Check those SSL certs

I had to update some ssl certs using a cloud service UI and cli tool. I was not sure which SSL certs I needed, so I checked the current config using these nifty command line tools, summerised like so:

echo -n | openssl s_client -connect $QDOMAIN:443  | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > $QDOMAIN.cert
openssl x509 -in $QDOMAIN.cert -text

Download the cert from the HTTPS server

This command uses the openssl tool to contact and negotiate with the SSL server behind the domain It then outputs keys and other information pertaining to the ssl handshake that occured. Using sed we extract the certificate from the output and write it to the file google.cert

echo -n | openssl s_client -connect  | sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' > google.cert

This talks directly to the server and there is not much to get in the way (e.g. browser cache) so is good to rely on as the truth.

Now we have a cert for a domain, we can compare with ssl cert for different domain and see if they are the same, for example

Check the cert

Now we have .cert file we can use the openssl tool to extract easily read information, such as expiry date.

openssl x509 -in google.cert -text