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From "Goldstein Lyor (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SSHD-642) Authentication failed: Signature length not correct: got 255 but was expecting 256
Date Thu, 11 Feb 2016 18:36:18 GMT

    [ https://issues.apache.org/jira/browse/SSHD-642?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15143219#comment-15143219

Goldstein Lyor commented on SSHD-642:

I am not sure how you suggest that MINA detect if zeroes are required or not. It would help
a lot if you could attach a code sample that uses Trilead and that *always* fails. Also, if
you have a solution in mind, feel free to fork the (latest) version from https://github.com/apache/mina-sshd,
and then submit a pull request with your recommended modification (just make sure that you
also add a unit test for it + that all the existing unit tests succeed un-modified...).

> Authentication failed: Signature length not correct: got 255 but was expecting 256
> ----------------------------------------------------------------------------------
>                 Key: SSHD-642
>                 URL: https://issues.apache.org/jira/browse/SSHD-642
>             Project: MINA SSHD
>          Issue Type: Bug
>    Affects Versions: 1.0.0
>            Reporter: Eugene Petrenko
> This issue I observe with quite low probability. It turns out that RSA signature verification
fails and thus SSH key authentication fails. (This is a bit strange that key verification
is executed BEFORE signature is checked). 
> In my cases it fails with Trilead SSH2 client. 
> From the code it fails inside JCE where it is asserted message size if not trimmed. (Exception
is not getting properly logged, but it is possible to find the message in sun/security/rsa/RSASignature.java
> In the sources of Trilead I see the code, that may trim leading zero byte from the signature.
Signature here is encoded with type and data, so that org.apache.sshd.common.signature.AbstractSignature#extractEncodedSignature
is executed and not-null is returned).
> https://github.com/JetBrains/intellij-community/blob/master/plugins/cvs/trilead-ssh2-build213/src/com/trilead/ssh2/signature/RSASHA1Verify.java#L98
> As you may see from the link this is the way they understand the standard. 
> I checked JSch code, and there is not such a byte trim there. 
> It may mean Mina SSHD should attempt to workaround it and add zero bites back

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