ios - 是否可以混淆UIViewAlertForUnsatisfiableConstraints？

Question

我想知道UIViewAlertForUnsatisfiableConstraints是否是我可以选择的选择器。到目前为止，我所知道的只是UIViewAlertForUnsatisfiableConstraints是一种可以用来放置符号断点的符号。但是我在任何公开课上都找不到这个符号。有人知道它在哪里吗？

请注意，我希望在单元测试中而不是在生产代码中执行此操作。

Answer 1

因为UIViewAlertForUnsatisfiableConstraints是C函数，所以混淆它比典型的Objective C方法需要更多的工作。

最简单的方法(大多数消息人士说这是唯一可能的方法)是通过Substrate的MSHookFunction进行的，但是这需要越狱的手机。如果这是一个有效的选项，我建议您使用它来简单地钩住函数。

在非越狱环境中，需要高级运行时操作。出于某种原因，我真的很喜欢浪费时间学习即将成为死语的语言..所以这里是完整的解决方案!这个link提供了巨大的帮助。

#import <dlfcn.h>
#import <objc/runtime.h>
#include <sys/mman.h>

int64_t originalOffset;
int64_t *origFunc;

void swizzled_UIViewAlertForUnsatisfiableConstraints(NSLayoutConstraint *offendingConstraint, NSArray *allConstraints) {
    // inject swizzle code here
    NSLog(@"swizzled!");

    // call the original function (if you want!)
    if (origFunc) {
        // replace jump instruction w/ the original memory offset
        *origFunc = originalOffset;
        ((void(*)(NSLayoutConstraint*, NSArray*))origFunc)(offendingConstraint, allConstraints);
    }
}

static inline BOOL swizzleAlertForUnsatisfiableConstraints() {

    // get the original function and hold onto it's memory offset
    origFunc = dlsym(RTLD_DEFAULT, "UIViewAlertForUnsatisfiableConstraints");
    if (!origFunc) {
        return NO;
    }
    originalOffset = *origFunc;

    // define the swizzled implementation
    int64_t *swizzledFunc = (int64_t*)&swizzled_UIViewAlertForUnsatisfiableConstraints;

    // make the memory containing the original funcion writable
    size_t pageSize = sysconf(_SC_PAGESIZE);
    uintptr_t start = (uintptr_t)origFunc;
    uintptr_t end = start + 1;
    uintptr_t pageStart = start & -pageSize;
    mprotect((void *)pageStart, end - pageStart, PROT_READ | PROT_WRITE | PROT_EXEC);

    //Calculate the relative offset needed for the jump instruction
    //Since relative jumps are calculated from the address of the next instruction,
    //  5 bytes must be added to the original address (jump instruction is 5 bytes)
    int64_t offset = (int64_t)swizzledFunc - ((int64_t)origFunc + 5 * sizeof(char));

    //Set the first instruction of the original function to be a jump
    //  to the replacement function.
    //E9 is the x86 opcode for an unconditional relative jump
    int64_t instruction = 0xe9 | offset << 8;
    *origFunc = instruction;

    return YES;
}