2 Free LetsEncrypt Certificates
2.2 Automatic Certificate Method
3 Alternative Free SSL Certificates
List of Figures
Figure 1: Domain Certificates Administration
Figure 2: Domain Certificate Entry
Figure 3: DNS Domain Certificate Entry
Domain SSL certificates are used for site identity and encryption, so site visitors and service users can be certain the site is genuine and communications are secure.
Domain Names in SSL certificates can be specified as a list of valid domains (example.com, www.example.com, mail.example.com, etc.). The domain list (and therefore certificate) may become quite large for sites with many services addressed as "service"."example.com". Another way of specifying valid domains in certificates is using a wildcard ("*") prefix to specify certificate domain names. The certificate will be valid for "*.example.com where" "*" can be "www", "mail", "iot", etc. (any prefix to base domain name).
Certificates must be created for www.yourdomain and yourdomain (both in same certificate file). This handles the case of the website being addressed as www.yourdomain or yourdomain. In general, domain names in certificates must exactly match the URL used to address the site or be wildcard certificates. Otherwise, clients will consider your site insecure and either refuse to connect or the browser will ask the user for a security exception.
There are three types of SSL certificates, differentiated by degree of trust checking that the certificate issuer has performed. GlobalSign provides an overview of SSL certificate types:
The type of SSL certificate required depends on the degree of trust you wish your clients to have. If your site is an e-commerce or medical site and you collect sensitive information, personal data such as passwords and credit card numbers, an Extended Validation (EV) certificate is required. This requirement can be omitted if you use a third party payment processor (with EV certificates) such as PayPal, Visa or Mastercard for e-commerce.
Free SSL certificates provide Domain Validation (DV) and only assure site clients that their communications are secure. They are adequate for all sites, including ecommerce, if a third party payment processor is used.
LetsEncrypt is a free, automated and open certificate authority supported by many leading internet companies concerned regarding the negative effects of high cost and complexity of commercial SSL certificates. They have done an excellent job, to the dismay of high-cost commercial SSL certificate providers.
LetsEncrypt certificates are valid for three months. They must be renewed every three months whether issued manually or automatically.
If your domain is a subdomain of a DNS provider and your DNS provider is not on the "Public Suffix List", you may have to create your SSL certificates manually. Further information regarding the "Public Suffix List" and why DNS providers need to be and how to get on the "list" is available here. Automatic creation / updates of LetsEncrypt SSL certificates may fail due to "rate limiting" for domains from DNS providers not on the "list". The options are to choose a DNS provider from the list or be prepared for rate limiting failures and retries (until success) using automatic certificate updates.
SSL For Free has a very easy to use webpage for creating LetsEncrypt SSL certificates. Go to their site, click "Advanced Options" for instructions regarding how to enter multiple domains. Use the following procedure:
This method works for unique domain names (yoursite.com, etc) and subdomains of DNS providers who may or may not be on the "Public Suffix List" (described in previous section). Using this method, certificates are created and renewed automatically.
SecureOffice offers a custom application called "luci-app-nginx-certificates" which automatically requests and updates LetsEncrypt certificates. To install it, enter "opkg update; opkg install luci-app-nginx-certificates" at a SecureOffice command prompt.
After installing luci-app-nginx-certificates, using a browser on your LAN, access the SecureOffice / OpenWrt web GUI and navigate to "Services->Domain Certificates". You will see the certificate administration page, as shown below:
Figure 1: Domain Certificates Administration
If "Domain Certificates" does not appear under the "Services" menu, the SecureOffice web server cache must be cleared and restarted. Enter "rm -rf /tmp/luci-*; /etc/init.d/nginx restart" at a command prompt and reload the page.
Change the email address (Global Configuration) to the email address that LetsEncrypt certificate expiry notices should go to. If left blank, LetsEncrypt will not send notices.
Delete the default domain entry by pressing "Delete" (Red button on right under "Certificates").
Enter a descriptive name for your new domain section to the left of the "Add" button. The section name can contain letters, numbers and underscores. It is suggested to use your primary domain with underscores, for example "my_domain_com". Press the "Add" button. A new section named "my_domain_com" will be created.
Note: If creating certificates for Sme-Server, be aware that Sme-Server allows specification of only one certificate and key files. This means that if Sme-Server is hosting multiple virtual domains, one certificate including all hosted domains must be created.
Fill in the following fields:
Once the domains and Key Size are entered, the new domain entries will appear as below:
Figure 2: Domain Certificate Entry
SecureOffice supports domain validation using local (HTTP-01) or DNS (DNS-01) LetsEncrypt challenges.
You will see your updated configuration, as shown below:
Figure 3:DNS Domain Certificate Entry
Ensure "Test" and "Debug" are selected. Press "Update". A "Command Results" text area will appear, displaying status, any error messages and pass / fail status. Fix any errors before proceeding (may require internet search).
Uncheck "Test", press "Update" again. A "Command Results" text area will appear, displaying status, any error messages and pass / fail status. Fix any errors before proceeding (may require internet search).
One error to watch out for is "Too Many Certificates Issued" which is an indication you are using a subdomain of a DNS provider not on the "Public Suffix List", meaning that you should retry (or, allow automatic reties to proceed until success), or an alternate method of acquiring SSL certificates or a LetsEncrypt compatible DNS provider must be chosen. While you are at it, send a support request to the DNS provider requesting they get on the "Public Suffix List".
After real certificates have been successfully created, check "Auto Update", uncheck "Debug", then "Save & Apply" to have your certificates auto renew and never have to deal with expired SSL certificates and costs again. "Auto Update" schedules a weekly task every Sunday at 11:30 PM which checks for certificate expiry and updates them if necessary.
Certificates can be viewed (and copied) by pressing "Show Certs".
There are many providers of free SSL certificates which can be found by an internet search. Follow their instructions to acquire certificates.
Be aware that all free SSL certificate providers (except for LetsEncrypt) require manual certificate renewal and expire quickly, with a maximum validity of three months.
Do not use free certificates from WoSign or StartCom, they have lost trust by major browser manufacturers and will not work except for older browsers.
It is also possible to use free self-signed SSL certificates (search internet for instructions) with the disadvantage that the root certificate authority (CA) file must be distributed and installed on all clients (PC's , tablets, phones). This may be useful for the truly paranoid, who do not trust third party certificate providers with their decryption keys and wish to form a private network of trust.
Alternative SSL certificates must be copied to SecureOffice directory "/etc/ssl/domains". The certificate file must be linked to "/etc/ssl/domains/domain.crt" ("ln -sf <certificate file> /etc/ssl/domains/domain.crt"). The key file must be linked to "/etc/ssl/domains/domain.key" ("ln -sf <certificate file> /etc/ssl/domains/domain.key"). This is done automatically for automatic certificate updates. Certificate names and location are crucial for Nginx and other SecureOffice applications.
There are many providers of commercial (paid) SSL certificates which can be found by an internet search. Follow their instructions to acquire certificates.
Commercial SSL certificates must be copied to SecureOffice directory "/etc/ssl/domains". The certificate file must be linked to "/etc/ssl/domains/domain.crt" ("ln -sf <certificate file> /etc/ssl/domains/domain.crt"). The key file must be linked to "/etc/ssl/domains/domain.key" ("ln -sf <certificate file> /etc/ssl/domains/domain.key"). This is done automatically for automatic certificate updates. Certificate names and location are crucial for Nginx and other SecureOffice applications.