DTLS can handle out of order record delivery. Additionally since
handshake messages can be bigger than will fit into a single packet, the
messages can be fragmented across multiple records (as with normal TLS).
That means that the messages can arrive mixed up, and we have to
reassemble them. We keep a queue of buffered messages that are "from the
future", i.e. messages we're not ready to deal with yet but have arrived
early. The messages held there may not be full yet - they could be one
or more fragments that are still in the process of being reassembled.

The code assumes that we will eventually complete the reassembly and
when that occurs the complete message is removed from the queue at the
point that we need to use it.

However, DTLS is also tolerant of packet loss. To get around that DTLS
messages can be retransmitted. If we receive a full (non-fragmented)
message from the peer after previously having received a fragment of
that message, then we ignore the message in the queue and just use the
non-fragmented version. At that point the queued message will never get
removed.

Additionally the peer could send "future" messages that we never get to
in order to complete the handshake. Each message has a sequence number
(starting from 0). We will accept a message fragment for the current
message sequence number, or for any sequence up to 10 into the future.
However if the Finished message has a sequence number of 2, anything
greater than that in the queue is just left there.

So, in those two ways we can end up with "orphaned" data in the queue
that will never get removed - except when the connection is closed. At
that point all the queues are flushed.

An attacker could seek to exploit this by filling up the queues with
lots of large messages that are never going to be used in order to
attempt a DoS by memory exhaustion.

I will assume that we are only concerned with servers here. It does not
seem reasonable to be concerned about a memory exhaustion attack on a
client. They are unlikely to process enough connections for this to be
an issue.

A "long" handshake with many messages might be 5 messages long (in the
incoming direction), e.g. ClientHello, Certificate, ClientKeyExchange,
CertificateVerify, Finished. So this would be message sequence numbers 0
to 4. Additionally we can buffer up to 10 messages in the future.
Therefore the maximum number of messages that an attacker could send
that could get orphaned would typically be 15.

The maximum size that a DTLS message is allowed to be is defined by
max_cert_list, which by default is 100k. Therefore the maximum amount of
"orphaned" memory per connection is 1500k.

Message sequence numbers get reset after the Finished message, so
renegotiation will not extend the maximum number of messages that can be
orphaned per connection.

As noted above, the queues do get cleared when the connection is closed.
Therefore in order to mount an effective attack, an attacker would have
to open many simultaneous connections.

Issue reported by Quan Luo.

CVE-2016-2179

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

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

MR: #3176
(cherry picked from commit a73be798)

Reviewed-by: Richard Levitte <levitte@openssl.org>
(cherry picked from commit 2a9afa40)

A function error code needed updating due to merge issues.

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

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: Richard 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: Richard Levitte <levitte@openssl.org>

(cherry picked from commit a1be17a7

)

Conflicts:
	crypto/pem/pem_err.c

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Stephen Henson <steve@openssl.org>

Apply a limit to the maximum blob length which can be read in do_d2i_bio()
to avoid excessive allocation.

Thanks to Shi Lei for reporting this.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit 66bcba14)

If an oversize BIGNUM is presented to BN_bn2dec() it can cause
BN_div_word() to fail and not reduce the value of 't' resulting
in OOB writes to the bn_data buffer and eventually crashing.

Fix by checking return value of BN_div_word() and checking writes
don't overflow buffer.

Thanks to Shi Lei for reporting this bug.

CVE-2016-2182

Reviewed-by: Tim Hudson <tjh@openssl.org>
(cherry picked from commit 07bed46f)

Conflicts:
	crypto/bn/bn_print.c

Check for error return in BN_div_word().

Reviewed-by: Tim Hudson <tjh@openssl.org>
(cherry picked from commit 8b9afbc0)

Thanks to Hanno Böck for reporting this bug.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit 39a43280)

Conflicts:
	crypto/pkcs12/p12_utl.c

Fix error path leaks in a2i_ASN1_STRING(), a2i_ASN1_INTEGER() and
a2i_ASN1_ENUMERATED().

Thanks to Shi Lei for reporting these issues.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit e1be1dce)

GH: #1322

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Stephen Henson <steve@openssl.org>
(cherry picked from commit 32baafb2)

Thanks to Shi Lei for reporting this bug.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit 81f69e5b)

Thanks to Shi Lei for reporting this issue.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit af601b83)

Use correct length in old ASN.1 indefinite length sequence decoder
(only used by SSL_SESSION).

This bug was discovered by Hanno Böck using libfuzzer.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit 436dead2)

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit 134ab513)

Reviewed-by: Richard Levitte <levitte@openssl.org>
(cherry picked from commit e9f17097)

Reviewed-by: Richard Levitte <levitte@openssl.org>
(cherry picked from commit 56f9953c)

TS_OBJ_print_bio() misuses OBJ_txt2obj: it should print the result
as a null terminated buffer. The length value returned is the total
length the complete text reprsentation would need not the amount of
data written.

CVE-2016-2180

Thanks to Shi Lei for reporting this bug.

Reviewed-by: Matt Caswell <matt@openssl.org>
(cherry picked from commit 0ed26acc)

Ensure things really do get cleared when we intend them to.

Addresses an OCAP Audit issue.

Reviewed-by: Andy Polyakov <appro@openssl.org>
(cherry picked from commit cb5ebf96)

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit 6ad8c482)

While travelling up the certificate chain, the internal
proxy_path_length must be updated with the pCPathLengthConstraint
value, or verification will not work properly.  This corresponds to
RFC 3820, 4.1.4 (a).

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit 30aeb312)

The subject name MUST be the same as the issuer name, with a single CN
entry added.

RT#1852

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit 338fb168)

RAND_pseudo_bytes() allows random data to be returned even in low entropy
conditions. Sometimes this is ok. Many times it is not. For the avoidance
of any doubt, replace existing usage of RAND_pseudo_bytes() with
RAND_bytes().

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

The previous "fix" still left "k" exposed to constant time problems in
the later BN_mod_inverse() call. Ensure both k and kq have the
BN_FLG_CONSTTIME flag set at the earliest opportunity after creation.

CVE-2016-2178

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit b7d0f283)

Operations in the DSA signing algorithm should run in constant time in
order to avoid side channel attacks. A flaw in the OpenSSL DSA
implementation means that a non-constant time codepath is followed for
certain operations. This has been demonstrated through a cache-timing
attack to be sufficient for an attacker to recover the private DSA key.

CVE-2016-2178

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(cherry picked from commit 621eaf49)

Fix typos and clarify a few things in the CONTRIBUTING file.

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

A common idiom in the codebase is:

if (p + len > limit)
{
    return; /* Too long */
}

Where "p" points to some malloc'd data of SIZE bytes and
limit == p + SIZE

"len" here could be from some externally supplied data (e.g. from a TLS
message).

The rules of C pointer arithmetic are such that "p + len" is only well
defined where len <= SIZE. Therefore the above idiom is actually
undefined behaviour.

For example this could cause problems if some malloc implementation
provides an address for "p" such that "p + len" actually overflows for
values of len that are too big and therefore p + len < limit!

Issue reported by Guido Vranken.

CVE-2016-2177

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

Set ctx->error = X509_V_ERR_OUT_OF_MEM when verificaiton cannot
continue due to malloc failure.  Similarly for issuer lookup failures
and caller errors (bad parameters or invalid state).

Also, when X509_verify_cert() returns <= 0 make sure that the
verification status does not remain X509_V_OK, as a last resort set
it it to X509_V_ERR_UNSPECIFIED, just in case some code path returns
an error without setting an appropriate value of ctx->error.

Add new and some missing error codes to X509 error -> SSL alert switch.

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

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

The functions SRP_Calc_client_key() and SRP_Calc_server_key() were
incorrectly returning a valid pointer in the event of error.

Issue reported by Yuan Jochen Kang

Reviewed-by: Richard Levitte <levitte@openssl.org>
(cherry picked from commit 308ff286)

In the X509 app check that the obtained public key is valid before we
attempt to use it.

Issue reported by Yuan Jochen Kang.

Reviewed-by: Viktor Dukhovni <viktor@openssl.org>

Reviewed-by: Richard Levitte <levitte@openssl.org>
(cherry picked from commit c393a5de)

Reviewed-by: Viktor Dukhovni <viktor@openssl.org>

RT#3826

Reviewed-by: Tim Hudson <tjh@openssl.org>
(cherry picked from commit 2b4825d0)

PR#4449

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

(cherry picked from commit b1f8ba4d)

PR#4466

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

(cherry picked from commit 06227924)

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit 708cf5de)

The default ASN.1 handling can be used for SEED. This also makes
CMS work with SEED.

PR#4504

Reviewed-by: Rich Salz <rsalz@openssl.org>
(cherry picked from commit c0aa8c27)