B4J Question [SOLVED] How to run a .jar without a wrapper?

JackKirk · Oct 13, 2019

This thread:
https://www.b4x.com/android/forum/t...h-additionaljar-and-javaobject-picasso.40904/

Seems to explain how you can run a .jar without it being wrapped (i.e. in a library) - for B4A only.

Does anyone know of any example on the forums of how to do it for B4J?

I've searched everywhere without success.

Thanks in anticipation...

DonManfred · Oct 13, 2019

it is the same for b4j. Use javaobject.

JackKirk · Oct 13, 2019

DonManfred said:
it is the same for b4j. Use javaobject.

DonManfred,

It might be the same to you but I am java illiterate - I need a fully spelt out example for B4J that accesses a jar.

Specifically what I want to do is access the jB4XEncryption jar without going through the library.

Your next question will be why? in which case see:
https://www.b4x.com/android/forum/threads/solved-obfuscating-of-library-methods.110448/

Thanks for your interest...

DonManfred · Oct 13, 2019

JackKirk said:
Specifically what I want to do is access the jB4XEncryption jar without going through the library.

The source is available here: https://github.com/AnywhereSoftware...nywheresoftware/b4x/object/B4XEncryption.java
You can see what the library is doing with the bouncy castle...

JackKirk · Oct 13, 2019

DonManfred said:
The source is available here: https://github.com/AnywhereSoftware...nywheresoftware/b4x/object/B4XEncryption.java
You can see what the library is doing with the bouncy castle...

Don Manfred,

I'm not interested in how it works - I can make it do what I want just fine.

If you look at the post I refer to above, namely:
https://www.b4x.com/android/forum/threads/solved-obfuscating-of-library-methods.110448/

you'll see what I am chasing - a way to make hackers work a bit harder.

Do you know of any full B4J examples of accessing a jar via javaobject?

Thanks...

DonManfred · Oct 13, 2019

JackKirk said:
Do you know of any full B4J examples of accessing a jar via javaobject?

No. I never use javaobject. I usually write a wrapper in java using eclipse if i need access to a java library.

But here is one

B4X:

#Region Project Attributes
    #MainFormWidth: 600
    #MainFormHeight: 600
#End Region

#AdditionalJar: jbcrypt-0.4

Sub Process_Globals
    Private fx As JFX
    Private MainForm As Form
End Sub

Sub AppStart (Form1 As Form, Args() As String)
    MainForm = Form1
    'MainForm.RootPane.LoadLayout("Layout1") 'Load the layout file.
    MainForm.Show
    
    Dim bc As JavaObject = GetBCrypt
    Dim saltstr As String = bc.RunMethod("gensalt",Null)
    Dim hashedpw As String = bc.RunMethod("hashpw",Array("Test :-)",saltstr))
    Log("HashedPassword="&hashedpw)
End Sub
Sub GetBCrypt As JavaObject
    Dim jo As JavaObject
    Return jo.InitializeStatic("org.mindrot.jbcrypt.BCrypt")
End Sub
Sub GetContext As JavaObject
    Return GetBA.GetField("context")
End Sub

Sub GetBA As JavaObject
    Dim jo As JavaObject
    Dim cls As String = Me
    cls = cls.SubString("class ".Length)
    jo.InitializeStatic(cls)
    Return jo.GetFieldJO("processBA")
End Sub
'Return true to allow the default exceptions handler to handle the uncaught exception.
Sub Application_Error (Error As Exception, StackTrace As String) As Boolean
    Return True
End Sub

JackKirk · Oct 13, 2019

Don Manfred,

Ah, that's the sort of code I'm looking for.

Now to really show my ignorance, can you explain how the string "org.mindrot.jbcrypt.BCrypt" is arrived at - if I google it it takes me to the github project but I don't see that string anywhere.

DonManfred · Oct 13, 2019

It is the classname in java notation.

Looking into jbcrypt jar from above (rename to.zip) you find a structure
org\
mindrot\
jbcrypt\
and here you find the BCrypt.class

It is a good help if you know some java

JackKirk · Oct 13, 2019

DonManfred said:
Looking into jbcrypt jar from above (rename to.zip) you find a structure

Digging through the jbcrypt-0.4.jar you gave at post #6 - I worked this out about 30 seconds before your email arrived

DonManfred said:
It is a good help if you know some java

As I said I'm java illiterate - and Objective C too - but I normally can work out what I need to do if I can find a good enough template - which I think you have now supplied.

Many thanks for your perseverance...

PS I'm off to bed now - I may have more questions tomorrow when I try to implement this.

JackKirk · Oct 14, 2019

Don Manfred,

Your example code can be simplified to:

B4X:

#Region Project Attributes
    #MainFormWidth: 600
    #MainFormHeight: 600
#End Region

#AdditionalJar: jbcrypt-0.4

Sub Process_Globals
    Private fx As JFX
    Private MainForm As Form
End Sub

Sub AppStart (Form1 As Form, Args() As String)
    MainForm = Form1
    'MainForm.RootPane.LoadLayout("Layout1") 'Load the layout file.
    MainForm.Show

    Dim bc As JavaObject
    bc = bc.InitializeStatic("org.mindrot.jbcrypt.BCrypt")

    Dim saltstr As String = bc.RunMethod("gensalt",Null)
    Dim hashedpw As String = bc.RunMethod("hashpw",Array("Test :-)",saltstr))
    Log("HashedPassword="&hashedpw)
End Sub

'Return true to allow the default exceptions handler to handle the uncaught exception.
Sub Application_Error (Error As Exception, StackTrace As String) As Boolean
    Return True
End Sub

The GetContext and GetBA subroutines are never used and the GetBCrypt subroutine can be replaced as indicated.

BUT...

When I modify this simplified code to try to drive jB4XEncryption:

B4X:

#Region Project Attributes
    #MainFormWidth: 600
    #MainFormHeight: 600
#End Region

'#AdditionalJar: jbcrypt-0.4
#AdditionalJar: bcprov-jdk15on-159
#AdditionalJar: jB4XEncryption

Sub Process_Globals
    Private fx As JFX
    Private MainForm As Form
End Sub

Sub AppStart (Form1 As Form, Args() As String)
    MainForm = Form1
    'MainForm.RootPane.LoadLayout("Layout1") 'Load the layout file.
    MainForm.Show

'    Dim bc As JavaObject
'    bc = bc.InitializeStatic("org.mindrot.jbcrypt.BCrypt")

'    Dim saltstr As String = bc.RunMethod("gensalt",Null)
'    Dim hashedpw As String = bc.RunMethod("hashpw",Array("Test :-)",saltstr))
'    Log("HashedPassword="&hashedpw)

    Private wrk_hexstr As String = "377B68B781B99388E6BE69E62AFA4145E660F4DFB81627CF9C2D969D403C0D1DC401A1B4841F90002533231A7555A9ACD238DBA3022BF74D"
 
    Private Obj_bytehandler As ByteConverter
 
    Private wrk_bytes() As Byte = Obj_bytehandler.HexToBytes(wrk_hexstr)

    Private wrk_jo As JavaObject
    wrk_jo = wrk_jo.InitializeStatic("anywheresoftware.b4x.object.B4XEncryption")

    wrk_bytes = wrk_jo.RunMethod("Decrypt", Array(wrk_bytes, "sneaky"))
 
    'Should produce AKIAZZZZZZZZZZZZZZZZ
    Log(BytesToString(wrk_bytes, 0, wrk_bytes.Length, "UTF8"))

End Sub

'Return true to allow the default exceptions handler to handle the uncaught exception.
Sub Application_Error (Error As Exception, StackTrace As String) As Boolean
    Return True
End Sub

I get:

Error occurred on line: 36 (Main)
java.lang.IllegalArgumentException: object is not an instance of declaring class
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at anywheresoftware.b4j.object.JavaObject.RunMethod(JavaObject.java:132)
at b4j.example.main._appstart(main.java:106)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at anywheresoftware.b4a.shell.Shell.runMethod(Shell.java:632)
at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:237)
at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:167)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:91)
at anywheresoftware.b4a.shell.ShellBA.raiseEvent2(ShellBA.java:98)
at anywheresoftware.b4a.BA.raiseEvent(BA.java:78)
at b4j.example.main.start(main.java:38)
at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:919)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$11(PlatformImpl.java:449)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$9(PlatformImpl.java:418)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:417)
at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:175)
at java.base/java.lang.Thread.run(Thread.java:844)

Where line 36 is:

wrk_bytes = wrk_jo.RunMethod("Decrypt", Array(wrk_bytes, "sneaky"))

Any ideas?

DonManfred · Oct 14, 2019

B4XEncryption is´nt static

try https://www.b4x.com/android/help/javaobject.html#javaobject_initializenewinstance

JackKirk · Oct 14, 2019

Don Manfred,

You are my java magician - works like a charm.

For anyone who is interested, the final code looks like:

B4X:

#Region Project Attributes
    #MainFormWidth: 600
    #MainFormHeight: 600
#End Region

#AdditionalJar: bcprov-jdk15on-159
#AdditionalJar: jB4XEncryption

Sub Process_Globals
    Private fx As JFX
    Private MainForm As Form
End Sub

Sub AppStart (Form1 As Form, Args() As String)
    MainForm = Form1
    'MainForm.RootPane.LoadLayout("Layout1") 'Load the layout file.
    MainForm.Show

    Private wrk_hexstr As String = "377B68B781B99388E6BE69E62AFA4145E660F4DFB81627CF9C2D969D403C0D1DC401A1B4841F90002533231A7555A9ACD238DBA3022BF74D"
    
    Private Obj_bytehandler As ByteConverter
    
    Private wrk_bytes() As Byte = Obj_bytehandler.HexToBytes(wrk_hexstr)

    Private wrk_jo As JavaObject
    wrk_jo = wrk_jo.InitializeNewInstance("anywheresoftware.b4x.object.B4XEncryption", Null)

    wrk_bytes = wrk_jo.RunMethod("Decrypt", Array(wrk_bytes, "sneaky"))
    
    'Should produce AKIAZZZZZZZZZZZZZZZZ
    Log(BytesToString(wrk_bytes, 0, wrk_bytes.Length, "UTF8"))

End Sub

'Return true to allow the default exceptions handler to handle the uncaught exception.
Sub Application_Error (Error As Exception, StackTrace As String) As Boolean
    Return True
End Sub

JackKirk · Oct 15, 2019

Don Manfred,

Now the dust has settled I'm in a reflective mood.

On thing is nagging me - why is the jbcrypt-0.4 jar "static" and the jB4XEncryption jar isn't?

And how could you tell?

And what does "static" mean anyrate?

Regards...

DonManfred · Oct 15, 2019

From the code. The class only contains static methods.

B4X:

public class BCrypt {
[...]
   public static String hashpw(String password, String salt) {

JackKirk said:
nd what does "static" mean anyrate?

No idea. I suggest to buy a java book.

For any further question please create a new thread.

B4J Question [SOLVED] How to run a .jar without a wrapper?

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