OPSEC P. Cain
Internet-Draft The Cooper-Cain Group, Inc.
Intended status: Best Current G. Jones
Practice Port111 Labs.
Expires: February 14, 2008 August 13, 2007
Logging Capabilities for IP Network Infrastructure
draft-ietf-opsec-logging-caps-04
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Abstract
This document lists logging capabilities originally identified in
Operational Security Requirements for Large Internet Service Provider
(ISP) IP Network Infrastructure [RFC3871] and needed to support
current operational practices, including those described in
Operational Security Current Practices In Internet Service Provider
Environments [RFC4778]. Logging is defined as the delivery of
messages about the device, the data passing through the device, or
the device's interaction with another device and has been
traditionally provided via the syslog or SNMP protocols.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Security Overview . . . . . . . . . . . . . . . . . . . . 4
1.2. Capabilities vs. Requirements . . . . . . . . . . . . . . 5
1.3. Format . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Functional Capabilities of Log Generating Systems . . . . . . 7
2.1. Logging Facility Uses Protocols Subject To Open Review . . 7
2.2. Logs Sent To Remote Servers . . . . . . . . . . . . . . . 8
2.3. Ability to Select Reliable Delivery . . . . . . . . . . . 9
2.4. Ability to Remotely Log with Privacy . . . . . . . . . . . 10
2.5. Ability to Log Locally . . . . . . . . . . . . . . . . . . 11
2.6. Ability to Log Different Severities to Different
Destinations . . . . . . . . . . . . . . . . . . . . . . . 12
2.7. Ability to Log to Multiple Destinations . . . . . . . . . 12
2.8. Ability to Maintain Accurate System Time . . . . . . . . . 13
2.9. Display Timezone and UTC Offset . . . . . . . . . . . . . 14
2.10. Default Timezone Should Be UTC . . . . . . . . . . . . . . 15
2.11. Log Entries Must Be Timestamped . . . . . . . . . . . . . 16
2.12. Log on Exception or Identified Event . . . . . . . . . . . 17
2.13. Logs Contain Untranslated IP Addresses . . . . . . . . . . 17
2.14. Logs Contain Records Of Critical Security Events . . . . . 18
2.15. Logs Contain Records of General Security Events . . . . . 20
2.16. Logs Do Not Contain Senstitvie Data . . . . . . . . . . . 20
2.17. Devices Should Log Every Message . . . . . . . . . . . . . 22
2.18. Log Drop Policy Should be Configurable . . . . . . . . . . 23
2.19. Local Log Storage Notification . . . . . . . . . . . . . . 24
2.20. Syslog-specific Capabilties . . . . . . . . . . . . . . . 25
2.20.1. Configurable Facility Values . . . . . . . . . . . . 25
2.20.2. Configurable Destination UDP Port . . . . . . . . . . 26
2.21. SNMP-specific capabilities . . . . . . . . . . . . . . . . 27
2.21.1. Read-only Operations Supported . . . . . . . . . . . 27
2.21.2. Restrict Sources of SNMP Queries . . . . . . . . . . 27
2.21.3. Only Return Specific Data to Requestor . . . . . . . 28
3. Security Considerations . . . . . . . . . . . . . . . . . . . 30
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
5. Informative References . . . . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 34
Intellectual Property and Copyright Statements . . . . . . . . . . 35
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1. Introduction
This document defines a set of capabilities for network equipment
that generates event logs or performs event logging in the
environments defined by Operational Security Current Practices In
Internet Service Provider Environments [RFC4778]. Its goal is to
identify capabilities required of the network equipment to generate
and forward messages from the network equipment to an event logging
system.
Although most people equate logging with using the syslog protocol
[RFC3164], other protocols such as SNMP [RFC3411] are quite capable
of generating a log entry for transmission to a remote log entry
collector.
RFC4778 defines the goals, motivation, scope, definitions, intended
audience, threat model, and potential attacks for each of the
practices currently in use by network operators. Those current
practices have been identified and refined to generate the
capabilities listed in this document.
1.1. Security Overview
The logging capabilities defined in this document are derived from
observations and experiences in real world networks where unexpected
activities in a network infrastructure caused concern to the network
operator. Examples of such activities are:
An adversary or unauthorized user login into an infrastructure
device. The risk is that the configuration or other operating
parameter could be modified.
A device becomes overwhelmed, throttles, or crashes. Without
logging or some other mechanism to notify the operator of the
condition, the operator will not know that an action is required
to return the device to optimal operating condition.
Network problems cannot be properly diagnosed without sufficient
information, which if not captured, will not be available for
diagnose activities.
The main threat in a logging infrastructure is that a bad event may
happen and the operator of the infrastructure may not be made aware
of that event and therefore cannot correct or respond to it. This
document is concerned solely with the ability of the network device
to generate appropriate messages. For guidance on transport and
secure delivery see The BSD Syslog Protocol [RFC3164]. For a logging
infrastructure introduction and guidance on building a secure
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infrastructure see NIST Publication 800-62, Guide to Security Log
Management. [SP800-92]
One threat to the logging infrastructure is a self-inflicted denial
of service attack due to an overwhelming amount of log messages
generated on the local machine. This could be caused by the local
system using all its available effort to generate log messages or
congestion through the network between the log generator and the log
collector, such that the remote system is inaccessible to management
operations. Although not specifically a capability, care should be
taken when configuring the logging infrastructure to account for this
threat.
1.2. Capabilities vs. Requirements
Capabilities may or may not be requirements. That is a local
determination that must be made by each operator with reference to
the policies that they must support. This document, together with
RFC4778, will assist network operators in identifying their security
capability requirements and communicating them clearly to vendors.
Capabilities are defined without reference to specific technologies.
This is done to leave room for deployment of new technologies that
implement the capability. Each capability cites the practices it
supports. Current implementations that support the capability are
cited.
1.3. Format
Each capability has the following subsections:
o Capability (what)
o Discussion
o Supported Practices (why)
o Current Implementations (how)
o Considerations (caveats, resource issues, protocol issues, etc.)
The Capability section describes a feature to be supported by the
device. The Supported Practice section cites practices described in
RFC4778 that are supported by this capability. The Current
Implementation section is intended to give examples of
implementations of the capability, citing technology and standards
current at the time of writing. It is expected that the choice of
features to implement the capabilities will change over time. The
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Considerations section lists operational and resource constraints,
limitations of current implementations, trade offs, etc.
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2. Functional Capabilities of Log Generating Systems
The capabilities in this section are intended to list testable,
functional capabilities that are needed to operate devices securely
and meet the obligations of Section 1.1 Security Overview.
2.1. Logging Facility Uses Protocols Subject To Open Review
Capability
The device is capable of providing a logging facility that is
based on protocols subject to open review.
Discussion
The use of logging based on protocols subject to open review
permits the operator to perform archiving and analysis of logs
without relying on vendor-supplied software and servers.
Supported Practices
* Use IETF-defined protocols such as syslog, syslog with reliable
delivery, syslog-ng, or SNMP.
Current Implementations
This capability can be satisfied by the use of one or more of
syslog [RFC3164], syslog with reliable delivery [RFC3195], TACACS+
[RFC1492], RADIUS [RFC2865], or SNMP [RFC3415].
The current best solution seems to be the following:
* Implement syslog as in .
* Consider implementing syslog with reliable delivery [RFC3195].
* Using SNMP with applicable security controls.
Considerations
None.
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2.2. Logs Sent To Remote Servers
Capability
The device is capable of supporting transmission of records of
security-related events to one or more remote collection devices.
There should be configuration settings on the device that allow
selection of destination servers.
Discussion
None.
Supported Practices
* Use multiple collection devices to enhance reliability.
* Use different collection devices to segregate different event
sensitivity levels. See Section 2.6.
Current Implementations
This capability may be satisfied by the use of one or more of:
syslog [I-D.ietf-syslog-protocol], syslog with reliable delivery
[RFC3195], TACACS+ [RFC1492], or RADIUS [RFC2865].
Considerations
This capability is important because it supports individual
accountability. It is important to store the security-related
events on a separate server to preserve them in case of failure or
compromise of the managed device.
This capability also supports analysis. It's easier to run a perl
script and insert things into a database on a logging server
dedicated to the task than a resource strapped router that may not
even have the necessary tools.
Note that there may be privacy or legal considerations when
logging/monitoring user activity.
High volumes of logging may generate excessive network traffic
and/or compete for scarce memory and CPU resources on the device.
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2.3. Ability to Select Reliable Delivery
Capability
The device is able to select reliable delivery of log messages.
Discussion
Reliable delivery is important to the extent that log data is
depended upon to make operational decisions and perform forensic
analysis. Without reliable delivery, log data becomes a
collection of hints instead of a true record of events.
Supported Practices
* Use syslog-ng.
* Use syslog with TLS [I-D.ietf-syslog-transport-tls]
* Tunnel the logging stream over a TCP-based connection.
* Use an out-of-band network to connect critical logging devices
to the collection device.
Current Implementations
One example of reliable syslog delivery is defined in
I-D.ietf-syslog-transport-tls. Syslog-ng provides another example
implementation, although the protocol has not been standardized.
Considerations
Reliable delivery should be used if the path from the log event
generator to the collection device transits administrative domains
or uses unreliable channels, as it is important that the entire
stream of log events is captured.
CAUTION: The use of reliable delivery is heavily debated within
the logging and security communities as errors encountered when
reliably logging can cause the log generator to repeatedly attempt
to deliver the log message in turn causing a denial of service or
deadlock condition. It may be desirable to use a rate-limiting
features in syslog senders or for the logger of a message to have
the option to either not log more messages or cease its own
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operation. This document does not specify which options to use.
2.4. Ability to Remotely Log with Privacy
Capability
The device is capable of delivering log data stream to the
collection device in a confidential manner.
Discussion
While syslog *could* provide this capability, it has many security
issues and by itself does not address issues from the threat
model. See the security considerations section of RFC3164 for a
list of issues. Syslog with reliable delivery provides solutions
to most/all of these issues, however at the time of this writing
there are few implementations. Other possible solutions might be
to tunnel syslog over a secure transport, but this often raises
difficult key management and scalability issues.
Supported Practices
* Log data tunnelled within IPSec or SSH.
* Use syslog-ng.
* Use security services supplied by SNMP [RFC3414]
Current Implementations
There is no common implementation of this capability.
Considerations
Delivering log data across untrusted streams or including
sensitive data in a event data may require additional
countermeasures to protect the data. This concern should not be
addressed lightly.
ISPs are fully aware that there is no security with syslog but
IPSec is considered too operationally expensive and cumbersome to
deploy. Implementations of syslog such as Syslog-ng and stunnel
could be used for better authentication and integrity protected
solutions. Physical security and access controls are important in
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the prevention of unauthorized access and modification of logs.
2.5. Ability to Log Locally
Capability
The device is capable of logging data locally on the device itself
into non-volatile storage.
Discussion
Logging of failed authentication attempts to local non-volatile
storage is critical as it provides a record of events if the
device gets isolated from its authentication interfaces or an
attack overwhelms the console interface. Local logging is also
important for viewing information when connected to the device and
it provides some backup of log data in case remote logging fails.
Local logging also provides a way to quickly view logs relevant to
one device without having to sort through a possibly large set of
logs from other devices at the collection device.
Supported Practices
* To conserve space, only failed device logins and network
connectivity issues are logged locally.
Current Implementations
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).
Considerations
Storage on the device may be limited. High volumes of log
messages may quickly fill the 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
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logging stops.
2.6. Ability to Log Different Severities to Different Destinations
Capability
The device is capable of specifying different severity levels of
log message to be delivered to different collection destinations.
Discussion
A network of multiple devices may generate a significant amount of
log data. The ability to send critical log messages, for example
a root login, to a specific destination device will enhance the
ability of the network operator to notice the critical event.
Supported Practices
* Email critical event notices to a continuously monitored
mailbox.
* Send critical event notices to a separate log collector that
scrolls received messages upon a large display in the NOC.
Current Implementations
There are no common implementations of this capability.
Considerations
The use of multiple collectors will incur maintenance and
reliability issues. In some cases, multiple filters watching a
single collection point may be more efficient than using multiple
collectors.
2.7. Ability to Log to Multiple Destinations
Capability
The device is capable of allowing log message to be delivered to
multiple collection destinations.
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Discussion
All ISPs have multiple syslog servers - some ISPs choose to use
separate syslog servers for varying infrastructure devices (i.e.,
one syslog server for backbone routers, one syslog server for
customer edge routers, etc.). This duplication provides a backup
mechanism to see what is going on in the network in the event that
a collection device 'forgets' to capture syslog messages if its
CPU is busy.
Supported Practices
* Use multiple log servers to enhance reliability.
Current Implementations
Most ISPs use multiple, sometimes geographically diverse, log
collectors.
Considerations
None.
2.8. Ability to Maintain Accurate System Time
Capability
The device is capable of maintaining accurate, "high resolution"
system time.
Discussion
Accurate time is important to the generation of reliable log data.
Accurate time is also important to the correct operation of some
authentication mechanisms.
The ability to correlate network events from different devices is
directly related to the accuracy of the log timestamps. If a time
line cannot be constructed, the event logs and forensic data are
useless.
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Supported Practices
* The time is derived from NTP which is generally configured as a
flat hierarchy at stratum-1 and stratum-2 servers to have less
configuration and fewer maintenance issues.
* Each router is configured with one stratum-1 peer both locally
and remotely.
Current Implementations
This capability may be satisfied by supporting the Network Time
Protocol (NTP) [RFC1305], Simple Network Time Protocol (SNTP)
[RFC4330], or via direct connection to an accurate time source.
Considerations
System clock chips are inaccurate to varying degrees. System time
should not be relied upon unless it is regularly checked and
synchronized with a known, accurate external time source (such as
an NTP stratum-1 server). Also note that if network time
synchronization is used, an attacker may be able to manipulate the
clock unless cryptographic authentication is used.
2.9. Display Timezone and UTC Offset
Capability
The device is capable of displaying and logging system time in a
timezone or offset from Universal Time Coordinated (UTC).
Discussion
None.
Supported Practices
* The log timestamps include a timezone indicator like "-05:00".
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Current Implementations
Many devices support this capability.
Considerations
Knowing the timezone or UTC offset makes correlation of data and
coordination with data in other timezones possible. Bob is in
Newfoundland, Canada which is UTC -3:30. Alice is somewhere in
Indiana, USA. Some parts of Indiana switch to daylight savings
time while others do not. A user on Bob's network attacks a user
on Alice's network. Both are using logs with local timezones and
no indication of UTC offset. Correlating these logs will be
difficult and error prone. Including timezone, or better, UTC
offset, eliminates these difficulties.
Notice that a physical location may have different offsets from
UTC during a year as summer time, daylight savings time, or other
local customs are applied.
2.10. Default Timezone Should Be UTC
Capability
The device is capable of using UTC for its default timezone for
display and logging. The device may be capable of supporting a
mechanism to allow the operator to specify the display and logging
of times in a timezone other than UTC.
Discussion
Knowing the timezone or UTC offset makes correlation and
coordination in other timezones possible.
Supported Practices
* The timezone offset can be entered as part of configuration of
a device.
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Current Implementations
Bob in Newfoundland (UTC -3:30) and Alice in Indiana (UTC -5 or
UTC -6 depending on the time of year and exact county in Indiana)
are working an incident together using their logs. Both left the
default settings, which was UTC, so there was no translation of
time necessary to correlate the logs.
Considerations
None.
2.11. Log Entries Must Be Timestamped
Capability
By default, the device should be capable of generating timestamps
on all log messages, accurate to within a second or less, and
including a timezone. The device should be capable of disabling
the generation of timestamps.
Discussion
Accurate timestamps are necessary for correlating events,
particularly across multiple devices or with other organizations.
This applies when it is necessary to analyze logs.
Supported Practices
* Each entry into the log file contains a time value.
Current Implementations
This capability may be satisfied by writing timestamps into syslog
messages.
Considerations
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.
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2.12. Log on Exception or Identified Event
Capability
The device is capable of generating log entries on exceptions
(e.g., failures) or event matching (e.g., generate a log entry if
an event happens) via a configurable value.
Discussion
Traditionally, log events are generated on exceptions, such as
failures or errors. Often this is not sufficient as a network
operator cannot tell if an attacker failed to log into a device
once, or failed once and then succeeded on the second try.
Devices should be configurable to allow for log messages on
failures, successes, or everything.
Supported Practices
* Log all login events to a device but have only the collection
device alert on failures.
* Log successful device configuration changes since one must be
aware of all modifications on some types of devices.
Current Implementations
Some ISPs put in passive devices to see routing updates and
withdrawals, so that they do not rely solely on the device for log
files.
Considerations
None.
2.13. Logs Contain Untranslated IP Addresses
Capability
The device is capable of NOT using the DNS name of the log message
generating device in event messages and logs. The device will use
the IP Address of the log message generator in its logs.
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Discussion
Although sometimes less obtuse than DNS names, IP address
assignments tend to be more stable than DNS entries. If an
operator is trying to correlate a historical event, the DNS name
may have been changed from that used at the event. To ease this
confusion, the IP address of the source of the action that caused
the log event should be retained in the log entry.
Supported Practices
* Include the source IP address in all log messages.
* Although a corresponding DNS name is useful, DNS lookups can be
slow and consume resources.
Current Implementations
Most devices include the source IP in event logs
Considerations
A failed network login should generate a record with the source
address of the login attempt, but the Source addresses may be
spoofed. Network-based attacks often use spoofed source addresses
so they should not be completely trusted unless verified by other
means. Having accurate timestamps in the logs increases the
chances that the use of an address can be correlated to an
individual.
2.14. Logs Contain Records Of Critical Security Events
Capability
The device is capable of generating a log event for at least the
following events:
* authentication successes
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* authentication failures
* session termination
* authorization changes
* configuration changes
* device status changes
Discussion
The main function of any of these log messages is to see what the
device is doing, as well as to try and ascertain what certain
malicious attackers are trying to do.
Typically, the data logged will contain the source and destination
IP addresses and layer 4 port numbers as well as a timestamp.
Supported Practices
* Examples of events recorded include: user logins, bad login
attempts, logouts, user privilege level changes, configuration
commands issued by privileged users, and system startup/
shutdown events.
Current Implementations
Most devices crudely support this capability.
Considerations
This list is far from complete. Note that there may be privacy or
legal considerations when logging/monitoring user activity or
personal information.
This is an important capability because it supports individual
accountability and auditing as well as forensics. See section
4.5.4.4 of Site Security Handbook [RFC2196].
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2.15. Logs Contain Records of General Security Events
Capability
The device is capable of generating a log record for all other
security related events including filtering (or ACL) exceptions,
routing protocol state changes, all device access (regardless of
authentication success or failure), all commands issued to a
device, and all routing events (boot-up/flaps).
Discussion
The main function of any of these log messages is to see what the
device is doing as well as to try and ascertain what certain
malicious attackers are trying to do.
Typically the data logged will contain the source and destination
IP addresses and layer 4 port numbers as well as a timestamp.
Supported Practices
* Examples of events recorded include: ACL matches, filtering
exceptions, and individual configuration commands issued by
users.
Current Implementations
Most devices crudely support this capability.
Considerations
This list is far from complete. Note that there may be privacy or
legal considerations when logging/monitoring user activity or
personal information.
This is an important capability because it supports individual
accountability and auditing as well as forensics. See section
4.5.4.4 of the Site Security Handbook.
2.16. Logs Do Not Contain Senstitvie Data
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Capability
By default configuration, the device is capable of excluding
sensitive data such as passwords, plaintext cryptographic keys,
and sensitive configuration information, from all audit records
including records of successful or failed authentication attempts.
Discussion
A user may make small mistakes in entering a password such as
using incorrect capitalization ("my password" vs. "My Password").
Event logs are traditionally dispersed widely so unexpected events
will be noticed. Unauthorized access to event logs that contain
these mistakes may compromise more than just the network devices
as most users do not have independent passwords for every system.
Supported Practices
* Login failure log messages include the failed username,
timestamp, and source IP address, but not the password used.
Current Implementations
Access control and authorization requirements differ for
accounting records (logs) and authorization databases (passwords).
Logging passwords may grant unauthorized access to individuals
with access to the logs. Logging failed passwords may also give
hints about actual passwords. See section 4.5.4.4 of Site
Security Handbook.
Considerations
There may be situations where it is appropriate/required to log
passwords, such as when performing real-time attack analysis.
Caution is advised in these rare circumstances.
Even with that caution, there's a remaining risk with logging user
names, since many users accidentally type in their password for
the username. One way to mitigate this risk is to log only
usernames that actually do exist but this adds considerable
complexity to a logging system and might allow a different attack
vector.
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2.17. Devices Should Log Every Message
Capability
Devices should be capable of being configured to either log every
event (possibly with operational degradation) or to drop events
due to congestion. If used, the drop capability should be
configurable as described in 2.18
Discussion
Many devices implement logging as an afterthought with the device
dropping log messages or failing to log critical events when the
device is "busy." This behaviour makes forensic analysis
difficult, if not impossible. Devices should be configurable to
not drop log events. The goal is to be able to enable or disable
this feature at times when collection of log messages may trump
operational stability.
Supported Practices
* Use multiple logging devices and collectors to capture enough
extra messages if one collector is not powerful enough to
recreate a full log.
* Use less complex local logging to collect every event as a
backup to remote log message omissions.
* Use creative aggregation techniques to capture the essence of
every log message but not the overhead of repeated logging, as
some versions of the syslogd implementation do when they report
"same message received 5 times" instead of logging all five
instances.
Current Implementations
Most current implementation use multiple logging devices and
caution the user when enabling full logging features.
Considerations
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Improper configuration or implementation of this capability may
open a device, network, or logging infrastructure to a self-
inflicted denial of service attack. With that caution, there are
also times when the collection of every log message is important
for short time periods.
2.18. Log Drop Policy Should be Configurable
Capability
The device is capapable of being configured to drop log messages
due to message volume or storage space constraints. The device
should be configurable to either: a) stop logging to all devices,
b) drop the oldest log messages, or c) stop logging to the local
device, when the local logging device is full.
Discussion
All log devices experience a time when there are more log messages
being generated than the system can handle or the local log
storage becomes full. Depending on the situation, the operator
may want to stop local logging as they are rectifying the logging
component, an re-enable it when the many-log-message activity is
completed.
A serious concern is to not allow the logging system to be totaly
disabled for extended periods of time.
Supported Practices
* Disable local logging to conserve log device resources and use
the remote log messages to rectify the situation.
* Disable local logging to retain the initial log messages of the
event and use the remote log messages for operation.
* Drop old log messages and retain a full log record at the
remote log message collector.
* Stop logging to all devices as troubleshooting progresses and
re-enable logging at the return to normal operations.
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Current Implementations
Some syslog implementations implement a subset of this capability;
other implementation perform quite poorly.
One implementation possibility is to use a Unix-style syslog
privilege mechanism, where log messages are divided into
categories. Each category has the drop capability so low-value
messages could be dropped while still delivering or recording
security critical messages to the collection devices.
Considerations
Improper configuration of this capability may cause the complete
loss of log messages, which should be considered a serious event.
An administrator or privileged account may be required to
configure this capability. Conversely, the log message collector
could run monitoring to raise an alarm if log messages are not
received periodically from critical devices.
This capability could be extended to include a time-out period
such that if a device would restart logging if it was disabled for
more than a certain time period.
2.19. Local Log Storage Notification
Capability
The device is capable of notifying remote log collectors if the
local log storage device is in danger of complete exhaustion.
Discussion
A remote log message collector may be unaware that the local log
storage device is nearly full and will stop accepting more log
message relatively soon. The log device should generate a
notification of some type to the remote log collectors so they are
aware of the fact. Since most operators perform analysis on the
remote copy of log messages, the operator would at least be aware
that they should rectify the situation
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Supported Practices
* Send a message to the remote log collectors when the local
storage device is 95% full.
Current Implementations
Some versions of syslog can be configured to provide this
capability.
Considerations
How the log device determines the right threshold (i.e. 95% vs
85%) to send out the notice and whether said notice is also
captured in the local storage is expected to be vendor specific.
2.20. Syslog-specific Capabilties
The predominant logging mechanism within network infrastructures is
BSD-syslog and its variants. With such widespread use, this section
identifies capabilities specific to syslog.
2.20.1. Configurable Facility Values
Capability
The device is capable of allowing for the selection of the syslog
facility number via configuration.
Discussion
A network operator may have many similar devices in their network.
The ability to segregate different severity events by the
strategic use of the syslog facility number is extremely useful.
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Supported Practices
* Authentication log entries are marked at a different facility
code to allow for easier segregation at the event collector.
Current Implementations
Some devices support this capability via a configuration variable.
Considerations
None.
2.20.2. Configurable Destination UDP Port
Capability
Devices are capable of allowing for the configuration of the
destination syslog UDP port number.
Discussion
In large logging environments, spreading the load amongst multiple
receiving daemons is a useful optimization. This capability also
allows operators to differentiate between different device
functions very easily, for example all backbone router log to port
512 and all access router log to port 513.
Supported Practices
* Send all backbone routers log to port 512 and all access router
log to port 513.
Current Implementations
Some devices support this capability via a configuration variable.
Considerations
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None.
2.21. SNMP-specific capabilities
Another common logging mechanism uses the notification messages of
the Simple Network Management Protocol [RFC3411].
2.21.1. Read-only Operations Supported
Capability
The device is capable of disabling SNMP write operations to the
device.
Discussion
Since SNMP is used as a management protocol in addition to its
logging functionality, the ability to disable operations that
would change the device operations should be supported for those
devices that aren't using the management functions.
Supported Practices
* Disable SNMP write operations.
Current Implementations
Some devices support this capability via a configuration variable.
Considerations
None.
2.21.2. Restrict Sources of SNMP Queries
Capability
The device is capable of restricting the IP addresses that can
query the SNMP interface for event data.
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Discussion
Since event data can educate an adversary, devices should be able
to only send event data ("responses") to certain, configured IP
addresses, not any system that interrogates them. See [RFC3413].
Supported Practices
* Configure devices to only accept SNMP requests from authorized
addresses.
Current Implementations
Some devices support this capability via a configuration variable.
It may also be implemented using packet or traffic filtering to
the device. See [I-D.ietf-opsec-filter-caps].
Considerations
None.
2.21.3. Only Return Specific Data to Requestor
Capability
The device is capable of delivering specific managed object data
(e.g., values linked to a specific OID) instead of returning all
event data for the device (e.g., an entire OID subtree).
Discussion
Since event data can educate an adversary, devices should be able
to only send specific event data instead of returning all the data
in every query. See [RFC3415].
Supported Practices
* Queries request specific OID values instead of dumping the
entire MIB. This practice reduces event data volume in
addition to attaining security.
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Current Implementations
Most devices support this capability.
Considerations
None.
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3. Security Considerations
Security capabilities of network devices is the subject matter of
this entire memo. The capabilities listed cite practices in
[RFC4778] that they are intended to support. RFC4778 Also defines
the general threat model, practices, and lists justifications for
each practice.
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4. IANA Considerations
There are no IONA actions required by this document.
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5. Informative References
[I-D.ietf-opsec-filter-caps]
Morrow, C., "Filtering and Rate Limiting Capabilities for
IP Network Infrastructure",
draft-ietf-opsec-filter-caps-09 (work in progress),
March 2007.
[I-D.ietf-syslog-protocol]
Gerhards, R., "The syslog Protocol",
draft-ietf-syslog-protocol-21 (work in progress),
June 2007.
[I-D.ietf-syslog-transport-tls]
Miao, F. and M. Yuzhi, "TLS Transport Mapping for Syslog",
draft-ietf-syslog-transport-tls-10 (work in progress),
May 2007.
[RFC1305] Mills, D., "Network Time Protocol (Version 3)", RFC 1305,
March 1992.
[RFC1492] Finseth, C., "An Access Control Protocol, Sometimes Called
TACOS", RFC 1492, July 1993.
[RFC2196] Fraser, B., "Site Security Handbook", RFC 2196,
September 1997.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)",
RFC 2865, 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.
[RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An
Architecture for Describing Simple Network Management
Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
December 2002.
[RFC3413] Levi, D., Meyer, P., and B. Stewart, "Simple Network
Management Protocol (SNMP) Applications", STD 62,
RFC 3413, December 2002.
[RFC3414] Blumenthal, U. and B. Wijnen, "User-based Security Model
(ISM) for version 3 of the Simple Network Management
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Protocol (SNMPv3)", STD 62, RFC 3414, December 2002.
[RFC3415] Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based
Access Control Model (CACM) for the Simple Network
Management Protocol (SNMP)", STD 62, RFC 3415,
December 2002.
[RFC3871] Jones, G., "Operational Security Requirements for Large
Internet Service Provider (ESP) IP Network
Infrastructure", RFC 3871, September 2004.
[RFC4330] Mills, D., "Simple Network Time Protocol (SMTP) Version 4
for IPv4, IPv6 and OSI", RFC 4330, January 2005.
[RFC4778] Kaeo, M., "Operational Security Current Practices In
Internet Service Provider Environments", RFC 4778,
January 2007.
[SP800-92]
Souppaya, M. and K. Kent, "Guide to Security Log
Management", FIPS 800-92, April 2006.
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Authors' Addresses
Patrick Cain
The Cooper-Cain Group, Inc.
P.O. Box 400992
Cambridge, MA 02140
U.S.A.
Phone: +1 617-848-1950
Email: pcain@coopercain.com
George Jones
Port111 Labs.
Email: gmj3871@pobox.com
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