Internet Engineering Task Force (IETF) F. Ljunggren
Request for Comments: 6841 Kirei AB
Category: Informational AM. Eklund Lowinder
ISSN: 2070-1721 .SE
T. Okubo
ICANN
January 2013
A Framework for DNSSEC Policies and DNSSEC Practice Statements
Abstract
This document presents a framework to assist writers of DNS Security
Extensions (DNSSEC) Policies and DNSSEC Practice Statements, such as
domain managers and zone operators on both the top level and
secondary level, who are managing and operating a DNS zone with
Security Extensions implemented.
In particular, the framework provides a comprehensive list of topics
that should be considered for inclusion into a DNSSEC Policy
definition and Practice Statement.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6841.
Copyright Notice
Copyright (c) 2013 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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Background . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Purpose . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. DNSSEC Policy . . . . . . . . . . . . . . . . . . . . . . 6
3.2. DNSSEC Practice Statement . . . . . . . . . . . . . . . . 7
3.3. Relationship between DNSSEC Policy and Practice
Statement . . . . . . . . . . . . . . . . . . . . . . . . 7
3.4. Set of Provisions . . . . . . . . . . . . . . . . . . . . 8
4. Contents of a Set of Provisions . . . . . . . . . . . . . . . 10
4.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Publication and Repositories . . . . . . . . . . . . . . . 11
4.3. Operational Requirements . . . . . . . . . . . . . . . . . 12
4.4. Facility, Management, and Operational Controls . . . . . . 12
4.5. Technical Security Controls . . . . . . . . . . . . . . . 16
4.6. Zone Signing . . . . . . . . . . . . . . . . . . . . . . . 20
4.7. Compliance Audit . . . . . . . . . . . . . . . . . . . . . 21
4.8. Legal Matters . . . . . . . . . . . . . . . . . . . . . . 22
5. Outline of a Set of Provisions . . . . . . . . . . . . . . . . 23
6. Security Considerations . . . . . . . . . . . . . . . . . . . 25
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8.1. Normative References . . . . . . . . . . . . . . . . . . . 26
8.2. Informative References . . . . . . . . . . . . . . . . . . 26
1. Introduction
1.1. Background
The Domain Name System (DNS) was not originally designed with strong
security mechanisms to provide integrity and authenticity of its
data. Over the years, a number of vulnerabilities have been
discovered that threaten the reliability and trustworthiness of the
system.
The Domain Name System Security Extensions (DNSSEC, [RFC4033],
[RFC4034], [RFC4035]) address these vulnerabilities by using public
key cryptography to add data origin authentication, data integrity
verification, and authenticated denial-of-existence capabilities to
the DNS. In short, DNSSEC provides a way for software to verify the
origin of DNS data and validate that it has not been modified in
transit or by intermediaries.
To provide a means for stakeholders to evaluate the strength and
security of the DNSSEC chain of trust, an entity operating a DNSSEC-
enabled zone may publish a DNSSEC Practice Statement (DPS),
comprising statements describing critical security controls and
procedures relevant for scrutinizing the trustworthiness of the
system. The DPS may also identify any of the DNSSEC Policies (DPs)
it supports, explaining how it meets their requirements.
The DP and DPS are not primarily aimed at users who rely on signed
responses from the DNS ("relying parties"); instead, their audience
is other stakeholders of the DNS infrastructure, a group that may
include bodies such as regulatory authorities.
Even though this document is heavily inspired by the "Internet X.509
Public Key Infrastructure Certificate Policy and Certification
Practices Framework" [RFC3647], with large parts being drawn from
that document, the properties and structure of the DNSSEC trust model
are fundamentally different from those of the X.509 Public Key
Infrastructure (PKI).
1.2. Purpose
The purpose of this document is twofold. Firstly, the document
explains the concepts of a DNSSEC Policy (DP) and of a DNSSEC
Practice Statement (DPS), and it describes the relationship between
the two. Secondly, it presents a framework to encourage and assist
writers of Policies and Practice Statements in creating consistent
and comparable documents. In particular, the framework identifies
the elements that should be considered in formulating a DP or a DPS.
It does not, however, define a particular Policy or Practice
Statement, nor does it seek to provide legal advice or
recommendations as to the contents.
1.3. Scope
The scope of this document is limited to discussion of the topics
that can be covered in a DP or a DPS, but it does not go into the
specific details that could possibly be included in either a DP or a
DPS. In particular, this document describes the types of information
that should be considered for inclusion in them.
This framework should be viewed and used as a checklist of factors
that ought be taken into consideration prior to deploying DNSSEC, and
as an outline to create an operational practices disclosure document.
As such, it focuses on the topics affected by the introduction of
DNSSEC into a zone. Other aspects, such as the operations of name
servers and registry systems, are considered out of scope. The
framework is primarily aimed at Top-Level Domain (TLD) managers and
organizations providing registry services, but it may be used by
high-value domain holders and so serve as a checklist for DNSSEC
readiness at a high level.
This document assumes that the reader is familiar with the general
concepts of DNS, DNSSEC, and PKI.
2. Definitions
This document makes use of the following defined terms:
Audit logs: Control evidence information to prove the integrity of
processes. This may be generated by DNS and DNSSEC-related
systems, supplied by the surrounding facility, or obtained from
manually generated, non-electronic documentation. Audit logs
will be examined by the internal and/or external auditors.
Activation data: Data values, other than keys, required to operate
the cryptographic modules used to protect the keys from
unauthorized use.
Chain of trust: A hierarchical structure of trust consisting of DNS
keys, signatures, and delegation signer records that, when
validated in a series, can provide proof of authenticity of the
last element in the chain, providing that the first element is
trusted. Usually, the first element is a trust anchor.
Compromise (key compromise): Key compromise is a situation where the
private component of a Signing Key signing key is lost, stolen, exposed,
modified, or used in an unauthorized manner. More strictly,
even a suspicion that one of these has occurred will be enough
to be considered as key compromise.
DNS: The Domain Name System (DNS) is a hierarchical global naming
catalog for computers, services, or any resource connected to
the Internet.
DNS zone: A portion of the global Domain Name System (DNS) namespace
for which administrative responsibility has been delegated.
DNSSEC: DNS Security Extensions (DNSSEC) is a set of IETF
specifications [RFC4033] [RFC4034] [RFC4035] that uses public
key cryptography to add data origin authentication, data
integrity verification, and authenticated denial of existence
capabilities to DNS.
DNSSEC Policy: A DNSSEC Policy (DP) sets forth the security
requirements and standards to be implemented for a DNSSEC-
signed zone.
DNSSEC Practice Statement: A DNSSEC Practice Statement (DPS) is a
practices disclosure document that may support and be a
supplemental document to the DNSSEC Policy (if such exists),
and it states how the management of a given zone implements
procedures and controls at a high level.
Key rollover: An operational process to change one of the DNSSEC
keys used for signing a zone via distribution of public keys in
a trusted manner.
Multi-person control: A security concept to distribute the authority
of an operation over multiple persons, to mitigate threats
caused by a single authorized individual. For example, a key
recovery function may require some number of authorized
individuals (m) out of the (n) to whom a portion of the
recovery key was distributed, to combine their key fragments,
before key recovery can occur.
PKI: Public Key Infrastructure (PKI) is a concept that makes use of
asymmetric cryptography to provide a system with integrity,
authentication, and confidentiality and to do it via
distribution of public keys in a trusted manner.
Policy authority: The body responsible for setting and administering
a DNSSEC Policy and for determining whether a DPS is suitable
for that Policy.
Relying party: An entity that relies on a signed response from the
DNS.
Repository: A location on the Internet to store DP, DPS, trust
anchors, and other related information that should be kept
public.
Security posture: A security posture is an indicator of how secure
an entity is and how secure the entity should be. It is the
result of an adequate threat model and risk assessment.
Separation of duties: A security concept that limits the influence
of a single person by segregating roles and responsibilities.
Signing Key: key: Private component of an asymmetric key pair that is
used for signing of resource records within the zone. Note
that the other component, called public key, is used for
signature validation.
TLD: A Top-Level Domain (TLD) is one of the domains at the highest
level below the root in the hierarchy of the DNS.
Trust anchor: Public portion of a key pair that is the authoritative
entity used to authenticate the first element in a chain of
trust.
3. Concepts
This section describes the concepts of a DNSSEC Policy and of a
DNSSEC Practice Statement. Other related concepts are described as
well.
3.1. DNSSEC Policy
A DNSSEC Policy (DP) sets forth requirements that are appropriate for
a specified level of assurance. For example, a DP may encompass all
topics of this framework, each with a certain set of security
requirements, possibly grouped according to impact. The progression
from medium to high levels of assurance would correspond to
increasing security requirements and corresponding increasing levels
of assurance.
A DP also constitutes a basis for an audit, accreditation, or another
assessment of an entity. Each entity can be assessed against one or
more DPs that it claims to implement.
3.2. DNSSEC Practice Statement
Most zone managers using DNSSEC will not have the need to create a
thorough and detailed statement of practices. For example, a
registrant may be the sole relying party of its own zone and would
already be aware of the nature and trustworthiness of its services.
In other cases, a zone manager may provide registration services with
only a very low level of assurances where the domain names being
secured may pose only marginal risks if compromised. Publishing a
DPS is most relevant for entities operating a zone that contains a
significant number of delegations to other entities.
A DNSSEC Practice Statement (DPS) should contain information that is
relevant to the stakeholders of the relevant zone(s). Since these
generally include the Internet community, it should not contain such
information that could be considered to be sensitive details of an
entity's operations.
A DNSSEC Practice Statement may identify a supported DP, which may
subsequently be used by a relying party to evaluate the
trustworthiness of any digital signatures verified using the public
key of that entity.
3.3. Relationship between DNSSEC Policy and Practice Statement
A DNSSEC Policy and a DNSSEC Practice Statement address the same set
of topics of interest to the stakeholders in terms of the level of
confidence ascribed to the security posture of a zone. The primary
difference is in the focus of their provisions. A Policy sets forth
the requirements and standards to be implemented for a DNSSEC-signed
zone, and may be used to communicate requirements that must be met by
complying parties; as such, it may also be used to determine or
establish equivalency between policies associated with different
zones. A Practice Statement, by contrast, describes how a zone
operator (and possibly other participants in the management of a
given zone) implements procedures and controls to meet the
requirements of applicable Policies. In other words, the Policy says
what needs to be done, and the Practice Statement says what is being
done.
An additional difference between a Policy and a Practice Statement
relates to the scope of coverage of the two kinds of documents, in
terms of its applicability. A Policy may apply to multiple
organizations or multiple zones. By contrast, a Practice Statement
would usually apply only to a single zone operator or a single
organization, since it describes the actual controls in place that
meet the requirements of applicable Policy.
For example, a TLD manager or regulatory authority may define
requirements in a Policy for the operation of one or more zones. The
Policy will be a broad statement of the general requirements for
managing the zone. A zone operator may be required to write its own
Practice Statement to support the Policy, explaining how it meets the
requirements of the Policy. Alternatively, a zone operator that is
also the manager of that zone, and not governed by any external
Policy, may still choose to disclose operational practices by
publishing a DPS. The zone operator might do so to provide
transparency and to gain community trust in its operations.
A Policy and a Practice Statement also differ in the level of detail
each expresses: although there may be variations, a Practice
Statement will provide a description of procedures and controls and
so will usually be more detailed than a Policy, which provides
general principles.
The main differences between a Policy and Practice Statement can be
summarized as follows:
(a) Operation of a DNS zone with DNSSEC may be governed by a Policy
that establishes requirements stating what the entity operating
that zone must do. An entity can use a Practice Statement to
disclose how it meets the requirements of a Policy or how it has
implemented critical processes and controls, absent a
controlling Policy.
(b) A Policy may serve the purpose of establishing a common basis of
trusted operation throughout a set of zones in the DNS
hierarchy. By contrast, a Practice Statement is a statement of
a single zone operator or organization.
(c) A Practice Statement is generally more detailed than a Policy
and specifies how the zone operator or organization implements
critical processes and controls, and how the entity meets any
requirements specified in the one or more Policies under which
it operates DNSSEC.
3.4. Set of Provisions
A set of provisions is a collection of Policy requirements or
Practice Statements, which may employ the approach described in this
framework by covering the topics appearing in Section 5 below. The
topics are described in detail in Section 4.
A Policy can be expressed as a single set of provisions.
A Practice Statement can also be expressed as a single set of
provisions with each component addressing the requirements of one or
more Policies. Alternatively, it could be a set of provisions that
do not reference any particular policy but instead describe a set of
self-imposed controls to the stakeholders. For example, a Practice
Statement could be expressed as a combination of the following:
(a) a list of Policies supported by the DPS;
(b) for each Policy in (a), a set of provisions that contains
statements addressing the requirements by filling in details not
stipulated in that policy or expressly left to the discretion of
the implementer. Such statements serve to show how this
particular Practice Statement implements the requirements of the
particular Policy; or
(c) a set of provisions that contains statements regarding the
DNSSEC operations practices, independent of any Policy.
The statements provided in (b) may augment or refine the stipulations
of an applicable Policy, but generally they must not conflict with
the stipulations. In certain cases, however, a Policy authority may
permit exceptions because certain compensating controls of the entity
disclosed in its Practice Statement allow it to provide a level of
assurance equivalent to full compliance with the policy.
The framework outlines the contents of a set of provisions, in terms
of eight primary components, as follows:
1. Introduction
2. Publication and Repositories
3. Operational Requirements
4. Facility, Management, and Operational Controls
5. Technical Security Controls
6. Zone Signing
7. Compliance Audit
8. Legal Matters
This framework can be used by Policy authorities to write DNSSEC
Policies and by zone operators to write a DNSSEC Practice Statements.
Having a set of documents with the same structure facilitates
comparisons with the corresponding documents of other zones.
4. Contents of a Set of Provisions
This section describes the contents of a set of provisions. Refer to
Section 5 for the complete outline.
Drafters of DPSs conforming to this framework are permitted to add
additional levels of subcomponents below those described here to meet
specific needs. All components listed in Section 5 should be
present, but drafters may leave components empty, only stating "no
stipulation", if so required.
4.1. Introduction
This component identifies and introduces the set of provisions, and
indicates the types of entities and applications for which the
document (either Policy or Practice Statement) is targeted.
4.1.1. Overview
This subcomponent provides a general introduction to the document.
It can also be used to provide a description of entities to which the
Policy or Practice Statement applies.
4.1.2. Document Name and Identification
This subcomponent provides any applicable names or other identifiers
of the document.
4.1.3. Community and Applicability
This subcomponent identifies the stakeholders along with their
expected roles and responsibilities. These include (but are not
limited to) an entity signing the zone, entities relying on the
signed zone, other entities that have operational dependency on the
signed zone, and an entity that entrusted the zone signing.
4.1.4. Specification Administration
This subcomponent contains the contact details of the organization
responsible for managing the DP/DPS, as well as the specification
change procedures. These procedures may include the description of
the notification mechanisms used to provide advance notice of
amendments that are deemed to materially affect the assurance
provided by the entity and how/when such amendments will be
communicated to the stakeholders.
If a Policy authority is responsible for determining whether a DPS is
suitable for the Policy, this subcomponent may include the name and
contact information of the entity in charge of making such a
determination. In this case, the subcomponent also includes the
procedures by which this determination is made.
4.2. Publication and Repositories
The component describes the requirements for an entity to publish
information regarding its practices, public keys, the current status
of such keys together with details relating to the repositories in
which the information is held. This may include the responsibilities
of publishing the DPS and of identifying documents that are not made
publicly available owing to their sensitive nature, e.g., security
controls, clearance procedures, or business information.
4.2.1. Repositories
This subcomponent describes the repository mechanisms used for making
information available to the stakeholders, and may include:
o The locations of the repositories and the means by which they may
be accessed;
o An identification of the entity or entities that operate
repositories, such as a zone operator or a TLD manager;
o Access control on published information objects; and
o Any notification services that may be subscribed to by the
stakeholders.
4.2.2. Publication of Public Keys
This subcomponent contains information relating to the publication of
public keys:
o Whether the public keys are included in a key hierarchy, published
as trust anchors, or both;
o The data formats and methods available to validate the
authenticity of public keys;
o The frequency and timing of publishing new information
(principally, as advance notice for stakeholders relying on the
public keys).
4.3. Operational Requirements
This component describes the operational requirements when operating
a DNSSEC-signed zone.
4.3.1. Meaning of Domain Names
This subcomponent describes the overall policy of child zone naming,
if any.
4.3.2. Identification and Authentication of Child Zone Manager
This subcomponent describes how the child zone manager has initially
been identified, and how any subsequent change request is
authenticated as originating from the manager or their authorized
representative.
4.3.3. Registration of Delegation Signer (DS) Resource Records
This subcomponent describes the process of establishing the chain-of-
trust to the child zone by incorporating delegation signer (DS)
record(s) into the zone.
4.3.4. Method to Prove Possession of Private Key
This subcomponent describes whether and, if so, under what
circumstances the child zone manager is required to provide proof of
the possession of the private component of any current or subsequent
child zone Signing Key signing key corresponding to a DS record they wish to
incorporate into the parent zone.
4.3.5. Removal of DS Resource Records
This subcomponent will explain how, when, and under what
circumstances the DS records may be removed from the zone.
4.4. Facility, Management, and Operational Controls
This component describes non-technical security controls (i.e.,
physical, procedural, and personnel) in use by the entity to securely
perform the DNSSEC related functions. Such controls include physical
access, key management, disaster recovery, auditing, and archiving.
These non-technical security controls are critical for trusting the
DNSSEC signatures, since lack of security may compromise DNSSEC
operations. For example, it could result in the creation of
signatures with erroneous information or in the compromise of the
Signing Key.
signing key.
Within each subcomponent, separate consideration will usually need to
be given to each entity type.
4.4.1. Physical Controls
In this subcomponent, the physical controls on the facility housing
the entity systems are described. Topics addressed may include:
o Site location and construction, such as requirements for multiple
tiers of physical barriers, construction requirements for high-
security areas, etc. It may also describe the use of locked
rooms, cages, safes, cabinets, etc.;
o Physical access, i.e., mechanisms to control access from one area
of the facility to another or additional controls for reaching
into higher tiers, such as dual-access control and two-factor
authentication;
o Power and air conditioning;
o Water exposures;
o Fire prevention and protection;
o Media storage, e.g., requiring the storage of backup media in a
separate location that is physically secure and protected from
fire, smoke, particle, and water damage;
o Waste disposal; and
o Off-site backup.
4.4.2. Procedural Controls
In this subcomponent, requirements for recognizing trusted roles are
described, together with a description of the responsibilities of
each role. Examples of trusted roles include system administrators,
security officers, crypto officers, and system auditors.
For each task identified, the number of individuals required to
perform the task (m of n rule, if applicable) should be stated for
each role. Identification and authentication requirements for each
role may also be defined.
This subcomponent also includes the separation of duties in terms of
the roles that cannot be performed by the same individuals.
4.4.3. Personnel Controls
This subcomponent addresses the following:
o Qualifications, experience, and clearances that personnel must
have as a condition of filling trusted roles or other important
roles. Examples include credentials, job experiences, and
official government clearances;
o Background checks and clearance procedures that are required in
connection with the hiring of personnel filling trusted roles or
other important roles. Such roles may require a check of their
criminal records, financial records, references, and any
additional clearances required for the position in question;
o Training requirements and training procedures for each role
following the hiring of personnel;
o Any retraining period and retraining procedures for each role
after completion of initial training;
o Frequency and sequence for job rotation among various roles;
o Sanctions against personnel for unauthorized actions, such as
unauthorized use of authority or unauthorized use of the entity
systems;
o Controls on personnel that are contractors rather than employees
of the entity; examples include:
* Bonding requirements on contract personnel;
* Contractual requirements including indemnification for damages
due to the actions of the contractor personnel;
* Auditing and monitoring of contractor personnel; and
* Other controls on contracting personnel.
o Documentation to be supplied to personnel during initial training,
retraining, or otherwise.
4.4.4. Audit Logging Procedures
This subcomponent is used to describe event logging and audit
systems, implemented for the purpose of maintaining an audit trail
and to provide evidence of process integrity. Elements include the
following:
o Types of events recorded, such as records of key rollover and
other key management operations, the personnel assigned to various
roles, attempts to access the system, and requests made to the
system;
o Frequency with which audit logs are processed or archived, e.g.,
weekly following an alarm or anomalous event or whenever the audit
log size reaches a particular size;
o Period for which audit logs are kept;
o Protection of audit logs:
* Who can view audit logs, for example, only the audit
administrator;
* Protection against modification of audit logs, for instance, a
requirement that no one may modify or delete the audit records
or that only an audit administrator may delete an audit file as
part of audit file rotation; and
* Protection against deletion of audit logs.
o Audit log backup procedures;
o Whether the audit log collection function is internal or external
to the system;
o Whether the subject who caused an audit event to occur is notified
of the audit action; and
o Vulnerability assessments, for example, where audit data is run
through a tool that identifies potential attempts to breach the
security of the system.
4.4.5. Compromise and Disaster Recovery
This subcomponent describes requirements relating to notification and
recovery procedures in the event of compromise or disaster. Each of
the following may need to be addressed separately:
o Identification or listing of the applicable incident and
compromise reporting and handling procedures, which may include
the investigation of measures to prevent the event from
reoccurring.
o The recovery procedures used if computing resources, software,
and/or data are corrupted or suspected to have been corrupted.
These procedures describe how, and under what circumstances,
operations of the system are to be suspended; how and when normal
operations are resumed; how the stakeholders are to be informed;
and how to assess the damage and carry out the root cause
analysis.
o The recovery procedures used if any keys are compromised. These
procedures describe how a secure environment is re-established,
how the keys are rolled over, how a new Trust Anchor trust anchor is provided
to the community (if applicable), and how new zone information is
published.
o The entity's capabilities to ensure business continuity following
a natural or other disaster. Such capabilities may include the
availability of a disaster recovery site at which operations may
be recovered. They may also include procedures for securing its
facility during the period of time following a natural or other
disaster and before a secure environment is re-established, either
at the original site or at a disaster recovery site, for example,
procedures to protect against theft of sensitive materials from an
earthquake-damaged site.
4.4.6. Entity Termination
This subcomponent describes requirements relating to procedures for
termination of a contract with an entity, termination notification,
and transition of responsibilities to another entity. The purpose
may be to ensure that the transition process will be transparent to
the stakeholders, and it will not affect the services.
4.5. Technical Security Controls
This component is used to define the security measures taken to
protect the cryptographic keys and activation data (e.g., PINs,
passwords, or manually held key shares) relevant to DNSSEC
operations. Secure key management is critical to ensure that all
secret and private keys and activation data are protected and used
only by authorized personnel.
Also described here are other technical security controls used to
perform the functions of key generation, authentication,
registration, auditing, and archiving. Technical controls include
life cycle security controls, software development environment
security, and operational security controls.
If applicable, other technical security controls on repositories,
authoritative name servers, or other participants may also be
documented here.
4.5.1. Key Pair Generation and Installation
Key pair generation and installation need to be considered, which may
involve answering the following questions:
1. Who generates the zone's public/private key pairs? How is the
key generation performed? Is the key generation performed by
hardware or software?
2. How is the private key installed in all parts of the key
management system?
3. How are the zone's public keys provided securely to the parent
zone and potential relying parties?
4. Who generates the public key parameters. Is the quality of the
parameters checked during key generation?
5. For what purposes may the keys be used, and/or for what purposes
should usage of the key be restricted?
4.5.2. Private Key Protection and Cryptographic Module Engineering
Controls
Requirements for private key protection and cryptographic modules
need to be considered for key generation and creation of signatures.
The following questions may need to be answered:
1. What standards, if any, are required for the cryptographic
module used to generate the keys? A cryptographic module can be
composed of hardware, software, firmware, or any combination of
them. For example, are the zone's signatures required to be
generated using modules compliant with the US FIPS 140-2
[FIPS-140-2] standard? If so, what is the required FIPS 140-2
level of the module? Are there any other engineering or other
controls relating to a cryptographic module, such as the
identification of the cryptographic module boundary, input/
output, roles and services, finite state machine, physical
security, software security, operating system security,
algorithm compliance, electromagnetic compatibility, and self
tests?
2. Is the private key under m of n multi-person control? If yes,
provide m and n (two-person control is a special case of m of n,
where m = 2 and n >= 2).
3. Is the private key escrowed? If so, who is the escrow agent, in
what form is the key escrowed (e.g., plaintext, encrypted, split
key), and what are the security controls on the escrow system?
4. Is the private key backed up? If so, who is the backup agent,
in what form is the key backed up (e.g., plaintext, encrypted,
split key), and what are the security controls on the backup
system?
5. Is the private key archived? If so, who is the archival agent,
in what form is the key archived (e.g. plaintext, encrypted,
split key), and what are the security controls on the archival
system?
6. Under what circumstances, if any, can a private key be
transferred into or from a cryptographic module? Who is
permitted to perform such a transfer operation? In what form is
the private key during the transfer (e.g., plaintext, encrypted,
or split key)?
7. How is the private key stored in the module (e.g., plaintext,
encrypted, or split key)?
8. Who can activate (use) the private key? What actions must be
performed to activate the private key (e.g., login, power on,
supply PIN, insert token/key, automatic, etc.)? Once the key is
activated, is the key active for an indefinite period, active
for one time, or active for a defined time period?
9. Who can deactivate the private key and how? Examples of methods
of deactivating private keys include logging out, turning the
power off, removing the token/key, automatic deactivation, and
time expiration.
10. Who can destroy the private key and how? Examples of methods of
destroying private keys include token surrender, token
destruction, and zeroizing the key.
4.5.3. Other Aspects of Key Pair Management
Other aspects of key management need to be considered for the zone
operator and other participants. For each of these types of
entities, the following questions may need to be answered:
1. What are the life cycle states for the management of any Signing
Keys? signing
keys?
2. What is the operational period of these keys? What are the usage
periods or active lifetimes for the pairs?
4.5.4. Activation Data
Activation data refers to data values other than whole private keys
that are required to operate private keys or cryptographic modules
containing private keys, such as a PIN, passphrase, or portions of a
private key used in a key-splitting scheme. Protection of activation
data prevents unauthorized use of the private key and potentially
needs to be considered for the zone operator and other participants.
Such a consideration may need to address the entire life cycle of the
activation data from generation through archival and destruction.
For each of the entity types, all of the questions listed in Sections
4.5.1 through 4.5.3 potentially need to be answered with respect to
activation data rather than with respect to keys.
4.5.5. Computer Security Controls
This subcomponent is used to describe computer security controls such
as:
1. use of the trusted computing base concept or equivalent;
2. discretionary access control, labels, mandatory access controls;
3. object reuse;
4. auditing;
5. identification and authentication;
6. trusted path; and
7. security testing.
This subcomponent may also address requirements for product
assurance, product evaluation analysis, testing, profiling, product
certification, and/or product accreditation.
4.5.6. Network Security Controls
This subcomponent addresses network security related controls,
including firewalls, routers, and remote access.
4.5.7. Timestamping
This subcomponent addresses requirements or practices relating to the
use of timestamps on various data. It may also discuss whether or
not the timestamping application must use a trusted time source.
4.5.8. Life Cycle Technical Controls
This subcomponent addresses system development controls and security
management controls.
System development controls include development environment security,
development personnel security, configuration management security
during product maintenance, software engineering practices, software
development methodology, modularity, layering, use of fail-safe
design and implementation techniques (e.g., defensive programming),
and development facility security.
Security management controls include execution of tools and
procedures to ensure that the operational systems and networks adhere
to configured security. These tools and procedures include checking
the integrity of the security software, firmware, and hardware to
ensure their correct operation.
4.6. Zone Signing
This component covers all aspects of zone signing, including the
cryptographic specification surrounding the Signing Keys, signing keys, signing
scheme, and methodology for key rollover and the actual zone signing.
Child zones and other relying parties may depend on the information
in this section to understand the expected data in the signed zone
and determine their own behavior. In addition, this section will be
used to state the compliance to the cryptographic and operational
requirements pertaining to zone signing, if any.
4.6.1. Key Lengths, Key Types, and Algorithms
This subcomponent describes the key generation algorithm, the key
types used for signing the key set and zone data, and key lengths
used to create the keys. It should also cover how changes to these
key lengths, key types, and algorithms may be performed.
4.6.2. Authenticated Denial of Existence
Authenticated denial of existence refers to the usage of NSEC
[RFC4034], NSEC3 [RFC5155], or any other mechanism defined in the
future that is used to authenticate the denial of existence of
resource records. This subcomponent describes what mechanisms are
used, any parameters associated with that mechanism, and how these
mechanisms and parameters may be changed.
4.6.3. Signature Format
This subcomponent is used to describe the signing method and
algorithms used for the zone signing.
4.6.4. Key Rollover
This subcomponent explains the key rollover scheme for each key type.
4.6.5. Signature Lifetime and Re-Signing Frequency
This subcomponent describes the life cycle of the Resource Record
Signature (RRSIG) record.
4.6.6. Verification of Resource Records
This subsection addresses the controls around the verification of the
resource records in order to validate and authenticate the data to be
signed. This may include a separate key set verification process if
using a split key signing scheme.
4.6.7. Resource Records Time-to-Live
This subcomponent specifies the resource records' time-to-live (TTL)
for all types relevant to DNSSEC, as well as any global parameters
that affect the caching mechanisms of the resolvers.
4.7. Compliance Audit
To prove the compliance with a Policy or the statements in the
Practice Statement, a compliance audit can be conducted. This
component describes how the audit is to be conducted at the zone
operator and, possibly, at other involved entities.
4.7.1. Frequency of Entity Compliance Audit
This subcomponent describes the frequency of the compliance audit.
4.7.2. Identity/Qualifications of Auditor
This subcomponent addresses what qualifications are required of the
auditor. For instance, it may be that an auditor must belong to a
specific association or that they have certain certifications.
4.7.3. Auditor's Relationship to Audited Party
This subcomponent is used to clarify the relationship between the
auditor and the entity being audited. This becomes important if
there are any requirements or guidelines for the selection of the
auditor.
4.7.4. Topics Covered by Audit
Topics covered by audit depends on the scope of the audit. Since the
DNSSEC Policy and Practice Statement is the document to be audited
against, it is ideal to set the scope of the audit to the scope of
the DP/DPS. However, the scope may be narrowed down or expanded as
needed, for example, if there are not enough resources to conduct a
full audit or if some portion is under development and not ready for
the audit.
4.7.5. Actions Taken as a Result of Deficiency
This subcomponent specifies the action taken in order to correct any
discrepancy that has a security impact. This could be the
remediation process for the audit findings or any other action to
correct any discrepancy with the DNSSEC Policy or Practice Statement.
4.7.6. Communication of Results
This subcomponent specifies how the results of the audit are
communicated to the stakeholders.
4.8. Legal Matters
The introduction of DNSSEC into a zone may have legal implications.
Consequently, it may be appropriate to declare the legal status of
the binding embodied in the DNSSEC digital signatures and to clarify
on any limitations of liability asserted by the registry manager.
In most cases, the DPS is not a contract or part of a contract;
instead, it is laid out so that its terms and conditions are applied
to the parties by separate documents, such as registrar or registrant
agreements. In other cases, its contents may form part of a legal
contract between parties (either directly or via other agreements).
In this case, legal expertise should be consulted when drawing up
sections of the document that may have contractual implications.
At a minimum, the Legal Matters section should indicate under what
jurisdiction the registry is operated and provide references to any
associated agreements that are in force. It may also be appropriate
to inform of any identified implications on the protection of
personally identifiable private information.
5. Outline of a Set of Provisions
This section contains a recommended outline for a set of provisions,
intended to serve as a checklist or a standard template for use by DP
or DPS writers. Such a common outline will facilitate:
(a) Comparison of a DPS with a DP to ensure that the DPS faithfully
implements the policy.
(b) Comparison of two DPSs.
Section 4 of this document is structured so that it provides guidance
for each corresponding component and subcomponent of the outline.
1. INTRODUCTION
1.1. Overview
1.2. Document name and identification
1.3. Community and applicability
1.4. Specification administration
1.4.1. Specification administration organization
1.4.2. Contact information
1.4.3. Specification change procedures
2. PUBLICATION AND REPOSITORIES
2.1. Repositories
2.2. Publication of public keys
3. OPERATIONAL REQUIREMENTS
3.1. Meaning of domain names
3.2. Identification and authentication of child zone manager
3.3. Registration of delegation signer (DS) resource records
3.4. Method to prove possession of private key
3.5. Removal of DS resource records
3.5.1. Who can request removal
3.5.2. Procedure for removal request
3.5.3. Emergency removal request
4. FACILITY, MANAGEMENT, AND OPERATIONAL CONTROLS
4.1. Physical controls
4.1.1. Site location and construction
4.1.2. Physical access
4.1.3. Power and air conditioning
4.1.4. Water exposures
4.1.5. Fire prevention and protection
4.1.6. Media storage
4.1.7. Waste disposal
4.1.8. Off-site backup
4.2. Procedural controls
4.2.1. Trusted roles
4.2.2. Number of persons required per task
4.2.3. Identification and authentication for each role
4.2.4. Tasks requiring separation of duties
4.3. Personnel controls
4.3.1. Qualifications, experience, and clearance
requirements
4.3.2. Background check procedures
4.3.3. Training requirements
4.3.4. Job rotation frequency and sequence
4.3.5. Sanctions for unauthorized actions
4.3.6. Contracting personnel requirements
4.3.7. Documentation supplied to personnel
4.4. Audit logging procedures
4.4.1. Types of events recorded
4.4.2. Frequency of processing log
4.4.3. Retention period for audit log information
4.4.4. Protection of audit log
4.4.5. Audit log backup procedures
4.4.6. Audit collection system
4.4.7. Vulnerability assessments
4.5. Compromise and disaster recovery
4.5.1. Incident and compromise handling procedures
4.5.2. Corrupted computing resources, software, and/or
data
4.5.3. Entity private key compromise procedures
4.5.4. Business continuity and IT disaster recovery
capabilities
4.6. Entity termination
5. TECHNICAL SECURITY CONTROLS
5.1. Key pair generation and installation
5.1.1. Key pair generation
5.1.2. Public key delivery
5.1.3. Public key parameters generation and quality
checking
5.1.4. Key usage purposes
5.2. Private key protection and cryptographic module
engineering controls
5.2.1. Cryptographic module standards and controls
5.2.2. Private key (m-of-n) multi-person control
5.2.3. Private key escrow
5.2.4. Private key backup
5.2.5. Private key storage on cryptographic module
5.2.6. Private key archival
5.2.7. Private key transfer into or from a cryptographic
module
5.2.8. Method of activating private key
5.2.9. Method of deactivating private key
5.2.10. Method of destroying private key
5.3. Other aspects of key pair management
5.4. Activation data
5.4.1. Activation data generation and installation
5.4.2. Activation data protection
5.4.3. Other aspects of activation data
5.5. Computer security controls
5.6. Network security controls
5.7. Timestamping
5.8. Life cycle technical controls
6. ZONE SIGNING
6.1. Key lengths, key types, and algorithms
6.2. Authenticated denial of existence
6.3. Signature format
6.4. Key rollover
6.5. Signature lifetime and re-signing frequency
6.6. Verification of resource records
6.7. Resource records time-to-live
7. COMPLIANCE AUDIT
7.1. Frequency of entity compliance audit
7.2. Identity/qualifications of auditor
7.3. Auditor's relationship to audited party
7.4. Topics covered by audit
7.5. Actions taken as a result of deficiency
7.6. Communication of results
8. LEGAL MATTERS
6. Security Considerations
The sensitivity of the information protected by DNSSEC at different
tiers in the DNS tree varies significantly. In addition, there are
no restrictions as to what types of information (i.e., DNS records)
that can be protected using DNSSEC. Each relying party must evaluate
its own environment and the chain of trust originating from a trust
anchor, the associated threats and vulnerabilities, to determine the
level of risk it is willing to accept when relying on DNSSEC-
protected objects.
7. Acknowledgements
This document is inspired by RFC 3647 and its predecessor (RFC 2527),
and the authors acknowledge the work in the development of these
documents.
In addition, the authors would like to acknowledge the contributions
made by Richard Lamb, Jakob Schlyter, and Stephen Morris.
8. References
8.1. Normative References
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security
Extensions", RFC 4034, March 2005.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, March 2005.
8.2. Informative References
[FIPS-140-2] NIST, "Security Requirements for Cryptographic
Modules", June 2005, <http://csrc.nist.gov/
publications/fips/fips140-2/fips1402.pdf>.
[RFC3647] Chokhani, S., Ford, W., Sabett, R., Merrill, C., and S.
Wu, "Internet X.509 Public Key Infrastructure
Certificate Policy and Certification Practices
Framework", RFC 3647, November 2003.
[RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
Security (DNSSEC) Hashed Authenticated Denial of
Existence", RFC 5155, March 2008.
Authors' Addresses
Fredrik Ljunggren
Kirei AB
P.O. Box 53204
Goteborg SE-400 16
Sweden
EMail: fredrik@kirei.se
Anne-Marie Eklund Lowinder
.SE (The Internet Infrastructure Foundation)
P.O. Box 7399
Stockholm SE-103 91
Sweden
EMail: amel@iis.se
Tomofumi Okubo
Internet Corporation For Assigned Names and Numbers
4676 Admiralty Way, Suite 330
Marina del Ray, CA 90292
USA
EMail: tomofumi.okubo@icann.org