Hook Internal Implementation of MGCopyAnswer (iOS 15)

MGCopyAnswer-Tweak.mm

#import <dlfcn.h>
#import <os/log.h>
#import <substrate.h>
#import <Foundation/Foundation.h>

#import "pac_helper.h"
#define _FUNC_ADDR_(A, O) (const void *)((long)(A) + (O))

/* ... */

static __attribute__((constructor)) void CHConstructor20()
{
    if (memcmp(make_sym_readable(ptrMGCopyAnswer), "\x01\x00\x80\xd2\x01\x00\x00\x14", 8) == 0)
    {
        MSHookFunction(make_sym_callable((void *)_FUNC_ADDR_(ptrMGCopyAnswer, 8)), 
                      (void *)replaced_MGCopyAnswer_internal,
                      (void **)&original_MGCopyAnswer_internal);
        
        os_log_debug(OS_LOG_DEFAULT, "Hooked legacy MGCopyAnswer_internal");
    }
    else if (memcmp(make_sym_readable(ptrMGCopyAnswer), "\x01\x00\x80\xd2", 4) == 0)
    {
        // Calculate the opcode of arm64 instruction B
        // Which is the offset of the function pointer
        
        // B <offset>
        void *bInstPtr = (void *)((uint8_t *)ptrMGCopyAnswer + 4);
        int32_t bInst = *((int32_t *)make_sym_readable(bInstPtr));
        
        // Check if it is a branch instruction
        if ((bInst & 0xFC000000) != 0x14000000) {
            os_log_error(OS_LOG_DEFAULT, "MGCopyAnswer_internal: Invalid branch instruction");
            return;
        }
        os_log_debug(OS_LOG_DEFAULT, "B instruction: 0x%x", bInst);

        int32_t offset = bInst & 0x3FFFFFF;
        if (offset & 0x2000000)
            offset |= 0xFC000000;
        offset <<= 2;
        os_log_debug(OS_LOG_DEFAULT, "Offset: 0x%x, %d", offset, offset);
        
        void *mPtrMGCopyAnswer = (void *)_FUNC_ADDR_(bInstPtr, offset);
        os_log_debug(OS_LOG_DEFAULT, "File offset of MGCopyAnswer_internal: 0x%lx", ABS((long)mPtrMGCopyAnswer - (long)handle));
        
        MSHookFunction(make_sym_callable(mPtrMGCopyAnswer), 
                      (void *)replaced_MGCopyAnswer_internal,
                      (void **)&original_MGCopyAnswer_internal);
        
        os_log_debug(OS_LOG_DEFAULT, "Hooked modern MGCopyAnswer_internal");
    }
    else
    {
        os_log_error(OS_LOG_DEFAULT, "Unsupported MGCopyAnswer");
    }
}

大佬为何不用 https://mayuyu.io/2017/06/26/HookingMGCopyAnswerLikeABoss/

大佬为何不用 https://mayuyu.io/2017/06/26/HookingMGCopyAnswerLikeABoss/

这就是拿掉 capstone 之后的实现

CNKCQ

ios 16 worked