OpenSSL certificate with subjectAltName one-liner

To create a SelfSigned OpenSSL certificate on one line which contains subjectAltName(s) you must use -extensions and -config as follows.

Looking at the output of x509 you should be able to see X509v3 extensions indicating our success.

I came up with this solution by piecing together man pages and random google result. I was surprised at how many incomplete and inaccurate answers were out there. What may have been more surprising was the complete lack of a full intact solution.

Some examples simply output csrs or require creating larger portions of openssl.cnf. The worst were examples which appended subjectAltName to the subject. They look like they are going to work but then don't.

Inspiration for my approach came from this nearly complete answer at StackExchange: Provide subjectAltName to openssl directly on command line. Buried near the bottom is a partial example (which i originally missed) which indicates -extensions rather than -reqexts. This is rather an important detail considering we are trying to make a certificate not a csr.

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