[Bug] Hard crash when using key based authentication with SSH version 8.8p1

[ghost]

Hard crash when connecting to a remarkable tablet profile that uses
SSH key authentication (not password authentication which works just fine).

I assume that's due to my version of SSH being >= 8.8. See https://remarkablewiki.com/tech/ssh
at the bottom of the page for confirmation and a workaround.

Reproduce on any GNU/Linux distribution (I'm using the latest Fedora) by:

• adding a profile that uses an SSH key
• running a version of SSH greater than or equal to 8.8 on that machine

To get a shell from the command line I had to change some settings in my $HOME/.ssh/config file which let me
connect just fine. For reference here's what I had to add to my config:

Host *
        PubkeyAcceptedKeyTypes +ssh-rsa
        HostKeyAlgorithms +ssh-rsa

And here's the logs:

Unhandled exception. Renci.SshNet.Common.SshException: openssh key type: ssh-rsa is not supported
   at Renci.SshNet.PrivateKeyFile.ParseOpenSshV1Key(Byte[] keyFileData, String passPhrase)
   at Renci.SshNet.PrivateKeyFile.Open(Stream privateKey, String passPhrase)
   at Renci.SshNet.PrivateKeyFile..ctor(Stream privateKey)
   at Slithin.Models.LoginInfo.GetKey() in /home/runner/work/Slithin/Slithin/Source/Slithin/Models/#Info.cs:line 28
   at Slithin.ViewModels.ConnectionWindowViewModel.Connect(Object obj) in /home/runner/work/Slithin/Slithin/Source/Slithin/ViewModels/ConnectWindowViewModel.cs:line 138
   at Slithin.Core.MVVM.DelegateCommand.Execute(Object parameter) in /home/runner/work/Slithin/Slithin/Source/Libraries/Slithin.Core/MVVM/DelegateCommand.cs:line 32
   at Avalonia.Controls.Button.OnClick() in /_/src/Avalonia.Controls/Button.cs:line 321
   at Avalonia.Controls.Button.OnPointerReleased(PointerReleasedEventArgs e) in /_/src/Avalonia.Controls/Button.cs:line 364
   at Avalonia.Input.InputElement.<>c.<.cctor>b__32_9(InputElement x, PointerReleasedEventArgs e) in /_/src/Avalonia.Input/InputElement.cs:line 223
   at Avalonia.Interactivity.RoutedEvent.<>c__DisplayClass23_0.<AddClassHandler>b__0(ValueTuple`2 args) in /_/src/Avalonia.Interactivity/RoutedEvent.cs:line 94
   at System.Reactive.AnonymousObserver`1.OnNextCore(T value) in /_/Rx.NET/Source/src/System.Reactive/AnonymousObserver.cs:line 67
   at System.Reactive.ObserverBase`1.OnNext(T value) in /_/Rx.NET/Source/src/System.Reactive/ObserverBase.cs:line 36
   at System.Reactive.Subjects.Subject`1.OnNext(T value) in /_/Rx.NET/Source/src/System.Reactive/Subjects/Subject.cs:line 145
   at Avalonia.Interactivity.EventRoute.RaiseEventImpl(RoutedEventArgs e) in /_/src/Avalonia.Interactivity/EventRoute.cs:line 118
   at Avalonia.Interactivity.EventRoute.RaiseEvent(IInteractive source, RoutedEventArgs e) in /_/src/Avalonia.Interactivity/EventRoute.cs:line 79
   at Avalonia.Interactivity.Interactive.RaiseEvent(RoutedEventArgs e) in /_/src/Avalonia.Interactivity/Interactive.cs:line 123
   at Avalonia.Input.MouseDevice.MouseUp(IMouseDevice device, UInt64 timestamp, IInputRoot root, Point p, PointerPointProperties props, KeyModifiers inputModifiers) in /_/src/Avalonia.Input/MouseDevice.cs:line 313
   at Avalonia.Input.MouseDevice.ProcessRawEvent(RawPointerEventArgs e) in /_/src/Avalonia.Input/MouseDevice.cs:line 144
   at Avalonia.Input.InputManager.ProcessInput(RawInputEventArgs e) in /_/src/Avalonia.Input/InputManager.cs:line 37
   at Avalonia.RawEventGrouper.DispatchFromQueue() in /_/src/Shared/RawEventGrouping.cs:line 56
   at Avalonia.Threading.JobRunner.RunJobs(Nullable`1 priority) in /_/src/Avalonia.Base/Threading/JobRunner.cs:line 37
   at Avalonia.X11.X11PlatformThreading.HandleX11(CancellationToken cancellationToken) in /_/src/Avalonia.X11/X11PlatformThreading.cs:line 169
   at Avalonia.X11.X11PlatformThreading.RunLoop(CancellationToken cancellationToken) in /_/src/Avalonia.X11/X11PlatformThreading.cs:line 245
   at Avalonia.Threading.Dispatcher.MainLoop(CancellationToken cancellationToken) in /_/src/Avalonia.Base/Threading/Dispatcher.cs:line 65
   at Avalonia.Controls.ApplicationLifetimes.ClassicDesktopStyleApplicationLifetime.Start(String[] args) in /_/src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs:line 120
   at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime[T](T builder, String[] args, ShutdownMode shutdownMode) in /_/src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs:line 209
   at Slithin.Program.Main(String[] args) in /home/runner/work/Slithin/Slithin/Source/Slithin/Program.cs:line 21
Aborted (core dumped)

I would have submitted a fix as a pull request since it seems like all we'd need to do is pass some configuration options to
SSH.NET to allow for that key format but I'm unfamiliar with cross platform C# development and won't have time to attempt
a fix until the weekend.

[furesoft]

Do you know if the problem only exists on linux or also on windows?

[ghost]

I could not reproduce the error on windows 10 or on debian buster (oldstable not current) however the output of ssh -V on windows returned:

OpenSSH_for_Windows_7.7p1

so I believe that once they integrate version 8 where that key type was deprecated the bug will surface again unless rsa keys of the type Remarkable tablets support are manually enabled in Slithin's codebase.

[PhilT]

Could be this. Some additional params need to passed to OpenSSH

OpenSSH 8.8 ssh-rsa problem
simonschllng/rm-sync#10