Code Injection from Scratch

Slide 1

Slide 1 text

CODE INJECTION FROM SCRATCH TRY! SWIFT - MARCH 5TH 2016 DANIEL HAIGHT - @DANIEL1OF1

Slide 2

Slide 2 text

class Foo { dynamic //this is suspicious func bar() -> String { return "try! Swift" } }

Slide 3

Slide 3 text

class ViewController: UIViewController { ... let textView = UITextView() let foo = Foo() override func viewDidLoad() { ... self.updateTextViewText() } ... func updateTextViewText() { self.textView.text = self.foo.bar() } }

Slide 4

Slide 4 text

import ObjectiveC.runtime class Foo { dynamic //we'll address it don't worry func bar() -> String { return "try! Swift" } }

Slide 5

Slide 5 text

import ObjectiveC.runtime class Foo { dynamic func bar() -> String { return "try! Swift" } dynamic func new_bar() -> String { return "try! ObjC" } func updateMethod() { ... } }

Slide 6

Slide 6 text

let originalClass = Foo.self let originalSelector = Selector("bar") let originalMethod = class_getInstanceMethod(originalClass, originalSelector) let types = method_getTypeEncoding(originalMethod) let newMethod = class_getInstanceMethod(originalClass, "new_bar") let newImplementation = method_getImplementation(newMethod) class_replaceMethod(originalClass, originalSelector, newImplementation, types)

Slide 7

Slide 7 text

No content

Slide 8

Slide 8 text

class ViewController: UIViewController { ... let textView = UITextView() let foo = Foo() override func viewDidLoad() { ... self.foo.updateMethod() self.updateTextViewText() } ... }

Slide 9

Slide 9 text

No content

Slide 10

Slide 10 text

class ViewController: UIViewController { ... let textView = UITextView() let foo = Foo() override func viewDidLoad() { ... self.updateTextViewText() } func updateTextButtonPressed() { self.foo.updateMethod() self.updateTextViewText() } ... }

Slide 11

Slide 11 text

No content

Slide 12

Slide 12 text

class Foo { ... func new_bar() -> String { return "try! ObjC" } ... }

Slide 13

Slide 13 text

No content

Slide 14

Slide 14 text

No content

Slide 15

Slide 15 text

class Foo { ... func new_bar() -> String { return "try! ObjC from bundle" } ... }

Slide 16

Slide 16 text

func updateBarMethodFromExternal() { let originalClass = Foo.self let originalSelector = Selector("bar") let oldMethod = class_getInstanceMethod(Foo.self, originalSelector) let types = method_getTypeEncoding(oldMethod) ...

Slide 17

Slide 17 text

... let newClass = TrySwiftInjectable.Foo.self let newMethod = class_getInstanceMethod(newClass, "new_bar") let newImplementation = method_getImplementation(newMethod) class_replaceMethod(originalClass, originalSelector, newImplementation, types) }

Slide 18

Slide 18 text

No content

Slide 19

Slide 19 text

No content

Slide 20

Slide 20 text

func updateBarMethodFromBundle() { NSBundle(path:"/tmp/TrySwiftInjectable.bundle")?.load() self.updateBarMethodFromExternal() }

Slide 21

Slide 21 text

class ViewController: UIViewController { ... func updateTextButtonPressed() { self.foo.updateBarMethodFromBundle() self.updateTextViewText() } ... }

Slide 22

Slide 22 text

No content

Slide 23

Slide 23 text

func method_list() -> [Method] { var outCount: CUnsignedInt = 0 var injectedMethodsList = class_copyMethodList(ViewController.self, &outCount); var methods = [Method]() for _ in 0..

Slide 24

Slide 24 text

No content

Slide 25

Slide 25 text

let classesCount = objc_getClassList(nil, 0) let buffer = UnsafeMutablePointer .alloc(Int(classesCount)) let autoreleasingBuffer = AutoreleasingUnsafeMutablePointer(buffer) objc_getClassList(autoreleasingBuffer, classesCount) var classes = [AnyClass]() for i in 0 ..< classesCount { if let currentClass: AnyClass = buffer[Int(i)] { classes.append(currentClass) } } buffer.dealloc(Int(classesCount))

Slide 26

Slide 26 text

func classesFromBundlePath(path:String) -> [AnyClass] { let oldClasses = allClasses() loadBundle() let newClasses = allClasses() let updatedClasses = newClass.minus(oldClasses) return updatedClasses }

Slide 27

Slide 27 text

No content

Slide 28

Slide 28 text

No content

Slide 29

Slide 29 text

let classes = classesForBundle(bundlePath) classes.forEach(injectNewClass)

Slide 30

Slide 30 text

func injectNewClass(newClass: AnyClass) { let originalClass = NSClassFromString(class_getName(newClass)) let methods = method_list(newClass) methods.forEach { method in let newImplementation = method_getImplementation(method) let selector = method_getName(method) let types = method_getTypeEncoding(method) class_replaceMethod(originalClass, originalSelector, newImplementation, types) } }

Slide 31

Slide 31 text

No content

Slide 32

Slide 32 text

No content

Slide 33

Slide 33 text

class Foo { dynamic func bar() -> String { return "try! Swift" } ... }

Slide 34

Slide 34 text

class Foo { func bar() -> String { return "try! Swift" } ... }

Slide 35

Slide 35 text

No content

Slide 36

Slide 36 text

WHAT IS dynamic ?

Slide 37

Slide 37 text

No content

Slide 38

Slide 38 text

HOW DOES A SWIFT METHOD DISPATCH?

Slide 39

Slide 39 text

struct almost_swift_class { Class isa; Class superclass; void *cache; //cache_t uintptr_t data_NEVER_USE; struct swift_data *swiftData; int an_int_we_dont_need_1; int an_int_we_dont_need_2; int an_int_we_dont_need_3; int an_int_we_dont_need_4; int struct_size; int an_int_we_dont_need_5; IMP vtable[20]; }

Slide 40

Slide 40 text

No content

Slide 41

Slide 41 text

THIS IS FINE

Slide 42

Slide 42 text

struct almost_swift_class *newclass = (__bridge struct almost_swift_class *)injectedClass; if ( (uintptr_t)newclass->swiftData & 0x1 ) { struct almost_swift_class *oldclass = (__bridge struct almost_swift_class *)originalClass; size_t bytes = oldclass->struct_size - offsetof(struct almost_swift_class, vtable); memcpy( oldclass->vtable, newclass->vtable, bytes ); }

Slide 43

Slide 43 text

No content

Slide 44

Slide 44 text

struct almost_swift_class *newclass = (__bridge struct almost_swift_class *)injectedClass;

Slide 45

Slide 45 text

size_t bytes = oldclass->struct_size - offsetof(struct almost_swift_class, vtable_start);

Slide 46

Slide 46 text

No content

Slide 47

Slide 47 text

memcpy( oldclass->vtable_start, newclass->vtable_start, bytes );

Slide 48

Slide 48 text

func injectNewClass(newClass: AnyClass) { ... copySwiftVtable() }

Slide 49

Slide 49 text

No content

Slide 50

Slide 50 text

LIVE

Slide 51

Slide 51 text

LIVE > Trigger for when new methods are available. > CallBack in code when new methods are available.

Slide 52

Slide 52 text

var reloadableObjects: [AnyObject]

Slide 53

Slide 53 text

relaodableObjects.forEach { $0?.injected() }

Slide 54

Slide 54 text

DEMO

Slide 55

Slide 55 text

No content

Slide 56

Slide 56 text

No content

Slide 57

Slide 57 text

A COMPLEX THING IS BUILT OUT OF LESS COMPLEX THINGS

Slide 58

Slide 58 text

THANKS - John Holdsworth - Erica Sadun - Jay Freeman - Mike Ash - Gwynne Raskind - Gwendolyn Weston - The organisers, Natasha and Translators