install-comodo-ssl-cert-for-nginx.md

Setting up a SSL Cert from Comodo

I use Namecheap.com as a registrar, and they resale SSL Certs from a number of other companies, including Comodo.

These are the steps I went through to set up an SSL cert.

Purchase the cert

Prior to purchasing a cert, you need to generate a private key, and a CSR file (Certificate Signing Request). You'll be asked for the content of the CSR file when ordering the certificate.

openssl req -new -newkey rsa:2048 -nodes -keyout example_com.key -out example_com.csr

This gives you two files:

• example_com.key -- your Private key. You'll need this later to configure ngxinx.
• example_com.csr -- Your CSR file.

Now, purchase the certificate, follow the steps on their site, and you should soon get an email with your PositiveSSL Certificate. It contains a zip file with the following:

• Root CA Certificate - AddTrustExternalCARoot.crt
• Intermediate CA Certificate - COMODORSAAddTrustCA.crt
• Intermediate CA Certificate - COMODORSADomainValidationSecureServerCA.crt
• Your PositiveSSL Certificate - www_example_com.crt (or the subdomain you gave them)

Install the Commodo SSL cert

Combine everything for nginx:

1. Combine the above crt files into a bundle (the order matters, here).

cat www_example_com.crt COMODORSADomainValidationSecureServerCA.crt COMODORSAAddTrustCA.crt AddTrustExternalCARoot.crt > ssl-bundle.crt

2. Store the bundle wherever nginx expects to find it.

mkdir -p /etc/nginx/ssl/example_com/
mv ssl-bundle.crt /etc/nginx/ssl/example_com/

3. Ensure your private key is somewhere nginx can read it, as well.

mv example_com.key /etc/nginx/ssl/example_com/

4. Make sure your nginx config points to the right cert file and to the private key you generated earlier.

    server {
        listen 443;

        ssl on;
        ssl_certificate /etc/nginx/ssl/example_com/ssl-bundle.crt;
        ssl_certificate_key /etc/nginx/ssl/example_com/example_com.key;

        # side note: only use TLS since SSLv2 and SSLv3 have had recent vulnerabilities
        ssl_protocols TLSv1 TLSv1.1 TLSv1.2;

        # ...

    }

5. Restart nginx.

Also refer to:

• nginx - Configuring HTTPS servers
• A Poodle proof, bulletproof Nginx SSL configuration
• Certificate Installation: NGINX