Manually Add Exception Table Entry?

Apr 8, 2014

because of the need to implement a certain software watermarking technique I have to manipulate the exception table.
 
(Link to the paper that describes the technique: [URL] .... (Section "Extension to Java Bytecode")
   
So far I could manually add the exception table entry with Javassist:
 
MethodInfo minfo = (MethodInfo) aclasscf.getMethods().get(0);
CodeAttribute ca = minfo.getCodeAttribute();
ExceptionTable et = ca.getExceptionTable();

[Code]....

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Manually Adding Exception Table Entry

Apr 7, 2014

I use Javassist to manually add a exception table entry:

Java Code:

MethodInfo minfo = (MethodInfo) aclasscf.getMethods().get(0);
CodeAttribute ca = minfo.getCodeAttribute();
ExceptionTable et = ca.getExceptionTable();
et.add(26, 30, 40, 0);
System.out.println("exception table size: " + et.size()); mh_sh_highlight_all('java');

If I get the bytecode with javap it seems to work:

Java Code:

Exception Table
from to target type
26 30 40 any mh_sh_highlight_all('java');

But the problem is that I can't run the file anymore. Simply running it with the java command results in "java.lang.VerifyError: Expecting a stackmap frame at branch target 40". After some research this seems to be a problem with java 7 and a stricter verifier. I read several times that java -XX:-UseSplitVerifier should be used instead.

This really fixed the stackmap error, but then another error appeared: "java.lang.VerifyError: (class: AClass, method: signature: ()V) Inconsistent stack height 2 != 1". Are there any further steps required to insert a new exception in the exception table?

Additional info: Later I want to remove gotos (in this case the goto at line 27) and add a function call instead. When this function finishes it will throw a exception and propagate it back to the caller (which will be at line 27). Then the program should go on as if nothing happend, that is also the reason why the target of the exception is the same as the target of the goto (40)

Here is the bytecode:

Java Code:

0: aload_0
1: invokespecial #8 // Method java/lang/Object."<init>":()V
4: iconst_0
5: istore_1
6: goto 19
9: getstatic #10 // Field java/lang/System.out:Ljava/io/PrintStream;
12: iload_1
13: invokevirtual #16 // Method java/io/PrintStream.println:(I)V

[Code] .....

Exception table:
from to target type
26 30 40 any mh_sh_highlight_all('java');

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Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at GUI.QC_receiving_book.printButtonActionPerformed(QC_receiving_book.java:309)
at GUI.QC_receiving_book.access$600(QC_receiving_book.java:26)
at GUI.QC_receiving_book$7.actionPerformed(QC_receiving_book.java:165)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)

[Code] ....

I tried avoiding the null exception by using the if statement but it didn't work. The row I choose from the table is full meaning there are no empty attributes. and all the data are imported from a mysql database to the table as String so there can't be any casting errors.

This is the part of the source code with the problem and i will also post the printing method. I tried debugging the class and when stepping into the first if statement it opened the jTable.java file and pointed at the getSelectedRow() method and this sentence "variable information not available.source compiled without -g option"

private void printButtonActionPerformed(java.awt.event.ActionEvent evt) {
if(samplesTable.getSelectedRow() >= 0){
int row = samplesTable.getSelectedRow();
System.out.println(row);
for(int x=0;x<samplesTable.getColumnCount();x++){
String value = samplesTable.getModel().getValueAt(row, x).toString();

[Code] ....

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I am new to programming in regards to I/O, channels, SSH, etc...

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I was thinking that maybe I have to use some other InputStream object at line 77 when setting the channels input stream instead of System.in, but I am not sure how to do this (but really I'm not sure if I'm even on the right tracks?). I believe all this confusion may be down to a misunderstanding with the general concepts involved with channels and I/O ...

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How To Manually Put Data Into InputStream

Aug 23, 2014

I am trying to transform the Shell.java program from the JCraft JSch examples : [URL] ....

The way in which I am trying to transform it is by instead of having the character input go into the channel automatically from the keyboard (refer to line 77 in Shell.java), I just want to pro-grammatically insert characters in to the channel at my discretion, so for example I have a string called unixCommand that I want to insert into the channel, and I don't want there to be any other way of inserting into the channel such as the standard input stream, so for example I'd have the statement <insert unixCommand to UNIX box at other side of channel> inserted somewhere after line 100 in Shell.java.

I was thinking that maybe I have to use some other InputStream object at line 77 when setting the channels input stream instead of System.in, but I am not sure how to do this (but really I'm not sure if I'm even on the right tracks?). I believe all this confusion may be down to a misunderstanding with the general concepts involved with channels and I/O.

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<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.5"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_5.xsd">
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<servlet>

[code]....

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I have a JSF application with this code in the xhtml page:

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<f:selectItems value="#{mybean.products}" />
</h:selectOneListbox>

and the corresponding snippets of the Java code are:

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// ...
private String product;
private ArrayList<String> productValues;
private ArrayList<String> productLabels;
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public String getLocation() { // Displayed on a page

[code]....

Most of this works correctly using only ArrayList SelectItem products without the two ArrayList and the separate SelectItem[], and the values and labels are put directly into products here. The menu works and I can select an item. However, I am unable to find the correct method for finding the index in the submit method,namely:

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I have problem with manually (through my java code) selecting items in a JTree. I did Google the problem and found solutions here :

[URL]

This code worked for me only partially. Once I tried selecting deeper nested nodes, I ran into problems. Since my production code is very cluttered I built an example and reproduced my exact problem in it.

DummyView.java
package de.fortis.tcws.client.controller;
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

[code].....

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Java Code:

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[declarations here]
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[Code] .....

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public class PayrollDemo
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[Code] ....

And this is the exception class.

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