Creating CSR with multiple Domains With Openssl

Creating a CSR (Certificate Signing Request) with multiple domains using OpenSSL involves generating a private key and a CSR file, which includes the details of the domain(s) to be included in the certificate. The process involves the following steps:

Generate a private key using the openssl command with the following syntax:

openssl genrsa -out domain.key 2048

This generates a private key file named "domain.key" with 2048 bits of encryption.

Create a configuration file (e.g. domain.conf) that contains the details of the domains to be included in the certificate. This file should contain the following details:

[req]

default_bits       = 2048

default_keyfile    = domain.key

distinguished_name = req_distinguished_name

req_extensions     = req_ext

[req_distinguished_name]

countryName             = Country Name (2 letter code)

stateOrProvinceName     = State or Province Name (full name)

localityName            = Locality Name (eg, city)

organizationName        = Organization Name (eg, company)

commonName              = Common Name (e.g. server FQDN or YOUR name)

emailAddress            = Email Address

[req_ext]

subjectAltName          = @alt_names

[alt_names]

DNS.1                  = example.com

DNS.2                  = www.example.com

DNS.3                  = subdomain.example.com

In the example above, "example.com", "www.example.com", and "subdomain.example.com" are included as the alternate domain names.

Generate a CSR file using the openssl command with the following syntax:

openssl req -new -sha256 -key domain.key -out domain.csr -config domain.conf

This generates a CSR file named "domain.csr" that contains the details of the private key and the alternate domain names specified in the configuration file.

Submit the CSR file to a Certificate Authority (CA) to obtain a signed SSL certificate that can be installed on the server.

Overall, this process allows for the creation of a CSR file with multiple domain names that can be used to obtain a signed SSL certificate to secure those domains.