def postgres_passwd(password, username, uppercase=False):
    """
    Reference(s):
        http://pentestmonkey.net/blog/cracking-postgres-hashes/

    >>> postgres_passwd(password='testpass', username='testuser', uppercase=False)
    'md599e5ea7a6f7c3269995cba3927fd0093'
    """


    if isinstance(username, unicode):
        username = unicode.encode(username, UNICODE_ENCODING)

    if isinstance(password, unicode):
        password = unicode.encode(password, UNICODE_ENCODING)

    retVal = "md5%s" % md5(password + username).hexdigest()

    return retVal.upper() if uppercase else retVal.lower()