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Uncovering CloudFlare

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Common Techniques to Uncover Cloudflare

  • You can use some service that gives you the historical DNS records of the domain. Maybe the web page is running on an IP address used before.

    • Same could be achieve checking historical SSL certificates that could be pointing to the origin IP address.

    • Check also DNS records of other subdomains pointing directly to IPs, as it's possible that other subdomains are pointing to the same server (maybe to offer FTP, mail or any other service).

  • If you find a SSRF inside the web application you can abuse it to obtain the IP address of the server.

  • Search a unique string of the web page in browsers such as shodan (and maybe google and similar?). Maybe you can find an IP address with that content.

Tools to uncover Cloudflare

# You can check if the tool is working with
prips 1.0.0.0/30 | hakoriginfinder -h one.one.one.one

# If you know the company is using AWS you could use the previous tool to search the
## web page inside the EC2 IPs
DOMAIN=something.com
WIDE_REGION=us
for ir in `curl https://ip-ranges.amazonaws.com/ip-ranges.json | jq -r '.prefixes[] | select(.service=="EC2") | select(.region|test("^us")) | .ip_prefix'`; do 
    echo "Checking $ir"
    prips $ir | hakoriginfinder -h "$DOMAIN"
done

Uncovering Cloudflare from Cloud infrastructure

Note that even if this was done for AWS machines, it could be done for any other cloud provider.

For a better description of this process check:

LogoCloudflare bypass - Discover IP addresses of Web servers in AWS | TrickestTrickest
# Find open ports
sudo masscan --max-rate 10000 -p80,443 $(curl -s https://ip-ranges.amazonaws.com/ip-ranges.json | jq -r '.prefixes[] | select(.service=="EC2") | .ip_prefix' | tr '\n' ' ') | grep "open"  > all_open.txt
# Format results
cat all_open.txt | sed 's,.*port \(.*\)/tcp on \(.*\),\2:\1,' | tr -d " " > all_open_formated.txt
# Search actual web pages
httpx -silent -threads 200 -l all_open_formated.txt -random-agent -follow-redirects -json -no-color -o webs.json
# Format web results and remove eternal redirects
cat webs.json | jq -r "select((.failed==false) and (.chain_status_codes | length) < 9) | .url" | sort -u > aws_webs.json

# Search via Host header
httpx -json -no-color -list aws_webs.json -header Host: cloudflare.malwareworld.com -threads 250 -random-agent -follow-redirects -o web_checks.json

Bypassing Cloudflare through Cloudflare

Authenticated Origin Pulls

This mechanism relies on client SSL certificates to authenticate connections between Cloudflare’s reverse-proxy servers and the origin server, which is called mTLS.

Instead of configuring it's own certificate, customers can simple use Cloudflare’s certificate to allow any connection from Cloudflare, regardless of the tenant.

Therefore, an attacker could just set a domain in Cloudflare using Cloudflare's certificate and point it to the victim domain IP address. This way, setting his domain completely unprotected, Cloudflare won't protect the requests sent.

More info here.

Allowlist Cloudflare IP Addresses

This will reject connections that do not originate from Cloudflare’s IP address ranges. This is also vulnerable to the previous setup where an attacker just point his own domain in Cloudflare to the victims IP address and attack it.

More info here.

Bypass Cloudflare for scraping

Cache

Sometimes you just want to bypass Cloudflare to only scrape the web page. There are some options for this:

  • Use Google cache: https://webcache.googleusercontent.com/search?q=cache:https://www.petsathome.com/shop/en/pets/dog

  • Use other cache services such as https://archive.org/web/

Tools

Some tools like the following ones can bypass (or were able to bypass) Cloudflare's protection against scraping:

Cloudflare Solvers

There have been a number of Cloudflare solvers developed:

Fortified Headless Browsers

Use a headless browser that isn't deetcted as an automated browser (you might need to customize it for that). Some options are:

Smart Proxy With Cloudflare Built-In Bypass

Smart proxies proxies are continuously updated by specialized companies, aiming to outmaneuver Cloudflare's security measures (as thats their business).

Som of them are:

For those seeking an optimized solution, the ScrapeOps Proxy Aggregator stands out. This service integrates over 20 proxy providers into a single API, automatically selecting the best and most cost-effective proxy for your target domains, thus offering a superior option for navigating Cloudflare's defenses.

Reverse Engineer Cloudflare Anti-Bot Protection

Reverse engineering Cloudflare's anti-bot measures is a tactic used by smart proxy providers, suitable for extensive web scraping without the high cost of running many headless browsers.

Advantages: This method allows for the creation of an extremely efficient bypass that specifically targets Cloudflare's checks, ideal for large-scale operations.

Disadvantages: The downside is the complexity involved in understanding and deceiving Cloudflare's deliberately obscure anti-bot system, requiring ongoing effort to test different strategies and update the bypass as Cloudflare enhances its protections.

Find more info about how to do this in the original article.

References

Learn AWS hacking from zero to hero with htARTE (HackTricks AWS Red Team Expert)!

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