certs

create_server_certificate.sh

create_server_certificate.sh is a script helping with issuing server certificates that can be used to provide TLS on web servers.

It also creates a Certificate Authority (CA) root key and certificate. This CA root certificate can be used to validate the server certificates it generates.

For instance, with curl:

curl --cacert /somewhere/ca-root.crt https://www.example.com/

or with wget:

wget --certificate=/somewhere/ca-root.crt https://www.example.com/

or with the python requests module:

import requests
r = requests.get("https://www.example.com", verify="/somewhere/ca-root.crt")

Usage

Simple domain

Create a server certificate for domain www.example.com:

./create_server_certificate.sh www.example.com

Will produce:

• www.example.com.key
• www.example.com.crt

Multiple domains

Create a server certificate for main domain www.example.com and alternative domains example.com, foo.com and bar.com:

./create_server_certificate.sh www.example.com foo.com bar.com

Will produce:

• www.example.com.key
• www.example.com.crt

Wildcard domain

Create a server certificate for wildcard domain *.example.com:

./create_server_certificate.sh "*.example.com"

Note that you need to use quotes around the domain string or the shell would expand *.

Will produce:

• *.example.com.key
• *.example.com.crt

Again, to prevent your shell from expanding *, use quotes. i.e.: cat "*.example.com.crt".

Such a server certificate would be valid for domains:

• foo.example.com
• bar.example.com

but not for domains:

• example.com
• foo.bar.example.com

Wildcard domain on multiple levels

While you can technically create a server certificate for wildcard domain *.example.com and alternative name *.*.example.com, client implementations generally do not support multiple wildcards in a domain name.

For instance, a python script using urllib3 would fail to validate domain foo.bar.example.com presenting a certificate with name *.*.example.com. It is advised to stay away from producing such certificates.

If you want to give it a try:

./create_server_certificate.sh "*.example.com" "*.*.example.com"

Such a server certificate would be valid for domains:

• foo.example.com
• bar.example.com
• foo.bar.example.com