How to force ssl and www for a subdomain as an independent domain?

Question

I have own the example.tld .
I want to force SSL and https for root-domain and all of its subdomains.
I have used below code in .htaccess file of root-domain:

RewriteEngine On
RewriteCond %{HTTPS} off [OR]
RewriteCond %{HTTP_HOST} !^www\.example\.tld$ [NC]
RewriteRule ^(.*)$ https://www.example.tld/$1 [L,R=301]

It looks work perfectly for root-domain.
But, for subdomains like as blog.example.tld , I have used different suggestions, such as:

RewriteCond %{HTTP_HOST} ^blog\.example.\tld$ [NC]
RewriteRule ^ https://www.%{HTTP_HOST}%{REQUEST_URI} [R=301,L,NE]

But, none of them works properly, and they will redirect to ssl www version of root-domain, instead of ssl www version of subdomain.
What should I do?

Answer 1

Finally, I have found the problem.
Problem had caused by host settings.

Due to some issues, I had to define subdomain as an independent domain in the host. This raised issues with Redirects. Because, instead of subdomain, the main domain was responding to Redirection commands.

To solve this problem, I've transferred subdomain to another host, so Redirection commands for subdomain was replied from new host containing subdomain.

In this new situation, the following simple command forces ssl and www for subdomain:

RewriteEngine On
RewriteCond %{HTTP_HOST} !^www\.sub.example\.tld$ [NC]
RewriteRule ^ https://www.%{HTTP_HOST}%{REQUEST_URI} [R=301,L]

RewriteCond %{HTTPS} off
RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [R=301,L]

I hope this experience will be useful for others.

Answer 2

But, none of them works properly, and they will redirect to ssl www version of root-domain, instead of ssl www version of subdomain.

(I'm assuming all your subdomains map to the same area of the filesystem.)

It sounds like you may have put the directives in the wrong order. If you placed the subdomain redirect after the root-domain redirect then it will never get processed and the root-domain redirect will catch all subdomain requests, and redirect the subdomain back to the root-domain, since the RewriteCond directive is checking whether the requested domain is not www.example.tld - this will also match the subdomain.

However, if you want to always enforce the www subdomain (even for your subdomains) then your directive(s) can be "simplified" into a single rule. For example:

RewriteEngine On

RewriteCond %{HTTPS} off [OR]
RewriteCond %{HTTP_HOST} !^www\.
RewriteCond %{HTTP_HOST} ^(?:www\.)?(.+)\.?$ [NC]
RewriteRule ^ https://www.%1%{REQUEST_URI} [R=301,L]

This matches any request that is either HTTP or does not start www. and redirects to HTTPS, prefixing the www subdomain (if necessary). The 3rd RewriteCond directive is necessary to capture the requested hostname, less any www. prefix (if any). The %1 in the substitution is a backreference to the hostname, less any www. prefix.

This naturally affects all domains on the account (if you have more than one).

UPDATE: I've just seen your answer, so I'm not sure whether this will be relevant now or not?