This builds on the work started in 1ab3836b and extends is so that
each extension has its own identified parsing functions, as well as an
allowed context identifying which messages and protocols it is relevant for.
Subsequent commits will do a similar job for the ServerHello extensions.
This will enable us to have common functions for processing extension blocks
no matter which of the multiple messages they are received from. In TLSv1.3
a number of different messages have extension blocks, and some extensions
have moved from one message to another when compared to TLSv1.2.

Perl changes reviewed by Richard Levitte. Non-perl changes reviewed by Rich
Salz
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Subsequent commits will pull other extensions code into this file.

Perl changes reviewed by Richard Levitte. Non-perl changes reviewed by Rich
Salz
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NRichard Levitte <levitte@openssl.org>

Don't use what is in supported_versions for the RSA pre-master
Reviewed-by: NEmilia Käsper <emilia@openssl.org>

There is a set of miscellaneous processing for OCSP, CT etc at the end of
the ServerDone processing. In TLS1.3 we don't have a ServerDone, so this
needs to move elsewhere.
Reviewed-by: NRich Salz <rsalz@openssl.org>

This is a major overhaul of the TLSv1.3 state machine. Currently it still
looks like TLSv1.2. This commit changes things around so that it starts
to look a bit less like TLSv1.2 and bit more like TLSv1.3.

After this commit we have:

ClientHello
+ key_share          ---->
                           ServerHello
                           +key_share
                           {CertificateRequest*}
                           {Certificate*}
                           {CertificateStatus*}
                     <---- {Finished}
{Certificate*}
{CertificateVerify*}
{Finished}           ---->
[ApplicationData]    <---> [Application Data]

Key differences between this intermediate position and the final TLSv1.3
position are:
- No EncryptedExtensions message yet
- No server side CertificateVerify message yet
- CertificateStatus still exists as a separate message
- A number of the messages are still in the TLSv1.2 format
- Still running on the TLSv1.2 record layer
Reviewed-by: NRich Salz <rsalz@openssl.org>

Added some TODOs, refactored a couple of things and added a SSL_IS_TLS13()
macro.
Reviewed-by: NRich Salz <rsalz@openssl.org>

There were a few places where we weren't checking to see if we were using
the draft TLS1.3 version or not.
Reviewed-by: NRich Salz <rsalz@openssl.org>

Renegotiation does not exist in TLS1.3, so we need to disable it at some
point.
Reviewed-by: NRich Salz <rsalz@openssl.org>

Replace a bare ";" with "continue;" for the body of a for loop.
Reviewed-by: NRich Salz <rsalz@openssl.org>

If supported_versions is present it takes precedence.
Reviewed-by: NRich Salz <rsalz@openssl.org>

We can end up with a NULL SSL_METHOD function if a method has been
disabled. If that happens then we shouldn't call vent->smeth().
Reviewed-by: NRich Salz <rsalz@openssl.org>

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

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

For consistency with the TLSv1.3 spec.
Reviewed-by: NKurt Roeckx <kurt@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>

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

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

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

Based on review feedback received.
Reviewed-by: NKurt Roeckx <kurt@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>

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

We read it later in grow_init_buf(). If CCS is the first thing received in
a flight, then it will use the init_msg from the last flight we received. If
the init_buf has been grown in the meantime then it will point to some
arbitrary other memory location. This is likely to result in grow_init_buf()
attempting to grow to some excessively large amount which is likely to
fail. In practice this should never happen because the only time we receive
a CCS as the first thing in a flight is in an abbreviated handshake. None
of the preceding messages from the server flight would be large enough to
trigger this.
Reviewed-by: NRich Salz <rsalz@openssl.org>

Travis is reporting one file at a time shadowed variable warnings where
"read" has been used. This attempts to go through all of libssl and replace
"read" with "readbytes" to fix all the problems in one go.
Reviewed-by: NRich Salz <rsalz@openssl.org>

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

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

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

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

Writing still to be done
Reviewed-by: NRich Salz <rsalz@openssl.org>

Includes addition of the various options to s_server/s_client. Also adds
one of the new TLS1.3 ciphersuites.

This isn't "real" TLS1.3!! It's identical to TLS1.2 apart from the protocol
and the ciphersuite...and the ciphersuite is just a renamed TLS1.2 one (not
a "real" TLS1.3 ciphersuite).
Reviewed-by: NRich Salz <rsalz@openssl.org>

tls_construct_finished() used to have different arguments to all of the
other construction functions. It doesn't anymore, so there is no neeed to
treat it as a special case.
Reviewed-by: NRich Salz <rsalz@openssl.org>

Ensure all message types work the same way including CCS so that the state
machine doesn't need to know about special cases. Put all the special logic
into ssl_set_handshake_header() and ssl_close_construct_packet().
Reviewed-by: NRich Salz <rsalz@openssl.org>

Move setting the handshake header up a level into the state machine code
in order to reduce boilerplate.
Reviewed-by: NRich Salz <rsalz@openssl.org>

Instead of initialising, finishing and cleaning up the WPACKET in every
message construction function, we should do it once in
write_state_machine().
Reviewed-by: NRich Salz <rsalz@openssl.org>

ssl_set_handshake_header2() was only ever a temporary name while we had
to have ssl_set_handshake_header() for code that hadn't been converted to
WPACKET yet. No code remains that needed that so we can rename it.
Reviewed-by: NRich Salz <rsalz@openssl.org>

A TLS message includes 3 bytes for its length in the header for the message.
This would allow for messages up to 16Mb in length. Messages of this length
are excessive and OpenSSL includes a check to ensure that a peer is sending
reasonably sized messages in order to avoid too much memory being consumed
to service a connection. A flaw in the logic of version 1.1.0 means that
memory for the message is allocated too early, prior to the excessive
message length check. Due to way memory is allocated in OpenSSL this could
mean an attacker could force up to 21Mb to be allocated to service a
connection. This could lead to a Denial of Service through memory
exhaustion. However, the excessive message length check still takes place,
and this would cause the connection to immediately fail. Assuming that the
application calls SSL_free() on the failed conneciton in a timely manner
then the 21Mb of allocated memory will then be immediately freed again.
Therefore the excessive memory allocation will be transitory in nature.
This then means that there is only a security impact if:

1) The application does not call SSL_free() in a timely manner in the
event that the connection fails
or
2) The application is working in a constrained environment where there
is very little free memory
or
3) The attacker initiates multiple connection attempts such that there
are multiple connections in a state where memory has been allocated for
the connection; SSL_free() has not yet been called; and there is
insufficient memory to service the multiple requests.

Except in the instance of (1) above any Denial Of Service is likely to
be transitory because as soon as the connection fails the memory is
subsequently freed again in the SSL_free() call. However there is an
increased risk during this period of application crashes due to the lack
of memory - which would then mean a more serious Denial of Service.

This issue does not affect DTLS users.

Issue was reported by Shi Lei (Gear Team, Qihoo 360 Inc.).

CVE-2016-6307
Reviewed-by: NRichard Levitte <levitte@openssl.org>

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

All the other functions that take an argument for the number of bytes
use convenience macros for this purpose. We should do the same with
WPACKET_put_bytes().
Reviewed-by: NRich Salz <rsalz@openssl.org>

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

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

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

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

No need to declare an explicit sub-packet. Just start one.
Reviewed-by: NRich Salz <rsalz@openssl.org>