How to run SSH command in android programmatically

Question

I would like to run a simple SSH command like ssh -R 80:localhost:1337 serveo.net , I know there is library jsch to do this , but it will not work without username and password . In my case there is no authentication is required . How can I do this ?

Update When I run the command ssh -R 80:localhost:1337 serveo.net -v, I get the following output

debug1: Server host key: ssh-rsa SHA256:07jcXlJ4SkBnyTmaVnmTpXuBiRx2+Q2adxbttO9gt0M
The authenticity of host 'serveo.net (159.89.214.31)' can't be established.
RSA key fingerprint is SHA256:07jcXlJ4SkBnyTmaVnmTpXuBiRx2+Q2adxbttO9gt0M.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added 'serveo.net,159.89.214.31' (RSA) to the list of known hosts.
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after 134217728 blocks
debug1: Will attempt key: /home/paranoid/.ssh/id_rsa 
debug1: Will attempt key: /home/paranoid/.ssh/id_dsa 
debug1: Will attempt key: /home/paranoid/.ssh/id_ecdsa 
debug1: Will attempt key: /home/paranoid/.ssh/id_ecdsa_sk 
debug1: Will attempt key: /home/paranoid/.ssh/id_ed25519 
debug1: Will attempt key: /home/paranoid/.ssh/id_ed25519_sk 
debug1: Will attempt key: /home/paranoid/.ssh/id_xmss 
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,keyboard-interactive
debug1: Next authentication method: publickey
debug1: Trying private key: /home/paranoid/.ssh/id_rsa
debug1: Trying private key: /home/paranoid/.ssh/id_dsa
debug1: Trying private key: /home/paranoid/.ssh/id_ecdsa
debug1: Trying private key: /home/paranoid/.ssh/id_ecdsa_sk
debug1: Trying private key: /home/paranoid/.ssh/id_ed25519
debug1: Trying private key: /home/paranoid/.ssh/id_ed25519_sk
debug1: Trying private key: /home/paranoid/.ssh/id_xmss
debug1: Next authentication method: keyboard-interactive
debug1: Authentication succeeded (keyboard-interactive).
Authenticated to serveo.net ([159.89.214.31]:22).
debug1: Remote connections from LOCALHOST:80 forwarded to local address localhost:1337
debug1: channel 0: new [client-session]
debug1: Entering interactive session.
debug1: pledge: network
debug1: Sending environment.
debug1: Sending env LC_ADDRESS = en_US.UTF-8
debug1: Sending env LC_NAME = en_US.UTF-8
debug1: Sending env LC_MONETARY = en_US.UTF-8
debug1: Sending env LC_PAPER = en_US.UTF-8
debug1: Sending env LANG = en_US.UTF-8
debug1: Sending env LC_IDENTIFICATION = en_US.UTF-8
debug1: Sending env LC_TELEPHONE = en_US.UTF-8
debug1: Sending env LC_MEASUREMENT = en_US.UTF-8
debug1: Sending env LC_TIME = en_US.UTF-8
debug1: Sending env LC_NUMERIC = en_US.UTF-8
debug1: remote forward success for: listen 80, connect localhost:1337
debug1: All remote forwarding requests processed
Forwarding HTTP traffic from https://vacuus.serveousercontent.com

It also creates known_hosts file inside .ssh folder. The content of known_hosts id following

|1|2K3SBFWPCPqI3poBW2X99LiuP8c=|cqCa7m1e23x1P9UpcUuPac+KKI8= ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDxYGqSKVwJpQD1F0YIhz+bd5lpl7YesKjtrn1QD1RjQcSj724lJdCwlv4J8PcLuFFtlAA8AbGQju7qWdMN9ihdHvRcWf0tSjZ+bzwYkxaCydq4JnCrbvLJPwLFaqV1NdcOzY2NVLuX5CfY8VTHrps49LnO0QpGaavqrbk+wTWDD9MHklNfJ1zSFpQAkSQnSNSYi/M2J3hX7P0G2R7dsUvNov+UgNKpc4n9+Lq5Vmcqjqo2KhFyHP0NseDLpgjaqGJq2Kvit3QowhqZkK4K77AA65CxZjdDfpjwZSuX075F9vNi0IFpFkGJW9KlrXzI4lIzSAjPZBURhUb8nZSiPuzj
|1|F1SIE4/IIEjZPJfHBIx90xnSjSU=|NKCdGqv3SFcGcAqPLvVfuRXI4Ok= ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDxYGqSKVwJpQD1F0YIhz+bd5lpl7YesKjtrn1QD1RjQcSj724lJdCwlv4J8PcLuFFtlAA8AbGQju7qWdMN9ihdHvRcWf0tSjZ+bzwYkxaCydq4JnCrbvLJPwLFaqV1NdcOzY2NVLuX5CfY8VTHrps49LnO0QpGaavqrbk+wTWDD9MHklNfJ1zSFpQAkSQnSNSYi/M2J3hX7P0G2R7dsUvNov+UgNKpc4n9+Lq5Vmcqjqo2KhFyHP0NseDLpgjaqGJq2Kvit3QowhqZkK4K77AA65CxZjdDfpjwZSuX075F9vNi0IFpFkGJW9KlrXzI4lIzSAjPZBURhUb8nZSiPuzj

I would not recommend it but possible serverfault.com/a/627909 — Matthias Wiedemann
– Matthias Wiedemann, Commented Jun 30, 2020 at 18:54
I suggest you run your ssh command with the "-v" flag to print debugging info, then edit your question to include the debugging info from a successful invocation. The whole premise of your question may be incorrect. Ssh may be supplying a username and authenticating without you knowing it. — Kenster
– Kenster, Commented Jul 2, 2020 at 19:55

Kenster · Accepted Answer · 2020-07-06 19:38:34Z

3

+50

Here is an example of using serveo through Jsch. The only real "trick" here seems to be specific to serveo. Serveo won't accept tunnel requests until the session has opened a "shell" or "exec" channel. Serveo uses the shell/exec channel to send status messages to the client. So it's necessary to open a shell or exec channel first, then request the remote forward.

The SSH protocol expects the client to supply a user name to login as. The ssh command line utility defaults to using the local username if you don't supply one. Jsch similarly defaults to using the value of the system property "user.name". Serveo is somewhat unusual in that it'll accept SSH connections from anyone, so you can use whatever name you like. You can let jsch use its default--assuming that works on android--or you can use a hard-coded name like "x" or "foo".

import com.jcraft.jsch.*;

public class App {
    public static void main(String[] arg) {
        JSch.setLogger(new MyLogger());
        JSch jsch = new JSch();
        try {
            final Session session = jsch.getSession("serveo.net");
            session.setHostKeyRepository(new NoSecurityRepo());
            session.connect();

            // Establish a shell channel to receive messages from serveo
            ChannelShell cc = (ChannelShell)session.openChannel("shell");
            cc.setPty(false);
            cc.setInputStream(System.in);
            cc.setOutputStream(System.out);
            cc.setExtOutputStream(System.err);
            cc.connect();

            // Now open a remote forward
            session.setPortForwardingR(null, 80, "localhost", 3000);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private static class MyLogger implements Logger {
        @Override
        public boolean isEnabled(int level) { return true; }
        @Override
        public void log(int level, String message) {
            System.err.printf("%s\t%s%n", level, message);
        }
    }

    /*
     * This implementation of HostKeyRepository is just for demonstration.
     * Every time you use it in production, a kitten dies. Please think of
     * the kittens.
     */
    private static class NoSecurityRepo implements HostKeyRepository {
        @Override
        public int check(String host, byte[] key) { return HostKeyRepository.OK; }
        @Override
        public void add(HostKey hostkey, UserInfo ui) { }
        @Override
        public void remove(String host, String type) { }
        @Override
        public void remove(String host, String type, byte[] key) { }
        @Override
        public String getKnownHostsRepositoryID() { return "NoSecurityRepo"; }
        @Override
        public HostKey[] getHostKey() { return new HostKey[0]; }
        @Override
        public HostKey[] getHostKey(String host, String type) { return new HostKey[0]; }
    }
}

edited Jul 6, 2020 at 19:38

answered Jul 4, 2020 at 18:52

Kenster

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3 Comments

mW3 Over a year ago

Thanks a lot , could you kindly tell me , which version of jsch are u using ? I am still getting 'username' is not given exception.I am trying to run this from android .

mW3 Over a year ago

Hey , Thanks a lot , I was able to figure that out . Now it is doing exactly what I wanted. You helped me a lot . Good day sir

Kenster Over a year ago

Serveo doesn't care what username you use. If you find that you have to supply a username, you can use a hardcoded value like "x" or "foo".

Matthias Wiedemann · Accepted Answer · 2020-07-01 11:15:15Z

0

I don't think, that your ssh command is not using any authentication. Please verify it using verbose out with ssh -v .... I guess it uses publickey with your default key id_rsa from ~/.ssh/id_rsa and the server just accepts any key.

If this is the case, you can do the same using jsch.

final JSch jSch = new JSch();
jSch.addIdentity(idRsaFile);
final Session newSession = jSch.getSession(null, "serveo.net", 22);
newSession.setConfig("PreferredAuthentications", "publickey");
newSession.setConfig("StrictHostKeyChecking", "no");

session.setUserInfo(new UserInfo() {
        @Override
        public String getPassphrase() {
            return null;
        }

        @Override
        public String getPassword() {
            return null;
        }

        @Override
        public boolean promptPassword(String message) {
            return false;
        }

        @Override
        public boolean promptPassphrase(String message) {
            return false;
        }

        @Override
        public boolean promptYesNo(String message) {
            return false;
        }

        @Override
        public void showMessage(String message) {

        }
    });
newSession.connect(connectTimeout);

and then

newSession.setPortForwardingR(...);

answered Jul 1, 2020 at 11:15

Matthias Wiedemann

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1 Comment

mW3 Over a year ago

Thanks for your answer . But in android where is that file located ? By the way I have also checked my pc , Inside .ssh folder there is a file called known_hosts . After running that command that file has value like following ``` |1|JPsTEjrqseCiLxjSr+00Ad6xGMc=|KKxBd62AgPo0sfeezhh8aGsja20= ssh-rsa ......... But in my terminal I get something like debug1: Server host key: ssh-rsa SHA256:07jcXlJ4SkBnyTmaVnmTpXuBiRx2+Q2adxbttO9gt0M I tried to pass that string inside jSch.addIdentity() method , but I get file not found exception.

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