Infrastructure System Engineering Group Y. Chen Internet-Draft Baidu Intended status: Informational April 17, 2020 Expires: October 17, 2020 Invisible Canonical Name Implementation draft-yaoyuan-dnsext-idr-adr-00 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. 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Chen Expires October 17, 2020 [Page 1] Internet-Draft Invisible Canonical Name Implementation April 2020 Abstract To accomplish the goal that not exposing redundant and unuseful CNAME chains in answers responded to clients, this document describes two new DNS resource records called "IDR" and "ADR" for hiding CNAME iterative process and better safety consideration. 1. Introduction The CNAME record presented in [RFC1034] and [RFC1035] nowadays is widely used to complete different functions. Simultaneously the record begins to show signs of weakness when helping engineers solve complex technical problems during increasingly complicated network environment. There are three fundamental flaws about CNAME and a scene which it cannot fit in: o Unnecessary and massive consumption of network bandwidth in traffic between clients and name resolvers if a chain with multi-CNAMEs is contained in answer section. Actually these CNAMEs are useless at all for clients. o The abuse of canonical names without authentication. Today we can easily configure a name redirected to a famous website without getting permission of the owner. Although website users with dns knowledge finally will know it is an alias after looking through the resolving process (someone not) and resource servers may take some security defence to deny illegal access, it still cause a tort about private intellectual property of real service providers. Maybe we can take some measures in dns layer. o CNAME chains in authoritative name servers MAY cause dns hijacking. As a name server will continue to find answers in internal cache, the upper servers could give answers those not equal to the real authoritative servers without validation. o In certain special circumstances or requirements, services providers closest to users side are not willing to present the intermediate process of the CNAMEs to customers. Certainly they MUST ask for permission of the original content administrators at first. To solve the above problems, we define two new DNS Resource Records with some extensions to current DNS rules.The changes are designed to be compatible with existing software. The existing support for CNAME and DNAME[RFC2672] is retained. Chen Expires October 17, 2020 [Page 2] Internet-Draft Invisible Canonical Name Implementation April 2020 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, [RFC2119]. 3. The "IDR" and "ADR" Resource Record IDR means "Invisible Direct Reference", it looks like a transparent agent who borrows resource records from others. The users cannot feel the agency process in detail. IDR means "Allow Direct Reference", which supplies a mechanism for safe references with permission. IDR and ADR have the following format: IDR: IDR ADR: ADR Like a normal record, all fields are required. The DATA field is a fully qualified [RFC1035] which MUST be in uncompressed form transferred in dns message. Both of records include a TTL value that represents the maximum time-to-live for a cached response in a resolver. IDR and ADR have the same behaviours as CNAME except the following features: o when a authoritative server deals with a query, return directly back to the asker when an IDR record is found rather than fall into deeply more queries process in its own name tree. o ADR is only used for authorization check and SHOULD not be included in answers when a resolver sends response packets to users. o When a resolver receives an IDR answer from a server, it MUST substitute the QNAME with IDR's and restart an additional query of QTYPE ADR. If the answer section includes the original QNAME(authentication passed), then the query process for original QTYPE can be continued. o Such kind of node as present in of IDL in answers MUST be removed if there is an IDR-ADR pair. Chen Expires October 17, 2020 [Page 3] Internet-Draft Invisible Canonical Name Implementation April 2020 The co-existence relationships among IDR/ADR and CNAME/DNAME: o IDR and ADR: YES o IDR and CNAME/DNAME: NO o ADR and CNAME/DNAME: YES o For each node and leaf on the tree-style domain name space, there MUST be at most one IDR record for each in the corresponding database, the number of ADR MUST not be limited. 4. Query Processing To complete the IDR/ADR mechanism the updating algorithms [RFC2136] and the name running algorithms [RFC1034][RFC2672] must be modified slightly for both servers and resolvers. 4.1. Processing By Primary Master Servers The following comparison rule SHOULD be added in the end of chapter 1.1.5. in [RFC2136]. IDL compare only NAME, CLASS, and TYPE -- it is not possible to have more than one IDL RR, even if their data fields differ. Meanwhile, ADLs SHOULD be allowed to co-exist with CNAME, DNAME, NS. 4.2. Processing By Authoritative Servers For a server performing non-recursive service steps 3.a and 5 of section 4.3.2 [RFC1034][RFC2672] are changed to check for a IDL record after checking for a CNAME type, and to make a pretreatment before packaging response message. DNS clients sending Extended DNS [EDNS0] queries with Version 0 or non-extended queries are presumed not to understand the semantics of the IDR/ADR record, so a server which implements this specification, when answering a non-extended query, SHOULD give out a CNAME record for each IDR record encountered during query processing to help the client reach the correct DNS data. The behaviour of clients and servers under Extended DNS versions greater than 0 will be specified when those versions are defined. Chen Expires October 17, 2020 [Page 4] Internet-Draft Invisible Canonical Name Implementation April 2020 The revised server algorithm is: 1. Set or clear the value of recursion available in the response depending on whether the name server is willing to provide recursive service. If recursive service is available and requested via the RD bit in the query, go to step 5, otherwise step 2. 2. Search the available zones for the zone which is the nearest ancestor to QNAME. If such a zone is found, go to step 3, otherwise step 4. 3. Start matching down, label by label, in the zone. The matching process can terminate several ways: a. If the whole of QNAME is matched, we have found the node. If the data at the node is a CNAME, and QTYPE doesn't match CNAME, copy the CNAME RR into the answer section of the response, change QNAME to the canonical name in the CNAME RR, and go back to step 1. Else if the data at the node is a IDL, and QTYPE doesn't match IDL, copy the IDL RR into the answer section of the response. If the query was not extended [EDNS0] with a Version indicating understanding of the IDL record, the server SHOULD make a substitution of CNAME for of RR already put in answer, then go back to step 6. The reason of not going back to step 1 is that it prevents the upper servers from hijacking dns data which SHOULD be responded by others who are authorized to answer. Otherwise, copy all RRs which match QTYPE into the answer section and go to step 6. b. If a match would take us out of the authoritative data, we have a referral. This happens when we encounter a node with NS RRs marking cuts along the bottom of a zone. Copy the NS RRs for the subzone into the authority section of the reply. Put whatever addresses are available into the additional section, using glue RRs if the addresses are not available from authoritative data or the cache. Go to step 4. Chen Expires October 17, 2020 [Page 5] Internet-Draft Invisible Canonical Name Implementation April 2020 c. If at some label, a match is impossible (i.e., the corresponding label does not exist), look to see whether the last label matched has a DNAME record. If a DNAME record exists at that point, copy that record into the answer section. If substitution of its for its in QNAME would overflow the legal size for a , set RCODE to YXDOMAIN and exit; otherwise perform the substitution and continue. If the query was not extended [EDNS0] with a Version indicating understanding of the DNAME record, the server SHOULD synthesize a CNAME record as described above and include it in the answer section. Go back to step 1. If there was no DNAME record, look to see if the "*" label exists. If the "*" label does not exist, check whether the name we are looking for is the original QNAME in the query or a name we have followed due to a CNAME. If the name is original, set an authoritative name error in the response and exit. Otherwise just exit. If the "*" label does exist, match RRs at that node against QTYPE. If any match, copy them into the answer section, but set the owner of the RR to be QNAME, and not the node with the "*" label. Go to step 6. 4. Start matching down in the cache. If QNAME is found in the cache, copy all RRs attached to it that match QTYPE into the answer section. If QNAME is not found in the cache but a DNAME record is present at an ancestor of QNAME, copy that DNAME record into the answer section. If there was no delegation from authoritative data, look for the best one from the cache, and put it in the authority section. Go to step 6. 5. Use the local resolver or a copy of its algorithm (see resolver section of this memo) to answer the query. Store the results, including any intermediate CNAMEs, DNAMEs in the answer section of the response, including two nodes which are connected by an IDL/ADL pair(not added) pointing to each other. 6. Using local data only, attempt to add other RRs which may be useful to the additional section of the query. Exit. Note that the IDLs SHOULD be also sent to clients with status "refused" if there are not corresponding ADLs found. Chen Expires October 17, 2020 [Page 6] Internet-Draft Invisible Canonical Name Implementation April 2020 4.3. Processing By Resolvers A resolver or a server providing recursive service MUST be modified to treat a IDL as somewhat analogous to a CNAME with some differences. The resolver algorithm of [RFC1034][RFC2672] section 5.3.3 is modified to renumber step 4.e as 4.f, 4.d as 4.e and insert a new 4.d. The complete algorithm becomes: 1. See if the answer is in local information, and if so return it to the client. 2. Find the best servers to ask. 3. Send them queries until one returns a response. 4. Analyze the response, either: a. if the response answers the question or contains a name error, cache the data as well as returning it back to the client. b. if the response contains a better delegation to other servers, cache the delegation information, and go to step 2. c. if the response shows a CNAME and that is not the answer itself, cache the CNAME, change the SNAME to the canonical name in the CNAME RR and go to step 1. d. if the response shows a IDL and that is not the answer itself, cache the IDL, preserve the original QNAME and QTYPE, change the QNAME with the in the IDL RR and restart an ADL query in local database or outside name servers. If returned results do not contain a ADL, terminate the process with RCODE refused. Else if one or more ADLs are found, cache them and judge if the original QNAME is included. If YES, change back to original QTYPE and go to step 1, else return the answer to the client with RCODE refused. e. if the response shows a DNAME and that is not the answer itself, cache the DNAME. If substitution of the DNAME's for its in the SNAME would overflow the legal size for a , return an implementation-dependent error to the application; otherwise perform the substitution and go to step 1. f. if the response shows a server failure or other bizarre contents, delete the server from the SLIST and go back to step 3. Chen Expires October 17, 2020 [Page 7] Internet-Draft Invisible Canonical Name Implementation April 2020 Before sending the records in answer section to the client, we MUST eliminate such kind of nodes which own this feature: the node is the in a IDL record, and it allows the to reference the records inside the node. In other words, the node has a IDL redirecting to another node which also has a ADL to authorize the jumping behaviour. 5. Examples of Use 5.1. Simple Mapping If the zone data for the FOO.EXAMPLE domain contains: WWW.FOO.EXAMPLE IDL WWW.BAR.EXAMPLE And the zone data for the BAR.EXAMPLE domain contains: WWW.BAR.EXAMPLE ADL WWW.FOO.EXAMPLE A 1.2.3.4 When a client send a query of type A for WWW.FOO.EXAMPLE, it will get a response as: WWW.FOO.EXAMPLE A 1.2.3.4 The client will not feel the existence of the intermediate node WWW.BAR.EXAMPLE when receiving answer from a resolver. We suggest a dns software which implements this specification could provide a method to present the detailed query process since it is convenient for operations staff to locate and solve problems related to dns. 5.2. Multilayer Mapping If dns name space includes the chain structure below: IDL IDL IDL IDL ------> ------> ------> ------> matched calss entrance node ---> N1 N2 N3 ... Nn ------> target <------ <------ <------ <------ matched type ADL ADL ADL ADL According to the processing rules, clients will only see the target in answer section with original QTYPE eventually. The nodes from N1 to Nn will be silently removed by resolvers when encoding the response packets. Chen Expires October 17, 2020 [Page 8] Internet-Draft Invisible Canonical Name Implementation April 2020 5.3. Interaction with CNAME If the zone data for the FOO.EXAMPLE domain contains: WWW.FOO.EXAMPLE CNAME WWW.BAR.EXAMPLE The zone data for the BAR.EXAMPLE domain contains: WWW.BAR.EXAMPLE IDL WWW.BAZ.EXAMPLE The zone data for the BAR.EXAMPLE domain contains: WWW.BAZ.EXAMPLE ADL WWW.BAR.EXAMPLE CNAME WWW.QUX.EXAMPLE And the zone data for the QUX.EXAMPLE domain contains: WWW.QUX.EXAMPLE A 1.2.3.4 When a client send a query of type A for WWW.FOO.EXAMPLE, it will get a response as: WWW.FOO.EXAMPLE CNAME WWW.BAR.EXAMPLE WWW.BAR.EXAMPLE CNAME WWW.QUX.EXAMPLE WWW.QUX.EXAMPLE A 1.2.3.4 5.4. Interaction with DNAME If the zone data for the FOO.EXAMPLE domain contains: WWW.FOO.EXAMPLE IDL WWW.FROBOZZ.EXAMPLE The zone data for the FROBOZZ.EXAMPLE domain contains: WWW.FROBOZZ.EXAMPLE ADL WWW.FOO.EXAMPLE FROBOZZ.EXAMPLE DNAME FROBOZZ-DIVISION.ACME.EXAMPLE The zone data for the ACME.EXAMPLE domain contains: WWW.FROBOZZ-DIVISION.ACME.EXAMPLE A 1.2.3.4 When a client send a query of type A for WWW.FOO.EXAMPLE, it will get a response as: WWW.FOO.EXAMPLE CNAME WWW.FROBOZZ-DIVISION.ACME.EXAMPLE WWW.FROBOZZ-DIVISION.ACME.EXAMPLE A 1.2.3.4 Chen Expires October 17, 2020 [Page 9] Internet-Draft Invisible Canonical Name Implementation April 2020 The ADL record MUST be arranged in the zone file of domain "FROBOZZ.EXAMPLE", otherwise it will meet a DNAME and terminate the query process because of the non-existance of ADL. The above examples are based on an extended recursive queries with EDNS over Version 0 from clients. 5.5. Handling queries with non-extended EDNS or EDNS with Version 0 When authoritative Servers see such a kind of query, they MUST treat IDL as a normal CNAME if exist. ADLs MUST be ignored and RCODE MUST be set to NXDOMAIN if there are not other kinds of records at all except ADLs inside the node. 6. Security Considerations The IDL/ADL records are similar to the CNAME record with regard to quoting resource records which have existed in other domains, differing in that the usage is safer than CNAME and do good to lighten pressure on network load. 7. IANA Considerations IANA may agree the allocation of these two records in the dns type registry if the specification is proved to be reasonable in the future. Chen Expires October 17, 2020 [Page 10] Internet-Draft Invisible Canonical Name Implementation April 2020 8. References [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, . [RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, November 1987, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound, "Dynamic Updates in the Domain Name System (DNS UPDATE)", RFC 2136, DOI 10.17487/RFC2136, April 1997, . [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC 2671, DOI 10.17487/RFC2671, August 1999, . [RFC2672] Crawford, M., "Non-Terminal DNS Name Redirection", RFC 2672, DOI 10.17487/RFC2672, August 1999, . Authors' Addresses Yaoyuan Chen Beijing Baidu Netcom Science Technology Co., Ltd No. 10 Shangdi 10th Street, Haidian District Beijing of China Phone: +86-18801393917 Email: chenyaoyuan@baidu.com Chen Expires October 17, 2020 [Page 11]