Tag Archives: Chrome

What are some upsides of googles’s SHA1 deprecation plan?

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NOTE: Google has since adopted a more gradual plan for migration which will addresses the potential false sense of urgency the prior plan represented. Personally I think the new plan is a good one. The upsides in this post are still accurate and it is my hope people switch to SHA256 based certificates as quickly as possible.

The Internet is about to embark on another Heartbleed-esq certificate migration. This time there is no immediate danger (which was certainly not the case with Heartbleed) and there is a proposed twelve weeks to plan and respond.

During this time (unless that plan changes) a large majority of the SSL secured Internet will need to swap out their SSL certificates or the users of these sites will see a little scarier user experience. To be fair some of these certificates will be expiring regardless and need to be replaced anyway but this still represents a large number of additional sites that will need to replace certificates sooner than they had planned.

That said there are upsides, for example given how many of the top sites now use SSL the users of these sites will need to move to modern browsers not dependent on platform crypto or update to a newer version of Windows in the process gaining access  to modern web technologies and security fixes.

Another benefit is that CAs that are not active participant in the CABFORUM and who do not follow the root program requirements closely will be sure to stop their use of SHA1 based signatures as soon as they see the user experience impacted.

The same thing will be true of device companies and enterprises who do not as of today have the option to participate in the CABFORUM and even if they did are frankly unlikely to. That is when they see their support calls go up they will change their products and/or processes so that such certificates are not used.

The net of which is by the end of 2017 we will most likely see the complete end-of-life of SHA1 as part of signature suites and we may see an above average increase in modern browser adoption.

Ryan

 

 

Revocation checking, Chrome and CRLsets

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One of the things I often hear is that Chrome no longer does revocation checking, this isn’t actually true.

All major browsers do some form of revocation checking, that includes Opera, Safari, Chrome, Firefox and Internet Explorer.

Google still does revocation checking it just does so through a proprietary mechanism called CRLsets.

As its name implies CRLsets are basically a combination of CRLs, Google crawls the web gathers CRLs and merges them together into a “mega-crl”. This mega-crl is formatted differently than other CRLs but it’s essentially the same thing but there are some important differences, the most important being that due to size concerns Google selectively chooses which CAs it includes in the CRL set and within those CRLs which revoked certificates to include.

With this understanding you have to wonder why would Google introduce this new mechanism if it not as comprehensive as the standard based ways to deal with revocation checking? The answer is simple performance and reliability.

With CRLsets Google is distributing the revocation list, and as such they can make sure that its delivered quickly they do this in-part by taking a bet that they can intelligently pick which revoked certificates are important (IMHO they cannot – revoked = revoked) and by being the one that distributes the list.

This has implications for users, Chrome trusts certificate authorities for which it has no revocation information for it also intentionally treats some revoked certificates as good which exposes you to some risk.

This is especially problematic for enterprises that use Chrome and leverage PKI, there is essentially no chance Google will decide to include your CRL. This is also problematic for those who encounter certificates from those CAs.

That’s not to say CRLsets do not have value they do, but those values have been discussed elsewhere in detail.

But what do you do if you want a more holistic solution to revocation checking? Its simple you can turn on the standards based revocation checking mechanisms and Chrome will use them in addition to the CRLset, to do that you go to Settings and expand choose Advanced Settings where you will see:

 

 

 

Here you can re-enable the standards based revocation checking mechanisms so chrome can do a more holistic job protecting you from the known bad actors on the internet.

Ryan

 

A look at untrusted certificates

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Today I did a blog post on how browsers show expired certificates. I figured I would take the opportunity to capture a few of the other failure cases for certificates.

 

The most severe example is that of an untrusted root certificate, for this scenario I figured the use of https://cacert.org was the most direct example.

 

There are a few cases where this error condition will come up, for example another one is if a server doesn’t include all of the intermediate certificates the clients cannot determine which Certificate Authority issued the certificate.

According to the current SSL Pulse data about 7.4% of the servers in the Alexa top one million may fall into this case.

 

Chrome

Internet Explorer

Mozilla

Opera

 

Safari