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https://issues.apache.org/jira/browse/SSHD-1141?focusedWorklogId=569246&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-569246
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ASF GitHub Bot logged work on SSHD-1141:
----------------------------------------
Author: ASF GitHub Bot
Created on: 20/Mar/21 12:09
Start Date: 20/Mar/21 12:09
Worklog Time Spent: 10m
Work Description: tomaswolf opened a new pull request #184:
URL: https://github.com/apache/mina-sshd/pull/184
Unconditionally announce that the client wants to get the server's
SSH_MSG_EXT_INFO. Otherwise the server will never send it. Add the
"ext-info-c" marker only on the very first key exchange proposal,
and make sure the client doesn't send by mistake "ext-info-s".
KexExtensions are available in all phases except PREKEX.
When server-sig-algs is received, reorder the client session's
signature factories such that algorithms the server announced as
supported come first, followed by those not announced, both in client
order.
The client determines the order and the server just says what it
supports.
Note that per RFC 8308 [1] it's possible that a server doesn't announce
_all_ the algorithms it supports, and a client is allowed to try
unsupported algorithms, but may face authentication penalties such
as back-off delays, authentication failures, or disconnections.
[1] https://tools.ietf.org/html/rfc8308
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Issue Time Tracking
-------------------
Worklog Id: (was: 569246)
Remaining Estimate: 0h
Time Spent: 10m
> 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
> Priority: Major
> Time Spent: 10m
> 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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