Jump channel

[JoostJM]

Implements the option of connecting to a SSH server through another SSH server (jump-host).
This is achieved through a new ProxyConnector class: SshConnector.

In addition, refactor the structure of ConnectionInfo objects, improving the configuration of proxy connections.
Proxy connections are now defined using ConnectionInfo objects, which are set to the ProxyConnection property of a ConnectionInfo object. This allows for specification of multiple proxies through which to connect.

As SSH requires different configuration compared to other proxy types, create new sub-interfaces of the IConnectionInfo interface.

Update tests to reflect new interface.

[JoostJM]

Related to #852.

[JoostJM]

A number of tests appear to be failing due to issues with the 8122 port used in tests. It looks like that port is already being used in AppVeyor. Commit 8f0da78 seems to fix this for most of the Connection tests, but the error occurs more often throughout the other tests.

[JoostJM]

Fixed failing tests. All changes in testing were due to the following reasons:

• Many of the tests used port 8122 to simulate connections, either by setting up a listener or expecting it to fail due to no listener on that port. However, port 8122 is already bound on appveyor, which causes either the listener to be unable to bind the socket, or producing an unexpected result in other tests, as the socket can be connected to.
  • This error is fixed by either using dynamic port assignment, or using port 8121.
• Timeout test set the timeout to a random small number. However, when testing proxy timeout, this should also be set on the ProxyConnectionInfo, which is a new object defined in this PR to allow connecting through multiple proxies.
  • This error is fixed by setting the timeout of proxyconnections to the same small value assigned to the connection info objects.
• The new interface requires a service factory object to be passed to the constructor of connector objects, allowing these objects to instantiate proxyconnector objects. In testing, these objects are replaced by Mock<> objects.
  • This error is fixed by implementing Mock<> objects for ServiceFactory where required.

[jophippe]

Hi, I'm testing this PR to merge it into the Visual Studio fork of SSH.NET, and I'm running into a hanging issue. I'm using this code:

var connectionInfo = new ConnectionInfo(Destination, 22, "root", ProxyTypes.Ssh,
    new ConnectionInfo(Proxy, "admin", new PasswordAuthenticationMethod("admin", Password)),
    new PasswordAuthenticationMethod("root", Password));

using (var client = new SftpClient(connectionInfo))
{
    client.Connect();
    var dirs = client.ListDirectory("/");
    foreach (var dir in dirs)
    {
        Console.WriteLine(dir.FullName);
    }
    client.Disconnect();
}

and the program hangs on the client.Connect() line. When I debug, it looks like the Session creates an SshConnector, then the SshConnector creates a Session, then that Session creates an SshConnector, and that SshConnector creates a Session, and so on until the AuthenticationConnection check causes the program to hang. Is there something I'm doing wrong?

[JoostJM]

@jophippe, My apologies. The updates I implemented to make it fit better with the more recent changes to SSH net introduced a bug. Before, I instantiated the connector by also passing the proxy connection info to the constructor (and used it there to instantiate the proxy session required for the jump). In the update, I moved that part to the Connect function, but forgot to use the ProxyConnectionInfo, using the ConnectionInfo instead (pointing to the ultimate destination). This caused an infinite recursion, as each instantiation of the Session tries to make a new SSH Connector. I fixed the error now.

[benrobot]

Any progress on this pull request? I would like to start using this feature.

[JoostJM]

This PR is/was ready for merging, but pending a review by @drieseng. I use it myself by checking out this branch. All checks passed.

[WojciechNagorski]

@JoostJM Amazing job! As soon as we release the .NET Standard version I'll want to test this PR. However, the branch needs to merge with the master because there are many conflicts.

[WojciechNagorski]

I will review this PR. This feature would be great for next version. But you should merge this PR to develop branch, not the master. The best option for you will be to create a new PR from the develop branch.

[JoostJM]

I'll merge with the develop branch as well. First I still need to finish up reviewing the merges of the tests (source code merge with master is done).

[JoostJM]

@WojciechNagorski, the merge with develop is complete. Besides the new features, this also contains some adjustments to the tests, removing the use of port 8122 as much as possible (using dynamic assignment of ports), and using 8121 elsewhere.
I implemented this as in the past, I ran into issues with tests in appveyor (it was already using port 8122 for something else).