如何为JWE添加到期?

Question

我正在尝试通过以下方式为我使用 jwcrypto 库生成的 JWE 添加到期时间

from jwcrypto import jwe, jwk, jwt
from datetime import datetime, timedelta
import time
# create JWK from existing key
jwk_str = '{"k":"29Js2yXM6P_4v9K1mHDlYVHw8Xvm_GEhvMTvKTRLRzY","kty":"oct"}'
jwk_key = jwk.JWK.from_json(jwk_str)
# calculate expiry time
d = datetime.now() + timedelta(seconds=5)
epoch = datetime.utcfromtimestamp(0)
total_seconds =  (d - epoch).total_seconds()
# Add exp to the claims
claims={"exp": total_seconds, "sub": "Some random payload"}
print(claims)
jwttoken = jwt.JWT(header={"alg": "A256KW", "enc": "A256CBC-HS512"}, claims=claims)
jwttoken.make_encrypted_token(jwk_key)
jwetokenstr = jwttoken.serialize()
print(jwetokenstr)
# wait for 10 seconds to cross the expiry time
time.sleep(10)
jwttoken = jwt.JWT()
jwttoken.deserialize(token, jwk_key) # Ideally this line should fail as expiry is reached but it doesn't
print(jwttoken.claims)

我正在获取有效负载，但到期声明未读取，并且在到期时不会失败。 我做错了什么？

Answer 1

这最终会减少为日期时间操作错误。

JSON Web 令牌的exp声明应填写从过期时间纪元开始的秒数。

datetime.now()返回对象的本地时间(不是 UTC 时间datetime.datetime。然后，上面的代码继续从 UTC 时间datetime.datetime对象 0 纪元时间中减去此本地时间datetime.datetime对象，并计算这两者之间的总秒数以确定到期时间。但是，由于这是将本地时间日期时间与 UTC 时间日期时间进行比较，因此此处的秒数实际上与纪元时间相差的本地时区与UTC的常数因子相差。

例如，如果我住在一个时间比 UTC 早 5 小时的地方，我实际上会使用此代码使用比我想要到期的真实纪元时间相差5 * 60 * 60秒的纪元时间。

相反，您可以简单地使用round(time.time()) + x其中x是 JWT 应过期的将来向前移动的秒数。time.time()从纪元返回秒数(但作为浮点数，因此您需要舍入(。

例如：

from jwcrypto import jwe, jwk, jwt
from datetime import datetime, timedelta
import time
jwk_str = '{"k":"29Js2yXM6P_4v9K1mHDlYVHw8Xvm_GEhvMTvKTRLRzY","kty":"oct"}'
jwk_key = jwk.JWK.from_json(jwk_str)
jwt_valid_seconds = 3
expiry_time = round(time.time()) + jwt_valid_seconds
claims={"exp": expiry_time, "sub": "Some random payload"}
jwttoken = jwt.JWT(header={"alg": "A256KW", "enc": "A256CBC-HS512"}, claims=claims)
jwttoken.make_encrypted_token(jwk_key)
jwetokenstr = jwttoken.serialize()
jwttoken2 = jwt.JWT()
jwttoken2.deserialize(jwetokenstr, jwk_key)
print('This should succeed because we are deserializing immediately before the JWT has expired:')
print(jwttoken2.claims)
# Wait for the JWT to expire, and then extra time for the leeway.
leeway = 60
time.sleep(leeway + jwt_valid_seconds + 1)
jwttoken2 = jwt.JWT()
print('nThis should fail due to the JWT expiring:')
jwttoken2.deserialize(jwetokenstr, jwk_key)

给出输出

(env) $ python jwe_expiry.py
This should succeed because we are deserializing immediately before the JWT has expired:
{"exp":1576737332,"sub":"Some random payload"}
This should fail due to the JWT expiring:
Traceback (most recent call last):
File "jwe_expiry.py", line 26, in <module>
jwttoken2.deserialize(jwetokenstr, jwk_key)
File "... python3.7/site-packages/jwcrypto/jwt.py", line 493, in deserialize
self._check_provided_claims()
File "... python3.7/site-packages/jwcrypto/jwt.py", line 370, in _check_provided_claims
self._check_default_claims(claims)
File "... python3.7/site-packages/jwcrypto/jwt.py", line 351, in _check_default_claims
self._check_exp(claims['exp'], time.time(), self._leeway)
File "... python3.7/site-packages/jwcrypto/jwt.py", line 333, in _check_exp
claim, limit, leeway))
jwcrypto.jwt.JWTExpired: Expired at 1576737332, time: 1576737392(leeway: 60)