curl -i -X PUT "https://api.box.com/2.0/web_links/32423234?fields=shared_link" \
     -H "authorization: Bearer <ACCESS_TOKEN>" \
     -d '{
       "shared_link": {
         "access": "open",
         "password": "mypassword",
         "unshared_at": "2012-12-12T10:53:43-08:00",
         "permissions": {
           "can_download": false
         }
       }
     }'

{
  "id": "12345",
  "type": "web_link",
  "etag": "1",
  "shared_link": {
    "url": "https://app.box.com/s/kwio6b4ovt1264rnfbyqo1",
    "download_url": "https://app.box.com/shared/static/kwio6b4ovt1264rnfbyqo1.pdf",
    "vanity_url": null,
    "vanity_name": null,
    "effective_access": "open",
    "effective_permission": "can_download",
    "is_password_enabled": false,
    "unshared_at": "2020-09-21T10:34:41-07:00",
    "download_count": 0,
    "preview_count": 0,
    "access": "open",
    "permissions": {
      "can_preview": true,
      "can_download": true,
      "can_edit": false
    }
  }
}