The DTLS implementation provides some protection against replay attacks
in accordance with RFC6347 section 4.1.2.6.

A sliding "window" of valid record sequence numbers is maintained with
the "right" hand edge of the window set to the highest sequence number we
have received so far. Records that arrive that are off the "left" hand
edge of the window are rejected. Records within the window are checked
against a list of records received so far. If we already received it then
we also reject the new record.

If we have not already received the record, or the sequence number is off
the right hand edge of the window then we verify the MAC of the record.
If MAC verification fails then we discard the record. Otherwise we mark
the record as received. If the sequence number was off the right hand edge
of the window, then we slide the window along so that the right hand edge
is in line with the newly received sequence number.

Records may arrive for future epochs, i.e. a record from after a CCS being
sent, can arrive before the CCS does if the packets get re-ordered. As we
have not yet received the CCS we are not yet in a position to decrypt or
validate the MAC of those records. OpenSSL places those records on an
unprocessed records queue. It additionally updates the window immediately,
even though we have not yet verified the MAC. This will only occur if
currently in a handshake/renegotiation.

This could be exploited by an attacker by sending a record for the next
epoch (which does not have to decrypt or have a valid MAC), with a very
large sequence number. This means the right hand edge of the window is
moved very far to the right, and all subsequent legitimate packets are
dropped causing a denial of service.

A similar effect can be achieved during the initial handshake. In this
case there is no MAC key negotiated yet. Therefore an attacker can send a
message for the current epoch with a very large sequence number. The code
will process the record as normal. If the hanshake message sequence number
(as opposed to the record sequence number that we have been talking about
so far) is in the future then the injected message is bufferred to be
handled later, but the window is still updated. Therefore all subsequent
legitimate handshake records are dropped. This aspect is not considered a
security issue because there are many ways for an attacker to disrupt the
initial handshake and prevent it from completing successfully (e.g.
injection of a handshake message will cause the Finished MAC to fail and
the handshake to be aborted). This issue comes about as a result of trying
to do replay protection, but having no integrity mechanism in place yet.
Does it even make sense to have replay protection in epoch 0? That
issue isn't addressed here though.

This addressed an OCAP Audit issue.

CVE-2016-2181
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Injects a record from epoch 1 during epoch 0 handshake, with a record
sequence number in the future, to test that the record replay protection
feature works as expected. This is described more fully in the next commit.
Reviewed-by: NRichard Levitte <levitte@openssl.org>

During a DTLS handshake we may get records destined for the next epoch
arrive before we have processed the CCS. In that case we can't decrypt or
verify the record yet, so we buffer it for later use. When we do receive
the CCS we work through the queue of unprocessed records and process them.

Unfortunately the act of processing wipes out any existing packet data
that we were still working through. This includes any records from the new
epoch that were in the same packet as the CCS. We should only process the
buffered records if we've not got any data left.
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Add a test to inject a record from the next epoch during the handshake and
make sure it doesn't get processed immediately.
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Split the create_ssl_connection() helper function into two steps: one to
create the SSL objects, and one to actually create the connection. This
provides the ability to make changes to the SSL object before the
connection is actually made.
Reviewed-by: NRichard Levitte <levitte@openssl.org>

This adds a BIO similar to a normal mem BIO but with datagram awareness.
It also has the capability to inject additional packets at arbitrary
locations into the BIO, for testing purposes.
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Dump out the records passed over the BIO. Only works for DTLS at the
moment but could easily be extended to TLS.
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Reviewed-by: NStephen Henson <steve@openssl.org>

Reviewed-by: NMatt Caswell <matt@openssl.org>

Reviewed-by: NMatt Caswell <matt@openssl.org>

Reviewed-by: NMatt Caswell <matt@openssl.org>

Reviewed-by: NMatt Caswell <matt@openssl.org>

@disablables is sorted, but these were just added at the end of
%disabled in commits c2e27310 and 22e3dcb7.
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>

The error message said "dane_tlsa_rrset" instead of "dane_tlsa_rrdata".
Reviewed-by: NRich Salz <rsalz@openssl.org>

Reviewed-by: NRich Salz <rsalz@openssl.org>

There's no reason we should enumerate every type of IMPLEMENT_ and
DECLARE_ line (and forget the ones we add a little now and then).
They all start with the same first word, let's just take'm all.
Reviewed-by: NRich Salz <rsalz@openssl.org>

Run util/openssl-format-source on ssl/

Some comments and hand-formatted tables were fixed up
manually by disabling auto-formatting.
Reviewed-by: NRich Salz <rsalz@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>
Reviewed-by: NStephen Henson <steve@openssl.org>

Duplicate alerts have happened, see
70c22888Reviewed-by: NRich Salz <rsalz@openssl.org>

Make maximum fragment length configurable and add various fragmentation
tests, in addition to the existing multi-buffer tests.
Reviewed-by: NRich Salz <rsalz@openssl.org>

Reviewed-by: NMatt Caswell <matt@openssl.org>

Since dasync isn't installed, and is only ever used as a dynamic
engine, there's no reason to consider it for initialization when
building static engines.
Reviewed-by: NBen Laurie <ben@openssl.org>

Reviewed-by: NMatt Caswell <matt@openssl.org>

Constify X509_SIG_get0() and order arguments to mactch new standard.

Add X509_SIG_get0_mutable() to support modification or initialisation
of an X509_SIG structure.
Reviewed-by: NMatt Caswell <matt@openssl.org>

using util/openssl-format-source on s_derver, s_client, ca.c, speed.c only...

Fix/merge some #ifndef
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>

Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>

Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>

Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>

Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>
Reviewed-by: NStephen Henson <steve@openssl.org>

Put the main object first in the params list.
Reviewed-by: NRichard Levitte <levitte@openssl.org>
Reviewed-by: NStephen Henson <steve@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>
Reviewed-by: NStephen Henson <steve@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>