DefaultPKCEProvider challenge rejected about google-auth-library-java

[sqrrrl]

Looks like the issue is padding. PKCE spec calls for having the padding stripped (https://www.rfc-editor.org/rfc/rfc7636#appendix-A) whereas the URL generated with the DefaultPkCEProvider has padding included (the trailing %3D in the challenge):

https://accounts.google.com/o/oauth2/auth?response_type=code&client_id=1091545035118-1fgup6gnafl7fhneispbln4rt6olmb19.apps.googleusercontent.com&redirect_uri=http://localhost:38377/Callback&scope=https://www.googleapis.com/auth/meetings.space.created&state&access_type=offline&approval_prompt=force&login_hint=default&include_granted_scopes=true&code_challenge=Wv7S82_ZOSlisom9x4K_qljSAb0LTPSjUogEz8Aq08E%3D&code_challenge_method=S256

[sqrrrl]

And verified that removing the padding fixes the issues:

.setPKCEProvider(new DefaultPKCEProvider() {
  @Override
   public String getCodeChallenge() {
     return super.getCodeChallenge().split("=")[0];
   }
})

[TimurSadykov]

@clundin25 Could you please take a look, maybe applies to other langs?

[clundin25]

Thanks for pointing this out @sqrrrl ! I have opened #1375 to address this issue.