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Let’s Encrypt Now Being Abused by Malvertisers
- skepticaluchiha 11y agoThere are peolpe that are really suprised? This was expected.
- ponytech 11y agoIMO the problem is more "attackers who have gained the ability to create subdomains under a legitimate domain" (not explained how) than Let's Encrypt.
- qopp 11y agoThere are sites that do this as part of their core ui, such as deviantart.
- alexpeattie 11y agoYes, although the subdomains still point to deviantart's servers. The difference here is that ad.example.com ends up pointing to the attacker's server. Because LetsEncrypt needs a very specific response to be served from a specific endpoint, you need this kind of total control to validate a domain and get a certificate issued.
- rmhrisk 11y agosee: https://publicsuffix.org/ https://publicsuffix.org/
- nulagrithom 11y agohttps://letsencrypt.org/howitworks/technology/#domain-validation https://letsencrypt.org/howitworks/technology/#domain-valida... There's a bit more to it than "allowing subdomain creation". You will need control over the DNS records, or ability arbitrarily change the page (essentially).
- eugeneionesco 11y agoThis is not an issue, just FUD from Trend Micro.
- aftbit 11y ago>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 for policing the behaviour of their certificate users. They should just ensure that they only issue certificates for validated CNs.
- chinathrow 11y ago>> in addition, they have stated that they do not believe CAs should act as a content filter. Isn't that what they exactly do when they check the safe browsing API?
- zamalek 11y agoThere 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.
- eridius 11y agoWhy 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?
- Ao7bei3s 11y agoBecause 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.
- Buge 11y agoThere were already free automatically-validated CAs before Let's Encrypt.
- Animats 11y agoAs a CA, Let's Encrypt should only be issuing certs to second level domains. If they want to issue one to a subdomain below that, there should be a check that the second level domain approves.
- roblabla 11y agoWhat about <somedomain>.co.uk ? Or the various other TLD that are 2-level deep already ? I believe it's impossible to implement this properly.
- nitrogen 11y agoThere's a huge suffix list that browsers use to control things like cookie scope: https://en.wikipedia.org/wiki/Public_Suffix_List https://en.wikipedia.org/wiki/Public_Suffix_List https://publicsuffix.org/ https://publicsuffix.org/ Probably includes https://en.wikipedia.org/wiki/List_of_Internet_top-level_domains https://en.wikipedia.org/wiki/List_of_Internet_top-level_dom...
- pdkl95 11y agoWhile I think it is a bad idea to limit which domains can use TLS in an ad hoc style, this issue with stuff like example.co.uk was solved in DNS a long time ago. One of the main features of DNS is the ability to delegate authority for a zone. You use a NS record on a valid name that where you have authority to indicate that some other server is authoritative for a given subset of your zone. If you bought example.com, you can create DNS records like subdomin.example.com. 172800 IN NS ns1.example.com to indicate that ns1.example.com is the authority for the entire subdomain.example.com zone. This includes all further nesting of .subdomain.example.com. Instead of guessing* who is responsible for a zone, you should simply ask the nearest upstream zone authority. Also, relying on lists is almost always the wrong solution - if your security requires you to successfully enumerate something, you are doing it wrong. ( http://www.ranum.com/security/computer_security/editorials/dumb/ http://www.ranum.com/security/computer_security/editorials/d... )
- pfg 11y ago
- joshmoz 11y agoHere is a more complete explanation of Let's Encrypt's views on the subject. https://letsencrypt.org/2015/10/29/phishing-and-malware.html https://letsencrypt.org/2015/10/29/phishing-and-malware.html
- rmhrisk 11y agoMy post responding to this - https://unmitigatedrisk.com/?p=552 https://unmitigatedrisk.com/?p=552
- tremon 11y agoThanks for that response. It is well-written and transparently constructed. That said, you're reading quite a bit more agenda and polemic in TrendMicro's post than I did. Possibly because you've seen this kind of post before :) If you can allow me a bit of proofreading, there are a few typo's in the article: [..] that said it is can be summarized as: -> lose the "is" Maybe the then the issue is -> lose the first "the" It had nothing to do with SSL, the attacker had full control of a subdomain and the attack would have still worked without it. -> The final "it" should presumably refer to SSL, but in this construct it refers to "control". I say “could” because in that not everyone is aware of -> lose "in that" ? Until all CAs are required to log all of the SSL certificates they issue into CT Logs and add are required to CAA -> Not sure of your intent here. "And CAA records are required before requesting certs"? Also, your quotes from the original article render for me (in firefox) as single-line textboxes with scrollbars. Maybe you can change it to force automatic wrapping?
- rmhrisk 11y agothanks, fixed everything but the quotes.
- breakingcups 11y agoTitle should read "Let’s Encrypt Now Being Used by Malvertisers" If someone gains access to a subdomain and is able to place files there, THAT is the problem, not being able to request a certificate for it. To quote both Ford and Raymond Chen: "It rather involved being on the other side of this airtight hatchway"
- deleted 11y ago[deleted]
- staunch 11y agoIn their attempt at shaming Let's Encrypt, only Trend Micro has been shamed.
- ars 11y agoI'm unclear about what the problem is. So the traffic is encrypted. How does that make anything worse? It seems pretty irrelevant to me if it's encrypted or not.
- MrSwagga 11y agoMaybe because it can't be automatically detected by some layer 7 firewall filters/web proxies.
- userbinator 11y agoAlthough some seem a bit squeamish about it, any good firewall/filtering solution should do SSL MITM --- especially now that encrypted connections are becoming the norm. Given that Trend Micro themselves provide AV software that does this, it's particularly ironic since it's already no problem for them to decrypt and scan encrypted traffic. It's likely just their CA division that dislikes Let's Encrypt.
- lini 11y agoNot 100% sure, but if the malicious ad is put on an HTTPS page, it would not be possible to load additional scripts and data from an un-encrypted (HTTP) location as opposed to another valid HTTPS location. Having your malware on an HTTPS site goes around the browser's mixed content restrictions.
- corobo 11y agoYou could just as easily register a separate domain and use HTTPS on that if your goal is to inject scripts in the background. The "problem" being reported here is that the user may think the site is not going to send them malware because it has a green padlock in the address bar
- erostrate 11y agoIndeed, trendmicro doesnt say anything about that. Let's Encrypt says "The concern most commonly expressed is that having valid HTTPS certificates helps these sites look more legitimate, making people more likely to trust them." I agree with Let's Encrypt position, they are not to blame here. https://letsencrypt.org/2015/10/29/phishing-and-malware.html https://letsencrypt.org/2015/10/29/phishing-and-malware.html
- supermatt 11y agoI 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?
- pfg 11y agoThis 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.
- supermatt 11y agoDNS 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.
- pfg 11y agoWoSign is one of the other CAs offering this option. It is unclear to me how TXT verification would have prevent this. The article indicates that the attackers created the subdomain and pointed it at a server they controlled; this means DNS was compromised and creating a TXT record wouldn't have been a problem. Domain owners which are worried about Let's Encrypt can opt to create a CAA DNS record that limits CAs allowed to issue certificates to ones they trust. CA/B BR can be found here[1]. [1]: https://cabforum.org/wp-content/uploads/Baseline_Requirements_V1_3_1.pdf https://cabforum.org/wp-content/uploads/Baseline_Requirement...
- zecg 11y agoIn other news, guns are used to kill people.
- pdkl95 11y ago> 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=<malicious urlencoded URL> 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/
- jmuguy 11y agoAs evidenced by the comments here, the people that count, that is system admins and developers, don't see a problem. Just more FUD from the traditional security players trying to remain relevant.
- solidninja 11y agoI finally created a HN account just to say the same thing. The security problem is that of the website itself and its choices of advertisers, not of the CA.
- Sujan 11y ago> > These DV certificates can help the hacker gain legitimacy with the public. > How? By the lock displayed in the browser that couldn't be there for free that easy before.
- cynix 11y agoStartSSL.
- userbinator 11y agoAs 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 https://news.ycombinator.com/item?id=10685458
- Sephr 11y agoI 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.
- pluma 11y ago> 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.
- ycmbntrthrwaway 11y agoI needed to create valid HTTPS certificate once, as a project to setup MITM proxy and test various applications verification of domain. I just created an account on https://www.startssl.com/ https://www.startssl.com/ with totally fake identity, found some place to register a free domain and got a certificate at zero cost within a few hours. Maybe Let's Encrypt makes it easier to automate, maybe they need to add a CAPTCHA (what for?), but the possibility of creating valid HTTPS certificates for malicious uses was already there. Banks and employers should just teach users to look for green icon near the URL, not just a padlock.