None. G. Jones, Editor
Internet-Draft The MITRE Corporation
Expires: April 24, 2004 October 25, 2003
Operational Security Requirements for IP Network Infrastructure:
Best-Current-Practices
draft-jones-opsec-02
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at http://
www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on April 24, 2004.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document defines a list of operational security requirements for
the infrastructure of large IP networks (routers and switches) which
are considered to be best current practice (BCP). A framework is
defined for specifying "profiles", which are collections of
requirements applicable to certain classes of devices (all,
core-only, edge-only...). The goal is to provide consumers of network
equipment a clear, concise way of communicating their security
requirements to vendors of such equipment. The requirements in this
document are considered to be best current practice (BCP). Comments
to: "opsec-comment@ops.ietf.org".
Jones, Editor Expires April 24, 2004 [Page 1]
Internet-Draft Operational Security Requirements October 2003
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 5
1.1 Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3 Definition of a Secure Network . . . . . . . . . . . . . . 5
1.4 Intended Audience . . . . . . . . . . . . . . . . . . . . 6
1.5 Format . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.6 Intended Use . . . . . . . . . . . . . . . . . . . . . . . 7
1.7 Definitions . . . . . . . . . . . . . . . . . . . . . . . 7
2. Functional Requirements . . . . . . . . . . . . . . . . . 8
2.1 Device Management Requirements . . . . . . . . . . . . . . 8
2.1.1 Support Secure Management Channels . . . . . . . . . . . . 8
2.2 In-Band Management Requirements . . . . . . . . . . . . . 8
2.2.1 Use Encryption Algorithms Subject To Open Review . . . . . 9
2.2.2 Use Strong Encryption . . . . . . . . . . . . . . . . . . 9
2.3 Out-of-Band (OoB) Management Requirements . . . . . . . . 10
2.3.1 Support a Non-IP 'Console' interface . . . . . . . . . . . 10
2.3.2 Support A Simple Default Communication Profile On The
'Console' . . . . . . . . . . . . . . . . . . . . . . . . 10
2.3.3 Support Separate Management Plane IP Interfaces . . . . . 11
2.3.4 No Forwarding Between Management Plane And Other
Interfaces . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3.5 Provide Separate Resources For The Management Plane . . . 12
2.4 Configuration and Management Interface Requirements . . . 12
2.4.1 CLI Provides Access to All Configuration and
Management Functions . . . . . . . . . . . . . . . . . . . 13
2.4.2 CLI Uses Existing Authentication Mechanisms . . . . . . . 13
2.4.3 CLI Supports Scripting of Configuration . . . . . . . . . 13
2.4.4 CLI Supports Management Over 'Slow' Links . . . . . . . . 14
2.4.5 Support Software Installation . . . . . . . . . . . . . . 14
2.4.6 Support Remote Configuration Backup . . . . . . . . . . . 15
2.4.7 Support Remote Configuration Restore . . . . . . . . . . . 16
2.4.8 Support Human-Readable Configuration File . . . . . . . . 16
2.5 IP Stack Requirements . . . . . . . . . . . . . . . . . . 16
2.5.1 Ability to Identify All Listening Services . . . . . . . . 17
2.5.2 Ability to Disable Any and All Services . . . . . . . . . 17
2.5.3 Listening Services Should Be Off By Default . . . . . . . 17
2.5.4 Ability to Control Service Bindings for Listening
Services . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.5.5 Ability to Control Service Source Address . . . . . . . . 18
2.5.6 Support Automatic Anti-spoofing for Single-Homed
Networks . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.5.7 Directed Broadcasts Disabled by Default . . . . . . . . . 20
2.6 Rate Limiting Requirements . . . . . . . . . . . . . . . . 20
2.6.1 Support Rate Limiting . . . . . . . . . . . . . . . . . . 20
2.6.2 Support Rate Limiting Based on State . . . . . . . . . . . 21
2.7 Basic Filtering Capabilities . . . . . . . . . . . . . . . 21
Jones, Editor Expires April 24, 2004 [Page 2]
Internet-Draft Operational Security Requirements October 2003
2.7.1 Ability to Filter Traffic . . . . . . . . . . . . . . . . 21
2.7.2 Ability to Filter Traffic TO the Device . . . . . . . . . 22
2.7.3 Ability to Filter Traffic THROUGH the Device . . . . . . . 22
2.7.4 Ability to Filter Without Performance Degradation . . . . 22
2.7.5 Ability to Filter Updates . . . . . . . . . . . . . . . . 23
2.7.6 Ability to Specify Filter Actions . . . . . . . . . . . . 24
2.7.7 Ability to Log Filter Actions . . . . . . . . . . . . . . 24
2.8 Packet Filtering Criteria . . . . . . . . . . . . . . . . 25
2.8.1 Ability to Filter on Protocols . . . . . . . . . . . . . . 25
2.8.2 Ability to Filter on Addresses . . . . . . . . . . . . . . 25
2.8.3 Ability to Filter on Any Protocol Header Fields . . . . . 25
2.8.4 Ability to Filter Inbound and Outbound . . . . . . . . . . 26
2.9 Packet Filtering Counter Requirements . . . . . . . . . . 26
2.9.1 Ability to Accurately Count Filter Hits . . . . . . . . . 26
2.9.2 Ability to Display Filter Counters . . . . . . . . . . . . 27
2.9.3 Ability to Display Filter Counters per Rule . . . . . . . 27
2.9.4 Ability to Display Filter Counters per Filter
Application . . . . . . . . . . . . . . . . . . . . . . . 28
2.9.5 Ability to Reset Filter Counters . . . . . . . . . . . . . 28
2.9.6 Filter Counters Must Be Accurate . . . . . . . . . . . . . 28
2.10 Other Packet Filtering Requirements . . . . . . . . . . . 29
2.10.1 Filter, Counters, and Filter Log Must Have Minimal
Performance Impact . . . . . . . . . . . . . . . . . . . . 29
2.10.2 Ability to Specify Filter Log Granularity . . . . . . . . 30
2.11 Event Logging Requirements . . . . . . . . . . . . . . . . 30
2.11.1 Logging Facility Conforms to Open Standards . . . . . . . 30
2.11.2 Ability to Log to Remote Server . . . . . . . . . . . . . 31
2.11.3 Ability to Log Locally . . . . . . . . . . . . . . . . . . 31
2.11.4 Ability to Maintain Accurate System Time . . . . . . . . . 31
2.11.5 Logs Must Be Timestamped . . . . . . . . . . . . . . . . . 32
2.11.6 Logs Contain Untranslated Addresses . . . . . . . . . . . 32
2.12 Authentication, Authorization, and Accounting (AAA)
Requirements . . . . . . . . . . . . . . . . . . . . . . . 33
2.12.1 Authenticate All User Access . . . . . . . . . . . . . . . 33
2.12.2 Support Authentication of Individual Users . . . . . . . . 33
2.12.3 Support Simultaneous Connections . . . . . . . . . . . . . 34
2.12.4 Ability to Disable All Local Accounts . . . . . . . . . . 34
2.12.5 Support Centralized User Authentication Methods . . . . . 35
2.12.6 Support Local User Authentication Method . . . . . . . . . 35
2.12.7 Support Configuration of Order of Authentication
Methods . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.12.8 No Unencrypted Transmission of Reusable Plain-text
Passwords . . . . . . . . . . . . . . . . . . . . . . . . 36
2.12.9 No Default Passwords . . . . . . . . . . . . . . . . . . . 37
2.12.10 Passwords Must Be Explicitly Configured Prior To Use . . . 37
2.12.11 Ability to Define Privilege Levels . . . . . . . . . . . . 38
2.12.12 Ability to Assign Privilege Levels to Users . . . . . . . 38
2.12.13 Default Privilege Level Must Be Read Only . . . . . . . . 39
Jones, Editor Expires April 24, 2004 [Page 3]
Internet-Draft Operational Security Requirements October 2003
2.12.14 Change in Privilege Levels Requires Re-Authentication . . 39
2.12.15 Support Recovery Of Privileged Access . . . . . . . . . . 39
2.12.16 Accounting Records . . . . . . . . . . . . . . . . . . . . 40
2.13 Layer 2 Devices Must Meet Higher Layer Requirements . . . 41
3. Documentation Requirements . . . . . . . . . . . . . . . . 42
3.1 Document Listening Services . . . . . . . . . . . . . . . 42
4. Assurance Requirements . . . . . . . . . . . . . . . . . . 43
4.1 Comply With Relevant IETF RFCs on All Protocols
Implemented . . . . . . . . . . . . . . . . . . . . . . . 43
4.2 Identify Origin of IP Stack . . . . . . . . . . . . . . . 44
4.3 Identify Origin of Operating System . . . . . . . . . . . 44
5. Security Considerations . . . . . . . . . . . . . . . . . 46
References . . . . . . . . . . . . . . . . . . . . . . . . 47
Author's Address . . . . . . . . . . . . . . . . . . . . . 48
A. Requirement Profiles . . . . . . . . . . . . . . . . . . . 49
A.1 Minimum Requirements Profile . . . . . . . . . . . . . . . 49
A.1.1 Functional Requirements . . . . . . . . . . . . . . . . . 49
A.1.2 Documentation Requirements . . . . . . . . . . . . . . . . 52
A.1.3 Assurance Requirements . . . . . . . . . . . . . . . . . . 53
A.2 Layer 3 Network Core Profile . . . . . . . . . . . . . . . 53
A.2.1 Functional Requirements . . . . . . . . . . . . . . . . . 53
A.3 Layer 3 Network Edge Profile . . . . . . . . . . . . . . . 53
A.3.1 Functional Requirements . . . . . . . . . . . . . . . . . 53
B. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 55
Intellectual Property and Copyright Statements . . . . . . 56
Jones, Editor Expires April 24, 2004 [Page 4]
Internet-Draft Operational Security Requirements October 2003
1. Introduction
1.1 Goals
This document defines a list of operational security requirements for
the infrastructure of large IP networks (routers and switches) which
are considered to be best current practice (BCP). The goal is to
provide consumers of IP network infrastructure a clear, concise way
of communicating their security requirements to equipment vendors.
1.2 Scope
The primary scope of these requirements is intended to cover the
infrastructure of large IP networks (e.g. routers and switches).
Certain groups (or "profiles", see below) apply only in specific
situations (e.g. all, edge-only, core-only). The requirements listed
in the minimum profile are intended to apply to all managed
infrastructure devices.
General purpose hosts (including infrastructure hosts such as name/
time/log/AA servers, etc.), unmanaged, or customer managed devices
(e.g. firewalls, Intrusion Detection System, dedicated VPN devices,
etc.) are explicitly out of scope. This means that while the
requirements in the minimum profile (and others) may apply,
additional requirements will not be added to account for their unique
needs.
Confidentiality and integrity of customer data are outside the scope.
While, the examples given are written with IPv4 in mind, most of the
requirements are general enough to apply to IPv6.
1.3 Definition of a Secure Network
For the purposes of this document, a secure network is one in which:
o the network keeps passing legitimate customer traffic
(availability)
o traffic goes where its supposed to go
(availability,confidentiality)
o the network elements remain manageable (availability)
o only authorized users can manage network elements (authorization)
o there is record of all security related events (accountability)
Jones, Editor Expires April 24, 2004 [Page 5]
Internet-Draft Operational Security Requirements October 2003
o the network operator has the necessary tools to detect and respond
to illegitimate traffic
The following assumptions are made:
o Devices are physically secure.
o The management infrastructure (AAA/DNS/log server, SNMP management
stations, etc.) is secure.
1.4 Intended Audience
There are two intended audiences: the end user (consumer) who
selects, purchases, and operates IP network equipment, and the
vendors who create them.
1.5 Format
The individual requirements are listed in one of the three sections
listed below.
o Section 2 lists functional requirements.
o Section 3 lists documentation requirements.
o Section 4 lists assurance requirements.
Within these areas, requirements are grouped in major functional
areas (e.g., logging, authentication, filtering, etc.)
Each requirement has the following subsections:
o The Requirement (What)
o The Justification (Why)
o Examples (How)
o Warnings (if applicable)
The requirement describes a policy to be supported by the device. The
justification tells why and in what context the requirement is
important. The examples section is intended to give examples of
implementations that may meet the requirement. Examples cite
technology and standards current at the time of this writing. It is
expected that the choice of implementations to meet the requirements
will change over time. The warnings list operational concerns,
Jones, Editor Expires April 24, 2004 [Page 6]
Internet-Draft Operational Security Requirements October 2003
deviation from standards, caveats, etc.
Security requirements will vary across different device types and
different organizations, depending on policy and other factors. A
desired feature in one environment may be a requirement in another.
Classifications must be made according to local need.
In order to assist in classification, the Appendix Appendix A defines
several requirement "profiles" for different types of devices.
Profiles are simply collections of requirements. They provide a
concise list of the requirements that apply to certain classes of
devices. The profiles in this document should be reviewed to
determine if they are appropriate the local environment.
1.6 Intended Use
It is anticipated that this document will be used in the following
manners:
Security Capability Checklist The requirements in this document may
be used as a checklist when evaluating networked products.
Composing Profiles Different subsets of these requirements may be
compiled to describe the needs of different devices,
organizations, and operating environments.
Communicating Requirements This document may be referenced, along
with profiles, to clearly communicate security requirements.
Basis For Testing and Certification This document may form the basis
for testing and certification of security features of networked
products.
1.7 Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Unless otherwise indicated, "IP" refers to IPv4
Jones, Editor Expires April 24, 2004 [Page 7]
Internet-Draft Operational Security Requirements October 2003
2. Functional Requirements
The requirements in this section are intended to list testable,
functional requirements that are needed to operate devices securely.
2.1 Device Management Requirements
2.1.1 Support Secure Management Channels
Requirement. The device MUST provide secure end-to-end channels for
all network traffic and protocols used to support management
functions. This MUST include at least protocols used for
configuration, monitoring, configuration backup, logging, time
synchronization, authentication, and routing. This requirement MAY
be satisfied using either In-Band or Out-of-Band management. See
Section 2.2 and Section 2.3.
Justification. Secure channels ensure confidentiality and integrity
of management traffic.
Examples. Different mechanisms may be used with different protocols
to satisfy this requirement. Secure management can be achieved
by the use of in-band protocols that support encryption, by using
insecure protocols over top of secure transports such as TLS or
IPsec or by the use of out-of-band management. For example
Secure protocols: SSH, SFTP, SNMPv3, BGP, NTP, Kerberos.
Insecure protocols tunneled: telnet, TFTP, SNMPv1 syslog, over TLS
or IPsec
Warnings. None.
2.2 In-Band Management Requirements
This section lists security requirements for devices that are managed
In-band. "In-band management" is defined as any management done over
the same channels and interfaces used for user/customer data.
Examples would include using SSH for management via customer or
Internet facing network interfaces. In-band management has the
advantage of lower cost (no extra interfaces or lines), but has
significant security disadvantages:
o saturation of customer lines or interfaces can make the device
unmanageable
o since public interfaces/channels are used, it is possible for
Jones, Editor Expires April 24, 2004 [Page 8]
Internet-Draft Operational Security Requirements October 2003
attackers to directly address and reach the device and to attempt
management functions
o in-band management traffic on public interfaces may be intercepted
o Since the same networking code and interfaces are shared for
management and customer data, it is not possible to isolate
management functions from failures in other areas (for example, a
"magic packet" or buffer overrun that causes the data forwarding
portions of a router to crash will also likely make it impossible
to manage...this would not necessarily be the case if the
management and data forwarding elements were completely separated)
2.2.1 Use Encryption Algorithms Subject To Open Review
Requirement. If encryption is used to satisfy the Section 2.1.1
requirements, then the encryption algorithms used MUST be subject
to open review.
Justification. Proprietary encryption algorithms and protocols that
have not been subjected to public/peer review are more likely to
have undiscovered weaknesses or flaws than open standards and
publicly reviewed algorithms.
Examples. For applications requiring symmetric encryption AES or 3DES
satisfy the requirement. For applications requiring asymmetric
encryption RSA and Elliptic Curve satisfy the requirement. For
key exchange Diffie-Hellman meets the requirement. For message
digests MD5 and SHA meet the requirement.
Warnings. Open review is necessary but not sufficient. The strength
of the algorithm and key length must also be considered. For
example, 56-bit DES meets the open review requirement, but is
today considered too weak and is therefore not recommended.
2.2.2 Use Strong Encryption
Requirement. If encryption is used to satisfy the Section 2.1.1
requirements, then the key lengths and algorithms SHOULD be
"strong".
Justification. Short keys and weak algorithms threaten the
confidentiality and integrity of communications.
Jones, Editor Expires April 24, 2004 [Page 9]
Internet-Draft Operational Security Requirements October 2003
Examples. This document explicitly does not attempt to make any
authoritative statement about what key lengths and algorithms
constitute "strong" encryption. The reader is encouraged to
consult the literature and to seek advice from trusted third
parties to determine which algorithms and key lengths provide
sufficiently "strong" encryption at any given time to protect data
of a given value.
Warnings. "Strong" is a relative term. Long keys and strong
algorithms are intended to increase the work factor required to
compromise the security of the data protected. Over time, as
processing power increases, the security provided by a given
algorithm and key length will degrade. The definition of "Strong"
must be constantly reevaluated. There may be legal issues
governing the use of encryption and the strength of encryption
used.
2.3 Out-of-Band (OoB) Management Requirements
See Section 2.2 for a discussion of the advantages and disadvantages
of In-band vs. Out-of-Band management.
2.3.1 Support a Non-IP 'Console' interface
Requirement. The device MUST support complete configuration and
management via a non-IP interface.
Justification. There are times when the device *must* be managed or
configured, even when the network is unavailable, routing and
network interfaces are incorrectly configured, the IP stack and/or
operating system may not be working (or may be vulnerable to
recently discovered exploits that make their use impossible/
inadvisable), or when high bandwidth paths to the device are
unavailable. In such situations, non-IP interfaces can provide a
way to manage and configure the device.
Examples. One example would be an RS232 (EIA232) interface that
provides the capability to load new versions of the system
software and to perform configuration via a command line
interface. RS232 interfaces are ubiquitous and well understood.
Warnings. None.
2.3.2 Support A Simple Default Communication Profile On The 'Console'
Jones, Editor Expires April 24, 2004 [Page 10]
Internet-Draft Operational Security Requirements October 2003
Requirement. The device MUST support a simple default profile of
communications parameters on the Non-IP management interface.
These communications parameters MUST be published in the system
documentation. There SHOULD be a method defined and published for
returning to the default configuration.
Justification. A simple, standard profile minimizes confusion and
maximizes the chances of successful and well understood recovery
practices. This profile follows the principals of "least surprise"
and "Be liberal in what you accept and conservative in what you
send."
Examples. The following is a profile widely used for RS232 console
connections: the only required signals SHOULD be Transmit Data
(TD), Receive Data (RD) and Signal Ground (SG). Other signals,
SHOULD NOT be required (e.g. DCD, RTS, CTS, DSR, etc.). The
default settings SHOULD be 9600bps, 8 bit data, no parity, one
stop-bit (9600 8n1). Sending a break would be one way to signal
that the communications parameters should be reset.
Warnings. The default RS232 profile described above does not support
hardware flow control.
2.3.3 Support Separate Management Plane IP Interfaces
Requirement. The device MAY provide designated network interface(s)
that are used for management plane traffic.
Justification. A separate management plane interface allows
management traffic to be segregated from other traffic (data/
forwarding plane, control plane). This reduces the risk that
unauthorized individuals will be able to observe management
traffic and/or compromise the device.
This requirement applies in situations where a separate OoB
management network exists.
Examples. This requirement may be satisfied, for example, with a
predefined Ethernet port dedicated to management and isolated from
customer traffic.
Warnings. The use of this type of interface depends on proper
functioning of both the operating system and the IP stack, as well
as good, known configuration at least on the portions of the
device dedicated to management. To talk to an ethernet interface
for management, you must know, for instance, it's IP address.
Jones, Editor Expires April 24, 2004 [Page 11]
Internet-Draft Operational Security Requirements October 2003
2.3.4 No Forwarding Between Management Plane And Other Interfaces
Requirement. If the device implements separate network interface(s)
for the management plane per Section 2.3.3 then the device MUST
not forward traffic between the management plane and
non-management plane interfaces.
Justification. This prevents the flow, intentional or unintentional,
of management traffic to/from places that it should not be
originating/terminating (e.g. anything beyond the customer-facing
interfaces).
Examples. This requirement may be satisfied by implementing separate
forwarding tables for management plane and non-management plane
interfaces that do not propagate routes to each other.
Warnings. None.
2.3.5 Provide Separate Resources For The Management Plane
Requirement. If the device implements separate network interface(s)
for the management plane per Section 2.3.3 then the device SHOULD
provide separate resources and use separate software for different
classes of interface.
Justification. The use of separate resources and system software
allows for fault isolation and increased reliability. If
something (a hacker sending a DoS flood or exercising a buffer
overrun) takes out the forwarding plane, the management plane is
likely to keep working, which will facilitate recovery.
Likewise, if something causes the management plane to stop
working, it is possible that the forwarding plane will keep doing
its job (forwarding packets).
Examples. Resources which should be separate include hardware
(memory, processor), data (forwarding table), and software (OS, IP
stack).
Warnings. None.
2.4 Configuration and Management Interface Requirements
This section lists requirements that document current best practice
in device configuration and management methods. In most cases, this
currently involves some sort of command line interface (CLI) and
configuration files. It may be possible in the future to meet the
Jones, Editor Expires April 24, 2004 [Page 12]
Internet-Draft Operational Security Requirements October 2003
individual requirements via other mechanisms, specifically via
mechanisms currently (October 2003) being defined by the IETF netconf
working group [netconf].
2.4.1 CLI Provides Access to All Configuration and Management Functions
Requirement. The Command Line Interface (CLI) or equivalent MUST
allow complete access to all configuration and management
functions.
Justification. Restricted or incomplete access to configuration or
management functions may make it impossible to perform necessary
tasks.
Examples. Examples of configuration include setting interface
addresses, defining and applying filters, configuring logging and
authentication, etc. Examples of management functions include
displaying dynamic state information such as CPU load, memory
utilization, packet processing statistics, etc.
Warnings. None.
2.4.2 CLI Uses Existing Authentication Mechanisms
Requirement. The CLI or equivalent MUST utilize existing
authentication methods.
Justification. The use of existing authentication methods keeps the
implementation simple and avoids needless complexity.
Examples. If a CLI function requires authentication functions and a
remote AAA (TACACS+, RADIUS, etc.) server is in use, then the CLI
should be able to use that server of authentication.
Warnings. None.
2.4.3 CLI Supports Scripting of Configuration
Requirement. The CLI or equivalent MUST support external scripting of
configuration functions. The scripting capability MUST NOT
require the use of a particular scripting language.
Justification. Scripting is necessary when the number of managed
devices is large and/or when changes must be implemented quickly.
The ability to script configuration functions provides operators
with the ability to implement solutions to problems not foreseen
Jones, Editor Expires April 24, 2004 [Page 13]
Internet-Draft Operational Security Requirements October 2003
or addressed by the vendor.
Examples. Example uses of scripting include: tracking an attack
across a large network, updating authentication parameters,
updating logging parameters, updating filters, configuration
fetching/auditing etc. Some languages that are currently used for
scripting include expect, Perl and TCL. Some properties of the
command language that enhance the ability to script are:
simplicity, regularity and consistency.
Warnings. None.
2.4.4 CLI Supports Management Over 'Slow' Links
Requirement. The device MUST support a command line interface (CLI)
or equivalent mechanism that works over low bandwidth connections
Justification. There are situations where high bandwidth for
management is not available, for example when in-band connections
are overloaded during an attack or when low-bandwidth, out-of-band
connections such as modems must be used... and it is often under
these conditions that it is most crucial to be able to perform
management and configuration functions.
Examples. The network is down. The network engineer just disabled
routing by mistake on the sole gateway router in a remote unmanned
data center. The only access to the device is over a modem
connected to a console port. The data center customers are
starting to call the support line. The GUI management interface is
redrawing the screen multiple times...slowly... at 9600bps.
Warnings. One consequence of this requirement may be that requiring a
GUI interface for management is unacceptable unless it can be show
to work acceptably over slow links.
2.4.5 Support Software Installation
Requirement. The device MUST provide a means to install new software
versions. It MUST be possible to install new software while the
device is disconnected from all public IP networks. This MUST NOT
rely on previous installation and/or configuration.
Justification.
* Vulnerabilities are often discovered in the base software
(operating systems, etc.) shipped by vendors. Often mitigation
Jones, Editor Expires April 24, 2004 [Page 14]
Internet-Draft Operational Security Requirements October 2003
of the risk presented by these vulnerabilities can only be
accomplished by updates to the vendor supplied software (e.g.
bug fixes, new versions of code, etc.). Without a mechanism to
load new vendor supplied code, it may not be possible to
mitigate the risk posed by these vulnerabilities.
* It is also conceivable that malicious behavior on the part of
hackers or unintentional behaviors on the part of operators
could cause software on devices to be corrupted or erased. In
these situations, it is necessary to have a means to (re)load
software onto the device to restore correct functioning.
* It is important to be able to load new software while
disconnected from all public IP networks because the device may
be vulnerable to old attacks before the update is complete.
Examples.
RS-232 The device could support uploading new code via an RS232
console port.
CD-ROM The device could support installing new code from a locally
attached CD-ROM drive.
NETWORK The device could support installing new code via a network
interface, assuming that (a) it is disconnected from all public
networks and (b) the device can boot an OS and IP stack from
some read-only media with sufficient capabilities to load new
code from the network.
Warnings. None.
2.4.6 Support Remote Configuration Backup
Requirement. The device MUST provide a means to store the system
configuration to a remote server. The stored configuration MUST
have sufficient information to restore the device to its
operational state at the time the configuration is saved.
Justification. Archived configurations are essential to enable
auditing and recovery.
Examples. Possible implementations include SCP, SFTP or FTP over a
secure channel. See Section 2.1.1 for requirements related to
secure communication channels for management protocols and data.
Jones, Editor Expires April 24, 2004 [Page 15]
Internet-Draft Operational Security Requirements October 2003
Warnings. The security of the remote server is assumed, with
appropriate measures being outside the scope of this document.
2.4.7 Support Remote Configuration Restore
Requirement. The device MUST provide a means to restore a
configuration that was saved as described in Section 2.4.6. The
system MUST be restored to its operational state at the time the
configuration was.
Justification. Restoration of archived configurations allows quick
restoration of service following an outage (security related as
well as from other causes).
Examples. Configurations may be restored using SCP, SFTP or FTP over
a secure channel. See Section 2.1.1 for requirements related to
secure communication channels for management protocols and data.
Warnings. The security of the remote server is assumed, with
appropriate measures being outside the scope of this document.
2.4.8 Support Human-Readable Configuration File
Requirement. The device MUST provide a means to remotely save a copy
of the system configuration file(s) in a human-readable form. It
MUST NOT be necessary to use a proprietary program to view the
configuration. The configuration MUST also be viewable in human
readable form on the device itself.
Justification. Having configurations in human-readable format is
necessary to enable off-line audits of the system configuration.
Having them in simple, non-proprietary formats also facilitates
automation of configuration checking.
Examples. A simple text-based configuration file would satisfy this
requirement.
Warnings. Offline copies of configurations should be well protected
as they often contain sensitive information such as SNMP community
strings, passwords, network blocks, customer information, etc.
2.5 IP Stack Requirements
Jones, Editor Expires April 24, 2004 [Page 16]
Internet-Draft Operational Security Requirements October 2003
2.5.1 Ability to Identify All Listening Services
Requirement. The vendor MUST:
* Provide a means to display all services that are listening for
network traffic directed at the device from any external
source.
* Display the interfaces on which each service is listening.
* Include both open standard and vendor proprietary services.
Justification. This information is necessary to enable a thorough
assessment of the security risks associated with the operation of
the device (e.g., "does this protocol allow complete management of
the device without also requiring authentication, authorization,
or accounting"?). The information also assists in determining
what steps should be taken to mitigate risk (e.g., "should I turn
this service off "?)
Examples. If, for example, the device is listening for SNMP on all
interfaces, then this requirement could be met by the provision of
a command which displays that fact.
Warnings. None.
2.5.2 Ability to Disable Any and All Services
Requirement. The device MUST provide a means to turn off any external
services listening.
Justification. The ability to disable services for which there is no
operational need will allow administrators to reduce the overall
risk posed to the device.
Examples. Processes that listen on TCP and UDP ports would be prime
examples of services that it must be possible to disable.
Warnings. None.
2.5.3 Listening Services Should Be Off By Default
Requirement. Services that cause the device to listen for traffic
destined for itself SHOULD be off by default. The user SHOULD
have to take explicit actions to enable any such services.
Jones, Editor Expires April 24, 2004 [Page 17]
Internet-Draft Operational Security Requirements October 2003
Justification. Open ports have the potential to expose
vulnerabilities. The user, not the vendor, should decide which
services are required and what risks to accept. This will also
prevent systems from being compromised through the misuse of
services which the user was unaware were enabled.
Examples. If the device supports SSH, HTTP, telnet and SNMP, in the
default configuration they should all be disabled.
Warnings. None.
2.5.4 Ability to Control Service Bindings for Listening Services
Requirement. The device MUST provide a means for the user to specify
the bindings used for all listening services. It MUST support
binding to a list of addresses and netblocks and SHOULD support
configuration of binding services to particular interfaces,
including loopback addresses.
Justification. This greatly reduces the need for complex filters. It
reduces the number of ports listening, and thus the number of
potential avenues of attack. It ensures that only traffic
arriving from legitimate addresses and/or on designated interfaces
can access services on the device.
Examples. If the device listens for inbound SSH connections, this
requirement means that it should be possible to specify that the
device will only listen to connections destined to specific
addresses (e.g. the address of the loopback interface) or received
on certain interfaces (e.g. an ethernet interface designated as
the "management" interface). It should be possible in this example
to configure the device such that the SSH is NOT listening on
every interface or to every address configured on the device.
Warnings. None.
2.5.5 Ability to Control Service Source Address
Requirement. The device MUST provide a means that allows the user to
specify the source address used for all outbound connections or
transmissions originating from the device. It MUST be possible to
specify source addresses independently for each type of outbound
connection or transmission. Source addresses MUST be limited to
addresses that are assigned to interfaces (including loopbacks)
local to the device.
Jones, Editor Expires April 24, 2004 [Page 18]
Internet-Draft Operational Security Requirements October 2003
Justification. This allows remote devices receiving connections or
transmissions to use source filtering as one means of
authentication. For example, if SNMP traps were configured to use
a known loopback address as their source, the SNMP workstation
receiving the traps (or a firewall in front of it) could be
configured to receive SNMP packets only from that address.
Examples. None.
Warnings. None.
2.5.6 Support Automatic Anti-spoofing for Single-Homed Networks
Requirement. The device MUST provide a means to designate particular
interfaces as servicing single-homed networks and MUST provide an
option to automatically apply anti-spoofing to such interfaces.
This option MUST work in the presence of dynamic routing and
dynamically assigned addresses. It MUST NOT negatively impact
performance. It MUST provide accurate counts of spoofed packets
that were dropped with logging options. It SHOULD be possible to
apply the option to an interface with a single command. For the
purposes of this requirement a "single-homed network" is defined
as one for which
* There is only one (logical) upstream connection
* Routing is symmetric
A "spoofed packet" is defined as a "packet having a source address
that, by application of the current forwarding tables, would not
have its return traffic routed back through the interface on which
it was received."
Justification. See [RFC2867] Network Ingress Filtering.
Examples. This requirement could be satisfied in several ways. It
could be satisfied by the provision of a single command that
automatically generates and applies filters to an interface that
implements anti-spoofing. It could be satisfied by the provision
of a command that causes the return path for packets received to
be checked against the current routing tables and dropped if they
would not be forwarded back through the interface on which they
were received.
Warnings. None.
Jones, Editor Expires April 24, 2004 [Page 19]
Internet-Draft Operational Security Requirements October 2003
2.5.7 Directed Broadcasts Disabled by Default
Requirement. The default configuration of the device MUST ensure
that:
* It will not respond to any directed broadcasts to any broadcast
domains of which it is a member.
* It will not propagate any directed broadcasts to any broadcast
domains to which it is directly connected.
There SHOULD be a mechanism to re-enable directed broadcasts on a
per-interface basis.
Justification. Directed broadcasts have few legitimate uses in modern
networks and are easily abused to amplify denial of service
attacks (e.g., SMURF attacks). [RFC2644] recommends the same
change in default settings as a Best Current Practice.
Examples. None.
Warnings. The requirement is in violation of [RFC1812].
2.6 Rate Limiting Requirements
2.6.1 Support Rate Limiting
Requirement. The device MUST provide the capability to limit the rate
at which it will pass traffic based on protocol, port, and
interface: and to rate-limit input and/or output separately on
each interface. It SHOULD allow filtering on any protocol and
MUST allow filtering on at least IP, ICMP, UDP, and TCP. This
feature SHOULD be implemented with minimal impact to system
performance.
Justification. This requirement provides a means of reducing or
eliminating the impact of certain types of attacks.
Examples. Assume that a web hosting company provides space in its
data-center to a company that becomes unpopular with a certain
element of network users, who then decide to flood the web server
with inbound ICMP traffic. It would be useful in such a situation
to be able to rate-filter inbound ICMP traffic at the
data-center's border routers. On the other side, assume that a
new worm is released that infects vulnerable database servers such
that they then start spewing traffic on TCP port 1433 aimed at
random destination addresses as fast as the system and network
Jones, Editor Expires April 24, 2004 [Page 20]
Internet-Draft Operational Security Requirements October 2003
interface of the infected server is capable. Further assume that
a data center has many vulnerable servers that are infected and
simultaneously sending large amounts of traffic with the result
that all outbound links are saturated. Implementation of this
requirement, would allow the network operator to rate limit
inbound and/or outbound TCP 1433 traffic (possibly to a rate of 0
packets/bytes per second) to respond to the attack and maintain
service levels for other legitimate customers/traffic.
Warnings. None.
2.6.2 Support Rate Limiting Based on State
Requirement. For stateful protocols it SHOULD be possible to rate
limit traffic based on session state.
Justification. This allows appropriate response to certain classes of
attack.
Examples. For example, for TCP sessions, it should be possible to
rate limit based on the SYN, SYN-ACK, RST, or other bit state.
Warnings. None.
2.7 Basic Filtering Capabilities
2.7.1 Ability to Filter Traffic
Requirement. The device MUST provide a means to filter IP packets on
any interface implementing IP.
In this document a "filter" is defined as a group of one or more
rules where each rule specifies one or more match criteria as
specified in Section 2.8.
Also see the specific filtering requirements that follow this one.
Justification. Packet filtering is important because it provides a
basic means of implementing policies that specify which traffic is
allowed and which is not. It also provides a basic tool for
responding to malicious traffic.
Examples. Access control lists that allow filtering based on protocol
and/or source/destination address and or source/destination port
would be one example.
Jones, Editor Expires April 24, 2004 [Page 21]
Internet-Draft Operational Security Requirements October 2003
Warnings. None.
2.7.2 Ability to Filter Traffic TO the Device
Requirement. It MUST be possible to apply the filtering mechanism to
traffic that is addressed directly to the device via any of its
interfaces - including loopback interfaces.
Justification. This is important because it allows filters to be
applied that protect the device itself from attacks and
unauthorized access.
Examples. Examples of this might include filters that permit only
SNMP and SSH traffic from an authorized management segment
directed to the device itself, while dropping all other traffic
addressed to the device.
Warnings. None.
2.7.3 Ability to Filter Traffic THROUGH the Device
Requirement. It MUST be possible to apply the filtering mechanism to
traffic that is being routed (switched) through the device.
Justification. This is important because it permits implementation of
basic policies on devices that carry transit traffic (routers,
switches, firewalls, etc.).
Examples. One simple and common way to meet this requirement is to
provide the ability to filter traffic inbound to each interface
and/or outbound from each interface. Ingress filtering as
described in [RFC2827] provides one example of the use of this
capability.
Warnings. None.
2.7.4 Ability to Filter Without Performance Degradation
Requirement. The device MUST provide a means to filter packets
without performance degradation. The device MUST be able to filter
on ALL interfaces (up to the maximum number possible)
simultaneously and with multiple filters per interface (e.g.,
inbound and outbound).
Jones, Editor Expires April 24, 2004 [Page 22]
Internet-Draft Operational Security Requirements October 2003
Justification. This is important because it enables the
implementation of filtering wherever and whenever needed. To the
extent that filtering causes degradation, it may not be possible
to apply filters that implement the appropriate policies.
Examples. Another way of stating the requirement is that filter
performance should not be the limiting factor in device
throughput. If a device is capable of forwarding, say, 30Mb/sec
without filtering, then it should be able to forward the same
amount with filtering in place. This requirement most likely
implies a hardware-based solution (ASIC).
Warnings. Without hardware based filtering, it may be possible for
the implementation of filters to degrade the performance of the
device or to cause it to cease functioning.
2.7.5 Ability to Filter Updates
Requirement. The device MUST provide a means to filter updates for
all protocols that could be used to update operational
characteristics of the device. Note that it MUST be possible to
specify a filter that disables all updates.
This requirement MAY be satisfied through the use of filters as
described in Section 2.7.1 and/or with mechanisms specific to each
protocol. Also note that update filtering is required in addition
to secure channels (Section 2.1.1) and authentication (Section
2.12)
Justification. Without the ability to filter protocols used for
management and operational updates, unauthorized users might be
able to change operational parameters (e.g., routing tables,
passwords, etc.) and/or completely disable the device.
Examples. This should include the ability to:
* Filter routing protocol updates
* Disable SNMP writing completely
* Filter addresses permitted to manage the device regardless of
protocol (SNMP,SSH,TELNET,HTTP,TFTP,SNMP...)
Warnings. None.
Jones, Editor Expires April 24, 2004 [Page 23]
Internet-Draft Operational Security Requirements October 2003
2.7.6 Ability to Specify Filter Actions
Requirement. The device MUST provide a mechanism to allow the
specification of the action to be taken when a filter rule
matches. Actions must include "permit" (allow the traffic),
"reject" (drop with appropriate notification to sender), and
"drop" (drop with no notification to sender). Also see Section
2.7.7 and Section 2.9
Justification. This capability is essential to the use of filters to
enforce policy.
Examples. Assume that you have a small DMZ network connected to the
Internet. You want to allow management using SSH coming from your
corporate office. In this case, you might "permit" all traffic to
port 22 in the DMZ from your corporate network, "rejecting" all
others. Port 22 traffic from the corporate network is allowed
through. Port 22 traffic from all other addresses results in an
ICMP message to the sender. For those who are slightly more
paranoid, you might choose to "drop" instead of "reject" traffic
from unauthorized addresses, with the result being that *nothing*
is sent back to the source.
Warnings. [Ed. Does "drop" with no ICMP unreachable violate any RFCs
?]
2.7.7 Ability to Log Filter Actions
Requirement.
It MUST be possible to log all filter actions. The logging
capability MUST be able to capture at least the following data:
permit/deny/drop status, source and destination ports, source and
destination IP address, which network element forwarded the packet
(interface, MAC address or other layer 2 information that
identifies the previous hop source of the packet), and time-stamp
to millisecond accuracy.
Logging of filter actions is subject to the requirements of
Section 2.11.
Justification. Logging is essential for auditing, incident response,
and operations.
Examples. A desktop network may not provide any services that should
be accessible from "outside." In such cases, all inbound
connection attempts should be logged as possible intrusion
Jones, Editor Expires April 24, 2004 [Page 24]
Internet-Draft Operational Security Requirements October 2003
attempts.
Warnings. None.
2.8 Packet Filtering Criteria
2.8.1 Ability to Filter on Protocols
Requirement. The device MUST provide a means to filter traffic based
on protocol.
Justification. Being able to filter on protocol is necessary to allow
implementation of policy, secure operations and for support of
incident response.
Examples. Some denial of service attacks are based on the ability to
flood the victim with ICMP traffic. One quick way (admittedly
with some negative side effects) to mitigate the effects of such
attacks is to drop all ICMP traffic headed toward the victim.
Warnings. None.
2.8.2 Ability to Filter on Addresses
Requirement. The function MUST be able to control the flow of traffic
based on source and/or destination IP address or blocks of
addresses such as Classless Inter-Domain Routing (CIDR) blocks.
Justification. The capability to filter on addresses and address
blocks is a fundamental tool for establishing boundaries between
different networks.
Examples. One example of the use of address based filtering is to
implement ingress filtering per [RFC2827].
Warnings. None.
2.8.3 Ability to Filter on Any Protocol Header Fields
Requirement. The filtering mechanism MUST support filtering based on
the value(s) of any portion of the protocol headers.
Justification. Being able to filter on portions of the header is
necessary to allow implementation of policy, secure operations,
and support incident response.
Jones, Editor Expires April 24, 2004 [Page 25]
Internet-Draft Operational Security Requirements October 2003
Examples. For example, this requirement implies that it is possible
to filter based on TCP or UDP port numbers, TCP flags such as SYN,
ACK and RST bits, and ICMP type and code fields. One common
example is to reject "inbound" TCP connection attempts (TCP, SYN
bit set). Another common example is the ability to control what
services are allowed in/out of a network. For example, it may be
desirable to only allow inbound connections on port 80 (HTTP) and
443 (HTTPS) to a network hosting web servers.
Warnings. None.
2.8.4 Ability to Filter Inbound and Outbound
Requirement. It MUST be possible to filter both incoming and outgoing
traffic on any interface.
Justification. This requirement allows flexibility in applying
filters at the place that makes the most sense. It allows invalid
or malicious traffic to be dropped as close to the source as
possible.
Examples. It might be desirable on a border router, for example, to
apply an egress filter outbound on the interface that connects a
site to its external ISP to drop outbound traffic that does not
have a valid internal source address. Inbound, it might be
desirable to apply a filter that blocks all traffic from a site
that is known to forward or originate lots of junk mail.
Warnings. None.
2.9 Packet Filtering Counter Requirements
2.9.1 Ability to Accurately Count Filter Hits
Requirement. The device MUST supply a facility for accurately
counting all filter hits.
Justification. Accurate counting of filter rule matches is important
because it shows the magnitude/frequency of attempts to violate
policy. This enables resources to be focused on areas of greatest
need.
Examples. Assume, for example, that a ISP network implements
anti-spoofing egress filters (see [RFC2827]) on interfaces of its
edge routers that support single-homed stub networks. Counters
could enable the ISP to detect cases where large numbers of
Jones, Editor Expires April 24, 2004 [Page 26]
Internet-Draft Operational Security Requirements October 2003
spoofed packets are being sent. This may indicate that the
customer is performing potentially malicious actions (possibly in
violation of the IPS's Acceptable Use Policy), or that system(s)
on the customers network have been "owned" by hackers and are
being (mis)used to launch attacks.
Warnings. None.
2.9.2 Ability to Display Filter Counters
Requirement. The device MUST provide a mechanism to display filter
counters.
Justification. Information that is collected is not useful unless it
can be displayed in a useful manner.
Examples. Assume there is a router with four interfaces. One is an
up-link to an ISP providing routes to the Internet. The other
three connect to separate internal networks. Assume that a host
on one of the internal networks has been compromised by a hacker
and is sending traffic with bogus source addresses. In such a
situation, it might be desirable to apply ingress filters to each
of the internal interfaces. Once the filters are in place, the
counters can be examined to determine the source (inbound
interface) of the bogus packets.
Warnings. None.
2.9.3 Ability to Display Filter Counters per Rule
Requirement. The device MUST provide a mechanism to display filter
counters per rule.
Justification. This makes it possible to see which rules are matching
and how frequently.
Examples. Assume that a filter has been defined that has two rules,
one permitting all SSH traffic (tcp/22) and the second dropping
all remaining traffic. If three packets are directed toward/
through the point at which the filter is applied, one to port 22,
the others to different ports, then the counter display should
show 1 packet matching the permit tcp/22 rule and 2 packets
matching the deny all others rule.
Jones, Editor Expires April 24, 2004 [Page 27]
Internet-Draft Operational Security Requirements October 2003
Warnings. None.
2.9.4 Ability to Display Filter Counters per Filter Application
Requirement. If it is possible for a filter to be applied more than
once at the same time, then the device MUST provide a mechanism to
display filter counters per filter application.
Justification. It may make sense to apply the same filter definition
simultaneously more than one time (to different interfaces, etc.).
If so, it would be much more useful to know which instance of a
filter is matching than to know that some instance was matching
somewhere.
Examples. One way to implement this requirement would be to have the
counter display mechanism show the interface (or other entity) to
which the filter has been applied, along with the name (or other
designator) for the filter. For example if a filter named
"desktop_outbound" applied two different interfaces, say,
"ethernet0" and "ethernet1," the display should indicate something
like "matches of filter 'desktop_outbound' on ethernet0 ..." and
"matches of filter 'desktop_outbound' on ethernet1 ..."
Warnings. None.
2.9.5 Ability to Reset Filter Counters
Requirement. It MUST be possible to reset counters to zero on a per
filter basis.
Justification. This allows operators to get a current picture of the
traffic matching particular rules/filters.
Examples. Assume that filter counters are being used to detect
internal hosts that are infected with a new worm. Once it is
believed that all infected hosts have been cleaned up and the worm
removed, the next step would be to verify that. One way of doing
so would be to reset the filter counters to zero and see if
traffic indicative of the worm has ceased.
Warnings. None.
2.9.6 Filter Counters Must Be Accurate
Jones, Editor Expires April 24, 2004 [Page 28]
Internet-Draft Operational Security Requirements October 2003
Requirement. Filter counters MUST be accurate. They MUST reflect
the actual number of matching packets since the last counter
reset.
Justification. Inaccurate data can not be relied on as the basis for
action. Underreported data can conceal the magnitude of a problem.
Examples. If N packets matching a filter are sent to/through a
device, then the counter should show N matches.
Warnings. None.
2.10 Other Packet Filtering Requirements
2.10.1 Filter, Counters, and Filter Log Must Have Minimal Performance
Impact
Requirement. Filtering, logging, and counting functionality MUST be
implemented such that they have minimal impact on performance.
Justification. The possibility of severe performance degradation in
the use of filtering, logging, or counting would reduce their
utility. Fear of adverse operational consequences might cause
operators to limit or discard their use completely in situations
where they are needed.
Examples.
Assume, for example, that a new worm is released that scans random
IP addresses looking for services listening on TCP port 1433. An
operator might want to investigate to see if any of the hosts on
their networks were infected and trying to spread the worm. One
way to do this would be to put up non-blocking filters counting
and logging the number of outbound connection 1433, and then to
block the requests that are determined to be from infected hosts.
If any of these capabilities (filtering, counting, logging) have
the potential to impose severe performance penalties, then this
otherwise rational course of action might not be possible.
Some examples of things that would make the logging features
unusable might include situations where their use:
* crashes the device
* consumes excessive resources (CPU, memory, bandwidth)
* makes the device unmanageable
Jones, Editor Expires April 24, 2004 [Page 29]
Internet-Draft Operational Security Requirements October 2003
* causes the loss of data
Warnings.
While there are some objective measures that indicate clearly when
a feature is unusable (its use crashes the device), "usability" is
largely a subjective term. Lab tests may be constructed to
determine how well the device behaves under certain loads, but the
ultimate test of usability for filtering, counting and logging
will come under live, quite possibly heavy, loads.
2.10.2 Ability to Specify Filter Log Granularity
Requirement. It MUST be possible to enable/disable logging on a per
rule basis.
Justification. The ability to tune the granularity of logging allows
the operator to log only the information that is desired. Without
this capability, it is possible that extra data (or none at all)
wold be logged, making it more difficult to find relevant
information.
Examples. If a filter is defined that has several rules, and one of
the rules denies telnet (tcp/23) connections, then it should be
possible to specify that only matches on the rule that denies
telnet should generate a log message.
Warnings. None.
2.11 Event Logging Requirements
2.11.1 Logging Facility Conforms to Open Standards
Requirement. The device MUST provide a logging facility that conforms
to open standards. Custom/Proprietary log protocols MAY be
implemented provided the same information is made available via
logging facilities that conform to open standards.
Justification. The use of open standards logging is important because
it permits the customer to perform archival and analysis of logs
without relying on vendor-supplied software and servers.
Examples. [RFC3195] meets this requirement. The use of SNMP traps may
also satisfy this requirement.
Jones, Editor Expires April 24, 2004 [Page 30]
Internet-Draft Operational Security Requirements October 2003
Warnings. While [RFC3164] and SNMP may satisfy this requirement, they
both fail to satisfy several other logging requirements.
2.11.2 Ability to Log to Remote Server
Requirement. The device MUST be capable of logging to a remote
server. It SHOULD be able to log to multiple servers.
Justification. External logging allows the storage of large,
persistent logs that may not be possible with local (on the
device) logging.
Examples. One example of a remote log server would be a host running
a syslog server. See [RFC3164].
Warnings. High volumes of logging may generate excessive network
traffic and/or compete for scarce memory and CPU resources on the
device.
2.11.3 Ability to Log Locally
Requirement.
It SHOULD be possible to log locally on the device itself.
Justification. Local logging is important for viewing information
when connected to the device. It provides some backup of log data
in case remote logging fails. It provides a way to view logs
relevant to one device without having to sort through a possibly
large set of logs from other devices.
Examples. One example of local logging would be a memory buffer that
receives copies of messages sent to the remote log server.
Another example might be a local syslog server (assuming the
device is capable of running syslog and has some local storage).
Warnings. Storage on the device may be limited. High volumes of
logging may quickly fill available storage, in which case there
are two options: new logs overwrite old logs (possibly via the use
of a circular memory buffer or log file rotation), or logging
stops.
2.11.4 Ability to Maintain Accurate System Time
Jones, Editor Expires April 24, 2004 [Page 31]
Internet-Draft Operational Security Requirements October 2003
Requirement. The device MUST maintain accurate, high resolution
system time. All displays of system time MUST include a timezone.
The default timezone SHOULD be UTC or GMT. The device SHOULD
support a mechanism to allow the operator to specify the timezone
for local system time.
Justification. This is important because the system clock is used for
time-stamping log messages.
Examples. This requirement may be satisfied by supporting Network
Time Protocol (NTP), Simple Network Time Protocol (SNTP), or via
direct connection to an accurate time source. See Section 2.1.1
for requirements related to secure communication channels for
management protocols and data.
Warnings. System clock chips are inaccurate to varying degrees.
System time should not be relied upon unless it is regularly
checked and synchronized with a known, accurate external time
source (such as an NTP stratum-1 server). Also note that if
network time synchronization is used, an attacker may be able to
manipulate the clock unless cryptographic authentication is used.
2.11.5 Logs Must Be Timestamped
Requirement. The device MUST time-stamp all log messages. The
time-stamp MUST be accurate to within a second or less. The
time-stamp MUST include a timezone.
Justification. This is important because accurate timestamps are
necessary for correlating events, particularly across multiple
devices or with other organizations. This applies when it is
necessary to analyze logs.
Examples. This requirement MAY be satisfied by writing timestamps
into syslog messages.
Warnings. It is difficult to correlate logs from different time
zones. Security events on the Internet often involve machines and
logs from a variety of physical locations. For that reason, UTC
is preferred, all other things being equal.
2.11.6 Logs Contain Untranslated Addresses
Requirement. Log messages MUST contain relevant IP addresses.
Jones, Editor Expires April 24, 2004 [Page 32]
Internet-Draft Operational Security Requirements October 2003
Justification. It is important to include IP address of access list
violation logs, authentication attempts. This enables a level of
individual and organizational accountability and is necessary to
enable analysis of network events, incidents, policy violations,
etc.
Examples. None.
Warnings.
* Source addresses may be spoofed. Network-based attacks often
use spoofed source addresses. Source addresses should not be
completely trusted unless verified by means.
* Addresses may be reassigned to different individual, for
example, in a desktop environment using DHCP. In such cases the
individual accountability afforded by this requirement is weak.
* Network topologies may change. Even in the absence of dynamic
address assignment, network topologies and address block
assignments do change. Logs of an attack one month ago may not
give an accurate indication of which host, network or
organization owned the system(s) in question at the time.
2.12 Authentication, Authorization, and Accounting (AAA) Requirements
2.12.1 Authenticate All User Access
Requirement. The device MUST provide a facility to perform
authentication of all user access to the system.
Justification. This functionality is required so that access to the
system can be restricted to authorized personnel.
Examples. This requirement MAY be satisfied by implementing a
centralized authentication system. See Section 2.12.5. It MAY
also be satisfied using local authentication. See Section 2.12.6
Warnings. None.
2.12.2 Support Authentication of Individual Users
Requirement. Each authentication mechanism supported by the device
MUST support the authentication of distinct, individual users.
Jones, Editor Expires April 24, 2004 [Page 33]
Internet-Draft Operational Security Requirements October 2003
Justification. The use of individual accounts, in conjunction with
logging, promotes accountability. The use of group or default
accounts undermines individual accountability.
Examples. The implementation depends on the types of authentication
supported by the device. Local usernames and passwords are one
possibility. Centralized authentication servers using usernames
and onetime passwords is another.
Warnings. This simply requires that the mechanism to support
individual users be present. Policy (e.g., forbidding shared
group accounts) and enforcement are also needed but beyond the
scope of this document.
2.12.3 Support Simultaneous Connections
Requirement. The device SHOULD support multiple simultaneous
connections by distinct users, possibly at different authorization
levels.
Justification. This allows multiple people to perform authorized
management functions simultaneously.
Examples. None.
Warnings. None.
2.12.4 Ability to Disable All Local Accounts
Requirement. The device MUST provide a means of disabling all local
accounts including:
* Local users
* Default accounts (vendor, maintenance, guest...)
* Privileged and unprivileged accounts
Justification. Default accounts, well-know accounts, and old accounts
provide easy targets for someone attempting to gain access to a
device. It must be possible to disable them to reduce the
potential vulnerability.
Examples. The implementation depends on the types of authentication
supported by the device.
Jones, Editor Expires April 24, 2004 [Page 34]
Internet-Draft Operational Security Requirements October 2003
Warnings. None.
2.12.5 Support Centralized User Authentication Methods
Requirement. The device MUST support a method of centralized
authentication of all user access via standard authentication
protocols.
Justification. Support for centralized authentication is particularly
important in large environments where the network devices are
widely distributed and where many people have access to them. This
reduces the effort needed to effectively restrict and track access
to the system by authorized personnel.
Examples. Terminal Access This requirement can be satisfied through
the use of Terminal Controller Access Control System Plus
(TACACS+), Remote Authentication Dial-In User Service (RADIUS), or
Kerberos. See Section 2.1.1 for requirements related to secure
communication channels for management protocols and data.
Warnings. None.
2.12.6 Support Local User Authentication Method
Requirement. The device SHOULD support a local authentication method.
If implemented, the method MUST NOT require interaction with
anything external to the device (such as remote AAA servers), and
MUST work in conjunction with Section 2.3.1 (Support a Non-IP
'Console' interface) and Section 2.12.7 (Support Configuration of
Order of Authentication Methods).
Justification. Support for local authentication may be required in
smaller environments where there may be only a few devices and a
limited number of people with access. The overhead of maintaining
centralized authentication servers may not be justified.
Examples. The use of local, per-device usernames and passwords
provides one way to implement this requirement.
Warnings. Authentication information must be protected wherever it
resides. Having, for instance, local usernames and passwords
stored on 100 network devices means that there are 100 potential
points of failure where the information could be compromised vs.
storing authentication data centralized server(s), which would
reduce the potential points of failure to the number of servers
and allow protection efforts (system hardening, audits, etc.) to
Jones, Editor Expires April 24, 2004 [Page 35]
Internet-Draft Operational Security Requirements October 2003
be focused on, at most, a few servers.
2.12.7 Support Configuration of Order of Authentication Methods
Requirement. The device MUST support the ability to configure the
order in which supported authentication methods are attempted.
Authentication SHOULD "fail closed", i.e. access should be denied
if none of the listed authentication methods succeeds.
Justification. This allows the operator flexibility in implementing
appropriate security policies that balance operational and
security needs.
Examples. If, for example, a device supports RADIUS authentication
and local usernames and passwords, it should be possible to
specify that RADIUS authentication should be attempted if the
servers are available, and that local usernames and passwords
should be used for authentication only if the RADIUS servers are
not available. Similarly, it should be possible to specify that
only RADIUS or only local authentication be used.
Warnings. None.
2.12.8 No Unencrypted Transmission of Reusable Plain-text Passwords
Requirement. The device MUST perform authentication without the
unencrypted transmission of reusable plain-text passwords across a
network. The implementation:
* MUST NOT cause significant performance degradation
* MUST NOT require additional devices (e.g., encryption cards,
etc.)
* MUST scale well/be supportable on large numbers of devices
(e.g., the number of keys and configuration settings that need
to be managed should increase at most linearly as the number of
devices).
This requirement MAY be satisfied by tunneling protocols that use
plain-text passwords over secure channels per Section 2.1.1.
Justification. Reusable plain-text passwords can easily be observed
using packet sniffers on shared networks. Mechanisms that impose
too high of an overhead or are not manageable will not be used.
This requirement specifically precludes the use of reusable
Jones, Editor Expires April 24, 2004 [Page 36]
Internet-Draft Operational Security Requirements October 2003
passwords with standard telnet without being carried over a secure
channel (see Section 2.1.1) for device management. It does allow
the use of standard telnet with one time passwords. Note that this
does not preclude the use of extra hardware; it simply says that
additional hardware (smart cards, encryption cards, etc.) must not
be required to support authentication without the use of clear
text passwords. See [RFC1704] for a through discussion of the
issues.
Examples. None.
Warnings. None.
2.12.9 No Default Passwords
Requirement. The initial configuration of the device MUST NOT contain
any default passwords or similar static authentication tokens.
"Similar static authentication tokens" includes any form of shared
secret, public or private key.
Justification. Default passwords provide an easy way for attackers to
gain unauthorized access to the device.
Examples. Passwords such as the name of the vendor, device, "default"
etc. are easily guessed. The SNMP community strings "public" and
"private" are well known defaults that provide read and write
access to devices.
Warnings. Lists of default passwords for various devices are readily
available at numerous websites.
2.12.10 Passwords Must Be Explicitly Configured Prior To Use
Requirement. The device MUST require the operator to explicitly
configure passwords and similar static authentication tokens prior
to use. "Similar authentication tokens" includes any form of
shared secret, public or private key.
Justification. This requirement is intended to prevent unauthorized
management access. Requiring the operator to explicitly configure
passwords will tend to have the effect of ensuring a diversity of
passwords. It also shifts the responsibility for password
selection to the user.
Jones, Editor Expires April 24, 2004 [Page 37]
Internet-Draft Operational Security Requirements October 2003
Examples. Assume that a device comes with console port for management
and a default administrative account. This requirement together
with No Default Passwords says that the administrative account
should come with no password configured. One way of meeting this
requirement would be to have the device require the operator to
choose a password for the administrative account as part of a
dialog the first time the device is configured.
Warnings. While this device requires operators to set passwords, it
does not prevent them from doing things such as using scripts to
configure 100s of devices with the same easily guessed passwords.
2.12.11 Ability to Define Privilege Levels
Requirement. It MUST be possible to define arbitrary subsets of all
management and configuration functions and assign them to groups
or "privilege levels," which can be assigned to users per Section
2.12.12
Justification. This requirement supports the implementation of the
principal of "least privilege", which states that an individual
should only have the privileges necessary to execute the
operations he/she is required to perform.
Examples. Examples of privilege levels might include "default," which
allows read-only access to device configuration and operational
statistics, "root/superuser/administrator" which allows update
access to all configurable parameters, and "operator" which allows
updates to a limited, user defined set of parameters. Note that
privilege levels may be defined locally on the device or on
centralized authentication servers.
Warnings. None.
2.12.12 Ability to Assign Privilege Levels to Users
Requirement. The device MUST be able to assign a defined set of
authorized functions, or "privilege level," to each user once they
have authenticated themselves the device. Privilege level
determines which functions a user is allowed to execute. Also
see See Section 2.12.11.
Justification. This requirement supports the implementation of the
principal of "least privilege," which states that an individual
should only have the privileges necessary to execute the
operations he/she is required to perform.
Jones, Editor Expires April 24, 2004 [Page 38]
Internet-Draft Operational Security Requirements October 2003
Examples. The implementation of this requirement will obviously be
closely coupled with the authentication mechanism. So for
example, if RADIUS is used, an attribute could be set in the
user's RADIUS profile that can be used to map the ID to a certain
privilege level.
Warnings. None.
2.12.13 Default Privilege Level Must Be Read Only
Requirement. The default privilege level MUST only allow read access
to device settings and operational parameters.
Justification. This requirement supports the implementation of the
principal of "least privilege," which states that an individual
should only have the privileges necessary to execute the
operations he/she is required to perform.
Examples. None.
Warnings. None.
2.12.14 Change in Privilege Levels Requires Re-Authentication
Requirement. The device MUST re-authenticate a user prior to granting
any change in user authorizations.
Justification. This requirement insures that users are able to
perform only authorized actions.
Examples. This requirement might be implemented by assigning base
privilege levels to all users and allowing the user to request
additional privileges, with the requests validated by the AAA
server.
Warnings. None.
2.12.15 Support Recovery Of Privileged Access
Requirement. The device MUST support a mechanism to allow authorized
individuals to recover full privileged administrative access in
the event that access is lost. Use of the mechanism MUST require
physical access to the device. There MAY be a mechanism for
disabling the recovery feature.
Jones, Editor Expires April 24, 2004 [Page 39]
Internet-Draft Operational Security Requirements October 2003
Justification. There are times when local administrative passwords
are forgotten, when the only person who knows them leaves the
company, or when hackers set or change the password. In all
these cases, legitimate administrative access to the device is
lost. There should be a way to recover access. Requiring
physical access to invoke the procedure makes it less likely that
it will be abused. Some organizations may want an even higher
level of security and be willing to risk total loss of authorized
access by disabling the recovery feature, even for those with
physical access.
Examples. Some examples of ways to satisfy this requirement are to
have the device give the user the chance to set a new
administrative password when:
The user sets a jumper on the system board to a particular
position.
The user sends a special sequence to the RS232 console port
during the initial boot sequence.
The user sets a "boot register" to a particular value.
Warnings. This mechanism, by design, provides a "back door" to
complete administrative control of the device and may not be
appropriate for environments where those with physical access to
the device can not be trusted.
2.12.16 Accounting Records
Requirement. The device MUST be able to store a record of at least
the following events:
* Failed logins
* Successful logins
* All Commands executed by the user during their session,
including via the management/serial port and interactions with
an underlying OS (e.g., Unix "shell" commands)
* Change in privilege level
* All logouts
Jones, Editor Expires April 24, 2004 [Page 40]
Internet-Draft Operational Security Requirements October 2003
The device MUST support transmission of accounting records to one
or more remote devices. There MUST be configuration settings on
the device that allow selection of servers.
Justification. This is important because it supports individual
accountability by providing a record of changes that were made and
who made them. It is important to store them on a separate server
to preserve them in case of failure or compromise of the managed
device.
Examples. This requirement MAY be satisfied by the use of
RADIUS,TACACS+, or syslog. See Section 2.1.1 for requirements
related to secure communication channels for management protocols
and data.
Warnings. Syslog is known to be unreliable/lossy during network
transmission (due to use of UDP). It has also been observed that
some devices lose a significant number of UDP packets before they
are ever transmitted, due (apparently) to low prioritization of
the internal processing of UDP packets. Similar problems have
been observed in various syslog servers (syslogd on UNIX systems).
Bottom line: be aware that syslog data may be lost at one of
several points.
2.13 Layer 2 Devices Must Meet Higher Layer Requirements
Requirement. If a device provides layer 2 services that are dependent
on layer 3 or greater services, then the portions that operate at
or above layer 3 MUST conform to the requirements listed in this
document.
Justification. All layer 3 devices have similar security needs and
should be subject to similar requirements.
Examples. For example, signaling protocols required for layer 2
switching may exchange information with other devices using layer
3 communications. In such cases, the device must provide a secure
layer 3 facility. Also, if higher layer capabilities (say, SSH or
SNMP) are used to manage a layer 2 device, then the rest of the
requirements in this document apply to those capabilities.
Warnings. None.
Jones, Editor Expires April 24, 2004 [Page 41]
Internet-Draft Operational Security Requirements October 2003
3. Documentation Requirements
The requirements in this section are intended to list information
that will assist operators in evaluating and securely operating a
device.
3.1 Document Listening Services
Requirement. The vendor MUST:
* Provide a documented explanation for all network services that
may be active on the system.
* Concisely document which features enable listening ports on the
device.
* List which services are on by default.
This information MUST be provided in a single, contiguous section
of the documentation. This list MUST include both open standard
and vendor proprietary services.
Justification. This information is necessary to enable a thorough
assessment of the security risks associated with the operation of
the device (e.g., "does this protocol allow complete management of
the device without also requiring authentication, authorization,
or accounting"?). The information also assists in determining
what steps should be taken to mitigate risk (e.g., "should I turn
this service off "?)
Examples. This documentation should include at least a list of all
possible network services that could be activated to listen on any
TCP and/or UDP port, or any vendor-proprietary port/protocol.
Warnings. None.
Jones, Editor Expires April 24, 2004 [Page 42]
Internet-Draft Operational Security Requirements October 2003
4. Assurance Requirements
The requirements in this section are intended to
o identify behaviors and information that will increase confidence
that the device will meet the security functional requirements.
o Provide information that will assist evaluation
4.1 Comply With Relevant IETF RFCs on All Protocols Implemented
Requirement. The default configuration of the device MUST fully
comply with IETF RFCs for all protocols implemented. "Compliance"
is defined in terms of [RFC2119]. The device MUST conform to the
absolute requirements. Any optional or recommended functionality
implemented MUST be in conformance with the RFC. The device MAY
provide means by which it can be configured in ways that are not
compliant with the RFCs (for instance, if conformance is
determined to be insecure).
Justification. A device must first perform its primary function
correctly. Once it is proven to perform its primary function, it
makes sense to ask if it does/can perform securely. For Internet
connected devices, compliance with RFCs provides a minimum level
of assurance that the device will function as intended and
inter-operate as part of an operational network. Failure to
comply with RFCs calls correct functioning into question and makes
the determination of secure functioning a secondary concern.
Examples. Some of the relevant RFCs include:
ICMP.
[RFC0792] INTERNET CONTROL MESSAGE PROTOCOL
[RFC1812] Requirements for IP Version 4 Routers
IP.
[RFC0791] INTERNET PROTOCOL
[RFC0922] BROADCASTING INTERNET DATAGRAMS IN THE PRESENCE OF
SUBNETS
[RFC1812] Requirements for IP Version 4 Routers
Jones, Editor Expires April 24, 2004 [Page 43]
Internet-Draft Operational Security Requirements October 2003
[RFC1858] Security Considerations for IP Fragment Filtering
[RFC2644] Changing the Default for Directed Broadcasts in
Routers
[RFC2827] Network Ingress Filtering
TCP.
[RFC0793] TRANSMISSION CONTROL PROTOCOL
[RFC1858] Security Considerations for IP Fragment Filtering
[RFC1948] Defending Against Sequence Number Attacks
UDP.
[RFC0768] User Datagram Protocol
[RFC1122] Requirements for Internet Hosts -- Communication
Layers
[RFC1812] Requirements for IP Version 4 Routers
Warnings. None.
4.2 Identify Origin of IP Stack
Requirement. The vendor MUST disclose the origin or basis of the IP
stack used on the system.
Justification. This information is required to better understand the
possible security vulnerabilities that may be inherent in the IP
stack.
Examples. For example, "The IP stack was derived from BSD 4.4," or
"The IP stack was implemented from scratch."
Warnings. Many IP stacks make simplifying assumptions about how an IP
packet should be formed. A malformed packet can cause unexpected
behavior in the device, such as a system crash or buffer overflow
which could result in unauthorized access to the system.
4.3 Identify Origin of Operating System
Jones, Editor Expires April 24, 2004 [Page 44]
Internet-Draft Operational Security Requirements October 2003
Requirement. The vendor MUST disclose the origin or basis of the
operating system (OS).
Justification. This information is required to better understand the
security vulnerabilities that may be inherent to the OS based on
its origin.
Examples. For example, "The operating system is based on Linux kernel
2.4.18."
Warnings. None.
Jones, Editor Expires April 24, 2004 [Page 45]
Internet-Draft Operational Security Requirements October 2003
5. Security Considerations
Security is the subject matter of this entire memo. It might be more
appropriate to list operational considerations. Operational issues
are mentioned as needed in the examples and warnings sections of each
requirement.
Jones, Editor Expires April 24, 2004 [Page 46]
Internet-Draft Operational Security Requirements October 2003
References
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September
1981.
[RFC0792] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, September 1981.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC
793, September 1981.
[RFC0922] Mogul, J., "Broadcasting Internet datagrams in the
presence of subnets", STD 5, RFC 922, October 1984.
[RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, October 1989.
[RFC1704] Haller, N. and R. Atkinson, "On Internet Authentication",
RFC 1704, October 1994.
[RFC1812] Baker, F., "Requirements for IP Version 4 Routers", RFC
1812, June 1995.
[RFC1858] Ziemba, G., Reed, D. and P. Traina, "Security
Considerations for IP Fragment Filtering", RFC 1858,
October 1995.
[RFC1948] Bellovin, S., "Defending Against Sequence Number Attacks",
RFC 1948, May 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2644] Senie, D., "Changing the Default for Directed Broadcasts
in Routers", BCP 34, RFC 2644, August 1999.
[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, May 2000.
[RFC2867] Zorn, G., Aboba, B. and D. Mitton, "RADIUS Accounting
Modifications for Tunnel Protocol Support", RFC 2867, June
2000.
[RFC3164] Lonvick, C., "The BSD Syslog Protocol", RFC 3164, August
Jones, Editor Expires April 24, 2004 [Page 47]
Internet-Draft Operational Security Requirements October 2003
2001.
[RFC3195] New, D. and M. Rose, "Reliable Delivery for syslog", RFC
3195, November 2001.
[netconf] IETF, "Network Configuration Working Group", 2003, <http:/
/www.ietf.org/html.charters/netconf-charter.html>.
Author's Address
George M. Jones, Editor
The MITRE Corporation
7525 Colshire Dr., WEST
McLean, VA 22102
U.S.A.
Phone: +1 703 488 9740
EMail: gmjones@mitre.org
URI: http://www.port111.com/opsec/
Jones, Editor Expires April 24, 2004 [Page 48]
Internet-Draft Operational Security Requirements October 2003
Appendix A. Requirement Profiles
This Appendix lists different profiles. A profile is a list of list
of requirements that apply to a particular class of devices. The
minimum requirements profile applies to all devices.
A.1 Minimum Requirements Profile
The functionality listed here represents a bare minimum set of
requirements which any managed networking infrastructure device
should adhere to. This includes all core and edge devices which are
part of an IP network (such as routers, and switches). Note that
SOHO equipment (typically DSL modem/routers, cable modem/routers,
etc) and wireless networking infrastructure equipment have their own
set of requirements and are not expected to adhere to this particular
set of minimal requirements.
The minimal requirements profile addresses functionality which will
provide reasonable capabilities to manage the devices in the event of
attacks, simplify troubleshooting, keep track of events which affect
system integrity, help analyze causes of attacks, as well as provide
administrators control over IP addresses and protocols to help
mitigate the most common attacks and exploits.
A.1.1 Functional Requirements
A.1.1.1 Device Management Requirements
o Support Secure Management Channels
A.1.1.2 In-Band Management Requirements
The following requirements apply only if In-Band management is used
to satisfy Section 2.1.1 (Support Secure Management Channels)
o Use Encryption Algorithms Subject To Open Review
o Use Strong Encryption
A.1.1.3 Out-of-Band (OoB) Management Requirements
The following requirements apply only if Out-of-Band management is
used to satisfy Section 2.1.1 (Support Secure Management Channels)
o Support a Non-IP 'Console' interface
Jones, Editor Expires April 24, 2004 [Page 49]
Internet-Draft Operational Security Requirements October 2003
o Support A Simple Default Communication Profile On The 'Console'
o Support Separate Management Plane IP Interfaces
o No Forwarding Between Management Plane And Other Interfaces
o Provide Separate Resources For The Management Plane
A.1.1.4 Configuration Requirements
CLI Provides Access to All Configuration and Management Functions
CLI Uses Existing Authentication Mechanisms
CLI Supports Scripting of Configuration
CLI Supports Management Over 'Slow' Links
Support Software Installation
Support Remote Configuration Backup
Support Remote Configuration Restore
Support Human-Readable Configuration File
A.1.1.5 IP Stack Requirements
o Comply With Relevant IETF RFCs on All Protocols Implemented
o Ability to Identify All Listening Services
o Ability to Disable Any and All Services
o Listening Services Should Be Off By Default
o Ability to Control Service Bindings for Listening Services
o Ability to Control Service Source Address
o Support Automatic Anti-spoofing for Single-Homed Networks
o Directed Broadcasts Disabled by Default
Jones, Editor Expires April 24, 2004 [Page 50]
Internet-Draft Operational Security Requirements October 2003
A.1.1.6 Basic Filtering Capabilities
o Ability to Filter Traffic
o Ability to Filter Traffic TO the Device
o Ability to Filter Updates
o Ability to Specify Filter Actions
o Ability to Log Filter Actions
A.1.1.7 Packet Filtering Criteria
o Ability to Filter on Protocols
o Ability to Filter on Addresses
o Ability to Filter on Any Protocol Header Fields
o Ability to Filter Inbound and Outbound
A.1.1.8 Packet Filtering Counter Requirements
o Packet Filtering Counter Requirements
o Ability to Display Filter Counters
o Ability to Display Filter Counters per Rule
o Ability to Display Filter Counters per Filter Application
o Ability to Reset Filter Counters
o Filter Counters Must Be Accurate
A.1.1.9 Other Packet Filtering Requirements
o Filter, Counters, and Filter Log Must Have Minimal Performance
Impact
A.1.1.10 Event Logging Requirements
o Logging Facility Conforms to Open Standards
Jones, Editor Expires April 24, 2004 [Page 51]
Internet-Draft Operational Security Requirements October 2003
o Ability to Log to Remote Server
o Ability to Log Locally
o Ability to Maintain Accurate System Time
o Logs Must Be Timestamped
o Logs Contain Untranslated Addresses
A.1.1.11 Authentication, Authorization, and Accounting (AAA)
Requirements
o Authenticate All User Access
o Support Authentication of Individual Users
o Support Simultaneous Connections
o Ability to Disable All Local Accounts
o Support Centralized User Authentication Methods
o Support Local User Authentication Method
o Support Configuration of Order of Authentication Methods
o No Unencrypted Transmission of Reusable Plain-text Passwords
o Ability to Define Privilege Levels
o Ability to Assign Privilege Levels to Users
o Default Privilege Level Must Be Read Only
o Change in Privilege Levels Requires Re-Authentication
o Support Recovery Of Privileged Access
o Accounting Records
A.1.2 Documentation Requirements
o Document Listening Services
o Identify Origin of IP Stack
Jones, Editor Expires April 24, 2004 [Page 52]
Internet-Draft Operational Security Requirements October 2003
o Identify Origin of Operating System
A.1.3 Assurance Requirements
o Comply With Relevant IETF RFCs on All Protocols Implemented
o Identify Origin of IP Stack
o Identify Origin of Operating System
A.2 Layer 3 Network Core Profile
This section builds on the minimal requirements listed in A.1 and
adds more stringent security functionality specific to layer 3
devices which are part of the network core. The network core devices
need to be as free as possible from features which affect high-speed
packet forwarding.
A core device is defined as a device that makes up the network
infrastructure but does not connect directly to customers or peers.
This would include backbone core routers.
A.2.1 Functional Requirements
A.2.1.1 IP Stack Requirements
A.3 Layer 3 Network Edge Profile
This section builds on the minimal requirements listed in A.1 and
adds more stringent security functionality specific to layer 3
devices which are part of the network edge. The network edge is
typically where much of the filtering and traffic control policies
are implemented.
An edge device is defined as a device that makes up the network
infrastructure and connects directly to customers or peers. This
would include routers connected to peering points, switches
connecting customer hosts, etc.
A.3.1 Functional Requirements
A.3.1.1 IP Stack Requirements
o Support Automatic Anti-spoofing for Single-Homed Networks
Jones, Editor Expires April 24, 2004 [Page 53]
Internet-Draft Operational Security Requirements October 2003
A.3.1.2 Rate Limiting Requirements
o Support Rate Limiting
o Support Rate Limiting Based on State
A.3.1.3 Basic Filtering Capabilities
o Ability to Filter Traffic THROUGH the Device
Jones, Editor Expires April 24, 2004 [Page 54]
Internet-Draft Operational Security Requirements October 2003
Appendix B. Acknowledgments
This document grew out of an internal security requirements document
used by UUNET for testing devices that were being proposed for
connection to the backbone.
The editor gratefully acknowledges the contributions of:
o Greg Sayadian, author of a predecessor of this document.
o Eric Brandwine, a major source of ideas/critiques.
o The MITRE Corporation for supporting continued development of this
document. NOTE: The editor's affiliation with The MITRE
Corporation is provided for identification purposes only, and is
not intended to convey or imply MITRE's concurrence with, or
support for, the positions, opinions or viewpoints expressed by
the editor.
o UUNET's entire network security team (past and present): Jared
Allison, Eric Brandwine, Clarissa Cook, Dave Garn, Tae Kim, Kent
King, Neil Kirr, Mark Krause, Michael Lamoureux, Maureen Lee, Todd
MacDermid, Chris Morrow, Alan Pitts, Greg Sayadian, Bruce Snow,
Robert Stone, Anne Williams, Pete White.
o Others who have provided significant feedback at various stages of
the life of this document are: Ran Atkinson, Fred Baker, Steve
Bellovin, Michael H. Behringer, Matt Bishop, Scott Blake, Randy
Bush, Steven Christey, Owen Delong, Sean Donelan, Robert Elmore,
Barry Greene, Dan Hollis, Merike Kaeo, John Kristoff, Chris
Liljenstolpe, James W. Laferriere, Jared Mauch, Alan Paller, Rob
Pickering, Gregg Schudel, Don Smith, Rodney Thayer, David Walters,
Joel N. Weber II, Anthony Williams, Neal Ziring
o Madge B. Harrison, technical writing review.
o This listing is intended to acknowledge contributions, not to
imply that the individual or organizations approve the content of
this document.
o Apologies to those who commented on/contributed to the document
and were not listed...contact the editor to be credited in future
versions
Version: $Id: draft-jones-opsec-01.cpp,v 1.4 2003年10月13日 11:39:26
george Exp $
Jones, Editor Expires April 24, 2004 [Page 55]
Internet-Draft Operational Security Requirements October 2003
Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assignees.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
Jones, Editor Expires April 24, 2004 [Page 56]
Internet-Draft Operational Security Requirements October 2003
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Jones, Editor Expires April 24, 2004 [Page 57]