Question

How do I set up a Subject Alternate Name

I am dealing with Amazon AWS and they require that my certificate have a “Subject Alternate Name”. How do I enter that on my self-signed certificate? Can I add it to an existing certificate (.pem)?

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In order to have a Subject Alternate Name (SAN) on an SSL certificate, you must first edit your OpenSSL configuration. On Ubuntu/Debian, that can be found at /etc/ssl/openssl.cnf Find the section of that file with the heading [ v3_ca ], you can add the line with your SAN there:

subjectAltName = www.example.com

If you need to use more than one SAN, you can use this format:

[ v3_req ]
# Snipping the other items that appear here for brevity
subjectAltName = @alt_names

[alt_names]
DNS.1 = mail.example.com
DNS.2 = www.example.com

Find more info on the CAcerts wiki.