SYSLOG, NetConf, NetFlow

W.lilakiatsakun

syslog (1)

• The purpose of syslog is to write system messages to a log

• Syslog messages can include everything from critical alarm conditions to ordinary debugging statement

• It provides a general trail of activities • It provides the capability for the device to

emit event messages without solicitation

syslog (2)

• Syslog message has 2 parts– A message header and the message body

• The message body contains the content of the message itself (english text, unstructured)

• The message header contains minimal but essential information in structured manner

General syslog message

• 179.19.209.130 – IP Address• 000024 – sequence number• Apr 12 18:01:55:643 – local time• ENV_MON – facility emitting the alarm• 1 – severity• SHUTDOWN – Event

syslog Protocol

• IETF is in process of passing a particular version of syslog as a standard– RFC 3164 BSD syslog protocol– RFC 3195 reliable delivery for syslog

• Refer to RFC3164 – UDP is used as transport service– Port 514

definition

• A machine that can generate a message will be called a "device".

• A machine that can receive the message and forward it to another machine will be called a "relay".

• A machine that receives the message and does not relay it to any other machines will be called a "collector". This has been commonly known as a "syslog server".

syslog message

• Consists of 3 parts :PRI /HEADER/MSG• Total length 1024 bytes or less

PRI (Priority) part

• Priority – combination of a facility and severity – Facility – category of a message (kernel message) , it

is a numeric code – Severity – numeric code 0 -7 , 0 is the most severe– Priority is formed by multiplying the numeric code of

the facility by 8 and adding the severity – Facility 7 and severity 3 , so priority = 59

Example of Facility code

Example of Severity

HEADER part (1)

• The HEADER part contains a timestamp and an indication of the hostname or IP address of the device

• The HEADER part of the syslog packet MUST contain visible (printing) characters (7-bit Ascii)

• HOSTNAME field will contain the hostname or IP address

• Timestamp field will contain the local time and is in the format of “Mmm dd hh:mm:ss"

HEADER part (2)

• Mmm –month of the year with the first character in uppercase and the other two characters in lowercase“Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec”

• dd -dd is the day of the month. – If the day of the month is less than 10, then it MUST be

represented as a space and then the number. • For example,– the 7th day of August would be represented as "Aug 7", with

two spaces between the "g" and the "7

HEADER part (3)

• hh:mm:ss is the local time. • The hour (hh) is represented in a 24-hour for

mat. – Valid entries are between 00 and 23

• The minute (mm) and second (ss) entries are between 00 - 59

MSG part (1)

• It contains some additional information of the process that generated the message, and then the text of the message

• It has 2 fields : TAG and CONTENT• TAG field will be the name of the program or process that generated the message.(not exceed 32

chars) • CONTENT field contains the details of the message. – This has traditionally been a freeform message that gives some

detailed information of the event

Example of syslog message

• <34> Oct 11 22:14:15 mymachine su: su root failed on /dev/pts/8

• <34> - priority• Oct 11 22:14:15 – timestamp• mymachine – hostname• su – TAG• “su root’ failed for on /dev/pts/8 “- Content

Security consideration (1)

• Authentication– The syslog delivery mechanism does not strongly a

ssociate the message with the message sender– a misconfigured machine may send syslog messag

es to a collector representing itself as another machine

– An attacker may transmit syslog messages to a collector.

Security consideration (2)

• Sequenced delivery– the syslog process and protocol do not ensure ordered

delivery.• Reliable delivery– no mechanism within either the syslog process or the p

rotocol to ensure delivery– May be maliciously intercepted or discarded

• Message Integrity– syslog messages may be damaged in transit or an attac

ker may maliciously modify them.

Security consideration (3)

• Message observation– No mechanisms to provide confidentiality of the

messages in transit. (clear-text messages) • Message Prioritization & Differentiation– No mechanism relating to priority message– Critical message and non critical message can be

treated as equal in term of reception

Security consideration (4)

• Misconfiguration– The syslog message may go to untended receiver

• Load Considerations– An attacker may perform a Denial of Service attac

k by filling the disk of the collector with false messages.

syslog deployment (1)

• Two roles are distinguished – syslog sender (management agent)– syslog receiver (management manager)

• Syslog receiver (1)– Device itself writing the messages to a local log

file • use circular log file for a limit size• Log files are created with a certain capacity

syslog deployment (2)

Circular log file

syslog deployment (3)

• syslog receiver (con’t)– Centralized logging host• Receiving messages from several devices and logging

those messages• Applications access this logging host instead of

individual devices

– Syslog relay , forwarding syslog messages to various apps.

syslog deployment (4)

Logging host

syslog relay

Netconf (1)

• Netconf is a network management protocol developed in the IETF by the Netconf working group.

• It was published as RFC 4741.• The NETCONF protocol provides mechanisms to

install, manipulate, and delete the configuration of network devices.

• It also can perform some monitoring functions.

Netconf (2)

• It uses an Extensible Markup Language (XML) based data encoding for the configuration data as well as the protocol messages.

• The NETCONF protocol operations are realized on top of a simple Remote Procedure Call (RPC) layer.

Netconf Datastore (1)

• The configuration information of devices can be thought of and handle as being contained in a datastore (like a file)

• The datastore resembles a MIB.• Netconf provides the operations to manage those

datastores.– SNMP targets the individual managed object in side MIB – Netconf targets the MIB as a whole or portion

Netconf Datastore (2)

A hierarchical datastore in NetconfA hierarchical datastore in Netconf

Netconf Datastore (3)

• Management operations can be applied to individual subtrees

• This capability feature is called as subtree filtering

State Data and Configuration Data (1)

• The information that can be retrieved from a running system is separated into two classes, configuration data and state data.

• Configuration data is the set of writable data that is required to transform a system from its initial default state into its current state

• State data is the additional data on a system that is not configuration data such as read-only status information and collected statistics

State Data and Configuration Data (2)

• NETCONF protocol recognizes the difference between configuration data and state data and provides operations for each.

• The <get-config> operation retrieves configuration data only.

• The <get> operation retrieves configuration and state data.

Netconf and XML (1)

• Netconf uses XML as encoding for its management operations

• XML documents contain so-called tags to delimit different pieces of information

• Tags are defined by users such as <email>alex@cisco.com(/email)

Netconf Architecture (1)

Netconf Architecture (2)

• Transport layer - NETCONF implementation MUST support the SSH transport protocol mapping Secure (Authentication, Integrity, and Confidentiality )– Block Extensible Exchange Protocol (BEEP) RFC4744– Simple Object Access Protocol (SOAP) RFC4743

• Remote Procedure Call layer– Allow manager to invoke function on agent– rpc request / rpc reply

Netconf Architecture (3)

• The operation layer– To manipulate configuration files– Get-config / Edit-config

• The content layer – Configuration data

• The management information will be transported and exchanged as XML documents

Netconf Message Structure

• Fig 8-14

A netconf request (1)

• Ex 8-4

A netconf request (2)

• RPC tag <rpc message-id =“101 … > …. </rpc>

– The <rpc> element has a mandatory attribute "message-id", which is an arbitrary string chosen by the sender of the RPC that will commonly encode a monotonically increasing integer.

– The receiver of the RPC does not decode or interpret this string but simply saves it to be used as a "message-id" attribute in any resulting <rpc-reply> message.

A netconf request (3)

• Namespace – All NETCONF protocol elements are defined in the following

namespace:urn:ietf:params:xml:ns:netconf:base:1.0

• Netconf operation – <get-config> … </get-config>

• Netconf Data addressing– <source>… </source> specifies the address of data – <filter> … </filter> specifies the subtree

A netconf reply

• Ex 8-5

Management operations

• Get-config – to retrieve config file (default is running config)

• Get – to retrieve state information • Edit-config – to modify or change a configuration• Copy-config – to copy new configuration• Delete-config – to remove a configuration• Lock and unlock – to protect configuration file

Security Consideration (1)

• Configuration information is by its very nature sensitive. – Its transmission in the clear and without integrity

checking leaves devices open to classic eavesdropping attacks.

• Configuration information often contains passwords, user names, service descriptions, and topological information, all of which are sensitive.

Security Consideration (2)

• The protocol, therefore, must minimally support options for both confidentiality and authentication. (SSH, BEEP, etc)

Netflow protocol /IPFIX (1)

• RFC 3954 (Netflow V.9) • RFC 5101 (IPFIX- aka. Netflow V.10)• Netflow was introduced by cisco to collect data

about networking traffic from a device.– Who are the top “talker” in the network– How much traffic is being exchanged between two

destination– How are links in the network being used– Where are the traffic bottlenecks in the network?

Netflow protocol /IPFIX (2)

• Netflow communicates statistical information about IP-based data traffic that flow over router

• The statistics are provided on a per-flow basis • A flow consists of all traffic that belongs to the

same communication context– A file–transfer application ,all packets belong to the

same transfer

• Fig 8-15

Flow

• Identified by the following information• Source address/Source port• Destination address/Destination port• Protocol type (TCP or UDP)• Type of service (TOS)• Input logical interface (same index in SNMP MIB)• Flow record includes the keys that identify the flow as

well as the time when flow started /stopped /how many packets were transported

Terminology (1)

• Observation Point– An Observation Point is a location in the network

where IP packets can be observed; for example, one or a set of interfaces on a network device like a router.

• Observation Domain– The set of Observation Points that is the largest

aggregatable set of flow information at the network device with NetFlow services enabled is termed an Observation Domain.

Terminology (2)• IP Flow or Flow– Set of IP packets passing an Observation Point in the

network during a certain time interval. – All packets that belong to a particular Flow have a set

of common properties derived from the data contained in the packet and from the packet treatment at the Observation Point.

• Flow Record– A Flow Record provides information about an IP Flow

observed at an Observation Point. – The Flow Data Records are also referred to as NetFlow

services data and NetFlow data.

Terminology (3)

• Exporter– A device (for example, a router) with the NetFlow

services enabled, the Exporter monitors packets entering an Observation Point and creates Flows from these packets.

– The information from these Flows is exported in the form of Flow Records to the NetFlow Collector

Terminology (4)

• NetFlow Collector– The NetFlow Collector receives Flow Records from

one or more Exporters. – It processes the received Export Packet(s); that is,

it parses and stores the Flow Record information. – Flow Records can be optionally aggregated before

being stored on the hard disk.

Benefit

• Allow network managers to account for detailed network use by individual users– Charge based on actual traffic consumption

• Provide a wealth of data for traffic analysis, bottleneck and network planning

• Provide tool to spot and defend against attacks on a network

Netflow Protocol

• Netflow version5 is commonly used • The newest version is RFC 3954 (version 9)• Flow information is exported from the router in User D

atagram Protocol (UDP) or Stream Control Transmission Protocol (SCTP) packets and collected using a netflow collector.

• Juniper Networks provides a similar feature for its routers called Jflow .

• Huawei Technology routers also support the same technology, but call it NetStream

Netflow packet structure

Packet structure

• Header– Sequence number of the packet– The number of flow records contained in the Netflow

packet– The version number of the netflow protocol itself

• Flow record– keys to identify flow – Start/finish time– Statistical data

Finishing the flow (1)

• 1. If the Exporter can detect the end of a Flow. For example, if the FIN or RST bit is detected in a TCP [RFC793] connection, the Flow Record is exported.

• 2. If the Flow has been inactive for a certain period of time. This inactivity timeout SHOULD be configurable at the Exporter, with a minimum value of 0 for an immediate expiration.

Finishing the flow (2)

• 3. For long-lasting Flows, the Exporter SHOULD export the Flow Records on a regular basis. This timeout SHOULD be configurable at the Exporter.

• 4. If the Exporter experiences internal constraints, a Flow MAY be forced to expire prematurely; for example, counters wrapping or low memory.

Security Consideration (1)

• Disclosure of Flow Information Data– Export Packets are not encrypted, the observation

of Flow Records can give an attacker information about the active flows in the network, communication endpoints and traffic patterns.

– This information can be used both to spy on user behavior and to plan and conceal future attacks. The information that an attacker could derive from the interception of Flow Records depends on the Flow definition.

Security Consideration (2)

• Forgery of Flow Records or Template Records– If Flow Records are used in accounting and/or

security applications, there may be a strong incentive to forge exported Flow Records (for example to defraud the service provider, or to prevent the detection of an attack).

– This can be done either by altering the Flow Records on the path between the Observer and the Collector, or by injecting forged Flow Records that pretend to be originated by the Exporter.

Security Consideration (3)

• Attacks on the NetFlow Collector– Denial of service attacks on the NetFlow Collector

can consume so many resources from the machine that, the Collector is unable to capture or decode some NetFlow Export Packets. Such hazards are not explicitly addressed by the NetFlow Version 9 protocol, although the normal methods used to protect a server from a DoS attack will mitigate the problem.

Example of Export Packet (1)

Example of Export Packet (2)

Example of Export Packet (3)

Management protocol positioning