Tpl/crypto: add HMAC support

feature
1

Hello, I am a big fan of Hugo and I am using it for my personal website https://edouard.paris and I am happy with it :slight_smile: I want to use Hugo for more projects using external APIs and here is a proposal feature I would like to see implemented (by me or any awesome hugo developer).

I want to use a image resizer engine https://github.com/thoas/picfit. Images are resized dynamically on the first request and then cached. For security an hmac is required. An HMAC is a specific type of message authentication code (MAC) involving a cryptographic hash function and a secret cryptographic key.

<img src="http://myengine.com/display?w=100&h=100&path=path/to/file.png&sig=<hmac>

The new feature would be a new template function hmac with 3 args:

  • The hash type (string): md5, sha256
  • The message (string)
  • The key (string)

Usage:

{{ $key := getenv "KEY"}}
{{ hmac "sha256" "hello, gohugo" $key }}

Please, tell me what do you think of this idea and if I should create a PR.
Thank you

2

Can you please clarify what you mean here?

Hugo is an “open-source static site generators”, content prepared by Hugo for publishing has no idea of neither first request nor second request.

3

Images are resized dynamically on the first request and then cached.

Picfit will store and resize images and serve them through a http server.
Hugo will not make any http request. It will juste generate an html page with link to images hosted by my picfit instance.

<img src="https://my-picfit-instance.com/hello.png?w=100&h=100&sig=1239786788999923472"

In order to forbid unknown clients to use the resize engine, an hmac is needed in the url.
I use picfit as example but other services use hmac like cloudimage docs

4

Seems like a reasonable request. Post this proposal to Github. I notice that you’re missing sha1 in the list of hash functions. hmac should support all hash functions in the tpl/crypto package. :+1:

2 Likes
5

Thank you, I will post here the github issue once created

6

Please do.