Request for Comments: 3871 The MITRE Corporation
Category: Informational September 2004
Operational Security Requirements for Large
Internet Service Provider (ISP) IP Network Infrastructure
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
This document defines a list of operational security requirements for
the infrastructure of large Internet Service Provider (ISP) IP
networks (routers and switches). A framework is defined for
specifying "profiles", which are collections of requirements
applicable to certain network topology contexts (all, core-only,
edge-only...). The goal is to provide network operators a clear,
concise way of communicating their security requirements to vendors.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Goals. . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2. Motivation . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Scope. . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.4. Definition of a Secure Network . . . . . . . . . . . . . 6
1.5. Intended Audience. . . . . . . . . . . . . . . . . . . . 6
1.6. Format . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.7. Intended Use . . . . . . . . . . . . . . . . . . . . . . 7
1.8. Definitions. . . . . . . . . . . . . . . . . . . . . . . 7
2. Functional Requirements . . . . . . . . . . . . . . . . . . . 11
2.1. Device Management Requirements . . . . . . . . . . . . . 11
2.1.1. Support Secure Channels For Management. . . . . 11
2.2. In-Band Management Requirements. . . . . . . . . . . . . 12
2.2.1. Use Cryptographic Algorithms Subject To
Open Review . . . . . . . . . . . . . . . . . . 12
2.2.2. Use Strong Cryptography . . . . . . . . . . . . 13
2.2.3. Use Protocols Subject To Open Review For
Management. . . . . . . . . . . . . . . . . . . 14
2.2.4. Allow Selection of Cryptographic Parameters . . 15
2.2.5. Management Functions Should Have Increased
Priority. . . . . . . . . . . . . . . . . . . . 16
2.3. Out-of-Band (OoB) Management Requirements . . . . . . . 16
2.3.1. Support a ’Console’ Interface . . . . . . . . . 17
2.3.2. ’Console’ Communication Profile Must Support
Reset . . . . . . . . . . . . . . . . . . . . . 19
2.3.3. ’Console’ Requires Minimal Functionality of
Attached Devices. . . . . . . . . . . . . . . . 19
2.3.4. ’Console’ Supports Fall-back Authentication . . 20
2.3.5. Support Separate Management Plane IP
Interfaces. . . . . . . . . . . . . . . . . . . 21
2.3.6. No Forwarding Between Management Plane And Other
Interfaces. . . . . . . . . . . . . . . . . . . 21
2.4. Configuration and Management Interface Requirements. . . 22
2.4.1. ’CLI’ Provides Access to All Configuration and
Management Functions. . . . . . . . . . . . . . 22
2.4.2. ’CLI’ Supports Scripting of Configuration . . . 23
2.4.3. ’CLI’ Supports Management Over ’Slow’ Links . . 24
2.4.4. ’CLI’ Supports Idle Session Timeout . . . . . . 25
2.4.5. Support Software Installation . . . . . . . . . 25
2.4.6. Support Remote Configuration Backup . . . . . . 27
2.4.7. Support Remote Configuration Restore. . . . . . 27
2.4.8. Support Text Configuration Files. . . . . . . . 28
2.5. IP Stack Requirements. . . . . . . . . . . . . . . . . . 29
2.5.1. Ability to Identify All Listening Services. . . 29
2.5.2. Ability to Disable Any and All Services . . . . 30
2.5.3. Ability to Control Service Bindings for
Listening Services. . . . . . . . . . . . . . . 30
2.5.4. Ability to Control Service Source Addresses . . 31
2.5.5. Support Automatic Anti-spoofing for
Single-Homed Networks . . . . . . . . . . . . . 32
2.5.6. Support Automatic Discarding Of Bogons and
Martians. . . . . . . . . . . . . . . . . . . . 33
2.5.7. Support Counters For Dropped Packets. . . . . . 34
2.6. Rate Limiting Requirements . . . . . . . . . . . . . . . 35
2.6.1. Support Rate Limiting . . . . . . . . . . . . . 35
2.6.2. Support Directional Application Of Rate
Limiting Per Interface. . . . . . . . . . . . . 36
2.6.3. Support Rate Limiting Based on State. . . . . . 36
2.7. Basic Filtering Capabilities . . . . . . . . . . . . . . 37
2.7.1. Ability to Filter Traffic . . . . . . . . . . . 37
2.7.2. Ability to Filter Traffic TO the Device . . . . 37
2.7.3. Ability to Filter Traffic THROUGH the Device. . 38
2.7.4. Ability to Filter Without Significant
Performance Degradation . . . . . . . . . . . . 38
2.7.5. Support Route Filtering . . . . . . . . . . . . 39
2.7.6. Ability to Specify Filter Actions . . . . . . . 40
2.7.7. Ability to Log Filter Actions . . . . . . . . . 40
2.8. Packet Filtering Criteria. . . . . . . . . . . . . . . . 41
2.8.1. Ability to Filter on Protocols. . . . . . . . . 41
2.8.2. Ability to Filter on Addresses. . . . . . . . . 42
2.8.3. Ability to Filter on Protocol Header Fields . . 42
2.8.4. Ability to Filter Inbound and Outbound. . . . . 43
2.9. Packet Filtering Counter Requirements. . . . . . . . . . 43
2.9.1. Ability to Accurately Count Filter Hits . . . . 43
2.9.2. Ability to Display Filter Counters. . . . . . . 44
2.9.3. Ability to Display Filter Counters per Rule . . 45
2.9.4. Ability to Display Filter Counters per Filter
Application . . . . . . . . . . . . . . . . . . 45
2.9.5. Ability to Reset Filter Counters. . . . . . . . 46
2.9.6. Filter Counters Must Be Accurate. . . . . . . . 47
2.10. Other Packet Filtering Requirements . . . . . . . . . . 47
2.10.1. Ability to Specify Filter Log Granularity . . . 47
2.11. Event Logging Requirements . . . . . . . . . . . . . . . 48
2.11.1. Logging Facility Uses Protocols Subject To
Open Review . . . . . . . . . . . . . . . . . . 48
2.11.2. Logs Sent To Remote Servers . . . . . . . . . . 49
2.11.3. Ability to Select Reliable Delivery . . . . . . 49
2.11.4. Ability to Log Locally. . . . . . . . . . . . . 50
2.11.5. Ability to Maintain Accurate System Time. . . . 50
2.11.6. Display Timezone And UTC Offset . . . . . . . . 51
2.11.7. Default Timezone Should Be UTC. . . . . . . . . 52
2.11.8. Logs Must Be Timestamped. . . . . . . . . . . . 52
2.11.9. Logs Contain Untranslated IP Addresses. . . . . 53
2.11.10. Logs Contain Records Of Security Events . . . . 54
2.11.11. Logs Do Not Contain Passwords . . . . . . . . . 55
2.12. Authentication, Authorization, and Accounting (AAA)
Requirements . . . . . . . . . . . . . . . . . . . . . . 55
2.12.1. Authenticate All User Access. . . . . . . . . . 55
2.12.2. Support Authentication of Individual Users. . . 56
2.12.3. Support Simultaneous Connections. . . . . . . . 56
2.12.4. Ability to Disable All Local Accounts . . . . . 57
2.12.5. Support Centralized User Authentication
Methods . . . . . . . . . . . . . . . . . . . . 57
2.12.6. Support Local User Authentication Method. . . . 58
2.12.7. Support Configuration of Order of
Authentication Methods . . . . . . . . . . . . 59
2.12.8. Ability To Authenticate Without Plaintext
Passwords . . . . . . . . . . . . . . . . . . . 59
2.12.9. No Default Passwords. . . . . . . . . . . . . . 60
2.12.10. Passwords Must Be Explicitly Configured Prior
To Use. . . . . . . . . . . . . . . . . . . . . 60
2.12.11. Ability to Define Privilege Levels. . . . . . . 61
2.12.12. Ability to Assign Privilege Levels to Users . . 62
2.12.13. Default Privilege Level Must Be ’None’. . . . . 62
2.12.14. Change in Privilege Levels Requires
Re-Authentication . . . . . . . . . . . . . . . 63
2.12.15. Support Recovery Of Privileged Access . . . . . 64
2.13. Layer 2 Devices Must Meet Higher Layer Requirements. . . 65
2.14. Security Features Must Not Cause Operational Problems. . 65
2.15. Security Features Should Have Minimal Performance
Impact . . . . . . . . . . . . . . . . . . . . . . . . . 66
3. Documentation Requirements . . . . . . . . . . . . . . . . . . 67
3.1. Identify Services That May Be Listening. . . . . . . . . 67
3.2. Document Service Defaults. . . . . . . . . . . . . . . . 67
3.3. Document Service Activation Process. . . . . . . . . . . 68
3.4. Document Command Line Interface. . . . . . . . . . . . . 68
3.5. ’Console’ Default Communication Profile Documented . . . 69
4. Assurance Requirements . . . . . . . . . . . . . . . . . . . . 69
4.1. Identify Origin of IP Stack. . . . . . . . . . . . . . . 70
4.2. Identify Origin of Operating System. . . . . . . . . . . 70
5. Security Considerations . . . . . . . . . . . . . . . . . . . 71
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 71
6.1. Normative References . . . . . . . . . . . . . . . . . . 71
6.2. Informative References . . . . . . . . . . . . . . . . . 74
Appendices
A. Requirement Profiles . . . . . . . . . . . . . . . . . . . . . 75
A.1. Minimum Requirements Profile . . . . . . . . . . . . . . 75
A.2. Layer 3 Network Edge Profile . . . . . . . . . . . . . . 78
B. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 79
Author’s Address . . . . . . . . . . . . . . . . . . . . . . . . . 80
Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 81
1. Introduction
1.1. Goals
This document defines a list of operational security requirements for
the infrastructure of large IP networks (routers and switches). The
goal is to provide network operators a clear, concise way of
communicating their security requirements to equipment vendors.
1.2. Motivation
Network operators need tools to ensure that they are able to manage
their networks securely and to insure that they maintain the ability
to provide service to their customers. Some of the threats are
outlined in section 3.2 of [RFC2196]. This document enumerates
features which are required to implement many of the policies and
procedures suggested by [RFC2196] in the context of the
infrastructure of large IP-based networks. Also see [RFC3013].
1.3. Scope
The scope of these requirements is intended to cover the managed
infrastructure of large ISP IP networks (e.g., routers and switches).
Certain groups (or "profiles", see below) apply only in specific
situations (e.g., edge-only).
The following are explicitly out of scope:
o general purpose hosts that do not transit traffic including
infrastructure hosts such as name/time/log/AAA servers, etc.,
o unmanaged devices,
o customer managed devices (e.g., firewalls, Intrusion Detection
System, dedicated VPN devices, etc.),
o SOHO (Small Office, Home Office) devices (e.g., personal
firewalls, Wireless Access Points, Cable Modems, etc.),
o confidentiality of customer data,
o integrity of customer data,
o physical security.
This means that while the requirements in the minimum profile (and
others) may apply, additional requirements have not be added to
account for their unique needs.
While the examples given are written with IPv4 in mind, most of the
requirements are general enough to apply to IPv6.
1.4. 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 it is supposed to go, and only where it is
supposed to go (availability, confidentiality).
o The network elements remain manageable (availability).
o Only authorized users can manage network elements (authorization).
o There is a record of all security related events (accountability).
o The network operator has the necessary tools to detect and respond
to illegitimate traffic.
1.5. Intended Audience
There are two intended audiences: the network operator who selects,
purchases, and operates IP network equipment, and the vendors who
create them.
1.6. Format
The individual requirements are listed in the three sections 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 Requirement (what)
o 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. See
[RFC3631]. It is expected that the choice of implementations to meet
the requirements will change over time. The warnings list
operational concerns, 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, Appendix A defines several
requirement "profiles" for different types of devices. Profiles are
concise lists of requirements that apply to certain classes of
devices. The profiles in this document should be reviewed to
determine if they are appropriate to the local environment.
1.7. Intended Use
It is anticipated that the requirements in this document will be used
for the following purposes:
o as a checklist when evaluating networked products,
o to create profiles of different subsets of the requirements which
describe the needs of different devices, organizations, and
operating environments,
o to assist operators in clearly communicating their security
requirements,
o as high level guidance for the creation of detailed test plans.
1.8. Definitions
RFC 2119 Keywords
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].
The use of the RFC 2119 keywords is an attempt, by the editor, to
assign the correct requirement levels ("MUST", "SHOULD",
"MAY"...). It must be noted that different organizations,
operational environments, policies and legal environments will
generate different requirement levels. Operators and vendors
should carefully consider the individual requirements listed here
in their own context. One size does not fit all.
Bogon.
A "Bogon" (plural: "bogons") is a packet with an IP source address
in an address block not yet allocated by IANA or the Regional
Internet Registries (ARIN, RIPE, APNIC...) as well as all
addresses reserved for private or special use by RFCs. See
[RFC3330] and [RFC1918].
CLI.
Several requirements refer to a Command Line Interface (CLI).
While this refers at present to a classic text oriented command
interface, it is not intended to preclude other mechanisms which
may meet all the requirements that reference "CLI".
Console.
Several requirements refer to a "Console". The model for this is
the classic RS232 serial port which has, for the past 30 or more
years, provided a simple, stable, reliable, well-understood and
nearly ubiquitous management interface to network devices. Again,
these requirements are intended primarily to codify the benefits
provided by that venerable interface, not to preclude other
mechanisms that meet all the same requirements.
Filter.
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.
In-Band management.
"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.
High Resolution Time.
"High resolution time" is defined in this document as "time having
a resolution greater than one second" (e.g., milliseconds).
IP.
Unless otherwise indicated, "IP" refers to IPv4.
Management.
This document uses a broad definition of the term "management".
In this document, "management" refers to any authorized
interaction with the device intended to change its operational
state or configuration. Data/Forwarding plane functions (e.g.,
the transit of customer traffic) are not considered management.
Control plane functions such as routing, signaling and link
management protocols and management plane functions such as remote
access, configuration and authentication are considered to be
management.
Martian.
Per [RFC1208] "Martian: Humorous term applied to packets that turn
up unexpectedly on the wrong network because of bogus routing
entries. Also used as a name for a packet which has an altogether
bogus (non-registered or ill-formed) Internet address." For the
purposes of this document Martians are defined as "packets having
a source address that, by application of the current forwarding
tables, would not have its return traffic routed back to the
sender." "Spoofed packets" are a common source of martians.
Note that in some cases, the traffic may be asymmetric, and a
simple forwarding table check might produce false positives. See
[RFC3704]
Out-of-Band (OoB) management.
"Out-of-Band management" is defined as any management done over
channels and interfaces that are separate from those used for
user/customer data. Examples would include a serial console
interface or a network interface connected to a dedicated