Apologies for resurrecting an old thread, but I have a real life data point to add.
This Canadian Govt website says your passport need only be valid for the duration of your stay:
http://www.canadainternational.gc.ca...as/FAQ.aspx#a3
I travelled to Canada with 5 months left on my British passport. I was diverted to immigration before leaving the airport. After a bit of tooth sucking, I had a piece of paper stapled into my passport limiting my stay in Canada to a date prior to expiration of my passport (much longer than my planned stay though). The standard passport stamp would have entitled me to stay for 6m, which the border control guys didn't seem comfortable with given my passport's validity.