Understanding EAP-FAST and Chaining implementations on AnyConnect NAM and ISE

Introduction

This article explains details regarding EAP-FAST implementations on Cisco AnyConnect Network Access Manager (NAM) and Identity Services Engine (ISE). It further explains how specific features work together and provides typical use cases and examples.

Prerequisites

Requirements

Cisco recommends that you have knowledge of these topics:

• Basic knowledge of EAP framework and EAP-FAST methods
• Basic knowledge of Identity Services Engine (ISE)
• Basic knowledge of AnyConnect NAM and Profile Editor  
• Basic knowledge of Cisco Catalyst configuration for 802.1x services

Components Used

The information in this document is based on these software versions:

• Windows 7 with Cisco AnyConnect Secure Mobility Client, Release 3.1 and 4.0
• Cisco Catalyst 3750X switch with software 15.2.1 and later
• Cisco ISE, Release 1.4

Theory

Phases

EAP-FAST is a flexible EAP method which allows mutual authentication of a supplicant and a server. It is similar to EAP-PEAP, but typically does not require the use of client or even server certificates. One advantage of EAP-FAST is the ability to chain multiple authentications (using multiple inner methods) and bind it cryptographically together (EAP Chaining). Cisco implementations use this for user and machine authentications.

EAP-FAST utilizes Protected Access Credentials (PAC) in order to quickly establish the TLS tunnel (session resume) or to authorize the user/machine (skip inner method for authentication).

There are 3 phases for EAP-FAST:

• phase 0 (PAC provisioning)
• phase 1 (TLS tunnel establishment)
• phase 2 (Authentication)

EAP-FAST supports PAC-less and PAC-based conversation. PAC-based consists of PAC provisioning and PAC-based authentication. PAC provisioning can be based on anonymous or authenticated TLS session.

PAC

PAC is Protected Access Credentials generated by the server and provided to client. It consists of:

• PAC key (random secret value, used to derive TLS master and session keys)
• PAC opaque (PAC key + user identity - all encrypted by EAP-FAST server master key)
• PAC info (server identity, TTL timers)

The server issuing the PAC will encrypt the PAC key and identity using the EAP-FAST server master key (that is PAC opaque) and sends the whole PAC to the client. It does not keep/store any other information (except master key which is the same for all PACs) .

Once the PAC opaque is received, it is decrypted using the EAP-FAST server master key and validated. The PAC key is used to derive the TLS master and session keys for an abbreviated TLS tunnel.

New EAP-FAST server master keys are generated when the previous master key expires.   In some cases, a master key can be revoked.

There are a few types of PAC's being used currently:

• Tunnel PAC: used for TLS tunnel establishment (without the need of client or server certificate). Sent in TLS Client Hello
• Machine PAC: used for TLS tunnel establishment and immediate machine authorization. Sent in TLS Client Hello
• User Authorization PAC: used for immediate user authentication (skip inner method) if allowed by server. Sent inside TLS tunnel using TLV.
• Machine Authorization PAC: used for immediate machine authentication (skip inner method) if allowed by server. Sent inside TLS tunnel using TLV.
• Trustsec PAC: used for authorization when performing environmental or policy refresh.

All of those PAC's are usually delivered automatically in phase 0. Some of the PAC's (Tunnel, Machine, Trustsec) can be also delivered manually.

When PACs are generated

• Tunnel PAC: provisioned after a successful authentication (inner method) if not used previously.
• Authorization PAC: provisioned after successful authentication (inner method) if not used previously.
• Machine PAC: provisioned after successful machine authentication (inner method) if not used previously and  when an Authorization PAC is not used. It will be proviosioned when the Tunnel PAC expires; however, not when the Authorization PAC expires. It will be provisioned when EAP-Chaining is enabled or disabled.

Note:

Each PAC provisioning requires successful authentication except of the following use case: authorized user asks for the Machine PAC for a machine that doesn't have an AD account.

The following table summarizes provisioning and proactive update functionality:

PAC Type	Tunnel v1/v1a/CTS	Machine	Authorization
Provide PAC on request on provisioning	yes	only on authenticated provisioning	only on authenticated provisioning and if Tunnel PAC is requested also
Provide PAC on request on authentication	yes	yes	only if it was not used in this authentication
Proactive update	yes	no	no
When falling back to PAC provisioning after failed PAC-based  authentication (e.g. when PAC is expired)	reject and don’t provide the new one	reject and don’t provide the new one	reject and don’t provide the new one
Support ACS 4.x PACs	for Tunnel PAC v1/v1a	yes	no

EAP-FAST Server Master Key ACS 4.x vs ACS 5x and ISE

There is a slight difference in Master key handling when comparing ACS 4.x and ISE

Feature	ACS 4.1.2	ACS 5.x / ISE
Master Key	Master key has TTL, can be active, retired or expired	Master key is automatically generated from seed at every configured period of time. Specific Master Key is always accessible and then never expired
PAC Refresh	PAC update is sent by server when PAC is expired, unless Master Key used for PAC encryption is expired	PAC update is sent by server after first successful authentication that is performed in specific configurable period of time before PAC expiration moment.

In other words, ISE will keep all old master keys and generate a new one by default once per week. As the Master Key cannot expire, only the PAC TTL will be validated.

The ISE Master Key generation period is configured from Administration -> Settings -> Protocol -> EAP-FAST -> EAP-FAST Settings.

Session Resume

This is an important component allowing for Tunnel PAC usage. It allows for TLS tunnel renegotiation without usage of certificates.

There are two session resume types for EAP-FAST: Server state based and stateless (PAC based).

Server State

Standard TLS based method is based on the TLS SessionID cached on the server. The client sending the TLS Client Hello attaches the SessionID in order to resume the session. The session is only used for PAC provisioning when using an anonymous TLS tunnel:

Stateless (PAC based)

User/Machine Authorization PAC is used to store the previous authentication and authorization states for the peer.

Client side resume is based on RFC 4507. The server doesn't need to cache any data; instead the client attaches the PAC in the TLS Client Hello SessionTicket extension. In turn, the PAC is validated by the server.  Example based on Tunnel PAC delivered to the server:

AnyConnect NAM implementation

It's enabled on client side (AnyConnect NAM) via Fast Reconnect - but it's used to control only authorization PAC usage.

With the setting disabled, NAM will still use the tunnel PAC to build the TLS tunnel (no certificates needed). However, this will not use authorization PACs in order to perform immediate user and machine authorization. As a result, phase 2 with the inner method will be always required.

ISE has an option to enable Stateless Session Resume. And as on NAM it's just for Authorization PAC. Tunnel PAC usage is controlled with options "Use PACs".

NAM will try to use PAC's if the option is enabled. If "Don't Use PACs" is configured in ISE and ISE receives a Tunnel PAC in the TLS extension the following error will be reported and an EAP Failure is returned:

insert here

In ISE,  it's also necessary to enable session resume based on TLS SessionID (from Global EAP-FAST settings). It's disabled by default:

Please keep in mind that only one type of session resume can be used. SessionID based is used only for PAC-less deployments, RFC 4507 based is used only for PAC deployments.

PAC provisioning (phase 0)

PACs can be automatically provisioned in phase0. Phase 0 consists of:

• TLS tunnel establishment
• Authentication (inner method)

PACs are delivered after a successful authentication inside the TLS tunnel via PAC TLV (and PAC TLV Acknowledgement)

Anonymous TLS tunnel

For deployments without a PKI infrastructure, it's possible to use an anonymous TLS tunnel. The anonymous TLS tunnel will be built using the Diffie Hellman cipher suite - without the need of a server or client certificate. This approach is prone to Man in the Middle attacks (impersonation).

To use this option, NAM requires the following configured option:

"If using PACs allow for unauthenticated PAC provisioning" (that makes sense only for password-based inner method because without PKI infrastructure it's not possible to use certificate-based inner method).

Also, ISE will need the following configured under the Authentication Allowed Protocols:

"Allow Anonymous In-band PAC Provisioning"

Anonymous in-band PAC provisioning is being used in TrustSec NDAC deployments (EAP-FAST session negotiated between network devices).

Authenticated TLS tunnel

This is the most secure and recommended option. The TLS tunnel is built based on the server certificate which is validated by the supplicant. This requires a PKI infrastructure on the server side only, which is required for ISE (on NAM it's possible to disable option "Validate Server Identity".

For ISE there are two additional options:

Normally, after PAC provisioning, an Access-Reject should be sent forcing the supplicant to reauthenticate using PACs. But since PACs were delivered in the TLS tunnel with authentication, it's possible to shorten the whole process and return Access-Accept immediately after PAC provisioning. 

The second option builds the TLS tunnel based on client certificate (this requires PKI deployment on the endpoints). This allows the TLS tunnel to be built with mutual authentication, which skips the inner method and goes directly to the PAC provisioning phase. It's important to be careful here - sometimes the supplicant will present a certificate which is not trusted by ISE (intended for other purposes) and the session will fail.

EAP-Chaining

Allows user and machine authentication within one Radius/EAP session. Multiple EAP methods can be chained together. After the first authentication (typically machine) has finished successfully, the server will send an Intermediate-Result TLV (inside TLS tunnel) indicating success. That TLV must be accompanied by a Crypto-Binding TLV Request. Cryptobinding is used to prove that both the server and peer  have participated in the specific sequence of authentications. The Cryptobinding process uses the keying material from phase 1 and phase 2. Additionally, one more TLV is attached: EAP-Payload - this is initiating  the new session (typically for the user). Once the radius server (ISE) receives the Crypto-Binding TLV Response and validates it, the following will be shown in the log and the next EAP method will be tried (typically for user authentication):

12126   EAP-FAST cryptobinding verification passed

If cryptobinding validation fails, the whole EAP session fails. If one of the authentications within failed then it's still fine - as a result, ISE allows an administrator to configure multiple chaining results based on Authorization Condition NetworkAccess:EapChainingResult:

EAP-Chaining is enabled on NAM automatically when EAP-FAST user and machine authentication is enabled.

EAP-Chaining must be configured in ISE.

Where PAC files are stored

By default, Tunnel and Machine PACs are stored in C:\ProgramData\Cisco\Cisco AnyConnect Secure Mobility Client\Network Access Manager\system\internalConfiguration.xml in sections <credential>. Those are stored in encrypted form.

Authorization PACs are stored only in memory and are removed after reboot or NAM service restart.

A service restart is required to remove the Tunnel or Machine PAC.

AnyConnect NAM 3.1 vs 4.0

AnyConnect 3.x NAM profile editor allowed the administrator to configure PACs manually. This feature has been removed from AnyConnect 4.x NAM profile editor.

The decision to remove that functionality is based on CSCuf31422 and CSCua13140 .

Examples

Network Diagram

All the examples were tested using the following network topology. The same applies also when using wireless.

EAP-Fast without EAP chaining with user and machine PAC

By default, EAP_chaining is disabled on ISE. However, all other options are enabled including Machine and Authorization PACs. The supplicant already has a valid Machine and Tunnel PAC. In this flow, there will be two separate authentications - one for the machine and one for the user - with separate logs on ISE. The main steps as logged by ISE. First authentication (machine):

• Supplicant sends TLS Client Hello with Machine PAC.
• Server validates the Machine PAC and builds the TLS tunnel (no certificates used).
• Server validates the Machine PAC and performs the account lookup in Active Directory and skips the inner method.

12102 Extracted EAP-Response containing EAP-FAST challenge-response and accepting EAP-FAST as negotiated 
12800 Extracted first TLS record; TLS handshake started 
12174 Received Machine PAC 
12805 Extracted TLS ClientHello message 
12806 Prepared TLS ServerHello message 
12801 Prepared TLS ChangeCipherSpec message 

12816 TLS handshake succeeded 
12132 EAP-FAST built PAC-based tunnel for purpose of authentication 

24351 Account validation succeeded 
24420 User's Attributes retrieval from Active Directory succeeded - example.com 
22037 Authentication Passed 
12124 EAP-FAST inner method skipped 

11503 Prepared EAP-Success 
11002 Returned RADIUS Access-Accept 

The second authentication (user):

• Supplicant sends the TLS Client Hello with Tunnel PAC.
• Server validates the PAC and builds the TLS tunnel (no certificates used).
• As supplicant does not have any Authorization PAC, the inner method (EAP-MSCHAP) is used for authentication.

12102 Extracted EAP-Response containing EAP-FAST challenge-response and accepting EAP-FAST as negotiated 
12800 Extracted first TLS record; TLS handshake started 
12175 Received Tunnel PAC 
12805 Extracted TLS ClientHello message 
12806 Prepared TLS ServerHello message 
12801 Prepared TLS ChangeCipherSpec message 

12816 TLS handshake succeeded 
12132 EAP-FAST built PAC-based tunnel for purpose of authentication 
12125 EAP-FAST inner method started 
11806 Prepared EAP-Request for inner method proposing EAP-MSCHAP with challenge 

24402 User authentication against Active Directory succeeded - example.com 
22037 Authentication Passed 

11503 Prepared EAP-Success 
11002 Returned RADIUS Access-Accept

In the "Other Attributes" section of the detailed report in ISE, the following is noted for both user and machine authentications:

EapChainingResult: No chaining

EAP-Fast with EAP chaining with PAC Fast Reconnect

In this flow, the supplicant already has a valid Tunnel PAC along with the User and Machine Authorization PACs:

• Supplicant sends the TLS Client Hello with Tunnel PAC.
• Server validates the PAC and builds the TLS tunnel (no certificates used).
• ISE starts EAP Chaining, supplicant attaches Authorization PACs for user and Machine using TLV inside the TLS tunnel.
• ISE validates the Authorization PACs (no inner method needed), verifies that accounts exist in Active Directory (no additional authentication), returns success.

12102   Extracted EAP-Response containing EAP-FAST challenge-response and accepting EAP-FAST as negotiated
12800   Extracted first TLS record; TLS handshake started
12175   Received Tunnel PAC
12805   Extracted TLS ClientHello message
12806   Prepared TLS ServerHello message
12801   Prepared TLS ChangeCipherSpec message

12816   TLS handshake succeeded
12132   EAP-FAST built PAC-based tunnel for purpose of authentication
12209   Starting EAP chaining
12210   Received User Authorization PAC
12211   Received Machine Authorization PAC

24420   User's Attributes retrieval from Active Directory succeeded - example.com
22037   Authentication Passed

24439   Machine Attributes retrieval from Active Directory succeeded - example.com
22037   Authentication Passed

11503   Prepared EAP-Success        
11002   Returned RADIUS Access-Accept 

In the "Other Attributes" section of the detailed report in ISE, the following is noted:

EapChainingResult: EAP Chaining

Additionally, both user and machine credentials are included in the same log as seen below:

Username: cisco,host/mgarcarz-PC

EAP-Fast with EAP chaining without PAC

In this flow, NAM is configured to not use a PAC, ISE is also configured to not use PAC (but with EAP Chaining)

• Supplicant sends TLS Client Hello without Tunnel PAC.
• Server responds with the TLS Certificate and Certificate Request payloads.
• Supplicant must trust server certificate, will not send any client certificate (certificate payload is zero), TLS tunnel is built.
• ISE send a TLV request for the client certificate inside the TLS tunnel, but supplicant does not (it's not necessary to have it in order to continue).
• Starts EAP Chaining for user, using inner method with MSCHAPv2 authentication.
• Continues with machine authentication, using inner method with MSCHAPv2 authentication.
• No PACs are being provisioned.

12102     Extracted EAP-Response containing EAP-FAST challenge-response and accepting EAP-FAST as negotiated
12800     Extracted first TLS record; TLS handshake started
12805     Extracted TLS ClientHello message
12806     Prepared TLS ServerHello message
12807     Prepared TLS Certificate message
12809     Prepared TLS CertificateRequest message
12811     Extracted TLS Certificate message containing client certificate
12812     Extracted TLS ClientKeyExchange message

12816     TLS handshake succeeded
12207     Client certificate was requested but not received during tunnel establishment. Will renegotiate and request client certificate inside the tunnel.
12226     Started renegotiated TLS handshake

12104     Extracted EAP-Response containing EAP-FAST challenge-response
12811     Extracted TLS Certificate message containing client certificate
12812     Extracted TLS ClientKeyExchange message
12804     Extracted TLS Finished message
12801     Prepared TLS ChangeCipherSpec message
12802     Prepared TLS Finished message
12226     Started renegotiated TLS handshake
12205     Client certificate was requested but not received inside the tunnel. Will continue with inner method.
12176     EAP-FAST PAC-less full handshake finished successfully

12209     Starting EAP chaining
12218     Selected identity type 'User'

11806     Prepared EAP-Request for inner method proposing EAP-MSCHAP with challenge

24402     User authentication against Active Directory succeeded - example.com
22037     Authentication Passed

12219     Selected identity type 'Machine'

11806     Prepared EAP-Request for inner method proposing EAP-MSCHAP with challenge

24470     Machine authentication against Active Directory is successful - example.com
22037     Authentication Passed

11503     Prepared EAP-Success
11002     Returned RADIUS Access-Accept 

EAP-Fast with EAP chaining authorization PAC expiration

In this flow, the Supplicant has a valid Tunnel PAC but has expired Authorization PACs:

• Supplicant sends the TLS Client Hello with Tunnel PAC.
• Server validates the PAC and builds the TLS tunnel (no certificates used).
• ISE starts EAP Chaining, supplicant attaches Authorization PACs for User and Machine using TLV inside the TLS tunnel.
• As the PACs are expired, the inner method for both user and machine is started (EAP-MSCHAP).
• Once both authentications are successful, both user and machine Authorization PACs are provisioned.

12102   Extracted EAP-Response containing EAP-FAST challenge-response and accepting EAP-FAST as negotiated
12800   Extracted first TLS record; TLS handshake started
12175   Received Tunnel PAC
12805   Extracted TLS ClientHello message
12806   Prepared TLS ServerHello message
12801   Prepared TLS ChangeCipherSpec message

12816   TLS handshake succeeded
12132   EAP-FAST built PAC-based tunnel for purpose of authentication
12209   Starting EAP chaining
12227   User Authorization PAC has expired - will run inner method
12228   Machine Authorization PAC has expired - will run inner method
12218   Selected identity type 'User'

11806   Prepared EAP-Request for inner method proposing EAP-MSCHAP with challenge

24402   User authentication against Active Directory succeeded - example.com
22037   Authentication Passed

12219   Selected identity type 'Machine'

24470   Machine authentication against Active Directory is successful - example.com
22037   Authentication Passed

12171   Successfully finished EAP-FAST user authorization PAC provisioning/update
12179   Successfully finished EAP-FAST machine authorization PAC provisioning/update

11503   Prepared EAP-Success
11002   Returned RADIUS Access-Accept 

EAP-Fast with EAP chaining tunnel PAC expired

In this flow when no valid tunnel PAC exists, full TLS negotiation with inner phase occurs.

• Supplicant sends the TLS Client Hello without Tunnel PAC.
• Server responds with the TLS Certificate and Certificate Request payloads.
• Supplicant must trust server certificate, will not send client certificate (certificate payload is zero), TLS tunnel built.
• ISE sends TLV request for the client certificate inside the TLS tunnel, but supplicant does not (it's not necessary to have it in order to continue).
• Starts EAP Chaining for user, using inner method with MSCHAPv2 authentication.
• Continues with machine authentication, using inner method with MSCHAPv2 authentication.
• Successfully provisioned all PACs (enabled in ISE config).

12102   Extracted EAP-Response containing EAP-FAST challenge-response and accepting EAP-FAST as negotiated
12800   Extracted first TLS record; TLS handshake started
12805   Extracted TLS ClientHello message
12806   Prepared TLS ServerHello message
12807   Prepared TLS Certificate message
12809   Prepared TLS CertificateRequest message
12105   Prepared EAP-Request with another EAP-FAST challenge
11006   Returned RADIUS Access-Challenge
11001   Received RADIUS Access-Request

12816   TLS handshake succeeded
12207   Client certificate was requested but not received during tunnel establishment. Will renegotiate and request client certificate inside the tunnel.
12226   Started renegotiated TLS handshake

12104   Extracted EAP-Response containing EAP-FAST challenge-response
12811   Extracted TLS Certificate message containing client certificate
12812   Extracted TLS ClientKeyExchange message
12804   Extracted TLS Finished message
12801   Prepared TLS ChangeCipherSpec message
12802   Prepared TLS Finished message
12226   Started renegotiated TLS handshake
12205   Client certificate was requested but not received inside the tunnel. Will continue with inner method.
12149   EAP-FAST built authenticated tunnel for purpose of PAC provisioning
12105   Prepared EAP-Request with another EAP-FAST challenge
11006   Returned RADIUS Access-Challenge
11001   Received RADIUS Access-Request
11018   RADIUS is re-using an existing session
12104   Extracted EAP-Response containing EAP-FAST challenge-response
12209   Starting EAP chaining
12218   Selected identity type 'User'
11806   Prepared EAP-Request for inner method proposing EAP-MSCHAP with challenge    

24402   User authentication against Active Directory succeeded - example.com
22037   Authentication Passed

12126   EAP-FAST cryptobinding verification passed
12200   Approved EAP-FAST client Tunnel PAC request
12202   Approved EAP-FAST client Authorization PAC request
12219   Selected identity type 'Machine'

11806   Prepared EAP-Request for inner method proposing EAP-MSCHAP with challenge

24470   Machine authentication against Active Directory is successful - example.com
22037   Authentication Passed

12169   Successfully finished EAP-FAST tunnel PAC provisioning/update
12171   Successfully finished EAP-FAST user authorization PAC provisioning/update
12170   Successfully finished EAP-FAST machine PAC provisioning/update
12179   Successfully finished EAP-FAST machine authorization PAC provisioning/update

11503   Prepared EAP-Success
11002   Returned RADIUS Access-Accept 

EAP-Fast with EAP chaining and anonymous TLS tunnel PAC provisioning

In this flow, ISE and NAM anonymous TLS tunnel is configured for PAC provisioning (ISE authenticated TLS tunnel for PAC provisioning is disabled) PAC provisioning request looks like:

• Supplicant sends TLS Client Hello without multiple ciphersuites.
• Server responds with the TLS Server Hello and TLS anonymous Diffie Hellman ciphers (for example TLS_DH_anon_WITH_AES_128_CBC_SHA).
• Supplicant accepts it and the anonymous TLS tunnel is built (no certificates exchanged).
• Starts EAP Chaining for user, using inner method with MSCHAPv2 authentication.
• Continues with machine authentication, using inner method with MSCHAPv2 authentication.
• Since the anonymous TLS tunnel is being built Authorization PACs are not allowed.
• Radius Reject is returned to force supplicant to reauthenticate (using provisioned PAC).

12102     Extracted EAP-Response containing EAP-FAST challenge-response and accepting EAP-FAST as negotiated      
12800     Extracted first TLS record; TLS handshake started
12805     Extracted TLS ClientHello message
12806     Prepared TLS ServerHello message
12808     Prepared TLS ServerKeyExchange message
12810     Prepared TLS ServerDone message

12812     Extracted TLS ClientKeyExchange message
12804     Extracted TLS Finished message
12801     Prepared TLS ChangeCipherSpec message
12802     Prepared TLS Finished message
12816     TLS handshake succeeded
12131     EAP-FAST built anonymous tunnel for purpose of PAC provisioning

12209     Starting EAP chaining
12218     Selected identity type 'User'

11806     Prepared EAP-Request for inner method proposing EAP-MSCHAP with challenge

24402     User authentication against Active Directory succeeded - example.com
22037     Authentication Passed

12162     Cannot provision Authorization PAC on anonymous provisioning. Authorization PAC can be provisioned only on authenticated provisioning
12200     Approved EAP-FAST client Tunnel PAC request
12219     Selected identity type 'Machine'

24470     Machine authentication against Active Directory is successful - example.com
22037     Authentication Passed

12162     Cannot provision Authorization PAC on anonymous provisioning. Authorization PAC can be provisioned only on authenticated provisioning      
12169     Successfully finished EAP-FAST tunnel PAC provisioning/update
12170     Successfully finished EAP-FAST machine PAC provisioning/update

11504     Prepared EAP-Failure
11003     Returned RADIUS Access-Reject 

Wireshark packet captures for anonymous TLS tunnel negotiation:

EAP-Fast with EAP chaining user authentication only

In this flow, AnyConnect NAM with EAP-FAST and User (EAP-TLS) and Machine authentication (EAP-TLS) is configured. The Windows PC is booted but user credentials are not provided. Switch initiates 802.1x session, NAM must respond however, user credentials are not provided, (no access to user store and certificate yet) therefore. user authentication will fail while the machine will be successful - ISE authz condition "Network Access:EapChainingResult EQUALS User failed and machine succeeded" is satisfied. Later, the user logs in and another authentication will start, both user and machine will succeed.

• Supplicant sends TLS Client Hello with Machine PAC.
• Server responds with the TLS Change Cipher Spec - TLS tunnel is immediately build based on that PAC.
• ISE initiates EAP Chaining and asking for user identity.
• Supplicant provides the machine identity instead (user not yet ready), finishes EAP-TLS inner method.
• ISE asks for user identity again, supplicant can not provide it.
• ISE sends TLV with intermediate result = failure (for user authentication).
• ISE returns the final EAP success message, ISE condition Network Access:EapChainingResult EQUALS User failed and machine succeeded is satisfied.

12102   Extracted EAP-Response containing EAP-FAST challenge-response and accepting EAP-FAST as negotiated
12800   Extracted first TLS record; TLS handshake started
12174   Received Machine PAC

12805   Extracted TLS ClientHello message
12806   Prepared TLS ServerHello message
12801   Prepared TLS ChangeCipherSpec message
12802   Prepared TLS Finished message

12816   TLS handshake succeeded
12132   EAP-FAST built PAC-based tunnel for purpose of authentication

12209   Starting EAP chaining
12218   Selected identity type 'User'

12213   Identity type provided by client is not equal to requested type
12215   Client suggested 'Machine' identity type instead

12104   Extracted EAP-Response containing EAP-FAST challenge-response
12523   Extracted EAP-Response/NAK for inner method requesting to use EAP-TLS instead

12805   Extracted TLS ClientHello message
12806   Prepared TLS ServerHello message
12807   Prepared TLS Certificate message
12809   Prepared TLS CertificateRequest message

12816   TLS handshake succeeded
12509   EAP-TLS full handshake finished successfully

22070   Identity name is taken from certificate attribute
15013   Selected Identity Source - Test-AD
24323   Identity resolution detected single matching account
22037   Authentication Passed

12202   Approved EAP-FAST client Authorization PAC request
12218   Selected identity type 'User'
12213   Identity type provided by client is not equal to requested type
12216   Identity type provided by client was already used for authentication
12967   Sent EAP Intermediate Result TLV indicating failure

12179   Successfully finished EAP-FAST machine authorization PAC provisioning/update
12106   EAP-FAST authentication phase finished successfully
11503   Prepared EAP-Success
11002   Returned RADIUS Access-Accept

EAP-Fast with EAP chaining and inconsistent anonymous TLS tunnel settings

In this flow, ISE is configured for PAC provisioning only via anonymous TLS tunnel, but NAM is using an authenticated TLS tunnel, the following will be logged by ISE:

12102   Extracted EAP-Response containing EAP-FAST challenge-response and accepting EAP-FAST as negotiated
12800   Extracted first TLS record; TLS handshake started
12805   Extracted TLS ClientHello message
12814   Prepared TLS Alert message
12817   TLS handshake failed
12121   Client didn't provide suitable ciphers for anonymous PAC-provisioning

11504   Prepared EAP-Failure
11003   Returned RADIUS Access-Reject 

This occurs when NAM is trying to build an authenticated TLS tunnel with it's speciphic TLS ciphers - and those are not accepted by ISE which is configured for anonymous TLS tunnel (accepting DH ciphers only)

Troubleshoot

ISE

For detailed logs, Runtime-AAA debugs should be enabled on the corresponding PSN node. Below are a few example logs from prrt-server.log:

Machine PAC generation:

DEBUG,0x7fd5332fe700,cntx=0001162745,sesn=mgarcarz-ise14/223983918/29245,CPMSessionID=0A3E946D00000FE5131F9D26,CallingStationID=00-50-B6-11-ED-31,FramedIPAddress=10.0.13.127,Using IID from PAC request for machine,EapFastTlv.cpp:1234

DEBUG,0x7fd5332fe700,cntx=0001162745,sesn=mgarcarz-ise14/223983918/29245,CPMSessionID=0A3E946D00000FE5131F9D26,CallingStationID=00-50-B6-11-ED-31,FramedIPAddress=10.0.13.127,Adding PAC of type=Machine Authorization,EapFastProtocol.cpp:3610

DEBUG,0x7fd5332fe700,cntx=0001162745,sesn=mgarcarz-ise14/223983918/29245,CPMSessionID=0A3E946D00000FE5131F9D26,CallingStationID=00-50-B6-11-ED-31,FramedIPAddress=10.0.13.127,Eap-Fast: Generating Pac, Issued PAC type=Machine Authorization with expiration time: Fri Jul  3 10:38:30 2015

PAC request approval:

INFO ,0x7fd5330fc700,cntx=0001162745,sesn=mgarcarz-ise14/223983918/29245,CPMSessionID=0A3E946D00000FE5131F9D26,user=host/mgarcarz-pc,CallingStationID=00-50-B6-11-ED-31,FramedIPAddress=10.0.13.127,Eap-Fast: client PAC request approved for PAC type - Requested PAC type=Machine,EapFastProtocol.cpp:955

INFO ,0x7fd5330fc700,cntx=0001162745,sesn=mgarcarz-ise14/223983918/29245,CPMSessionID=0A3E946D00000FE5131F9D26,user=host/mgarcarz-pc,CallingStationID=00-50-B6-11-ED-31,FramedIPAddress=10.0.13.127,Eap-Fast: client PAC request approved for PAC type - Requested PAC type=Machine Authorization,EapFastProtocol.cpp:955

PAC validation:

DEBUG,0x7fd5330fc700,cntx=0001162499,sesn=mgarcarz-ise14/223983918/29243,CPMSessionID=0A3E946D00000FE5131F9D26,user=anonymous,CallingStationID=00-50-B6-11-ED-31,FramedIPAddress=10.0.13.127,Authorization PAC is valid,EapFastProtocol.cpp:3403

Eap,2015-07-03 09:34:39,208,DEBUG,0x7fd5330fc700,cntx=0001162499,sesn=mgarcarz-ise14/223983918/29243,CPMSessionID=0A3E946D00000FE5131F9D26,user=anonymous,CallingStationID=00-50-B6-11-ED-31,FramedIPAddress=10.0.13.127,Authorization PAC accepted,EapFastProtocol.cpp:3430

Example of successful summary for PAC generation:

DEBUG,0x7fd5331fd700,cntx=0001162749,sesn=mgarcarz-ise14/223983918/29245,CPMSessionID=0A3E946D00000FE5131F9D26,user=cisco,CallingStationID=00-50-B6-11-ED-31,FramedIPAddress=10.0.13.127,Conversation summary: Provisioning. Authenticated. Inner method succeeded. Inner method succeeded. Generated PAC of type Tunnel V1A. Generated PAC of type User Authorization. Generated PAC of type Machine. Generated PAC of type Machine Authorization.  Success

Example of successful summary for PAC validation:

DEBUG,0x7fd5330fc700,cntx=0001162503,sesn=mgarcarz-ise14/223983918/29243,CPMSessionID=0A3E946D00000FE5131F9D26,user=host/mgarcarz-pc,CallingStationID=00-50-B6-11-ED-31,FramedIPAddress=10.0.13.127,Conversation summary: Authentication. PAC type Tunnel V1A. PAC is valid.Skip inner method. Skip inner method.  Success

AnyConnect NAM

DART logs from NAM provide the following details:

Example for non EAP-Chaining session, Machine authentication without fast reconnect:

EAP: Identity requested
Auth[eap-fast-pac:machine-auth]: Performing full authentication
Auth[eap-fast-pac:machine-auth]: Disabling fast reauthentication

Example of Authorization PAC lookup (machine authentication for non EAP-Chaining session):

Looking for matching pac with iid: host/ADMIN-PC2
Requested machine pac was sen

All states of inner method (for MSCHAP) can be verified from the logs below:

 EAP (0) EAP-MSCHAP-V2: State: 0 (eap_auth_mschapv2_c.c 731
 EAP (0) EAP-MSCHAP-V2: State: 2 (eap_auth_mschapv2_c.c 731
 EAP (0) EAP-MSCHAP-V2: State: 1 (eap_auth_mschapv2_c.c 731
 EAP (0) EAP-MSCHAP-V2: State: 4 (eap_auth_mschapv2_c.c 73

NAM allows the configuration of the extended logging feature which will capture all EAP packets and save them in pcap file. This is especially helpful for Start Before Logon functionality (EAP packets are captured even for authentications which occur before user logon). For feature activation ask your TAC engineer.

References

• Cisco AnyConnect Secure Mobility Client Administrator Guide, Release 4.0 EAP-FAST configuration
• Cisco Identity Services Engine Administrator Guide, Release 1.4 EAP-FAST recommendations
• Cisco Identity Services Engine Design Guides
• Deploying EAP Chaining with AnyConnect NAM and Cisco ISE
• Technical Support & Documentation - Cisco Systems