0.2.4 changes

ChangeLog.md

@@ -1,3 +1,6 @@
+* [0.2.4](https://github.com/mwiede/jsch/releases/tag/jsch-0.2.4)
+  * When connections fail due to an algorithm negotiation failure, throw a `JSchAlgoNegoFailException` that extends `JSchException`.
+    * The new `JSchAlgoNegoFailException` details which specific algorithm negotiation failed, along with what both JSch and the server proposed.
 * [0.2.3](https://github.com/mwiede/jsch/releases/tag/jsch-0.2.3)
   * #188 fix private key length checks for ssh-ed25519 & ssh-ed448. by @norrisjeremy in https://github.com/mwiede/jsch/pull/189
 * [0.2.2](https://github.com/mwiede/jsch/releases/tag/jsch-0.2.2)

examples/JumpHosts.java

@@ -0,0 +1,168 @@
+/* -*-mode:java; c-basic-offset:2; indent-tabs-mode:nil -*- */
+/**
+ * This program will demonstrate SSH through jump hosts.
+ * Suppose that you don't have direct accesses to host2 and host3.
+ *   $ CLASSPATH=.:../build javac JumpHosts.java
+ *   $ CLASSPATH=.:../build java JumpHosts usr1@host1 usr2@host2 usr3@host3
+ * You will be asked passwords for those destinations,
+ * and if everything works fine, you will get file lists of your home-directory
+ * at host3.
+ *
+ */
+import com.jcraft.jsch.*;
+import java.awt.*;
+import javax.swing.*;
+
+public class JumpHosts {
+  public static void main(String[] arg){
+
+    try{
+      JSch jsch = new JSch();
+
+      if(arg.length <= 1){
+        System.out.println("This program expects more arguments.");
+        System.exit(-1);
+      }
+
+      Session session = null;
+      Session[] sessions = new Session[arg.length];
+
+      String host = arg[0];
+      String user = host.substring(0, host.indexOf('@'));
+      host = host.substring(host.indexOf('@')+1);
+
+      sessions[0] = session = jsch.getSession(user, host, 22);
+      session.setUserInfo(new MyUserInfo());
+      session.connect();
+      System.out.println("The session has been established to "+user+"@"+host);
+
+      for(int i = 1; i < arg.length; i++){
+        host = arg[i];
+        user = host.substring(0, host.indexOf('@'));
+        host = host.substring(host.indexOf('@')+1);
+
+        int assinged_port = session.setPortForwardingL(0, host, 22);
+        System.out.println("portforwarding: "+
+                           "localhost:"+assinged_port+" -> "+host+":"+22);
+        sessions[i] = session =
+          jsch.getSession(user, "127.0.0.1", assinged_port);
+
+        session.setUserInfo(new MyUserInfo());
+        session.setHostKeyAlias(host);
+        session.connect();
+        System.out.println("The session has been established to "+
+                           user+"@"+host);
+      }
+
+      ChannelSftp sftp = (ChannelSftp)session.openChannel("sftp");
+
+      sftp.connect();
+      sftp.ls(".",
+              new ChannelSftp.LsEntrySelector() {
+                public int select(ChannelSftp.LsEntry le) {
+                  System.out.println(le);
+                  return ChannelSftp.LsEntrySelector.CONTINUE;
+                }
+              });
+      sftp.disconnect();
+
+      for(int i = sessions.length-1; i >= 0; i--){
+        sessions[i].disconnect();
+      }
+    }
+    catch(Exception e){
+      System.out.println(e);
+    }
+  }
+
+  public static class MyUserInfo implements UserInfo, UIKeyboardInteractive{
+    public String getPassword(){ return passwd; }
+    public boolean promptYesNo(String str){
+      Object[] options={ "yes", "no" };
+      int foo=JOptionPane.showOptionDialog(null,
+             str,
+             "Warning",
+             JOptionPane.DEFAULT_OPTION,
+             JOptionPane.WARNING_MESSAGE,
+             null, options, options[0]);
+       return foo==0;
+    }
+
+    String passwd;
+    JTextField passwordField=(JTextField)new JPasswordField(20);
+
+    public String getPassphrase(){ return null; }
+    public boolean promptPassphrase(String message){ return true; }
+    public boolean promptPassword(String message){
+      Object[] ob={passwordField};
+      int result=
+          JOptionPane.showConfirmDialog(null, ob, message,
+                                        JOptionPane.OK_CANCEL_OPTION);
+      if(result==JOptionPane.OK_OPTION){
+        passwd=passwordField.getText();
+        return true;
+      }
+      else{ return false; }
+    }
+    public void showMessage(String message){
+      JOptionPane.showMessageDialog(null, message);
+    }
+    final GridBagConstraints gbc =
+      new GridBagConstraints(0,0,1,1,1,1,
+                             GridBagConstraints.NORTHWEST,
+                             GridBagConstraints.NONE,
+                             new Insets(0,0,0,0),0,0);
+    private Container panel;
+    public String[] promptKeyboardInteractive(String destination,
+                                              String name,
+                                              String instruction,
+                                              String[] prompt,
+                                              boolean[] echo){
+      panel = new JPanel();
+      panel.setLayout(new GridBagLayout());
+
+      gbc.weightx = 1.0;
+      gbc.gridwidth = GridBagConstraints.REMAINDER;
+      gbc.gridx = 0;
+      panel.add(new JLabel(instruction), gbc);
+      gbc.gridy++;
+
+      gbc.gridwidth = GridBagConstraints.RELATIVE;
+
+      JTextField[] texts=new JTextField[prompt.length];
+      for(int i=0; i<prompt.length; i++){
+        gbc.fill = GridBagConstraints.NONE;
+        gbc.gridx = 0;
+        gbc.weightx = 1;
+        panel.add(new JLabel(prompt[i]),gbc);
+
+        gbc.gridx = 1;
+        gbc.fill = GridBagConstraints.HORIZONTAL;
+        gbc.weighty = 1;
+        if(echo[i]){
+          texts[i]=new JTextField(20);
+        }
+        else{
+          texts[i]=new JPasswordField(20);
+        }
+        panel.add(texts[i], gbc);
+        gbc.gridy++;
+      }
+
+      if(JOptionPane.showConfirmDialog(null, panel,
+                                       destination+": "+name,
+                                       JOptionPane.OK_CANCEL_OPTION,
+                                       JOptionPane.QUESTION_MESSAGE)
+         ==JOptionPane.OK_OPTION){
+        String[] response=new String[prompt.length];
+        for(int i=0; i<prompt.length; i++){
+          response[i]=texts[i].getText();
+        }
+        return response;
+      }
+      else{
+        return null;  // cancel
+      }
+    }
+  }
+}

pom.xml

@@ -165,7 +165,7 @@
         <dependency>
             <groupId>ch.qos.logback</groupId>
             <artifactId>logback-classic</artifactId>
-            <version>1.3.0-beta0</version>
+            <version>1.3.0</version>
             <scope>test</scope>
         </dependency>
         <dependency>
@@ -177,7 +177,7 @@
         <dependency>
             <groupId>org.scalatest</groupId>
             <artifactId>scalatest_2.13</artifactId>
-            <version>3.2.12</version>
+            <version>3.2.13</version>
             <scope>test</scope>
             <exclusions>
                 <exclusion>
@@ -610,7 +610,7 @@
                                 <path>
                                     <groupId>com.google.errorprone</groupId>
                                     <artifactId>error_prone_core</artifactId>
-                                    <version>2.13.1</version>
+                                    <version>2.15.0</version>
                                 </path>
                             </annotationProcessorPaths>
                         </configuration>

src/main/java/com/jcraft/jsch/JSchAlgoNegoFailException.java

@@ -0,0 +1,69 @@
+package com.jcraft.jsch;
+
+/**
+ * Extension of {@link JSchException} to indicate when a connection fails during algorithm
+ * negotiation.
+ */
+public class JSchAlgoNegoFailException extends JSchException {
+
+  private static final long serialVersionUID = -1L;
+
+  private final String algorithmName;
+  private final String jschProposal;
+  private final String serverProposal;
+
+  JSchAlgoNegoFailException(int algorithmIndex, String jschProposal, String serverProposal) {
+    super(failString(algorithmIndex, jschProposal, serverProposal));
+    algorithmName = algorithmNameFromIndex(algorithmIndex);
+    this.jschProposal = jschProposal;
+    this.serverProposal = serverProposal;
+  }
+
+  /** Get the algorithm name. */
+  public String getAlgorithmName() {
+    return algorithmName;
+  }
+
+  /** Get the JSch algorithm proposal. */
+  public String getJSchProposal() {
+    return jschProposal;
+  }
+
+  /** Get the server algorithm proposal. */
+  public String getServerProposal() {
+    return serverProposal;
+  }
+
+  private static String failString(int algorithmIndex, String jschProposal, String serverProposal) {
+    return String.format(
+        "Algorithm negotiation fail: algorithmName=\"%s\" jschProposal=\"%s\" serverProposal=\"%s\"",
+        algorithmNameFromIndex(algorithmIndex), jschProposal, serverProposal);
+  }
+
+  private static String algorithmNameFromIndex(int algorithmIndex) {
+    switch (algorithmIndex) {
+      case KeyExchange.PROPOSAL_KEX_ALGS:
+        return "kex";
+      case KeyExchange.PROPOSAL_SERVER_HOST_KEY_ALGS:
+        return "server_host_key";
+      case KeyExchange.PROPOSAL_ENC_ALGS_CTOS:
+        return "cipher.c2s";
+      case KeyExchange.PROPOSAL_ENC_ALGS_STOC:
+        return "cipher.s2c";
+      case KeyExchange.PROPOSAL_MAC_ALGS_CTOS:
+        return "mac.c2s";
+      case KeyExchange.PROPOSAL_MAC_ALGS_STOC:
+        return "mac.s2c";
+      case KeyExchange.PROPOSAL_COMP_ALGS_CTOS:
+        return "compression.c2s";
+      case KeyExchange.PROPOSAL_COMP_ALGS_STOC:
+        return "compression.s2c";
+      case KeyExchange.PROPOSAL_LANG_CTOS:
+        return "lang.c2s";
+      case KeyExchange.PROPOSAL_LANG_STOC:
+        return "lang.s2c";
+      default:
+        return "";
+    }
+  }
+}

src/main/java/com/jcraft/jsch/KeyExchange.java

@@ -123,13 +123,13 @@ protected static String[] guess(Session session, byte[]I_S, byte[]I_C) throws Ex
       loop:
       while(j<cp.length){
         while(j<cp.length && cp[j]!=',')j++; 
-        if(k==j) return null;
+        if(k==j) throw new JSchAlgoNegoFailException(i, Util.byte2str(cp), Util.byte2str(sp));
         String algorithm=Util.byte2str(cp, k, j-k);
         int l=0;
         int m=0;
         while(l<sp.length){
           while(l<sp.length && sp[l]!=',')l++; 
-          if(m==l) return null;
+          if(m==l) throw new JSchAlgoNegoFailException(i, Util.byte2str(cp), Util.byte2str(sp));
           if(algorithm.equals(Util.byte2str(sp, m, l-m))){
             guess[i]=algorithm;
             break loop;
@@ -144,7 +144,7 @@ protected static String[] guess(Session session, byte[]I_S, byte[]I_C) throws Ex
         guess[i]="";
       }
       else if(guess[i]==null){
-        return null;
+        throw new JSchAlgoNegoFailException(i, Util.byte2str(cp), Util.byte2str(sp));
       }
     }
 

src/main/java/com/jcraft/jsch/Session.java

@@ -600,9 +600,6 @@ private KeyExchange receive_kexinit(Buffer buf) throws Exception {
    }
 
     guess=KeyExchange.guess(this, I_S, I_C);
-    if(guess==null){
-      throw new JSchException("Algorithm negotiation fail");
-    }
 
     if(guess[KeyExchange.PROPOSAL_KEX_ALGS].equals("ext-info-c") ||
        guess[KeyExchange.PROPOSAL_KEX_ALGS].equals("ext-info-s")){