None. G. Jones, Editor
Internet-Draft The MITRE Corporation
Expires: April 14, 2004 October 15, 2003
Operational Security Requirements for IP Network Infrastructure:
Advanced Requirements
draft-jones-opsec-info-00
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document defines a list of operational security requirements for
the infrastructure of large IP networks (such as routers and
switches). The goals of this document are to serve as a collection
of ideas for security features that would improve operational
security and to assist consumers of network equipment in
communicating their security requirements to vendors. The
requirements in this document are NOT considered to be best current
practice (BCP). Comments to: "opsec-comment@ops.ietf.org".
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Definition of a Secure Network . . . . . . . . . . . . . . 4
1.4 Intended Audience . . . . . . . . . . . . . . . . . . . . 5
1.5 Format . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.6 Intended Use . . . . . . . . . . . . . . . . . . . . . . . 5
1.7 Definitions . . . . . . . . . . . . . . . . . . . . . . . 6
2. Functional Requirements . . . . . . . . . . . . . . . . . 7
2.1 Device Management Requirements . . . . . . . . . . . . . . 7
2.1.1 Restrict Management to Local Interfaces . . . . . . . . . 7
2.2 In-Band Management Requirements . . . . . . . . . . . . . 7
2.2.1 Key Management Must Be Scalable . . . . . . . . . . . . . 8
2.3 Out-of-Band (OoB) Management Requirements . . . . . . . . 8
2.3.1 Enforce Separation of Data and Management Planes . . . . . 8
2.4 User Interface Requirements . . . . . . . . . . . . . . . 9
2.4.1 Display All Configuration Settings . . . . . . . . . . . . 9
2.5 IP Stack Requirements . . . . . . . . . . . . . . . . . . 10
2.5.1 Ability to Disable Processing of Packets Utilizing IP
Options . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.5.2 Support Denial-Of-Service (DoS) Tracking . . . . . . . . . 10
2.5.3 Traffic Monitoring . . . . . . . . . . . . . . . . . . . . 11
2.5.4 Traffic Sampling . . . . . . . . . . . . . . . . . . . . . 12
2.5.5 Ability To Remove In-Band Visibility . . . . . . . . . . . 13
2.6 Basic Filtering Capabilities . . . . . . . . . . . . . . . 14
2.6.1 Ability to Filter Without Performance Degradation . . . . 14
2.7 Packet Filtering Criteria . . . . . . . . . . . . . . . . 14
2.7.1 Ability to Filter on Layer 2 MAC Addresses . . . . . . . . 14
2.8 Event Logging Requirements . . . . . . . . . . . . . . . . 15
2.8.1 Ability to Log All Security Related Events . . . . . . . . 15
2.8.2 Ability to Select Reliable Delivery . . . . . . . . . . . 15
2.8.3 Ability to Classify Events . . . . . . . . . . . . . . . . 16
2.8.4 Logs Do Not Contain DNS Names by Default . . . . . . . . . 16
2.9 Authentication, Authorization, and Accounting (AAA)
Requirements . . . . . . . . . . . . . . . . . . . . . . . 17
2.9.1 Enforce Selection of Strong Local Static Authentication
Tokens (Passwords) . . . . . . . . . . . . . . . . . . . . 17
2.9.2 Support Device-to-Device Authentication . . . . . . . . . 17
2.10 Layer 2 Requirements . . . . . . . . . . . . . . . . . . . 18
2.10.1 Filtering MPLS LSRs . . . . . . . . . . . . . . . . . . . 18
2.10.2 VLAN Isolation . . . . . . . . . . . . . . . . . . . . . . 19
2.10.3 Layer 2 Denial-of-Service . . . . . . . . . . . . . . . . 19
3. Documentation Requirements . . . . . . . . . . . . . . . . 20
3.1 Provide a List of All Protocols Implemented . . . . . . . 20
3.2 Provide Documentation for All Protocols Implemented . . . 20
3.3 Catalog of Log Messages Available . . . . . . . . . . . . 20
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4. Assurance Requirements . . . . . . . . . . . . . . . . . . 22
4.1 Ability to Withstand Well-Known Attacks and Exploits . . . 22
4.2 Vendor Responsiveness . . . . . . . . . . . . . . . . . . 23
5. Security Considerations . . . . . . . . . . . . . . . . . 25
References . . . . . . . . . . . . . . . . . . . . . . . . 26
Author's Address . . . . . . . . . . . . . . . . . . . . . 26
A. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 27
Intellectual Property and Copyright Statements . . . . . . 28
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1. Introduction
1.1 Goals
The goals of this document are to serve as a collection of ideas for
security features that would improve operational security and to
assist consumers of network equipment in communicating their security
requirements to vendors.
1.2 Scope
The primary scope of these requirements is intended to cover the
infrastructure of large IP networks (e.g. routers and switches).
General purpose hosts (including infrastructure hosts such as name/
time/log/AA servers, etc.), unmanaged, or customer managed devices
(e.g. firewalls, Intrusion Detection System, dedicated VPN devices,
etc.) are explicitly out of scope.
Confidentiality and integrity of customer data are outside the scope.
While, the examples given are written with IPv4 in mind, most of the
requirements are general enough to apply to IPv6.
1.3 Definition of a Secure Network
For the purposes of this document, a secure network is one in which:
o the network keeps passing legitimate customer traffic
(availability)
o traffic goes where it's supposed to go (availability)
o the network elements remain manageable (availability)
o only authorized users can manage network elements (authorization)
o there is record of all security related events (accountability)
o the network operator has the necessary tools to detect and respond
to illegitimate traffic
The following assumptions are made:
o Devices are physically secure.
o The management infrastructure (AAA/DNS/log server, SNMP management
stations, etc.) is secure.
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1.4 Intended Audience
There are two intended audiences: the end user (consumer) who
selects, purchases, and operates IP network equipment, and the
vendors who create them.
1.5 Format
The individual requirements are listed in one of the three sections
listed below.
o Section 2 lists functional requirements.
o Section 3 lists documentation requirements.
o Section 4 lists assurance requirements.
Within these areas, requirements are grouped in major functional
areas (e.g., logging, authentication, filtering, etc.)
Each requirement has the following subsections:
o The Requirement (What)
o The Justification (Why)
o Examples (How)
o Warnings (if applicable)
The requirement describes a policy to be supported by the device. The
justification tells why and in what context the requirement is
important. The examples section is intended to give examples of
implementations that may meet the requirement. Examples cite
technology and standards current at the time of this writing. It is
expected that the choice of implementations to meet the requirements
will change over time. The warnings list operational concerns,
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.
1.6 Intended Use
It is anticipated that this document will be used in the following
manners:
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Documenting Useful, non-BCP Features This document is a collection
of security features that would be useful in improving operational
security. The features listed herein are not considered to best
current practice (BCP) at this time. It is anticipated that the
features listed here may, over time, become widely implemented and
thus be candidates for migration to a BCP document.
Security Capability Checklist The requirements in this document may
be used as a checklist when evaluating networked products.
Communicating Requirements This document may be referenced, 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. Functional Requirements
The requirements in this section are intended to list testable,
functional requirements that are needed to operate devices securely.
2.1 Device Management Requirements
2.1.1 Restrict Management to Local Interfaces
Requirement. The device MUST have the ability to restrict management
traffic to sources within one hop of the device in cases where
management done over IP.
Justification. Restricting management traffic to devices attached
locally reduces the risk of unauthorized configuration of the
device from across the Internet.
This requirement applies primarily to SOHO equipment, where
out-of-band management may not be feasible, and additional
security for management traffic is most effectively applied by
restricting it to local only.
Examples. This requirement MAY be satisfied by reducing the TTL on
return TCP management traffic to 1, or by filtering all traffic to
the management service not sourced from local subnets. See
[I-D.gill-gtsh]
Warnings. None.
2.2 In-Band Management Requirements
This section lists security requirements for devices that are managed
In-band. "In-band management" is defined as any management done over
the same channels and interfaces used for user/customer data.
In-band management has the advantage of lower cost (no extra
interfaces or lines), but has significant security disadvantages:
o saturation of customer lines or interfaces can make the device
unmanageable
o since public interfaces/channels are used, it is possible for
attackers to directly address and reach the device and to attempt
management functions
o in-band management traffic on public interfaces may be intercepted
o Since the same networking code and interfaces are shared for
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management and customer data, it is not possible to isolate
management functions from failures in other areas (for example, a
"magic packet" or buffer overrun that causes the data forwarding
portions of a router to crash will also likely make it impossible
to manage...this would not necessarily be the case if the
management and data forwarding elements were completely separated)
2.2.1 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 a large number
of users, the key/password space could quickly grow to
unmanageable size.
Examples. The use of AAA protocols such as RADIUS or the use of
Kerberos greatly increases the manageability of keys and passwords
however, someone still needs to configure the databases and
periodically ensure that the databases have not become
compromised. The use of a Public Key Infrastructure (PKI), which
utilizes digital certificates to automate the secure distribution
of passwords and keys, should be a consideration for networks with
a large set of keys/passwords to manage.
Warnings. None.
2.3 Out-of-Band (OoB) Management Requirements
See Section 2.2 for a discussion of the advantages and disadvantages
of In-band vs. Out-of-Band management.
2.3.1 Enforce Separation of Data and Management Planes
Requirement. The device MUST support separation of data and
management plane. It MUST support complete physical and logical
separation of management and non-management traffic.
Justification. Separation of management and data plane 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
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arbitrary users of a public network to crash the data forwarding
elements of a router. If data forwarding and management elements
are separated, it is likely that the management 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 it is likely that the entire device will crash or
become unmanageable.
Examples. One way to satisfy this requirement would be to do all of
the following
* Implement management and forwarding planes using separate
Operating Systems and IP stacks.
* Do not allow forwarding between management and data planes.
* Disable (or do not implement) all management functions (e.g.,
telnet, FTP, TFTP, SSH, SNMP, HTTP, etc.) on the data plane.
Warnings. None.
2.4 User Interface Requirements
2.4.1 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. Sometimes default settings change between releases, for
example an older release of software may enable directed
broadcasts by default while the newer one disables it. If the
device only displays non-default settings, then the customer/
auditor must keep a list of software versions and default settings
in order to insure that device configuration complies with local
policy (e.g. "directed broadcasts must be disabled"). The task of
auditing for policy compliance is made much simpler if there is a
way to display *all* settings, default or otherwise.
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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.
2.5 IP Stack Requirements
2.5.1 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"
2.5.2 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.
* MUST display the interface on which a matching packet arrived.
* MUST display the layer-2 header information.
* 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).
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* 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.
Warnings. None.
2.5.3 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 -
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.
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Examples.
The addition of any traffic monitoring facility must be
implemented with minimal impact on system performance.
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.
2.5.4 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.
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.
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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.
Warnings. Traffic sampling can add significant network traffic,
processor, and memory use.
2.5.5 Ability To Remove In-Band Visibility
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 not accept any packets beyond those required
to support routing information transfer.
* The device SHOULD NOT generate any packets beyond those
required to support routing information transfer. This includes
ICMP error messages.
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 to devices comprising the core network
infrastructure. This enforces out of band only access, and ensures
that risk to the core infrastructure from end users is minimized.
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
* Ability to control the generation of ICMP messages, including
port unreachable and timeouts
It MUST be possible to configure each of these settings
individually.
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Warnings. Although some STEALTHING MECHANISMS MAY BE IN VIOLATION OF
SOME RFCs, they are desirable/necessary in certain circumstances
for security and operational reasons.
2.6 Basic Filtering Capabilities
2.6.1 Ability to Filter Without Performance Degradation
Requirement. The device MUST provide a means to filter packets
without performance degradation. The device MUST be able to filter
on ALL interfaces (up to the maximum number possible)
simultaneously and with multiple filters per interface (e.g.,
inbound and outbound).
Justification. This is important because it enables the
implementation of filtering wherever and whenever needed. To the
extent that filtering causes degradation, it may not be possible
to apply filters that implement the appropriate policies.
Examples. Another way of stating the requirement is that filter
performance should not be the limiting factor in device
throughput. If a device is capable of forwarding, say, 30Mb/sec
without filtering, then it should be able to forward the same
amount with filtering in place. This requirement most likely
implies a hardware-based solution (ASIC).
Warnings. Without hardware based filtering, it may be possible for
the implementation of filters to degrade the performance of the
device or to cause it to cease functioning.
2.7 Packet Filtering Criteria
2.7.1 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.
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Warnings. None.
2.8 Event Logging Requirements
2.8.1 Ability to Log All Security Related Events
Requirement. The logging facility MUST be capable of logging any
event that affects system security.
Justification. Having the device log all events that might impact
system security 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."
* 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.)
Warnings. None.
2.8.2 Ability to Select Reliable Delivery
Requirement. It MUST be possible to select reliable, sequenced
delivery of log messages. .
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.
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Warnings. None.
2.8.3 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 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 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.
2.8.4 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.
Examples. None.
Warnings. DNS name translation can impose significant performance
delays.
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2.9 Authentication, Authorization, and Accounting (AAA) Requirements
2.9.1 Enforce Selection of Strong Local Static Authentication Tokens
(Passwords)
Requirement. Strength checks for static passwords fall into three
types:
1. computational checks against the password itself (length,
character set, upper/lower case)
2. comparison checks against static data sets (dictionary tests)
3. comparison checks against dynamic data sets (history checks,
username tests)
The device MUST support at least computational checks with the
following minimum requirements: The password MUST be at least [6]
characters long and MUST contain at least [3] of the following
elements
* At least [1] Lower case alphabetic character
* At least [1] Upper case alphabetic character
* At least [1] Numeric character
* At least [1] Special character
The device MAY enforce the selection of "strong" local passwords
through comparison checks against dynamic and/or static data sets.
Justification. Trivial passwords are easily guessed, increasing the
likelihood of unauthorized access.
Examples. An initial configuration dialog may require the user to set
a password to control initial access. If the user enters a
password that is not strong (e.g. "123") then the configuration
dialog should inform the user that the chosen password is weak and
provide another opportunity to select a strong password.
Warnings.
2.9.2 Support Device-to-Device Authentication
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Requirement. The device MUST support device-to-device authentication
for all non-interactive management protocols.
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.
Examples. Examples of protocols that implement device to device
authentication are: SNMP (community strings), NTP and BGP (shared
keys).
Warnings. None.
2.10 Layer 2 Requirements
2.10.1 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 MUST provide
sufficient information so that 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 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.
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2.10.2 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.
2.10.3 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
Justification. This requirement is needed to ensure the
confidentiality and availability of data transmitted via the
switch.
Examples. None.
Warnings. None.
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3. Documentation Requirements
The requirements in this section are intended to list information
that will assist operators in evaluating and securely operating a
device.
3.1 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. The documentation should contain a concise list in the
system/release documentation describing the protocols implemented
(link,network,transport,management, routing, etc.)
Warnings. None.
3.2 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.
3.3 Catalog of Log Messages Available
Requirement. The vendor SHOULD specify a catalog of all messages that
a device can emit. This SHOULD be included with every release of
software for the device. The contents of variable portions of
each message (IP address, hostname, timestamp, etc.) SHOULD be
documented.
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Justification. A complete catalog of all possible messages permits
the customer to automate response to possible events.
Examples. If the device sends syslog messages, then the documentation
should contain a list of all possible syslog messages.
Warnings. None.
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4. Assurance Requirements
The requirements in this section are intended to
o identify behaviors and information that will increase confidence
that the device will meet the security functional requirements.
o Provide information that will assist evaluation
4.1 Ability to Withstand Well-Known Attacks and Exploits
Requirement. The vendor MUST provide software updates or
configuration advice "in a timely fashion" to mitigate the effect
of "well know vulnerabilities" in the device itself and "well
known exploits" directed to the device. These updates or
configuration changes MUST NOT result in a reduced feature set -
except in cases where removing a feature entirely is the ONLY way
to stop the exploit. Updates SHOULD NOT introduce new features.
Vendors MUST NOT require customers to pay a fee or purchase
support (or other) contracts in order to obtain exploit fixes.
These requirements only apply to devices that are supported that
the time the exploit or vulnerability becomes "well known".
For the purpose of this document, well-known vulnerabilities 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
* Standard Nessus [Nessus] Plugins
* Vendor security bulletins for the device in question.
* The [PROTOS] test suite
While "in a timely fashion" is open to interpretation, one
measurable, customer-centric metric is "before the vulnerability
is exploited in my device causing loss of confidentiality,
integrity or availability".
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.
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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. 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.
4.2 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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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
[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.gill-gtsh]
Gill, V., Heasley, J. and D. Meyer, "The Generalized TTL
Security Mechanism (GTSM)", draft-gill-gtsh-04 (work in
progress), October 2003.
[Nessus] Deraison, R., "Nessus Security Scanner", 2003, <http://
www.nessus.org>.
[PROTOS] University of Oulu, "PROTOS Test Suites", 2003, <http://
www.ee.oulu.fi/research/ouspg/protos/>.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September
1981.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3195] New, D. and M. Rose, "Reliable Delivery for syslog", RFC
3195, November 2001.
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. Acknowledgments
This document grew out of an internal security requirements document
used by UUNET for testing devices that were being proposed for
connection to the backbone.
The editor gratefully acknowledges the contributions of:
o Greg Sayadian, author of a predecessor of this document.
o Eric Brandwine, a major source of ideas/critiques.
o The MITRE Corporation for supporting continued development of this
document. NOTE: The editor's affiliation with The MITRE
Corporation is provided for identification purposes only, and is
not intended to convey or imply MITRE's concurrence with, or
support for, the positions, opinions or viewpoints expressed by
the editor.
o UUNET's entire network security team (past and present): Jared
Allison, Eric Brandwine, Clarissa Cook, Dave Garn, Tae Kim, Kent
King, Neil Kirr, Mark Krause, Michael Lamoureux, Maureen Lee, Todd
MacDermid, Chris Morrow, Alan Pitts, Greg Sayadian, Bruce Snow,
Robert Stone, Anne Williams, Pete White.
o Others who have provided significant feedback at various stages of
the life of this document are: Ran Atkinson, Fred Baker, Steve
Bellovin, Michael H. Behringer, Matt Bishop, Scott Blake, Randy
Bush, Steven Christey, 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-01.cpp,v 1.2 2003/08/13 17:45:25
george Exp $
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