From https://geti2p.net/en/docs/api/samv3:
If SILENT=false was passed, which is the default value, the SAM bridge
sends the client a ASCII line containing the base64 public destination
key of the requesting peer
So, `Accept()` is supposed to receive a Base64 encoded destination of
the connecting peer, but if it receives something like this instead:
STREAM STATUS RESULT=I2P_ERROR MESSAGE="Session was closed"
then destroy the session.
Peeking at the underlying socket file descriptor of `Sock` and checkig
if it is `INVALID_SOCKET` is bad encapsulation and stands in the way of
testing/mocking/fuzzing.
Instead use an empty unique_ptr to denote that there is no valid socket.
The fs.* files are already part of the libbitcoin_util library. With the
introduction of the fs_helpers.* it makes sense to move fs.* into the
util/ directory as well.
Instead of providing our destination (private key) to the I2P proxy when
creating the session, ask it to generate one for us and do not save it
on disk.
Change the types of `i2p::Connection::sock` and
`i2p::sam::Session::m_control_sock` from `Sock` to
`std::unique_ptr<Sock>`.
Using pointers would allow us to sneak `FuzzedSock` instead of `Sock`
and have the methods of the former called.
After this change a test only needs to replace `CreateSock()` with
a function that returns `FuzzedSock`.
Put a limit on the amount of data `Sock::RecvUntilTerminator()` can read
if no terminator is received.
In the case of I2P this avoids a runaway (or malicious) I2P proxy
sending us tons of data without a terminator before a timeout is
triggered.
Implement the following commands from the I2P SAM protocol:
* HELLO: needed for all of the remaining ones
* DEST GENERATE: to generate our private key and destination
* NAMING LOOKUP: to convert .i2p addresses to destinations
* SESSION CREATE: needed for STREAM CONNECT and STREAM ACCEPT
* STREAM CONNECT: to make outgoing connections
* STREAM ACCEPT: to accept incoming connections
