Lately, I’ve explored creating my own CSRs for use with Let’s Encrypt, so I can control the common name and subject names. I’m neurotic enough that I can’t bear to let Let’s Encrypt decide.
Including additional domains, a technique known as Subject Alternatives Names or
subjectAltName (SAN), requires a configuration file to pass the relevant arguments to OpenSSL.
Fill in the above with relevant details and save it as
example.com.conf. Then, run OpenSSL using this configuration file:
openssl req -new -config example.com.conf -keyout example.com.key -out example.com.csr
Confirm the CSR using this command:
openssl req -text -noout -verify -in example.com.csr
The preceding is contingent on your OpenSSL configuration enabling the SAN extensions (
v3_req) for its
req commands, in addition to the
/etc/ssl/openssl.cnf, you may need to uncomment this line:
# req_extensions = v3_req # The extensions to add to a certificate request