Algorithm specification vulnerability for versions pre-2.0 running on JRuby

[revodoge]

Algorithm became a required param for verifying signature in #184 to address https://auth0.com/blog/critical-vulnerabilities-in-json-web-token-libraries/

The PR mentioned:

This doesn't seem to be exploitable right now because the current implementation
of OpenSSL::HMAC.digest expects a string as the key, so if rsa_public is an
OpenSSL::PKey::RSA object, JWT.decode will raise an error. But it would be
better not to depend on this OpenSSL::HMAC.digest behavior

Although the behavior mentioned holds for MRI, JRuby behaves differently and is vulnerable (i.e. you get a successful verification without any errors raised).

Out of caution, I'd recommend marking the old versions as vulnerable with a note clarifying that only JRuby is affected here: https://github.com/rubysec/ruby-advisory-db

That way people can get notified by tooling such as bundler audit of the potential need to upgrade

[excpt]

Hi @revodoge,

thank you very much for this report.

I am going to fill in the required form to get this issue into the database.

[victorhazbun]

@revodoge Does this affects version 2.2.1 and above? if not, why not? cc @excpt

[revodoge]

@victorhazbun this was fixed in 2.0 by requiring algorithm to be passed in as a parameter and from a quick glance at the current code it looks like you still need algorithms passed in so this should be fine