I use Firebase Storage to put images as image space, and then link to my blog, for example:

I checked "https://firebase.google.com/support/guides/security-checklist" it is mentioned
rules_version = '2';
service firebase.storage {
match /b/{bucket}/o {
match /{allPaths=**} {
allow read, write: if false;
}
}
}
But it doesn't seem to mention how to restrict the domain, for example: the image can only be read in example1.com, not in example2.com