From the rfc5280 it's a bit unclear to me if the subject name needs to be repeated in the Subject Alternative Name (SAN).

The RFC says "addition" or "in place". So it could be both?  Subject Alternative Name

   These identities may be included
   in addition to or in place of the identity in the subject field of
   the certificate. 

For example, github.com has the following certificate:


CN = github.com
O = GitHub, Inc.
L = San Francisco
S = California
C = US

and Subject Alternative Name:

DNS Name=github.com
DNS Name=www.github.com

If the certificate would use this as Subject Alternative Name:

DNS Name=www.github.com

So without DNS Name=github.com. Would it still work for both domains? (github.com and www.github.com)


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