401 Unauthorized: What digiRunner Is Really Trying to Tell You

digiRunner Gateway blocking unauthorized API requests

(Figure 1: digiRunner Gateway Interception for Unauthorized Client Access)

In Part 1, we established digiRunner's core design philosophy: clear error feedback. Now, let's dive deep into the most common hurdle: the 401 Unauthorized error.

According to digiRunner's error-handling mechanism, a 401 represents an Authentication Failure. This means the Gateway cannot confirm your identity.

This piece of information is the most critical clue for debugging. As stated in digiRunner's technical documentation: "The Gateway will intercept the request directly and will not forward it to the backend service".

Why this matters: This saves developers a massive amount of time. You can immediately rule out any errors in your backend microservices. The problem is 100% between the client and the digiRunner Gateway.

The Engineer's 401 Playbook: A Scenario-Based Guide

Here are the specific scenarios where you will encounter a 401 error and the strategies to fix them.

Scenario 1: The "Oops" Error (Missing Credentials)

This is the most common and easiest error to fix.

Symptom: You receive a 401 Unauthorized immediately.
Cause: The client failed to include the required credential headers. You might be missing the Authorization: Bearer <token> or X-Api-Key in the HTTP header.
Action: Check your client-side code, Postman settings, or cURL command.

Scenario 2: The "Expired" Error (Token Expiration)

Symptom: You receive a 401 Unauthorized, often with a JSON response describing the error.
Cause: The exp (Expiration Time) claim in the JWT has passed. The Gateway strictly checks this claim during validation.
Deep Dive (Refresh Tokens): If you attempt to use an expired Refresh Token to get a new Access Token, the system will return a 401 with a specific message like "error": "invalid_token" and "error_description": "Refresh token expired".

Recommended Action: This is not a bug; it is a feature. Your client application must be built to handle this. The professional approach is to implement an HTTP interceptor that catches the 401, automatically uses the Refresh Token to get a new Access Token, and retries the original request. The user should only be forced to log in again if the Refresh Token also fails.

digiRunner Gateway automatic refresh token sequence workflow

(Figure 2: Automated Refresh Token Sequence via digiRunner Interceptor)

Scenario 3: The "Tamper" Error (Invalid Signature)

Symptom: You receive a 401 Unauthorized despite the token looking "correct" superficially.
Cause: The JWT's signature (the third part of the token) is invalid. This means the token was either tampered with in transit or signed by a key the Gateway doesn't trust (e.g., using a dev environment key in production).
Recommended Action: This is a serious security alert . digiRunner will intercept and reject such requests immediately. Check your environment configuration (dev keys vs. prod keys) right away.

Scenario 4: The "Impersonation" Error (Bad Credentials)

Symptom: You haven't even received a token yet. You are requesting a token from the /oauth/token endpoint and receive a 401.
Cause: You provided an incorrect client_id or client_secret when requesting the token.
Recommended Action: Check the logs for hints like "The client account or password is incorrect" or "Bad credentials".

Scenario 5: The "Revoked" Error (Manual Revocation)

Symptom: You receive a 401 Unauthorized, even though the token is not expired and the signature is valid.
Cause: The Access Token or Refresh Token has been manually revoked by the resource owner (the user) or an administrator. This happens if a user changes their password or clicks "log out from all devices".
Recommended Action: Treat this signal as a forced re-authentication. The client must prompt the user to log in again.

Conclusion: What a 401 Teaches Us

A 401 is not a single error, but a "category" of failure. By providing clear contextual distinctions, digiRunner saves developers the valuable time they would otherwise spend checking backend logs or guessing the problem's location.

FAQ: Common Issues

Q: What is 401?

A: 401 signifies Authentication Failure by the digiRunner Gateway; identity confirmation failed.

Q: Where is the digiRunner 401 error source??

A: The issue is 100% between the client and the Gateway. You can rule out backend microservices.

Q: How to fix missing credentials?

A: Include the Authorization: Bearer or X-Api-Key in your HTTP header.

Q: How to handle expired JWT tokens professionally?

A: Implement an HTTP interceptor to use a Refresh Token and retry the original request.

Q: What causes the Invalid Signature 401 error?

A: The JWT was tampered with, or signed by an untrusted key (e.g., dev key in prod).

Q: What is the action for a revoked token?

A: Treat this as a forced re-authentication. The client must prompt the user to log in again.

Q: What debugging topic follows 401 Unauthorized?

A: The next topic is the 403 Forbidden error, focusing on authorization nuances and scopes.

Choose your next step

→ Try digiRunner Open Source on GitHub: Master the scenarios, including fixing Missing Credentials, addressing Invalid Signatures, and initiating re-authentication for Revoked Tokens.

→ Technical Documentation Dive Deep: Understand the professional approach for handling Token Expiration (Scenario 2), which requires implementing an HTTP interceptor to use a Refresh Token and automatically retry the original request.

→ Insights & Community: Explore digiRunner’s core design philosophy: providing clear contextual distinctions for 401 errors, thereby saving developers the valuable time they would otherwise spend checking backend logs or guessing the problem's location.

Security relies on precision. digiRunner’s clear error feedback system eliminates guesswork and confirms the problem is strictly at the Gateway level. You have mastered authentication. Now, secure the access.

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