使用python boto3为AWS Cognito实现USER_SRP_AUTH

Question

亚马逊提供iOS,Android和Javascript Cognito SDK,提供高级身份验证用户操作.

例如,请参见用例4:

https://github.com/aws/amazon-cognito-identity-js

但是,如果您使用的是python/boto3,那么您只需要一对基元:cognito.initiate_auth和cognito.respond_to_auth_challenge.

我试图使用这些原语以及pysrplib与USER_SRP_AUTH流进行身份验证,但我所拥有的是不起作用.

在调用RespondToAuthChallenge操作时出现"出错(NotAuthorizedException)总是失败:用户名或密码不正确." (使用JS SDK查找用户名/密码对.)

我的怀疑是我正在构建错误的挑战响应(步骤3),和/或当它想要base64时传递Congito十六进制字符串,反之亦然.

有没有人得到这个工作？有谁看到我做错了什么？

我试图复制authenticateUser在Javascript SDK中找到的调用的行为:

https://github.com/aws/amazon-cognito-identity-js/blob/master/src/CognitoUser.js#L138

但我做错了什么,无法弄清楚是什么.

#!/usr/bin/env python
import base64
import binascii
import boto3
import datetime as dt
import hashlib
import hmac

# http://pythonhosted.org/srp/
# https://github.com/cocagne/pysrp
import srp

bytes_to_hex = lambda x: "".join("{:02x}".format(ord(c)) for c in x)

cognito = boto3.client('cognito-idp', region_name="us-east-1")

username = "foobar@foobar.com"
password = "123456"

user_pool_id = u"us-east-1_XXXXXXXXX"
client_id = u"XXXXXXXXXXXXXXXXXXXXXXXXXX"

# Step 1:
# Use SRP lib to construct a SRP_A value.

srp_user = srp.User(username, password)
_, srp_a_bytes = srp_user.start_authentication()

srp_a_hex = bytes_to_hex(srp_a_bytes)

# Step 2:
# Submit USERNAME & SRP_A to Cognito, get challenge.

response = cognito.initiate_auth(
    AuthFlow='USER_SRP_AUTH',
    AuthParameters={ 'USERNAME': username, 'SRP_A': srp_a_hex },
    ClientId=client_id,
    ClientMetadata={ 'UserPoolId': user_pool_id })

# Step 3:
# Use challenge parameters from Cognito to construct 
# challenge response.

salt_hex         = response['ChallengeParameters']['SALT']
srp_b_hex        = response['ChallengeParameters']['SRP_B']
secret_block_b64 = response['ChallengeParameters']['SECRET_BLOCK']

secret_block_bytes = base64.standard_b64decode(secret_block_b64)
secret_block_hex = bytes_to_hex(secret_block_bytes)

salt_bytes = binascii.unhexlify(salt_hex)
srp_b_bytes = binascii.unhexlify(srp_b_hex)

process_challenge_bytes = srp_user.process_challenge(salt_bytes,                          
                                                     srp_b_bytes)

timestamp = unicode(dt.datetime.utcnow().strftime("%a %b %d %H:%m:%S +0000 %Y"))

hmac_obj = hmac.new(process_challenge_bytes, digestmod=hashlib.sha256)
hmac_obj.update(user_pool_id.split('_')[1].encode('utf-8'))
hmac_obj.update(username.encode('utf-8'))
hmac_obj.update(secret_block_bytes)
hmac_obj.update(timestamp.encode('utf-8'))

challenge_responses = {
    "TIMESTAMP": timestamp.encode('utf-8'),
    "USERNAME": username.encode('utf-8'),
    "PASSWORD_CLAIM_SECRET_BLOCK": secret_block_hex,
    "PASSWORD_CLAIM_SIGNATURE": hmac_obj.hexdigest()
}

# Step 4:
# Submit challenge response to Cognito.

response = cognito.respond_to_auth_challenge(
    ClientId=client_id,
    ChallengeName='PASSWORD_VERIFIER',
    ChallengeResponses=challenge_responses)

Answer 1

您的实施中存在许多错误.例如:

1. pysrp默认情况下使用SHA1算法.它应该设置为SHA256.
2. _ng_const 长度应为3072位,应从中复制 amazon-cognito-identity-js
3. 没有hkdf功能pysrp.
4. 响应应该包含secret_block_b64,而不是secret_block_hex.
5. 错误的时间戳格式. %H:%m:%S表示"小时:月:秒",+0000应替换为UTC.

有没有人得到这个工作？

是.它在warrant.aws_srp模块中实现. https://github.com/capless/warrant/blob/develop/warrant/aws_srp.py

from warrant.aws_srp import AWSSRP


USERNAME='xxx'
PASSWORD='yyy'
POOL_ID='us-east-1_zzzzz'
CLIENT_ID = '12xxxxxxxxxxxxxxxxxxxxxxx'

aws = AWSSRP(username=USERNAME, password=PASSWORD, pool_id=POOL_ID,
             client_id=CLIENT_ID)
tokens = aws.authenticate_user()
id_token = tokens['AuthenticationResult']['IdToken']
refresh_token = tokens['AuthenticationResult']['RefreshToken']
access_token = tokens['AuthenticationResult']['AccessToken']
token_type = tokens['AuthenticationResult']['TokenType']

注意,该aws_srp模块尚未合并到master分支中.

authenticate_user方法仅支持PASSWORD_VERIFIER挑战.如果您想回应其他挑战,请查看authenticate_user和boto3文档.