[TYPO3-english] TYPO3 behind a CDN and checkValidBrowserOrDie() ("Your browser version looks incompatible with this TYPO3 version")

[Michael Schams]

Hi!

When accessing the BE, TYPO3 checks the browser used by the client [1]. 
The User-Agent string is used for this [2].

If the user-agent does not match a pattern of "known" browsers 
(currently: Konqueror, Opera, MSIE, Mozilla and Flash), 
$GLOBALS['CLIENT']['BROWSER'] is not set [3] and as a consequence an 
exception is thrown and the user can not login: "#1294587023: Browser 
Error: Your browser version looks incompatible with this TYPO3 version!" 
[4]

Some of our TYPO3 CMS sites are behind CDNs (content delivery network). 
 From a client's perspective, the CDN is the end-point and the CDN does 
not forward the user-agent string to the application server (here: the 
TYPO3 instance). In fact the CDN sends it's own string to identify that 
the request comes from the CDN, but not the user-agent from the client's 
browser.

As a workaround, I have used two domains in these cases: one for the 
frontend (which points to the CDN) and a second one for the backend 
(which points to the server directly and bypasses the CDN). This is not 
ideal and I wonder if someone has a similar setup or a better solution 
:-)


Cheers
Michael


[1] typo3/init.php, line 55:

00053:  ->checkBackendIpOrDie()
00054:  ->checkSslBackendAndRedirectIfNeeded()
00055:  ->checkValidBrowserOrDie()
00056:  ->loadExtensionTables(TRUE)
00057:  ->initializeSpriteManager()

[2] typo3/sysext/core/Classes/Utility/GeneralUtility.php -> method 
clientInfo()

[3] typo3/sysext/core/Classes/Core/Bootstrap.php -> method 
checkValidBrowserOrDie()

[4] https://wiki.typo3.org/Exception/CMS/1294587023