problem with 4-way handshake

Chao Li li.evan.chao at gmail.com
Mon Feb 27 01:17:07 EST 2012


Greetings,

I'm porting hostapd to my project. I have made WPA/WPA2-PSK worked, as I
was thinking my work was about to well done, I encountered a weird problem.

When I use EAP-PEAP mode, radius phase message exchange has succeeded, at
then PMK should have been generated, it starts to 4-way handshake.

In my first test, I used my MacBook Pro as STA, and the whole process well
done.

Then I used my Nexus S Android phone, 4-way handshake could finish, because
STA didn't send 2/4 msg to authenticator.

Next I used my IBM T60 notebook with WinXp, 4-way could also succeed.

At last I tried iPad with iOS5, same as the Android phone.

At failure case, after hostapd send 1/4 msg to STA, instead of respond with
2/4 msg, STA send a Start msg to hostapd, log of hostapd is as below:

EAP: EAP entering state SUCCESS2
IEEE 802.1X: 00:1f:3b:3b:9e:19 BE_AUTH entering state SUCCESS
eth0: STA 00:1f:3b:3b:9e:19 IEEE 802.1X: Sending EAP Packet (identifier 113)
TX EAPOL - hexdump(len=22): 00 1f 3b 3b 9e 19 04 7d 7b 0c f6 a7 88 8e 02 00
00 04 03 71 00 04
IEEE 802.1X: 00:1f:3b:3b:9e:19 BE_AUTH entering state IDLE
WPA: 00:1f:3b:3b:9e:19 WPA_PTK entering state INITPMK
WPA: PMK from EAPOL state machine (len=64)
PMK - hexdump(len=32): a4 d5 96 f8 98 b5 dc f2 c3 2b c3 78 c8 0e 29 75 2b
5d 93 bf 5d 2a 15 09 c0 5d f0 5e 06 80 81 92
WPA: 00:1f:3b:3b:9e:19 WPA_PTK entering state PTKSTART
*eth0: STA 00:1f:3b:3b:9e:19 WPA: sending 1/4 msg of 4-Way Handshake*
WPA: Send EAPOL(version=2 secure=0 mic=0 ack=1 install=0 pairwise=8
kde_len=22 keyidx=0 encr=0)
######## called in __wpa_send_eapol
TX EAPOL - hexdump(len=135): 00 1f 3b 3b 9e 19 04 7d 7b 0c f6 a7 88 8e 02
03 00 75 02 00 8a 00 10 00 00 00 00 00 00 00 01 55 b3 30 87 69 53 f6 03 cd
4e f9 3a 5f 6c 02 2f 97 6c ae 9b e9 0b b6 3e 59 4e 72 54 6d 82 00 90 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 16 dd 14
00 0f ac 04 49 51 72 da 1a 5b 4b b8 5b cd 80 94 26 c3 44 ea
*IEEE 802.1X: 46 bytes from 00:1f:3b:3b:9e:19*
*   IEEE 802.1X: version=1 type=1 length=0*
*   ignoring 42 extra octets after IEEE 802.1X packet*
*eth0: STA 00:1f:3b:3b:9e:19 IEEE 802.1X: received EAPOL-Start from STA*
eth0: STA 00:1f:3b:3b:9e:19 WPA: event 5 notification
WPA: 00:1f:3b:3b:9e:19 WPA_PTK entering state AUTHENTICATION2

I have wiress frame captures by OmniPeek for both success and failure
cases. I compared EAP frames, I couldn't find significant difference.
Anyone idea on how to analysis/debug the problem would be
greatly appreciated! Thanks in advance!

Evan
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