utils.py 文件源码

def get_rand_string(length=12, allowed_chars='0123456789abcdef'):
    """
    Returns a securely generated random string. Taken from the Django project

    The default length of 12 with the a-z, A-Z, 0-9 character set returns
    a 71-bit value. log_2((26+26+10)^12) =~ 71 bits
    """
    if not using_sysrandom:
        # This is ugly, and a hack, but it makes things better than
        # the alternative of predictability. This re-seeds the PRNG
        # using a value that is hard for an attacker to predict, every
        # time a random string is required. This may change the
        # properties of the chosen random sequence slightly, but this
        # is better than absolute predictability.
        random.seed(
            hashlib.sha256(
                ("%s%s" % (
                    random.getstate(),
                    time.time())).encode('utf-8')
            ).digest())
    return ''.join([random.choice(allowed_chars) for i in range(length)])