Handling SNI alerts in OpenJDK

[Omair Majid]

Hi Bernd,

* ecki at zusammenkunft.net <ecki at zusammenkunft.net> [2015-11-16 15:17]:
> I brought this up before, and agree with you that it is a good idea:
> if the server sends the alert and treats it fatal there is no problem
> in at least trying to continue. It is also not a security problem
> because the certificate will be validated (and if it is indeed the
> wrong server it will be noticed).
> 
> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7127374
> 
> I am not sure why it was rejected, most likely because of the unclear
> warning semantics. However I thi k there is no problem in continuing,
> either the server cooperates or not, the client will notice. Other
> implementations handle this less picky and still work.

I just wanted to clarify that this is slightly different from my
proposal. This bug suggests that if the server sends a *fatal* alert the
client should continue. This goes against the specification. RFC 5246
says: 

"Upon transmission or receipt of a fatal alert message, both parties
immediately close the connection."

So, I am not sure if not following the RFC is a good idea or not. Maybe
it will be better, I am not sure. I haven't really looked into it. Do
you know how browsers or other SSL/TLS clients handle this?

What I am asking for is for a slightly different case: *warning* (not
fatal) alerts to be treated differently. RFC 5246 states:

"If an alert with a level of warning is sent and received, generally
the connection can continue normally.  If the receiving party decides
not to proceed with the connection (e.g., after having received a
no_renegotiation alert that it is not willing to accept), it SHOULD send
a fatal alert to terminate the connection."

It is this case where the specification allows OpenJDK a choice. OpenJDK
can either treat a unrecognized_name warning alert as fatal (and abort)
or non-fatal (and continue). Many other clients (including browsers such
as Firefox and Chrome) continue normally in the presence of a
unrecognized_name warning alert. From that point of view OpenJDK should
too.

Thanks,
Omair

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