File transfer over ssh via scp and sftp

1. File transfer over ssh via scp and sftp A two second dirty example

2. Jsch • Limited documentation, but seems pretty good • Get jar file from http://www.jcraft.com/jsch/ • Examples: http://www.jcraft.com/jsch/examples/ • Documentionhttp://show.docjava.com/book/cgij/jdoc/net/ssh/jsch/JSch.html (or search for jsch doc) • To use, add the jar file to the set of external libraries in eclipse • Jsch requires a couple of classes to be implemented • UserInfo

3. UserInfo • UserInfo • User info contains user names and passwords • The online examples show how to make a dialog box appear to get the user name and password. However, these examples don’t work on android. • By hardcoding, we can skip using UserInfo

4. HostKeyRepository • Ssh stores the keys of machines it has previously communicated with. This avoids man-in-the-middle attacks • Jsch uses the class HostKeyRepository to decide how to store and retrieve keys • A hardcoded example is as follows • Add • MyHostKeyRepositorymyHostKeyRepository = new MyHostKeyRepository(); • class MyHostKeyRepository implements HostKeyRepository{}; • Let eclipse make required functions • Go to getHostKeyand add • byte[] key = new byte[16]; • String[] keyStr = {"ae","71","c6","56","fa","38","76","65","3c","ad","e8","8d","a1","71","00","23"}; • for(inti=0; i<keyStr.length; i++) • key[i] = Byte.parseByte(keyStr[i], 16); • HostKey[] hk = new HostKey[1]; • try { • hk[0] = new HostKey("128.4.35.59",key); • } catch (JSchException e) { • e.printStackTrace(); • } • return hk; • However, you must set the keyStr to be the key of the machine you will communicate with. • Sometimes this key is given in various config information. • You can get the key by running the program with the above, incorrect key. • The android log will show you an error and show the correct key. • Get that key string and put it into the code above

5. File transfer with sftp • class MyRunnable implements Runnable { • int _arg; // this can be some argument, but we skip using arguments in this simple exmaple • MyRunnable(intarg) { • _arg = arg; • } • @Override • public void run() { • moveFile(arg); • } • } • public void moveFile() { // since the file transfer will take some time, we must put the file transfer in a separate thread. • MyRunnablemyrunnable = new MyRunnable(0); • new Thread(myrunnable).start(); • } • public void moveFileWithSFTP { • String user = “user"; // user name • String host = "128.4.1.45"; // machine name could be a string that is resolved with dns • String sfile= “filename.txt"; // file to move • String dfile = “filename.txt”; // name of destination file • JSchjsch=new JSch(); • jsch.setHostKeyRepository(myHostKeyRepository); • Session session; • session = jsch.getSession(user, host, 22); • session.setPassword(“password"); // hard coded password.. Use UserInfo to improve • session.connect(); • if(!session.isConnected()) { • Log.e("sch",“connect failed"); • session.disconnect(); • return; • } • Log.e("sch","connected"); • channel=session.openChannel("sftp"); • channel.connect(); • ChannelSftp c=(ChannelSftp)channel; • c.put(sfile,dfile,ChannelSftp.OVERWRITE); • if (((SftpATTRS)c.stat("LocationTracker.txt")).getSize()==(new File(lfile)).length()) { • Log.e("sfpt","success"); • } else { • Log.e("sfpt","file transfer faield"); • } • Log.e("sftp","done"); // this line is run only after the transfer finishes • channel.disconnect(); • session.disconnect(); • }