Caching JWKS from Identity Provider using Azure API management for validating JWT

Question

The code below validates JWT token by downloading JWKS every time it validates each request following this

    <validate-jwt header-name="Authorization" failed-validation-httpcode="401" failed-validation-error-message="Error: expired token or invalid token" require-expiration-time="true" require-scheme="Bearer" require-signed-tokens="true">
        <openid-config url="https://IdentityProvider/oidc/.well-known/openid-configuration" />
        <audiences>
            <audience>aud id</audience>
        </audiences>
    </validate-jwt>

My question is how to cache the JWKS from the example link below to avoid downloading it every time, and without hard-coding the JWKS, since it is rotated regularly.

https://demo.identityserver.io/.well-known/openid-configuration/jwks

https://openid-connect-eu.onelogin.com/oidc/certs

Any code example and links for caching and validate JWT would be appreciated.

Below seems relevant but not a complete example.

https://docs.microsoft.com/en-us/azure/api-management/api-management-sample-cache-by-key

Update

Just to be clear, I want to cache the contents from JWKS of the links above to improve performance.

Answer 1

Checkout the below sample referred from here if that helps !

<policies>
    <inbound>
        <!-- Add your wcf relay address as the base URL below -->
        <set-backend-service base-url="" />
        <!-- verify if there is a relaytoken key stored in cache -->
        <cache-lookup-value key="@("relaytoken")" variable-name="relaytoken" />
        <choose>
            <!-- If there is no key stored in cache -->
            <when condition="@(!context.Variables.ContainsKey("relaytoken"))">
                <set-variable name="resourceUri" value="@(context.Request.Url.ToString())" />
                <!-- Retrieve Shared Access Policy key from  Name Value store -->
                <set-variable name="accessKey" value="{{accessKey}}" />
                <!-- Retrieve Shared Access Policy key name from  Name Value store -->
                <set-variable name="keyName" value="{{accessKeyName}}" />
                <!-- Generate the relaytoken key -->
                <set-variable name="relaytoken" value="@{
                    TimeSpan sinceEpoch = DateTime.UtcNow - new DateTime(1970, 1, 1);
                    string expiry =  Convert.ToString((int)sinceEpoch.TotalSeconds + 3600);
                    string resourceUri = (string)context.Variables["resourceUri"];
                    string stringToSign = Uri.EscapeDataString (resourceUri) + "\n" + expiry;
                    HMACSHA256 hmac = new HMACSHA256(Encoding.UTF8.GetBytes((string)context.Variables["accessKey"]));
                    string signature = Convert.ToBase64String(hmac.ComputeHash(Encoding.UTF8.GetBytes(stringToSign)));
                    string sasToken = String.Format("SharedAccessSignature sr={0}&sig={1}&se={2}&skn={3}",
                    Uri.EscapeDataString(resourceUri), Uri.EscapeDataString(signature), expiry, context.Variables["keyName"]);
                    return sasToken;
                    }" />
                <!-- Store the relaytoken in the cache -->
                <cache-store-value key="relaytoken" value="@((string)context.Variables["relaytoken"])" duration="10" />
            </when>
        </choose>
        <!-- If the operation request uses json format, convert it to XML - Azure Relay expects XML format (based on WCF) -->
        <set-body template="liquid">
            <!-- set your body transformation here -->
        </set-body>
        <!-- Create the ServiceBusAuthorization header using the relaytoken as value -->
        <set-header name="ServiceBusAuthorization" exists-action="override">
            <value>@((string)context.Variables["relaytoken"])</value>
        </set-header>
        <!-- Set the content type to application/xml -->
        <set-header name="Content-Type" exists-action="override">
            <value>application/xml</value>
        </set-header>
        <base />
    </inbound>
    <backend>
        <base />
    </backend>
    <outbound>
    <!-- If the operation responses uses json format, convert it from XML - Azure Relay will return XML format (based on WCF) -->
        <set-body template="liquid">
            <!-- set your body transformation here -->
        </set-body>
        <!-- Set the content type to application/json -->
        <set-header name="Content-Type" exists-action="override">
            <value>application/json</value>
        </set-header>
    </outbound>
    <on-error>
        <base />
    </on-error>
</policies>

Answer 2

Azure API Management service has built-in support for HTTP response caching using the resource URL as the key ( https://github.com/toddkitta/azure-content/blob/master/articles/api-management/api-management-sample-cache-by-key.md ). What you could do is to set the openid-config url as an operation and control caching by yourself. Another approach could be by introducing an own caching service.

Answer 3

APIM will not download open id config for every request. It's downloaded, cached and automatically refreshed periodically, every hour if I recall correctly.