I looked it up, and you are kinda right in the theory of it, and I was wrong in the practice of it. The practical power lies with the Cabinet.
From Wikipedia:
"A declaration of war by Canada [...] is an exercise of the royal prerogative on the constitutional advice of the ministers of the Crown in Cabinet and does not require the direct approval of the Parliament of Canada, though such can be sought by the government."
I looked it up, and you are kinda right in the theory of it, and I was wrong in the practice of it. The practical power lies with the Cabinet.
From Wikipedia:
"A declaration of war by Canada [...] is an exercise of the royal prerogative on the constitutional advice of the ministers of the Crown in Cabinet and does not require the direct approval of the Parliament of Canada, though such can be sought by the government."
https://en.wikipedia.org/wiki/Declaration_of_war_by_Canada