Got it.

It's super stupid.
The key they give to feed the HMAC-SHA256 is actually a base64 string that needs to be decoded.
It's not mentionned in the docs and I missed the constructor of the Signer in Ruby:

# Public: Initialize the Signer.
#
# access_key - The access_key encoded in Base64. Defaults to the one
#�� in the global configuration.
def initialize(access_key=Azure.config.storage_access_key)
�� @access_key = Base64.strict_decode64(access_key)
end

Tests are passing now :)

Thanks for your patience Sven!

On Thu, Jun 19, 2014 at 4:01 PM, Sven Van Caekenberghe <sven@stfx.eu> wrote:

On 19 Jun 2014, at 15:52, Fran��ois Stephany <tulipe.moutarde@gmail.com> wrote:

>
> >
> > You might want to have a look at the code in Zinc-AWS (group AWS in ConfigurationOfZincHTTPComponents), in particular ZnAWSS3Client and ZnAWSS3RequestSignatureTool - it is using similar request signing but does HMAC-SHA1.
> >
> > Thanks! I wasn't aware of the existence of ZnAWS.
> > Actually, i'm currently using the HMAC-SHA256 implementation of the CloudFork.
>
> Is that an all Smalltalk implementation ?
> Because it would be really good to have SHA256 in the image.
>
> Yes it is. The class comment says:
>
> "
> http://csrc.nist.gov/publications/fips/fips180-2/fips180-2withchangenotice.pdf This class represnets the implementation of CFSHA256 as describied above.
> Please direct questions or comments about this implementation to Ron Teitelbaum: Ron@USMedRec.com
> This code was extensively coppied from SHA1 by Luciano Notarfrancesco lnotarfrancesco@yahoo.com
> "
>
> It seems to work for AWS, I wonder what I'm doing wrong here...

You have to be 100% sure that the SHA256, HMAC-SHA256 code works (as opposed to the SHA1, HMAC-SHA1 code) then you absolutely need examples: a known canonical string and keys with a Base64 signature output. Start by making sure you can replicate this in your reference implementation (Ruby, Java, C#) and then start to go to Pharo.

Look *very* carefully at each element of the canonical string, one letter difference, one header, punctuation, whitespace, case, date or time format difference will break the whole thing - that is the point of being a signature.