DeviceType = multicast allows one to specify a multicast address and port with
a Device statement. Tinc will then read/send packets to that multicast group
instead of to a tun/tap device. This allows interaction with UML, QEMU and KVM
instances that are listening on the same group.
Apart from the platform specific tun/tap driver, link with the dummy and
raw_socket devices, and optionally with support for UML and VDE devices.
At runtime, the DeviceType option can be used to select which driver to
use.
Encryption and authentication of the meta connection is spread out over
meta.c and protocol_auth.c. The new protocol was added there as well,
leading to spaghetti code. To improve things, the new protocol will now
be implemented in sptps.[ch].
The goal is to have a very simplified version of TLS. There is a record
layer, and there are only two record types: application data and
handshake messages. The handshake message contains a random nonce, an
ephemeral ECDH public key, and an ECDSA signature over the former. After
the ECDH public keys are exchanged, a shared secret is calculated, and a
TLS style PRF is used to generate the key material for the cipher and
HMAC algorithm, and further communication is encrypted and authenticated.
A lot of the simplicity comes from the fact that both sides must have
each other's public keys in advance, and there are no options to choose.
There will be one fixed cipher suite, and both peers always authenticate
each other. (Inspiration taken from Ian Grigg's hypotheses[0].)
There might be some compromise in the future, to enable or disable
encryption, authentication and compression, but there will be no choice
of algorithms. This will allow SPTPS to be built with a few embedded
crypto algorithms instead of linking with huge crypto libraries.
The API is also kept simple. There is a start and a stop function. All
data necessary to make the connection work is passed in the start
function. Instead having both send- and receive-record functions, there
is a send-record function and a receive-data function. The latter will
pass protocol data received from the peer to the SPTPS implementation,
which will in turn call a receive-record callback function when
necessary. This hides all the handshaking from the application, and is
completely independent from any event loop or socket characteristics.
[0] http://iang.org/ssl/hn_hypotheses_in_secure_protocol_design.html
The generate-keys command now generates both an RSA and an ECDSA keypair,
but one can generate-rsa-keys or generate-ecdsa-keys to just generate one type.
It is modelled after the pseudorandom function from RFC4346 (TLS 1.1), the only
significant change is the use of SHA512 and Whirlpool instead of MD5 and SHA1.
We live in the 21st century, and we require C99 semantics, so we do not need to
work around buggy libcs. The xmalloc() and related functions are now static
inline functions.
Libevent 2.0's buffer code is not completely backward compatible with 1.4's.
In order to not (mis)use it anymore, we implement it ourselves. The buffers
are automatically expanding when necessary. When consuming data from the
buffer, no memmove()s are performed. Only when adding to the buffer would
write past the end do we shift everything back to the start.
The utility functions in the lib/ directory do not really form a library.
Also, now that we build two binaries, tincctl does not need everything that was
in libvpn.a, so it is wasteful to link to it.
This is a slightly modified patch from Grzegorz Dymarek that allows tinc to use
the tunemu device, which allows tinc to be compiled for iPhones and recent
iPods. To enable support for tunemu, the --enable-tunemu option has to be used
when running the configure script.
This relieves some confusion and problems during the libevent transition.
In particular, "event_add" was defined by both.
(The 't' stands for 'timeout', 'tinc', 'temporary', or some such.)
