[squeak-dev] [ANN] ModifierKeysMorph & WebClientOAuth2 (Zinc-SSO port)

Tim Johnson digit at sonic.net
Sat Jun 13 17:40:12 UTC 2020

> On Jun 11, 2020, at 6:39 PM, Levente Uzonyi <leves at caesar.elte.hu> wrote:
>> It is useful for SSO.  But for automated workflows, where human intervention is undesired, there is another type of OAuth2 which may be called "server to server" or apparently "two-legged OAuth":
>> https://developers.google.com/identity/protocols/oauth2/service-account <https://developers.google.com/identity/protocols/oauth2/service-account>
>> I tried and failed to implement this last year.  Where I failed was in computing the JSON Web Signature (JWS).  I could generate JWTs successfully*, but JWSs for Google require "SHA256withRSA (also known as
>> RSASSA-PKCS1-V1_5-SIGN with the SHA-256 hash function)" which requires one very specific algorithm missing from SqueakSSL and which I simply could not engineer on my own at the time (or perhaps ever — I might just not be
>> smart enough ;) ).  I was able to get as far as crafting the JSON in Squeak and then signing using Python's implementation of the algorithm and it would work.
>> If we could get server-to-server OAuth2 using WebClient, that would also allow us to, say, connect to Google Drive directly from Squeak, or be a client of Google Cloud Platform / Compute Engine, etc.  I think that would be
>> very cool.
>> Sadly, I seem to recall this type of OAuth (and thus this algorithm) would also be necessary for GitHub/GitLab.
> The Cryptography package seems to have this stuff implemented, though I haven't verified the results. Here's how to use it:
> Let's say privateKey is an RSAPrivateKey with your private key (See class side methods and RSAPrivateKeyFileReader how to initialize it) and message is your serialized json to sign. Then
> 	privateKey v15SignMessageHash: (HashFunction newSHA256 digestInfoAsn1DerEncodingFromMessage: message)
> should return the signature.

Thank you Levente.  When I mentioned algorithms I was hoping you might respond.  :) 

I found my old JWT code from last year on GitHub:  https://github.com/tcj/beaufort <https://github.com/tcj/beaufort>      (Oh no, it contains an old email address of mine in one of its tests...)

I loaded Cryptography into an image so I could run my tests again, and noticed that the Cryptography package has seen a lot of work this year.  Thanks for that.

So:  the tests I wrote last year (with a small change) pass now.  This could be very good news and may be worth further investigation.  Thank you again!  I will update my tests (& remove my old email address...?) and upload a new version of this package.

I am reminded that the issue I'd encountered last year was that HS256 could work, but RS256 could not.  Now, unit tests are passing for both.  (My BfJWTRFCTest>>#testConversion is not passing so I'll need to look into that.)

Here is the gist of my JWT signing code:

BfJWT>>#signedWith: aKey
	| headerAndClaims |
	self secret: aKey.
	headerAndClaims := self headerAndClaims.
	^ '{1}.{2}' format: { headerAndClaims . self signatureFrom: headerAndClaims }

... #signatureFrom: is implemented differently for HS256 versus RS256 subclasses of BfJWT.  My RS256 encoding was like this:

BfRS256 signatureFrom: aString
	| signedMessage hashed privateKey |
	privateKey := (Pkcs12PrivateKeyFileReader fromFile: 'timj-project-mar-2019-a94d67a8d0c8.p12') asPrivateKey.
	signedMessage := privateKey signMessage: aString.
	hashed := SHA256 new hashStream: signedMessage readStream.
	^ hashed base64UrlEncoded

A year ago, I could have described how & why it wasn't working... but that information has left my brain now.

For what it's worth, Norbert Hartl's JSONWebToken also lacks support for this RS256 encoding format.

https://github.com/noha/JSONWebToken/commit/4a4d20eaa6e84e2676a577f74bc6e24c1ead0047 <https://github.com/noha/JSONWebToken/commit/4a4d20eaa6e84e2676a577f74bc6e24c1ead0047>

It seems to be a common issue around the internet that people find RS256 very difficult.

Thanks again,

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.squeakfoundation.org/pipermail/squeak-dev/attachments/20200613/b6b1c1f9/attachment.html>

More information about the Squeak-dev mailing list