wpa-handshake with python - hashing difficulties

Question

I try to write a Python program which calculates the WPA-handshake, but I have problems with the hashes. For comparison I installed cowpatty (to see where I start beeing wrong).

My PMK-generation works fine, but the PTK-calculation alsways seems to be wrong. I am not sure if I have to format my input (macadresses and noces) or just give them into the function as a string.

I will give you my routerinformation, which is no problem since I just set it up for testing.

My program looks as follows:

import hmac,hashlib,binascii

passPhrase  = "10zZz10ZZzZ"
ssid        = "Netgear 2/158" 
A           = "Pairwise key expansion" 
APmac       = "001e2ae0bdd0"
Clientmac   = "cc08e0620bc8"
ANonce      = "61c9a3f5cdcdf5fae5fd760836b8008c863aa2317022c7a202434554fb38452b"
SNonce      = "60eff10088077f8b03a0e2fc2fc37e1fe1f30f9f7cfbcfb2826f26f3379c4318"
B           = min(APmac,Clientmac)+max(APmac,Clientmac)+min(ANonce,SNonce)+max(ANonce,SNonce)
data="0103005ffe010900200000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"

def customPRF512(key,A,B):
    blen = 64
    i    = 0
    R    = ''
    while i<=((blen*8+159)/160):
        hmacsha1 = hmac.new(key,A+chr(0x00)+B+chr(i),sha)
        i+=1
        R = R+hmacsha1.digest()
    return R[:blen]


pmk = pbkdf2(passPhrase, ssid, 4096, 32) #no sourcecode, since b2a_p(pmk) output fits to those of cowpatty

ptk = customPRF512(pmk,A,B) #the prf-function fits the pseudocode in the ieee, but does not give me the correct output (like cowpatty does)
# and i have no idea why :(

print b2a_p(pmk),"\n\n\n"
print b2a_p(ptk),"\n\n\n"

mic1 = hmac.new(ptk[0:16],data)
print mic1.hexdigest() #should be the mic-calculation, not sure if this is correct...

the desired outputs (which cowpatty confirmed) are:

PMK is
 01b8 09f9 ab2f b5dc 4798 4f52 fb2d 112e
 13d8 4ccb 6b86 d4a7 193e c529 9f85 1c48

Calculated PTK for "10zZz10ZZzZ" is
 bf49 a95f 0494 f444 2716 2f38 696e f8b6 
 428b cf8b a3c6 f0d7 245a d314 a14c 0d18
 efd6 38aa e653 c908 a7ab c648 0a7f 4068
 2479 c970 8aaa abc3 eb7e da28 9d06 d535

Calculated MIC with "10zZz10ZZzZ" is
 4528 2522 bc67 07d6 a70a 0317 a3ed 48f0

Maybe someone of you could tell me, why my program simply doesn't work. Do the hmac-functions work correctly? Is my input formatted wrong? Do I have to regard endianess anywhere? Thanks for your time in advance, I would appreciate any help!

Minutes

Answer 1

Alright, I figured it out by myself... more by desperate testing and some luck, than successful research, which lead to nothing long enough. Instead of using the MAC-adresses and nonces as the strings they were, I had to unhexlify them. I used

a2b_hex() #alternatively unhexlify()

My final code looks somewhat like this, defs excluded:

import hmac,hashlib,binascii
passPhrase="10zZz10ZZzZ"
ssid        = "Netgear 2/158"
A           = "Pairwise key expansion"
APmac       = a2b_hex("001e2ae0bdd0")
Clientmac   = a2b_hex("cc08e0620bc8")
ANonce      = a2b_hex("61c9a3f5cdcdf5fae5fd760836b8008c863aa2317022c7a202434554fb38452b")
SNonce      = a2b_hex("60eff10088077f8b03a0e2fc2fc37e1fe1f30f9f7cfbcfb2826f26f3379c4318")
B           = min(APmac,Clientmac)+max(APmac,Clientmac)+min(ANonce,SNonce)+max(ANonce,SNonce)
data        = a2b_hex("0103005ffe01090020000000000000000100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000")

pmk     = pbkdf2(passPhrase, ssid, 4096, 32) 
ptk     = customPRF512(pmk,A,B)
mic     = hmac.new(ptk[0:16],data)

print "desiredpmk:\t","01b809f9ab2fb5dc47984f52fb2d112e13d84ccb6b86d4a7193ec5299f851c48"
print "pmk:\t\t",b2a_hex(pmk),"\n"
print "desired ptk:\t","bf49a95f0494f44427162f38696ef8b6"
print "ptk:\t\t",b2a_hex(ptk[0:16]),"\n"
print "desired mic:\t","45282522bc6707d6a70a0317a3ed48f0"
print "mic:\t\t",mic.hexdigest(),"\n"

So the answers to my questions were: yes, hashfunctions work correctly, yes, input is formatted wrong, no, no endianess-issues.

Minutes

Answer 2

Thanks for posting. This helped me out, so posting my revisions:

#==========================================================================================
#
# Verify the MIC code in EAPoL Message #2 is valid, or not (WPA2)
#
#==========================================================================================
#
# The home for this code is (so check for updates):
#
#     https://www.duckware.com/tech/verify-mic-in-four-way-handshake.py.txt
#
#   and this code is fully public, as it was based on/derived from this public code:
#
#     https://mcmap.net/q/1525670/-wpa-handshake-with-python-hashing-difficulties
#
# 1. PMK: 'Pairwise Master Key' (256-bit) is generated from SSID/PASS in WPA2:
#
#     o https://www.wireshark.org/tools/wpa-psk.html (SSID/PASS to PMK)
#     o http://anandam.name/pbkdf2/ (Password-Based Key Derivation Function 2)
#
# 2. PRF512: The PRF-512 function is used to compute four 128-bit keys (KCK,KEK,TK1,TK2).
#    For details on this function, see:
#
#     o http://etutorials.org/Networking/802.11+security.+wi-fi+protected+access+and+802.11i/Part+II+The+Design+of+Wi-Fi+Security/Chapter+10.+WPA+and+RSN+Key+Hierarchy/Computing+the+Temporal+Keys/
#
# 3. KCK: The KCK (first 128 bits of the PTK; see above) are used to generate the MIC:
#
#     o https://tldp.org/HOWTO/8021X-HOWTO/intro.html
#
# RUN: Run the code below in an ONLINE Python 2.7 compiler.  For example:
#
#     o https://repl.it/languages/python
#     o https://www.tutorialspoint.com/execute_python_online.php
#
# CUSTOMIZE: How to customize the code below:
#
#    1) PCAP the problematic handshake (TIP: use tcpdump with ether host xx:xx:xx:xx:xx:xx)
#    2) Update SSID/PASS vars below with the known Wi-Fi name/password
#    3) Copy entire Ethernet frames for EAPoL Message #1/#2 into EAPOL1/2 vars below.
#       TIP: In Wireshark, right click on Ethernet frame, 'Copy' / '...as a Hex Stream' / paste below
#    4) Use first with a working 4-way handshake (to confirm proper usage; MIC match), then apply
#       to non-working 4-way handshake to confirm that the MIC in Message #2 is good/bad.
#    5) The code below, unmodified, results in a MIC found/calculated 'match'
#
# See also:
#
#     o https://www.wifi-professionals.com/2019/01/4-way-handshake
#     o https://mcmap.net/q/1624409/-creating-wpa-message-integrity-code-mic-with-python
#     o https://www.shellvoide.com/wifi/understanding-wpa-wpa2-hash-mic-cracking-process-python/
#     o https://ww.ins1gn1a.com/understanding-wpa-psk-cracking/
#     o https://docs.python.org/3/library/binascii.html
#     o https://mcmap.net/q/1624410/-how-to-convert-a-mac-number-to-mac-string
#
#==========================================================================================

import hmac,hashlib,binascii

def to_mac(addr): return ':'.join(addr[i:i+2] for i in range(0,len(addr),2))
def PRF_512(key,A,B): return ''.join(hmac.new(key,A+chr(0)+B+chr(i),hashlib.sha1).digest() for i in range(4))[:64]
def a2b(s): return binascii.a2b_hex(s);
def b2a(by): return binascii.b2a_hex(by);

EAPOL1 = a2b("60f189052d94a00460216606888e0203005f02008a00100000000000000001141f7a3ebdc0b51712934bef6e43ea13f80cb460f121f35408aa607046e239980000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000")
EAPOL2 = a2b("a0046021660660f189052d94888e0103007502010a000000000000000000015b46c7165f504c664aed90b78f3b705e02b4b029a67e3189d1632479d7e7a4e6000000000000000000000000000000000000000000000000000000000000000056de18f5efa272a4663560b73c537a65001630140100000fac040100000fac040100000fac028000")
SSID   = "your-wifi-ssid"
PASS   = "your-wifi-password"
PMK    = hashlib.pbkdf2_hmac('sha1', PASS, SSID, 4096, 32)  

VER_WPA = 2   # WPA2 means use 'SHA1'
XAUTH   = a2b("888E")
if EAPOL1[0:6]==EAPOL2[6:12] and EAPOL2[0:6]==EAPOL1[6:12] and EAPOL1[12:14]==XAUTH and EAPOL1[12:14]==XAUTH:
  if ord(EAPOL1[20])%8==VER_WPA and ord(EAPOL2[20])%8==VER_WPA:
    R1 = EAPOL1[31:63]      # random 1 (AP nonce)
    R2 = EAPOL2[31:63]      # random 2 (STA nonce)
    M1 = EAPOL2[0:6]        # MAC 1 (AP MAC)
    M2 = EAPOL1[0:6]        # MAC 2 (STA MAC)

    # Generate KCK, KEK, TK1, TK2 from the PMK (and AP/STA info)
    PTK = PRF_512(PMK,"Pairwise key expansion",min(M1,M2)+max(M1,M2)+min(R1,R2)+max(R1,R2))
    KCK = PTK[0:16];

    # try to validate the MIC in EAPoL message #2 is correct
    MICRAW   = hmac.new(KCK,EAPOL2[14:95]+a2b("00000000000000000000000000000000")+EAPOL2[111:],hashlib.sha1)
    MICFOUND = b2a(EAPOL2[95:111])
    MICCALC  = MICRAW.hexdigest()[0:32]

    print "SSID/PASS: ",SSID,"/",PASS
    print "PMK:       ",b2a(PMK)
    print "AP-MAC:    ",to_mac(b2a(M1))
    print "STA-MAC:   ",to_mac(b2a(M2))
    print "AP-NONCE:  ",b2a(R1)
    print "STA-NONCE: ",b2a(R2)
    print "KCK:       ",b2a(KCK)
    print "MIC-found: ",MICFOUND
    print "MIC-calc:  ",MICCALC
    print "Result:    ",("OK: EAPoL message #2 validated" if MICFOUND==MICCALC else "ERROR: MIC does not match")
  else:
    print "***ERROR: Did not find expected 'WPA2' version in EAPoL messages"
else:
  print "***ERROR: Problem validated Ethernet frames.  Do EAPOL1 and EAPOL2 both include the Ethernet headers?"

Silva