Revert VNC disconnection workaround when Guacamole Docker image is updated

[dav3r]

In #1, we added a workaround to avoid frequent VNC disconnections by disabling 'TLSVnc' authentication.

We believe that Guacamole fixed the underlying issue in PR #217. Although that fix was merged into the master branch on April 24, 2019, the latest Guacamole Docker image (which we are using) was built from the Guacamole 1.0 release from Jan. 8, 2019, which predates PR #217.

The purpose of this issue is to ensure that at some point in the future, we should obtain a Guacamole Docker image (or build our own) that includes PR #217. Once that happens, we should roll back the changes that were made in #1, since they should no longer be necessary.

[CloudSurgeon]

Thanks, ladies and gents. I am leveraging your workaround. I was also facing GUAC-414, so I built and compiled everything from source to see if the PR suggested for the issue actually resolved the problem. Unfortunately, the problem seems to persist (Ubuntu Bionic). I would be curious to see if you have attempted and experienced the same?

[dav3r]

@CloudSurgeon That is disappointing to hear that you are still seeing the same issue after building from source. We have not yet built an up-to-date Docker image from source, but when we do, I will be sure to post an update here about our results.

[CloudSurgeon]

I spoke to the Guac devas and I need to go back and double check the version of libvnc I compiled against. It is suspected I compiled against an older version. I'll try and take the time to run through again and will let you know.

…

On Tue, Sep 3, 2019 at 4:11 PM dav3r ***@***.***> wrote: @CloudSurgeon <https://github.com/CloudSurgeon> That is disappointing to hear that you are still seeing the same issue after building from source. We have not yet built an up-to-date Docker image from source, but when we do, I will be sure to post an update here about our results. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#2?email_source=notifications&email_token=AC7RDSSMLCHNLTUFBV6BOG3QH3AFZA5CNFSM4IN2Y5DKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD5ZNOGI#issuecomment-527619865>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AC7RDSRK3MJQFMWD4LTPJDLQH3AFZANCNFSM4IN2Y5DA> .

[dav3r]

FYI, we are currently testing the latest 1.1.0 Guacamole images (guacamole and guacd)
and we are still seeing sporadic VNC disconnections by Guacamole (as described in #1) when we do not start the VNC server with -SecurityType VncAuth (to disable the TLSVnc authentication).

In the Guacamole PR with the potential fix for this issue, they state:

Note that support for these callbacks was released in LibVNCServer/Client 0.9.11, so it will only work against 0.9.11 or later- the bug documented in GUACAMOLE-414 will still be present when using libvncserver/client prior to 0.9.11.

We should be fine on that front- our VNC server host is running with libvncserver version 0.9.12:

# dpkg -l | grep libvncserver
ii  libvncserver1:amd64                  0.9.12+dfsg-8                        amd64        API to write one's own VNC server

Note that the error message in the VNC server is slightly different now:

VNCSConnST:  closing 10.224.1.13::60288: readTLS: Decryption has failed. (-24)
...
TLS:         TLS session wasn't terminated gracefully

Here is what it looks like in the guacd Docker container log:

guacd | guacd[567]: ERROR:	Error handling message from VNC server.
guacd | guacd[567]: INFO:	Internal VNC client disconnected

I see two possibilities:

• Fairly unlikely: The Guacamole fix that was made back in April 2019 has not made its way into the Docker image created on Jan. 29, 2020.
• More likely: There is an additional issue going on here that we are not aware of.

For now, we will continue to run without using TLSVnc authentication.