def mydecrypt(password, data):
'''
Decrypt some data. Input must be bytes.
@param password: The secret value used as the basis for a key.
This should be as long as varied as possible. Try to avoid common words.
@param data: The data to be decrypted, typically as bytes.
@return: The decrypted data, as bytes. If the original message was a
string you can re-create that using `result.decode('utf8')`.
'''
simplecrypt._assert_not_unicode(data)
simplecrypt._assert_header_prefix(data)
print "mydecrypt -- 1"
version = simplecrypt._assert_header_version(data)
print "mydecrypt -- 1.1"
simplecrypt._assert_decrypt_length(data, version)
print "mydecrypt -- 1.2"
raw = data[simplecrypt.HEADER_LEN:]
salt = raw[:simplecrypt.SALT_LEN[version]//8]
print "mydecrypt -- 2"
hmac_key, cipher_key = simplecrypt._expand_keys(password, salt)
hmac = raw[-simplecrypt.HASH.digest_size:]
hmac2 = simplecrypt._hmac(hmac_key, data[:-simplecrypt.HASH.digest_size])
simplecrypt._assert_hmac(hmac_key, hmac, hmac2)
print "mydecrypt -- 3"
counter = simplecrypt.Counter.new(simplecrypt.HALF_BLOCK, prefix=salt[:simplecrypt.HALF_BLOCK//8])
cipher = simplecrypt.AES.new(cipher_key, simplecrypt.AES.MODE_CTR, counter=counter)
r = cipher.decrypt(raw[simplecrypt.SALT_LEN[version]//8:-simplecrypt.HASH.digest_size])
print "[%s] %d" % (r,len(r))
return r
def test_header(self):
ctext = bytearray(encrypt('password', 'message'))
assert ctext[:HEADER_LEN] == HEADER[LATEST]
for i in range(len(HEADER)):
ctext2 = bytearray(ctext)
ctext2[i] = 1
try:
_assert_header_prefix(ctext2)
_assert_header_version(ctext2)
assert False, 'expected error'
except DecryptionException as e:
assert 'bad header' in str(e), e
if i > 1: assert 'more recent version of simple-crypt' in str(e), e
else: assert 'not generated by simple-crypt' in str(e)
ctext2 = bytearray(ctext)
ctext2[len(HEADER)] = 1
try:
decrypt('password', ctext2)
assert False, 'expected error'
except DecryptionException as e:
assert 'format' not in str(e), e