default system policy to
> disallow insecure algorithms such as ssh-rsa. They thus can not find a
> suitable signature algorithm and fail to log in. Quite a high level of
> knowledge is required to override the default system cryptography policy, and
> it can be quite confusing because the user's ssh-key works in many other
> contexts (against openssh servers, etc.). For full details see discussion in
> SSHD-1118.
> For example, connecting to a recent openssh server I see something like
> {quote}debug1: kex_input_ext_info:
> server-sig-algs=<ssh-ed25519,[email protected],ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected]>
> {quote}
> I believe that Mina SSHD does support these more secure signature algorithms,
> but because they aren't reported the client won't use them.
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