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>

 * SSL_SESSION_set1_id()
 * SSL_SESSION_get0_id_context()
 * SSL_CTX_get_tlsext_status_cb()
 * SSL_CTX_get_tlsext_status_arg()
Reviewed-by: NRichard Levitte <levitte@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>

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

These functions are no longer relevant to 1.1.0 (we always have auto ecdh
on) - but no reason to break old code that tries to call it. The macros will
only return a dummy "success" result if the app was trying to enable ecdh.
Disabling can't be done in quite this way any more.

Fixes Github Issue #1437
Reviewed-by: NViktor Dukhovni <viktor@openssl.org>

Reviewed-by: NMatt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1451)

DTLSv1_client_method() is deprecated, but it was the only way to obtain
DTLS1_BAD_VER support. The SSL_OP_CISCO_ANYCONNECT hack doesn't work with
DTLS_client_method(), and it's relatively non-trivial to make it work without
expanding the hack into lots of places.

So deprecate SSL_OP_CISCO_ANYCONNECT with DTLSv1_client_method(), and make
it work with SSL_CTX_set_{min,max}_proto_version(DTLS1_BAD_VER) instead.
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>

SSL_set_rbio() and SSL_set_wbio() are new functions in 1.1.0 and really
should be called SSL_set0_rbio() and SSL_set0_wbio(). The old
implementation was not consistent with what "set0" means though as there
were special cases around what happens if the rbio and wbio are the same.
We were only ever taking one reference on the BIO, and checking everywhere
whether the rbio and wbio are the same so as not to double free.

A better approach is to rename the functions to SSL_set0_rbio() and
SSL_set0_wbio(). If an existing BIO is present it is *always* freed
regardless of whether the rbio and wbio are the same or not. It is
therefore the callers responsibility to ensure that a reference is taken
for *each* usage, i.e. one for the rbio and one for the wbio.

The legacy function SSL_set_bio() takes both the rbio and wbio in one go
and sets them both. We can wrap up the old behaviour in the implementation
of that function, i.e. previously if the rbio and wbio are the same in the
call to this function then the caller only needed to ensure one reference
was passed. This behaviour is retained by internally upping the ref count.

This commit was inspired by BoringSSL commit f715c423224.

RT#4572
Reviewed-by: NRich Salz <rsalz@openssl.org>

Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1301)

Reviewed-by: NRichard Levitte <levitte@openssl.org>
GH: #1330

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

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

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

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

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

In light of potential UKS (unknown key share) attacks on some
applications, primarily browsers, despite RFC761, name checks are
by default applied with DANE-EE(3) TLSA records.  Applications for
which UKS is not a problem can optionally disable DANE-EE(3) name
checks via the new SSL_CTX_dane_set_flags() and friends.
Reviewed-by: NRich Salz <rsalz@openssl.org>

Commit aea145e3 removed some error codes that are generated
algorithmically: mapping alerts to error texts.  Found by
Andreas Karlsson.  This restores them, and adds two missing ones.
Reviewed-by: NMatt Caswell <matt@openssl.org>

If application uses any of Windows-specific interfaces, make it
application developer's respondibility to include <windows.h>.
Rationale is that <windows.h> is quite "toxic" and is sensitive
to inclusion order (most notably in relation to <winsock2.h>).
It's only natural to give complete control to the application developer.
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>

Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1275)

Commit 361a1191 removed all ciphersuites that could support temporary
RSA keys, therefore the associated functions were removed. We should have
"no-op" compatibility macros for these.
Reviewed-by: NStephen Henson <steve@openssl.org>

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

Reviewed-by: NKurt Roeckx <kurt@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1245)

GH1098: Add X509_get_pathlen() (and a test)
GH1097:  Add SSL_is_dtls() function.

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

The tlsext_status_type field in SSL is used by e.g. OpenResty to determine
if the client requested the certificate status, but SSL is now opaque.
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>

The ssl3_init_finished_mac() function can fail, in which case we need to
propagate the error up through the stack.

RT#3198
Reviewed-by: NRich Salz <rsalz@openssl.org>

accompanying documentation.
Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1135)

Add script to find unused err/reason codes
Remove unused reason codes.
Remove entries for unused functions
Reviewed-by: NMatt Caswell <matt@openssl.org>

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

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

Add a status return value instead of void.
Add some sanity checks on reference counter value.
Update the docs.
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>

If the application has limited the size of the async pool using
ASYNC_init_thread() then we could run out of jobs while trying to start a
libssl io operation. However libssl was failing to handle this and treating
it like a fatal error. It should not be fatal...we just need to retry when
there are jobs available again.
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Reviewed-by: NRichard Levitte <levitte@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/952)

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

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

The no-op de-init macros may fail because of extraneous ";", so we use
a slightly different construct instead.
Reviewed-by: NTim Hudson <tjh@openssl.org>
Reviewed-by: NRichard Levitte <levitte@openssl.org>

SSL_COMP_free_compression_methods() should not be called expicitly - we
should leave auto-deinit to clean this up instead.
Reviewed-by: NTim Hudson <tjh@openssl.org>
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Add an accessor for SSL_CTX.

Since libssl was made opaque, there is no way for users to access the
cipher_list, while users can set the cipher_list by
SSL_CTX_set_cipher_list().
Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>

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

Signed-off-by: NRob Percival <robpercival@google.com>
Reviewed-by: NEmilia Käsper <emilia@openssl.org>