def ciphertext_length(header, plaintext_length):
    """Calculates the complete ciphertext message length, given a complete header.

    :param header: Complete message header object
    :type header: aws_encryption_sdk.structures.MessageHeader
    :param int plaintext_length: Length of plaintext in bytes
    :rtype: int
    """
    ciphertext_length = header_length(header)
    ciphertext_length += body_length(header, plaintext_length)
    ciphertext_length += footer_length(header)
    return ciphertext_length