ISO/IEC 20648:2016

Information technology — TLS specification for storage systems

ISO/IEC 20648:2016 details the requirements for use of the Transport Layer Security (TLS) protocol in conjunction with data storage technologies. The requirements set out in this specification are intended to facilitate secure interoperability of storage clients and servers as well as non-storage technologies that may have similar interoperability needs. ISO/IEC 20648:2016 is relevant to anyone involved in owning, operating or using data storage devices. This includes senior managers, acquirers of storage product and service, and other non-technical managers or users, in addition to managers and administrators who have specific responsibilities for information security and/or storage security, storage operation, or who are responsible for an organization's overall security program and security policy development. It is also relevant to anyone involved in the planning, design and implementation of the architectural aspects of storage security.

Technologies de l'information — Spécification TLS pour systèmes de stockage

General Information

• Status: Published
• Publication Date: 02-Mar-2016
• ICS: 35.030 - IT Security
• ICS: 35.040 - Information coding
• ICS: 35.220.01 - Data storage devices in general
• Technical Committee: ISO/IEC JTC 1 - Information technology
• Drafting Committee: ISO/IEC JTC 1 - Information technology
• Current Stage: 9092 - International Standard to be revised
• Completion Date: 24-Jan-2023

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 20648
First edition
2016-03-01
Information technology — TLS
specification for storage systems
Technologies de l’information — Spécification TLS pour systèmes de
stockage
Reference number
ISO/IEC 20648:2016(E)
©
ISO/IEC 2016

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ISO/IEC 20648:2016(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
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ISO/IEC 20648:2016(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
5 Overview and concepts . 3
5.1 General . 3
5.2 Storage specifications . 3
5.3 Overview of TLS . 4
5.3.1 TLS Background . . . 4
5.3.2 TLS functionality . 4
5.3.3 Summary of cipher suites. 4
5.3.4 X.509 digital certificates . 5
6 Requirements . 5
6.1 TLS protocol requirements . 5
6.2 Cipher suites . 6
6.2.1 Required cipher suites for interoperability . 6
6.2.2 Recommended cipher suites for enhanced security . 6
6.3 Digital certificates. 7
7 Guidance for the implementation and use of TLS in data storage .7
7.1 Digital certificates. 7
7.1.1 Certificate model . 7
7.1.2 Chain of trust . 8
7.1.3 Certificate lifecycle . 8
7.1.4 Revocation . 8
7.2 Security awareness . 8
7.3 Cipher suites . 9
7.4 Using TLS with HTTP . 9
7.5 Use of pre-shared keys . 9
Bibliography .11
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ISO/IEC 20648:2016(E)

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical
activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the
work. In the field of information technology, ISO and IEC have established a joint technical committee,
ISO/IEC JTC 1.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for
the different types of document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent
rights. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT), see the following URL: Foreword — Supplementary information.
ISO/IEC 20648 was prepared by the Storage Networking Industry Association (SNIA) [as TLS
Specification for Storage Systems, Version 1.0.1] and was adopted, under the PAS procedure, by Joint
Technical Committee ISO/IEC JTC 1, Information technology, in parallel with its approval by the national
bodies of ISO and IEC. The content of ISO/IEC 20648 and SNIA TLS Specification for Storage Systems
Version 1.0.1 is identical.
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Introduction
Within Information and Communications Technology (CT), one of the best defenses against
telecommunications attacks is to deploy security services implemented with mechanisms specified
in standards that are thoroughly vetted in the public domain and rigorously tested by third party
laboratories, by vendors, and by users of commercial off-the-shelf products. Three services that
most often address network user security requirements are confidentiality, message integrity and
authentication.
The Internet Engineering Task Force (IETF) with its Transport Layer Security (TLS) has a standard that
is able to prevent tampering, message forgery, and eavesdropping by encrypting data units, or segments,
from one end of the transport layer to the other. In addition, TLS is application protocol independent,
which means higher-level protocols like HTTP can layer on top of the TLS protocol transparently.
Additional details beyond the basic TLS protocol specification are necessary to ensure both security
and interoperability. This specification provides that detail in the form of specific requirements and
guidance for using Transport Layer Security (TLS) in conjunction with storage systems.
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INTERNATIONAL STANDARD ISO/IEC 20648:2016(E)
Information technology — TLS specification for storage
systems
1 Scope
This specification details the requirements for use of the Transport Layer Security (TLS) protocol in
conjunction with data storage technologies. The requirements set out in this specification are intended
to facilitate secure interoperability of storage clients and servers as well as non-storage technologies
that may have similar interoperability needs.
This specification is relevant to anyone involved in owning, operating or using data storage devices.
This includes senior managers, acquirers of storage product and service, and other non-technical
managers or users, in addition to managers and administrators who have specific responsibilities
for information security and/or storage security, storage operation, or who are responsible for an
organization’s overall security program and security policy development. It is also relevant to anyone
involved in the planning, design and implementation of the architectural aspects of storage security.
2 Normative references
The following referenced documents, in whole or in part, are normatively referenced in this document
and are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 27000, Information technology — Security techniques — Information security management
systems — Overview and vocabulary
IETF RFC 5280, Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL)
Profile, IETF, 2008
IETF RFC 5246, The Transport Layer Security (TLS) Protocol Version 1.2, IETF, 2008
IETF RFC 5746, Transport Layer Security (TLS) Renegotiation Indication Extension, IETF, 2010
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 27000 and the
following apply.
3.1
cipher suite
named combination of authentication, encryption, and message authentication code algorithms used to
negotiate the security settings for a network connection
Note 1 to entry: Cipher suites are typically used with the Transport Layer Security (TLS) and the Secure Sockets
Layer (SSL) network protocols.
3.2
digital certificate
data structure signed with a digital signature that is based on a public key and which asserts that the
key belongs to a subject identified in the structure
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3.3
perfect forward secrecy
security condition in which a leaving entity cannot obtain any subsequent shared secret keys
[SOURCE: ISO/IEC 11770-5:2011, 3.24]
3.4
proxy
intermediary that acts as both a server and a client for the purpose of making requests on behalf of
other clients
3.5
self-signed certificate
digital certificate (3.2) that is signed by the same entity whose identity it certifies
Note 1 to entry: A self-signed certificate is one signed with its own private key.
3.6
security strength
a number associated with the amount of work (i.e. the number of operations) that is required to break a
cryptographic algorithm or system
Note 1 to entry: Security strength is specified in bits, and is a specific value from the set {80, 112, 128, 192, 256}.
b
A security strength of b bits means that of the order of 2 operations are required to break the system.
[SOURCE: ISO/IEC 9797-2:2011, 3.14]
4 Symbols and abbreviated terms
3DES Triple Data Encryption Standard
AED Authenticated Encryption with Additional Data
AES Advanced Encryption Standard
CA Certificate Authority
CBC Cipher Block Chaining
CDMI Cloud Data Management Interface
CRL Certificate Revocation List
CRLDP CRL Distribution Point
DER Distinguished Encoding Rules
DHE Ephemeral Diffie-Hellman
DSA Digital Signature Algorithm
ECDHE Elliptic Curve Ephemeral Diffie–Hellman
ECDSA Elliptic Curve Digital Signature Algorithm
EDE Encryption-Decryption-Encryption
GCM Galois/Counter Mode
HMAC Hash-based Message Authentication Code
HTTP Hypertext Transfer Protocol
HTTPS Hypertext Transfer Protocol Secure
ICT Information and Communications Technology
IETF Internet Engineering Task Force
IP Internet Protocol
MAC Message Authentication Code
MD5 Message Digest 5
OCSP Online Certificate Status Protocol
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PEM Privacy Enhanced Mail
PKCS Public-Key Cryptography Standards
PKI Public Key Infrastructure
PSK Pre-Shared Key
RFC Request For Comment
RSA Rivest, Shamir, and Adelman algorithm
SHA Secure Hash Algorithm
SMI-S Storage Management Initiative – Specification
SNIA Storage Networking Industry Association
SSL Secure Socket Layer
TCP Transmission Control Protocol
TLS Transport Layer Security
5 Overview and concepts
5.1 General
Data storage systems and infrastructure increasingly use technologies such as protocols over TCP/IP
to manage the systems and data as well as to access the data. In many situations, the historical reliance
on isolated connectivity, specialized technologies, and the physical security of data centers are not
sufficient to protect data, especially when the data is considered sensitive and/or high value. Thus,
there is a need to include security at the transport layer and at the same time, ensure interoperability.
The Transport Layer Security (TLS) and its predecessor, the Security Socket Layer (SSL), have been used
successfully to protect a wide range of communications over TCP/IP. Recognizing this fact, the storage
industry has mandated the use of TLS/SSL in conjunction with the Hypertext Transfer Protocol (HTTP)
for multiple specifications (see 5.2). Unfortunately, these storage specifications tend to be lengthy and
complex, resulting in long development cycles that don’t allow for rapid requirements changes due to
security vulnerabilities or new attacks.
The objectives for this specification are to:
— Specify the TLS elements necessary to secure storage management and data access
— Facilitate timely updates and enhancements to the security for the storage specifications
— Ensure storage clients and systems can interoperate securely
— Support non-storage technologies that may have similar TLS interoperability needs
5.2 Storage specifications
As a starting point, the TLS requirements were extracted from the following specification:
— ISO/IEC 17826:2012, Information technology — Cloud Data Management Interface (CDMI)
— Storage Networking Industry Association (SNIA), Storage Management Initiative – Specification
(SMI-S), Version 1.6.1
These requirements were then harmonized, eliminating minor differences. The resulting requirements
(see clause 6) have been updated to reflect the current state of TLS and attack mitigation strategies.
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5.3 Overview of TLS
5.3.1 TLS Background
TLS is a protocol that provides communications security over networks. It allows client/server
applications to communicate in a way that is designed to prevent eavesdropping, tampering, or
message forgery. TLS is layered on top of some reliable transport protocol (e.g., TCP), and it is used for
encapsulation of various higher-level protocols (e.g., HTTP).
TLS version 1.2 of the protocol is specified in IETF RFC 5246. Earlier, and less secure, versions of TLS
are also specified and in use; TLS versions 1.0 is specified in IETF RFC 2246 and TLS versions 1.1 is
specified in IETF RFC 4346. The predecessor to TLS, The Secure Sockets Layer (SSL), and in particular,
version 3.0 is also in use, but also considered less secure; SSL 3.0 is documented in the historical IETF
RFC 6101, The Secure Sockets Layer (SSL) Protocol Version 3.0.
5.3.2 TLS functionality
TLS provides endpoint authentication and communications privacy over the network using
cryptography. Typically, only the server is authenticated (i.e., its identity is ensured) while the client
remains unauthenticated; this means that the end user (whether an individual or an application) has a
measure of assurance with whom they are communicating. Mutual authentication (the identities of both
endpoints are verified) requires, with few exceptions, the deployment of digital certificates on the client.
TLS involves three basic phases:
a) Peer negotiation for algorithm support
b) Key exchange and authentication
c) Symmetric cipher encryption and message authentication
During the first phase, the client and server negotiate cipher suites (see 5.3.3), which determine the
ciphers to be used, the key exchange, authentication algorithms, and the Message Authentication Codes
(MACs). The key exchange and authentication algorithms are typically public key algorithms. The MACs
are made up from a keyed-Hash Message Authentication Code, or HMAC.
5.3.3 Summary of cipher suites
Both TLS and SSL 3.0 package one key establishment, confidentiality, signature and hash algorithm
into a “cipher suite.” A registered 16-bit (4 hexadecimal digit) number, called the cipher suite index,
is assigned for each defined cipher suite. For example, RSA key agreement, RSA signature, Triple Data
Encryption Standard (3DES) using Encryption-Decryption-Encryption (EDE) and Cipher Block Chaining
(CBC) confidentiality, and the Secure Hash Algorithm (SHA-1) hash are assigned the hexadecimal value
{0x000A} and given a label of TLS_RSA_WITH_3DES_EBE_CBC_SHA for TLS.
To ensure a measure of interoperability between clients and servers, each version of TLS specifies a
1)
mandatory cipher suite that all compliant applications are required to implement. The following are
the mandatory cipher suites associated with the different versions of TLS:
— TLS 1.0: TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA {0x00, 0x13}
— TLS 1.1: TLS_RSA_WITH_3DES_EBE_CBC_SHA {0x00, 0x0A}
— TLS 1.2: TLS_RSA_WITH_AES_128_CBC_SHA {0x00, 0x0F}
The client always initiates the TLS session and starts cipher suite negotiation by transmitting a
handshake message that lists the cipher suites (by index value) that it will accept. The server responds

1) Section 9 - Mandatory Cipher Suites of each of the corresponding TLS IETF RFCs is where these mandatory
cipher suites are specified. The mandatory cipher suite is required to be implemented and supported in the absence
of an application profile.
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with a handshake message indicating which cipher suite it selected from the list or an “abort.” Although
the client orders its list of cipher suite by preference, starting with the most preferred, the server
may choose any of the cipher suites proposed by the client. Therefore, there is no guarantee that the
negotiation will select the strongest suite. If no cipher suites are mutually supported, the connection is
aborted.
NOTE When the negotiated options, includin
...