Ejemplo n.º 1
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	def edit_func(offset, newtext):
		assert offset <= len(ciphertext)

		new_p = plaintext[:offset] + newtext + plaintext[offset+len(newtext):]
		#print "New plaintext: %s" % new_p

		return aes_ctr(k, new_p, nonce)
Ejemplo n.º 2
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def challenge_26_encrypt(string_in):
    to_return = 'comment1=cooking%20MCs;userdata=' + string_in.replace(
        '=', '%3d').replace(
            ';', '%3b') + ';comment2=%20like%20a%20pound%20of%20bacon'
    to_return = str.encode(to_return)

    return aes_ctr(to_return, challenge_26_aes_key)
Ejemplo n.º 3
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def break_ctr_api(plaintext, ctr_key=None):
    '''
    Imagine the "edit" function was exposed to attackers by means of an API call that didn't
    reveal the key or the original plaintext; the attacker has the ciphertext and controls the
    offset and "new text".

    Recover the original plaintext.

    ciphera = a_plaintext xor keystream
    cipherb = b_plaintext xor keystream
    ciphera xor cipherb = a_plaintext xor keystream xor b_plaintext xor keystream
    ciphera xor cipherb xor b_plaintext = a_plaintext
    '''
    if ctr_key is None:
        ctr_key = generate_random_key()
    ciphertext = aes_ctr(plaintext, ctr_key)

    def api(offset, newtext):
        return edit_ctr_cipher(ciphertext, ctr_key, offset, newtext)

    a_cipher = ciphertext
    b_plaintext = b'A' * len(ciphertext)
    b_cipher = api(0, b_plaintext)
    return bytes(
        [a ^ b ^ c for a, b, c in zip(a_cipher, b_cipher, b_plaintext)])
Ejemplo n.º 4
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def check_ctr_bitflip(k, ciphertext, nonce):
	plaintext = aes_ctr(k, ciphertext, nonce)
	print "decrypted: ", repr(plaintext)
	pieces = plaintext.split(';')
	for p in pieces:
		if p == 'admin=true':
			return True

	return False
Ejemplo n.º 5
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def aes_ctr_oracle(k, plaintext, nonce):
	s1 = "comment1=cooking%20MCs;userdata="
	s2 = ";comment2=%20like%20a%20pound%20of%20bacon"

	# strip ';' and '=' from plaintext
	plaintext = plaintext.replace(';','')
	plaintext = plaintext.replace('=','')

	return aes_ctr(k, s1 + plaintext + s2, nonce)
Ejemplo n.º 6
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def aes_ctr_get_edit_func(plaintext):

	k = os.urandom(16)
	nonce = os.urandom(8)

	ciphertext = aes_ctr(k, plaintext, nonce)

	def edit_func(offset, newtext):
		assert offset <= len(ciphertext)

		new_p = plaintext[:offset] + newtext + plaintext[offset+len(newtext):]
		#print "New plaintext: %s" % new_p

		return aes_ctr(k, new_p, nonce)

	return ciphertext, edit_func
Ejemplo n.º 7
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def test_challenge19():
    b64strings = [
        'SSBoYXZlIG1ldCB0aGVtIGF0IGNsb3NlIG9mIGRheQ==',
        'Q29taW5nIHdpdGggdml2aWQgZmFjZXM=',
        'RnJvbSBjb3VudGVyIG9yIGRlc2sgYW1vbmcgZ3JleQ==',
        'RWlnaHRlZW50aC1jZW50dXJ5IGhvdXNlcy4=',
        'SSBoYXZlIHBhc3NlZCB3aXRoIGEgbm9kIG9mIHRoZSBoZWFk',
        'T3IgcG9saXRlIG1lYW5pbmdsZXNzIHdvcmRzLA==',
        'T3IgaGF2ZSBsaW5nZXJlZCBhd2hpbGUgYW5kIHNhaWQ=',
        'UG9saXRlIG1lYW5pbmdsZXNzIHdvcmRzLA==',
        'QW5kIHRob3VnaHQgYmVmb3JlIEkgaGFkIGRvbmU=',
        'T2YgYSBtb2NraW5nIHRhbGUgb3IgYSBnaWJl', 'VG8gcGxlYXNlIGEgY29tcGFuaW9u',
        'QXJvdW5kIHRoZSBmaXJlIGF0IHRoZSBjbHViLA==',
        'QmVpbmcgY2VydGFpbiB0aGF0IHRoZXkgYW5kIEk=',
        'QnV0IGxpdmVkIHdoZXJlIG1vdGxleSBpcyB3b3JuOg==',
        'QWxsIGNoYW5nZWQsIGNoYW5nZWQgdXR0ZXJseTo=',
        'QSB0ZXJyaWJsZSBiZWF1dHkgaXMgYm9ybi4=',
        'VGhhdCB3b21hbidzIGRheXMgd2VyZSBzcGVudA==',
        'SW4gaWdub3JhbnQgZ29vZCB3aWxsLA==', 'SGVyIG5pZ2h0cyBpbiBhcmd1bWVudA==',
        'VW50aWwgaGVyIHZvaWNlIGdyZXcgc2hyaWxsLg==',
        'V2hhdCB2b2ljZSBtb3JlIHN3ZWV0IHRoYW4gaGVycw==',
        'V2hlbiB5b3VuZyBhbmQgYmVhdXRpZnVsLA==', 'U2hlIHJvZGUgdG8gaGFycmllcnM/',
        'VGhpcyBtYW4gaGFkIGtlcHQgYSBzY2hvb2w=',
        'QW5kIHJvZGUgb3VyIHdpbmdlZCBob3JzZS4=',
        'VGhpcyBvdGhlciBoaXMgaGVscGVyIGFuZCBmcmllbmQ=',
        'V2FzIGNvbWluZyBpbnRvIGhpcyBmb3JjZTs=',
        'SGUgbWlnaHQgaGF2ZSB3b24gZmFtZSBpbiB0aGUgZW5kLA==',
        'U28gc2Vuc2l0aXZlIGhpcyBuYXR1cmUgc2VlbWVkLA==',
        'U28gZGFyaW5nIGFuZCBzd2VldCBoaXMgdGhvdWdodC4=',
        'VGhpcyBvdGhlciBtYW4gSSBoYWQgZHJlYW1lZA==',
        'QSBkcnVua2VuLCB2YWluLWdsb3Jpb3VzIGxvdXQu',
        'SGUgaGFkIGRvbmUgbW9zdCBiaXR0ZXIgd3Jvbmc=',
        'VG8gc29tZSB3aG8gYXJlIG5lYXIgbXkgaGVhcnQs',
        'WWV0IEkgbnVtYmVyIGhpbSBpbiB0aGUgc29uZzs=',
        'SGUsIHRvbywgaGFzIHJlc2lnbmVkIGhpcyBwYXJ0',
        'SW4gdGhlIGNhc3VhbCBjb21lZHk7',
        'SGUsIHRvbywgaGFzIGJlZW4gY2hhbmdlZCBpbiBoaXMgdHVybiw=',
        'VHJhbnNmb3JtZWQgdXR0ZXJseTo=', 'QSB0ZXJyaWJsZSBiZWF1dHkgaXMgYm9ybi4='
    ]
    ciphertexts = [
        set3.aes_ctr(base64.b64decode(s), constants.key) for s in b64strings
    ]
    set3.challenge19(ciphertexts)
Ejemplo n.º 8
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def challenge26_isadmin(ciphertext):
    return b';admin=true;' in set3.aes_ctr(ciphertext, constants.key)
Ejemplo n.º 9
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def challenge26_encrypt(user_input):
    user_input = user_input.replace(b';', b'%3B')
    user_input = user_input.replace(b'=', b'%3D')
    plaintext = b'comment1=cooking%20MCs;userdata=' + user_input
    plaintext += b';comment2=%20like%20a%20pound%20of%20bacon'
    return set3.aes_ctr(plaintext, constants.key)
Ejemplo n.º 10
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def challenge25_edit(ciphertext, offset, newtext):
    plaintext = set3.aes_ctr(ciphertext, constants.key)
    return set3.aes_ctr(plaintext[:offset] + newtext, constants.key)
Ejemplo n.º 11
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def challenge_26_detect_admin(cipher):
    decrypted = aes_ctr(cipher, challenge_26_aes_key)
    return decrypted.count(b";admin=true") > 0
Ejemplo n.º 12
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def test_challenge25():
    with open('25.txt') as file:
        plaintexts = [base64.b64decode(line.strip().encode()) for line in file]
    for plaintext in plaintexts:
        ciphertext = set3.aes_ctr(plaintext, constants.key)
        assert set4.challenge25(ciphertext) == plaintext
Ejemplo n.º 13
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def test_challenge18():
    ct = b'L77na/nrFsKvynd6HzOoG7GHTLXsTVu9qvY/2syLXzhPweyyMTJULu/6/kXX0KSvoOLSFQ=='
    result = set3.aes_ctr(base64.b64decode(ct), b'YELLOW SUBMARINE')
    assert result == b"Yo, VIP Let's kick it Ice, Ice, baby Ice, Ice, baby "