Re: [ipxe-devel] [ipxe/ipxe] successful wpa handshake (memcmp polarity) (#103)

[Michael Brown]

Closed #103.

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/ipxe/ipxe/pull/103#event-3571626809___
ipxe-devel mailing list
ipxe-devel@lists.ipxe.org
https://lists.ipxe.org/mailman/listinfo/ipxe-devel

Re: [ipxe-devel] [ipxe/ipxe] successful wpa handshake (memcmp polarity) (#103)

[Michael Brown]

Good catch; thanks.  Pushed the memcmp fix as 
http://github.com/ipxe/ipxe/commit/0de5e6014 and pushed a simpler fix for the 
wpa_derive_ptk debug message as http://github.com/ipxe/ipxe/commit/ee2dc525b

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/ipxe/ipxe/pull/103#issuecomment-661904071___
ipxe-devel mailing list
ipxe-devel@lists.ipxe.org
https://lists.ipxe.org/mailman/listinfo/ipxe-devel

Re: [ipxe-devel] [ipxe/ipxe] successful wpa handshake (memcmp polarity) (#103)

[Joshua Oreman]

I haven't contributed to iPXE in many years, so I don't have write access to 
the Github repo, but this PR looks good to me.

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/ipxe/ipxe/pull/103#issuecomment-574368989___
ipxe-devel mailing list
ipxe-devel@lists.ipxe.org
https://lists.ipxe.org/mailman/listinfo/ipxe-devel

Re: [ipxe-devel] [ipxe/ipxe] successful wpa handshake (memcmp polarity) (#103)

[Joshua Oreman]

I wrote the original WPA code in 2009, and definitely successfully booted with 
it at that time. It looks like the incorrect-polarity memcmp() was only 
introduced in 2014: 
https://github.com/ipxe/ipxe/commit/8ee39f7432e63c2382ab3e7d24e234310f4532c9

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/ipxe/ipxe/pull/103#issuecomment-574368260___
ipxe-devel mailing list
ipxe-devel@lists.ipxe.org
https://lists.ipxe.org/mailman/listinfo/ipxe-devel

[ipxe-devel] [ipxe/ipxe] successful wpa handshake (memcmp polarity) (#103)

[Bazz]

Fix memcmp() to return proper standard positive/negative
values for unequal comparisons. Similar to commit 3946aa9. The 
current implementation is backwards (i.e. the functions are returning
negative when they should be positive and vice-versa).

Currently all other consumers of these functions only check the return value
for ==0 or !=0 and so we can safely change the implementation without
breaking things.

However, there is one call that checks the polarity of
`memcmp()`, and that is 
[wpa_derive_ptk()](https://github.com/ipxe/ipxe/blob/8f1514a00450119b04b08642c55aa674bdf5a4ef/src/net/80211/wpa.c#L290-L305)
 during the wireless WPA 4-way
handshake. Due to the incorrect memcmp polarity, the WPA handshake
creates an incorrect PTK, and the handshake would fail after step 2.
Undoubtedly, the AP noticed the supplicant failed the mic check. This
commit fixes that issue.

Signed-off-by: Michael Bazzinotti 

P.S. This wpa handshake bug is believed to have been longstanding for several 
years, and based on my current understanding, it possibly dates back to the 
release of the ipxe wpa feature itself. That makes no sense, but let's look 
at what I have uncovered. It seems a user encountered the exact same issue in 
[iPXE forums in 2016](https://forum.ipxe.org/showthread.php?tid=7943): a mic 
check failure. I realize net booting wirelessly is not popular nor well 
supported, and in that way bugs can live for a long time without being 
addressed. HOWEVER!

`wpa_derive_ptk()` would never run successfully unless with a different 
`memcmp()` function, due to the reversed polarity. How could a single person 
have ever successfully joined a WPA network using ipxe's `memcmp()`? I 
assume the code was ran successfully in the past, right? In those cases, was 
some other `memcmp()` somehow being used? For example, could the system's 
native memcmp() accidently have been superceding ipxe's?

 In any case, it seems a properly built ipxe that uses its internal `memcmp` 
could never generate a correct wpa ptk using `wpa_derive_ptk()` ? If you have 
any additional information to explain why, please by all means. Or join me in a 
state of wonder. Thanks
You can view, comment on, or merge this pull request online at:

  https://github.com/ipxe/ipxe/pull/103

-- Commit Summary --

  * [libc] Fix memcmp() to return proper values
  * [wpa] fix erroneous dbg printout in wpa_derive_ptk

-- File Changes --

M src/core/string.c (2)
M src/net/80211/wpa.c (9)

-- Patch Links --

https://github.com/ipxe/ipxe/pull/103.patch
https://github.com/ipxe/ipxe/pull/103.diff

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/ipxe/ipxe/pull/103
___
ipxe-devel mailing list
ipxe-devel@lists.ipxe.org
https://lists.ipxe.org/mailman/listinfo/ipxe-devel