random-developer · May 28, 2019 01:20 · May 26, 2017
diff --git a/AutoHook.h b/AutoHook.h
@@ -0,0 +1,6 @@
+@protocol AutoHook <NSObject>
+@required
+
++ (NSArray <NSString *> *)targetClasses;
+
+@end
diff --git a/AutoHookImplementor.m b/AutoHookImplementor.m
@@ -0,0 +1,164 @@
+@import Foundation;
+@import ObjectiveC.runtime;
+@import MachO.dyld;
+
+#import "AutoHook.h"
+
+@interface AutoHookImplementor : NSObject
+
+@end
+
+@implementation AutoHookImplementor
+
++ (void)load {
+    [self implementAllMethodHooks];
+}
+
+
++ (void)implementAllMethodHooks {
+    unsigned classCount;
+    Class *classes = objc_copyClassList(&classCount);
+    if (!classes) {
+        NSLog(@"Error: Auto hook couldn't get class list");
+        return;
+    }
+
+    Protocol *hookProtocol = @protocol(AutoHook);
+
+    for (int index = 0; index < classCount; index += 1) {
+        Class hookClass = classes[index];
+        if (class_conformsToProtocol(hookClass, hookProtocol) == false) {
+            continue;
+        }
+        [self implementHooksForClass:hookClass];
+    }
+
+    free(classes);
+}
+
++ (void)implementHooksForClass:(Class)hookClass {
+    const char *className = class_getName(hookClass);
+    Class metaClass = hookClass;
+    if (class_isMetaClass(metaClass) == FALSE && className != NULL) {
+        Class potentialMetaClass = objc_getMetaClass(className);
+        if (potentialMetaClass) {
+            metaClass = potentialMetaClass;
+        }
+
+        NSArray *targetClasses = [hookClass targetClasses];
+
+        for (NSString *targetClassName in targetClasses) {
+            Class targetClass = NSClassFromString(targetClassName);
+            if (!targetClass) {
+                NSLog(@"Couldn't find target class %@", targetClassName);
+                continue;
+            }
+
+            [self implementMethodHooksForClass:hookClass
+                                   targetClass:targetClass];
+        }
+    }
+}
+
++ (void)implementMethodHooksForClass:(Class)hookClass
+                         targetClass:(Class)targetClass {
+    unsigned int methodCount;
+    Method *methods = class_copyMethodList(hookClass, &methodCount);
+    if (!methods) {
+        NSLog(@"Couldn't get method list for class: %s", class_getName(hookClass));
+        return;
+    }
+    for (int methodIndex = 0; methodIndex < methodCount; methodIndex += 1) {
+        Method hookMethod = methods[methodIndex];
+        if (!hookMethod) {
+            continue;
+        }
+
+        SEL hookMethodSelector = method_getName(hookMethod);
+        if (!hookMethodSelector) {
+            continue;
+        }
+
+        NSString *hookPrefix = @"hook_";
+        NSString *originalStorePrefix = @"original_";
+
+        NSString *hookMethodName = NSStringFromSelector(hookMethodSelector);
+        if ([hookMethodName hasPrefix:hookPrefix] == FALSE) {
+            if ([hookMethodName hasPrefix:originalStorePrefix] == FALSE) {
+                [self addMethodToClass:targetClass fromClass:hookClass method:hookMethod];
+            }
+            continue;
+        }
+
+        NSString *targetMethodName = [hookMethodName substringFromIndex:hookPrefix.length];
+        SEL targetMethodSelector = NSSelectorFromString(targetMethodName);
+        Method targetMethod = class_getInstanceMethod(targetClass, targetMethodSelector);
+        BOOL targetMetaClass = FALSE;
+
+        if (!targetMethod) {
+            targetMetaClass = TRUE;
+            targetMethod = class_getClassMethod(targetClass, targetMethodSelector);
+        }
+
+        if (!targetMethod) {
+            NSLog(@"Error: Target class %s doesn't incorporate method %@",
+                  class_getName(targetClass), targetMethodName);
+            continue;
+        }
+
+        const char *targetTypeEncoding = method_getTypeEncoding(targetMethod);
+        const char *hookedTypeEncoding = method_getTypeEncoding(hookMethod);
+        if (strcmp(targetTypeEncoding, hookedTypeEncoding) != 0) {
+            NSLog(@"Error: Not implementing hook: target type encoding %s doesn't match hook type encoding: %s for selector %s",
+                  targetTypeEncoding, hookedTypeEncoding, sel_getName(targetMethodSelector));
+            return;
+        }
+
+        IMP hookImplementation = method_getImplementation(hookMethod);
+        if (!hookImplementation) {
+            NSLog(@"Error: Couldn't get implementation for method %@", hookMethodName);
+            continue;
+        }
+
+        NSString *originalStoreMethodName = [originalStorePrefix stringByAppendingString:targetMethodName];
+        SEL originalStoreSelector = NSSelectorFromString(originalStoreMethodName);
+
+        Method originalStoreMethod = class_getInstanceMethod(hookClass, originalStoreSelector);
+        if (!originalStoreMethod) {
+            class_getClassMethod(hookClass, originalStoreSelector);
+        }
+
+        IMP originalImplementation = method_getImplementation(targetMethod);
+        if (!originalImplementation) {
+            NSLog(@"Error: Couldn't get implementation for method %@", targetMethodName);
+            continue;
+        }
+
+        if (originalStoreMethod) {
+            Class addMethodClass = targetClass;
+            if (targetMetaClass) {
+                addMethodClass = objc_getMetaClass(class_getName(targetClass));
+            }
+            class_addMethod(addMethodClass, originalStoreSelector, originalImplementation, targetTypeEncoding);
+        }
+
+        IMP previousImplementation = class_replaceMethod(targetClass, targetMethodSelector, hookImplementation, targetTypeEncoding);
+        if (previousImplementation != NULL) {
+            NSLog(@"Implemented hook for [%s %@]", class_getName(targetClass), targetMethodName);
+        } else {
+            NSLog(@"Failed to implement hook for [%s %@]", class_getName(targetClass), targetMethodName);
+        }
+
+    }
+
+    free(methods);
+}
+
++ (void)addMethodToClass:(Class)targetClass fromClass:(Class)hookClass method:(Method)method {
+    SEL selector = method_getName(method);
+    const char *typeEncoding = method_getTypeEncoding(method);
+    IMP implementation = method_getImplementation(method);
+    class_addMethod(targetClass, selector, implementation, typeEncoding);
+}
+
+@end
diff --git a/exampleHook.m b/exampleHook.m
@@ -0,0 +1,28 @@
+@import UIKit;
+#import "AutoHook.h"
+
+@interface HOOKUIViewController: UIViewController <AutoHook>
+@end
+@implementation HOOKUIViewController
+
++ (NSArray *)targetClasses {
+    return @[@"UIViewController"];
+}
+
+
+- (void)hook_viewDidLoad {
+    [self original_viewDidLoad];
+    [self addOverlayView];
+}
+
+- (void)addOverlayView {
+  UIView *overlayView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 150, 150)];
+    blue.backgroundColor = [UIColor.greenColor colorWithAlphaComponent:0.15];
+    [self.view addSubview:blue];
+}
+
+// MARK: - Placeholders
+
+- (void)original_viewDidLoad { }
+
+@end
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