I want to create/calculate a SECRET_HASH for AWS Cognito using boto3 and python. This will be incorporated in to my fork of warrant.
I configured my cognito app client to use an app client secret. However, this broke the following code.
def renew_access_token(self):
"""
Sets a new access token on the User using the refresh token.
NOTE:
Does not work if "App client secret" is enabled. 'SECRET_HASH' is needed in AuthParameters.
'SECRET_HASH' requires HMAC calculations.
Does not work if "Device Tracking" is turned on.
https://stackoverflow.com/a/40875783/1783439
'DEVICE_KEY' is needed in AuthParameters. See AuthParameters section.
https://docs.aws.amazon.com/cognito-user-identity-pools/latest/APIReference/API_InitiateAuth.html
"""
refresh_response = self.client.initiate_auth(
ClientId=self.client_id,
AuthFlow='REFRESH_TOKEN',
AuthParameters={
'REFRESH_TOKEN': self.refresh_token
# 'SECRET_HASH': How to generate this?
},
)
self._set_attributes(
refresh_response,
{
'access_token': refresh_response['AuthenticationResult']['AccessToken'],
'id_token': refresh_response['AuthenticationResult']['IdToken'],
'token_type': refresh_response['AuthenticationResult']['TokenType']
}
)
When I run this I receive the following exception:
botocore.errorfactory.NotAuthorizedException:
An error occurred (NotAuthorizedException) when calling the InitiateAuth operation:
Unable to verify secret hash for client <client id echoed here>.
This answer informed me that a SECRET_HASH is required to use the cognito client secret.
The aws API reference docs AuthParameters section states the following:
For REFRESH_TOKEN_AUTH/REFRESH_TOKEN: USERNAME (required), SECRET_HASH (required if the app client is configured with a client secret), REFRESH_TOKEN (required), DEVICE_KEY
The boto3 docs state that a SECRET_HASH is
A keyed-hash message authentication code (HMAC) calculated using the secret key of a user pool client and username plus the client ID in the message.
The docs explain what is needed, but not how to achieve this.
The below get_secret_hash method is a solution that I wrote in Python for a Cognito User Pool implementation, with example usage:
import boto3
import botocore
import hmac
import hashlib
import base64
class Cognito:
client_id = app.config.get('AWS_CLIENT_ID')
user_pool_id = app.config.get('AWS_USER_POOL_ID')
identity_pool_id = app.config.get('AWS_IDENTITY_POOL_ID')
client_secret = app.config.get('AWS_APP_CLIENT_SECRET')
# Public Keys used to verify tokens returned by Cognito:
# http://docs.aws.amazon.com/cognito/latest/developerguide/amazon-cognito-user-pools-using-tokens-with-identity-providers.html#amazon-cognito-identity-user-pools-using-id-and-access-tokens-in-web-api
id_token_public_key = app.config.get('JWT_ID_TOKEN_PUB_KEY')
access_token_public_key = app.config.get('JWT_ACCESS_TOKEN_PUB_KEY')
def __get_client(self):
return boto3.client('cognito-idp')
def get_secret_hash(self, username):
# A keyed-hash message authentication code (HMAC) calculated using
# the secret key of a user pool client and username plus the client
# ID in the message.
message = username + self.client_id
dig = hmac.new(self.client_secret, msg=message.encode('UTF-8'),
digestmod=hashlib.sha256).digest()
return base64.b64encode(dig).decode()
# REQUIRES that `ADMIN_NO_SRP_AUTH` be enabled on Client App for User Pool
def login_user(self, username_or_alias, password):
try:
return self.__get_client().admin_initiate_auth(
UserPoolId=self.user_pool_id,
ClientId=self.client_id,
AuthFlow='ADMIN_NO_SRP_AUTH',
AuthParameters={
'USERNAME': username_or_alias,
'PASSWORD': password,
'SECRET_HASH': self.get_secret_hash(username_or_alias)
}
)
except botocore.exceptions.ClientError as e:
return e.response