The sdwebimageencrypt from goodopenrepo

#前言

日常开发中调试中，偶尔去其他网站上复制一个图片地址到自己的项目里调试使用，但是有些时候图片做了防盗链处理导致加载不出来，这种情况一般都是添加一个Referer解决，还有一些时图片加载了，但是展示不了，这可能是对图片进行了加密处理，这种就需要在下载好图片或者解码图片时进行解密处理，特对两种情况做下记录

https://github.com/eye1234456/SDWebImageEncrypt 一、图片防盗链Referer 在下载图片时的header里增加正确的Referer即可

二、图片加解密

###SDWebImage 5.x https://github.com/eye1234456/SDWebImageEncrypt/tree/sdwebimage_5.x podfile

  pod 'SDWebImage', '~> 5.0'
  pod 'SDWebImageWebPCoder'

解密图片由2个时机，分别是下载时和解码时，可以选择任何种，也可以两种同时存在，但是同时存在会更耗性能

#####> 2.1、解密时机一：服务器图片加密后，在下载后解密展示与缓存解密后的图片创建一个SDWebImageDownloaderOperation的子类,重写- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error方法，对图片进行解密，具体如下

#import "FEDecryptSDWebImageDownloaderOperation.h"
#import <SDWebImage/SDImageCodersManager.h>
#import "AESKeyHeader.h"
#import "NSData+FE.h"

@implementation FEDecryptSDWebImageDownloaderOperation
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {
#pragma clang diagnostic push
//"-Wunused-variable"这里就是警告的类型
#pragma clang diagnostic ignored "-Wundeclared-selector"
    if ([self respondsToSelector:@selector(imageData)]) {
#pragma clang diagnostic pop
        NSMutableData *imageData = (NSMutableData *)[self valueForKeyPath:@"imageData"];
        
        // 默认对所有数据进行解密尝试
        __block NSData *decodeData = [imageData fe_aesDecryptWithKey:kAESKey];
        // 如果解密后的数据不支持解码，则说明不需要解密
        if (![[SDImageCodersManager sharedManager] canDecodeFromData:decodeData]) {
            [super URLSession:session task:task didCompleteWithError:error];
            return;
        }
        // 对解密的数据解码成图片，如果解码失败，则说明不需要解密
        UIImage *image = [[SDImageCodersManager sharedManager] decodedImageWithData:decodeData options:nil];
        if (image == nil) {
            [super URLSession:session task:task didCompleteWithError:error];
            return;
        }
        // 如果解密后的数据能完整解码成图片，说明该图片需要加密，且能正常解码成功，则将解密后的数据继续交由后续流程处理
        NSMutableData *decodeDataM = [decodeData mutableCopy];
        if (decodeDataM != nil) {
            [self setValue:decodeDataM forKeyPath:@"imageData"];
        }
        
    }
    [super URLSession:session task:task didCompleteWithError:error];
    
}

将自定义的下载解密类配置给SDWebImage

- (void)configDecryptSDWebImageAtDownloadTime {
    // 配置支持webp图片
    SDImageWebPCoder *webPCoder = [SDImageWebPCoder sharedCoder];
    [[SDImageCodersManager sharedManager] addCoder:webPCoder];
    // 配置图片下载时解密，并将解密的图片缓存到本地
    SDWebImageDownloaderConfig.defaultDownloaderConfig.operationClass = FEDecryptSDWebImageDownloaderOperation.class;;

}

#####> 2.2、解密时机二：、服务器图片加密后，在下载后将NSData解码成图片成解密，缓存的数据是加密的数据，每次从硬盘获取图片时都要先解密然后再解码

创造各种默认ImageCoder的子类，包含：SDImageIOCoder、SDImageGIFCoder、SDImageAPNGCoder、SDImageWebPCoder的子类，并重写- (BOOL)canDecodeFromData:(nullable NSData *)data和- (UIImage *)decodedImageWithData:(NSData *)data options:(nullable SDImageCoderOptions *)options两个方法，具体实现如下（以gif为例）：


#import "FESDImageGIFCoder.h"

#import "AESKeyHeader.h"
#import "NSData+FE.h"

@implementation FESDImageGIFCoder

- (BOOL)canDecodeFromData:(nullable NSData *)data {
    // 默认对所有数据进行解密尝试
    __block NSData *decodeData = [data fe_aesDecryptWithKey:kAESKey];
    // 判断解密的图片是否符合当前解码器，如果符合，直接返回yes
    BOOL canDecode = [super canDecodeFromData:decodeData];
    if (canDecode) {
        return canDecode;
    }
    // 不符合，则使用原始数据调用父类解码器
    return [super canDecodeFromData:data];
}

- (UIImage *)decodedImageWithData:(NSData *)data options:(nullable SDImageCoderOptions *)options {
    if (!data) {
        return nil;
    }
    // 默认对所有数据进行解密尝试
    __block NSData *decodeData = [data fe_aesDecryptWithKey:kAESKey];
    // 如果使用解密的数据解码成功，则表示图片是需要解密的，返回解密后的图片
    UIImage *image = [super decodedImageWithData:decodeData options:options];
    if (image != nil) {
        return image;
    }
    // 解密后的图片解码失败，则直接使用原始数据进行解码
    return [super decodedImageWithData:data options:options];
}
@end

初始化时调用

- (void)configDecrptyAtDecodeTime {
    // 配置图片解码时解密，由于SDWebImage在使用时是逆序，所以这里的顺序不能乱
    // 普通图片
    [SDImageCodersManager.sharedManager addCoder:FEDecryptSDImageIOCoder.new];
    // gif图片
    [SDImageCodersManager.sharedManager addCoder:FESDImageGIFCoder.new];
    // apng图片
    [SDImageCodersManager.sharedManager addCoder:FESDImageAPNGCoder.new];
    // webp图片
    [SDImageCodersManager.sharedManager addCoder:FESDImageWebPCoder.new];
}

还有一种使用分类的方式，将codermanager进行统一处理

- (void)configDecrptyAtDecodeTime2 {
    // 使用分类的方式，对所有的coder进行统一解密处理
    // SDImageCodersManager+FEAllLoader
    // webp图片
    [SDImageCodersManager.sharedManager addCoder:[SDImageWebPCoder sharedCoder]];
}

#import <SDWebImage/SDWebImage.h>

NS_ASSUME_NONNULL_BEGIN

@interface SDImageCodersManager (FEAllLoader)

@end

NS_ASSUME_NONNULL_END

解密分类

#import "SDImageCodersManager+FEAllLoader.h"
#import <objc/runtime.h>
#import "AESKeyHeader.h"
#import "NSData+FE.h"

@implementation SDImageCodersManager (FEAllLoader)
+ (void)load {
    
    Method canDecodeMethod = class_getInstanceMethod(self, @selector(canDecodeFromData:));
    Method feCanDecodeMethodMethod = class_getInstanceMethod(self, @selector(fe_canDecodeFromData:));
    method_exchangeImplementations(canDecodeMethod, feCanDecodeMethodMethod);
    
    Method decodeMethod = class_getInstanceMethod(self, @selector(decodedImageWithData:options:));
    Method feDecodeMethodMethod = class_getInstanceMethod(self, @selector(fe_decodedImageWithData:options:));
    method_exchangeImplementations(decodeMethod, feDecodeMethodMethod);
}

- (BOOL)fe_canDecodeFromData:(NSData *)data {
    BOOL canDecode = [self fe_canDecodeFromData:data];
    if (!canDecode) {
        NSData *decodeData = [data fe_aesDecryptWithKey:kAESKey];
        canDecode = [self fe_canDecodeFromData:decodeData];
    }
    return canDecode;
}

- (UIImage *)fe_decodedImageWithData:(NSData *)data options:(nullable SDImageCoderOptions *)options {
    if (!data) {
        return nil;
    }
    UIImage *image = [self fe_decodedImageWithData:data options:options];
    if (image == nil) {
        NSData *decodeData = [data fe_aesDecryptWithKey:kAESKey];
        image = [self fe_decodedImageWithData:decodeData options:options];
    }
    return image;
}
@end

###SDWebImage 4.x https://github.com/eye1234456/SDWebImageEncrypt/tree/sdwebimage_4.x 大同小异，只是一些类名和方法不一致 podfile

pod 'SDWebImage', '~> 4.4.8'
  pod 'SDWebImage/WebP'
  pod 'SDWebImage/GIF'

需要重写配置的类下载时解密：SDWebImageDownloaderOperation 解码时解密：SDWebImageImageIOCoder SDWebImageGIFCoder SDWebImageWebPCoder

###YYWebImage https://github.com/eye1234456/SDWebImageEncrypt/tree/yywebimage 由于YYWebImage里的代码写的比较死，不像SDWebImage一样是可以灵活配置子类，所以只能使用分类在load方法里进行方法交换处理 podfile

  # YYWebImage
  pod 'YYWebImage'
  pod 'YYImage/WebP'

需要重写配置的类下载时解密：YYWebImageOperation

具体实现就是重写数据下载完成时，尝试解密后读取图片类型，如果解密读取的类型是正常的，未解密的图片读取的图片不正常，则将解密后的Data数据替换未解密的Data数据

#import "YYWebImageOperation+FE.h"
#import <objc/runtime.h>
#import "AESKeyHeader.h"
#import "NSData+FE.h"

@implementation YYWebImageOperation (FE)
+ (void)load {
#pragma clang diagnostic push
//"-Wunused-variable"这里就是警告的类型
#pragma clang diagnostic ignored "-Wundeclared-selector"
    Method originMethod = class_getInstanceMethod(self, @selector(_fe_connectionDidFinishLoading:));
    Method swizzledMethod = class_getInstanceMethod(self, @selector(connectionDidFinishLoading:));
#pragma clang diagnostic pop
    method_exchangeImplementations(originMethod, swizzledMethod);
}
- (void)_fe_connectionDidFinishLoading:(NSURLConnection *)connection {
#pragma clang diagnostic push
//"-Wunused-variable"这里就是警告的类型
#pragma clang diagnostic ignored "-Wundeclared-selector"
    if ([self respondsToSelector:@selector(data)]) {
#pragma clang diagnostic pop
        NSMutableData *data = (NSMutableData *)[self valueForKeyPath:@"data"];
    // 默认对所有数据进行解密尝试
    NSData *decodeData = [data fe_aesDecryptWithKey:kAESKey];
    YYImageType originImageType = YYImageDetectType((__bridge CFDataRef)data);
    YYImageType decodeImageType = YYImageDetectType((__bridge CFDataRef)decodeData);
        if (originImageType == YYImageTypeUnknown && decodeImageType != YYImageTypeUnknown) {
            NSMutableData *decodeDataM = [decodeData mutableCopy];
            [self setValue:decodeDataM forKeyPath:@"data"];
        }
    }
    [self _fe_connectionDidFinishLoading:connection];
}
@end

####方式二、YYWebImage在解码时解密创建YYImageDecoder的分类，在将data解码成YYImage时，如果解码失败，将数据解密后再次尝试解码


//
//  YYImageDecoder+FE.h
//  SDWebImageEncrypt
//
//  Created by Flow on 3/24/22.
//

#import <YYImage/YYImage.h>

NS_ASSUME_NONNULL_BEGIN

@interface YYImageDecoder (FE)

@end

NS_ASSUME_NONNULL_END


//
//  YYImageDecoder+FE.m
//  SDWebImageEncrypt
//
//  Created by Flow on 3/24/22.
//

#import "YYImageDecoder+FE.h"
#import <objc/runtime.h>
#import "AESKeyHeader.h"
#import "NSData+FE.h"

@implementation YYImageDecoder (FE)
+ (void)load {
    
    static dispatch_once_t onceToken;
        dispatch_once(&onceToken, ^{
            // 交换类方法
            [self swizzleMethod:object_getClass((id)self) orgSel:@selector(decoderWithData:scale:) swizzSel:@selector(fe_decoderWithData:scale:)];
        });
}

/// 交换方法
+ (BOOL)swizzleMethod:(Class)class orgSel:(SEL)origSel swizzSel:(SEL)altSel {
    Method origMethod = class_getInstanceMethod(class, origSel);
    Method altMethod = class_getInstanceMethod(class, altSel);
    if (!origMethod || !altMethod) {
        return NO;
    }
    BOOL didAddMethod = class_addMethod(class,origSel,
                                        method_getImplementation(altMethod),
                                        method_getTypeEncoding(altMethod));
    
    if (didAddMethod) {
        class_replaceMethod(class,altSel,
                            method_getImplementation(origMethod),
                            method_getTypeEncoding(origMethod));
    } else {
        method_exchangeImplementations(origMethod, altMethod);
    }
    
    return YES;
}

/// AES解密图片
+ (instancetype)fe_decoderWithData:(NSData *)data scale:(CGFloat)scale {
    YYImageDecoder *decoder = [self fe_decoderWithData:data scale:scale];
    if (decoder == nil) {
        NSData *decodeData = [data fe_aesDecryptWithKey:kAESKey];
        decoder = [self fe_decoderWithData:decodeData scale:scale];
    }
    return decoder;
}
@end

YYWebImage里的YYAnimatedImageView在展示的是非动图时展示不出来，原因是单张图时displayLayer:没做任何处理参考：ibireme/YYWebImage#242

- (void)displayLayer:(CALayer *)layer {
    if (_curFrame) {
        layer.contents = (__bridge id)_curFrame.CGImage;
    }
}

修改如下即可：

- (void)displayLayer:(CALayer *)layer {
    if (_curFrame) {
        layer.contents = (__bridge id)_curFrame.CGImage;
    }else {
        [super displayLayer:layer];
    }
}

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