To retrieve and decode a JWT token in a Logic App, you can follow these steps:
1. Retrieve the JWT Token: First, you need to obtain the JWT token. This can be done by parsing the headers of an incoming request. If the token is sent in the `Authorization` header, you can extract it using a `Parse JSON` action with a schema that captures the `Authorization` key. Then, create a variable to hold just the token part (e.g., after "Bearer ")[10].
2. Decode the JWT Token: JWT tokens are Base64URL-encoded. You can decode the payload portion of the token using the `split` and `base64ToString` functions in Logic Apps. Split the token by the "." separator to isolate the payload. Then, append "=" to ensure the length is a multiple of 4 for Base64 decoding. Logic Apps will implicitly convert this to a Base64 string, which you can then decode using `base64ToString`[1][3].
3. Parse the Decoded Payload: After decoding the payload, you will have a JSON string. Use another `Parse JSON` action to convert this string into a JSON object that you can work with in your Logic App. You can define a schema for this JSON object based on the expected claims in the JWT token[3].
4. Extract Claims: Once the JSON is parsed, you can extract specific claims (like user ID or email) and use them as needed in your Logic App workflow.
This approach allows you to decode and use JWT tokens directly within Azure Logic Apps without needing to create an Azure Function or use external services for decoding. However, if you need to validate the token (check its signature), you might need to use an external service or an Azure Function with a library capable of JWT validation.
Citations:
[1] https://stackoverflow.com/questions/54257879/how-to-decode-a-jwt-token-in-azure-logic-app
[2] https://www.criipto.com/blog/jwt-validation-guide
[3] https://autosysops.com/blog/parse-jwt-tokens-in-azure-logic-apps
[4] https://hasura.io/blog/best-practices-of-using-jwt-with-graphql
[5] https://www.michev.info/blog/post/2140/decode-jwt-access-and-id-tokens-via-powershell
[6] https://supertokens.com/blog/revoking-access-with-a-jwt-blacklist
[7] https://techcommunity.microsoft.com/blog/azuredevcommunityblog/part-4-secure-your-logic-app-using-api-management-8211-validate-jwt-access-restr/336802
[8] https://docs.azure.cn/en-us/logic-apps/logic-apps-securing-a-logic-app
[9] https://www.mikaelsand.se/2022/06/extracting-values-from-a-jwt-token-in-apim/
[10] https://rakhesh.com/azure/parsing-json-tokens-in-a-logic-app/
[11] https://github.com/auth0/jwt-decode