Ali shahbazi khojasteh dot1X

Dot1X & EAPByAli Shahbazi

• 802.1x works at Layer 2 to authentication and authorize devices on wireless access points.

IEEE 802.1x

• It is used for certain closed wireless access points.

802.1x Authentication• A wireless node must be authenticated before it can gain

access to other LAN resources

• It does assume a point-to-point model.

• Then PPP can serve for this point-to-point model.

802.1x Authentication

What is PPP and what does it have to do with wireless security?

• Most people are familiar with PPP, the point-to-point protocol. It’s most commonly used for dial-up Internet access.

• PPP is also used by some ISPs for DSL and cable modem authentication, in the form of PPPoE (PPP over Ethernet).


• By any measure, PPP is a very successful protocol.

• In practice, PPP has gone far beyond its original use as a dial-up access method as it's now used all over the Internet.


• Although PPP has many parts that make it useful in different networking environments, the part that we care about in this demonstration is the authentication piece.


• Before anything at Layer 3 (like IP) is established, PPP goes through an authentication phase at Layer 2.

• With dial-up Internet access, that’s the username and password.


• PPP authentication is used to identify the user at the other end of the PPP line before giving them access.

• By authenticating at layer 2, you are independent of upperlayer protocol (such as IP).


• And you can make decisions on how to handle layer 3 protocols, such as IP, based on the authentication information.

• For example, depending on what authentication information you provide, you might get a particular IP address.

PPP General Frame Format

802.1x Terminology

• 802.1x does introduce some terminology that we need to get used to.

• An authenticator helps authenticate what you connect to it. It does this via the authentication server.

• The supplicant is what is being authenticated. See the following diagram if that's unclear.

802.1x Terminology

802.1x Terminology

• The Port Access Entity (PAE) is what executes the algorithms and follows the protocol(s).

• Each of the three items above has a PAE, but the PAE software does do different things on each of the three.

How did EAP get into the picture?

• As PPP use grew, people quickly found its limitations, both in flexibility and in level of security, in the authentication methods, such as PAP.


• Most corporate networks want to do more than simple usernames and passwords for secure access.

• So a new authentication protocol, called the Extensible Authentication Protocol (EAP) was designed.

What is EAP

EAP

• Extensible Authentication Protocol is a universal authentication framework frequently used in wireless networks and Point-to-Point connections.

• It is defined by RFC 3748.

http://en.wikipedia.org/wiki/Authentication

http://en.wikipedia.org/wiki/Wireless_LAN

http://en.wikipedia.org/wiki/Point-to-Point_Protocol

http://tools.ietf.org/html/rfc3748

EAP and WPA

• WPA and WPA2 standard has officially adopted five EAP types as its official authentication mechanisms.

• EAP is a way for a supplicant to authenticate, usually against a back-end RADIUS server.

• EAP comes from the dial access world and PPP.

EAP and WPA

• There is a RFC for how RADIUS should support EAP between authenticator and authentication server, RFC 3579.

• EAP was first defined in the IETF RFC 2284.

EAP and WPA

• The EAP TLS variant is defined in RFC 2716.

• The following figure shows the EAP format.

• Note that when 802.1x is the transport, all this fits into the 802.1x payload field, with EAPOL packet type set to 0 (EAP packet).

EAP and WPA

The EAPOL frame format

• EAP is a way for a supplicant to authenticate, usually against a back-end RADIUS server.

• EAP comes from the dial access world and PPP.

EAP and WPA

• There is an RFC for how RADIUS should support EAP between authenticator and authentication server, RFC 3579.

EAP and WPA

• EAP was first defined in the IETF RFC 2284.

• The EAP TLS variant is defined in RFC 2716.

EAP and WPA

• The following figure shows the EAP format.

• Note that when 802.1x is the transport, all this fits into the 802.1x payload field, with EAPOL packet type set to 0 (EAP packet).

EAP and WPA

EAP format

• The code field indicates the type of EAP packet as follows: (1) Request, (2) Response,

(3) Success, (4) Failure

• The ID is one byte for matching requests and responses.

• Length is the byte count including the code, ID, length and data fields.

• The data field format varies depending on the code field.

EAP format

• Types 3 and 4, Success and Failure are easy to describe: they have no data field (0 bytes).

• Types 1 and 2 share a format. It boils down to a type code (one byte) then the data for that type.

EAP format

• Here's what that makes the EAP packet look like:

EAP format

• The original RFC defines several types of EAP authentication. They are:

1 Identity2 Notification3 Nak (response only)4 MD5-Challenge5 One-Time Password (OTP) (RFC 1938)6 Generic Token Card

13 TLS (RFC 2716 adds TLS)

EAP format

• The RFC's contain some great diagrams showing the sequence of messages for the above EAP variants.

EAP format

• The IEEE 802.1x standard goes through all this for EAP-OTP in a couple of different scenarios (supplicant initiated exchange, authenticator initiated, etc.).

EAP format


• EAP sits inside PPP’s authentication protocol.

• It provides a generalized framework for all sorts of authentication methods.

EAP Message

• Exactly one EAP packet is encapsulated in the Information field of a PPP Data Link Layer frame and building a PPP EAP Message.

• Where the protocol field indicates type hex C227 (PPP EAP).


• By pulling EAP out (destacando) into a separate protocol, it then has the option of re-use in other environments - like 802.1X.


• EAP is supposed to head off (desviar) proprietary authentication systems and let everything from passwords to challenge-response tokens and PKI certificates work smoothly.


• With a standardized EAP, interoperability and compatibility across authentication methods becomes simpler.


• Only the client and the authentication server have to be coordinated.

• By supporting EAP authentication, a RAS server (in wireless this is the AP) gets out of the business of actively participating in the authentication dialog ...


• For example, when you dial a remote access server (RAS) and use EAP as part of your PPP connection, the RAS doesn’t need to know any of the details about your authentication system.


• ... ... and just re-packages EAP packets to hand off to a RADIUS server to make the actual authentication decision.

How 802.1x Works

• The 802.1x access control works on unaggregated physical ports at OSI Layer 2. It allows or denies access.

• The access control it exerts can govern bidirectional or inbound traffic.

How 802.1x Works

• On LAN media, 802.1x needs some way to communicate between the Supplicant and the Authenticator. This happens directly at Layer 2.

• The protocol used is EAPOL, which stands for EAP encapsulation over LANs.

How 802.1x Works

• EAP is a separate protocol (or family of protocols) for authentication.

• Let's take a look at the EAPOL frame format. It is shown in the following figure:

How 802.1x Works


• The packet type is as follows:

• 0 EAP Packet1 EAPOL Start2 EAPOL Logoff3 EAPOL Key4 EAPOL Encapsulated Alert


• The key packet type is used for EAP variants that allow an encryption key.

• The packet body is then a Key Descriptor, with specified fields. We'll skip the details.


• The Alert EAP packet type allows for things (like SNMP) to be sent through a port where the authentication resulted in an unauthorized state.


• The standard notes that use in a shared environment is highly insecure unless the supplicant to authenticator traffic is a secure association, i.e. encrypted.


• The authenticator then uses a standard protocol, usually RADIUS, to relay information to and from the authentication server.


• The following figure shows how the protocol works.

• It basically provides a L2 wrapper to transport EAP information between supplicant and authenticator.


• Note that the EAPOL-Start message is only used if the supplicant initiates the exchange.

• The authenticator can notice link status has changed, and just jump right in with the EAP exchange.


• It may seem a little silly, having a big diagram with only a couple of arrows in it. I hope that this emphasizes the key point here.


• The double arrow goes further since we'll see that the authenticator re-encapsulates the EAP information, typically within RADIUS, and passes it through to the authentication server.


IEEE 802.1

• IEEE 802.1 is a working group of the IEEE 802 project of the IEEE. It is concerned with:• 802 LAN/MAN architecture • internetworking among 802 LANs, MANs and other wide

area networks, • 802 Link Security (This is not wireless), • 802 overall network management, and • protocol layers above the MAC & LLC layers.

What Is 802.1x?

• IEEE 802.1x is an IEEE standard for port-based Network Access Control which extends the 802.1.

• it is part of the IEEE 802.1 group of protocols.

• It provides authentication to devices attached to a LAN port, establishing a point-to-point connection or preventing access from that port if authentication fails.

• The standard 802.1x is an IEEE standard for Port-Based Network Access Control.

What Is 802.1x?

IEEE 802.1x - a port based authentication protocol

• From the introduction to the 802.1x standard document, with some omissions:

What Is 802.1x?

• "Port-based network access control makes use of the physical access characteristics of IEEE 802 LAN infrastructures in order to provide a means of authenticating and authorizing devices attached to a LAN port [...],

What Is 802.1x?

• and of preventing access to that port in cases in which the authentication and authorization process fails. [...]

What Is 802.1x?

• Examples of ports in which the use of authentication can be desirable include the Ports of MAC Bridges, [...] ,

• and associations between stations and access points in IEEE 802.11 Wireless LANs."

What Is 802.1x?

• That is, 802.1x and EAPOL just exist as a way to transport EAP information between Supplicant and Authenticator.

What Is 802.1x?

How This All Works

• The RFC's contain some diagrams showing the sequence of messages for the above EAP variants.

How This All Works

• The IEEE 802.1x standard goes through all this for EAP-OTP in a couple of different scenarios (supplicant initiated exchange, authenticator initiated, etc.).

How This All Works

• This fills in the big EAP arrow in the above diagram to show the full sequence of messages.

• The following figure shows my version of the sequence of messages for EAP-OTP (One Time Password).

How This All Works

Medium to large Enterprise

WLAN Security

EAP

• Extensible Authentication Protocol is a universal authentication framework frequently used in wireless networks and Point-to-Point connections.

• It is defined by RFC 3748.

• Although the EAP protocol is not limited to wireless LANs and can be used for wired LAN authentication, it is most often used in wireless LANs.

EAP

WPA

• WPA and WPA2 standard has officially adopted five EAP types as its official authentication mechanisms.

• EAP is an authentication framework, not a specific authentication mechanism. It only defines message formats.

WPA

• The EAP provides some common functions and a negotiation of the desired authentication mechanism.

• Such mechanisms are called EAP authentication methods.

WPA

• Each protocol that uses EAP defines a way to encapsulate that protocol's messages within the EAP messages.

• In the case of 802.1x, this encapsulation is called EAPOL, "EAP over LANs".

WPA

Level 3: Medium to large Enterprise WLAN security

• EAP-TLS could be the recommended authentication method for this security level.

• EAP-TLS have the same server and client side digital certificate requirements.

• To implement EAP-TLS, not only does the server require a Digital Certificate but the users as well.


• This means you will need Certificate Authority to issue a proper Server Digital Certificate on a pair of dedicated RADIUS servers and not just a Self Signed Certificate on a makeshift RADIUS Server.


• For this security level, the proper PKI best practices should be followed.

• There should be at least a single dedicated PKI Root Certificate Authority, but preferably it should at least be a 2 or 3 tier PKI design.


• A two tier chain for a medium Enterprise organization would have an offline Root Certificate Authority and an online Issuing Certificate Authority.


• The reason for this is that if a Certificate Authority is ever compromised, you can revoke it and create a new one ...

• ... from the higher offline Certificate Authorities without having to start your PKI deployment from scratch.


• Building a PKI from scratch because of a compromised Certificate Authority would be completely unacceptable in a large scale environment.


• A large Enterprise should implement the three tier design with offline Root Certificate Authority, offline subordinate Certificate Authority, and online Issuing Certificate Authority.


• Methods defined in IETF RFCs include:• EAP-MD5, • EAP-OTP, • EAP-GTC, • EAP-TLS or EAP-TTLS, • EAP-IKEv2, • EAP-SIM, • EAP-AKA


• Some commonly used methods capable of operating in wireless networks include:• EAP-TLS, • EAP-TTLS

• Requirements for EAP methods used in wireless LAN authentication are described in RFC 4017.


THANKS

Ali shahbazi khojasteh dot1X

Engineering