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Generate ssl certificates with Subject Alt Names

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   =

Additional FQDNs can be added if required:

DNS.1   =
DNS.2   =
DNS.3   =

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: 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.

[ req ]
default_bits = 4096
distinguished_name = req_distinguished_name
req_extensions = req_extensions_section
prompt = yes
[ req_distinguished_name ]
countryName = Country Name (2 letter code)
countryName_min = 2
countryName_max = 2
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
organizationalUnitName = Organizational Unit Name (eg, section)
organizationalUnitName_default = IT
commonName = Common Name (eg, server FQDN or YOUR name)
commonName_max = 64
commonName_default =
emailAddress = Email Address (eg,
emailAddress_max = 64
emailAddress_default =
[ req_extensions_section ]
subjectAltName = @subject_alternative_name_section
[ subject_alternative_name_section ]
DNS.1 =
DNS.2 = *
DNS.3 =
DNS.4 = *
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