Resolved Domain with 100 domains alias: Let's encrypt problem

[Erwan]

Plesk Onyx / Centos
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Hello,
We have a problem with a website on which we have 100 domains alias (since a lot of year).
We want now use "https" with Let's Encrypt.
So we select domain alias to secure (all) and we validate.
After a lot of minutes, we have an error:

"operation too long"

If we gradually add alias domains, we have the same problem from the 20 or 25th domain...

How can we solve this?
Is there a command line to made the opration?

 

[ChristophRo]

I doubt that so many domains will work at all, and there is nothing that Plesk can do about it.

The "certificate alternative name" property of an SSL certificate is limited to 4096 bytes, thus there is an ultimate limit on how many domains you can place within a single cert.
That is also why most official signers (Digicert, Comodo and co.) do no offer SAN certificates for more that 50 domain names.

So yeah, while 100 domains may work if they are very short, that many will easily break the 4kB limit in most cases.

 

[Erwan]

Ok. Thank you.