dns_cpanel: resolve the most specific zone in _get_root

With both domain.tld and sub.domain.tld zones on the account, the first
endswith hit could pick the parent zone while cPanel stores the record
in the most specific one, so the cleanup never found the record and
left an orphaned _acme-challenge TXT entry. Pick the longest matching
zone with an exact literal suffix match (_endswith treats the needle as
a regex, letting xdomain.tld wrongly match zone domain.tld).

https://github.com/acmesh-official/acme.sh/issues/6807

dnsapi/dns_cpanel.sh

@@ -38,7 +38,7 @@ dns_cpanel_add() {
   fi
   # adding entry
   _info "Adding the entry"
-  stripped_fulldomain=$(echo "$fulldomain" | sed "s/.$_domain//")
+  stripped_fulldomain="${fulldomain%.$_domain}"
   _debug "Adding $stripped_fulldomain to $_domain zone"
   _myget "json-api/cpanel?cpanel_jsonapi_apiversion=2&cpanel_jsonapi_module=ZoneEdit&cpanel_jsonapi_func=add_zone_record&domain=$_domain&name=$stripped_fulldomain&type=TXT&txtdata=$txtvalue&ttl=1"
   if _successful_update; then return 0; fi
@@ -128,13 +128,27 @@ _get_root() {
     _err "Primary domain list not found!"
     return 1
   fi
-  for _domain in $_domains; do
-    _debug "Checking if $fulldomain ends with $_domain"
-    if (_endswith "$fulldomain" "$_domain"); then
-      _debug "Root domain: $_domain"
-      return 0
-    fi
+  # Pick the LONGEST matching zone, dot-anchored: with both domain.tld and
+  # sub.domain.tld zones on the account, cPanel stores the record in the
+  # most specific zone, so add and rm must both resolve to that one.
+  _domain=""
+  for d in $_domains; do
+    _debug "Checking if $fulldomain ends with $d"
+    # case with quoted patterns gives an exact literal suffix match;
+    # _endswith treats the needle as a regex, so its dots would let
+    # xdomain.tld wrongly match zone domain.tld
+    case "$fulldomain" in
+    "$d" | *".$d")
+      if [ "${#d}" -gt "${#_domain}" ]; then
+        _domain="$d"
+      fi
+      ;;
+    esac
   done
+  if [ -n "$_domain" ]; then
+    _debug "Root domain: $_domain"
+    return 0
+  fi
   return 1
 }