62 lines
2.1 KiB
Python
62 lines
2.1 KiB
Python
import requests
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from binascii import hexlify, unhexlify
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url = 'http://192.168.0.222:5000'
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# Any registered username and password
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username = 'myBLfLEDraYh3Dq'
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password = '9GQLqu39EviKw'
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# default comment and any much longer string
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original = 'No description yet'
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description = 'stringadiversamapiulungastringadiversamapiulungastringa'.encode('ascii')
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# do login
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s = requests.session()
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r = s.post(url + '/login', data={'username': username, 'password': password})
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cur_iv = s.cookies['iv']
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ciphertext1 = s.cookies['session']
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# loop trough 256 requests to obtain a two time pad
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for i in range(int(cur_iv), int(cur_iv)+256):
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s.post(url + '/user', data={'description': description})
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if s.cookies['iv'] == cur_iv:
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ciphertext2 = s.cookies['session']
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for i in range(0, len(ciphertext1), 2):
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if ciphertext1[i:i+1] != ciphertext2[i:i+1]:
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break
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# obtain new cookis with the original comment to flip the fals in true
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s.post(url + '/user', data={'description': original})
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cur_iv = s.cookies['iv']
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uid = s.cookies['uid']
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description = description.hex()
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ciphertext1 = ciphertext1[i:]
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ciphertext2 = ciphertext2[i:i+len(description)]
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# xor our known plaintext with the given ciphertext to recover part of the rc4 stream
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key = '{:x}'.format(int(ciphertext2, 16) ^ int(description, 16))[0:len(ciphertext1)]
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# xor our known rc4 stream with the default comment on the same iteration to decrypt the final parte of the cookie
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plaintext = unhexlify('{:x}'.format(int(key, 16) ^ int(ciphertext1, 16)))
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# print the plaintext and notice it has a show_flag parameter
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print('[*] Decrypted first cookie: ' + plaintext.decode('ascii'))
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# xor 'true ' with 'false' to calculate the value to use to flip the ciphertext
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flip = '{:x}'.format(int('true '.encode('ascii').hex(), 16) ^ int('false'.encode('ascii').hex(), 16))
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cur_session = s.cookies['session']
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# xor to obtain 'true ' from false'
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flip = '{:x}'.format(int(flip, 16) ^ int(cur_session[-12:-2], 16))
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session = cur_session[0:-12] + flip + cur_session[-2:]
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# get the flag!
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flag = requests.get(url + '/user', cookies={'iv': cur_iv, 'uid': uid, 'session': session})
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print('[*] Got the flag: ' + flag.text)
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