[GIT PULL V2] Fixes for rekeying, Android builds, etc.

[Nikos Mavrogiannopoulos]

On 02/18/2014 07:08 AM, Kevin Cernekee wrote:

> Also, start_cstp_connection() can still change the DTLS parameters.
> I'd assume we need to call dtls_reconnect() unconditionally after
> cstp_reconnect() to allow for this,

dtls_reconnect() follows the cstp_reconnect() call as it is now from the
cstp_mainloop. I don't think they should be completely merged, because
in the use-case the dtls_reconnect only occurs if the dtls rekey method
is set to none.

> or go back to calling dtls_close()
> upon master secret regeneration.  But it's OK to skip dtls_handshake()
> after cstp_handshake(), provided that dtls_times.rekey_method !=
> REKEY_NONE.
> This still leaves the question of whether it is safe to rekey DTLS via
> dtls_reconnect() / dtls_try_handshake(), or if we actually need to
> send a new master secret first?  What do the Cisco clients do?  Maybe
> the master secret regeneration could be moved elsewhere.

We don't to generate a new key for a rekey process. The reconnection
(and subsequent handshake) ensures that the final DTLS key will be
different (will also depend on the nonces of the handshake).

> Absent a full CSTP reconnection, how should dtls_times.last_rekey get updated?

It is updated by keepalive_action() when sending the KA_REKEY command.

> If keepalive_action() only returns KA_REKEY for REKEY_TUNNEL, will the
> new REKEY_SSL logic in dtls.c ever run?

There is something fishy there indeed. It should be != REKEY_NONE. I've
updated that. I've tried to fix the open issues, and make it a bit more
resistant to failures (if DTLS rehandshake it will now reconnect).

> FWIW I set a 4-minute rekey interval on my ASA, disabled all rekeying
> in openconnect, and ran it overnight with no obvious problems.  But I
> would hate to break somebody else's configuration, because these "VPN
> quits passing traffic after 3 days" problems are very frustrating to
> debug.

Without rekey one can transfer 2^48 DTLS packets before the TLS
connection terminates. That's an enormous amount for 3 days though.

regards,
Nikos