Let's Encrypt's New Root and Intermediate Certificates

https://letsencrypt.org/2020/09/17/new-root-and-intermediates.html

by arkadiyt • 6 years ago

448 174 6 years ago

ECDSA is fantastic for all the reasons touched on in this article, but I’m sure the use of NIST curves will draw some criticism. As far as I know, no cryptographer seriously believes the curves to be backdoored, but nonetheless seems to be a hot topic of online discussion. DJB lists them as “unsafe”. Of course, other curve parameters like 25519 don’t have the same widespread deployment that the NIST curves enjoy, so this is a very sensible choice.

schoen2• 6 years ago

Yes, there isn't adequate browser (or other client) support to use Curve25519 signatures in a public CA's certificate.

I'm actually kind of confused about exactly what would be required and exactly what the state of it is, so maybe someone can chime in -- I just know it's not ready.

Another thing I don't understand is what the threat model looks like for applying hypothetically backdoored curves. That is, can you interactively or offline attack ECDHE, ECDSA, or both? Can you derive the private key from the public key, by inspection and calculation, by observing random signatures, by obtaining chosen signatures, or something else?

coder5434• 6 years ago

Yes, there isn't adequate browser (or other client) support to use Curve25519 signatures in a public CA's certificate.

I'm not so sure about that.

https://en.wikipedia.org/wiki/Curve25519#History

"Also in 2018, RFC 8446 was published as the new Transport Layer Security v1.3 standard. It requires mandatory support for X25519, Ed25519, X448, and Ed448 algorithms.[24]"

I haven't confirmed this myself, but it seems like anything that supports TLS 1.3 (a lot of things, relatively speaking) supports both curve25519 and curve448.

Another thing I don't understand is what the threat model looks like for applying hypothetically backdoored curves.

Maybe this article can provide some insight into what people are concerned about: https://en.wikipedia.org/wiki/Dual_EC_DRBG

Obviously, no one has proof that the NIST curves are backdoored, so who knows what kind of backdoor they would have? No one really wants to find out the hard way, though.

barkingcat• 6 years ago

the very nature of a backdoor prevents you from knowing the answer to your threat model questions.

If no-one knows what kind of backdoor it is, how does anyone know how the attack works?

The only sane approach is to assume all of the above.

coder5434• 6 years ago

Even better than curve25519, I would prefer to see the related curve448 supported. I haven't heard any reason to prefer the NIST curves when open alternatives exist. From what I understand, curve25519 is significantly faster than the NIST curves, in addition to being better understood.

And it isn't just DJB speaking against the NIST curves. There's a relevant quote from Bruce Schneier here: https://en.wikipedia.org/wiki/Curve25519#History

The only real advantage I know of with the NIST curves is that they might be more widely supported, which you mentioned, and which is all the more reason why it would be good for an organization like Let's Encrypt to push the industry forward with regards to curve448 support.

I wouldn't mind if they offered options for what kind of certificate you would like them to issue, so people who favor NIST curves could get a certificate signed that way, and people who prefer curve25519 or curve448 could get a certificate signed that way, but I also realize that more maintenance burden is never fun.

But, those are just my thoughts on the issue... maybe I'm completely wrong.

jopsen• 6 years ago

Let's Encrypt started to make HTTPS available everywhere, and to make it free.

That in its own was a revolution.

I would rather seem them tread carefully, and build a reputation for reliability, than trying to push new standards.

Sure LE has a place in standards discussions, as does Mozilla, but as a CA you can't just push stuff..

CAs have to be extraordinarily boring and slow. It's a trust business :)

elmo2you2• 6 years ago

The reasons for using the NIST curve might have less to do with technical merits or security aspects, and more with regulations and certifications. Certifying something including cryptography already certified (NIST curve) is easier/cheaper than otherwise.

As for backdoors, nobody really knows .. the nature of the algorithm itself makes it practically impossible to even detect a backdoor, even when there is one. So far, no evidence of that though. So if there is a backdoor, then whoever has knowledge of it is damned good in keeping it a secret. In my opinion a bit too good to be likely. That said, NIST has been caught before with their pants down. Rather awkward, since that's the organization supposed to certify such things. One can even wonder what worth or real meaning certifications still have, after they got caught with what they did. I'd personally consider it mostly a national US affair, but the reality is that the rest of the world is still dominated by US standards when it comes to the internet.

All in all, the reasons for using the NIST curve might be more economical and people doing security by marking check boxes, rather than about actual security or efficiency.

slim3• 6 years ago

Why would they nées certification ?

GordonS2• 6 years ago

Would be interested to know if anyone here has had customers push back about the use of ECDSA, especially those in the defence sector?

rkeene2• 6 years ago

I haven't, though RSA is much more common

EcDSA is included in NIST SP 800-73 (PIV) but I've never seen cards with it

user59944612• 6 years ago

Working in the finance sector, I haven't seen push back because I haven't seen anybody or anything use ECDSA. ^^

Usage and support is relatively low. Most people have no idea what ECDSA is or how to use it. There are some issues in java versions (7 or 8) if you try to use ECDSA. I personally don't find the elliptic curves and parameters easy to grasp and I have a math background (multiplying large numbers was much more palatable), I think a developer would quickly hit a roadblock if they tried to work with it.

Long story short. There is no benefits to ECDSA (over RSA) so there is really no reason to push for it.

The only place where DSA is somewhat used is SSH keys. SSH has its own crypto routines, they've added support and pushed DSA for some time. Keys are a bit shorter so it's nicer to copy paste to github or digital ocean.

nurettin• 6 years ago

I'm sure this is about the mathematical soundness of the prime numbers used in elliptic curve cryptography, but wouldn't it be much easier to access half the internet's traffic if root certificates were compromised instead?

sjwright• 6 years ago

When you say access, do you mean intercept and decrypt?

I’m fairly sure root certificates are only affect the browser’s trust of a server’s public key and is not involved in the security of encryption—for that you’d still need the server’s individual private key.

And even then I’m still not sure if the private key is sufficient given modern encryption protocols. Hopefully someone else can chime in to elaborate here.

ilaksh• 6 years ago

(Not sure people realized this is sarcasm.) Right because if they believe something crazy like there being a backdoor in something recommended by the government then people will just say they are not a real cryptographer. Because of course no part of our government ever does anything tricky like backdoors and even if one part of the government did, it could never influence another part that made recommendations to the public for what security algorithms to use. And of course anyone suggesting that such a thing might be possible is just an insane conspiracy theorist.

tyingq• 6 years ago

"As far as I know, no cryptographer seriously believes the curves to be backdoored, but nonetheless seems to be a hot topic of online discussion. DJB lists them as “unsafe”."

I'm not very well educated in this space. Is DJB historically prone to exaggeration?

toast03• 6 years ago

the NIST curves are unsafe, regardless of if they are backdoored. In order to use them safely, you have to carefully prepare your private key, because some keys are unsuitable. for curve 25519, you just need a decent secure random, all keys in the keyspace are good.

rvnx• 6 years ago

"NIST promotes U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic interests of U.S. companies"

I don't think it's incompatible with a backdoor.

Why would they NOT backdoor it ?

throw0101a2• 6 years ago

FIPS 186-5 and SP 800-186 (currently in final draft) will have new curves:

NIST is proposing updates to its standards on digital signatures and elliptic curve cryptography to align with existing and emerging industry standards. As part of these updates, NIST is proposing to adopt two new elliptic curves, Ed25519 and Ed448, for use with EdDSA. EdDSA is a deterministic elliptic curve signature scheme currently specified in the Internet Research Task Force (IRTF) RFC 8032, Edwards-Curve Digital Signature Algorithm. NIST further proposes adopting a deterministic variant of ECDSA, which is currently specified in RFC 6979, Deterministic Usage of the Digital Signature Algorithm and Elliptic Curve Digital Signature Algorithm. Finally, based on feedback received on the adoption of the current elliptic curve standards, the draft standards deprecate curves over binary fields due to their limited use by industry.

* https://csrc.nist.gov/news/2019/comment-on-draft-fips-186-5-...

I'd be curious to see if the NSA will allow them for their 'Suite B' equivalent for classified stuff.

tialaramex10• 6 years ago

The only permissible keys are:

RSA keys of 2048 bits or some larger multiple of 8 bits or ECDSA keys from NIST P-256, NIST P-384 or NIST P-521 curves

https://cabforum.org/baseline-requirements-documents/ (See section 6.1.5)

Other keys violate the Baseline Requirements which are common rules agreed between the major CAs and Browser vendors. Now, a CA could choose to just disregard the BRs, but then they're automatically in violation of the root trust programme rules for the major root trust programmes - at least Microsoft, Apple, Mozilla, Google, then arguably Oracle (because Java) and some other smaller outfits. So that's probably the end of that Certificate Authority, at least for the Web PKI.

Individual root programmes also have their own rules, and so in this case Mozilla's rules are important because they further restrict keys to RSA or ECDSA P-256 or P-384 only.

https://www.mozilla.org/en-US/about/governance/policies/secu... (section 5.1 this time)

Now, those are just policies, you can change policies, but that's not up to Let's Encrypt. If you believe Mozilla needs to support Curve 25519 then that's a bunch of software development you can volunteer to do, followed by lobbying all their competitors because it's futile if only Firefox supports it anyway.

colmmacc• 6 years ago

In modern times, the keys on a SSL certificate don't directly encrypt the session key used to protect communications between your browser and web-server. Instead the key only signs the diffie-helman share that a web server uses. Web-server operators are free to use 25519 for their ECDH shares if they want to, the curve used there does not have to match the certificate's curve.

Even if the NIST curves are backdoored, the backdoor wouldn't be able to passively decrypt TLS sessions. At best it might allow someone with knowledge of the backdoor to impersonate a web-server, but that's an active attack and it would be very risky for the attacker. They'd run a huge risk of disclosing their back door capability.

coder5434• 6 years ago

Can you link to a config example for nginx for what you’re describing in your first paragraph? Or a web framework in any language? I’ve never seen that done before, where the DH shares don’t match the certificate type. But, I’m definitely not an expert on the low level details of TLS.

tlb2• 6 years ago

Active attacks are effective and not that risky. For most web services, the attacker only needs to intercept a single transaction in order to get the session cookies and then you are pwned. Since they only need one, they can hit you with a DNS cache poisoning attack and simultaneous clickjacking attack while you're on a public WiFi.

In general, I'm skeptical of any "this attack isn't really practical" arguments. They have a way of becoming practical enough for high-value targets, so it's not something I want to use.

hashamali• 6 years ago

For the last five years, Let’s Encrypt has had one root: the ISRG Root X1, which has a 4096-bit RSA key and is valid until 2035.

Somewhat tangential, but what happens to all active certificates when the root key expires?

axaxs• 6 years ago

They all become untrusted, if the verifier does their job. That said, a root doesn't issue site level certificates, so the intermediates and issued certs themselves would expire first.

LeonM• 6 years ago

CAs simply never sign a cert with an expiry longer than their own root cert.

Thus, by the time the root cert expires, all client certs will already be expired.

masklinn• 6 years ago

what happens to all active certificates when the root key expires?

They expire, but normally the CA wouldn't issue certificates outliving their root.

It can be a concern for legacy devices whose trust store doesn't get updated, but really no more so than any other cert expiration or revocation.

akadruid1• 6 years ago

This actually happened recently and some older stuff stopped working. there's a write up here: https://www.namecheap.com/blog/sectigo-ssl-certificate-root-...

user59944612• 6 years ago

That blog article is a poor explanation of the issue.

The root CA from namecheap was expiring. They tried to recreate it, only changing the date, to continue to issue certificates to customers with it the same way.

They hoped users/systems would accept their newer CA automatically after the old CA expired. CA are additive, there are many configured on a system, it's standard practice to add more by keeping existing ones and adding new ones.

This blew up in their face monumentally because having two identical CA is conflicting. Things failed to verify after the original CA expired.

Ayesh4• 6 years ago

Any untrusted, expired, or revoked certificate in the certificate chain (includes root, lead certificate, and all intermediates), means the client will not trust the connected.

GordonS2• 6 years ago

From the article I can see that using ECDSA instead of RSA could save up to 400 bytes per connection - that's nice.

Aside from certificate and key size, my understanding is that ECDSA is less computationally intense than RSA, but this gets only a brief mentioned in the article - does anyone know how CPU use compares for typical setup of a TLS connection for ECDSA vs RSA?

arkadiyt2• 6 years ago

Here's a 2017 Cloudflare blog post that compares the performance of ECDSA sign and verify operations (using 256 bit keys) against RSA sign and verify operations (using 2048 and 3072 bit keys) on various CPU architectures:

https://blog.cloudflare.com/arm-takes-wing/

zepearl3• 6 years ago

Questions:

- Do the graphs mean that the "sign" operation of OpenSSL when using ECDSA is many times faster and the "verify" operation is ~4 times slower (compared to RSA)?

- I suppose that "sign" is linked to issuing certificates, while "verify" would be involved to checking certificates?

(sorry, I'm not a pro with this stuff)

cpeterso• 6 years ago

The article says ECDSA has “correspondingly faster encryption, decryption, signing, and verification operations” than RSA.

Ayesh4• 6 years ago

I delivered a talk about TLS performance and how EC certificates compare to RSA, and their strengths are compared. Slides in PDF: https://ayesh.me/files/talks/TLS-and-Headers/TLS-and-Headers...

You can also do a simple benchmark with `openssl speed`.

jng• 6 years ago

It would be nice if they included a TL;DR notice at the top saying: “1. If you are a user of let’s encrypt today, this announcement does not imply that you need to do anything at all, and, 2. The main thing is that new certificates are shorter and will take up less bandwidth, plus also safer.” In any case, thanks for the great, free service!

colesantiago• 6 years ago

I agree, I wish articles like this at the very least summarised their article first before going into a deep technical rabbit hole.

edoceo2• 6 years ago

Side note: a TLDR at the top is called a BLUF = Bottom Line, Up Front.

https://en.m.wikipedia.org/wiki/BLUF_(communication)

pfundstein• 6 years ago

A TLDR is traditionally at the bottom, but there's no rule against putting it at the top.

cortesoft• 6 years ago

But no one knows what that means, so you would have to explain the whole thing every time you use it, defeating the purpose of a short acronym.

Say tl;dr in the first sentence and everyone knows what it means.

zeroimpl• 6 years ago

Interesting, seems pretty similar to an Executive Summary which also would have been very useful here.

Ayesh4• 6 years ago

In hindsight, Let's Encrypt is good at backwards compatibility and actionable information. I suppose the target audience is technical.

LE is phrasing out their v1 API, and they email all users of v1 if they recently issued certificates with it. I suppose majority of non technical users of LE don't even visit the web site, apart from downloading the ToS PDF.

anderspitman• 6 years ago

I don't want to go too far OT, but had a question if someone wouldn't mind answering it or pointing me to some materials.

I've been digging into DNS and TLS lately. Given the way ACME works (essentially using DNS to verify you own a domain before giving you a cert), what's the reason you can't just put your public key in a DNS record? I'm assuming it has something to do with security issues at the DNS level, but don't really know.

jcrawfordor• 6 years ago

This is basically the idea behind DANE. The problem is that DNS was historically unauthenticated and so just as vulnerable to on-path attacks as HTTP - perhaps more so due to the distributed, hierarchical nature which enables certain types of takeovers.

DANE assumes that DNSSEC is in place, so that the DNS records are authenticated. This allows the DNS records to be used to deliver TLS trust information in a way that is still ultimately rooted in a certificate authority (whoever operates DNSSEC for the TLD).

Adoption has been limited, mostly because adoption of DNSSEC itself has been limited, arguably because DNSSEC is overcomplicated and high-maintenance, but also just due to a lack of motivation. Similarly, users couldn't care less about how TLS trust is delivered and DANE has never really gotten a big corporate champion to push for it, so there just hasn't been the drive. Industry seems to have chosen DNS-over-HTTPS as the long-term solution to many of DNS's problems, and it clashes somewhat with DANE - I'm sure you could make them work together but it would definitely become awkward

AndyMcConachie• 6 years ago

Where DANE has seen pickup is in the SMTP space. https://stats.dnssec-tools.org/

J0_k3r• 6 years ago

I'd also like an answer for this.

wgetch• 6 years ago

What happens if both DNS requests are hijacked? Could an attacker return both a different IP and a different public key that correspond to a malicious server?

Edit: I should clarify, I think the issue stems from DNS being a potential attack vector itself. You can't blindly trust what DNS tells you. This is precisely the problem that certificate chains (issued by a trusted third party) purport to resolve-- one of trust.

Ayesh4• 6 years ago

Well there's DNSSEC. Implementation details (such as lack of practice in key rotation, TTL, etc) aside, DNSSEC works and LetsEncrypt validates it.

Then there is Certificate Transparency logs. It will be passive action at this point, but it's an action regardless.

Let's Encrypt checks DNS validation and DNS CAA from multiple PoPs, but I don't think it's enforced by CA/B requirements to do so (happy to be corrected).

Polylactic_acid• 6 years ago

One possible reason is that its more likely that your individual dns is being modified/tampered with than it is for LEs servers. This way your individual ISP can't mess with things.

kilburn4• 6 years ago

As other comments said, DNS is vulnerable to man-in-the-middle attacks without DNSSEC, and DNSSEC is not widely adopted.

However, even with DNSSEC, bob could obtain domain.tld's keys and then use them to MITM alice's DNS requests, getting her browser to show a malicious site for domain.tld complete with a trusted certificate. Furthermore, bob can do this for alice and only alice, decreasing the odds of detection by a large margin.

With LE you gain:

- Targeted attacks harder to pull off, since you would need to successfully attack the LE servers/networks first and then your actual target.

- LE participates in the certificate transparency initiative, meaning every time a certificated is emitted for a domain it gets recorded.

These things are particularly relevant when you consider that in most cases the DNS is either directly or indirectly controlled by state actors at their root. With DNS-only, they could pull off such targeted attacks without anybody noticing. With LE, they can still pull off these attacks, but there would be a papertrail when that happened.

tssva2• 6 years ago

DNSSEC is not about protecting MITM attacks against DNS traffic. DNSSEC is about validating that DNS records have not been tampered with. Are you thinking about DNS over HTTPS and DNS over TLS?

slim3• 6 years ago

Let's not forget that letsencrypt is an EFF project when the shit hits the fan

jaas• 6 years ago

EFF is a strong supporter but Let's Encrypt is not an EFF project. Let's Encrypt is owned and run by Internet Security Research Group:

https://www.abetterinternet.org/

slim3• 6 years ago

the project is older than that organisation

egberts1• 6 years ago

I couldn’t do OCSP stapling with my Firefox 80 against my LetsEncrypt website. Had to turn off stapling.

octorian3• 6 years ago

I really wish Let's Encrypt had a solution for those of us with lots of "internal" devices that neither need public access nor are capable of running an automated renewal job (routers, switches, IoT gizmos, etc).

All of these things come with half-baked self-signed certs, and web browsers and mobile devices these days are making it increasingly difficult to actually stomach such certs for anything at all.

I wish the "SSL All The Things!" crusaders would consider this use case once in a while, and actually offer a usable solution.

(Some of us could go through the trouble of setting up a private CA to deal with this issue, but getting everything to trust your own personal CA root seems like almost as much of a hassle at times.)

ricktdotorg• 6 years ago

look into Cloudflare’s cfssl. it’s really great if you just want a simple internal CA.

arkadiyt2• 6 years ago

I use mkcert [1] with great success - it's easy to setup locally trusted certs which I load onto my router and other devices.

[1] https://github.com/FiloSottile/mkcert

wtallis• 6 years ago

That seems like a nifty tool, but it doesn't seem to do anything to address the difficulty of getting your private CA trusted on more than one of your devices. I'd like to be able to access my router and switch configuration interfaces from more than one client PC, and perhaps even from a smartphone.

sleevi• 6 years ago

One of the challenges in this space is similar to captive portal detection. It’s not enough to have a solution, you need the vendors of those devices to adopt the solution.

Unfortunately, just like captive portals want to avoid detection by your OS [*], the vendors of these devices want to do the least possible work, for the lowest possible cost, never updating or supporting the device once sold. Any new solution is more work for them, especially early on when things are still in development/in flux and may require changes over time, since the problems in this space are actually rather difficult.

It’s not that this problem isn’t important, but rather that there’s no clear good path here. However, even still, the alternative (of HTTP) is much worse for the Web, so TLS is still promoted aggressively.

[1] The reason captive portals want to avoid OS detection is because the OS-spawned UI generally doesn’t have access to your browser cookies. The ecosystem has mostly ossified around a few captive portal vendors, who want your cookies either for advertising/demographics/traffic, or want to offer “Sign in with Social Network” (to both track and... advertising). So they want you to use your main browser, not the OS UI, and thus want to actively avoid OS detection. It’s sad.

tialaramex10• 6 years ago

The very long term good news on captive portals is that users hate them, so they're doomed on that basis.

octorian3• 6 years ago

One of the challenges in this space is similar to captive portal detection

I really wish someone had thought of that problem when defining the 802.11 specs. Though I suspect the idea hadn't even occurred to them at the time.

This was much worse back in the mid-00's when WiFi was a newer use case. Seemed like flipping open my laptop in a public place back then would suddenly cause all the network-connected widgets on my desktop to go absolutely berserk as a result of portal nonsense.

at_a_remove• 6 years ago

I could not agree more. Information Technology, for reasons unknown to me, seems to ferment a kind of extremism with a large helping of "if you are NOT doing it this way you are what is killing the world," and the "SSL All the Things!" people are a great example of it. I've heard people suggest that you should just dump your web-serving software in favor of a different webserver that works better with Let's Encrypt, nevermind that a lot of people in the real world are running niche proprietary software that has very specific webservers they are tightly-integrated with. And -- it has been argued to me -- the solution was to not just get in that service sector in the first place.

DenseComet• 6 years ago

Most of the time, you can stick Nginx or HAProxy in front of it all, and terminate TLS there, with the last part on your interal network being HTTP.

baybal2• 6 years ago

Reminds me how either Xiaomi, or some other fairly big smart things co. bricked few millions of their smart lightbulbs when their root cert expired, and they had no valid cert left to sign a new firmware.

galaxyLogic• 6 years ago

Some of us could go through the trouble of setting up a private CA to deal with this issue

I've read about doing that for development purposes. But it sounds complicated. Therefore I wonder couldn't there be an open source solution that produces an npm module which when I run it creates a private CA for me?

I mean if it is complicated to create a private CA, why not automate that task?

martijnvds• 6 years ago

"mkcert" is a tool to automate this: https://github.com/FiloSottile/mkcert

omBratteng• 6 years ago

I've deployed step-ca internally and have my root certificate added through cloud-init for new servers. Also supports ACME https://smallstep.com/docs/getting-started/

silon42• 6 years ago

(Some of us could go through the trouble of setting up a private CA to deal with this issue, but getting everything to trust your own personal CA root seems like almost as much of a hassle at times.)

This is the actual problem... setting up your own CA for internal networks could be automated relatively easily.

bsdubernerd• 6 years ago

The problem is not the self-signed cert or CA. The problem is managing trust on the devices themselves.

Imagine you want to trust only _your_ self-signed cert or CA root for a specific service. Good luck making that work.

This issue should be so common that there should baked-in functionality in every piece of software to allow for this. It's often totally missing or implemented incorrectly (self-signed certs or custom CAs are often trusted in _addition_ to the system CA roots!).

hvidgaard• 6 years ago

Let's Encrypt revolves around short lived certificates and automated solutions for updating. I think your best bet is having an internal "service" (could be in a docker container), that do the updating. If you can SSH into the device, you can write a script that does it.

mrzool• 6 years ago

I point a bunch of subdomains to my local IPs using https://nip.io and authenticate them all using a wildcard Let’s Encrypt certificate. Works great.

g8oz• 6 years ago

A very detailed tutorial with screenshots for those of us with no clue would be much appreciated.

vmladenov• 6 years ago

https://github.com/acmesh-official/acme.sh this works for me for most of my devices at home. pfSense and Proxmox both have plugins for it. Each device requests its own certificate for a host on a private subdomain of a domain I own e.g. hostname.private.domain.com

mrweasel• 6 years ago

That still only works if your device is able to reach the internet. We have a bunch of servers which aren't directly on the internet, because they don't need to.

filleokus2• 6 years ago

Even when you have a private CA, you still have the issue of getting everything in your environment to trust it. Even in an enterprise setting, from my experience. Most workstations and servers are managed and have the root cert in the trust store, but then you have a long tail of appliances and containerised applications, or OSS software that doesn't use the OS trust store or BYO devices.

With publicly trusted certs you instead trade the trusting-CA-issue for the issuing-issue.

I'm starting to think that it's easier to use publicly trusted certs with FQDN for internal use. Some kind of ACME-proxy, and portal, which is publicly accessible and can respond to ACME inquires. Maybe in combination with some non-LE CA that can issue long lived certs for certain uses where updates can't be automated (e.g network appliances). But then there's the Certificate Transparency Issue, leaking internal names etc.

The dream would be a LE issued sub-CA limited to *.internal.example.com, so you can have an "internal" CA that is publicly trusted.

szszrk• 6 years ago

That would mean I can issue a valid, trusted worldwide, certificate what will work on your internal site.

Using public domains for internal sites are the way to go in my opinion. As long as you pay the bills you have guarantee that you control your domain. You can issue any kind of certificates and so on. If you have a nice naming scheme you won't leak that much info in then Internet. A lot of companies I know does that, by the recommendation of security teams (due to issues with using .local or .example.com domains).

cm21873• 6 years ago

Well Let's Encrypt has a solution, it is DNS authentication, which doesn't require Let's Encrypt to establish a direct connection to the device. But you still need a way to automatically renew the certificate (your DNS must have a supported API) and deploy it automatically. But that's not a Let's Encrypt problem to solve.

jackweirdy• 6 years ago

I use this solution myself.

I have a domain name I own and only have A records configured for use on internal DNS.

Externally it is managed by cloudflare, and certbot uses the cloudflare plugin to renew certificates before deploying certs to my hardware over telnet

dingaling2• 6 years ago

But that's not a Let's Encrypt problem to solve.

But it's a problem they permitted to arise by enforcing 90-day expiry

An internal web config interface could happily use a 10-year cert

alanfranz2• 6 years ago

lots of "internal" devices that neither need public access nor are capable of running an automated renewal job (routers, switches, IoT gizmos, etc).

How is that a CA's reponsibility? I wish vendors would setup an appropriate API for dealing with that on their devices. Quite often you need to enter strange web interfaces in order to setup a certificate.

Let's Encrypt needs to verify you're in control of the hostname. This can happen with either http or dns verification. DNS verification with certbot requires you to setup almost nothing (i.e. you don't need the machine running certbot to be exposed to the public internet) if you're using a supported DNS provider (there're many) for the zone.

So, the missing part is NOT in let's encrypt infrastructure. It's in the device API. You can launch the certificate renewal script just about anywhere (e.g. a small server or vm within your network that can access the internet); but then, how would you automatically deliver the certificate to the device? That's the missing link.

johannes1234321• 6 years ago

How is that a CA's reponsibility?

The request wasn't (only) asking for a solution by the CAs but by the '"SSL All The Things!" crusaders' which includes creators of browsers and mobile devices enforcing stricter rules and a request to take these things into more consideration.

In my words: We need solutions for non-technical individuals to run a somewhat secure environment locally without being confronted with security warnings everywhere. A CA can play a role in that, but probably not fully solve it.

imtringued• 6 years ago

Are you joking? The primary reason why one would want one certificate per device is because you are directly connecting to the device instead of letting the device connect to the vendor API which is already behind HTTPS. Your idea will just lead to a lot of bricked IoT devices once the vendor takes his certificate renewal API down.

friendzis2• 6 years ago

The solution is somewhat simple - have Let's Encrypt (or any root CA) issue intermediary CA limited to your domain. You "only" need devices to trust the root CA and could issue certs at will. The problem is that this use case was/is a threat to CA business model and is not really supported in the current cert infrastructure.

lxgr• 6 years ago

Isn‘t that mostly because the necessary X.509 extension isn‘t widely supported?

Of course, this seems like a chicken and egg problem, but my point is that adoption would take a couple of years in practice.

ikornaselur2• 6 years ago

I use DNS auth for internal certificates. I have multiple domains that only have entries on 10.0.0.0/8, mostly as *.identifier.domain.tld. With DNS auth they all have valid certificates from LetsEncrypt.

gfxgirl2• 6 years ago

Do you actually have that or are you suggesting it a solution? Unless something changed you can't get certs for subdomains unless they they are the public suffix list and getting on that list is non-trivial.

dingaling2• 6 years ago

DNS Auth doesn't work with split-horizon DNS though, since the LE process will update the internal view instead of the external.

It sounds like you've put all your RRs in one flat zone visible internally ad externally but then that breaks device network portability, since mail.example.net on 10.x.x.x won't be reachable once outside the internal network

ACME and LE were really developed without an understanding of how certs work in the IT World. They were developed by folks who spin up a service on AWS and think that's how the world works.

tracker1• 6 years ago

You can use dns for certs instead of web/http verification.

qwertox• 6 years ago

Maybe some kind of wildcard approach would be helpful, where you generate your Let's Encrypt certificate with a wildcard, and are able to distribute it automatically to every device via a standardized API.

That way only one device (possibly a Raspberry Pi) would actually be confronted with the task of generating the certificate and validating the verification requests from LE's servers.

This is what I'm doing at home: on a public VPS I have a custom made DNS/HTTP-server, which is pointed to by the NS-Record for the subdomain int.example.com by my DNS-Provider for my domain example.com. So everything but int.example.com is under control of the DNS-Provider, int.example.com is under the control of my custom DNS/HTTP-Server.

The local Raspberry Pi invokes certbot, gets the authentication tokens from LE's servers, POSTs them to the DNS/HTTP-server via HTTP, LE's servers query the DNS-server for the TXT-Record and certbot then continues with its work of storing the new certificates. Finally a script then distributes these certificates to the local HTTP-servers.

The thing about these certificates is that they contain a wildcard certificate for * .int.example.com, and this way I get a wildcard certificate covering server-1.int.example.com, server-2.int.example.com, ...

If the IoT-devices would have a standardized API to deploy the certificates to them, then I could access the ip camera via https://ipcam-1.int.example.com.

The public DNS/HTTP-server does not respond to requests of any of the * .int.example.com subdomains. The local Pi-Hole has all the DNS-records for those subdomains.

maxekman• 6 years ago

What a pleasure to read this post! Very well written, informative, and accessible for readers of most technical levels.

ggm• 6 years ago

Remembering that *.domain cannot span dots in certificates, and the consequence for SNI if you dry to use FQDN as a dot-separated space beyond the "flat" model.

The convergence of certificate issuance, domain names, domain matching logic, configs, port-binding, information leakage. Its a nightmare. 5 tuple be damned: the higher protocol layers are now deciding how to de-mux your service.

Let's Encrypt's New Root and Intermediate Certificates

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