Hi Patrice, thanks for your reply. Unfortunately, your explanation does not 
fit the facts which I've supplied. Let me try to convince you by restating 
in more detail two parts of my investigation:

1. Ignoring openssl for a moment, it is a FACT that if I open up the latest 
version of Chrome on my laptop here in our office, and type in the URL 
https://dashboard.geospock.com, the page doesn't load, and displays the 
following error:

SSL connection error
ERR_SSL_PROTOCOL_ERROR
Unable to make a secure connection to the server. This may be a problem 
with the server, or it may be requiring a client authentication certificate 
that you don't have.

It's doing this right now, as I type this. If I repeat the test on my home 
broadband connection, it loads and works just fine. The latest version of 
Chrome quite clearly supports all the latest TLS versions (right?), so you 
can't explain that away by claiming that I need to upgrade to a client the 
supports more than SSLv3. That's what I'm doing!

2. Looking at the openssl results, I also observed the debug info mentions 
SSLv3, and found that very odd. I experimented with using the openssl 
switches to disallow SSLv3 connections, and it had no effect on the 
behaviour. I also noted that in cases where it works (on the same computer, 
with the exact same command line), openssl indicates that it has 
established a TLSv1 connection, not SSLv3. So my conclusion is that the 
SSLv3 info in the crash is there because the SSL negotiation is somehow 
being corrupted, causing openssl to attempt to fallback to SSLv3, and then 
crashing it. For the record, the version of openssl on my computer is OpenSSL 
0.9.8zg 14 July 2015.

So the bottom line here, unless you're prepared to investigate further, is 
that serving App Engine apps on a custom Google Apps domain using a custom 
certificate via SNI is unusable (because it might fail randomly at any time 
in any geographical location). I suppose we could try using a virtual IP 
address instead, but that absolutely shouldn't be necessary. For our 
business-critical apps, we've now rerouted our traffic via our own SSL 
proxy to achieve exactly what Google Apps is supposed to be doing (our 
proxy is using SNI), and that's working just fine, while the Google 
infrastructure continues to fail. I find this unacceptable. Is there really 
nothing more you can do?

On Wednesday, 26 August 2015 15:11:32 UTC+1, Patrice (Cloud Platform 
Support) wrote:
>
> Hi Jon,
>
> Sorry for the delay, there was a lot of movement and investigation to get 
> to the bottom of this. What seems to be the issue is that older clients 
> that support sslv3 but not tls appeared to get errors. 
>
> Running $ openssl s_client -ssl3 -connect <fqdn>:443 -servername <fqdn> 
> would always fail with a handhshake error. As soon as we drop "-ssl3, 
> everything goes ok. Looking into the "illegal parameter" you get, we cannot 
> reproduce, and we have to pin it down to the version of software that 
> you're running. Looking online, every report of open ssl throwing "illegal 
> parameter" seemed to have to do with the version of openSSL or a 
> client-side config.
>
> I then went to check with the back-end team to see what was happening 
> there. Turns out it is indeed working as intended. SNI does not support 
> SSLv3. To get such a certificate up and running, I would suggest moving to 
> a Virtual IP <https://cloud.google.com/appengine/docs/ssl#virtual_ip_vip>, 
> which can help your situation.
>
> I hope that this will provide enough to shed some light on this.
>
> Cheers
>
>
>
>
> On Monday, August 24, 2015 at 11:09:22 AM UTC-4, Jon Travers wrote:
>>
>> Yes certainly. For the two locations where we've seen problems: our 
>> office broadband is using IP address 94.10.92.68, and our London VPS is 
>> on 46.101.45.203.
>>
>> Hope that helps
>> Jon
>>
>> On Monday, 24 August 2015 15:57:47 UTC+1, Patrice (Cloud Platform 
>> Support) wrote:
>>>
>>> Hi Jon,
>>>
>>> Thank you for all that extra information, this definitely will help in 
>>> finding out what issue you're having.
>>>
>>> Do you have on hand the IPs of the different locations/VPSes? I'm trying 
>>> to investigate, but having the exact IP that threw up the request would 
>>> definitely be helpful.
>>>
>>> Cheers
>>>
>>

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