Swift compiler as a library: obfuscator case

Presented during Mobile Warsaw meetup on 22nd of May 2018

Transcript

1. Swift compiler as a library: 
 obfuscator case Krzysztof Siejkowski
2. In software development, obfuscation is the deliberate act of creating source or machine code that is difficult for humans to understand — Wikipedia
3. App Store YourApp binary file Your source code
4. App Store YourApp binary file YourApp encrypted (FairPlay) Jailbroken device YourApp binary file Your source code
5. App Store YourApp binary file YourApp encrypted (FairPlay) YourApp decrypted (in memory) Memory dump tool YourApp binary file Jailbroken device YourApp binary file Your source code
6. App Store YourApp binary file YourApp encrypted (FairPlay) YourApp decrypted (in memory) Memory dump tool YourApp binary file Your source code Disassembler (Hopper) Assembly/pseudo-code Jailbroken device
7. App Store YourApp binary file YourApp encrypted (FairPlay) YourApp decrypted (in memory) Memory dump tool YourApp binary file Your source code Disassembler (Hopper) Assembly/pseudo-code Jailbroken device
12. class MyViewController: UIViewController {} class MyView: UIView {} class MyModel: NSManagedObject {} class MyRuntimeUsingObject: NSObject {} class SomeClass { @objc func someFunc() {} }
13. Obfuscation is more than symbol renaming 
 Code Obfuscation Techniques for Software Protection
 —PhD thesis by Jan Cappaert
 

14. How to obfuscate? • after compilation • during compilation • before compilation
15. After compilation: binary to binary iXGuard (https://www.guardsquare.com/en/ixguard)
16. During compilation: source to binary Obfuscator-LLVM (https://github.com/obfuscator-llvm/obfuscator)
17. Before compilation: source to source WE!!!
18. Goal: obfuscate Swift code 
 by renaming
21. Does it work?
22. Does it work? YES
23. Not universal tool… • no DSYM support • no multiple targets • no mixed Swift/Obj-C • not all Swift constructs supported
24. …but still powerful • Storyboards/XIBs renaming • various Swift expressions supported • excluding configuration • very easy to integrate
25. $ bin/sirius -help USAGE: sirius -projectrootpath [PROJECTROOTPATH] -obfuscatedproject [OBFUSCATEDPROJECTPATH]
26. Xcode project Zobfuskowany Xcode project Command line interface (standalone or as Xcode build step) Original Xcode project Obfuscated Xcode project (copy or inplace)
27. Original Xcode project Xcode project parsing Symbols identification Generation of new names Obfuscated Xcode project (copy or inplace) Renaming in the source files
28. Original Xcode project Xcode project parsing
29. Original Xcode project Xcode project parsing Symbols identification
30. Original Xcode project Xcode project parsing Symbols identification Generation of new names
31. Original Xcode project Xcode project parsing Symbols identification Generation of new names Obfuscated Xcode project Renaming in the source files
32. Obfuscation verification Original Xcode project Xcode project parsing Symbols identification Generation of new names Obfuscated Xcode project Renaming in the source files Main command line interface
33. Obfuscation verification Original Xcode project Xcode project parsing Obfuscated Xcode project Main command line interface Swift compiler Symbols identification Generation of new names Renaming in the source files
42. 1. create new folder in swift/tools
 2. add add_swift_tool_subdirectory function 
 to swift/tools/CMakeLists.txt
 3. create new .cpp file with main function 
 4. create new CMakeLists.txt for your tool
 5. add add_swift_host_tool function 
 to swift/tools/<your-tool>/CMakeLists.txt 
 and define the source files, executable name and dependencies How to add new command line tool?
50. 1. create new folders in swift/include/swift and swift/lib
 2. add your .h interfaces 
 to swift/include/swift/<your-library>
 3. add your .cpp implementations to swift/lib/<your-library>
 4. create CMakeLists.txt for your library 
 at swift/lib/<your-library>/CMakeLists.txt 
 with add_swift_library function 
 that defines the source files, library name and dependencies
 5. add add_subdirectory function to swift/lib/CMakeLists.txt 
 How to add new library?
56. 1. create new folder in swift/unittests
 2. add your .cpp test source code 
 to swift/unittests/<your-library>
 3. create CMakeLists.txt for your unit tests
 at swift/unittests/<your-library>/CMakeLists.txt 
 with add_swift_unittest function that 
 defines the source files, executable name and dependencies
 4. add add_subdirectory call to swift/unittests/CMakeLists.txt 
 How to add unit tests?
59. 1. create tool in swift/tools/<your-tool>
 2. (not required, but a good idea) create library 
 for the underlying logic 
 in swift/include/swift/<your-library> 
 and swift/lib/<your-library>
 3. add unit tests to swift/unittests/<your-library>
 4. add integration tests to swift/tests/<your-tool>
 How to create new compiler-based tool?
61. Abstract 
 Syntax 
 Tree
62. CompilerInstance Compiler; CompilerInvocation Invocation; Invocation.setModuleName(ModuleName); Invocation.setMainExecutablePath(MainExecutablePath); for (const auto &InputFilename : InputFilenames) { Invocation.addInputFilename(InputFilename); } Invocation.setFrameworkSearchPaths(FrameworkPaths); Invocation.setSDKPath(SdkPath); Invocation.setTargetTriple(Triple); if (Compiler.setup(Invocation)) { return stringError("Error during compiler setup"); } Compiler.performSema();
63. class SymbolsWalker : public SourceEntityWalker { bool visitDeclReference(ValueDecl *, CharSourceRange, TypeDecl *, ExtensionDecl *, Type, ReferenceMetaData) override; } for (auto* Unit : Compiler.getMainModule() ->getFiles()) { if (auto* Current = dyn_cast<SourceFile>(Unit)) { SymbolsWalker Walker; Walker.walk(&Current); } }
64. ParamDecl *Parameter = //given from SourceEntityWalker auto Name = Parameter ->getName().str().str(); CharSourceRange Range(Parameter ->getNameLoc(), Name.length());
65. auto &SourceManager = Current ->getASTContext().SourceMgr; auto BufferId = Current ->getBufferID().getValue();
 std ::error_code Error; llvm ::raw_fd_ostream DescriptorStream(Path, Error, F_None); SourceEditOutputConsumer Editor(SourceManager, 
 BufferId, DescriptorStream);
 
 CharSourceRange Range = // computed slide ago auto ReplacingString = // replacement for range in code Editor ->ide ::SourceEditConsumer ::accept(SourceManager, Range, ReplacingString);
67. static llvm ::cl ::opt<std ::string> SymbolsJsonPath("symbolsjson", llvm ::cl ::desc("Name of the file containing extracted symbols"), llvm ::cl ::cat(ObfuscatorNameMapper)); int main(int argc, char *argv[]) { INITIALIZE_LLVM(argc, argv); llvm ::cl ::ParseCommandLineOptions(argc, argv, “obfuscator-name-mapper");
68. void MappingTraits<SymbolsJson> :: mapping(IO &Io, SymbolsJson &Object) { Io.mapRequired("symbols", Object.Symbols); } Input Input(JsonString); SymbolsJson Symbols; Input >> Symbols;
69. • LLVM Programmer’s Manual 
 (http://llvm.org/docs/ProgrammersManual.html) 
 • LLVM Coding Standards 
 (http://llvm.org/docs/CodingStandards.html) • many more!
70. 1. Get familiar with C++11 Few last practical tips
71. 1. Get familiar with C++11
 2. Use Xcode as IDE (works really well!) Few last practical tips
72. 1. Get familiar with C++11
 2. Use Xcode as IDE (works really well!)
 3. Keep Swift compiler in sync 
 with Xcode version Few last practical tips
73. 1. Get familiar with C++11
 2. Use Xcode as IDE (works really well!)
 3. Keep Swift compiler in sync 
 with Xcode version
 4. Don’t let the lack of compiler knowledge 
 scare you away! Few last practical tips
75. Pros Cons Anything compiler can do, you can do too!
76. Pros Cons Anything compiler can do, you can do too! Compiler libs are designed for compilation, not for your tool
77. Pros Cons Anything compiler can do, you can do too! Compiler libs are designed for compilation, not for your tool So many tools are available!
78. Pros Cons Anything compiler can do, you can do too! Compiler libs are designed for compilation, not for your tool So many tools are available! No stable API, breaking changes all the time
79. Pros Cons Anything compiler can do, you can do too! Compiler libs are designed for compilation, not for your tool So many tools are available! No stable API, breaking changes all the time You can leverage 
 the existing infrastructure
80. Pros Cons Anything compiler can do, you can do too! Compiler libs are designed for compilation, not for your tool So many tools are available! No stable API, breaking changes all the time You can leverage 
 the existing infrastructure You must fit into 
 the existing infrastructure
81. Pros Cons Anything compiler can do, you can do too! Compiler libs are designed for compilation, not for your tool So many tools are available! No stable API, breaking changes all the time You can leverage 
 the existing infrastructure You must fit into 
 the existing infrastructure Support for both 
 Swift and Objective-C
82. Pros Cons Anything compiler can do, you can do too! Compiler libs are designed for compilation, not for your tool So many tools are available! No stable API, breaking changes all the time You can leverage 
 the existing infrastructure You must fit into 
 the existing infrastructure Support for both 
 Swift and Objective-C There might be better alternatives
83. Alternatives • libSyntax • SourceKit • existing swift tools
85. • https://github.com/PolideaPlayground/ SiriusObfuscator-SymbolExtractorAndRenamer 
 • Documentation folder has a lot of notes 
 on various implementation decisions, 
 with details and motivation
87. @KacperHarasim
88. Questions? @_siejkowski
89. Thank you!