None. G. Jones, Editor
Internet-Draft The MITRE Corporation
Expires: December 8, 2003 June 9, 2003
Network Security Requirements for Devices Implementing Internet
Protocol
draft-jones-opsec-00
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 except that the right to
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This Internet-Draft will expire on December 8, 2003.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document defines a list of security requirements for devices
that implement the Internet Protocol (IP). These requirements apply
to devices that makeup the network core infrastructure (such as
routers and switches) as well other devices that implement IP (e.g.,
cable modems, personal firewalls,hosts). A framework is defined for
specifying "profiles", which are collections of devices applicable to
certain classes of devices. The goal is to provide consumers of
network equipment a clear, concise way of communicating their
security requirements to vendors of such equipment. Please send any
COMMENTS TO: "opsec-comment@ops.ietf.org". ALSO SEE "http://
www.port111.com/opsec/opsec-meta.txt".
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 5
1.1 Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3 Context . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.4 Intended Audience . . . . . . . . . . . . . . . . . . . . 5
1.5 Format . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.6 Intended Use . . . . . . . . . . . . . . . . . . . . . . . 6
1.7 Definitions . . . . . . . . . . . . . . . . . . . . . . . 7
2. Best Current Practice . . . . . . . . . . . . . . . . . . 8
2.1 Device Management Requirements . . . . . . . . . . . . . . 8
2.1.1 Support Out-of-Band Management (OoB) Interfaces . . . . . 8
2.1.2 Enforce Separation of Data and Control Channels . . . . . 8
2.1.3 Separation Not Achieved by Filtering . . . . . . . . . . . 9
2.1.4 No Forwarding Between Management and Data Planes . . . . . 9
2.1.5 Device Remains Manageable at All Times . . . . . . . . . . 9
2.1.6 Support Remote Configuration Backup . . . . . . . . . . . 10
2.1.7 Support Management Over Slow Links . . . . . . . . . . . . 11
2.2 User Interface Requirements . . . . . . . . . . . . . . . 11
2.2.1 Support Human-Readable Configuration File . . . . . . . . 11
2.2.2 Display of 'Sanitized' Configuration . . . . . . . . . . . 11
2.3 IP Stack Requirements . . . . . . . . . . . . . . . . . . 12
2.3.1 Comply With Relevant IETF RFCs on All Protocols
Implemented . . . . . . . . . . . . . . . . . . . . . . . 12
2.3.2 Provide a List of All Protocols Implemented . . . . . . . 14
2.3.3 Provide Documentation for All Protocols Implemented . . . 14
2.3.4 Ability to Identify All Listening Services . . . . . . . . 14
2.3.5 Ability to Disable Any and All Services . . . . . . . . . 15
2.3.6 Ability to Control Service Bindings for Listening
Services . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3.7 Ability to Control Service Source Address . . . . . . . . 16
2.3.8 Ability to Withstand Well-Known Attacks and Exploits . . . 16
2.3.9 Maintain Primary Function at All Times . . . . . . . . . . 17
2.3.10 Support Automatic Anti-spoofing for Single-Homed
Networks . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.3.11 Ability to Disable Processing of Packets Utilizing IP
Options . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.3.12 Ability to Disable Directed Broadcasts . . . . . . . . . . 19
2.3.13 Identify Origin of IP Stack . . . . . . . . . . . . . . . 20
2.3.14 Identify Origin of Operating System . . . . . . . . . . . 20
2.4 Rate Limiting Requirements . . . . . . . . . . . . . . . . 20
2.4.1 Support Rate Limiting . . . . . . . . . . . . . . . . . . 21
2.4.2 Support Rate Limiting Based on State . . . . . . . . . . . 21
2.5 Ability to Filter Traffic . . . . . . . . . . . . . . . . 22
2.6 Packet Filtering Criteria . . . . . . . . . . . . . . . . 22
2.6.1 Ability to Filter on Protocols . . . . . . . . . . . . . . 22
2.6.2 Ability to Filter on Addresses . . . . . . . . . . . . . . 22
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2.6.3 Ability to Filter on Any Protocol Header Fields . . . . . 23
2.6.4 Ability to Filter Inbound and Outbound . . . . . . . . . . 23
2.6.5 Ability to Filter on Layer 2 MAC Addresses . . . . . . . . 24
2.7 Packet Filtering Application Targets . . . . . . . . . . . 24
2.7.1 Ability to Filter Traffic Through the Device . . . . . . . 24
2.7.2 Ability to Filter Traffic to the Device . . . . . . . . . 24
2.7.3 Ability to Filter Updates . . . . . . . . . . . . . . . . 25
2.8 Packet Filtering Actions . . . . . . . . . . . . . . . . . 25
2.8.1 Ability to Specify Filter Actions . . . . . . . . . . . . 25
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 . . . . . . . . . . . . 26
2.9.3 Ability to Display Filter Counters per Rule . . . . . . . 27
2.9.4 Ability to Display Filter Counters per Filter
Application . . . . . . . . . . . . . . . . . . . . . . . 27
2.9.5 Ability to Reset Filter Counters . . . . . . . . . . . . . 28
2.9.6 Filter Counters Must Be Accurate . . . . . . . . . . . . . 28
2.10 Other Packet Filtering Requirements . . . . . . . . . . . 28
2.10.1 Ability to Log Filter Actions . . . . . . . . . . . . . . 29
2.10.2 Ability to Specify Filter Log Granularity . . . . . . . . 29
2.10.3 Ability to Filter Without Performance Degradation . . . . 29
2.10.4 Filter, Counters, and Filter Log Performance Must Be
Usable . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.11 Event Logging Requirements . . . . . . . . . . . . . . . . 31
2.11.1 Ability to Log All Events That Affect System Integrity . . 31
2.11.2 Logging Facility Conforms to Open Standards . . . . . . . 32
2.11.3 Catalog of Log Messages Available . . . . . . . . . . . . 32
2.11.4 Ability to Log to Remote Server . . . . . . . . . . . . . 32
2.11.5 Ability to Select Reliable Delivery . . . . . . . . . . . 33
2.11.6 Ability to Configure Security of Log Messages . . . . . . 33
2.11.7 Ability to Log Locally . . . . . . . . . . . . . . . . . . 33
2.11.8 Ability to Specify Logservers by Event Classification . . 34
2.11.9 Ability to Classify Events . . . . . . . . . . . . . . . . 34
2.11.10 Ability to Maintain Accurate System Time . . . . . . . . . 35
2.11.11 Logs Must Be Timestamped . . . . . . . . . . . . . . . . . 35
2.11.12 Logs Contain Untranslated Addresses . . . . . . . . . . . 36
2.11.13 Logs Do Not Contain DNS Names by Default . . . . . . . . . 36
2.12 Authentication, Authorization, and Accounting (AAA)
Requirements . . . . . . . . . . . . . . . . . . . . . . . 37
2.12.1 Authenticate All User Access . . . . . . . . . . . . . . . 37
2.12.2 Support Authentication of Individual Users . . . . . . . . 37
2.12.3 Support Simultaneous Connections . . . . . . . . . . . . . 37
2.12.4 Ability to Disable All Local Accounts . . . . . . . . . . 38
2.12.5 Support Centralized User Authentication . . . . . . . . . 38
2.12.6 Support Local User Authentication . . . . . . . . . . . . 39
2.12.7 Support Configuration of Order of Authentication
Methods . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.12.8 Ability to Authenticate Without Reusable Plaintext
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Passwords . . . . . . . . . . . . . . . . . . . . . . . . 39
2.12.9 Support Device-to-Device Authentication . . . . . . . . . 40
2.12.10 Ability to Define Privilege Levels . . . . . . . . . . . . 41
2.12.11 Ability to Assign Privilege Levels to Users . . . . . . . 41
2.12.12 Default Privilege Level Must Be Read Only . . . . . . . . 42
2.12.13 Change in Privilege Levels Requires Re-Authentication . . 42
2.12.14 Accounting Records . . . . . . . . . . . . . . . . . . . . 42
2.13 Layer 2 Requirements . . . . . . . . . . . . . . . . . . . 43
2.13.1 Filtering MPLS LSRs . . . . . . . . . . . . . . . . . . . 43
2.13.2 VLAN Isolation . . . . . . . . . . . . . . . . . . . . . . 44
2.13.3 Layer 2 Denial-of-Service . . . . . . . . . . . . . . . . 44
2.13.4 Layer 3 Dependencies . . . . . . . . . . . . . . . . . . . 45
2.14 Vendor Behavior . . . . . . . . . . . . . . . . . . . . . 45
2.14.1 Vendor Responsiveness . . . . . . . . . . . . . . . . . . 45
3. Non-Standard Requirements . . . . . . . . . . . . . . . . 47
3.1 Device Management Requirements . . . . . . . . . . . . . . 47
3.1.1 Support Secure Management Channels . . . . . . . . . . . . 47
3.1.2 Use Non-Proprietary Encryption . . . . . . . . . . . . . . 48
3.1.3 Use Strong Encryption . . . . . . . . . . . . . . . . . . 48
3.1.4 Key Management Must Be Scalable . . . . . . . . . . . . . 49
3.1.5 Support Scripting of Management Functions . . . . . . . . 49
3.2 User Interface Requirements . . . . . . . . . . . . . . . 50
3.2.1 Display All Configuration Settings . . . . . . . . . . . . 50
3.3 IP Stack Requirements . . . . . . . . . . . . . . . . . . 50
3.3.1 Support Denial-Of-Service (DoS) Tracking . . . . . . . . . 50
3.3.2 Traffic Monitoring . . . . . . . . . . . . . . . . . . . . 51
3.3.3 Traffic Sampling . . . . . . . . . . . . . . . . . . . . . 52
4. Advanced Requirements . . . . . . . . . . . . . . . . . . 54
4.1 IP Stack Requirements . . . . . . . . . . . . . . . . . . 54
4.1.1 Ability To Stealth Device . . . . . . . . . . . . . . . . 54
5. Security Considerations . . . . . . . . . . . . . . . . . 56
References . . . . . . . . . . . . . . . . . . . . . . . . 57
Author's Address . . . . . . . . . . . . . . . . . . . . . 59
A. Requirement Profiles . . . . . . . . . . . . . . . . . . . 60
A.1 Minimum Requirements Profile . . . . . . . . . . . . . . . 60
A.2 Layer 3 Network Core Profile . . . . . . . . . . . . . . . 61
A.3 Layer 3 Network Edge Profile . . . . . . . . . . . . . . . 61
A.4 Layer 2 Network Core Profile . . . . . . . . . . . . . . . 62
A.5 Layer 2 Edge Profile . . . . . . . . . . . . . . . . . . . 62
B. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 63
Intellectual Property and Copyright Statements . . . . . . 64
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1. Introduction
1.1 Goals
The goal of this document is to define a list of security
requirements for devices that implement Internet Protocol (IP). The
intent of the list is to provide consumers of IP devices a clear,
concise way of communicating their security requirements to equipment
vendors.
1.2 Scope
These requirements apply to devices that make up the network core
infrastructure (such as routers and switches) as well other devices
that implement IP (e.g., cable modems, personal firewalls,hosts).
While, the examples given are written with IPv4 in mind, most of the
requirements are general enough to apply to IPv6.
1.3 Context
Devices are expected to conform to protocol specifications as defined
by the Internet Engineering Task Force (IETF) Request for Comment
(RFC) series for all protocols which they implement unless otherwise
noted.
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 three sections
below.
o Section 2 lists requirements that are based on approved standards
and/or codify existing best practices. Requirements in this
category are mature.
o Section 3 lists requirements for security features or practices
that are desirable, but for which there are not yet approved
standards or widely accepted best practices. Requirements in this
category are generally the subject of active work.
Work-in-progress documents such as vendor documents, Internet
drafts or documents describing a practice may be cited as
examples.
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o Section 4 lists requirements for security features or practices
that are desirable that have not been standardized and that may
present significant challenges in terms of implementation,
support, cost, or other issues.
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,
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 are suggestions only and
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.
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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
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2. Best Current Practice
This section is intended to list security features that comprise best
practice at the time of writing. They are known to be implemented
and useful for improving security.
2.1 Device Management Requirements
2.1.1 Support Out-of-Band Management (OoB) Interfaces
Requirement. The device MUST provide an OoB interface for management
access.
Justification. This is important because it allows all management of
the device to be done via separate control channels and reduces
the risk that unauthorized individuals will observe management
traffic and/or compromise the device.
It applies in situations where a separate OoB management network
exists or other OoB access mechanisms (e.g., modems) are used to
provide secure remote management.
Examples. This requirement MAY be satisfied with a serial console
port or a separate network interface, such as an Ethernet port.
Warnings. OoB management may not be required or feasible in all
situations: for instance; if remote management is not a
requirement.
2.1.2 Enforce Separation of Data and Control Channels
Requirement. The device MUST support separation of data and control
channels. It MUST support complete physical and logical separation
of management and non-management traffic.
Justification. Separation of control and data channels enables the
application of separate and appropriate controls to each channel,
and reduces the possibility that a vulnerability in one area/
environment (data forwarding) could have an adverse impact on
another area (control/management). For example, imagine that a
"killer packet" or buffer overrun is discovered that allows
arbitrary users of a public network to crash the data forwarding
elements of a router. If data forwarding and control elements are
separated, it is likely that the control elements will continue to
function, allowing the network operator to evaluate and respond to
the problem. If they are not separated (e.g., they both use the
same interfaces and share an operating system and IP stack), then
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it is likely that the entire device will crash or become
unmanageable.
Examples. This requirement may be satisfied by supporting OoB
management interfaces per Section 2.1.1 and supporting the ability
to disable all protocols that support management functions (e.g.,
telnet, FTP, TFTP, SSH, SNMP, HTTP, etc.) on all non-management
ports.
See [I-D.ietf-forces-requirements] for related requirements.
Warnings. None.
2.1.3 Separation Not Achieved by Filtering
Requirement. The requirements to enforce separation of of data and
control channels SHALL NOT be satisfied using a filtering
mechanism alone.
Justification. Filters do not guarantee internal separation of
traffic.
Examples. None.
Warnings. None.
2.1.4 No Forwarding Between Management and Data Planes
Requirement. It MUST NOT be possible to forward data between data
plane and management plane.
Justification. This is to ensure that it is impossible to route
packets to the management interface through the publicly
accessible ports on the device.
Examples. One way of meeting this requirement would be to have
completely separate IP stacks and forwarding tables for management
and non-management interfaces and to prohibit propagation of
routing information between the two forwarding tables.
Warnings. None.
2.1.5 Device Remains Manageable at All Times
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Requirement. The device MUST remain manageable at all times, even in
the presence of attacks directed to or through the device.
Justification. This requirement is particularly important for
management ports. If a malicious user is able to effectively
disable the management port, then it may be impossible for
authorized users to access the device to respond to incidents and
maintain normal operation.
Examples. Assume that an attacker is able to flood the management
port, launch a large number of well known attacks (See Section
2.3.8) directly against the management port, or to use a group of
compromised hosts to saturate all links connected to the device.
It is precisely under these conditions that it is critical to
preserve ability to connect to the device to perform management
functions. The issuance of such management commands may be the
primary tool for mitigating the effects of the attacks. Also see
Section 2.5.
Warnings. There is a never-ending arms race between the discovery/
exploitation of new vulnerabilities and the full deployment of
code and configurations necessary to remove the vulnerabilities.
This requirement is therefore something of an ideal. It will
require constant attention on the part of both vendors and
operators to achieve the best approximation of meeting the
requirement at any given time. Also see the warning on Section
2.3.9
2.1.6 Support Remote Configuration Backup
Requirement. The device MUST provide a means to store and retrieve
the system configuration to/from 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 or FTP over a secure
channel. See Section 3.1.1 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.
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2.1.7 Support Management Over Slow Links
Requirement. The device MUST provide a management interface that
enables management over low bandwidth links (e.g., modem or serial
port)
Justification. This is important because it is often necessary to
manage remote devices for which high bandwidth access is not
available.
Examples. A consistent command line interface is one possible
implementation of this requirement. An open, well-defined,
scriptable management protocol is another.
Warnings. None.
2.2 User Interface Requirements
2.2.1 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.
2.2.2 Display of 'Sanitized' Configuration
Requirement. The device MUST support the display of a "sanitized"
configuration in which all sensitive information that appears in
the system configuration must be replaced with innocuous data.
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Justification. This is necessary to allow safe distribution and
analysis of configurations.
Examples. Some examples of "sensitive information" include:
* system passwords
* usernames and passwords
* shared secrets (RADIUS, TACACS, IKE, VPN, SNMP, NTP, routing
protocols, etc.)
* Private keys
* All IP addresses and blocks.
* System names
* Domain names
* Comments
* Banners
* User defined data (filter names, SNMP profile names, etc.)
* Contact information (snmp server, contact, location info, etc.)
One simple way of obscuring the information would be to replace it
with "***"s or similar characters in the display of the device
configuration.
Warnings. Some information may be "sensitive" in some situations, but
not in others. Passwords are clearly sensitive. Other
information in configurations that may be considered sensitive
could include: IP addresses on particular interfaces (one way of
obscuring these might be to replace the first octet with "10." in
all cases), the name of the device, comments, banners, addresses
of peers/upstream devices, addresses of logging devices, AAA
servers, NTP servers, etc.
2.3 IP Stack Requirements
2.3.1 Comply With Relevant IETF RFCs on All Protocols Implemented
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Requirement. The device MUST fully comply with IETF RFCs for all
protocols implemented.
Justification. This is important because it ensures interoperability
of products from multiple vendors.
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
[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
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Warnings. None.
2.3.2 Provide a List of All Protocols Implemented
Requirement. The vendor SHOULD provide a concise list all protocols
implemented by the device.
Justification. This facilitates thorough and appropriately targeted
testing.
Examples. None.
Warnings. None.
2.3.3 Provide Documentation for All Protocols Implemented
Requirement. The vendor SHOULD provide references to publicly
available specifications for all protocols implemented.
Justification. Security thorough obscurity is bad policy. Closed,
undocumented protocols that have not undergone through public
review may contain undiscovered (by the vendor) vulnerabilities
that can easily be exploited. Open, documented protocols
facilitate thorough and appropriately targeted testing.
Examples. None.
Warnings. It is acknowledged that there may be valid business or
other non-technical reasons for not releasing documentation for
protocols, This requirement should be evaluated on a case-by-case
basis.
2.3.4 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. The mechanism should also display the interfaces on
which each service is listening.
* Provide a documented explanation for all network services that
may be active on the system.
* Concisely document which features enable listening ports on the
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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.
2.3.5 Ability to Disable Any and All Services
Requirement. The device MUST provide a means to turn off any external
services.
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. It SHOULD be possible to enable/disable each service
independently if it is not needed.
Warnings. None.
2.3.6 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.
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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. The default configuration as displayed by Section 3.2.1
should list all interfaces and all potential services along with
the ports they listen to, the addresses they listen to, and the
interfaces they bind to. These should all be made configurable.
Warnings. None.
2.3.7 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.
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.
2.3.8 Ability to Withstand Well-Known Attacks and Exploits
Requirement. The device MUST have an IP stack and operating system
that is robust enough to withstand well-known attacks and
exploits. For the purpose of this document, well-known attacks and
exploits are defined as those that have been published by the
following:
* Computer Emergency Response Team Coordination Center [CERT/CC]
Advisories
* Common Vulnerabilities and Exposures [CVE] entries
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* Bugtraq [Bugtraq] postings
* Standard Nessus [Nessus] Plugins
* Vendor security bulletins for the device in question.
Justification. Product vulnerabilities and tools to exploit
vulnerabilities are all constantly evolving. A configuration that
is secure one day may be insecure the next due to the discovery of
a new vulnerability or the release of a new exploit script.
Devices that are vulnerable to known exploits may be easily
compromised or disabled. This can affect confidentiality,
availability, and data integrity.
Examples. Take for example the SNMP vulnerabilities described in
[CERT.2002-03]. These vulnerabilities were discovered and a
toolkit for exploiting them was publicly released. What this
requirement is saying is that known vulnerabilities such as this
should be fixed.
It is up to the customer/operator to verify to their satisfaction
that the system is "bug free" and free of known exploits. Some
possible methods of doing this include
* Taking the vendors word
* Testing for themselves
* Relying on 3rd party testing/certification
Warnings. It is acknowledged that the number of known vulnerabilities
is constantly expanding and that it is not possible to prove that
any system is completely bug and vulnerability free (with
apologies to any computer science researchers who may think
otherwise). Any test or "certification" of a device to show
compliance with this requirement will be an approximation at a
point in time. The most that can be shown is that a given list of
exploits failed.
2.3.9 Maintain Primary Function at All Times
Requirement. The device MUST maintain its primary function at all
times, even in the presence of attacks directed to or through the
device.
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Justification. One of the primary goals of security is to preserve
availability of resources (such as routers, switches or hosts) for
authorized use. That is the goal of this requirement.
Examples. Assume that several attacks (See Section 2.3.8 were
directed at the management port or that a flood attack was
directed through the device. In both these cases, the device
should continue to perform its routing/switching functions. Also
see Section 2.5.
Warnings. There is a never ending arms race between those who would
discover and exploit vulnerabilities and those who would defend
against them. New vulnerabilities are discovered continually, and
there is a window of opportunity for harm between the time of
discovery and the time that the patch or configuration changes is
applied. The vendor must be made aware of the problem, analyze it,
implement fixes, and make updated code/images available. The
operator must acquire and install the patched code and/or perform
the necessary configuration to defend against the new
vulnerability. In this context, this requirement is admittedly an
idealized goal.
2.3.10 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.
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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.
2.3.11 Ability to Disable Processing of Packets Utilizing IP Options
Requirement. The device MUST provide a means to disable processing of
all packets utilizing IP Options. This option MUST be available
on a per-interface basis. It MUST be possible to individually
configure which options are processed. Source routing SHOULD be
disabled by default.
Justification. Options can be used to alter normal traffic flows and
thus circumvent network-based access control mechanisms (such as
firewalls). They can also be used to provide information (such as
routes taken) that could be useful to an attacker mapping a
network.
Examples. None.
Warnings. RFC791 says "The Options provide for control functions
needed or useful in some situations but unnecessary for the most
common communications... [options] must be implemented by all IP
modules (host and gateways). What is optional is their
transmission in any particular datagram, not their implementation"
2.3.12 Ability to Disable Directed Broadcasts
Requirement. The device MUST provide a configuration mechanism so
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.
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These SHOULD be the default settings.
Justification. Directed broadcasts have few legitimate uses in modern
networks and are easily abused to amplify denial of service
attacks (e.g., SMURF attacks). [RFC2664] recommends the same
change in default settings as a Best Current Practice.
Examples. None.
Warnings. None.
2.3.13 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.
2.3.14 Identify Origin of Operating System
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.
2.4 Rate Limiting Requirements
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2.4.1 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
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.
2.4.2 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.
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2.5 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 2.6.
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.
Warnings. None.
2.6 Packet Filtering Criteria
2.6.1 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.
2.6.2 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.
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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.
2.6.3 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.
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.
2.6.4 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.
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Warnings. None.
2.6.5 Ability to Filter on Layer 2 MAC Addresses
Requirement. Filters in layer 2 devices MUST be able to filter based
on Media Access Control (MAC) addresses.
Justification. This provides a level of control that may be needed to
enforce policy and respond to malicious activity.
Examples. Policy may require, for example, that personal systems not
be allowed to connect to the internal desktop network. Restricting
the MAC addresses on a port is one way of enforcing this.
Warnings. None.
2.7 Packet Filtering Application Targets
2.7.1 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. Ingress filtering as described in [RFC2827] is one example
of filtering traffic intended to pass through the device.
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
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addressed to the device.
Warnings. None.
2.7.3 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 2.5 and/or with mechanisms specific to each
protocol. Also note that update filtering is required in addition
to secure channels (Section 3.1.1) 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.
2.8 Packet Filtering Actions
2.8.1 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
2.10.1 and Section 2.9
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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
?]
2.9 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
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.
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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 seperate 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.
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.
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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
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
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2.10.1 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
attempts.
Warnings. None.
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.
2.10.3 Ability to Filter Without Performance Degradation
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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).
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.
2.10.4 Filter, Counters, and Filter Log Performance Must Be Usable
Requirement. Filtering, logging, and counting functionality MUST be
implemented such that they are usable, from a performance
standpoint, in situations where they are the logical solution.
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.
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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
* 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.
2.11 Event Logging Requirements
2.11.1 Ability to Log All Events That Affect System Integrity
Requirement. The logging facility MUST be capable of logging any
event that affects system integrity.
Justification. Having the device log all events that might impact
system integrity promotes accountability and enables
audit-ability.
Examples.
The list of items that must be logged includes, but is not limited
to, the following events:
* Filter matches, described in Section 2.10.1
* Authentication failures (e.g., bad login attempts)
* Authentication successes (e.g., user logins)
* Authorization changes (e.g., User privilege level changes)
* Configuration changes (e.g., command accounting)
* Device status changes (interface up/down, etc.)
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Warnings. None.
2.11.2 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.
Warnings. While [RFC3164] and SNMP may satisfy this requirement, they
both fail to satisfy several other logging requirements.
2.11.3 Catalog of Log Messages Available
Requirement. The vendor MUST specify a catalog of all messages that a
device can emit. This MUST be included with every release of
software for the device.
Justification. A complete catalog of all possible messages permits
the customer to automate response to possible events.
Examples. None.
Warnings. None.
2.11.4 Ability to Log to Remote Server
Requirement. The device MUST be capale 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].
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Warnings. High volumes of logging may generate excessive network
traffic and/or compete for scarce memory and CPU resources on the
device.
2.11.5 Ability to Select Reliable Delivery
Requirement. It MUST be possible to select reliable, sequenced
delivery of log messages between device sending the message and
server receiving the message.
Justification. Reliable delivery is important to the extent that log
data is depended upon to make operational decisions and forensic
analysis. Without reliable delivery, log data becomes a
collection of hints.
Examples. One example of reliable syslog delivery is defined in
[RFC3195]. Syslog-ng provides another example, although the
protocol has not been standardized.
Warnings. None.
2.11.6 Ability to Configure Security of Log Messages
Requirement. It MUST be possible to configure the logging mechanism
such that there is independent control of the authenticity,
integrity, confidentiality, and replay prevention of log messages.
Justification. See section 5 of [RFC3195], and section 6 of
[RFC3164].
Examples. [RFC3195] defines one way of meeting these requirements.
Warnings. None.
2.11.7 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.
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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.
2.11.8 Ability to Specify Logservers by Event Classification
Requirement. The device MUST allow the remote log server to be
specified by the event classification. For example,
security-related messages would go to one log server, while
operational messages would go to another.
Justification. This is important because it allows (in concert with
requirement Section 2.11.9 ) messages of certain types to be sent
to different servers for processing. This is important in
environments with large numbers of devices, large numbers of log
messages, and/or where responsibilities for certain classes of
messages are divided.
Examples. This requirement MAY be satisfied by providing
configuration commands that allow the user to assign syslog
facilities to each message or class of messages. For example, it
should be possible to specify that all security-related events be
assigned syslog facility local4 and that messages classified as
local4 should be sent to syslog server 10.9.8.7.
Warnings. None.
2.11.9 Ability to Classify Events
Requirement. The device SHOULD provide a mechanism for assigning
classifications to all messages. At a minimum, it MUST provide
the ability to assign a chosen classification to all security
related messages, and different classification(s) to all other
messages.
Justification. This is important because it allows (in concert with
requirement Section 2.11.8 ) messages of certain types to be sent
to different servers for processing. This is important in
environments with large numbers of devices, large numbers of log
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messages, and/or where responsibilities for certain classes of
messages are divided.
Examples. This requirement MAY be satisfied by providing a mechanism
to assign specific syslog facility codes to specific messages or
groups of messages. For example, all security events could be
assigned to one facility code, all network routing issues to
another, and all physical (power, line card) to another.
Warnings. None.
2.11.10 Ability to Maintain Accurate System Time
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). See Section 3.1.1 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).
2.11.11 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.
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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.
2.11.12 Logs Contain Untranslated Addresses
Requirement. Log messages MUST contain relevant IP addresses.
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.
2.11.13 Logs Do Not Contain DNS Names by Default
Requirement. By default, log messages MUST NOT contain DNS names
resolved at the time the message was generated. The device MAY
provide a facility to incorporate translated DNS names in addition
to the IP address.
Justification. This is important because IP to DNS mappings change
over time and mappings done at one point in time may not be valid
later. Also, the use of the resources (memory, processor, time,
bandwidth) required to do the translation could result in *no*
data being sent/logged, and, in the extreme case could lead to
degraded performance and/or resource exhaustion.
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Examples. None.
Warnings. DNS name translation can impose significant performance
delays.
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.
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.
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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.
Warnings. None.
2.12.5 Support Centralized User Authentication
Requirement. The device MUST support 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. This requirement MAY be satisfied by implementing Terminal
Access Controller Access Control System Plus (TACACS+), Remote
Authentication Dial-In User Service (RADIUS), or Kerberos 5. See
Section 3.1.1 for requirements related to secure communication
channels for management protocols and data.
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Warnings. None.
2.12.6 Support Local User Authentication
Requirement. The device MAY support local authentication.
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
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.
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 Ability to Authenticate Without Reusable Plaintext Passwords
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Requirement. The device MUST perform authentication without the
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 3.1.1.
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
passwords with standard telnet without being carried over a secure
channel (see Section 3.1.1) 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 Support Device-to-Device Authentication
Requirement. The device MUST support device-to-device authentication
for all non-interactive management protocols. Also see Section
2.12.8 and Section 3.1.1
Justification. This is required to allow automated management
functions to operate with a reasonable level assurance that
updates and sharing of management information is occurring only
with authorized devices.
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Examples. Examples of protocols that implement device to device
authentication are: SNMP (community strings), NTP and BGP (shared
keys).
Warnings. None.
2.12.10 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
2.12.11
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.
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.
2.12.11 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
are authenticated the device. Privilege level determines which
functions a user is allowed to execute. Also see See Section
2.12.10.
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. 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.
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Warnings. None.
2.12.12 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.
2.12.13 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.
2.12.14 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
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* All logouts
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 3.1.1 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 Requirements
2.13.1 Filtering MPLS LSRs
Requirement. The device MUST provide a method to filter packets based
on layer 3 and 4 criteria on Label Switch Routers (LSRs)
regardless of whether they are encapsulated using Multi Protocol
Label Switching (MPLS). The MPLS encapsulated packets MUST NOT be
allowed to bypass IP filters. Logging facilities that MUST provide
previous-hop information when information so the previous hop for
a logged packet can be determined. Packets tagged with MPLS labels
MUST be treated as IP packets when crossing an interface on which
a filter is applied. Encapsulation/decapsulation MAY take place
before or after the filter as long as it does not cause the
filters to be ignored. When logging the input interface
information for hits on outgoing filter list rules, any MPLS label
that was present when the packet was received MUST be logged with
the input interface. This functionality is equivalent to the
requirement that all layer 2 source information must be logged
when the input interface is logged. Also, the addition of any
filtering and logging MUST be implemented with no significant
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performance degradation to the normal system operations.
Justification. This is important because it may be necessary to
filter traffic encapsulated in a LSP. This applies primarily to
backbone and large core networks.
Examples. None.
Warnings. None.
2.13.2 VLAN Isolation
Requirement. The device MUST NOT allow VLAN Hopping. This applies to
the insertion of falsified VLAN IDs or 802.1Q (or equivalent) tags
into frames in an attempt to hop from one VLAN to another while
traversing the switch. Many VLAN implementations allow hopping if
the native VLAN (usually VLAN 1) is set up as the trunk port. If
this is the case then the default configuration on the switch MUST
NOT allow the trunk port to be set as the native VLAN. Also the
switch MUST NOT broadcast ARP requests across VLANs.
Justification. This requirement is intended to ensure that layer 2
traffic remains isolated to designated VLANs. It applies in
situations where data on different VLAN segments have different
sensitivity classification.
Examples. None.
Warnings. None.
2.13.3 Layer 2 Denial-of-Service
Requirement. It MUST NOT be possible for users connected to a switch
port to perform an action which results in denial of service to
other users connected to the switch. Examples of denial of service
would include:
* Causing the switch to crash
* Causing long delays (e.g., by forcing spanning tree
recalculations)
* Redirecting/stealing traffic
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Justification. This requirement is needed to ensure the
confidentiality and availability of data transmitted via the
switch.
Examples. None.
Warnings. None.
2.13.4 Layer 3 Dependencies
Requirement. If a device provides layer 2 services that are dependent
on layer 3 or greater services, then the portions that operate at
layer 3 MUST conform to the layer 3 security requirements listed
in this document where appropriate. For example, signaling
protocols required for layer 2 switching may exchange information
with other devices using layer 3 communications. The device must
provide a secure layer 3 facility.
Justification. All layer 3 devices have similar security needs and
should be subject to similar requirements.
Examples. None.
Warnings. None.
2.14 Vendor Behavior
2.14.1 Vendor Responsiveness
Requirement. The vendor MUST be responsive to current and future
security requirements as specified by the customer. When new
security exploits are discovered, either by the customer or the
public, the vendor MUST provide patches or workarounds in a timely
fashion to mitigate the threat from any existing vulnerability in
the system. The vendor MUST ensure that it remains actively aware
of security threats.
Justification. This is important because new vulnerabilities are
regularly discovered. Slow vendor response to vulnerabilities
increase the level of risk/window of opportunity for exploit. This
requirement applies to ALL devices.
Examples. This is a non-technical requirement. The implementation
involves process, customer support, engineering, etc.
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Warnings. This "requirement" has a large element of subjectivity.
When evaluating vendor responsiveness, objective data (such as
mean time to releasing patches for new exploits) should be
evaluated.
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3. Non-Standard Requirements
This section is intended to list security features that may not be
implemented at the time of this writing, would be useful for
improving security, and are not thought to present significant
challenges in terms of technology required, support costs,
performance impact, etc.
3.1 Device Management Requirements
3.1.1 Support Secure Management Channels
Requirement. The device MUST provide a secure end-to-end channel 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 by using protocols that support secure channels
directly or by layering insecure protocols over secure transport
protocols.
Justification. Secure channels ensure confidentiality and integrity
of management traffic.
Examples. Secure channels are most commonly implemented using
encryption...one can imagine other secure channels, such as
shielded cable run in tamper-evident conduit monitored by armed
guards... but in most cases "secure channel" will mean encryption.
See [ANSI.T1.276-200x] for a discussion of appropriate algorithms.
The following table shows examples of the security requirements
for different classes of protocols. The rows list different
classes of protocols. The columns show the required security
attributes. The attributes are: Confidentiality (Conf.),
Integrity (Integ.), User-to-Device Authentication (Auth. U2D), and
Device-to-Device Authentication (Auth D2D).:
+---------------+-------+-------+-------+-------+
| Type | Conf. | Integ.| Auth. | Auth. |
| Protocol(s) | | | U2D | D2D |
+---------------+-------+-------+-------+-------+
| Management | X | X | X | |
| telnet, HTTP| | | | |
| FTP, | | | | |
+---------------+-------+-------+-------+-------+
| Management | X | X | | X |
| TFTP,SNMP | | | | |
+---------------+-------+-------+-------+-------+
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| Logging | X | X | | X |
| Syslog | | | | |
| | | | | |
+---------------+-------+-------+-------+-------+
| Time | | | | |
| NTP | | X | | X |
| | | | | |
+---------------+-------+-------+-------+-------+
| AAA | | | | |
| TACACS, | | | | |
| RADIUS, | X | X | X | X |
| DIAMETER, | | | | |
| Kerberos, | | | | |
+---------------+-------+-------+-------+-------+
| Routing | | | | |
| BGP,OSPF, | | X | | X |
| RIP | | | | |
+---------------+-------+-------+-------+-------+
Warnings. None.
3.1.2 Use Non-Proprietary Encryption
Requirement. If encryption is used to satisfy the Section 3.1.1
requirements, then the encryption algorithms used MUST be
non-proprietary. See [ANSI.T1.276-200x]
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. None.
Warnings. None.
3.1.3 Use Strong Encryption
Requirement. If encryption is used to satisfy the Section 3.1.1
requirements, then the key lengths and algorithms MUST be "strong"
by current definitions.
Justification. Short keys and weak algorithms threaten the
confidentiality and integrity of communications.
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Examples. [ANSI.T1.276-200x] provides a list of acceptable key
lengths for various types of encryption algorithms at the time of
this writing.
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.
3.1.4 Key Management Must Be Scalable
Requirement. The number of keys and passwords that must be managed to
support other requirements in this document MUST scale well.
Specifically, The number of keys and passwords managed MUST
increase, at most, linearly as the number of devices and users.
Justification. In large networks, or in networks with large number of
users, the key/password space could quickly grow to unmanageable
size, inhibiting proper management and making audits difficult if
not impossible.
Examples. [Ed. insert verbiage about PKIs, etc. Contributions to
this space solicited.] See Section 3.1.1.
Warnings. [Ed. insert verbiage about PKIs, etc. Contributions to
this space solicited]
3.1.5 Support Scripting of Management Functions
Requirement. The device MUST provide a management interface that:
* Supports external scripting
* Has a simple, regular syntax
* Allows complete access to all management functions
* Works consistently on both in-band and out-of-band interfaces
The interface MUST NOT be a text-based menu, windowing system, or
GUI. The implementation should support scripts running on external
systems using Perl, Expect, or some other common scripting
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languages. This requirement explicitly does not anticipate
support for scripting languages on the device itself.
Justification. Scripting support is important for configuration
fetching, auditing, attack tracking, automated administration,
etc.
Examples. A consistent command line interface is one possible
implementation of this requirement. An open, well-defined,
scriptable management protocol is another. An example of this
would be the work currently being done in the IETF on xmlconf. See
[I-D.enns-xmlconf-spec].
Warnings. None.
3.2 User Interface Requirements
3.2.1 Display All Configuration Settings
Requirement. The device MUST provide a mechanism to display a
complete listing of all possible configuration settings and their
current values. This MUST include values for any "hidden"
commands. It MUST be possible to display all values, even those
that are disabled, "off," or set to default values.
Justification. It is not possible to perform thorough audits without
a complete listing of all possible configuration settings and
their current values.
Examples. None.
Warnings. It has been stated that it may be unreasonable to expect
vendors to expose all settings, as this would lead to confusion
due to customers changing settings that did not apply to their
situation, and could drive up support costs.
3.3 IP Stack Requirements
3.3.1 Support Denial-Of-Service (DoS) Tracking
Requirement. The device MUST include native "spoofed" packet
tracking. This feature:
* MUST be able to capture data to a tracking table that shows how
many packets match a configurable layer 3/4 header pattern or
list of patterns from each previous hop router.
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* MUST display the interface on which a matching packet arrived.
* MUST display the layer-2 header information. arrived.
* MUST implement "unknown source" as an optional part of the
header pattern where "unknown" is the set of all addresses that
are unreachable by the router (i.e., not in the forwarding
table).
* MUST be able to display the tracking table showing the pattern
that is being tracked and how many matches were received from
each previous hop.
This feature MUST be implemented with minimal impact to system
performance.
Justification. This applies in situations where DoS attacks, possibly
utilizing spoofed source addresses, must be tracked across one or
more routers. Without the capability to track DoS packets, it is
possible that an attacker could adversely impact the availability
of resources (hosts, routers, network links, etc.) leaving network
administrators little to no capability to track and stop the
attack. Layer 2 header information is particularly useful for
identifying spoofed sources coming in over an Ethernet interface
at a peering point and you want to track the source back to a
particular ISP so you can ask them to trace the source.
Examples.
These features must allow the customer to quickly and easily ask
the router which packets matching a given profile came into the
router, from where, and how many from each source.
Note that this requirement MAY be satisfied by implementing the
requirements listed in Section 2.5
Warnings. None.
3.3.2 Traffic Monitoring
Requirement. The device MUST provide a means to monitor selected
traffic through the system. It MUST provide the ability to select
specific traffic patterns for monitoring based on arbitrary IP
header patterns and layer 4 (TCP and UDP) header patterns. This
includes: source and destination IP address, IP header flags,
layer 4 source and destination ports (TCP, UDP), ICMP type and
code fields, and other IP protocol types (e.g., 50 - ESP, 47 -
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GRE, etc.). It MUST provide the ability to monitor the full
contents of the packets. This feature MUST be implemented with
minimal impact on system performance. In addition, the device MUST
provide a means to remotely capture the data being monitored.
Justification. This requirement applies in contexts where traffic
headers and content must be monitored. This enables
characterization of malicious (and non-malicious) traffic, which
may be essential to enable effective response and maintain normal
operations.
Examples.
The addition of any traffic monitoring facility must be
implemented with minimal impact on system performance. See Section
3.1.1 for requirements related to secure communication channels
for management protocols and data.
Remote capture of header data could be implemented by sending it
via syslog or SNMP. For the full packet capture, the device may
send this information over the network for small data streams, or
provide a "port mirroring" capability for large data streams where
the data would be duplicated out a second configurable port.
Warnings. Monitoring data can add significant network traffic,
processor, and memory use.
3.3.3 Traffic Sampling
NOTE: there is a proposed IETF working group active in this area. See
the mailing list archives at https://ops.ietf.org/lists/psamp/. It is
possible this section may just reference the product of that working
group.
Requirement. The device MUST provide a means to sample traffic
through the system and summarize data from the layer 3 and 4
headers.
It MUST be possible to dump the cache at specified intervals to a
collection host. It MUST be possible to specify device behavior
when the cache is full. Options SHOULD include: dumping the cache
to the specified collection host(s), clearing the cache,
overwriting the cache, and disabling further sampling. The cache
SHOULD be implemented as a circular buffer such that older entries
are overwritten first. The device SHOULD provide options to
manually dump or clear the cache.
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The device SHOULD provide a means of summarizing sampled data.
The following IP layer header information SHOULD be summarized
appropriately: type of service (or DS field), total length,
protocol, source, and destination. The following TCP/UDP header
information SHOULD be summarized appropriately: source port,
destination port, UDP packet length, TCP header length, and TCP
flag bits.
The device MUST provide the ability to select the traffic-sampling
rate. For instance, there MUST be a way to sample every nth
packet, where n is a number determined by an authorized user and
entered into the system configuration file. This feature must be
implemented with minimal impact on system performance.
Justification. This requirement enables accurate characterization of
data transiting the device. This supports identification of and
response to malicious traffic.
Examples. This requirement MAY be satisfied by allowing the user to
specify that 1 in every N packets should be sampled. See Section
3.1.1 for requirements related to secure communication channels
for management protocols and data.
Warnings. Traffic sampling can add significant network traffic,
processor, and memory use.
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4. Advanced Requirements
This section is intended to list security features that may not be
implemented at the time of this writing, would be useful for
improving security, but which may present significant challenges in
terms of technology required, support costs, performance impact, etc.
4.1 IP Stack Requirements
4.1.1 Ability To Stealth Device
Requirement. The device MUST provide a mechanism to allow it to
become a "black box" as seen from public interfaces. Specifically
this means:
* The device SHOULD provide no information about itself (e.g.,
system type, HW configuration, operating system type/revision,
etc.) beyond the edge of the network (except for what's
required to route traffic).
* Edge interfaces SHOULD be visible beyond the network.
* Internal interfaces SHOULD NOT be visible beyond the network
(but would be visible within the network).
* It MUST be possible to not only disable all listening ports,
but also to prevent them from initiating any traffic (such as
ICMP error messages) in response to user activity.
While the default configuration of the device SHOULD be fully RFC
compliant (including the sending of ICMP messages), it MUST be
possible to alter the default configuration such that the device
is "stealthed" (i.e., does not send ICMP messages or otherwise
respond directly to packets directed to it on non-management
interfaces).
Justification. This applies primarily in the context of core network
infrastructure. A stealthed infrastructure which can not be
addressed is less susceptible to direct attack. Stealthing the
core network infrastructure would eliminate the possibility of
large classes of attacks and thus increase reliability and
availability.
Examples. Some specific capabilities important to stealthing include:
* Ability to filter/deny/ignore pings (ICMP echo requests)
* Ability to filter on individual protocol header bits
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* Ability to control the generation of ICMP messages, including
port unreachable and timeouts
It MUST be possible to configure each of these settings
individually.
Warnings. Although some STEALTHING MECHANISMS MAY BE IN VIOLATION OF
SOME RFCs, they are desirable/necessary in certain circumstances
for security and operational reasons.
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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.
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References
[ANSI.T1.276-200x]
American National Standards Institute (ANSI),
"T1.276-200x: Draft proposed American National Standard
for Telecommunications Operations, Administration,
Maintenance, and Provisioning Security Requirements for
the Public Telecommunications Network: A Baseline of
Security Requirements for the Management Plane", April
2003.
[Bugtraq] SecurityFocus/Symantec, "Bugtraq mailing list", 2003,
<http://www.securityfocus.com/archive/1>.
[CERT.2002-03]
CERT/CC, "Multiple Vulnerabilities in Many Implementations
of the Simple Network Management Protocol (SNMP)", 2002,
<http://www.cert.org/advisories/CA-2002-03.html>.
[CERT/CC] CERT/CC, "CERT/CC Advisories", 2003, <http://www.cert.org/
advisories/>.
[CVE] The MITRE Corporation, "MITRE Common Vulnerabilities and
Exposures", 2003, <http://www.cve.mitre.org>.
[I-D.enns-xmlconf-spec]
Enns, R., "XMLCONF Configuration Protocol",
draft-enns-xmlconf-spec-00 (work in progress), February
2003.
[I-D.ietf-forces-requirements]
Khosravi, H. and T. Anderson, "Requirements for Separation
of IP Control and Forwarding",
draft-ietf-forces-requirements-09 (work in progress), May
2003.
[Nessus] Deraison, R., "Nessus Security Scanner", 2003, <http://
www.nessus.org>.
[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.
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[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.
[RFC2664] Plzak, R., Wells, A. and E. Krol, "FYI on Questions and
Answers - Answers to Commonly Asked "New Internet User"
Questions", RFC 2664, 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
2001.
[RFC3195] New, D. and M. Rose, "Reliable Delivery for syslog", RFC
3195, November 2001.
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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/
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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.
[Ed. there have been major changes to the individual requirements
since these profiles were created. They will be updated in -01].
A.1 Minimum Requirements Profile
o Section 2.3.1
o Section 2.1.1
o Section 3.1.1
o Section 2.1.6
o Section 2.12.1
o Section 2.12.2
o Section 2.12.3
o Section 2.12.4
o Section 2.12.5
o Section 2.12.6
o Section 2.12.7
o Section 2.12.8
o Section 2.12.10
o Section 2.12.11
o Section 2.12.12
o Section 2.12.13
o Section 2.12.14
o Section 2.3.8
o Section 2.3.4
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o Section 2.3.5
o Section 2.3.6
o Section 2.11.1
o Section 2.2.1
o Section 3.1.5
o Section 2.1.7
o Section 2.14.1
A.2 Layer 3 Network Core Profile
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. This section lists layer
requirements specific to core devices.
o Section 3.3.3
o Section 3.3.2
o Section 3.3.1
o Section 4.1.1
A.3 Layer 3 Network Edge Profile
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. This section lists layer
requirements specific to edge devices. In general, edge device
requirements are a superset of those for core devices.
o Section 2.4.1
o Section 2.4.2
o Section 2.5
o Section 2.6.3
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o Section 2.6.2
o Section 2.11.1
o Section 2.11.7
o Section 2.11.4
o Section 2.9.1
o Section 2.7.1
o Section 2.7.2
o Section 2.10.3
o Section 3.3.3
o Section 3.3.2
o Section 3.3.1
A.4 Layer 2 Network Core Profile
This section lists layer two requirements specific to core devices.
o Section 2.13.2
o Section 2.13.3
o Section 2.13.4
A.5 Layer 2 Edge Profile
This section lists layer two requirements specific to edge devices.
o Section 2.13.1
o Section 2.6.5
o Section 2.13.2
o Section 2.13.3
o Section 2.13.4
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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, Sean Donelan, Robert Elmore, Barry Greene, Dan Hollis,
Merike Kaeo, John Kristoff, Chris Liljenstolpe, James W.
Laferriere, Alan Paller, Rob Pickering, Gregg Schudel, Rodney
Thayer, David Walters, 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-00.cpp,v 1.9 2003/06/09 10:59:03
george Exp $
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Jones, Editor Expires December 8, 2003 [Page 65]
