Summary

When using the Google Drive API with OAuth authentication in an n8n instance hosted on the Railway environment, the generated redirect URI defaults to the Railway-provided domain (e.g., *.railway.app) instead of a configured custom domain (e.g., n8n.callteksupport.com). This causes a mismatch between the redirect URI and the authorized redirect URI configured in the Google Cloud Console, resulting in a 400 invalid_request error during authentication.

Steps to Reproduce

1. Deploy an n8n cluster on Railway using the provided template.

2. Configure a custom domain (e.g., n8n.callteksupport.com) via DNS.

   • Add a CNAME record pointing the custom domain to the Railway-provided domain (e.g., primary-production-2f4f.up.railway.app).

3. Add the custom domain to the WEBHOOK_URL environment variable in n8n.

4. Configure the Google Drive API and set the authorized redirect URI in the Google Cloud Console to match the custom domain:

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   https://n8n.callteksupport.com/rest/oauth2-credential/callback

5. Attempt to authenticate the Google Drive API in n8n.

Expected Behavior

n8n should generate the redirect URI using the configured custom domain (https://n8n.callteksupport.com/rest/oauth2-credential/callback), allowing successful OAuth authentication.

Actual Behavior

The generated redirect URI defaults to the Railway-provided domain (https://primary-production-2f4f.up.railway.app/rest/oauth2-credential/callback), resulting in a mismatch and a 400 invalid_request error from Google.

Environment

• n8n Version: (e.g., 1.x.x)

• Deployment Environment: Railway

• Custom Domain: n8n.callteksupport.com

• Google Cloud Configuration:

  • Authorized redirect URI: https://n8n.callteksupport.com/rest/oauth2-credential/callback

  • Enabled Scopes: Google Drive API (https://www.googleapis.com/auth/drive)

Logs & Error Details

• Error Message:

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  Error 400: invalid_request Request details: redirect_uri=primary-production-2f4f.up.railway.app/rest/oauth2-credential/callback

• Railway Logs: (Provide relevant snippets showing environment variables and URI generation behavior, if available)

Workarounds Attempted

1. Configured WEBHOOK_URL environment variable to https://n8n.callteksupport.com.

2. Updated Google Cloud Console to include both Railway domain and custom domain in authorized redirect URIs.

3. Verified DNS configuration (CNAME for custom domain points to Railway-generated domain).

Despite these steps, n8n continues to generate the redirect URI using the Railway-provided domain, ignoring the WEBHOOK_URL configuration.

Proposed Solution

• Ensure n8n respects the WEBHOOK_URL environment variable when generating redirect URIs for OAuth authentication.

• Allow explicit configuration of the redirect URI through an environment variable or other settings.

Severity

• Impact: Blocks integration with Google Drive API.

• Priority: High for users relying on OAuth-based integrations with custom domains in Railway deployments.

Additional Context

The issue is specific to OAuth-based integrations in n8n hosted on Railway. Other webhook functionalities may not be affected if the WEBHOOK_URL is properly respected.