Why is Microsoft OAuth2 Timing Out in n8n Behind an NGINX Reverse Proxy?

It looks like n8n is not receiving a timely response from Microsoft's OAuth server, which is causing the connection to time out with an ETIMEDOUT error. In your setup—running behind an NGINX reverse proxy—this can happen if n8n is not correctly recognizing the network topology. Here are some things to check:

1. Reverse Proxy Configuration
   Make sure your NGINX configuration forwards and preserves the original request headers correctly. If n8n sits behind one or more proxies, it’s important to set the appropriate proxy settings.

2. N8N Proxy Environment Variable
   When running n8n behind a reverse proxy, you might need to set the environment variable N8N_PROXY_HOPS to the number of proxy hops between the end client and n8n. This tells n8n how many proxies are in front of it so that it can build correct callback URLs. For example:

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   N8N_PROXY_HOPS=1

   (Adjust the value if you have more proxies.)

3. Network and Firewall Issues
   The error shows that n8n times out while trying to reach an IP (20.190.159.128 on port 443). Verify that your Docker container (or host) isn’t blocked by a firewall or network policy when connecting to that endpoint. Confirm that there isn’t any outgoing traffic blocking or DNS issue causing the delay.

4. NGINX Timeout Settings
   Check NGINX’s timeout settings. If the proxy has too short a timeout for connections to complete the OAuth handshake, the connection might abort before Microsoft’s server responds.

By addressing these potential issues, you should be able to resolve the connection timeout for the Microsoft OAuth flow. Once you ensure that n8n is aware of the proxy hops and network restrictions (if any), the "Connect my account" process should complete without the ETIMEDOUT error.

Below is a summary of what the error indicates and some troubleshooting steps:

What the Error Means

• ETIMEDOUT 20.190.159.128:443:
  This error means the connection attempt from your n8n container to the Microsoft OAuth endpoint timed out. The IP address (20.190.159.128) on port 443 is not responding in time, which usually points to a network connectivity issue rather than a configuration error within n8n itself.

Possible Causes

1. Network or Firewall Restrictions:
   Your Docker container might not be able to make outbound HTTPS calls. This could be due to a firewall rule or network policy blocking access to external endpoints.

2. NGINX or Reverse Proxy Configuration:
   While your reverse proxy handles incoming traffic, check if there are outbound restrictions or if the proxy’s configuration might be indirectly affecting external calls.

3. Docker Network Settings:
   If Docker is configured with custom network settings, ensure that the container has proper access to the internet.

4. Azure/Communication issues:
   Though less likely since you've confirmed connectivity from your server, transient issues or a misconfigured redirect/authorization URL in Azure could also lead to timeouts.

Suggested Troubleshooting Steps

• Test Outbound Connection from the Container:
  Open a shell in your Docker container and run a command like:

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  curl -v https://20.190.159.128

  This will help verify if the container can reach the Microsoft endpoint directly.

• Check Firewall and Network Rules:
  Ensure that your host and any intermediary firewalls/routers allow outbound HTTPS traffic (port 443).

• Review Reverse Proxy Settings:
  Although NGINX is mainly handling incoming requests, double-check its configuration to ensure it isn’t interfering with n8n’s outbound connections.

• Verify OAuth2 Configurations:
  Revisit your OAuth Redirect URL both on Azure and within your n8n credential settings to ensure they match perfectly. Even though the timeout suggests a network issue, it’s worth verifying.

• Restart n8n and/or Docker Container:
  In some cases, simply restarting the service or container can help if it’s a temporary networking hiccup.

Final Note

The error isn’t coming from n8n’s internal processing but rather from an inability to reach the Microsoft OAuth endpoint. Matching these troubleshooting tips with your setup should help pinpoint where the connection is being blocked.