Change:
In most HTTPS transactions used by ACME, the ACME client is the HTTPS client and the ACME server is the HTTPS server.  The ACME server acts <del> as an HTTP and HTTPS client when validating challenges via HTTP. </del> <ins> as a client when validating challenges: an HTTP client when validating an 'http-01' challenge, a DNS client with 'dns-01', etc. </ins> ACME servers SHOULD follow the recommendations of RFC7525 when configuring their TLS implementations.  ACME servers that support TLS

Discussion:
URL URL
Looks good to me. I didn't necessarily expect the bit about de-provisioning a challenge response to need a SHOULD, but I don't object.
Thanks NAME With approval from co-author, chair, and AD, I guess it's safe to merge :)
So the de-provision isn't just editorial, but it is only a SHOULD. All of these look fine to me. LGTM :rocket: Thanks NAME Ben Campbell has entered the following ballot position for draft-ietf-acme-acme-14: Yes When responding, please keep the subject line intact and reply to all email addresses included in the To and CC lines. (Feel free to cut this introductory paragraph, however.) Please refer to URL for more information about IESG DISCUSS and COMMENT positions. The document, along with other ballot positions, can be found here: URL COMMENT: Thanks for the work on this; I'm happy to see it nearing completion. I have a few minor comments: Substantive : "The ACME server acts as an HTTP and HTTPS client when validating challenges via HTTP." Section 8.3 says that HTTP challenge validation cannot use HTTPS. Also, §6 says that all interactions between the client and server use HTTPS. I recognize challenge validation is not really an interaction between the client and server, but I suspect some readers may be confused. "ACME servers SHOULD follow the recommendations of [RFC7525] when configuring their TLS implementations." Why not MUST? : "... and the server MUST reject new-account requests that do not have the "termsOfServiceAgreed" field set to "true". " The MUST seems overly strong there; is there no room for local policy? Would it be completely insane to offer optional ToS? (For example, maybe one gets some additional service for agreeing to terms, but still gets a cert either way.) "Clients SHOULD NOT automatically agree to terms by default." Why not MUST NOT? : Is there a lifetime after which a provisioned HTTP resource in response to a challenge should go away? Editorial and Nits , first paragraph: Is the "user" the person requesting services from the ACME server? : " It is RECOMMENDED that the server perform DNS queries and make HTTP connections from various network perspectives..." : " The inner JWS is NOT REQUIRED to have a "nonce" header parameter."

"NOT REQUIRED" is not among the terms defined by 2119/8174. I suspect this is intended as a statement of fact, and should therefore not be capitalized. I'm not sure what that means. Given that this uses an upper-case RECOMMENDED, can it be stated more concretely? : Is this section also to be removed? Thanks for the work on this; I'm happy to see it nearing completion. I have a few minor comments:Section 8.3 says that HTTP challenge validation cannot use HTTPS. Also, §6 says that all interactions between the client and server use HTTPS. I recognize challenge validation is not really an interaction between the client and server, but I suspect some readers may be confused. Why not MUST? The MUST seems overly strong there; is there no room for local policy? Would it be completely insane to offer optional ToS? (For example, maybe one gets some additional service for agreeing to terms, but still gets a cert either way.) Why not MUST NOT? §2, first paragraph: Is the "user" the person requesting services from the ACME server? "NOT REQUIRED" is not among the terms defined by 2119/8174. I suspect this is intended as a statement of fact, and should therefore not be capitalized. I'm not sure what that means. Given that this uses an upper-case RECOMMENDED, can it be stated more concretely? §13.3: Is this section also to be removed?