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From "ASF GitHub Bot (Jira)" <j...@apache.org>
Subject [jira] [Work logged] (SSHD-968) SshClient times out during keep-alive, when SSH_MSG_GLOBAL_REQUEST is replied with SSH_MSG_UNSUPPORTED
Date Thu, 27 Feb 2020 08:16:00 GMT

     [ https://issues.apache.org/jira/browse/SSHD-968?focusedWorklogId=394022&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-394022
]

ASF GitHub Bot logged work on SSHD-968:
---------------------------------------

                Author: ASF GitHub Bot
            Created on: 27/Feb/20 08:15
            Start Date: 27/Feb/20 08:15
    Worklog Time Spent: 10m 
      Work Description: lgoldstein commented on issue #112: SSHD-968
URL: https://github.com/apache/mina-sshd/pull/112#issuecomment-591840036
 
 
   The suggested fix seems to involve too many methods changes - not mention the fact that
the extra argument is very specific to this issue. What if future fixes require more argument
? However, your fix has given me an idea I would like to explore that may provide (IMO) a
better solution. Be patient for 1-2 days and I might have something.
 
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Issue Time Tracking
-------------------

    Worklog Id:     (was: 394022)
    Time Spent: 20m  (was: 10m)

> SshClient times out during keep-alive, when SSH_MSG_GLOBAL_REQUEST is replied with SSH_MSG_UNSUPPORTED
> ------------------------------------------------------------------------------------------------------
>
>                 Key: SSHD-968
>                 URL: https://issues.apache.org/jira/browse/SSHD-968
>             Project: MINA SSHD
>          Issue Type: Improvement
>    Affects Versions: 2.3.0
>         Environment: Windows 10
>            Reporter: Patrik Ek
>            Assignee: Guillaume Nodet
>            Priority: Major
>          Time Spent: 20m
>  Remaining Estimate: 0h
>
> In case SSH_MSG_GLOBAL_REQUEST is not supported by the remote SSH server, the keep-alive
heartbeat times out. The reason for this is SSH_MSG_UNIMPLEMENTED is only logged in
> {color:#172b4d}org.apache.sshd.common.session.helpers{color}.AbstractSession
> The method identifying the SSH_MSG_UNIMPLEMENTED is called AbstractSession.doHandleMessage()
> The consequense is that no reply is received and the heartbeat times out instead of calling
AbstractSession.requestFailure(). Which in turn leads to the session terminates.
> According to RFC 4253 sect. 11.4 ({color:#004000}https://tools.ietf.org/html/rfc4253#section-11.4{color})
the SSH_MSG_UNIMPLEMENTED is meant to be ignored, but this makes little sense for a heartbeat,
as even SSH_MSG_UNIMPLEMENTED is good enough to count as a reply for this. This is for example
the case in OpenSSH, where SSH_MSG_UNIMPLEMENTED replies for heartbeat, does not lead to a
termination of the SSH session.
> There is a workaround released in 2.1.1, to use ReservedSessionMessagesHandler for handling
replies, but this does not allow access to the method AbstractSession.requestFailure() (without
using reflection so to say). Further, the heartbeat is ongoing in the background, so there
is no good solution to this problem from outside of the framework.
> https://issues.apache.org/jira/browse/SSHD-887?jql=project%20%3D%20SSHD%20AND%20fixVersion%20%3D%202.1.1
> Would this be possible to fix? The reason I write it here is because the bug seems to
existing up to some version of libssh, even for the SSHv2 protocol, so just writing a bug
report on the particular server will not solve the problems for already existing implementations
using libssh.
> The following config is used,
> SshClient client = SshClient.setUpDefaultClient(){color:#cc7832};{color}{color:#808080}
> {color} {color:#172b4d}PropertyResolverUtils.updateProperty(client, ClientFactoryManager.HEARTBEAT_INTERVAL,
15000);
>  PropertyResolverUtils.updateProperty(client,ClientFactoryManager.HEARTBEAT_REPLY_WAIT,
30000);
>  PropertyResolverUtils.updateProperty(client,ClientFactoryManager.HEARTBEAT_REQUEST,
"keepalive@openssh.com");{color}
> {color:#cc7832}{color:#172b4d}BR{color}
> {color:#172b4d}Patrik{color}
> {color}



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