Home > Articles > Security > Network Security

  • Print
  • + Share This
This chapter is from the book

Understanding Authentication Policies

Now that you understand the four main responsibilities of the Authentication Policy, it will be easier to understand why you are doing the things that are introduced in this section. To understand Authentication Policies even more, let’s examine a few.

From the ISE GUI, navigate to Policy > Authentication. Notice the default, as displayed in Figure 13-1.

Figure 13-1

Figure 13-1. Default Authentication Policy

Basic Authentication Policy rules are logically organized in this manor:

  • IF conditions THEN ALLOW PROTCOLS IN LIST AllowedProtocolList
  • AND CHECK THE IDENTITY STORE IN LIST IdentityStore

Rules are processed in a top-down, first-match order; just like a firewall policy. So, if the conditions do not match, the authentication is compared to the next rule in the policy.

As shown in Figure 13-1, ISE is preconfigured with a default rule for MAC Authentication Bypass (MAB). Use this rule to dig into authentication rules and how they work. If you have a live ISE system, it may help to follow along with the text.

Figure 13-2 demonstrates the MAB rule in flowchart format.

Figure 13-2

Figure 13-2.MAB Rule Flow Chart

Conditions

The conditions of this rule state, “If the authentication request is Wired_MAB or Wireless_MAB, it will match this rule.” You can expand these conditions by mousing over the conditions and clicking the target icon that appears or by looking directly at the authentication conditions shown in the following steps:

  1. Navigate to Policy > Policy Elements > Conditions > Authentication > Compound Conditions.
  2. Select Wired_MAB.

    As you can see in Figure 13-3, Wired_MAB is looking for the RADIUS Service-Type to be Call-Check and the NAS-Port-Type to be Ethernet. This combination of attributes from the RADIUS authentication packet notifies ISE that it is a MAB request from a switch.

    Figure 13-3

    Figure 13-3.Wired_MAB Condition

    Figure 13-4 highlights these key attributes in a packet capture of the MAB authentication request.

    Figure 13-4

    Figure 13-4.Packet Capture of Wired MAB

  3. Navigate to Policy > Policy Elements > Conditions > Authentication > Compound Conditions.
  4. Select Wireless_MAB.

    As shown in Figure 13-5, wireless MAB is similar. However, it uses a NAS-Port-Type of Wireless - IEEE 802.11. This combination of attributes from the RADIUS authentication packet tells ISE that it is a MAB request from a wireless device.

    Figure 13-5

    Figure 13-5. Wireless_MAB Condition

Allowed Protocols

After the conditions are matched, the rule now dictates what authentication protocols are permitted. Looking at the predefined MAB rule, this rule uses the Default Network Access list of allowed protocols (which is almost every supported authentication protocol).

Let’s examine the default allowed protocols. From the ISE GUI, perform the following steps:

  1. Navigate to Policy > Policy Elements > Results > Authentication > Allowed Protocols.
  2. Select Default Network Access.

    As you can see in Figure 13-6, the list of supported protocols and their options is extensive. This default list is inclusive with the intention of making deployments work easily for customers, but security best practice is to lock this down to only the protocols needed for that rule.

    Figure 13-6

    Figure 13-6.Default Network Access

Authentication Protocol Primer

This section examines the most common authentication protocols seen in most environments, so you can create a more specific list of allowed protocols for your deployment. Let’s follow Figure 13-6, from top-down:

  • PAP: Password Authentication Protocol. The username is sent in the clear, and the password is optionally encrypted. PAP is normally used with MAB, and some devices use PAP for Web authentications. We recommend you enable this for the MAB rule only and disable PAP for any authentication rules for real authentications.

    The check box for Detect PAP as Host Lookup allows PAP authentications to access the internal endpoints database. Without this check box selected, MAB would not work.

  • CHAP: Challenge Handshake Authentication Protocol. The username and password are encrypted using a challenge sent from the server. CHAP is not often used with network access; however, some vendors send MAB using CHAP instead of PAP.

    The check box for Detect CHAP as Host Lookup allows CHAP authentications to access the internal endpoints database. Without this check box selected, MAB does not work.

Extensible Authentication Protocol (EAP) Types

EAP is an authentication framework providing for the transport and usage of identity credentials. EAP encapsulates the usernames, passwords, and certificates that a client is sending for purposes of authentication. There are many different EAP types, each one has its own benefit and downside. As an interesting sidenote, 802.1X defines EAP over LAN:

  • EAP-MD5: Uses a Message Digest algorithm to hide the credentials in a HASH. The hash is sent to the server, where it is compared to a local hash to see if the credentials are accurate. However, EAP-MD5 does not have a mechanism for mutual authentication. That means the server is validating the client, but the client does not authenticate the server (i.e., does not check to see if it should trust the server). EAP-MD5 is common on some IP-Phones, and it is also possible that some switches send MAB requests within EAP-MD5. The check box for Detect EAP-MD5 as Host Lookup allows EAP-MD5 authentications to access the internal endpoints database. Without this check box selected, MAB does not work.
  • EAP-TLS: Uses Transport Layer Security (TLS) to provide the secure identity transaction. This is similar to SSL and the way encryption is formed between your web browser and a secure website. EAP-TLS has the benefit of being an open IETF standard, and it is considered “universally supported.” EAP-TLS uses X.509 certificates and provides the ability to support mutual authentication, where the client must trust the server’s certificate, and vice versa. It is considered among the most secure EAP types, because password capture is not an option; the endpoint must still have the private key. EAP-TLS is quickly becoming the EAP type of choice when supporting BYOD in the enterprise.

Tunneled EAP Types

The EAP types previously described transmit their credentials immediately. These next two EAP types (see Figure 13-7) form encrypted tunnels first and then transmit the credentials within the tunnel:

  • PEAP: Protected EAP. Originally proposed by Microsoft, this EAP tunnel type has quickly become the most popular and widely deployed EAP method in the world. PEAP forms a potentially encrypted TLS tunnel between the client and server, using the x.509 certificate on the server in much the same way the SSL tunnel is established between a web browser and a secure website. After the tunnel is formed, PEAP uses another EAP type as an “inner method,” authenticating the client using EAP within the outer tunnel.
  • EAP-MSCHAPv2: When using this inner method, the client’s credentials are sent to the server encrypted within an MSCHAPv2 session. This is the most common inner-method, as it allows for simply transmission of username and password, or even computer name and computer passwords to the RADIUS server, which in turn authenticates them to Active Directory.
  • EAP-GTC: EAP-Generic Token Card (GTC). This inner method was created by Cisco as an alternative to MSCHAPv2 that allows generic authentications to virtually any identity store, including One-Time-Password (OTP) token servers, LDAP, Novell E-Directory and more.
  • EAP-TLS: Although rarely used and not widely known, PEAP is capable of using EAP-TLS as an inner method.
    Figure 13-7

    Figure 13-7.Tunneled EAP Types (PEAP and FAST)

  • EAP-FAST: Flexible Authentication via Secure Tunnel (FAST) is similar to PEAP. FAST was created by Cisco as an alternative to PEAP that allows for faster re-authentications and supports faster wireless roaming. Just like PEAP, FAST forms a TLS outer tunnel and then transmits the client credentials within that TLS tunnel. Where FAST differs from the PEAP is the ability to use Protected Access Credentials (PAC). A PAC can be thought of like a secure cookie, stored locally on the host as “proof” of a successful authentication.
    • EAP-MSCHAPv2: When using this inner method, the client’s credentials are sent to the server encrypted within an MSCHAPv2 session. This is the most common inner method, as it allows for simply transmission of username and password, or even computer name and computer passwords to the RADIUS server, which in turn authenticates them to Active Directory.
    • EAP-GTC: EAP-Generic Token Card (GTC). This inner method was created by Cisco as an alternative to MSCHAPv2 that allows generic authentications to virtually any identity store, including One-Time-Password (OTP) token servers, LDAP, Novell E-Directory, and more.
    • EAP-TLS: EAP-FAST is capable of using EAP-TLS as an inner method. This became popular with EAP chaining.
  • EAP Chaining with EAP-FASTv2: As an enhancement to EAP-FAST, a differentiation was made to have a user PAC and a machine PAC. After a successful machine authentication, ISE issues a machine-PAC to the client. Then, when processing a user authentication, ISE requests the machine-PAC to prove that the machine was successfully authenticated, too. This is the first time in 802.1X history that multiple credentials have been able to be authenticated within a single EAP transaction, and it is known as EAP chaining. The IETF is creating a new open standard based on EAP-FASTv2 and, at the time of publishing this book, it was to be referred to as EAP-TEAP (tunneled EAP), which should eventually be supported by all major vendors.

Identity Store

After processing the allowed protocols, the authentication request is then authenticated against the chosen identity store, or in this case with MAB, it is compared to the internal endpoints database (list of MAC addresses stored locally on ISE).

If the MAC address is known, it is considered to be a successful MAB (notice it was not termed successful authentication). MAB is exactly that, bypassing authentication, and it is not considered a secure authentication.

The selected identity source may also be an identity source sequence, which attempts a series of identity stores in order. This is covered in Chapter 21, “Monitor Mode.”

Options

Every authentication rule has a set of options that are stored with the identity store selection. These options tell ISE what to do: if an authentication fails, if the user/device is unknown, or if the process fails. The options are Reject, Continue, and Drop:

  • Reject: Send Access-Reject back to the NAD.
  • Continue: Continue to the Authorization Policy regardless of authentication pass/fail. (Used with Web authentication.)
  • Drop: Do not respond to the NAD; NAD will treat as if RADIUS server is dead.

See Chapters 20–23 for more details on when to use these options.

Common Authentication Policy Examples

This section considers a few quick examples of Authentication Policies, based on common use-case or simply because they were interesting.

Using the Wireless SSID

One of the most common Authentication Policy requests that I get is to treat authentications differently based on the SSID of the wireless network. Creating the policy is not difficult; what becomes challenging is the identification of the attribute to use, because Source-SSID is not a field in a RADIUS packet. The attribute you need to use is called-station-id. That is the field that describes the wireless SSID name.

For this example, let’s build a rule for an SSID named CiscoPress. This rule will be configured to

  • Only match authentications coming from that SSID
  • Allow only EAP-FAST authentications
  • Utilize EAP chaining
  • Authenticate against Active Directory

From the ISE GUI, perform the following steps:

  1. Navigate to Policy > Authentication.
  2. Insert a new rule above the preconfigured Dot1X rule.
  3. Provide a name for the rule. In this case, we named it CiscoPress SSID.
  4. For the condition, choose RADIUS > Called-Station-ID.
  5. Select Contains.
  6. Type in the SSID Name in the text box. Figure 13-8 shows the condition.
    Figure 13-8

    Figure 13-8. Called-Station-ID Contains CiscoPress

  7. Create a new allowed protocol object that only allows EAP-FAST, as shown in Figure 13-9. Select the drop-down for Allowed Protocols.
    Figure 13-9

    Figure 13-9.Create a New Allowed Protocol

  8. Click the cog in the upper-right corner and choose Create a New Allowed Protocol.
  9. Provide a name. In this case, it was named it EAP-FAST ONLY.
  10. Optionally, provide a description.
  11. Working top-down, ensure that all the check boxes are unchecked until you reach Allow EAP-FAST.
  12. Confirm that Allow EAP-FAST is enabled.
  13. For ease of use, enable EAP-MS-CHAPv2, EAP-GTC, and EAP-TLS for inner methods.
  14. Select Use PACs for faster session re-establishment, and to allow EAP chaining.

    Figure 13-10 shows the EAP-FAST settings for the new Allowed Protocols definition.

    Figure 13-10

    Figure 13-10.Allowed Protocols

  15. For ease of deployment, select Allow Anonymous In-Band PAC Provisioning and Allow Authenticated In-Band PAC Provisioning.
  16. Check the boxes for Server Sends Access-Accept After Authenticated Provisioning and Accept Client Certificate for Provisioning.
  17. Enable Allow Machine Authentication.
  18. Select Enable Stateless Session Resume.
  19. Select Enable EAP chaining, as shown in Figure 13-11.
    Figure 13-11

    Figure 13-11.Allowed Protocols, Continued

  20. Because you are only allowing one protocol, there is no need to set a preferred EAP Protocol.
  21. Click Save.
  22. Select the drop-down for the identity source (currently set for Internal Users), as shown in Figure 13-12.
    Figure 13-12

    Figure 13-12.Selecting the AD Identity Source

  23. Select your Active Directory source. In this case, the name is AD1.
  24. Leave the default options.
  25. Click Done.
  26. Click Save.

    Figure 13-13 shows the completed authentication rule.

    Figure 13-13

    Figure 13-13.Completed Authentication Rule

This completes the creation of the authentication rule. Determining what actions to take for the authentications that passed is handled in the Authorization Policy.

Remote-Access VPN

Very often, authentications for a remote-access VPN connection get routed to an OTP server, like RSAs SecureID. For this example, let’s build a rule for remote-access VPN authentications. This rule will be configured to

  • Only match authentications coming from the VPN device
  • Route that authentication to the OTP server

From the ISE GUI, perform the following steps:

  1. Navigate to Policy > Authentication.
  2. Insert a new rule above the preconfigured Dot1X rule.
  3. Provide a name for the rule. In this case, it was named RA VPN.
  4. For the condition, choose DEVICE > Device Type.
  5. Set the operator to Equals.
  6. Choose the Network Device Group VPN.

    Figure 13-14 shows the selection of the conditions.

    Figure 13-14

    Figure 13-14.Device Type Equals VPN

  7. For this example, just use the allowed protocol of Default Network Access.
  8. For the identity store, the OTP server was selected that was previously configured in Administration > Identity Management > External Identity Sources > RADIUS Token (ATWOTP).
  9. Leave the default options.
  10. Click Done.
  11. Click Save.

    Figure 13-15 shows the completed RA VPN rule.

    Figure 13-15

    Figure 13-15.Completed Authentication Rule

Alternative ID Stores Based on EAP Type

In this modern day of BYOD and mobility, it is common to have multiple user and device types connecting to the same wireless SSID. In scenarios like this, often times, the corporate users with corporate laptops authenticate using EAP-FAST with EAP chaining while BYOD-type devices need to use certificates and EAP-TLS. Anyone authenticating with PEAP is recognized as a non-corporate and non-registered asset and sent to a device registration portal instead of being permitted network access.

For this example, let’s modify the preconfigured Dot1X rule by creating subrules for each EAP type. This rule will be configured to

  • Match wired or wireless 802.1X
  • Route EAP-TLS authentications to a Certificate Authentication Profile (CAP)
  • Route PEAP authentications to an LDAP server
  • Route EAP-FAST to Active Directory
  • Route EAP-MD5 to internal endpoints for host-lookup as a MAB request

From the ISE GUI, perform the following steps:

  1. Navigate to Policy > Authentication.
  2. Edit the preconfigured Dot1X rule.
  3. Create a new allowed protocol object that only allows EAP authentications. Select the drop-down for allowed protocols.
  4. Click the cog in the upper-right corner and choose Create a New Allowed Protocol.
  5. Provide a name. In this case, it is named All EAP Types.
  6. Optionally, provide a description.
  7. Working top-down, ensure all EAP types are enabled, except for LEAP (unless you need LEAP for backward compatibility).
  8. Enable EAP chaining, as done previously in the wireless SSID exercise.
  9. Click Save.
  10. Insert a new subrule above the Default Identity Store subrule and name it EAP-TLS.
  11. For the condition, choose Network Access > EapAuthentication equals EAP-TLS (as shown in Figure 13-16).
    Figure 13-16

    Figure 13-16.Network Access:EapAuthentication Equals EAP-TLS

  12. For the identity source, choose the preconfigured Certificate Authentication Profile (CAP). This was configured at Administration > Identity Management > External Identity Sources > Certificate Authentication Profile.
  13. Insert a new row above the EAP-TLS row to insert EAP-FAST. Place EAP-FAST above EAP-TLS, because EAP-TLS may be used as an inner-method of EAP-FAST.
  14. Choose Network Access > EapTunnel Equals EAP-FAST for the condition.
  15. Select the Active Directory object for the identity source.
  16. Insert a new row above the EAP-TLS row to insert PEAP.
  17. Choose Network Access > EapTunnel Equals PEAP for the condition.
  18. Select the LDAP object for the identity source.
  19. Insert a new row below the EAP-TLS row to insert EAP-MD5.
  20. Choose Network Access > EapAuthentication Equals EAP-MD5 for the condition.
  21. Select internal endpoints for the identity source.
  22. Change the default identity store (bottom row) to be Deny Access.
  23. Click Done.
  24. Click Save.

    Figure 13-17 shows the completed rule and subrules.

    Figure 13-17

    Figure 13-17.Completed Authentication Rule and Sub Rules

This completes the authentication section of this chapter. The next section takes an in-depth look at Authorization Policies and common authorization rules.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020