Using the tinc command, an administrator of an existing VPN can generate
invitations for new nodes. The invitation is a small URL that can easily
be copy&pasted into email or live chat. Another person can have tinc
automatically setup the necessary configuration files and exchange keys
with the server, by only using the invitation URL.
The invitation protocol uses temporary ECDSA keys. The invitation URL
consists of the hostname and port of the server, a hash of the server's
temporary ECDSA key and a cookie. When the client wants to accept an
invitation, it also creates a temporary ECDSA key, connects to the server
and says it wants to accept an invitation. Both sides exchange their
temporary keys. The client verifies that the server's key matches the hash
in the invitation URL. After setting up an SPTPS connection using the
temporary keys, the client gives the cookie to the server. If the cookie
is valid, the server sends the client an invitation file containing the
client's new name and a copy of the server's host config file. If everything
is ok, the client will generate a long-term ECDSA key and send it to the
server, which will add it to a new host config file for the client.
The invitation protocol currently allows multiple host config files to be
send from the server to the client. However, the client filters out
most configuration variables for its own host configuration file. In
particular, it only accepts Name, Mode, Broadcast, ConnectTo, Subnet and
AutoConnect. Also, at the moment no tinc-up script is generated.
When an invitation has succesfully been accepted, the client needs to start
the tinc daemon manually.
At this point, c->config_tree may or may not be NULL, but this does not tell us whether it is an
outgoing connection or not. For incoming connections, we do not know the peer's name yet,
so we always have to claim ECDSA support. For outgoing connections, we always need to check
whether we have the peer's ECDSA public key, so that if we don't, we correctly tell the peer that
we want to upgrade.
This gets rid of the rest of the symbolic links. However, as a consequence, the
crypto header files have now moved to src/, and can no longer contain
library-specific declarations. Therefore, cipher_t, digest_t, ecdh_t, ecdsa_t
and rsa_t are now all opaque types, and only pointers to those types can be
used.
Normally all requests sent via the meta connections are checked so that they
cannot be larger than the input buffer. However, when packets are forwarded via
meta connections, they are copied into a packet buffer without checking whether
it fits into it. Since the packet buffer is allocated on the stack, this in
effect allows an authenticated remote node to cause a stack overflow.
This issue was found by Martin Schobert.
The tree functions were never used on the connection_tree, a list is more appropriate.
Also be more paranoid about connections disappearing while traversing the list.
Struct outgoing_ts and connection_ts were depending too much on each other,
causing lots of problems, especially the reuse of a connection_t. Now, whenever
a connection is closed it is immediately removed from the list of connections
and destroyed.
Proxy type "exec" can be used to have an external script or binary set
up an outgoing connection. Standard input and output will be used to
exchange data with the external command. The variables REMOTEADDRESS and
REMOTEPORT are set to the intended destination address and port.
When the Proxy option is used, outgoing connections will be made via the
specified proxy. There is no support for authentication methods or for having
the proxy forward incoming connections, and there is no attempt to proxy UDP.
* Everything is identical except the headers of the records.
* Instead of sending explicit message length and having an implicit sequence
number, datagram mode has an implicit message length and an explicit sequence
number.
* The sequence number is used to set the most significant bytes of the counter.
This allows tincctl to receive log messages from a running tincd,
independent of what is logged to syslog or to file. Tincctl can receive
debug messages with an arbitrary level.
If we don't have ECDSA keys for the node we connect to, set protocol_minor
to 1, to indicate this to the other end. This will first complete the
old way of authentication with RSA keys, and will then exchange ECDSA keys.
The connection will be terminated right afterwards, and the next attempt
will use ECDSA keys.
With some exceptions, tinc only accepted host configuration options for the
local node from the corresponding host configuration file. Although this is
documented, many people expect that they can also put those options in
tinc.conf. Tinc now internally merges the contents of both tinc.conf and the
local host configuration file.
If one uses a symbolic name for the Port option, tinc will send that name
literally to other nodes. However, it is not guaranteed that all nodes have
the same contents in /etc/services, or have such a file at all.
