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https://issues.apache.org/jira/browse/SSHD-1141?focusedWorklogId=571440&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-571440
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ASF GitHub Bot logged work on SSHD-1141:
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Author: ASF GitHub Bot
Created on: 24/Mar/21 19:38
Start Date: 24/Mar/21 19:38
Worklog Time Spent: 10m
Work Description: tomaswolf opened a new pull request #186:
URL: https://github.com/apache/mina-sshd/pull/186
If the server had announced via server-sig-algs which signature
algorithms it supports, UserAuthPubKey tries the known algorithms
first. If authentication with such a known signature algorithm fails,
there is no point trying other algorithms.
Trying different signature algorithms may make sense only if the client
doesn't know which algorithms the server supports.
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Issue Time Tracking
-------------------
Worklog Id: (was: 571440)
Time Spent: 3h (was: 2h 50m)
> 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: 3h
> 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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