Internet Engineering Task Force (IETF) Phillip Hallam-Baker Internet-Draft Comodo Group Inc. Intended Status: Standards Track March 21, 2014 Expires: September 22, 2014 Private-DNS draft-hallambaker-dnse-00 Abstract This document describes DNSE-JX, a transport security mechanism for the DNS protocol. The mechanism may be employed to secure communication between a client and its resolver or between a resolver and an authoritative server. Service binding including key exchange is effected using the JSON Service Connect (JCX) Protocol. DNS protocol messages are wrapped in a new framing protocol. Deployment of the new security mechanism compliments DNSSEC. 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." Copyright Notice Copyright (c) 2014 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 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Hallam-Baker September 22, 2014 [Page 1] Internet-Draft Private-DNS March 2014 Table of Contents 1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Related Work . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.3. Defined Terms . . . . . . . . . . . . . . . . . . . . . . 3 2. Use Cases and Requirements . . . . . . . . . . . . . . . . . . 4 2.1. Core Use Cases . . . . . . . . . . . . . . . . . . . . . 4 2.1.1. Client/Resolver Communications . . . . . . . . . . . 5 2.1.2. Resolver/Authoritative Communications . . . . . . . 7 2.2. Constraints . . . . . . . . . . . . . . . . . . . . . . . 8 2.2.1. Legacy Deployment . . . . . . . . . . . . . . . . . 8 2.2.2. Integrity Attacks . . . . . . . . . . . . . . . . . 8 2.2.3. Limited message size . . . . . . . . . . . . . . . . 8 2.3. Requirements . . . . . . . . . . . . . . . . . . . . . . 8 2.3.1. Confidentiality Requirements . . . . . . . . . . . . 9 2.3.2. Integrity Requirements . . . . . . . . . . . . . . . 9 2.3.3. Access Requirements . . . . . . . . . . . . . . . . 9 3. Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.1. Service Connection . . . . . . . . . . . . . . . . . . . 10 3.2. DNS Message Encapsulation . . . . . . . . . . . . . . . . 11 3.3. Satisfaction of Requirements . . . . . . . . . . . . . . 12 4. Service Connection and Key Exchange . . . . . . . . . . . . . 12 5. DNS Message Encapsulation . . . . . . . . . . . . . . . . . . 13 5.1. Request . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.2. Response . . . . . . . . . . . . . . . . . . . . . . . . 14 5.3. Payload . . . . . . . . . . . . . . . . . . . . . . . . . 15 6. Security Considerations . . . . . . . . . . . . . . . . . . . 15 6.1. Service . . . . . . . . . . . . . . . . . . . . . . . . . 16 6.2. Confidentialityty . . . . . . . . . . . . . . . . . . . . 16 6.3. Integrity . . . . . . . . . . . . . . . . . . . . . . . . 16 6.4. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 16 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 8. Acnowledgementsts . . . . . . . . . . . . . . . . . . . . . . 16 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 9.1. Normative References . . . . . . . . . . . . . . . . . . 16 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 17 Hallam-Baker September 22, 2014 [Page 2] Internet-Draft Private-DNS March 2014 1. Introduction. Recent events have required urgent consideration of privacy concerns in Internet protocols. In particular the lack of confidentiality controls in the DNS [RFC1035] protocol is of considerable concern. This document illustrates the privacy and related concerns raised with a set of use cases which in turn give rise to a set of requirements. Private-DNS, a security enhancement for the DNS protocol is then proposed to meet the stated set of requirements. This enhancement provides for encryption and authentication of the DNS protocol messages. Private-DNS makes use of the JSON Service Connect (JCX) Protocol [I- D.hallambaker-wsconnect] and introduces a new framing protocol. 1.1. Related Work The proposal approach compliments the integrity controls provided by DNSSEC [RFC4033]. While both provide integrity controls, the controls provided by DNSSEC are based on digital signatures while this proposal provides controls based on a Message Authentica Code technique. Like the Omnibroker protocol [I-D.hallambaker-omnibroker], this proposal is built on JCX [I-D.hallambaker-wsconnect] but offers a low level interface to the DNS protocol alone as opposed to a high level interface to generalized discovery services. A client would use the DNSE-JX interface in cases where retrieval of specific DNS resource records is required. The OmniBroker protocol would be used in cases where the client delegates the choice of discovery strategy to the OmniBroker service. 1.2. Terminology The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this document, are to be interpreted as described in [RFC2119] 1.3. Defined Terms [[These terms are deliberately left blank here or else we will spend time wordsmithing the defined term definitions rather than looking at the protocol.] Hallam-Baker September 22, 2014 [Page 3] Internet-Draft Private-DNS March 2014 Authoritative DNS Server Caching Recursive Resolver DNS DNS Client Recursive Resolver Stub Resolver 2. Use Cases and Requirements The immediate motivation for considering a DNS transport layer security protocol is the desire to improve the privacy of Internet communications by allowing encryption of DNS requests and responses. Since any encryption protocol mustby its very nature require changes to both the sender and receiver of a message, any such change is necessarily backwards incompatible. Accordingly we consider two sets of use cases: * Use cases that illustrate aspects of the immediate concern of protecting privacy of DNS protocol messages. * Use cases that illustrate other concerns that might be usefully addressed in any major revision of the DNS protocol. 2.1. Core Use Cases The DNS is the Internet infrastructure that makes authoritative statements about DNS names. In particular the DNS is used to support discovery of Internet services by mapping DNS names onto IP addresses. In the conventional configuration, a client requiring information from the DNS does not access DNS authoritative servers directly and instead makes requests through a resolver. The resolver in turn determines which requests to make to answer the query and forwards the request to the authoritative server. +-------------+ +-------------+ +-------------+ | Client |--->| Resolver |--->|Authoritative| +-------------+ +-------------+ +-------------+ Due to the distributed and hierarchical nature of the DNS, answering a DNS query typically requires queries to multiple Authoritative servers. This process is known as Recursive Resolution of the DNS Query. In the typical configuration the Resolver is a 'Caching Recursive Resolver' capable of making Recursive Queries and caching Hallam-Baker September 22, 2014 [Page 4] Internet-Draft Private-DNS March 2014 the result to answer future queries. The client is typically a 'Stub Client' that is not capable of making recursive queries itself and must rely on a Recursive Resolver to do this for it. One of the major security weaknesses in the DNS infrastructure as currently deployed is that by default most Internet enabled devices accept DNS service from the servers offered to it by DHCP when a connection is established. Since the DNS is a naming service and thus a trusted service, DNS services SHOULD be trustworthy. The practice of relying on a the 'local' DNS resolver advertised in the DHCP connection is therefore highly unsatisfactory. In real world circumstances this configuration is further complicated by firewalls, NAT devices and other middleboxes. Many of which filter or in some cases modify DNS protocol packets whether or not they are addressed to that device. For the purposes of considering the privacy of the DNS protocol, there are two important protocol interactions to consider: * Communications between a Client and a Resolver * Communications between a Resolver and an Authoritative Server The DNS protocol supports both modes of interaction without special provision for either case. From a security point of view, the two interactions have different characteristics and give rise to different use cases. 2.1.1. Client/Resolver Communications Communications between the client and the resolver reveal a lot of privacy sensitive information about the user. A DNS query for the address of a controversial Web Site indicates with high probability that a user is viewing material from the site. In the typical configuration a DNS client makes use of the DNS resolution server(s) advertised by DHCP when a network configuration is established or server(s) that are configured manually by an administrator. In either case the relationship between the client and the resolver is at minimum persistent for the length of time the network association is active. In the case that the DNS service is selected and confinugred manually, the security relationship might last for years or the entire life of the device. Hallam-Baker September 22, 2014 [Page 5] Internet-Draft Private-DNS March 2014 2.1.1.1. Local Resolver For the sake of completeness, we state the case in which a client obtains DNS service from a local DNS server advertised at the time the network connection is established as a use case. Note however that the privacy concerns that can be protected in such circumstances are necessarily limited as the user has no idea where the service is being provided from. [U-LOCAL]: User connects to untrusted local network and wishes to use the locally provided DNS service. While a user may not intend to use the local DNS service, there are many real world network configurations that attempt to impose this on the user for a variety of reasons. In particular hotels and other providers of local wireless Internet often make use of a 'captive DNS resolver' to direct users to a portal for a variety of business purposes that include limiting use of the wireless network to particular parties. While it is clearly impossible to provide robust privacy protections to users who accept core network functions from random untrustworthy sources, the ability to establish network connections in such circumstances is essential. 2.1.1.2. Selected Public Resolver A public resolver allows users to avoid the numerous security vulnerabilities inherent in the local resolver model. Instead of taking trusted services from random, anonymous providers, the user selects a particular DNS resolution provider to be used regardless of which network is in use. Many Public DNS resolution services are for-profit commercial ventures. The business models supporting such services include advertising and data-mining the DNS log file data. [[U-PUBLIC] The user takes DNS resolution service from a selected provider offering a public DNS resolution service. 2.1.1.3. Selected Subscriber Resolver In an alternative business model the DNS resolution service is visible to the public Internet but only answers requests from paying subscribers. While such a service might not be considered sufficiently attractive for it to be offered as a stand-alone service, an ISP or security provider might offer a privacy enhanced DNS as part of a more general offering. Hallam-Baker September 22, 2014 [Page 6] Internet-Draft Private-DNS March 2014 [[U-SUBSCRIBER] The user takes DNS resolution service from a selected provider offering the service on a subscription model of some form. 2.1.1.4. Selected Private Resolver Most medium to large enterprises run their own DNS services as part of their trusted network infrastructure. Although the DNS is conceptually a single uniform namespace, many Internet sites regard the DNS names of their internal network machines to be secret. Protecting the secrecy of such names being one of the principle attractions of a DNS privacy protocol to such enterprises. this leads to the widespread use of 'split-horizon' DNS in which different views of the DNS namespace are visible depending on whether a machine is inside or outside the enterprise. [U-PRIVATE] A device takes DNS resolution service from a private service restricted to authorized use. 2.1.1.5. Hybrid Resolver To reduce equipment costs and in response to employee demand, many enterprises now support a Bring Your Own Device (BYOD) model in which a device that is the property of the owner. Such a device requires access to a private DNS service to access enterprise resources within a hidden split-horizon DNS. But the owner might not wish their private use of the device to be visible to their employer. [U-HYBRID] A user makes use of different DNS resolution services for different portions of the DNS namespace. 2.1.2. Resolver/Authoritative Communications Communications between a Resolver and an Authoritative Server can also leak privacy sensitive data. Such leakage is mitigated at resolvers with a large number of users and a high traffic load. Unlike clients which typically direct DNS requests to a single resolver or a small number of resolvers, resolvers typically interact with a large number of authoritative servers. Some of which service a large number of DNS domains and others service are restricted to a publishing data for a specific enterprise. Although these use cases are not distinguished in the DNS protocol, the privacy implications and protocol constraints of interactions with the two types of server are very different. Any interaction between a resolver and an authoritative server that responds to requests for a single domain with a single host effectively discloses the nature of the request regardless of whether encryption is used. At the other extreme, traffic analysis of interactions with authoritative services serving a large number of domains revealls Hallam-Baker September 22, 2014 [Page 7] Internet-Draft Private-DNS March 2014 much less. [U-A-BULK] Interaction between a resolver and an authoritative server supporting a large number of domains. [U-A-TAIL] Interaction between a resolver and an authoritative server supporting a small number of domains such that the interaction is effectively disclosure of the nature of the communication. 2.2. Constraints Any proposal to address the use cases must operate within the constraints set by existing DNS infrastructure and administration practices. 2.2.1. Legacy Deployment The DNS protocol specification was first published in 1987 and has evolved significantly over time. While the vast majority of deployed DNS servers support modern features such as EDN(0) and DNSSEC, many do not. Likewise, most DNS clients and servers accept messages longer than the 500 byte minimum implementation requirement. Regretably, while most DNS clients and servers are capable of supporting features introduced since [RFC1035], many middle-box devices including firewalls and residential network gateway devices do not. 2.2.2. Integrity Attacks One of the core security vulnerabilities of the original DNS protocol is that responses are only weakly bound to requests, thus enabling an attack known as 'DNS-Spoofing'. While DNSSEC is intended to provide a long term solution to the problem of DNS spoofing, deployment of DNSSEC is currently the rare exception rather than the rule. 2.2.3. Limited message size One of the chief performance limitations of the DNS as currently deployed is that most DNS servers will only accept a single request per DNS message. Th despite support for multiple queries in a single request in the DNS protocol, Hallam-Baker September 22, 2014 [Page 8] Internet-Draft Private-DNS March 2014 2.3. Requirements The use cases set out above give rise to the following requirements. the term 'requirement' is used to refer to protocol features that might be considered desirable without taking a position as to whether they are necessary or desirable in practice. A proposal that is simpler or more performant may be considered to be superior to one that satisfies every requirement. 2.3.1. Confidentiality Requirements [R-C-PASSIVE] Protect the confidentiality of request and response data against a passive attacker. [R-C-AFIRST] Protect the confidentiality of request and response data against an active attacker after first contact. [R-C-ACTIVE] Protect the confidentiality of request and response data against an active attacker on every contact. [R-C-TRAFFIC] Protect the contents of messages from being disclosed by an external attacker through traffic analysis. [R-C-LINKING] Protect the client against profiling by the resolver. [R-C-ATHOR] Protect the confidentiality of messages against profiling by authoritative servers. 2.3.2. Integrity Requirements [R-PSPOOF] Prevent spoofing of DNS responses by passive attack [R-ASPOOF] Prevent spoofing of DNS responses by active attack 2.3.3. Access Requirements [R-CANON] Support anonymous access to a DNS resolution service Hallam-Baker September 22, 2014 [Page 9] Internet-Draft Private-DNS March 2014 [R-CAUTH] Support authentication of the client requesting access to a DNS resolution service [R-AMP] Prevent Message amplification attack [R-DDOS] Prevent Denial of Service attack on the service Note that [[R-CANON] and [[RCAUTH] are mutually exclusive. While it is desirable for a solution to be capable of supporting both it is not possible for a request to be anonymous and authenticated at the same time by definition. The access requirement [[RCAUTH] is also distinct from the spoofing countermeasure requirements [R-PSPOOF] and [R-ASPOOF]. The access requirement [[RCAUTH] requires that the service identify the source of a request. The anti-spoofing requirements require that responses be authenticated against the requests made. 3. Architecture PRIVATE-DNS has two parts * Service Connection * DNS message encapsulation In PRIVATE-DNS, the service connection is provided by the existing [I-D.hallambaker-wsconnect] proposal. The DNS message encapsulation is new and supports encryption and authentication of the DNS protocol messages. To make use of PRIVATE-DNS a client first establishes a connection to a DNS server (resolver or authoritative) using the connection protocol. Once a client has established a connection it MAY use it to make as many queries as desired until either the connection context expires or is cancelled by the service. The Service Connection and Query Service MAY be operated on the same host or on separate hosts. 3.1. Service Connection The service connection mechanism is responsible for establishing a connection context between a client and a service. The connection context comprises: * A security context (opaque identifier, key, algorithm choice) between the client and the connection service Hallam-Baker September 22, 2014 [Page 10] Internet-Draft Private-DNS March 2014 * One or more query host connection contexts, each comprisingNetwork connection description (IP address, Port, Protocol, transport)Security Context (opaque identifier, key, algorithm choice) between the client and the query host The PRIVATE-DNS proposal is designed on the assumption that Service Connection transactions are relatively infrequent and thus the efficiency of the Service Connection protocol is not a major concern. Accordingly the Service Connection protocol is implemented as a JSON/REST Web Service over HTTP. While of an efficient encoding (e.g. [I-D.hallambaker-jsonbcd] would permit a more efficient implementation of the protocol using UDP, such an approach would be vulnerable to Denial of Service attacks against the service unless appropriate countermeasures were taken. For example use of a 'cookie' approach to prove the validity of the purported request source address. A service connection MAY return a host connection set that includes multiple protocol and/or transport options. This has the important consequence that it allows new message formats or a transition to an entirely new protocol to be effected by simply defining a new identifier. A distinction is drawn between a connection to a service and a connection to a host. A connection to a host is a relationship to a specific instance of a service with a distinct IP address. A connection to a service is a relationship to a set of hosts. This distinction is an important one for Denial of Service mitigation. A DNS service need not publish the same network connection description to every client. This permits a service to mitigate DoS attacks by filtering query requests by IP address, a strategy that is greatly enhanced by the large address space of IPv6. Different configurations of the Service Connection service allow a DNS service to meet different combinations of security requirements. For example the Public Resolver described in [U-PUBLIC] would not require authentication of the client to the service but this would be required for the Subscriber, Private and Hybrid Resolvers described in [U-SUBSCRIBER], [[U-PRIVATE] and [[U-HYBRID].]. 3.2. DNS Message Encapsulation The DNS Query Encapsulation is designed for efficiency and to support the following features * Encryption * Authentication * Multiple DNS queries and responses per PRIVATE-DNS Query [[*] Hallam-Baker September 22, 2014 [Page 11] Internet-Draft Private-DNS March 2014 * Multiple packet responses [[*] The features marked [[*] are not essential for the purpose of meeting the privacy requirements but considerably improve the efficiency and flexibility of the DNS protocol. In particular the ability to make multiple DNS queries in a single transaction enables the use of novel discovery techniques without impact on performance. Choice of encoding scheme is notoriously open to differences without distinctions (aka bikeshedding). Fortunately this is a decision that the Service Connection service makes easy to revisit. Accordingly this specification only describes the information to be put in the massages rather than the messages themselves. The principle design choice to be made is between a tagged data format (e.g. JSON) and a position based format (e.g. the format used in TLS). A tagged format offers greater flexibility while a position based format is more efficient. At present the TLS position based approach is prefered since this is compatible with the traditional approach in DNS. 3.3. Satisfaction of Requirements [[TBS go through each requirement and show that it is satisfied or satisfiable by a particular configuration.] 4. Service Connection and Key Exchange The Service Connection is established using [I-D.hallambaker- wsconnect]. The protocol identifiers for PRIVATE-DNS are as follows: Service Identifier PRIVATE-DNS Protocol DNS Presentation PRIVATE-DNS-P Transport UDP Under certain network conditions attempts to reach the PRIVATE-DNS service may fail due to constraints imposed by firewalls or through attempted censorship. Under these conditions, HTTP [RFC2616] MAY be used as an alternative transport as follows: Hallam-Baker September 22, 2014 [Page 12] Internet-Draft Private-DNS March 2014 Protocol DNS Presentation POST Transport HTTP A PRIVATE-DNS service offered in this fashion MUST support HTTP/1.1 or higher. 5. DNS Message Encapsulation The DNS Message Encapsulation format is described using the format desribed in [RFC5246]. Note that in this notation the size of a length specifier is defined by the maximum number of octets permitted in the corresponding data field. For convenience these sizes are given as 255 or 65335 to specify 1 and 2 byte length specifiers respectively. The actual length of the data fields that can be used in practice will depend on the maximum size of UDP packet that can be reliably transmitted. Note that the omission of version numbers in the on-the-wire data structures is intentional. Use of the message encapsulation requires that the parties have previously established a host connection comprising the network and security parameters required to communicate. The choice of message encapsulation including the protocol version is defined in the host connection. In the DNS protocol requests and responses use the same message structure. The encapsulation uses different structures for requests and responses but the payload of each structure is a sequence of [RFC1035] messages. opaque TransactionID<16..255> opaque SecurityContextID<1..255> 5.1. Request If the UDP transport is in use, a request consists of exactly one packet. Hallam-Baker September 22, 2014 [Page 13] Internet-Draft Private-DNS March 2014 A request has the following structure: struct { TransactionID transactionID; SecurityContextID securityContextID; opaque encryptedPayload<1..65535> } Request; Where: transactionID Is a unquie identifier for the transaction and an input to the function used to derrive the initialization vector (IV) for the encryption algorithm securityContextID Is the opaque security context identifier returned by the Service Connect Service. encryptedPayload Is the encrypted message payload. 5.2. Response A response MAY consist of 1 or up to 16 packets, each formatted as follows: struct { TransactionID transactionID; uint8 index; uint8 maxIndex; uint16 clearResponse; opaque encryptedPayloadSegment<0..65535> } Response; Where: transactionID Is a unquie identifier for the transaction and an input to the function used to derrive the initialization vector (IV) for the encryption algorithm index Is the index number of this response packet. maxIndex Is the index number of the last packet. The value of maxIndex MUST be the same for every packet. Receivers MUST reject packets Hallam-Baker September 22, 2014 [Page 14] Internet-Draft Private-DNS March 2014 clearResponse Is a response code sent enclair. The value 0 indicates a successful response. Error codes TBS. It might be expedient to merge these with index and maxIndex to shave some bytes. encryptedPayloadSegment Is the encrypted message payload segment. To obtain the encryptedPayload of the response, the receiver: * Waits for all the response packets to arrive * Sorts the response packets by the value of index. * Extracts the value of encryptedPayloadSegment from each response * Concatenate the values of encryptedPayloadSegment to obtain the encryptedPayload value UDP packets MAY be sent out of order and the order in which they were received MAY not match the order in which they were sent. A receiver MUST accept response packets recieved in any order. 5.3. Payload The payload is a sequence of the following types of data:::: DNS Message(s) The Payload MUST contain at least one DNS message Options The Payload may contain additional options (To be defined) Pading The Payload MAY contain padding Message Authentication Code The Payload MUST contain a MAC. this is calculated over the contents of the payload excluding the MAC. For this reason the MAC is always the last data in the payload. Placing the MAC inside the payload ensures that it is encrypted. this prevents a passive attacker determining the length of the MAC which might leak information.. Hallam-Baker September 22, 2014 [Page 15] Internet-Draft Private-DNS March 2014 6. Security Considerations [[TBS] 6.1. Service 6.2. Confidentialityty 6.3. Integrity 6.4. Privacy 7. IANA Considerations 8. Acnowledgementsts 9. References 9.1. Normative References [I-D.hallambaker-jsonbcd] Hallam-Baker, P, "Binary Encodings for JavaScript Object Notation: JSON-B, JSON-C, JSON-D", Internet-Draft draft-hallambaker-jsonbcd-01, 21 January 2014. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5246] Dierks, T.,Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. [RFC2616] Fielding, R.,Gettys, J.,Mogul, J.,Frystyk, H.,Masinter, L.,Leach, P.,Berners-Lee, T., "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. [I-D.hallambaker-wsconnect] Hallam-Baker, P, "JSON Service Connect (JCX) Protocol", Internet-Draft draft-hallambaker- wsconnect-05, 21 January 2014. [RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, 1 November 1987. [I-D.hallambaker-omnibroker] Hallam-Baker, P, "OmniBroker Protocol", Internet-Draft draft-hallambaker-omnibroker-07, 21 January 2014. [RFC4033] Arends, R.,Austein, R.,Larson, M.,Massey, D.,Rose, S., "DNS Security Introduction and Requirements", RFC 4033, March 2005. Hallam-Baker September 22, 2014 [Page 16] Internet-Draft Private-DNS March 2014 Author's Address Phillip Hallam-Baker Comodo Group Inc. philliph@comodo.com Hallam-Baker September 22, 2014 [Page 17]