How to change the rights to folders and files in ISPManager via API?

Question

ISPmanager

When executing func=file.upload, it uploads a file with root ownership, you need to change it via api, but I didn’t find such a function. Tried file.unixattr and file.attr - it doesn't work through them for some reason.
Here is the code I am using ($loginIsp = "root"):

"https://".$host."/billmgr?authinfo=".$loginBill.":".$passBill."
&func=register&username=".$login."&passwd=".$password."&confirm=".$password."
&email=".$email."&person=".$login."&ptype=pperson&country=182&sok=ok&out=json"

"https://".$host."/billmgr?authinfo=".$login.":".$password."
&func=vhost.order.5&domain=".$domen."&price=".$tarif."&promocode=promo
&elid=&noback=on&period=13&sok=ok&out=json"

"https://".$host."/ispmgr?authinfo=".$loginIsp.":".$passIsp."
&func=user.edit&elid=user".$_REQUEST["item_id"]."&passwd=".$_REQUEST["password"]."&confirm=".$_REQUEST["password"]."
&name=user".$_REQUEST["item_id"]."&disklimit=2000&maillimit=10000&ftplimit=4&
webdomainlimit=4&maildomainlimit=4&baselimit=4&baseuserlimit=4&ssi=on&cgi=on
&phpfcgi=on&phpmod=on&preset=lite-pro&shell=on&sok=ok&out=json"

"https://".$host."/ispmgr?authinfo=".$loginIsp.":".$passIsp."
&func=file.upload&plid=/var/www/user".$_REQUEST["item_id"]."/data/www/".$_REQUEST["domen"]

"https://".$host."/ispmgr?authinfo=".$loginIsp.":".$passIsp."
&func=file.extract&elid=/var/www/".$_REQUEST["login"]."/data/www/".$_REQUEST["domen"]."/archiv.zip&sok=ok&out=json"

Making Curl requests. Empirically, I found that in order for the requests to work, you need to additionally log in to the browser in ispmanager.