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soc:2009:oremanj:journal:week6 [2009/07/03 15:58] rwcr |
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| ====== Joshua Oreman: 802.11 wireless development ====== | ====== Joshua Oreman: 802.11 wireless development ====== | ||
| - | ===== Journal Week 5 ===== | + | ===== Journal Week 6 ===== |
| ==== Monday, 29 June ==== | ==== Monday, 29 June ==== | ||
| Line 87: | Line 87: | ||
| ==== Friday, 3 July ==== | ==== Friday, 3 July ==== | ||
| - | WPA2 is working. | + | WPA2 is working! |
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=fc7d95d70fd197319dc4f0138ba2df3705286e91| | ||
| + | [crypto] Make AES context size and algorithm structure externally available]] | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=436b6980765eb7bb5061a8fd301affe9af0f8283| | ||
| + | [crypto] Add AES key-wrap mode (RFC 3394)]] | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=b9025f9a595fd44e86b0957f12db4381de801010| | ||
| + | [wpa] Remove KIE encrypt function, and allow decrypt to return an error]] | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=8f4e89b9e81bc2a3b714d7a49de1efd18c86e904| | ||
| + | [tkip] Make private functions static]] | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=fdaaa4d9df9e43ce825d9b37e11126c9f36a7f31| | ||
| + | [wpa] Avoid recomputing Snonce during handshake + some minor tightening]] | ||
| + | * [[http://git.etherboot.org/?p=people/oremanj/gpxe.git;a=commit;h=be6d51f8d83f42717d580b6df0057886b2f4119f| | ||
| + | [wpa] Add support for CCMP encryption (AES-based, WPA2 default)]] | ||
| + | |||
| + | I was able to connect to a network that uses CCMP for unicast packets and TKIP for broadcast packets, and do DHCP (which uses broadcast) and chainload tomsrtbt (unicast) without any crypto errors. (The unicast/broadcast cipher split is fairly common, because the broadcast cipher has to be supported by every node, while a unicast cipher can be negotiated with each node separately.) | ||
| + | |||
| + | Before that, I discovered that writing a memory-processing loop like this: | ||
| + | for ( i = nblk; i >= 1; i++ ) { | ||
| + | /* ... */ | ||
| + | } | ||
| + | is a surefire road to a hair-pulling two-hour debugging session. Learn from my mistake, and don't write descending loops as ascending loops. :-) | ||
| + | |||
| + | CCMP uses AES in two ways: in key-wrap mode (RFC 3394) to protect the group key in the 4-Way Handshake frames, and in counter mode with CBC-MAC (CCM; RFC 3610) to handle normal data packets. I implemented AES-wrap as a generic crypto function, since it is reasonably simple and does not have many tunable parameters; it doesn't have a ''crypto_algorithm'' structure, but that's just a matter of it being almost uniformly used for bite-sized chunks of data that are generally operated on in one piece. For CCM, I made the implementation private to WPA2 because that allowed me to make WPA2-specific size-saving assumptions about how it would be used. I kept the encryption and MACing code separate from the packet marshalling code, though, so if another use for CCM arises it should be fairly easily genericizable. | ||
| + | |||
| + | This will be my last coding work until July 20. In the meantime I will be preparing for and competing in the [[http://ipho2009.smf.mx/home|2009 International Physics Olympiad]] in Merida, Mexico. Wish me luck! :-) | ||
| + | |||
| + | After I get back: drivers drivers drivers... | ||
