Tests contain requests with User-Agent Microsoft-CryptoAPI

Hello all,

eventually some web page tests contain requests with
User-Agent: Microsoft-CryptoAPI/6.1
Host: gm.symcd.com

even though the tests are run with user agent Chrome and the original webpage does not contain any links to the aforementioned host.

Example: https://www.webpagetest.org/result/170425_AH_NP7/1/details/#waterfall_view_step1
Request #2

Re-running the same tests usually results in a run without any of those requests.

This happens on www.webpagetest.org as well as on our local WPT installation.
I suspect Microsoft Windows Update agent to be the culprit.

These requests should not happen during a WPT test run.

Best regards,
Ingo Steinke

Those are OCSP validation checks for www.weltbild.de and are absolutely part of the test. The only reason they don’t show up all the time is that the validation check result will be cached for a while.

If you want to see it always show up, there is a checkbox on the advanced settings page to clear the OS certificate cache for every run. That will also cause OCSP checks for intermediate certificates though which are usually in the cache.

The performance fix to make them not happen is to enable OCSP Stapling on the web server: https://hpbn.co/transport-layer-security-tls/#ocsp-stapling

Thanks for the explanation!