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Posted to dev@mina.apache.org by "Michael Heemskerk (JIRA)" <ji...@apache.org> on 2013/09/06 13:42:51 UTC
[jira] [Commented] (SSHD-256) SSH_MSG_CHANNEL_REQUEST for Putty
handled incorrectly
[ https://issues.apache.org/jira/browse/SSHD-256?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13760151#comment-13760151 ]
Michael Heemskerk commented on SSHD-256:
----------------------------------------
See the linked pull request for the patch
> SSH_MSG_CHANNEL_REQUEST for Putty handled incorrectly
> -----------------------------------------------------
>
> Key: SSHD-256
> URL: https://issues.apache.org/jira/browse/SSHD-256
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 0.7.0, 0.8.0, 0.9.0
> Reporter: Michael Heemskerk
>
> Symptom:
> SSH connection is kept open after the command completes when using Putty, Plink or TortoisePlink, or rather Putty does not finish.
> See:
> * https://code.google.com/p/tortoisegit/issues/detail?id=1880
> * https://jira.atlassian.com/browse/STASH-3824
> Cause:
> ChannelSession has special handling for SSH_MSG_CHANNEL_REQUEST messages that are sent by Putty:
> if (type != null && type.endsWith("@putty.projects.tartarus.org")) {
> // Ignore but accept, more doc at
> // http://tartarus.org/~simon/putty-snapshots/htmldoc/AppendixF.html
> return true;
> }
> There are really two problems with this workaround that was introduced in SSHD-77:
> 1) This code ignores the "want reply" flag on the field and simply ignores the request. According to the SSH protocol specification, the server MUST send back a reply (success or failure) if the "want reply" flag is set to true.
> 2) Putty _intentionally_ sends an invalid request and _expects_ to receive a SSH_MSG_CHANNEL_FAILURE response (see http://tartarus.org/~simon/putty-snapshots/htmldoc/AppendixF.html), which is the default behaviour of ChannelSession.
> I don't know whether changes in Putty or changes in MinaSSHD have made the workaround obsolete, but it is obsolete. I've verified that without the bit of code I quoted above, the Putty terminates normally.
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