CRL handling is over-aggressive

[macintux]

Per http://security.stackexchange.com/questions/10158/ocsp-and-crls-specified-in-ca-or-client-certificate it doesn't appear that a CRL is mandatory for every item in a chain of certificates.

Yet https://github.com/basho/riak_api/blob/develop/src/riak_api_ssl.erl#L101-L105 fails certificate validation without one.

This is impacting JRuby + our ruby client, and may well impact other applications attempting client-side certificate-based authentication.

cc @Vagabond in case he'd care to chime in. Not sure what the standards say here.

[macintux]

riak.conf workaround for chains without CRL: check_crl=off

Thanks @Vagabond

/cc @bkerley

[bkerley]

check_crl = off breaks previously-working client cert auth in the ruby-client running on C ruby.

[macintux]

https://github.com/basho/riak_api/blob/develop/src/riak_api_ssl.erl#L90-L91

We're hiding errors if validation is turned on.

[macintux]

Here's the default verification function from public_key.hrl in the OTP public_key library:

-define(DEFAULT_VERIFYFUN,
    {fun(_,{bad_cert, _} = Reason, _) ->
         {fail, Reason};
        (_,{extension, _}, UserState) ->
         {unknown, UserState};
        (_, valid, UserState) ->
         {valid, UserState};
        (_, valid_peer, UserState) ->
         {valid, UserState}
     end, []}).

[macintux]

And yet, I can't prove that in riak_test. Quite befuddled.

[Vagabond]

I think you're correct, you should be handling bad_cert and extension explicitly and remove that catch-all clause.

[macintux]

When I create a parallel certificate structure that Riak doesn't know about, validate_function is not invoked, so the impact isn't as severe as I feared.

Still unclear what's happening with @bkerley and his Ruby client.

[bkerley]

As near as I can tell, it has two code paths:

Ruby with C OpenSSL

1. Client sends Riak client cert only
2. Riak validates client cert against configured CA
3. Riak validates client cert CN

JRuby with BouncyCastle "OpenSSL"

1. Client sends Riak client cert and client cert's issuer/CA
2. Riak might validate client cert against configured CA?
3. Riak attempts to validate CRL on client-provided CA
4. If no CRL entry on client-provided CA, close connection.

[macintux]

Is this matrix accurate, Bryce?

My theory (admittedly weak) is your certs are broken somehow and we're masking it with the catch-all function header in validate_function.

check_crl	CRuby	JRuby
on	:thumbsup:	:thumbsdown:
off	:thumbsdown:	:thumbsdown:

[Vagabond]

Fixing the verify fun should help, see what you get when you do that.

[Vagabond]

It is very easy to generate bad ssl certificate chains.

[macintux]

Bryce has a fixed validate_function for testing.

The original bug (mandating CRLs) also needs to be addressed if that is the correct diagnosis; I suspect the conflation of two problems isn't helping with comprehension.

[macintux]

Ok, at this point there are two changes that seem useful but have yet to be proved one way or another. Bryce is struggling to get consistent results, but the standard tests can't reproduce what he's seeing, so I'm going to assume there are other "SSL is bloody hard" problems there.

• Make CRL handling optional
• Handle bad certs sent to validate_function

Leaving target at 2.0.1, working on tracing the OTP call chain to better understand what happens with the current code and the implications of changing it.

[Vagabond]

Trying the ruby client with certificated generated by the riak_tests would go a long way to clarifying if it is a certificate problem.