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https://issues.apache.org/jira/browse/SSHD-828?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16516924#comment-16516924
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Gavin Camp commented on SSHD-828:
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The best fix would be to notify the socks/proxy implementation that the channel
is active before actually allowing any packets to flow over it, thus allowing
the socks/proxy implementation to send the final socks packet before any
packets from the channel.
That is, ensure that any listeners add to the channel e.g.
channel.open().addListener(this::onChannelOpened);
are always called before allowing any packets to flow over the channel.
> Race condition when using SOCKS connections
> -------------------------------------------
>
> Key: SSHD-828
> URL: https://issues.apache.org/jira/browse/SSHD-828
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 1.7.0
> Reporter: Gavin Camp
> Priority: Major
> Attachments: patch.diff
>
>
> There is a race condition when using SOCKS proxies with the SSHD server.
> After the initial SOCKS negotiation the SOCKS proxy creates a channel. When
> notified that the SOCKS channel is open the SOCKS proxy then sends the final
> accept SOCK packet. However there is a timing issue where very fast hosts
> could have already sent a packet over the now open channel - which will
> arrive at the client before the final SOCKS proxy packet. This confuses the
> SOCKS client connected to the server as its expected a SOCKS packet and
> instead gets a packet from the underlying stream.
> While this isn't a huge issue for us, given that we have the patch, this
> could render the SOCKS implementation useless for some users.
> Attached is a rough patch the corrects the issue.
> Note: as we are just using SSHD for testing I wasn't overly concerned with
> error checking or avoiding synchronization - I'm just providing it to help
> illustrate the issue. Also you can ignore the pom and check-style changes I
> just disabled them for an easier life.
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