TLS, CSP, CNAME Probing

1) TLS Probing

Nowadays generally all websites communicate over HTTPS(HyperText Transfer Protocol Secure). In order to use HTTPS, the website owner needs to issue an SSL(Secure Socket Layer) certificate.

This SSL/TLS(Transport Layer Security) certificate contains hostname belonging to the same organization.

Clicking on the "Lock🔒" button in the address bar, you can view the TLS/SSL certificate of any website.

Hackerone.com contain these subdomains in its TLS certificate

For this purpose, we will be using a tool called Cero

Installation:

go install github.com/glebarez/cero@latest

Running:

cero in.search.yahoo.com | sed 's/^*.//' | grep -e "\." | sort -u

2) CSP Probing

In order to defend from the XSS attacks as well as keeping in mind to allow cross-domain resource sharing in websites CSP(Content Security Policies) are used. These CSP headers sometimes contain domains/subdomains from where the content is usually imported.

Hence, these subdomains can be helpful for us. In the below image we can see I extracted domains/subdomains from the CSP header of twitter.com

cat subdomains.txt | httpx -csp-probe -status-code -retries 2 -no-color | anew csp_probed.txt | cut -d ' ' -f1 | unfurl -u domains | anew -q csp_subdomains.txt

3) CNAME Probing

I personally came across 2-3 cases where visiting the CNAME of the website showed me the same website without a firewall. (I personally don't know why this happened)

Since then I probe the CNAME's of the subdomains found.

dnsx -retry 3 -cname -l subdomains.txt