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aws-setup.md

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AWS Setup

Cognito

An outline of steps:

  1. Create a User Pool
  2. Create a Client Application
  3. Create a Custom Domain Name
  4. Create a Federated Identity Pool
    • Set the user pool and client application as Authentication Provider
    • Allow unauthenticated user acces
    • Allow Cognito to create roles for authenticated and unauthenticated users

User Pool

  1. From Cognito, click Manage User Pools, then click Create a User Pool
  2. Provide a name for the pool. (The demo usesapi-auth-demo )
  3. You can Review Defaults or Step through Settings. (These instructions walk through settings.)
  • Set sign-in settings such as use username or email address
  • Set required attributes

  • password policy
  • allow user signup

  • MFA
  • Verification Options
  • IAM Role for sending SMS to users

  • Customize email messages

  • tags

  • specify or create an application client (can also be done later)
  • NOTE: don't check the "Generate client secret" checkbox

  • verify settings, create the pool

App Client Settings

  • Click App client settings in left sidebar
  • enter authenication callback URLs and Signed out URLs

App Clients

If the aws.cognito.signin.user.admin scope is enabled, its permissions are set from General Settings, App clients

Read and write settings, by attribute are specified, for the app client.

NOTE: If aws.cognito.signin.user.admin is enabled, a user could extract session tokens from the browser and use the Cognito API (as the app client would) to read/write attributes. This may or may not be desired, depending on the individual application.

Domain Name

Select a custom subdomain (needs to be unique across AWS) or a custom domain. We will use a subdomain, which is easier to setup. (More on custom domains can be found here.)

Federated Identity Pool

  • From the Cognito main page, click Manage Identty Pools, then click Create new identity pool
  • Under Authentication Providers, enter the User Pool ID and App Client ID created in the earlier steps
  • check Enable access to unauthenticated identities

  • Click Create new role for Unauthenticated Role and Authenticated Role (Doc are here)

Note: We will also explicitly allow unauthenticated users. In this configuration, Cognito will assign authenticated users to one IAM role, and unauthenticated users to another IAM role. It is isn't necessary to assign unauthenticated users to an IAM role. But if you want to have explicit control over unauthenticated user policy, via IAM vs. authenticated users, it can be useful.

API Gateway

Claudia.js will create the API resources, but the following is to create a usage policy for the API, which will be tied to an API key.

Usage Plan

  • From the API Gateway console, click Usage Plans on the left sidebar.

  • Provide a name

  • Optionally set Throttling and Quota

API Key

  • From the API Gateway console, click API Keys on the left sidebar.
  • click Create API key from the Actions menu button
  • specify a name and let the key auto-generate
  • click Save
  • click Add to Usage Plan
  • enter the name of the Usage Plan created earlier

While API keys can used as an authentication mechanism, we will use it for policy enforcement. We will use AWS Cognito for authentication. As noted, the API key enables our throttle policy. We will simply use one API key for all requests - you could create an API key per user (using a Cognito triggers) or whatever key assignment scheme you'd like.

IAM

Many of the IAM roles will be automatically be created by Cognito and Claudia.js. But the authenticated user role needs to be edited to provide access to appropriate resources. (In the demo, this is a single API method.)

The ARN for the API Gateway resources, for the authorized user to acces, is needed.

  • From the API Gateway, go to the API created with Claudia.js
  • Click Resources and then the method to be protected
  • in the Method Request, select the ARN (in yellow below)
  • wildcards can be used to specify multiple methods once the base ARN is known

For the IAM role,

  • From the IAM console, find the authenticated user role
    • If Cognito created it, it will be named Cognito_<pool_name>AuthRole
  • There may be an Invoke_<api> policy in the role. If not create a new policy

Edit the policy's JSON to

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "execute-api:Invoke"
            ],
            "Resource": "arn:aws:execute-api:<ARN FOR API RESOURCE>",
            "Effect": "Allow"
        }
    ]
}

That's all!