How to set one path alias as the canonical alias?
Metatg seems to be your answer:

Currently supported meta tags:

Abstract

Author

Canonical URL

Copyright

Description

Dublin Core (sub-module)

Generator

Image source

Keywords

News Keywords

Open Graph Protocol (sub-module)

Original Source

Publisher URL

Robots

Shortlink URL

Title (e.g. Page titles)

Twitter Cards (sub-module)