they ask for name ,application no and/or UCI number, and may be some other relevant details, I don’t remember exactly, they are reliable. I got my GCMS 2 times from them. If you have any friend or relative in Canada. You can apply GCMS if you are Canadian citizen, pr or present in canada on any status on following website
https://atip-aiprp.apps.gc.ca/atip/welcome.do