Firebase Storage CORS Issue -

i need create base64string images stored in firebase storage bucket. when try convert image using canvas, getting cors issue.

i've found this: firebase storage , access-control-allow-origin

so, i've tried set cors bucket using command:

gsutil cors set cors.json gs://mybucket4f-8a2.appspot.com 

where file cors.json is:

[{"origin": ["*"],"responseheader": ["content-type"],"method": ["get", "head"],"maxageseconds": 3600}] 

then getting error:

accessdeniedexception: 403 caller not have storage.buckets.get access bucket gs://mybucket4f-8a2.appspot.com 

and logged right user using firebase login.

any help, please?