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Government-Linked Certificate Authorities in OS X

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Re: Government-Linked Certificate Authorities in OS X

#21

Post by kristofferR »

threeseed wrote: post #16
kristofferR wrote: post #13

Why doesn't the browsers collect information from its users (if they agree to it) about which CAs are used by which domains - and display a strong warning if a different CA than the norm tries to issue a certificate?

Because the m/billions of users bar a few thousand will have no idea what to make of the warning. I mean I don't even know what constitutes a "normal" CA. And to be honest who really cares. Countries increasingly are mandating invasive spying through legislation. Arguing over CAs is like rearranging deckchairs on the titanic.

It wouldn't be much different than certificate pinning is today, just a crowdsourced version.

Sure, the CA system should be replaced altogether, but that's going to take quite some time. In the mean time I think the idea I mentioned could be useful to avoid invisible man-in-the-middle attacks by the CAs. It only requires work by the browser developers, while changing from CAs to something else will take a major effort by everyone who's running a part of the web.

Re: Government-Linked Certificate Authorities in OS X

#22

Post by bsaul »

I could see another weaker but immediately implementable approach to just issueing a list of domain-root certificate maps that someone would have to manage :

Why couldn't browser issue a warning whenever the root CA for a known domain has changed compared to previous browsing sessions ? I suppose MITM attack are targeted and probably depends on the network you're using. If there's a difference between the root certificate for google.com when surfing with your laptop at home or from the office, then there's probably something wrong.

It's a bit similar to what ssh is doing with cert/ip associations.

Re: Government-Linked Certificate Authorities in OS X

#23

Post by captainmuon »

We should come up with a scheme where certificates are signed by multiple CAs (or you have several cross-linked certificates). If one signature changes but not the others, you know something is wrong [1]. It would be beneficial to use CAs from different political blocks, like one from the US, one from China, and one from the EU, to reduce the risk of collaboration.

Of course, a MITM attacker would just strip all certificates and send only theirs along, so you have to have a way to enforce multiple signatures from different blocks. Maybe a httpss url scheme or something.

[1] Something like: http://security.stackexchange.com/questions/6926/multiple-ca...

Re: Government-Linked Certificate Authorities in OS X

#25

Post by mrmondo »

alfiedotwtf wrote: post #24
mrmondo wrote: post #20

I've written a simple script to remove these from OSX: https://github.com/sammcj/delete-unknown-root-ca Pull requests welcome, Don't run unless you know what you're doing, YMMV etc....

Great, until an OSX update :/

Yeah exactly, band-aid for those that are interested / concerned - certainly not a fix.

Re: Government-Linked Certificate Authorities in OS X

#26

Post by kijin »

bsaul wrote: post #22

I could see another weaker but immediately implementable approach to just issueing a list of domain-root certificate maps that someone would have to manage : Why couldn't browser issue a warning whenever the root CA for a known domain has changed compared to previous browsing sessions ? I suppose MITM attack are targeted and probably depends on the network you're using. If there's a difference between the root certif…

That's what certificate pinning is for. And of course, Chrome already refuses to connect to Google if the certificate doesn't match what Chrome expects.

http://tools.ietf.org/html/draft-ietf-websec-key-pinning-12

Re: Government-Linked Certificate Authorities in OS X

#27

Post by sharvil »

kristofferR wrote: post #13

Why doesn't the browsers collect information from its users (if they agree to it) about which CAs are used by which domains - and display a strong warning if a different CA than the norm tries to issue a certificate?

EFF's SSL Observatory [1] does collect information on certs used by SSL enables sites for research purposes.

[1] https://www.eff.org/observatory

Re: Government-Linked Certificate Authorities in OS X

#28

Post by hsivonen »

threeseed wrote: post #11

> Sidenote: A Windows 7 PC has 38 Certificate Authority certificates installed. My Mac OS X Yosemite has 217 Certificate Authority certificates installed. Windows 7 was released 5 years ago. Might be more relevant to compare to Windows 10 given that Yosemite is updated quite regularly.

Doesn't Windows 7 download root certs from Microsoft's repo on demand? I.e. 38 isn't the total number but the total actually seen by that PC.

Re: Government-Linked Certificate Authorities in OS X

#29

Post by skuhn »

grey-area wrote: post #19
dingaling wrote: post #17

Earlier quoted context omitted.

> and they are making steps towards this with measures like pinning aren't they? Pinning is an unscalable hack around the core problem.

I'd be interested to know why if you have the time.

The classic manual method of cert pinning is not feasible for more than a handful of large sites, because each browser that supports it has to update its own pin list.

Google adds a whitelist of public keys to Chrome upon request, only for high impact sites. Firefox does the same, with a different list. Safari doesn't support it at all. IE supports it in a useless fashion.

This is totally unworkable in the long term. Broader support also opens it up to smaller (less savvy) sites who will inevitably get bitten by a lack of foresight. "Oh, I only authorized GoDaddy and now I use Entrust...". However, set too broad a list and you've just given an attacker a list of targets to pick the weakest link from, possibly not dissimilar from choosing a target amongst "all CAs clients support".

The manual method is not the only way, and it's always been apparent that it was not the end game. HSTS and HPKP are important steps forward, and support is decent. As always though, IE is a useless impediment to progress.

https://projects.dm.id.lv/Public-Key-Pins_test

It's going to be a while before HPKP is everywhere, but it's definitely a better approach.

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