Create a Self-signed Certificate with a SAN (Subject Alternative Name)

QUESTION

ANSWER

$ openssl version
OpenSSL 1.1.1l  24 Aug 2021

$ find /usr/local -name openssl.cnf
/usr/local/etc/openssl@1.1/openssl.cnf
/usr/local/Cellar/openssl@1.1/1.1.1l_1/.bottle/etc/openssl@1.1/openssl.cnf
/usr/local/Cellar/openssl@1.1/1.1.1l/.bottle/etc/openssl@1.1/openssl.cn
...

[ alternate_names ]

DNS.1        = api.example.com
DNS.2        = www.example.com

$  openssl genrsa -out private.key 2048
Generating RSA private key, 2048 bit long modulus (2 primes)
.....................+++++
........................................................................................+++++
e is 65537 (0x010001)

$ openssl req -new -x509 -key private.key -sha256 -out certificate.pem -days 730 -config ./openssl.cnf
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:
State or Province Name (full name) [Some-State]:NSW
Locality Name (eg, city) []:Sydney
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Example
Organizational Unit Name (eg, section) []:www
Common Name (e.g. server FQDN or YOUR name) []:api
Email Address []:

$ openssl x509 -noout -text -in certificate.pem
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            77:e7:9a:4a:a0:aa:0b:c9:32:0d:36:4e:34:3f:d1:6e:f9:a2:b4:6c
        Signature Algorithm: sha256WithRSAEncryption
        Issuer: C = AU, ST = NSW, L = Sydney, O = Example, OU = www, CN = api
        Validity
            Not Before: Oct 29 01:06:43 2021 GMT
            Not After : Oct 29 01:06:43 2023 GMT
        Subject: C = AU, ST = NSW, L = Sydney, O = Example, OU = www, CN = api
...
            X509v3 Subject Alternative Name:
                DNS:api.example.com, DNS:www.example.com
...

ADDITIONAL INFORMATION

Disclaimer: This article involves products and technologies which do not form part of the MuleSoft product set. Technical assistance for such products is limited to this article.