2016-11-27 14:09 GMT+01:00 Jakub Zelenka <bu...@php.net>: > > > On Sun, Nov 27, 2016 at 1:06 PM, Jakub Zelenka <bu...@php.net> wrote: > >> >> >> On Sat, Nov 26, 2016 at 3:49 PM, Niklas Keller <m...@kelunik.com> wrote: >> >>> Morning Internals, >>> >>> I plan to distrust SHA-1 certificates by default in PHP 7.2. All major >>> browsers will no longer trust SHA-1 certificates starting already >>> 2017-01-01. >>> >>> Unfortunately, PHP doesn't even provide a way yet to limit the accepted >>> algorithms for certificates. The RFC fixes that and introduces new >>> defaults >>> for PHP 7.2. The "signature_algorithms" context option will also be >>> backported to PHP 5.6, which is only supported until the end of 2016 with >>> regular releases, but after that there will be two more years of >>> security-only updates. Therefore I'd like to get this done before the end >>> of 2016. >>> >>> Currently the RFC aims for BC and doesn't restrict the algorithms on >>> older >>> versions. As all major browsers start distrusting those certificates on >>> 2017-01-01 I'm not sure whether that's the correct choice. I'd like to go >>> secure-by-default there and disable SHA-1 also on older versions. People >>> which really need longer can always opt-out and add the needed algorithms >>> again. Unfortunately, we didn't announce any plans regarding SHA-1 yet, >>> so >>> this might be a bit last-minute. >>> >>> You can read the full RFC in the wiki: >>> https://wiki.php.net/rfc/distrust-sha1-certificates >>> >>> >> I think you should change the format to match the one supported by >> OpenSSL [1] which is also simpler. >> > It is exactly in OpenSSL's format for SSL_CTX_set1_sigalgs_list.
> In general I'm not a big fan of such defaults especially when new values >> can be added later (e.g. EdDSA that is specified in TLS 1.3) so we have to >> keep it up to date which was kind of issue in the past. >> > That's true, but I don't see a way in OpenSSL do have a blacklist instead, but we could do that in our own verify callback. > However I see the point that we should make it easier for users to have it >> secure by default so it's probably a good choice. It's not actually just >> about SHA >> > > Ah sent before I finished it. :) I wanted to say that it's not just about > SHA-1 but also MD5 that I think we might still support but would have to > double check that... > I wanted to double-check that, too, but didn't do that yet. If MD5 is still supported, we should definitely put it into PHP 5.6 as a security update. As far as I can see, MD5 support is the case if it has not been disabled by the OpenSSL version in use, as all supported algorithms are allowed by default. SSL_CTX_set1_sigalgs is anyway only supported starting in OpenSSL 1.0.2, so we need a custom verify callback for older OpenSSL versions. In our own verify callback we can use a blacklist instead of the suggested whitelist by default. Regards, Niklas
