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Using JWT Authorizers

caution

AWS supports JWT authorizers for HTTP APIs and not REST APIs on the API Gateway service. For REST APIs follow the Lambda authorizer guide

This guide will work if you are using SuperTokens Session Tokens.

If you implementing an OAuth2 setup, through the Unified Login or the Microservice Authentication features, you will have to manually set the token audience property. Please check the referenced pages for more information.

1) Add the aud claim in the JWT based on the authorizer configuration#

config.mjs

import Session from 'supertokens-node/recipe/session'

export function getBackendConfig() {
return {
framework: "awsLambda",
supertokens: {
connectionURI: "",
apiKey: "",
},
appInfo: {
// learn more about this on https://supertokens.com/docs/session/appinfo
appName: "<YOUR_APP_NAME>",
apiDomain: "<YOUR_API_DOMAIN>",
websiteDomain: "<YOUR_WEBSITE_DOMAIN>",
apiBasePath: "/auth",
websiteBasePath: "/auth",
},
recipeList: [
Session.init({
exposeAccessTokenToFrontendInCookieBasedAuth: true,
override: {
functions: function (originalImplementation) {
return {
...originalImplementation,
createNewSession: async function (input) {
input.accessTokenPayload = {
...input.accessTokenPayload,
/*
* AWS requires JWTs to contain an audience (aud) claim
* The value for this claim should be the same
* as the value you set when creating the
* authorizer
*/
aud: "jwtAuthorizers",
};

return originalImplementation.createNewSession(input);
},
};
}
},
}),
],
isInServerlessEnv: true,
}
}

2) Configure your authorizer#

  • Go to the "Authorizers" tab in the API Gateway configuration and select the "Manage authorizers" tab
  • Click "Create", in the creation screen select "JWT" as the "Authorizer type"
  • Enter a name for your authorizer (You can enter any name for this field)
  • Use $request.header.Authorization for the "Identity source". This means that API requests will contain the JWT as a Bearer token under the request header "Authorization".
  • Use {apiDomain}/{apiGatewayPath}/{apiBasePath} for the "Issuer URL".
  • Set a value for the "Audience" field, this will be the value you expect the JWT to have under the aud claim. In the backend config above the value is set to "jwtAuthorizers"

3) Add the authorizer to your API#

  • In the "Authorization" section select the "Attach authorizers to routes" tab
  • Click on the route you want to add the authorizer to and select the authorizer you created from the dropdown
  • Click "Attach authorizer"
  • Deploy your changes and test your API

4) Check for auth claims of the JWT#

Once the JWT authorizer successfully validates the JWT, the claims of the JWT will be available to your lambda functions via $event.requestContext.authorizer.jwt.claims. You should check for the right authorization access here.

For example, if one of your lambda functions requires that the user's email is verified, then it should check for the jwt payload's st-ev claim value to be {v: true, t:...}, else it should reject the request. Similar checks need to be done to enforce the right user role or if 2FA is completed or not.

This is required because SuperTokens issues JWTs immediately after the user signs up / logs in, regardless of if all the authorisation checks pass or not. Functions exposed by our SDK like verifySession or getSession do these authorisation checks on their own, but since these functions are not used in the this flow, you will have to check them on your own.