Ssh-rs panic on a thread when using in multi threading

[Paulo-21]

Hello,
I had an issue with your library.
One thread panic when i use more threads than i have physical cores.
When i use Available parallelism from the rust standard library, i got 12 cores.
I precise that my cpu have 8 cores without hyper threading and 2 physical cores with Hyper Threading.
So 10 physical core without hyper threading.

When i set the number of threads to 10, no crash happen but when i increase the number of threads to 11 or 12 then it crash.

i m just running n threads and running ssh inside of each one.

thread '<unnamed>' panicked at C:\Users\Username\.cargo\registry\src\index.crates.io-6f17d22bba15001f\ssh-rs-0.4.1\src\config\version.rs:36:17:
assertion `left == right` failed
  left: [69, 120, 99, 101]
 right: [83, 83, 72, 45]
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[HsuJv]

Hi,

May I have a copy of your PoC code?

It looks strange cuz this assert is only to test the first 4 bytes of the ssh server replies when we connected.
According to the RFC, it must be "SSH-xxxxxx", which in ASCII is [83, 83, 72, 45, xxxxx]

A fatal here is that we shall throw an error rather than panic. But if you're connecting a true ssh server, it is worth investigating more about how could it happen.

BRs.

[Paulo-21]

Hi, thank you for your help.
Ssh Server : OpenSSH_8.9p1

PoC

use ssh;
use std::thread::{self, JoinHandle};
use std::thread::available_parallelism;
fn main() {
    //let default_parallelism_approx = available_parallelism().unwrap().get();
    let default_parallelism_approx = 11;
    let mut threads = Vec::<JoinHandle<()>>::new();
    for i in 0..default_parallelism_approx {
        let mut start = i;
        let e = thread::spawn(move || {
            let session_name = "Admin";
	    let password = "12345678";
            while start < 10000 {
                let connection = ssh::create_session()
                .username(&session_name)
                .password(&password)
                .connect("wwww.website.com:22");

        }
        });
        threads.push(e);
    }
    for _u in 0..default_parallelism_approx {
        let r = threads.pop().unwrap();
        let _ = r.join();
    }
}

[HsuJv]

Hi @Paulo-21

With #78 it now returns an error SshError::VersionDismatchError rather than panic.

It's actually some error message which indicates that the server is not able to handle more clients.

thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: VersionDismatchError { our: "SSH-2.0-SSH_RS-0.4.1", their: "Exceeded MaxStartups" }', exec/src/main.rs:38:18
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: VersionDismatchError { our: "SSH-2.0-SSH_RS-0.4.1", their: "Exceeded MaxStartups" }', exec/src/main.rs:38:18
thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: VersionDismatchError { our: "SSH-2.0-SSH_RS-0.4.1", their: "Exceeded MaxStartups" }', exec/src/main.rs:38:18
thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: VersionDismatchError { our: "SSH-2.0-SSH_RS-0.4.1", their: "Exceeded MaxStartups" }', exec/src/main.rs:38:18

I'll later have 0.4.2 released to include the fix.

Thank you for reporting!

BRs.

[Paulo-21]

Hi @HsuJv
Thank you for your reactivity.