Learning from my mistakes about TLS, certificates and browsers

Well, I guess that, for those who read my previous post about SSL/TLS error messages on Mac OS X browsers, it’s abundantly clear that I don’t really know SSL/ TLS and the way browsers handle the certificates. But hey, I blog to learn from my mistakes and Philip and Peter helped me understand a bit about TLS with their useful comments.

The summary for TLS-dummies like me:

  • According to the TLS spec the server should not only provide it’s own certificate, but also any intermediate certificate between it’s own & the CA’s root
  • Browsers (or the OS’es key stores that some browsers depend upon) don’t ship with any intermediate certificate, but can and in some cases will store (cache) them when they come across them. In Firefox, cached intermediate certificates are listed as being part of the “software security device”, whereas root certificates are in the “builtin object token”.

All in all, this means that whenever you’re implementing TLS (or SSL, if you’re old-fashioned) you have  to configure your webserver to provide all intermediate certificates in a “chainfile” as (for example) per Apache’s SSLCertificateChainFile directive.

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