Java Virtual Machine (Obfuscation and Java)

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Java Virtual Machine(Obfuscation and Java)

• ??????? ?????????
• 2004

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What it is all about?

• ????????? Java
• Classfile
• ??????????? ???
• ????????? ? ????????? ??????
• ????????? ??????? ?????? ????-????
• ?????????? ? Java
• QA

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Java Technology(????????)

• Java ?????????? ?????? SUN Microsystems
• 1991 ?. James Gosling ???? Oak
• 1995 ?. ????????? ???????? ?? JAVA ? ??????
  ?????? ?????????? - JDK 1.0
• 1998 ?. ????????? Java 2 ( SE, EE, ME)
• Java ???
• ?????????
• ?????????
• ???????????
• ????????-??????????????

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What is this all for?
SMART HOUSE
EMBEDDED MEDICAL SYSTEM
WEB SERVER
VM
DESKTOP
CELLPHONE
H.JAR
PALM
SMARTPHONE
iPAQ
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???? ???? ? JAVA
Compiler (javac)
a.java
a.class
Obfuscator
JAR (jar) ZIP
b. class
b.java
External Verifier
b.java
b. class
H.JAR
Compiler (other)
e.other
e.class
Manifest.mf
f.png
g.txt
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OOP (JIC)
Moveable
2DPoint Pos
SetPosition()
ValidatePos()
Figure
Draw()
SetColor()
ValidatePos()
ValidatePos()
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CLASS FILE
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Classfile structure(?????????)

• ??????????? ?????????? Java ???????????????? ?
  ???? ?????? classfile-?? (??? ?? ??????? JAR)
• ???????????? ????????? JAVA
• ????????????
• ?????? ??????????????????????
• ??????? ??????????
• ???????????? ???????? ??????????? ???????????

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Classfile structure(????????)

• ?????? classfile ???????????? ?????? ??????
  ?????? ??? ??????????
• ?? ?? ?????? ????????? ??????? ?????? ?
  ????????????? ????????????? ?????? ?????? ???
  ??????????
• Classfile ??? ????????? ???????????????????
  ????? ???? (big-endian)
• ?? ???????????? ??????? classfile ??? ??????
  ??????

Classfile
JAVA
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Classfile structure(??? ????????)

• ??? ????????
• ??? ?????? (??????, ???????????? ???)
• ?????? ?? ?????-?????? (??????????)
• ????? ?????????????? ???????????
• ???????? ?????
• ???????? ?????
• ???????? ???????
• ???????? ???????
• ???????? ?????????

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Classfile structure(??????????? ???)

• ????? ??????? ??????????? ????????? ?????? ???
  ?????????? ? ???????? ???????? ?? ????
• ???????? ????? ????????? ?????????? ?????????
• ??????
• ????????? (int, float, long, double, ?????? UTF8)
• ?????? ?? ????????????? ???????? ??????? ????????
  (???????, ???????, ???????)
• ???????????? ?????? ????????? 216
• ??????????? ??? ????????? ? ???????? ??????????

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??????
CONSTANT_Methodref_info
CONSTANT_Class_info
COCONSTANT_NameAndType_info
CONSTANT_Utf8_info
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Attributes

• SourceFile - ???????? ?????????
• ConstantValue ???????? ?????????
• Code ???????? ????
• Exceptions ?????? ?????????? ???????? ???????
• InnerClasses ?????? ????????? ??????? ?? ??????
  ???????
• Synthetic ??????? ? ??? ??? ???? ??????
  ???????????? ? ?????????
• LineNumberTable ?????? ?????? ?? ?????? ?????
• LocalVariableTable ?????? ???? ?????????
  ??????????
• Deprecated ??????? ? ??? ??? ???? ??? ?????
  ???????? (??????????)

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Methods and attributes
attribute_info      u2 attribute_name_index
     u4 attribute_length      u1
infoattribute_length     
Code_attribute      u2 attribute_name_index
     u4 attribute_length      u2 max_stack
     u2 max_locals      u4 code_length     
u1 codecode_length      u2
exception_table_length      u2 start_pc
     u2 end_pc      u2 handler_pc      u2
catch_type      exception_tableexception_tabl
e_length u2 attributes_count     
attribute_info attributesattributes_count
    
method_info   u2 access_flags      u2
name_index      u2 descriptor_index      u2
attributes_count      attribute_info
attributesattributes_count     
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JVM
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???????????? JVM

• ? ???? ??????? ????????? ????
• ?? ????????? ????

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JVM Subsystems
?????????
???????? ?????
???? ????? ?????
????? ??????????? ????????????
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JVM (????????? JAVA ??????)

• ???????????????
• ????????? ??????????
• ?????? ??????????? ?????? ??????????? ?? ???????
  ?? ???????
• ?????????????? ?????? ??????
• ??????? ??????????????? ??????????????

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JVM (????????? JAVA ??????)

• JVM ?????????? ???????? ?????? ? ??????????
  ???????????
• ?????? ????? ? JVM ????? ???? ???? ?????
  ??????????? ????????
• JVM ????????? ?
• ?????? ????????? (??????? ????????)
• ?????????? ??????????? ???????????
• ???????????? ???????????

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JVM
Runtime constpool
Thread 1
Thread 2
JVM Op Stack
Local Variables
Parameters
Frame3
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JVM
FRAME STACK (call stack)
Thread 1
Thread 2
ALU
MEMORY
FRAME2
JVM Op Stack
HEAP
FRAME2
FRAME1
FRAME1
FRAME1
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BYTE code(?????????)

• ???????? ????? ????? ? 8 ??? ? ???????????
  ???????
• ???????? ????? ????????? ????????? ????????????
• ???? ????????? ????????
• ???? ??????? ? ??????? ???????? (IS ???????????)
• ?? ????? ???????????
• ?????? ???????? ? ??????? ???????? 8, 32, 64 ????

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BYTE code(???? ??????)

• byte - 8-bit ???????? ?????
• short - 16-bit ???????? ?????
• int - 32-bit ???????? ?????
• long - 64-bit ???????? ?????
• char - 16-bit ??? ???????? ??? ?????????????
  UNICODE
• float
• double

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BYTE code(????)

• ?????? ? ???????????
• Push ????-????
• ?????????? ? ???????? ????????? ??????????
• Pop ????-???? ? ?????? ?? ??????
• ?????????????? ????????
• ???????? ????????? ? ???????? ?????????, ????????
  ???????, ???????? ???????? ?? ???????
• ???????? ???????????? ????????
• ???????? ???????? ??????????? ? ????????????
  ?????
• ???????? ????? ????????, ????????, ????????
  ?????????? ?????
• ?????? ??????????
• ?????? ? ???????????? ?????????
• ??????? ???????? ?? ????
• ??????? ???????? ? ??????? ????????

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Size reduction
iconst_m1
push (byte)-1
n if (x lt 9 x gt 3) then x 3 else
OTHER_OPCODE push (byte)n
iconst_n
bipush
push x
sipush
push x
ldc
push CONST_POOLx
ldc_w
push CONST_POOLx
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Vierifier

• invoke virtual
• ????? ?????? ???? ????? ?????? ??? ?????? ??????.
  
• ? ??? ?????????
• verifier
• ? runtime

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JIT

• Pros vs Cons
• Time 2x-40x faster
• Memory Overhead 5x-10x
• Compilation
• JIT Just-In-Time
• AOT Ahead-Of-Time
• HI Hotspot Implementations

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Garbage collection(????? ?????)

• ????? ? ??????? ??????????? ?????????????
• ? ????????? ??????? ??? ??? ???????????
• ??? ????? ???? ??????????? ??????... ??????
  ??????? ??? ????
• ??????????? ???? ?????? ? ?????? ?????? ? ???...
• ???? ???????????? ?????????? ??? ?????????????,
  ???? ??? ????????????? ???????????? ? ??????
  ??????

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Obfuscation
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Obfuscation and Java

• Pros
• ??? ?? ????? ???? ??????????
• Java ?????? ????? ?????????????
• ?????????? ???????? ?????
• Cons
• Reflection ????? ???????? ???????
• ????????? Java ?????? ??????????

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Decompilers

• Goto
• ?????? ????? for ? synchronized ? ????-????
  ?? ?? ?????? ????? ??????? ? Java
• ??? ???????? ????????, ???? ?? ?? ???????. ??????
  ????? ? ????? ?? ????????????, ???? ??? ??????????

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Decompilers
? ?????? ??? ???? ?????????????.
b a a b
int tmp tmp a a b b tmp
iload_0 iload_1 istore_0 istore_1
iload_0 istore_2 iload_1 istore_0 iload_2 istore_1

???????????
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Obfuscation - Names and profiles (Retroguard)

• GNU GPL
• ??????????

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Names and profiles (JODE)

• GNU GPL
• ?????????????? ???????, ??????? ? ?????
• ???????? ?????????? ??????????
• ???????? ???????? ???? (???????, ???????,
  ?????)
• ??????????? ????????? ????????? ??????????
• ???? ????????????

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Names and profiles (SandMark)

• ?????? ??????????? ???????????? ?????????
  watermarking, tamper-proofing ? code obfuscation
• ??????? ?? ?????????? by Venkatesan, Collberg,
  Stern, and others

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Names and profiles (DashO)

• Commercial
• Suns choice
• Features
• Package/Class/Method/Field renaming using our
  patented Overload-Induction(tm) renaming system
• Unused Class/Method/Field and constant pool entry
  removal
• Advanced Control Flow Obfuscation
• String Encryption
• Class and method level optimization to improve
  JIT performance

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Names and profiles
???????? ???? (name mangling) ????????? ?????? ????????? (code mangling) ??????????? ????? (strings enscription)
Retroguard ?
SandMark ? ?
DashO
JODE ?
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Where is more information available?

• ????????????? ?????????? ? Java ?????? ??????????
  ? ???????????? SUN ? ?????? ???? ???
• http//sunsite.nstu.ru/java-stuff/vmspec/
• ?????????? ? ?????????? ? classfile
• ftp//ftp.cs.arizona.edu/reports/2004/TR04-11.pdf
• ????????? ???????????
• http//www.retrologic.com/retroguard-docs.html
• http//sandmark.cs.arizona.edu/publications.html
• http//www.preemptive.com/products/dasho/Features.
  html

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THE END

• ??????? ?? ????????

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Q A

• ?????? ?????? ?????