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Server CPU 100% when connecting from Chrome Browser

Posted: 05/25/2013 15:09:41
by Erich Kuba (Standard support level)
Joined: 05/16/2013
Posts: 42

Hi there,

Firstly, let me say that I am very impressed with your component set.

It took a while to get my head around it, but it is clearly very powerful once you understand things. Also, thanks for all the support so far. It's helped me a lot.

That said, I do have a serious problem:

Server Environment:
Linux 64bit. Debian 6.
SSB / Synapse / Freepascal / Lazarus
fSSLServer.Versions := [sbSSL2, sbSSL3, sbTLS1,sbTLS11, sbTLS12];
fSSLServer.RenegotiationAttackPreventionMode := rapmStrict;

Client Environment:
Google Chrome (Version 27.0.1453.93) on Linux 64bit, Apple Mac 10.8 & Windows

Fault Experienced:
The browser connects to the server and negotiates TLS 1.1 or TLS 1.0 (Dependant on the browser's capabilities). After that, the document is served to the browser and everything looks fine on the browser side. The problem is that about 3-5 seconds after the page has been served to the client (with browser sockets still open), the server software consumes 100% of a CPU Core for each connection from the browser. The server software responds to additional requests from the client if I do a refresh, which is slightly odd. I have used Wireshark to analyse the traffic and can verify that the browser is not sending any additional data that may be causing this fault. i.e. After the server has sent the document to the client, no further data changes hands in order to trigger this event. The server continues to consume 100% of a core after the browser has been closed and the sockets (and hence the TElSecureServer) have been destroyed.

Disabling the SSL engine (i.e. Unencrypted connection) removes the fault. I have spent a considerable amount of time placing entries which write to debug logs throughout my code and I am of the view that the fault must be somewhere within the SSB code.

I have tested this with the following browsers and they do not cause the fault and work as expected:
On Apple Mac: Firefox (Version 21.0), Opera (Version 12.15) & Safari (Version 6.0.4)
On Linux (64bit): Firefox (Version 21.0), Iceweasel (Version 3.5.16) & Opera (Version 11.60).
On Windows XP: Internet Explorer (Version 8.0.6001), Firefox (Version 21.0)

I have tested this with the following browsers and they do cause the fault:
On Apple Mac: Chrome (Version 27.0.1453.93)
On Linux (64bit): Chrome (Version 27.0.1453.93), Chromium (Version 6.0.472.63)
On Windows XP: Chrome (Version 27.0.1453.94 m)

Note: The fault only presents itself when a Google Chrome or Chromium browser connects from either Linux, Mac or Windows.

The fault is 100% reproducible and is obviously very concerning for obvious reasons.

Sorry ... can't do more modern Windows to test with as I don't use Windows and only have an old copy of XP on a VM.

Please advise.
Posted: 05/26/2013 00:55:09
by Eugene Mayevski (Team)

Thank you very much for such detailed report. I will move it to HelpDesk where our developers can work on it.

Sincerely yours
Eugene Mayevski



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