cloudflare-ip-filter 0.1.0

Flask middleware to restrict access to Cloudflare IP ranges

Cloudflare IP Restriction Middleware for Flask

This is a simple Flask middleware module that restricts access to your Flask application only to requests coming from Cloudflare's official IPv4 ranges.

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Features

• Automatically fetches the current list of Cloudflare IPv4 ranges from Cloudflare's API.
• Checks incoming request IPs against the Cloudflare IP ranges.
• Blocks any request from IPs outside Cloudflare's ranges with HTTP 403 Forbidden.
• Logs allowed and blocked requests in color-coded terminal output using colorama.
• Uses only the standard request.remote_addr for IP checking (does not rely on X-Forwarded-For for filtering, but logs the real IP if present).

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Requirements

• Python 3.7+
• Flask
• requests
• colorama

Install dependencies with:

pip install flask requests colorama

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Usage

1. Import and call fetch_cloudflare_ips() once at app startup to load IP ranges:

from utils.ip_filter import fetch_cloudflare_ips, restrict_to_cloudflare

app = Flask(__name__)
fetch_cloudflare_ips()

2. Add restrict_to_cloudflare as a before-request hook to block unauthorized IPs:

@app.before_request
def check_ip():
    restrict_to_cloudflare()

3. Your app will now only accept requests coming through Cloudflare's IPv4 proxies.

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How it works

• The module fetches Cloudflare's current IPv4 CIDR blocks from their API.
• Every incoming request's IP (request.remote_addr) is checked if it belongs to any of those CIDRs.
• If yes, access is allowed and the real client IP (from X-Forwarded-For header if present) is logged in green.
• Otherwise, the request is aborted with HTTP 403, and the blocked IP is logged in red.

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Notes

• This module does not handle IPv6 addresses.
• It assumes your Flask app is running behind Cloudflare proxy.
• The X-Forwarded-For header is only used for logging purposes, not for access control.
• You may want to run fetch_cloudflare_ips() periodically (e.g. daily) to keep IP ranges up to date.

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Example output

Cloudflare IP ranges loaded successfully.
✅ Allowed access. Real IP: 203.0.113.45
⛔️ Blocked IP access: 198.51.100.23

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License

MIT License

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Feel free to contribute or ask questions!