secrets --- 生成管理密码的安全随机数

Added in version 3.6.

源代码: Lib/secrets.py

The secrets module is used for generating cryptographically strong random numbers suitable for managing data such as passwords, account authentication, security tokens, and related secrets.

In particular, secrets should be used in preference to the default pseudo-random number generator in the random module, which is designed for modelling and simulation, not security or cryptography.

参见

PEP 506

随机数

The secrets module provides access to the most secure source of randomness that your operating system provides.

class secrets.SystemRandom

用操作系统提供的最高质量源生成随机数的类。详见 random.SystemRandom。

secrets.choice(seq)

返回一个从非空序列中随机选取的元素。

secrets.randbelow(exclusive_upper_bound)

返回 [0, exclusive_upper_bound) 范围内的随机整数。

secrets.randbits(k)

返回有 k 个随机比特位的非负数。

生成 Token

The secrets module provides functions for generating secure tokens, suitable for applications such as password resets, hard-to-guess URLs, and similar.

secrets.token_bytes(nbytes=None)

Return a random byte string containing nbytes number of bytes.

If nbytes is not specified or None, DEFAULT_ENTROPY is used instead.

>>> token_bytes(16)
b'\xebr\x17D*t\xae\xd4\xe3S\xb6\xe2\xebP1\x8b'
secrets.token_hex(nbytes=None)

Return a random text string, in hexadecimal. The string has nbytes random bytes, each byte converted to two hex digits.

If nbytes is not specified or None, DEFAULT_ENTROPY is used instead.

>>> token_hex(16)
'f9bf78b9a18ce6d46a0cd2b0b86df9da'
secrets.token_urlsafe(nbytes=None)

Return a random URL-safe text string, containing nbytes random bytes. The text is Base64 encoded, so on average each byte results in approximately 1.3 characters.

If nbytes is not specified or None, DEFAULT_ENTROPY is used instead.

>>> token_urlsafe(16)
'Drmhze6EPcv0fN_81Bj-nA'

Token 应当使用多少个字节？

To be secure against brute-force attacks, tokens need to have sufficient randomness. Unfortunately, what is considered sufficient will necessarily increase as computers get more powerful and able to make more guesses in a shorter period. As of 2015, it is believed that 32 bytes (256 bits) of randomness is sufficient for the typical use-case expected for the secrets module.

要自行管理 Token 长度的用户，可以通过为 token_* 函数指定 int 参数显式指定 Token 要使用多大的随机性。该参数以字节数表示随机性大小。

Otherwise, if no argument is provided, or if the argument is None, the token_* functions uses DEFAULT_ENTROPY instead.

secrets.DEFAULT_ENTROPY

Default number of bytes of randomness used by the token_* functions.

The exact value is subject to change at any time, including during maintenance releases.

其他功能

secrets.compare_digest(a, b)

如果字符串或 字节型对象 a 与 b 相等则返回 True，否则返回 False，使用了“常数时间比较”来降低 定时攻击 的风险。请参阅 hmac.compare_digest() 了解更多细节。

应用技巧与最佳实践

This section shows recipes and best practices for using secrets to manage a basic level of security.

生成长度为八个字符的字母数字密码：

import string
import secrets
alphabet = string.ascii_letters + string.digits
password = ''.join(secrets.choice(alphabet) for i in range(8))

备注

应用程序不应该 以可恢复的格式存储密码，无论是纯文本的还是加密的。 它们应当使用高加密强度的单向（不可逆）哈希函数加盐并执行哈希运算。

生成长度为十个字符的字母数字密码，包含至少一个小写字母，至少一个大写字母以及至少三个数字：

import string
import secrets
alphabet = string.ascii_letters + string.digits
while True:
    password = ''.join(secrets.choice(alphabet) for i in range(10))
    if (any(c.islower() for c in password)
            and any(c.isupper() for c in password)
            and sum(c.isdigit() for c in password) >= 3):
        break

生成 XKCD 风格的密码串：

import secrets
# 在标准 Linux 系统中，使用方便的字典文件。
# 其他系统平台可能需要提供它们专用的词列表。
with open('/usr/share/dict/words') as f:
    words = [word.strip() for word in f]
    password = ' '.join(secrets.choice(words) for i in range(4))

生成临时密保 URL，包含密码恢复应用的安全 Token：

import secrets
url = 'https://example.com/reset=' + secrets.token_urlsafe()