[jira] [Resolved] (SSHD-1331) SSH Algorithm negotiation

["Pavel Pohner (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SSHD-1331?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Pavel Pohner resolved SSHD-1331.
--------------------------------
    Resolution: Information Provided

Thanks a lot, [~twolf], I suppose that makes more sense. I'll try reordering the signature algorithms then.

> SSH Algorithm negotiation 
> --------------------------
>
>                 Key: SSHD-1331
>                 URL: https://issues.apache.org/jira/browse/SSHD-1331
>             Project: MINA SSHD
>          Issue Type: Question
>    Affects Versions: 2.9.2
>            Reporter: Pavel Pohner
>            Priority: Major
>
> Hello,
> I'm facing a weird issue with SSH signature algorithm negotiation:
> Signature algorithms for RSA are sorted like this in my implementation:
>  
> {code:java}
> List<BuiltinSignatures> RSA_SIGNATURES = List.of(
>       BuiltinSignatures.rsa,
>       BuiltinSignatures.rsaSHA512_cert,
>       BuiltinSignatures.rsaSHA256_cert,
>       BuiltinSignatures.rsaSHA512,
>       BuiltinSignatures.rsaSHA256 {code}
> when establishing connection with server that offers following lists of algorithms, the connection is established without any issue:
> {code:java}
> ssh-rsa
> rsa-sha2-512
> rsa-sha2-256 {code}
> but, when server with list of algorithms in following order is encountered:
> {code:java}
> rsa-sha2-512
> rsa-sha2-256
> ssh-rsa {code}
> the connection fails with following exception:  *KeyExchange signature verification failed for key type=ssh-rsa*
> Based on SSH RFC my current understanding is, that in the second scenario, algorithm guessing happens, where my implementation (client), guesses the *ssh-rsa* algorithm, meanwhile the server guesses the {*}rsa-sha2-512{*}, in that case the guess is not successful and there's defined algorithm that must be followed (basically, client iterating over the common list of algorithms until finding the correct match) - [https://datatracker.ietf.org/doc/html/rfc4253#section-7.1]
> This seems to not be the case though as the exception says that the signature verification failed for *ssh-rsa,* I would expect the implementation to iterate to the *rsa-sha2-512* and match the server's guessed algorithm.
> How is this handled in Mina SSHD implementation? Is this something I can override/handle in my own implementation? Can someone point me in the right direction please?
>  



--
This message was sent by Atlassian Jira
(v8.20.10#820010)

---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@mina.apache.org
For additional commands, e-mail: dev-help@mina.apache.org