Let’s Encrypt Now Being Abused by Malvertisers • Hacker News Board

Re: Let’s Encrypt Now Being Abused by Malvertisers

#31

Post by pfg » Thu, Jan 07, 2016, 9:14 AM UTC

supermatt wrote: post #28

I havent used Lets Encrypt, but other CAs would validate the owner of the TLD by sending an email to hostmaster. You wouldnt be able to have certificates issued on a subdomain unless you are verified as owner of the TLD. Is this not the case here, and if not, why not?

This is one of many verification mechanisms other CAs offer. A lot of them also offer verification via DNS TXT record, or by placing a file under a certain path and verifying it's being served via HTTP. Let's Encrypt is definitely not the first to offer any of those, and they are in line with the CA/B Baseline Requirements under which CAs operate.

Re: Let’s Encrypt Now Being Abused by Malvertisers

#32

Post by pdkl95 » Thu, Jan 07, 2016, 9:19 AM UTC

> gained the ability to create subdomains under a legitimate domain

As lots of people in this thread have already pointed out, that's the security problem. The DNS zone that was delegated to you, then you have a responsibility to keep the "squatters" away.

> Traffic to this created subdomain was protected with HTTPS

Good. HTTP is obsolete. That doesn't change anything from the perspective of the victim.

> an open DoubleClick redirect

Which is yet another example of how irresponsible advertisers are creating huge attack surfaces.

From the blog they link to:

    bid.g.doubleclick.net/xbbe/creative/click?r1=

It sounds like doubleclick is sending out the harmful redirect. Maybe they should verify URLs instead of blindly believing the query params?

    "msxml.domdocument"

LOL

> These DV certificates can help the hacker gain legitimacy with the public.

How? "The public" probably doesn't even know what a DV certificate is.

It doesn't look like Let's Encrypt is even involved in any of the actual problems that enable this attack.

> As a certificate authority ourselves

... I guess that explains this hit piece ... /sigh/

Re: Let’s Encrypt Now Being Abused by Malvertisers

#33

Post by sametmax » Thu, Jan 07, 2016, 9:19 AM UTC

droopybuns wrote: post #29

aftbit wrote: post #5

>Let’s Encrypt only checks domains that it issues against the Google safe browsing API; in addition, they have stated that they do not believe CAs should act as a content filter. Security on the infrastructure is only possible when all critical players – browsers, CAs, and anti-virus companies – play an active role in weeding out bad actors. I agree strongly with Let's Encrypt's view. They should not be responsible f…

Encrypting everything has consequences. I recently had an IoT pairing issue between two devices. A normal human will not run wireshark to troubleshoot a pairing failure between two devices. I did. I was rewarded with a shitty protocol that could not be evaluated for errors and a moderated support forum that encouraged me to reboot my router. Taken to its extreme conclusion- there are important networking problems tha…

And buckling up your seat belt has consquences. You cannot danse the way you used to on your seat and 1 time out 1000, it actually makes the accident more violent.

Still, you should use the seat belt. All the time.

Re: Let’s Encrypt Now Being Abused by Malvertisers

#34

Post by userbinator » Thu, Jan 07, 2016, 9:22 AM UTC

As a certificate authority ourselves

That says it all, really. This isn't the first time other CAs have attempted to stop LE:

https://news.ycombinator.com/item?id=10685458

Re: Let’s Encrypt Now Being Abused by Malvertisers

#35

Post by userbinator » Thu, Jan 07, 2016, 9:25 AM UTC

droopybuns wrote: post #29

aftbit wrote: post #5

>Let’s Encrypt only checks domains that it issues against the Google safe browsing API; in addition, they have stated that they do not believe CAs should act as a content filter. Security on the infrastructure is only possible when all critical players – browsers, CAs, and anti-virus companies – play an active role in weeding out bad actors. I agree strongly with Let's Encrypt's view. They should not be responsible f…

Encrypting everything has consequences. I recently had an IoT pairing issue between two devices. A normal human will not run wireshark to troubleshoot a pairing failure between two devices. I did. I was rewarded with a shitty protocol that could not be evaluated for errors and a moderated support forum that encouraged me to reboot my router. Taken to its extreme conclusion- there are important networking problems tha…

That's what MITM proxies are for... but I do agree that devices with encrypted traffic, without any means of its owner inspecting it, can be a significant threat.

Re: Let’s Encrypt Now Being Abused by Malvertisers

#36

Post by pjc50 » Thu, Jan 07, 2016, 9:31 AM UTC

droopybuns wrote: post #29

aftbit wrote: post #5

>Let’s Encrypt only checks domains that it issues against the Google safe browsing API; in addition, they have stated that they do not believe CAs should act as a content filter. Security on the infrastructure is only possible when all critical players – browsers, CAs, and anti-virus companies – play an active role in weeding out bad actors. I agree strongly with Let's Encrypt's view. They should not be responsible f…

Encrypting everything has consequences. I recently had an IoT pairing issue between two devices. A normal human will not run wireshark to troubleshoot a pairing failure between two devices. I did. I was rewarded with a shitty protocol that could not be evaluated for errors and a moderated support forum that encouraged me to reboot my router. Taken to its extreme conclusion- there are important networking problems tha…

Of course, not encrypting and authenticating between the devices lets any other compromised device on your network interpose itself in that pairing and do whatever it likes with your IoT devices.

Re: Let’s Encrypt Now Being Abused by Malvertisers

#37

Post by supermatt » Thu, Jan 07, 2016, 9:37 AM UTC

pfg wrote: post #31

supermatt wrote: post #28

I havent used Lets Encrypt, but other CAs would validate the owner of the TLD by sending an email to hostmaster. You wouldnt be able to have certificates issued on a subdomain unless you are verified as owner of the TLD. Is this not the case here, and if not, why not?

This is one of many verification mechanisms other CAs offer. A lot of them also offer verification via DNS TXT record, or by placing a file under a certain path and verifying it's being served via HTTP. Let's Encrypt is definitely not the first to offer any of those, and they are in line with the CA/B Baseline Requirements under which CAs operate.

DNS TXT records I can also agree with, as its as secure as email in the respect that it uses the same potential vector for spoofing.

File verification (which I haven't seen as an option with the multiple CAs I have used) is an alternate vector. It may be in line with the CA/B Baseline Requirements, but by removing this they would likely eliminate this threat.

This is a serious problem

p.s. I note that this "content change" verification mechanism is mentioned as point 6 under 3.2.2.4 of the Baseline requirements. It is entirely feasible that when these documents were written this particular issue wasn't considered. How would one go about repealing this particular point, and thus forcing CAs to comply.

Re: Let’s Encrypt Now Being Abused by Malvertisers

#38

Post by Ao7bei3s » Thu, Jan 07, 2016, 9:38 AM UTC

eridius wrote: post #27

zamalek wrote: post #20

Earlier quoted context omitted.

There is a way to avoid this issue: Let's Encrypt should disallow subdomain registrations unless a TXT record is present for the parent domain. For example, if I wanted to get a certificate for bar.foo.example.com there would need to be a Let's Encrypt TXT record for foo.example.com. Although it's not their responsibility, they can take steps to mitigate it.

Why is this something they should do? If I have complete control over a subdomain bar.foo.example.com, why do I need cooperation from the parent foo.example.com in order to set up something basic like an SSL certificate?

Because A records don't mean complete control over domains.

There is a difference between "I can serve content under this domain (currently)" and "I control this domain (and can decide where it points)".

DNS domain validation is the right way to do domain validation. But it's slightly harder for users, which is why HTTP(s)- or E-Mail-based validation is being done more often.

Re: Let’s Encrypt Now Being Abused by Malvertisers

#39

Post by Sephr » Thu, Jan 07, 2016, 9:39 AM UTC

I don't understand. How is it being "abused"? If the attacker has actual DNS access to create ad.{legitimate domain}.com, then Let's Encrypt is working as intended. So what if they're hosting malware—that's {legitimate domain}.com's problem.

Let's Encrypt has absolutely nothing to do with content behavior safety, only domain validation and encryption to keep data away from prying eyes.

This title is no different from "Chairs Now Being Abused by Criminals". It's nonsensical and completely unrelated. Do you care that criminals have started using chairs to sit down (gasp)? I don't think this even belongs on Hacker News.

Re: Let’s Encrypt Now Being Abused by Malvertisers

#40

Post by pluma » Thu, Jan 07, 2016, 9:45 AM UTC

> As a certificate authority ourselves

This pretty much invalidates the entire argument. TLS is not about making things look more legitimate. If anything, CLAs are to blame for marketing TLS as something it's not.

Let's Encrypt is doing the right thing here, Trendmicro is part of the problem.