iOS 信息安全 - 后台挂起

最新推荐文章于 2021-12-02 22:00:42 发布

Mokzark

最新推荐文章于 2021-12-02 22:00:42 发布

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CC 4.0 BY-SA版权

分类专栏： ios 文章标签： app安全后台挂起模糊效果数据隐私

本文链接：https://blog.youkuaiyun.com/ssq940410/article/details/84584901

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当iOS应用进入后台时，系统保存的屏幕快照可能暴露敏感信息。本文介绍了如何通过添加高斯模糊视图来防止信息泄露，详细讲解了在`applicationWillResignActive`和`applicationDidBecomeActive`中添加和移除模糊视图的实现，并提供了模糊算法的实现代码。参考了支付宝后台挂起时的模糊效果。

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当应用进入后台时，系统会自动在当前应用的页面截屏并存储到手机内，如果当前页面涉及敏感信息时，被攻击会造成泄密。如下图生成的两张图片路径：

防止造成信息泄露 - 添加高斯模糊(参考支付宝挂起时的模糊效果)

实现方案：

在applicationWillResignActive中添加模糊视图

- (BlurView *)backgroundBar{

if (!_backgroundBar) {

_backgroundBar = [[BlurView alloc] initWithFrame:[UIScreen mainScreen].bounds];

}

return _backgroundBar;

}

- (void)applicationWillResignActive:(UIApplication *)application {

__weak typeof(self)weakSelf = self;

dispatch_async(dispatch_get_main_queue(), ^{

for (UIWindow *window in [UIApplication sharedApplication].windows) {

if (window.windowLevel == UIWindowLevelNormal) {

[window addSubview:weakSelf.backgroundBar];

}

});

}

然后在applicationDidBecomeActive中将模糊视图删除

- (void)applicationDidBecomeActive:(UIApplication *)application {

__weak typeof(self)weakSelf = self;

dispatch_async(dispatch_get_main_queue(), ^{

[weakSelf.backgroundBar removeFromSuperview];

weakSelf.backgroundBar = nil;

});

}

模糊视图实现方案

#import "CMFKBlurView.h"

#import <Accelerate/Accelerate.h>

#define screenWidth SCREEN_WIDTH

#define screenHeight SCREEN_HEIGHT

#define screenScale ([UIScreen mainScreen].scale)

#if __IPHONE_OS_VERSION_MAX_ALLOWED > __IPHONE_6_1

#define kCGImageAlphaPremultipliedLast (kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedLast)

#else

#define kCGImageAlphaPremultipliedLast kCGImageAlphaPremultipliedLast

#endif

@implementation CMFKBlurView

- (instancetype)initWithFrame:(CGRect)frame{

self = [super initWithFrame:frame];

if (self) {

UIImage *image = [UIImage imageWithData:UIImageJPEGRepresentation([self getCurrentImage], 1.0)];

self.blurImage = [self blurryImage:image withBlurLevel:0.3];

UIImageView *bgView = [[UIImageView alloc] initWithFrame:frame];

bgView.image =self.blurImage;

[self addSubview:bgView];

}

return self;

}

- (UIImage *)getCurrentImage{

UIGraphicsBeginImageContextWithOptions(CGSizeMake(screenWidth*screenScale,screenHeight*screenScale),YES, 0);//截屏

[[[[UIApplication sharedApplication] keyWindow] layer] renderInContext:UIGraphicsGetCurrentContext()];

UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

CGImageRef imageRef = viewImage.CGImage;

CGRect rect =CGRectMake(0,0, screenWidth*screenScale,screenHeight*screenScale);

CGImageRef imageRefRect =CGImageCreateWithImageInRect(imageRef, rect);

UIImage *sendImage = [[UIImage alloc] initWithCGImage:imageRefRect];

CGImageRelease(imageRefRect);

return sendImage;

}

//模糊算法

- (UIImage *)blurryImage:(UIImage *)image withBlurLevel:(CGFloat)blur {

if (blur <0.f || blur > 1.f) {

blur = 0.5f;

}

int boxSize = (int)(blur *100);

boxSize = boxSize - (boxSize % 2) +1;

CGImageRef img = image.CGImage;

vImage_Buffer inBuffer, outBuffer;

vImage_Error error;

void *pixelBuffer;

CGDataProviderRef inProvider =CGImageGetDataProvider(img);

CFDataRef inBitmapData =CGDataProviderCopyData(inProvider);

inBuffer.width =CGImageGetWidth(img);

inBuffer.height =CGImageGetHeight(img);

inBuffer.rowBytes =CGImageGetBytesPerRow(img);

inBuffer.data = (void*)CFDataGetBytePtr(inBitmapData);

pixelBuffer = malloc(CGImageGetBytesPerRow(img) *CGImageGetHeight(img));

if(pixelBuffer ==NULL)

NSLog(@"No pixelbuffer");

outBuffer.data = pixelBuffer;

outBuffer.width =CGImageGetWidth(img);

outBuffer.height =CGImageGetHeight(img);

outBuffer.rowBytes =CGImageGetBytesPerRow(img);

error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer, NULL, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);

if (error) {

NSLog(@"error from convolution %ld", error);

}

CGColorSpaceRef colorSpace =CGColorSpaceCreateDeviceRGB();

CGContextRef ctx =CGBitmapContextCreate(outBuffer.data,outBuffer.width,outBuffer.height,8,outBuffer.rowBytes,colorSpace,kCGImageAlphaPremultipliedLast);

CGImageRef imageRef =CGBitmapContextCreateImage (ctx);

UIImage *returnImage = [UIImage imageWithCGImage:imageRef];

//clean up

CGContextRelease(ctx);

CGColorSpaceRelease(colorSpace);

free(pixelBuffer);

CFRelease(inBitmapData);

CGColorSpaceRelease(colorSpace);

CGImageRelease(imageRef);

return returnImage;

}

参考文章: https://blog.youkuaiyun.com/jp940110jpjp/article/details/44307515