Tools

Install nmap (and fix permissions):

snap install nmap
snap connect nmap:network-control

nmap supports XML output with the option -oX. Install xmllint for nicely formatting XML:

snap install libxml2

Install xml2json for converting the XML to JSON for easier parsing:

sudo apt install npm
sudo sudo npm install -g xml2json

Checking TLS parameters with nmap

Scan all open ports

nmap -v -p 1-65535 localhost

Verify TLS cert on all open ports

nmap -v -p 1-65535 --script ssl-cert localhost

• Ensure each port includes a ssl-cert section, otherwise it's not using TLS.

Check specific ports

Check only the specified ports: nmap -v -p 20385,21995 --script ssl-cert localhost -oX -

Expired certificate

nmap -v --script ssl-cert expired.badssl.com -p 443 -oX -

• Check the notBefore and notAfter fields and verify the current date is in the range.

Insecure SSL/TLS versions

Insecure TLSv1.1 version: nmap -v --script ssl-enum-ciphers tls-v1-1.badssl.com -p 1011 -oX -

• Ensure that only TLSv1.2 (or higher appear in the list, and not e.g. TLSv1.1.

Insecure ciphers

Insecure RC4 cipher: nmap -v --script ssl-enum-ciphers rc4.badssl.com -p 443 -oX -

• Check the ciphers table and ensure all the strength fields are A (and not e.g. C).