Exemplo n.º 1
0
    def to_key(self, passphrase):
        required_length = utils.symmetric_cipher_key_lengths.get(
                            self.symmetric_algorithm
                        )
        hash_length = utils.hash_lengths.get(self.hash_algorithm)
        pass_ = 0
        result = bytearray()
        # Length of content hashed on each iteration
        len2 = len(passphrase) + 8
        count = self.count
        if count is None:
            count = len2

        while (pass_ * hash_length) < required_length:
            # "If the hash size is less than the key size, multiple instances
            #  of the hash context are created -- enough to produce the
            #  required key data."
            hash_ = utils.get_hash_instance(self.hash_algorithm)

            # "These instances are preloaded with 0, 1, 2, ... octets of zeros
            #  (that is to say, the first instance has no preloading, the
            #  second gets preloaded with 1 octet of zero, the third is
            #  preloaded with two octets of zeros, and so forth)."
            hash_.update(bytearray([0x00] * pass_))

            # Spec is actually pretty vague here - had to determine when the
            # salt really should be hashed from gcrypt/gnupg source.
            for i in range(math.ceil(count / float(len2))):
                to_write = min(len2, count - (len2 * i))
                hash_.update((bytes(self.salt) + bytes(passphrase))[:to_write])

            # "Once the passphrase is hashed, the output data from the
            #  multiple hashes is concatenated, first hash leftmost, to
            #  produce the key data"
            result.extend(bytearray(hash_.digest()))
            pass_ += 1

        # "any excess octets on the right [are] discarded."
        return result[:required_length]
Exemplo n.º 2
0
 def get_algorithm_and_session_key(self, passphrase):
     hash_ = utils.get_hash_instance(self.key_hash_algorithm)
     hash_.update(passphrase)
     key = hash_.digest()
     return 1, key
Exemplo n.º 3
0
 def get_algorithm_and_session_key(self, passphrase):
     hash_ = utils.get_hash_instance(self.key_hash_algorithm)
     hash_.update(passphrase)
     key = hash_.digest()
     return 1, key