Generate ssl certificates with Subject Alt Names

SSL-certs-OSX.md

Generate ssl certificates with Subject Alt Names on OSX

Open ssl.conf in a text editor.

Edit the domain(s) listed under the [alt_names] section so that they match the local domain name you want to use for your project, e.g.

DNS.1   = my-project.dev

Additional FQDNs can be added if required:

DNS.1   = my-project.dev
DNS.2   = www.my-project.dev
DNS.3   = fr.my-project.dev

Create a directory for your project, e.g. my_project and save ssl.conf inside it.

Open Terminal and navigate to 'my_project':

cd my_project

Generate a private key:

openssl genrsa -out private.key 4096

Generate a Certificate Signing Request

openssl req -new -sha256 \
    -out private.csr \
    -key private.key \
    -config ssl.conf 

(You will be asked a series of questions about your certificate. Answer however you like, but for 'Common name' enter the name of your project, e.g. my_project)

Now check the CSR:

openssl req -text -noout -in private.csr

You should see this:

X509v3 Subject Alternative Name: DNS:my-project.site and Signature Algorithm: sha256WithRSAEncryption

Generate the certificate

openssl x509 -req \
    -sha256 \
    -days 3650 \
    -in private.csr \
    -signkey private.key \
    -out private.crt \
    -extensions req_ext \
    -extfile ssl.conf

Add the certificate to keychain and trust it:

sudo security add-trusted-cert -d -r trustRoot -k /Library/Keychains/System.keychain private.crt

(Alternatively, double click on the certificate file private.crt to open Keychain Access. Your project name my_project will be listed under the login keychain. Double click it and select 'Always trust' under the 'Trust' section.)

If you are using MAMP Pro, add (or edit) a host with the server name you listed under the [alt_names] section of your ssl.conf. On the SSL tab select the Certificate file and Certificate key that you just generated.

Save changes and restart Apache.

ssl.conf

[ req ]
default_bits       = 4096
distinguished_name = req_distinguished_name
req_extensions     = req_ext

[ req_distinguished_name ]
countryName                 = Country Name (2 letter code)
countryName_default         = GB
stateOrProvinceName         = State or Province Name (full name)
stateOrProvinceName_default = England
localityName                = Locality Name (eg, city)
localityName_default        = Brighton
organizationName            = Organization Name (eg, company)
organizationName_default    = Hallmarkdesign
commonName                  = Common Name (e.g. server FQDN or YOUR name)
commonName_max              = 64
commonName_default          = localhost

[ req_ext ]
subjectAltName = @alt_names

[alt_names]
DNS.1   = your-website.dev
DNS.2   = another-website.dev

commonName が deprecated なので使うにしても alt_names にも同じものを含めたほうが良い。
commonName が見られない実装も存在するので。