Why are cookies unrecognized when a link is clicked from an external source (i.e. Excel, Word, etc...)
I noticed that when a link is clicked externally from the web browser, such as from Excel or Word, that my session cookie is initially unrecognized, even if the link opens up in a new tab of the same browser window.
The browser ends up recognizing its cookie eventually, but I am puzzled as to why that initial link from Excel or Word doesn't work. To make it even more challenging, clicking a link works fine from Outlook.
Does anybody know why this might be happening? I'm using the Zend Framework with PHP 5.3.
Answer
This is because MS Office is using Hlink.dll component to lookup if the link is Office document or something else. MS Office expect to open the document linked within documents without the aid of external browser (using Hlink.dll component of IE6).
If session cookie protects website Hlink naturally is being redirected to login page and having reached HTML page and not able to "understand" it opens it in external browser. Note that it opens not original URL (expected behavior) but the result of redirect, even if it was 302 redirect.
Microsoft has that bug in unsupported component (Hlink.dll), instead of recognizing the bug they turn it over to our head (trying to convince us that it is flaw of SSO system we use, i.e. session cookies) and refuses to upgrade it. It offers workaround that turns off the lookup functionality of MS Office:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Office\9.0\Common\Internet\ForceShellExecute:DWORD=1
Or offer us to workaround serverside, to avoid HTTP redirects and change into Javascript redirects or META REFRESH redirects (i.e. to have Hlink get text/html page on original URL and make it run external browser to handle it).