Re: [Acme] Considerations about ACME BoF

"Salz, Rich" <> Mon, 30 March 2015 16:38 UTC

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From: "Salz, Rich" <>
To: Massimiliano Pala <>, "" <>
Thread-Topic: [Acme] Considerations about ACME BoF
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Date: Mon, 30 Mar 2015 16:38:02 +0000
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Subject: Re: [Acme] Considerations about ACME BoF
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Thanks for your detailed note.  I want to make sure we have started to address your issues. Stephen responded to the procedural ones, and from your reply it appeared to me that you are, basically, satisfied.  Let me talk to the technical points you raise.

Reinventing the wheel.  Many parties have invented certificate enrollment protocols before, including the IETF and W3C and various commercial organizations. None of them have been very successful in meeting an important need: setting up a certificate for a small independent website. The best we seem to have is “have a human click here.”  Perhaps that’s a mindshare or deployment, as opposed to strictly a technical, issue, but I tend to think not, and based on the sentiment in the room, many people share that opinion.

Message format. Definitely something for the WG, once formed, to decide.

Weak points in the draft, which is about discoverability.  This is a general issue, and probably outside the scope of this group.  How is this problem solved now with existing enrollment packages?  (That’s almost a rhetorical question but not quite.)

Issuer trust issues:  I think this probably imposes some requirements on the protocol. For example, explicitly identifying the issue CA, and perhaps its trust chain, in the response messages so that the appropriate local configuration can be done.

So, in my view, you’ve raised some good questions that need to be addressed, but haven’t convinced me that this effort would be fundamentally flawed from day one. I would love to see if others share your view.

Senior Architect, Akamai Technologies
IM: Twitter: RichSalz

From: Massimiliano Pala []
Sent: Friday, March 27, 2015 10:32 AM
Subject: [Acme] Considerations about ACME BoF

Dear ACME BoF-ers,

when I started to write this e-mail I did not expect to get this long - since the content might be a bit controversial, I would encourage people to stick to the technical arguments and not start a flame war about the topics (that happened in the past.. many, many, many times...).

After attending the BoF and speaking with several people, I feel compelled to bring to the community's attention some concerns about ACME. I have two different types of concerns - procedural (and this might require a broader audience, probably a cross post to the ietf ml), and technical. I would like people commenting on both.

I think that ALL of the following points should be addresses before any decision about forming a new WG or even adopting the proposed I-D as a working item is taken.

Here's my concerns.

Procedural Issues.

Let's Encrypt. When the "Let's Encrypt" initiative was presented, I was quite confused about the scope. We all agree that IETF is about defining protocols on the wire - not promoting specific products or business models. However, in this case, I was under the impression that the IETF was sponsoring a specific piece of software and a new CA initiative that will be soon operational. Besides the fact that the new Let's Encrypt CA might (maybe not now) be a commercial viable initiative, my question is: why a non-existing, commercially viable, non-standard-based initiative is being presented at the IETF ? This is really troublesome especially in the view of this creating a precedence. What happens when another vendor comes to IETF and presents similar pitches about their products - what basis do we have to deny that presentation anymore ? This, I think, it is a really important point that should be discussed deeply.

Overstepping the Technical Boundaries. As it was pointed out during the BoF, the proposed initiative does not address any technical issue, but, instead, is pushing a specific BUSINESS model. I found very inappropriate the examples of "I could not get my certificates in 45 minutes.." as this is a NON argument. Besides the many issues about an automated certificate issuance (even for just a DV cert), the choices made by current Internet CAs (I am referring to Internet CAs because for corporate or "closed" PKIs automation HAS NEVER BEEN A PROBLEM by using current standards) are based on POLICY decisions and not technical merits. Is IETF going to be in the policy decision business instead of focusing on technical aspects of interoperability?

Real Scope of ACME. I think there should be a discussion about where this work is supposed to land. If it is another attempt (as noted during the BoF) to push further DANE (even when, as pointed out during the BoF, there is not much real interest in the real world for it) possibly to replace work like WebPKI or PKIX protocols, this should be clearly stated. Also, if that is the case, I think we are potentially choosing a single-point-of-failure model for trust (DNSSEC) which is scary and dangerous especially from a privacy perspective considering who is in control of top-domain keys. Privacy advocates should really be concerned about this issue.

Technical Issues.

Reinventing the Wheel. During the meeting I already expressed my concerns about many different aspects of the proposed scope. First off, we have a serious problem with overlapping over EXISTING IETF standards for message formats that are perfectly viable and currently deployed in a lot of environments. I am referring to the CMC / CMS / EST. Lot of time and engineering efforts have been spent over these formats and tons of certificates are, today, managed using these formats. Moreover, these formats allow for deploying systems with multiple factors of authentication and hardware tokens. I should not have to explain to the IETF community the horrible mistake to have multiple competing standards (we went down that road in the past and it was A HORRIBLE DISASTER) - that is why, at each level of the IETF, much attention has been paid to avoid this situation. I do not see why this is an exception to this very important principle. If the work in the potential WG will continue, ARE WE GOING TO RETIRE EXISTING STANDARDS ?

Message Format. The argument about ASN.1 vs JSON has to be re-framed in a TECHNICAL context instead of the not-so-appropriate argument "ASN.1 is evil". First off, either we talk about JSON SCHEMA vs. ASN.1 or we talk about JSON vs. DER. These are two completely different arguments. Since we are at IETF, let's focus on the "bits on the wire". It seems to me that the choice is quite clear: DER. The format is much more well defined, more compact, and has the required flexibility to accommodate for the required data structures. JSON makes sense in a JavaScript environment (JavaScript Object Notation) - but not much more outside that. JSON is thought to be readable by humans (by design) and has several limitations when it comes to encoding binary data (additional encoding is required) or non-ASCII names (again, additional encoding is required). In a JS environment where everything is UTF16, that is not an issue (if you ever worked in the space you would know that that is not really true for binary data encoding), but in this context the format has SERIOUS limitations that makes it a POOR format choice for the job. Moreover, considering the requirement for supporting DER as the STANDARDIZED format for ALL PKIX objects, it seems a very odd choice to require the use of yet-another-data-format (less efficient when it come to the bits on the wire) on top of what already exists and needs to be supported. Are we going to change all data formats to JSON ? If not, I do not think there are technical reasons to adopt an inferior (from a bits-on-the-wire perspective) than what we have and works today.

Weak Points in I-D. As I pointed out during the BoF, the problem to solve about providing automation for certificate management is discoverability of the services provided by a CA. In particular, I am referring to the fact that even if you convince a CA to adopt yet-another-format, there is no discussion about how the different CAs will be "discovered" - which ones support the new protocol ? The draft-barnes-acme-01 says:
" The ACME client presents the operator with a list of CAs from
      which it could get a certificate.
      (This list will change over time based on the capabilities of CAs
      and updates to ACME configuration.)  The ACME client might prompt
      the operator for payment information at this point."
This sentence makes sense only if it is referring to a specific piece of software - since the discoverability issue is not even mentioned, I assume that the authors of the software will have the power to DISCRIMINATE which CAs to support. Doesn't this seem NOT APPROPRIATE for a IETF wg ? Shouldn't there be a way to discover which CAs support which protocol ? If this problem was addressed first, there could be some ground for BEGINNING a discussion, but as it is written today, based just on this consideration, this document is a non-starter. Again, are we in the business of supporting a specific software? Moreover, how are the CAs identified ? By Name ? By the Hash of their certificates ? What trust is to be put in such a choice ? How stale can that information become ? Who is the authoritative information about what is supported by a vendor ?

Issued Certificates Trust Issues. Another important point is about what is the level of trust we want to achieve with the proposal and how this impacts the inclusion of CAs that support this protocol into standard trust stores (e.g., operating systems, browsers, MUAs, etc.) Since we have representatives from the browser's community (and I also hope from OSes), this is a question that needs to be addressed - would the adoption of this protocol be allowed for a Trusted CA ? Since there is no actual authentication of the requesting entity - the only level of certificates that can be issued is DV (and I have my doubts about that too). How is this better than current procedures from a trust perspective? Again, I know this is more of a POLICY related than technical issue - but these questions need an answer because the document itself oversteps the technical boundary, these are the type of discussions we also need to address.


Although I have always pushed for increasing the availability of certificates and the deployment of secure communications for almost 20yrs now, I do think that the proposed work is a non-starter for all the reasons I described above. I would like the whole community and the area directors to discuss the points above before proceeding any further.

This is Just my personal opinion. Sorry for the long e-mail.

Best Regards,
Massimiliano Pala, Ph.D.