macOS Function Hooking

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Kuingilia Kazi

Tengeneza dylib na sehemu ya __interpose (__DATA___interpose) (au sehemu iliyofungwa na S_INTERPOSING) inayojumuisha jozi za pointa za kazi zinazorejelea kazi za awali na zilizochukua nafasi.

Kisha, ingiza dylib na DYLD_INSERT_LIBRARIES (kuingilia kazi kunahitaji kutokea kabla ya programu kuu kupakia). Kwa dhahiri vizuizi vilivyowekwa kwenye matumizi ya DYLD_INSERT_LIBRARIES pia hapa.

Kuingilia printf

interpose.c
// gcc -dynamiclib interpose.c -o interpose.dylib
#include <stdio.h>
#include <stdarg.h>

int my_printf(const char *format, ...) {
//va_list args;
//va_start(args, format);
//int ret = vprintf(format, args);
//va_end(args);

int ret = printf("Hello from interpose\n");
return ret;
}

__attribute__((used)) static struct { const void *replacement; const void *replacee; } _interpose_printf
__attribute__ ((section ("__DATA,__interpose"))) = { (const void *)(unsigned long)&my_printf, (const void *)(unsigned long)&printf };
DYLD_INSERT_LIBRARIES=./interpose.dylib ./hello
Hello from interpose

DYLD_INSERT_LIBRARIES=./interpose2.dylib ./hello
Hello from interpose

Chaguo la mazingira la DYLD_PRINT_INTERPOSTING linaweza kutumika kudebugi interposing na litachapisha mchakato wa interpose.

Pia elewa kwamba interposing hutokea kati ya mchakato na maktaba zilizopakiwa, haitafanyi kazi na hifadhi ya maktaba iliyoshirikiwa.

Interposing ya Kisasa

Sasa pia ni iwezekanavyo kuingiza kazi kwa njia ya kisasa kwa kutumia kazi ya dyld_dynamic_interpose. Hii inaruhusu kuingiza kazi kwa njia ya programu wakati wa muda wa uendeshaji badala ya kufanya hivyo tu kutoka mwanzoni.

Inahitajika tu kuonyesha tuples ya kazi ya kuchukua nafasi na kazi mbadala.

struct dyld_interpose_tuple {
const void* replacement;
const void* replacee;
};
extern void dyld_dynamic_interpose(const struct mach_header* mh,
const struct dyld_interpose_tuple array[], size_t count);

Kufunga Mbinu

Katika ObjectiveC hivi ndivyo mbinu inavyoitwa: [myClassInstance nameOfTheMethodFirstParam:param1 secondParam:param2]

Inahitajika kitu, mbinu na paramu. Na wakati mbinu inaitwa msg inatumwa kutumia kazi objc_msgSend: int i = ((int (*)(id, SEL, NSString *, NSString *))objc_msgSend)(someObject, @selector(method1p1:p2:), value1, value2);

Kitu ni someObject, mbinu ni @selector(method1p1:p2:) na hoja ni value1, value2.

Kufuatia miundo ya vitu, ni rahisi kufikia orodha ya mbinu ambapo majina na alama za nambari ya mbinu zinapatikana.

Tafadhali kumbuka kwamba kwa sababu mbinu na madarasa yanafikiwa kulingana na majina yao, habari hii imehifadhiwa kwenye faili ya binary, hivyo ni rahisi kuipata kwa kutumia otool -ov </path/bin> au class-dump </path/bin>

Kufikia mbinu za asili

Inawezekana kupata habari za mbinu kama jina, idadi ya paramu au anwani kama ilivyo kwenye mfano ufuatao:

// gcc -framework Foundation test.m -o test

#import <Foundation/Foundation.h>
#import <objc/runtime.h>
#import <objc/message.h>

int main() {
// Get class of the variable
NSString* str = @"This is an example";
Class strClass = [str class];
NSLog(@"str's Class name: %s", class_getName(strClass));

// Get parent class of a class
Class strSuper = class_getSuperclass(strClass);
NSLog(@"Superclass name: %@",NSStringFromClass(strSuper));

// Get information about a method
SEL sel = @selector(length);
NSLog(@"Selector name: %@", NSStringFromSelector(sel));
Method m = class_getInstanceMethod(strClass,sel);
NSLog(@"Number of arguments: %d", method_getNumberOfArguments(m));
NSLog(@"Implementation address: 0x%lx", (unsigned long)method_getImplementation(m));

// Iterate through the class hierarchy
NSLog(@"Listing methods:");
Class currentClass = strClass;
while (currentClass != NULL) {
unsigned int inheritedMethodCount = 0;
Method* inheritedMethods = class_copyMethodList(currentClass, &inheritedMethodCount);

NSLog(@"Number of inherited methods in %s: %u", class_getName(currentClass), inheritedMethodCount);

for (unsigned int i = 0; i < inheritedMethodCount; i++) {
Method method = inheritedMethods[i];
SEL selector = method_getName(method);
const char* methodName = sel_getName(selector);
unsigned long address = (unsigned long)method_getImplementation(m);
NSLog(@"Inherited method name: %s (0x%lx)", methodName, address);
}

// Free the memory allocated by class_copyMethodList
free(inheritedMethods);
currentClass = class_getSuperclass(currentClass);
}

// Other ways to call uppercaseString method
if([str respondsToSelector:@selector(uppercaseString)]) {
NSString *uppercaseString = [str performSelector:@selector(uppercaseString)];
NSLog(@"Uppercase string: %@", uppercaseString);
}

// Using objc_msgSend directly
NSString *uppercaseString2 = ((NSString *(*)(id, SEL))objc_msgSend)(str, @selector(uppercaseString));
NSLog(@"Uppercase string: %@", uppercaseString2);

// Calling the address directly
IMP imp = method_getImplementation(class_getInstanceMethod(strClass, @selector(uppercaseString))); // Get the function address
NSString *(*callImp)(id,SEL) = (typeof(callImp))imp; // Generates a function capable to method from imp
NSString *uppercaseString3 = callImp(str,@selector(uppercaseString)); // Call the method
NSLog(@"Uppercase string: %@", uppercaseString3);

return 0;
}

Marejeo

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