Thank you for writing the draft. Please find my comments. I hope there are helpful. Yours, Daniel Special Use Domain 'home.arpa.' draft-ietf-homenet-dot-12 Abstract This document specifies the behavior that is expected from the Domain Name System with regard to DNS queries for names ending with '.home.arpa.', and designates this domain as a special-use domain name. 'home.arpa.' is designated for non-unique use in residential home networks. Home Networking Control Protocol (HNCP) is updated to use the 'home.arpa.' domain instead of '.home'. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: I would personally start by saying the document defines a special-use domain name and then defines the behavior. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on February 11, 2018. Copyright Notice Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of Pfister & Lemon Expires February 11, 2018 [Page 1] Internet-Draft dot homenet August 2017 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 3. General Guidance . . . . . . . . . . . . . . . . . . . . . . 3 4. Domain Name Reservation Considerations . . . . . . . . . . . 3 5. Updates to Home Networking Control Protocol . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 6 7. Delegation of 'home.arpa.' . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 10.1. Normative References . . . . . . . . . . . . . . . . . . 8 10.2. Informative References . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction Users and devices within a home network (hereafter "homenet") require devices and services to be identified by names that are unique within the boundaries of the homenet [RFC7368]. The naming mechanism needs to function without configuration from the user. While it may be possible for a name to be delegated by an ISP, homenets must also function in the absence of such a delegation. A default name with a scope limited to each individual homenet needs to be used. This document corrects an error in [RFC7788], replacing '.home' with 'home.arpa.' as the default domain-name for homenets. '.home' had been selected as the most user-friendly option. However, there are existing uses of '.home' that may be in conflict with this use: evidence indicates that '.home' queries frequently leak out and reach the root name servers [ICANN1] [ICANN2]. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: I believe that more important than the leak is that the introduction of .home in the root zone has been identified as highly risky. Another reason for not adopting it are also some uncertainty about its introduction into the root zone. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% In addition, it's necessary, for compatibility with DNSSEC (Section 6), that an insecure delegation ([RFC4035] section 4.3) be present for the name. There is an existing process for allocating names under '.arpa' [RFC3172]. No such process is available for requesting a similar delegation in the root at the request of the IETF, which does not administer that zone. As a result, the use of '.home' is deprecated. This document registers the domain '.home.arpa.' as a special-use domain name [RFC6761] and specifies the behavior that is expected from the Domain Name System with regard to DNS queries for names whose rightmost non-terminal labels are 'home.arpa.'. Queries for Pfister & Lemon Expires February 11, 2018 [Page 2] Internet-Draft dot homenet August 2017 names ending with '.home.arpa.' are of local significance within the scope of a homenet, meaning that identical queries will result in different results from one homenet to another. In other words, a name ending in 'home.arpa.' is not globally unique. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: I think the text mentioned in the beginning of the paragraph above should be in the abstract. That was the sense of my previous comment. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Although this document makes specific reference to RFC7788, it is not intended that the use of 'home.arpa.' be restricted solely to networks where HNCP is deployed; it is rather the case that 'home.arpa.' is the correct domain for uses like the one described for '.home' in RFC7788: local name service in residential homenets. 2. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 3. General Guidance The domain name '.home.arpa.' is to be used for naming within residential homenets. Names ending with '.home.arpa.' reference a locally-served zone, the contents of which are unique only to a particular homenet, and are not globally unique. Such names refer to nodes and/or services that are located within a homenet (e.g., a printer, or a toaster). DNS queries for names ending with '.home.arpa.' are resolved using local resolvers on the homenet. Such queries MUST NOT be recursively forwarded to servers outside the logical boundaries of the homenet. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: "local resolvers" seems to me mis-leading. Your resolver may be local but still forward the query to the Global Internet. I do not see better ways to say it other than inside the boundaries of the homenet. Maybe we could say: DNS queries for names ending with '.home.arpa.' are resolved using homenet specific resolution mechanisms. Eventually an informational reference to the simple naming architecture may be added so the reader can refer to the doc for further information. For full disclosure Ted and I are co-authors. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Some service discovery user interfaces that are expected to be used on homenets conceal information such as domain names from end users. However, it is still expected that in some cases, users will need to see, remember, and even type, names ending with 'home.arpa.'. It is therefore desirable that users identify the domain and understand that using it expresses the intention to connect to a service that is specific to the homenet to which they are connected. Enforcing the fulfillment of this intention is out of scope for this document. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: I have difficulties understanding the paragraph above. If the idea is to say home.arpa has special meaning that should be considered by GUIs I would propose the following ordering. It is therefore desirable that users identify the domain and understand that using it expresses the intention to connect to a service that is specific to the homenet to which they are connected. Some service discovery user interfaces that are expected to be used on homenets conceal information such as domain names from end users. However, it is still expected that in some cases, users will need to see, remember, and even type, names ending with 'home.arpa.'. Enforcing the fulfillment of this intention is out of scope for this document. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 4. Domain Name Reservation Considerations This section defines the behavior of systems involved in domain name resolution when resolving queries for names ending with '.home.arpa.' (as per [RFC6761]). Pfister & Lemon Expires February 11, 2018 [Page 3] Internet-Draft dot homenet August 2017 1. Users can use names ending with '.home.arpa.' just as they would use any other domain name. The 'home.arpa.' name is chosen to be readily recognized by users as signifying that the name is addressing a service on the homenet to which the user's device is connected. 2. Application software SHOULD NOT treat names ending in 'home.arpa.' differently than other names. In particular, there is no basis for trusting names that are subdomains of 'home.arpa.' (see Section 6). %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: a domain name ending in home.arpa may be resolved differently that a regular domain name. As a result a different treatment is applied. I think that "treat" means that no special meaning - other that the domain name is inside the homenet boundaries - should be associated to a home.arpa. If I am correct I would limit the consideration to the name rather then the application. I would suggest the text below: names ending in home.arpa SHOULD NOT be associated any other properties than the affiliation to the homenet. In particular, there is no basis for trusting names that are subdomains of 'home.arpa.' (see Section 6). %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 3. Name resolution APIs and libraries MUST NOT recognize names that end in '.home.arpa.' as special and MUST NOT treat them differently. Name resolution APIs MUST send queries for such names to a recursive DNS server that is configured to be authoritative for the 'home.arpa.' zone appropriate to the homenet. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: I believe the text below does not concern the library but the resolver. It is different to say libraries MUST NOT have specific considerations for home.arpa than a resolution service that may use different libraries MUST NOT consider the home.arpa differently. My understanding of the text below is that the resolver and the authoritative server for the home.arpa MUST be co-located. The reasons I think this is not exact is that resolution for home.arpa can also be provided by other mechanisms than an authoritative server. Typically, resolution can be done by requesting Authoritative Servers, Advertising Proxies, Hybrid Proxies (now called Discovery Proxies).... The other reason is do not see the text below accurate is that you may have a DNS Proxy that transparently to the end user split the resolution between homenet specific resolutions when home.arpa is encountered while other names are sent to the ISP resolver. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% One or more IP addresses for recursive DNS servers will usually be supplied to the client through router advertisements or DHCP. If a host is configured to use a resolver other than one that is authoritative for the appropriate 'home.arpa.' zone, the client may be unable to resolve, or may receive incorrect results for, names in sub domains of 'home.arpa.'. 4. Caching resolvers conforming to this specification MUST support DNSSEC queries. While validation is not required, it is strongly encouraged; a caching resolver that does not validate answers that can be validated may cache invalid data; this will prevent validating stub resolvers from successfully validating answers. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: I see the text above as a recommendation for caching resolvers in the homenet, but the relation to the home.arpa is unclear to me. Was the intention to say that names under the home.arpa zone SHOULD be secured with DNSSEC so caching resolvers MUST support DNSSEC validation. In addition, these caching resolvers MUST also be able to be configured with a Trust Anchor for the home.arpa. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Unless configured otherwise, recursive resolvers and DNS proxies MUST behave as described in Locally Served Zones ([RFC6303] Section 3). That is, queries for domains that are subdomains of 'home.arpa.' MUST NOT be forwarded, with one important exception: a query for a DS record when the DO bit ([RFC4035] section 3.2.1) set MUST return the correct answer for that question, including correct information in the authority section that proves that the record is nonexistent. So for example a query for the NS record for 'home.arpa.' MUST NOT result in that query being forwarded to an upstream cache nor to the authoritative DNS server for '.arpa.'. However, as necessary to provide accurate authority information, a query for the DS record MUST result in whatever queries are necessary being forwarded; typically, this will just be a query for the DS record, since the necessary authority information will be included in the authority section of the response if the DO bit is set. Pfister & Lemon Expires February 11, 2018 [Page 4] Internet-Draft dot homenet August 2017 In addition to the behavior specified above, recursive resolvers that can be used in a homenet MUST be configurable with a delegation to an authoritative server for that particular homenet's instance of the domain 'home.arpa.'. It is permissible to combine the recursive resolver function for general DNS lookups with an authoritative resolver for 'home.arpa.'; in this case, rather than forwarding queries for subdomains of 'home.arpa.' to an authoritative server, the caching resolver answers them authoritatively. The behavior with respect to forwarding queries specifically for 'home.arpa.' remains the same. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: The full consideration seems to me to be conformance to RFC6303. In particular the recommendations for DNSSEC in RFC 6303 seems to me accurated and are not specifically mentioned here. Maybe that should be clearly stated that all considerations of RFC6303 should be considered as home.arpa is of local scope. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 5. No special processing of 'home.arpa.' is required for authoritative DNS server implementations. It is possible that an authoritative DNS server might attempt to check the authoritative servers for 'home.arpa.' for a delegation beneath that name before answering authoritatively for such a delegated name. In such a case, because the name always has only local significance there will be no such delegation in the 'home.arpa.' zone, and so the server would refuse to answer authoritatively for such a zone. A server that implements this sort of check MUST be configurable so that either it does not do this check for the 'home.arpa.' domain, or it ignores the results of the check. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: I understand this as being incorrect. The resolver can also be configured with a trust anchor. I would refer to the RFC6303: As DNSSEC is deployed within the IN-ADDR.ARPA and IP6.ARPA namespaces, the zones listed above will need to be delegated as insecure delegations, or be within insecure zones. This will allow DNSSEC validation to succeed for queries in these spaces despite not being answered from the delegated servers. It is recommended that sites actively using these namespaces secure them using DNSSEC [RFC4035] by publishing and using DNSSEC trust anchors. This will protect the clients from accidental import of unsigned responses from the Internet. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 6. DNS server operators MAY configure an authoritative server for 'home.arpa.' for use in homenets and other home networks. The operator for the DNS servers authoritative for 'home.arpa.' in the global DNS will configure any such servers as described in Section 7. 7. 'home.arpa.' is a subdomain of the 'arpa' top-level domain, which is operated by IANA under the authority of the Internet Architecture Board according to the rules established in [RFC3172]. There are no other registrars for .arpa. 5. Updates to Home Networking Control Protocol The final paragraph of Home Networking Control Protocol [RFC7788], section 8, is updated as follows: OLD: Names and unqualified zones are used in an HNCP network to provide naming and service discovery with local significance. A network- wide zone is appended to all single labels or unqualified zones in order to qualify them. ".home" is the default; however, an administrator MAY configure the announcement of a Domain-Name TLV Pfister & Lemon Expires February 11, 2018 [Page 5] Internet-Draft dot homenet August 2017 (Section 10.6) for the network to use a different one. In case multiple are announced, the domain of the node with the greatest node identifier takes precedence. NEW: Names and unqualified zones are used in an HNCP network to provide naming and service discovery with local significance. A network- wide zone is appended to all single labels or unqualified zones in order to qualify them. 'home.arpa.' is the default; however, an administrator MAY configure the announcement of a Domain-Name TLV (Section 10.6) for the network to use a different one. In case multiple are announced, the domain of the node with the greatest node identifier takes precedence. The 'home.arpa.' special-use name does not require a special resolution protocol. Names for which the rightmost two labels are 'home.arpa.' are resolved using the DNS protocol [RFC1035]. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: If home.arpa are no different than other resolutions and we start from the root zone responses are likely to be NXDOMAIN. I think we should clarify that DNS is used as a transport protocol, but that resolution may be handled differently. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 6. Security Considerations A DNS record that is returned as a response to a query for an FQDN in the domain '.home.arpa.' is expected to have local significance. It is expected to be returned by a server involved in name resolution for the homenet the device is connected in. However, such response MUST NOT be considered more trustworthy than would be a similar response for any other DNS query. Because 'home.arpa.' is not globally scoped and cannot be secured using DNSSEC based on the root domain's trust anchor, there is no way to tell, using a standard DNS query, in which homenet scope an answer belongs. Consequently, users may experience surprising results with such names when roaming to different homenets. To prevent this from happening, it may be useful for the resolver to identify different homenets on which it has resolved names, but this is out of scope for this document. It is not possible to install a trust anchor for this zone in the '.arpa' zone. The reason for this is that in order to do so, it would be necessary to have the key-signing key for the zone ([RFC4034] Section 5). Since the zone is not globally unique, no one key would work. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: I think that DS is meant rather than trust anchor. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% An alternative would be to install a authenticated denial of existence ([RFC4033] Section 3.2). %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: This is unclear where the denial of existence is set. Is that in the home.arpa zone or the arpa zone. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% However, this assumes that validation is being done on a caching resolver that is aware of the special local meaning of 'home.arpa.'. If a host stub resolver attempts to validate a name in 'home.arpa.', an authenticated denial Pfister & Lemon Expires February 11, 2018 [Page 6] Internet-Draft dot homenet August 2017 of existence of 'home' as a subdomain of 'arpa.' would cause the validation to fail. Therefore, the only delegation that will allow names under 'home.arpa.' to be resolved is an insecure delegation, as in [RFC6303] section 7. Consequently, unless a trust anchor for the particular instance of the 'home.arpa.' zone being validated is manually configured on the validating resolver, DNSSEC signing of names within the 'home.arpa.' zone is not possible. Although in principle it might be useful to install a trust anchor for a particular instance of 'home.arpa.', it's reasonable to expect that a host with such a trust anchor might from time to time connect to more than one network with its own instance of 'home.arpa.'. Such a host would be unable to access services on any instance of 'home.arpa.' other than the one for which a trust anchor was configured. It is in principle possible to attach an identifier to an instance of 'home.arpa.' that could be used to identify which trust anchor to rely on for validating names in that particular instance. However, the security implications of this are complicated, and such a mechanism, as well as a discussion of those implications, is out of scope for this document. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: There are also some privacy issues associated to leaking names outside the homenet boundaries. For example daniel_smith.home.arpa reveal the identity of the member of the homenet, my_ipad.home.arpa reveals the devices you own, the application. home.arpa may also used in larger environment such as corporate / private. going from one to the other may also leak such information. The leak can be from the homenet to the outside world in which case one neeed to control the queries sent. But in intruder (or guest) may also access the homenet and proceed to discovery of the names. As a result even though homenet is believe to be a trusted environment, care should be considered while publishing under the home.arpa. as well as whose the information is accessible to. They might be collision as well. myprinter.home.arpa may be found in various environments, and upon discovery you may also - in this example - print confidential information to that printer. In some case you may not even be aware, for example, if your printing information failed home, and is re-activated once you are in another environment. As information may be sensitive it may be encrypted using IPsec DTLS as described by dprive for both authentication and confidentiality. When the trust anchor is configured in the resolver, these must be able to roll-over the key and should follows the requirements for DNSSEC validators. if it is impossible for a resolver to see the difference between an attack and a re-key we are in trouble. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 7. Delegation of 'home.arpa.' In order to be fully functional, there must be a delegation of 'home.arpa.' in the '.arpa.' zone [RFC3172]. This delegation MUST NOT include a DS record, and MUST point to one or more black hole servers, for example 'blackhole-1.iana.org.' and 'blackhole- 2.iana.org.'. The reason that this delegation must not be signed is that not signing the delegation breaks the DNSSEC chain of trust, which prevents a validating stub resolver from rejecting names published under 'home.arpa.' on a homenet name server. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: The zone home.arpa MUST NOT be seen as belonging to the homenet. As a result, NS and DS records for home.arpa does not have meanings outside a specific domain. A Public server outside the boundaries of the homenet MUST consider this traffic as irrelevant and sink. Redirection to as112 without coordination with as112 operator may rather be performed using DNAME. I believe more text should document the two alternative. With the proposed configuration, the query will be directed to a server that is not authoritative for the zone. The response is likely to be REFUSED, while in the other case it is likely to be NXDOMAIN. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 8. IANA Considerations IANA is requested to record the domain name 'home.arpa.' in the Special-Use Domain Names registry [SUDN]. IANA is requested, with the approval of IAB, to implement the delegation requested in Section 7. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% MGLT: OK if IANA may make the direct way work. In that case is there any need to update a registry for zone served by as112? %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%