Because the global cookie threshold is higher than the per-IP block
threshold, it was previously possible for an attacker to block a legitimate
user by sending spoofed IKE_SA_INIT packets from that user's IP.
The timespan for requiring cookies is now also not extended anymore with
every IKE_SA_INIT received during the calm down period. Because this
allowed an attacker, after initially triggering the global cookie threshold,
to force cookies for all clients by sending just a single spoofed
IKE_SA_INIT every 10 seconds.
We keep track of reaching the per-IP threshold in segments of the hashed
IP addresses, so only a (random, due to chunk_hash()'s random key) subset
of clients will receive cookies, if single IPs are targeted.
The default global threshold is increased a bit.
If we are under attack and there are lots of requests, we might hit
the previous use count limit pretty quickly and may switch secrets multiple
times a second, which renders the 10 second default lifetime of COOKIEs
pointless and prevents legitimate clients from sending requests with valid
COOKIEs.
Depending on how CLOCK_MONOTONIC is implemented, time_monotonic() might
return 0 within 1 second after the system is started. If that's the
case, we just default to 0 for now to avoid a crash (doesn't "hide" the
system time, but it's only the uptime anyway in this case).
Closesstrongswan/strongswan#435.
While this doesn't really create any problems it is not 100% correct to
accept such messages because, of course, the sender of an IKE_SA_INIT
request is always the original initiator of an IKE_SA.
We currently don't check the flag later, so we wouldn't notice if the
peer doesn't set it in later messages (ike_sa_id_t.equals doesn't
compare it anymore since we added support for IKEv1, in particular since
17ec1c74de).
We sent both a notify using IKEv1 and IKEv2. This is a little more aggressive
than required, RFC 5996 says we "SHOULD send an unauthenticated Notify
message of type INVALID_MAJOR_VERSION containing the highest (closest) version
number it supports".
Fixes#657.
When the monotonic timer is initialized to 0 right after the system is
booted the daemon responded with COOKIES for COOKIE_CALMDOWN_DELAY (10s).
Since the COOKIE verification code actually produces an overflow for
COOKIE_LIFETIME (10s) it wouldn't even accept properly returned COOKIEs.
Checking for last_cookie makes sense anyway as that condition must only
apply if we actually sent a COOKIE before.
This ensures that no threads are active when plugins and the rest of the
daemon are unloaded.
callback_job_t was simplified a lot in the process as its main
functionality is now contained in processor_t. The parent-child
relationships were abandoned as these were only needed to simplify job
cancellation.
Toggling COOKIEs on/off is problematic: After doing a COOKIE exchange as
initiator, we can't know if the completing IKE_SA_INIT message is to our first
request or the one with the COOKIE. If the responder just enabled/disabled
COOKIEs and packets get retransmitted, both might be true. Avoiding COOKIE
behavior toggling improves the situation, but does not solve the problem during
the initial COOKIE activation.
Tobias Brunner