Have you ever tried accessing a website hosted behind Cloudflare from your Google Cloud Platform (GCP) instance, only to be greeted by a cryptic "Access Denied" error message? This frustrating problem can happen due to various reasons, but the good news is it can usually be easily fixed with some targeted troubleshooting.
Why Access Might Be Blocked
There are a few common culprits for getting blocked by Cloudflare when trying to access a site from GCP:
Troubleshooting Steps
Here are some things you can try to regain access:
Check IP Reputation
Use a tool like IPVoid to check if your GCP instance's public IP address has been flagged for abuse. If so, you may need to restart your instance to get a clean IP assigned.
# Restart GCP instance
gcloud compute instances reset [INSTANCE_NAME]Verify Location Access
Some websites block traffic from certain physical locations. Use a geolocation tool like IPLocation to check if your instance's region is being blocked. Consider launching in a different zone if access is limited.
Confirm Not a Bot
Cloudflare may be blocking automated scraping or scripted access attempts. Try manually accessing the site from your instance through curl or browser to verify you are not being flagged as a bot.
# Test site access from command line
curl -I https://www.example.comCheck Cloudflare WAF Rules
The site owner may have set up Web Application Firewall (WAF) rules in Cloudflare that are blocking your instance. Ask them to review their WAF configuration and whitelist your instance's IP if needed.
Use a VPN/Proxy
As a last resort, you can mask your GCP IP and geography by connecting your instance to a VPN service or proxy server. This makes your traffic appear to come from the VPN/proxy provider instead.
Gaining Insights from Errors
While frustrating, "Access Denied" errors often provide clues to the underlying block reason if you look closely.
# Example Cloudflare Block Page
Access Denied
You don't have permission to access "http://www.example.com/" on this server.
Reference #18.adff185.1594934.1c7364bThe reference # provides a unique identifier for the block instance that can be used when troubleshooting with Cloudflare support. The first section gives context on the specific policy triggering it.
Digging into these details can reveal whether it is an IP-based block, bot related, or other firewall policy causing issues.
Preventing Future Access Problems
Once you regain access, it is smart to take steps to prevent ending up blocked again in the future:
With some targeted troubleshooting and preventative measures, you can get Cloudflare to stop wrongly blocking your important GCP instance traffic.