ssh login throwing error

[john bean]

hi im trying to log into a server on local network with code

public class MainActivity extends AppCompatActivity {



            public void run() {
               try {
                    // Connection establishment and authentication
                    try (ClientSession session = client.connect("med1a", "192.168.1.2",port).verify(10000).getSession()) {//error thrown from here
                        session.addPasswordIdentity("2servman");
                        session.auth().verify(50000);
                        Toast toast=Toast.makeText(getApplicationContext(),"connected", Toast.LENGTH_SHORT);
                        toast.setMargin(50,50);
                        toast.show();
                        System.out.println("Connection establihed");

                        // Create a channel to communicate
                        channel = session.createChannel(Channel.CHANNEL_SHELL);
                        System.out.println("Starting shell");

                        ByteArrayOutputStream responseStream = new ByteArrayOutputStream();
                        channel.setOut(responseStream);

                        // Open channel
                        channel.open().verify(5, TimeUnit.SECONDS);
                        try (OutputStream pipedIn = channel.getInvertedIn()) {
                            pipedIn.write(command.getBytes());
                            pipedIn.flush();
                        }

                        // Close channel
                        channel.waitFor(EnumSet.of(ClientChannelEvent.CLOSED),
                                TimeUnit.SECONDS.toMillis(5));

                        // Output after converting to string type
                        String responseString = new String(responseStream.toByteArray());
                        System.out.println(responseString);
                       // shellOutput.setText(responseString);

                    } catch (IOException e) {
                        e.printStackTrace();
                    } finally {
                        client.stop();
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }

        });
       thread.start();



    
}

but is throwing the error when i try to connect

2022-01-26 19:44:22.891 24926-24926/com.example.remote2 D/AndroidRuntime: Shutting down VM
2022-01-26 19:44:22.900 24926-24926/com.example.remote2 E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.remote2, PID: 24926
    java.lang.ExceptionInInitializerError
        at org.apache.sshd.common.config.keys.IdentityUtils$LazyDefaultUserHomeFolderHolder.access$000(IdentityUtils.java:48)
        at org.apache.sshd.common.config.keys.IdentityUtils.getUserHomeFolder(IdentityUtils.java:64)
        at org.apache.sshd.common.config.keys.PublicKeyEntry$LazyDefaultKeysFolderHolder.<clinit>(PublicKeyEntry.java:271)
        at org.apache.sshd.common.config.keys.PublicKeyEntry$LazyDefaultKeysFolderHolder.access$000(PublicKeyEntry.java:269)
        at org.apache.sshd.common.config.keys.PublicKeyEntry.getDefaultKeysFolderPath(PublicKeyEntry.java:284)
        at org.apache.sshd.client.config.hosts.HostConfigEntry$LazyDefaultConfigFileHolder.<clinit>(HostConfigEntry.java:109)
        at org.apache.sshd.client.config.hosts.HostConfigEntry$LazyDefaultConfigFileHolder.access$000(HostConfigEntry.java:107)
        at org.apache.sshd.client.config.hosts.HostConfigEntry.getDefaultHostConfigFile(HostConfigEntry.java:1156)
        at org.apache.sshd.client.config.hosts.DefaultConfigFileHostEntryResolver.<init>(DefaultConfigFileHostEntryResolver.java:51)
        at org.apache.sshd.client.config.hosts.DefaultConfigFileHostEntryResolver.<clinit>(DefaultConfigFileHostEntryResolver.java:40)
        at org.apache.sshd.client.ClientBuilder.<clinit>(ClientBuilder.java:68)
        at org.apache.sshd.client.ClientBuilder.builder(ClientBuilder.java:171)
        at org.apache.sshd.client.SshClient.setUpDefaultClient(SshClient.java:773)
        at com.example.remote2.MainActivity.launchclient(MainActivity.java:52)
        at com.example.remote2.MainActivity$1.onClick(MainActivity.java:119)
        at android.view.View.performClick(View.java:6617)
        at android.view.View.performClickInternal(View.java:6594)
        at android.view.View.access$3100(View.java:778)
        at android.view.View$PerformClick.run(View.java:25906)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6723)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:495)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
     Caused by: java.lang.IllegalArgumentException: No user home
        at org.apache.sshd.common.util.ValidateUtils.$r8$lambda$1D3Pm1dHguhozQI_dpJQD8NBElg(Unknown Source:2)
        at org.apache.sshd.common.util.ValidateUtils$$ExternalSyntheticLambda0.apply(Unknown Source:2)
        at org.apache.sshd.common.util.ValidateUtils.createFormattedException(ValidateUtils.java:213)
        at org.apache.sshd.common.util.ValidateUtils.throwIllegalArgumentException(ValidateUtils.java:179)
        at org.apache.sshd.common.util.ValidateUtils.checkTrue(ValidateUtils.java:156)
        at org.apache.sshd.common.util.ValidateUtils.checkNotNullAndNotEmpty(ValidateUtils.java:56)
        at org.apache.sshd.common.config.keys.IdentityUtils$LazyDefaultUserHomeFolderHolder.<clinit>(IdentityUtils.java:50)
        at org.apache.sshd.common.config.keys.IdentityUtils$LazyDefaultUserHomeFolderHolder.access$000(IdentityUtils.java:48) 
        at org.apache.sshd.common.config.keys.IdentityUtils.getUserHomeFolder(IdentityUtils.java:64) 
        at org.apache.sshd.common.config.keys.PublicKeyEntry$LazyDefaultKeysFolderHolder.<clinit>(PublicKeyEntry.java:271) 
        at org.apache.sshd.common.config.keys.PublicKeyEntry$LazyDefaultKeysFolderHolder.access$000(PublicKeyEntry.java:269) 
        at org.apache.sshd.common.config.keys.PublicKeyEntry.getDefaultKeysFolderPath(PublicKeyEntry.java:284) 
        at org.apache.sshd.client.config.hosts.HostConfigEntry$LazyDefaultConfigFileHolder.<clinit>(HostConfigEntry.java:109) 
        at org.apache.sshd.client.config.hosts.HostConfigEntry$LazyDefaultConfigFileHolder.access$000(HostConfigEntry.java:107) 
        at org.apache.sshd.client.config.hosts.HostConfigEntry.getDefaultHostConfigFile(HostConfigEntry.java:1156) 
        at org.apache.sshd.client.config.hosts.DefaultConfigFileHostEntryResolver.<init>(DefaultConfigFileHostEntryResolver.java:51) 
        at org.apache.sshd.client.config.hosts.DefaultConfigFileHostEntryResolver.<clinit>(DefaultConfigFileHostEntryResolver.java:40) 
        at org.apache.sshd.client.ClientBuilder.<clinit>(ClientBuilder.java:68) 
        at org.apache.sshd.client.ClientBuilder.builder(ClientBuilder.java:171) 
        at org.apache.sshd.client.SshClient.setUpDefaultClient(SshClient.java:773) 
        at com.example.remote2.MainActivity.launchclient(MainActivity.java:52) 
        at com.example.remote2.MainActivity$1.onClick(MainActivity.java:119) 
        at android.view.View.performClick(View.java:6617) 
        at android.view.View.performClickInternal(View.java:6594) 
        at android.view.View.access$3100(View.java:778) 
        at android.view.View$PerformClick.run(View.java:25906) 
        at android.os.Handler.handleCallback(Handler.java:873) 
        at android.os.Handler.dispatchMessage(Handler.java:99) 
        at android.os.Looper.loop(Looper.java:193) 
        at android.app.ActivityThread.main(ActivityThread.java:6723) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:495) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858) 
2022-01-26 19:44:22.920 24926-24926/com.example.remote2 I/Process: Sending signal. PID: 24926 SIG: 9

anyone know what is causing this any help for a noob would be great thanks

[Rob Spoor]

john bean wrote:

     Caused by: java.lang.IllegalArgumentException: No user home

Can you login manually as the same user? I doubt it, because I get a feeling that you're trying to connect using a system account. Those aren't meant to be used to login as, not locally and not remotely.

[Tim Holloway]

Rob Spoor wrote:

john bean wrote:

     Caused by: java.lang.IllegalArgumentException: No user home

Can you login manually as the same user? I doubt it, because I get a feeling that you're trying to connect using a system account. Those aren't meant to be used to login as, not locally and not remotely.

I concur. I'm pretty sure that the real meaning of that message is "No home directory defined for that user on the ssh server".

[Ron McLeod]

It appears like the problem is that it did not find a property for the (client) user's home directory (maybe it is needed to look for something under its .ssh directory).

In org.apache.sshd.common.config.keys.IdentityUtils:

private static final Path PATH
		= Paths.get(ValidateUtils.checkNotNullAndNotEmpty(System.getProperty("user.home"), "No user home"))
				.toAbsolutePath()
				.normalize();

[Tim Holloway]

Ron McLeod wrote:It appears like the problem is that it did not find a property for the (client) user's home directory (maybe it is needed to look for something under its .ssh directory).

Allowing for whatever funny business systemd has been up to lately, the remote user's home directory is defined in /etc/passwd and attached to that user's specific login ID, regardless of whether it's a local or remote login. An SSH client can immediately cd somewhere else, if it's set up properly as part of the ssh login process, but I think that there does have to be a fixed initial home defined on the server.

[Ron McLeod]

This failure is occurring on the client side, before any network interaction with the server.

My guess would be that the client implementation wants to look for the remote endpoint's public key which is normally stored in ~/.ssh/known_hosts, so it first needs a path the home directory.

Also, the OP's code is running on Android - I'm not sure where ssh information is stored in that case.

[Tim Holloway]

Android is built on top of Linux, so if you had root access, you probably would find the ingfrastructure there. Although since Android itself is a VM, like the regular JVM I wouldn't guarantee that that would be its one and only key registration database.

In any event, a known-hosts entry is created only when a remote client has successfully negotiated with a server and confirmed its identity.  The known-hosts file merely pairs the returned server key to its dial-in address (hostname or IP) and doesn't even carry user information. That part goes in the ssh authorized_keys file IF you copy a key from the server (using ssh-copy-id or similar).

So in short, I can see no reason for the client to know or care about either the client or the server's home directory. It's only the server that should be dealing with that.

Ergo, first, I'd check the user account definition on the server. If that checked out (and specifically if you could log in OK from a non-Android client), I'd check to make sure that the app wasn't using a library that's not actually Android-friendly.

[Rob Spoor]

I agree with both of you. I'd first check if you can actually login as this user before trying to fix the code. But Ron appears be right that the .ssh folder is missing. That means that the private key and known hosts need to be configured in a different way.

[Tim Holloway]

Rob Spoor wrote:But Ron appears be right that the .ssh folder is missing.

What bothers me about that is that Android's philosphy isn't filesystem-based as a rule. Most mutable storage is in databases.

As for alternate storage in the abstract, consider PuTTY for Windows. I actually have no idea where it keeps its host keys. Windows, after all doesn't support SSH natively (or PuTTY wouldn't have been created), and the idea of a hidden SSH folder isn't part of the standard Windows paradigm. Although for the most part, when mimicking Unix networking constructs Windows does tend to follow Unix.

[Rob Spoor]

Tim Holloway wrote:As for alternate storage in the abstract, consider PuTTY for Windows. I actually have no idea where it keeps its host keys. Windows, after all doesn't support SSH natively (or PuTTY wouldn't have been created), and the idea of a hidden SSH folder isn't part of the standard Windows paradigm. Although for the most part, when mimicking Unix networking constructs Windows does tend to follow Unix.

Where else but in the Windows Registry, under key HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\SshHostKeys. I had to check the about dialog to find the key under Software.

[Tim Holloway]

Thus, PuTTY needs no user home directory (or .ssh/known hosts).

[Rob Spoor]

No, it uses the registry for all of its storage. It also use a file ~\AppData\Local\PUTTY.RND, but that's probably easily replacable.