[QUESTION] - Passive mode with custom provided TcpStream

[markhaehnel]

Hi, i'm trying to connect to a FTP server over a SOCKS5 proxy. Connecting works fine.

I just connect with FtpStream::connect_with_stream(stream.into_inner())? where stream is my SOCKS5 TcpStream.

The problem is now: In passive mode, when i want to retrieve a file, the connection to the server is not done via the proxy (provided TcpStream). It instantiates a new TcpStream internally.

Is there a way to achieve connecting over a custom provided TcpStream when doing retr_as_stream?

Best regards, Mark

[veeso]

Hi,

I'm not sure how it should work though. The TcpStream is instantiated using the addr returned by pasv, so how can you know the address prior to this? If you could provide more details with a full flow it would be great for me to understand exactly how it should be implemented.

[markhaehnel]

The current flow is as follows:

let stream = Socks5Stream::connect("localhost:1080", address)?;
let mut client = FtpStream::connect_with_stream(stream.into_inner())?;

client.set_mode(Mode::Passive);
client.login(username, password)?;

let mut file_to_write = std::fs::File::create(format!("dl/{}", filename))?;
let mut retr_stream = client.retr_as_stream(filename)?;
std::io::copy(&mut retr_stream, &mut file_to_write)?;
client.finalize_retr_stream(retr_stream)?;

client.quit()?;

For solving this my idea would be that one could provide a optional function that creates a TcpStream for the client. Kind of like this:

let stream = Socks5Stream::connect("localhost:1080", address)?;
let mut client = FtpStream::connect_with_stream(stream.into_inner())?;

client.stream_builder(|address| {
    let stream = TcpStream::connect(address)?;
    Ok(stream)

    // or if you want to use a socks5 proxy
    let stream = Socks5Stream::connect("localhost:1080", address)?;
    Ok(stream.into_inner())
});

client.set_mode(Mode::Passive);
client.login(username, password)?;

let mut file_to_write = std::fs::File::create(format!("dl/{}", filename))?;
let mut retr_stream = client.retr_as_stream(filename)?;
std::io::copy(&mut retr_stream, &mut file_to_write)?;
client.finalize_retr_stream(retr_stream)?;

client.quit()?;

This function would be called whenever the client needs to create a new TcpStream for the data connection. For example here.

What do you think of this?

BTW, i would be happy to provide the implementation in a PR once we agree on a solution.

[veeso]

I guess it could work. I'll try to implement this.

[markhaehnel]

Mind if I submit a Pull Request with my proposed changes?

[veeso]

I actually was already implementing it 😅

[markhaehnel]

No problem, go on! 😄