EAP-TLS problems with Cisco AP541N and Server 2008 NPS

Question

Hi,
I want to use EAP-TLS with my shiny new certificates issued by my new Windows CA, and what happens? Nothing works.
I don't have a clue what I should do. I try to establish a EAP-TLS connection using my Windows CE mobile device, but my cisco AP541N logs this:
Oct 18 15:42:58
info
hostapd
wlan0: STA 00:17:23:xx:xx:xx IEEE 802.1X: Supplicant used different EAP type: 3 (Nak)
Oct 18 15:42:58
warn
hostapd
wlan0: STA 00:17:23:xx:xx:xx IEEE 802.1X: authentication failed - identity 'XXXXXX' EAP type: 13 (TLS)
Oct 18 15:42:58
info
hostapd
The wireless client with MAC address 00:17:23:xx:xx:xx had an authentication failure.
NPS logs this:
Name der Verbindungsanforderungsrichtlinie: Sichere Drahtlosverbindungen 2
Netzwerkrichtlinienname: XXXXXX
Authentifizierungsanbieter: Windows
Authentifizierungsserver: XXXXX
Authentifizierungstyp: EAP
EAP-Typ: -
Kontositzungs-ID: -
Protokollierungsergebnisse: Die Kontoinformationen wurden in die lokale Protokolldatei geschrieben.
Ursachencode: 22
Ursache: Der Client konnte nicht authentifiziert werden, da der angegebene EAP (Extensible Authentication-Protokoll)-Typ vom Server nicht verarbeitet werden kann.
I'm sorry it's german, but the gist is: The server can't process the authentication with the specified EAP type, which should be EAP-TLS.
I think the NAK answer in my cisco AP logs is the problem. Well, not the problem, since it is the standard procedure in the EAP request / challenge, I think, but somebody messes up with it.
Did anybody encounter something like this before? Or just knows what to do?
Thanks in advance
Lenni

Answer 1

Joe:
Having NPS, you have the options to configure PEAP-MSCHAPv2 or EAP-TLS.
EAP-TLS: mandates a certificate on the server as well as a certificate on every single machine for authentication purposes.
PEAP-MSCHAPv2: mandates a certificate on the server only. Users connecting to the wireless network must trust the certificate (or, user devices can be configured to escape this trust and connect even if the server cert is not trusted).
for PEAP-MSCHAPv2, Your options are:
- Buy a certificate for the server from a trusted party (Verisign for example [which was bought later by Symantec]). This way all devices will - by default - trust the server's cert.
- Install local CA. Install a cert on the server and then push the root CA cert for your CA to all client device so they trust this issuer.
- If both up options are not valid for you, what you can do is to configure every single client to ignore the untrusted cert and proceed with the connectoin. (This is a security concern though. not recommended unless really needed).
You must get a cert on the server and all clients must trust that certificate's issuer. Otherwise you'll not be able to user PEAP.
HTH
Amjad
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