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This is exactly the problem with OCSP. There's no way to tell if the remote server is down, or if a malicious actor sitting in your path is blocking it. So yo
by jfindley 9y ago
This is exactly the problem with OCSP. There's no way to tell if the remote server is down, or if a malicious actor sitting in your path is blocking it. So your browser can either a) make it super easy for all your OCSP-using sites to appear down, which will encourage users to use other, non-OCSP, sites, or b) silently fail, which makes the entire exercise pointless.
Stapling only partially mitigates this, as it doesn't currently work with intermediate certs, and at this point most sites have at least one intermediate cert.
- pas 9y agoCould you elaborate on why they don't work with intermediate certs?
- jfindley 9y agoRFC 6066 specifies that you can only have one certificate in an OCSP response - as with intermediate certs you need to be able to respond with a chain, this does not work. RFC 6961 defines a multiple response capability, but my understanding is that currently this is not sufficiently widely implemented to be useful yet.
- pas 9y agoThanks! I thought it's enough if the stapled response contains information only about the intermediate cert, and the browser would accept that as good enough, if the chain it got in the handshake is valid. https://bugzilla.mozilla.org/show_bug.cgi?id=611836 https://bugzilla.mozilla.org/show_bug.cgi?id=611836 - this looks pretty abandoned (last comment 3 years ago) :/ and I found no bug for Chrome.
- skrubly 9y agoChrome, as far as I know, does not do OCSP - https://www.imperialviolet.org/2012/02/05/crlsets.html https://www.imperialviolet.org/2012/02/05/crlsets.html