[cabfpub] Draft Ballot 185 - Limiting the Lifetime of Certificates: User input

Christian Heutger ch at psw.net
Fri Feb 10 08:06:52 UTC 2017

I remember the time, MD5 has been phased out. From our side it worked well. Customers got informed, that MD5 certs, which are still not replaced, will be revoked by date x and all our customers reissued their certs before the deadline. So I still see OCSP for urgent changes, there was much development on OCSP like OCSP stapling, so the recent issues with OCSP have been solved, meanwhile I see a e.g. 2 years evolution phase for new algorithms good enough. However, algorithm x+1 should be pushed earlier and honoured on usage, e.g. many customers use tools like SSLlabs to test their sites and try to catch the A+ or something like an A++, so maybe that’s the use of SHA3 and e.g. 4096 bit keys already today. With SHA-2 switch most claiming customers on our side came from Windows XP (ok, that product should already be gone, but is still alive) and from many(!) Android users. Because of the big fragmentation, own Android versions by phone vendors and worse update policies result in many problems with SHA-2 changes, latest on SHA-2 full chain. Phasing out with 1 year timeframe wouldn’t only enterprises get in trouble with their clients, inhouse CAs, ..., it would also harm a large user base, e.g. Android users, latest without stock ROM. And currently we also accept users on risk as we push domain validated certificates and accept claiming no responsibility on e.g. phishing as promoting encryption only being safe (as stated e.g. in latest Chrome release). So users believe they are safe to enter details on phishing sites, scam sites, ... as Chrome tells them, they are safe. Not safe is fine, encrypted would also be fine, but safe is also a proofen identity of the site or just stating the operator like with EV. So if it’s not safe to disable SHA-1 right now, validity period wouldn’t be the solution but urging the last operators to replace their certs with SHA-2 and otherwise they will be revoked based on Baseline Requirements. Decreasing from 60 months to 39 months seems not to have helped with SHA-2 now, so why should 39 months to 13 months do? Last changes like internal domain names removal also worked with our customer base, and it was also because of a deadline and revocation warning, not via lifetime.

Von: Ryan Sleevi <sleevi at google.com>
Datum: Donnerstag, 9. Februar 2017 um 21:44
An: CA/Browser Forum Public Discussion List <public at cabforum.org>
Cc: Jody Cloutier <jodycl at microsoft.com>, Christian Heutger <ch at psw.net>
Betreff: Re: [cabfpub] Draft Ballot 185 - Limiting the Lifetime of Certificates: User input

To Jody's point:

Consider the following sites (all times Pacific, because I'm on a Mac right now and I'm too lazy to adjust back to GMT from the UI)

https://amd.com (Symantec; expires 2017-07-21, issued 2014-07-21; https://crt.sh/?id=4638163 )
https://americancrew.com (Symantec; expires 2018-07-10, issued 2014-06-09; https://crt.sh/?id=4324896 )
https://www.ashevillechamber.org/ (GoDaddy; expires 2017-03-06, issued 2012-03-06; https://crt.sh/?id=982926 )
https://bitcoin.hu (Comodo; expires 2019-08-14, issued 2014-08-14; https://crt.sh/?id=4816214 )
https://gm.ca (DigiCert/Verizon; expires 2017-09-18, issued 2014-09-18; https://crt.sh/?id=5021956 )

Despite the Forum's efforts, all of these certificates are SHA-1 and valid through 2017-01-01. That means these sites break when you disable SHA-1, such as Chrome has. I'm sure, if members want to keep debating this as if it's not an issue, I can find certificates from most of the CA members opposed that demonstrate these sorts of issues.

You might be wondering where I came up with this list. It wasn't Certificate Transparency. It was courtesy of Mozilla, by way of understanding what's currently preventing them from disabling SHA-1 on Firefox 51 at 100% - specifically, https://bugzilla.mozilla.org/show_bug.cgi?id=1330043#c7

Until Mozilla disables SHA-1, their users are at risk. They're at risk from malicious parties having taking advantages of CA's past reticence to adopt serial entropy - and I'm happy to name the specific CAs I'm thinking about, if members would like - and they're at risk of CAs misissuing SHA-1 - of which, again, I'm happy to name some specific members who have already proven this is a valid concern.

But this also demonstrates the balance that browsers face when charged with protecting their users - do we block access to these sites (as Chrome is doing, and as Microsoft will around February 15) or not? If we do block these sites, we run the risk of causing the average user to see too many of these messages a day, thus succumbing to warning fatigue, and causing them to ignore these warnings when their information is truly at risk. This makes everyone less secure - either through warning fatigue or through lack of automatic protection.

We can talk about how revocation is the answer - but this is clearly irrelevant, because every one of these certificates is unrevoked. We can argue about how many outgoing links to those specific addresses exist and whether they're "used" - for example, https://www.amd.com has corrected the error, but https://amd.com has not - but that's irrelevant, because browsers intentionally don't collect data to that degree, precisely because it's invasive to users' privacy. So we - the Forum - have no way of determining whether or not our users care about these sites, whether or not the server operators care about these sites, whether or not the CAs care about these sites - but we know these sites will and do break.

For those who are unfortunately arguing we should "phase these requirements in" - we did that, with 60 month certs to 39 month certs. Notice how those 60 month certs are still causing pain in the examples I gave above? That phase in approach doesn't meaningfully work - at least not for validity periods.

What would the world look like if we had required 398 day (nee 13 month) certificates from the get-go? Not a single one of those certificates would be valid beyond 2017-02-01. Browsers - such as Chrome, Firefox, Edge, Safari, Opera, Qihoo360 - could all make an informed decision that they can enforce "no SHA-1" on 2017-02-01, and know *it will not break a single site*.

What an amazing world that would be.
Because it would mean our users were protected from SHA-1 issues - whether past or future.
That's the world we want to move to.
That's the world some member CAs are opposing.

That's why this is about security.

On Thu, Feb 9, 2017 at 11:59 AM, Christian Heutger via Public <public at cabforum.org<mailto:public at cabforum.org>> wrote:
I’m following the discussion already for a while. I understand the reasons, but I also see the customers situation out there. I also saw the votes recently and as a compromise I believe a two year timeframe + up to 90 days on renewal (so a total of 27 months or 820 days to be clear) would be a reasonable timeframe for most customers. However, I still expect some trouble, but maybe some exceptions would be granted. For the need to eliminate any X fast, OCSP still should be the solution, to get an evolution process running, two years should be enough.

Am 09.02.17, 18:47 schrieb "Jody Cloutier" <jodycl at microsoft.com<mailto:jodycl at microsoft.com>>:

    I'm the first to admit that I haven't been following this thread as closely as I would like, but, from Microsoft's perspective, we want shorter certificates and not longer. We would certainly endorse a ballot that would mandate shorter certificate life for the very reason stated below: if we want to eliminate X we would know exactly when the last cert will expire. We've gone so far as to consider mandating this as a program requirement. Anyway, that's our .02.

    -----Original Message-----
    From: Public [mailto:public-bounces at cabforum.org<mailto:public-bounces at cabforum.org>] On Behalf Of Christian Heutger via Public
    Sent: Thursday, February 9, 2017 9:31 AM
    To: CA/Browser Forum Public Discussion List <public at cabforum.org<mailto:public at cabforum.org>>
    Cc: Christian Heutger <ch at psw.net<mailto:ch at psw.net>>
    Subject: Re: [cabfpub] Draft Ballot 185 - Limiting the Lifetime of Certificates: User input

    > I can see why there's some confusion here :-) Ryan is not arguing that we should switch to 13 months so that we will always in future move from "let's eliminate Algorithm X" to "Algorithm X is gone" in 13 months. One would always consider lots of data points in setting such a timetable. His point is that 3.25 > year certs make it very hard to move faster than that in _any_ deprecation scenario, whether simple or complex.

    I don’t believe, moving faster is required for normal situations. If there are issues arising needing faster reaction, revocation and reissue is still a possible way. For normal situations, enterprises need to be able to react and they can’t move faster. Why are most enterprises skipping one Windows version and roll out the next one? As they are not able to move faster in controlled enterprise security environments.

    > I don't agree that replacing your certificates once a year requires automation. It's made easier by automation, but it doesn't require it.

    As I understood the discussion, 1 year is the first step on a road to months or weeks.

    > I'm sure there are plenty of CAs, big and small, who would assert their automation solutions are secure. :-)

    But as you know, there is nothing, which is 100% secure and if we talk about certificates in their sense of encryption and(!) identity assurance, such job shouldn’t be based on automatism.

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