transport.py 文件源码

def _get_cipher(self, name, key, iv):
        if name not in self._cipher_info:
            raise SSHException('Unknown client cipher ' + name)
        if name in ('arcfour128', 'arcfour256'):
            # arcfour cipher
            cipher = self._cipher_info[name]['class'].new(key)
            # as per RFC 4345, the first 1536 bytes of keystream
            # generated by the cipher MUST be discarded
            cipher.encrypt(" " * 1536)
            return cipher
        elif name.endswith("-ctr"):
            # CTR modes, we need a counter
            counter = Counter.new(nbits=self._cipher_info[name]['block-size'] * 8, initial_value=util.inflate_long(iv, True))
            return self._cipher_info[name]['class'].new(key, self._cipher_info[name]['mode'], iv, counter)
        else:
            return self._cipher_info[name]['class'].new(key, self._cipher_info[name]['mode'], iv)