关于融云及时聊天的消息加密

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  好久没更新技术文章了，正好最近做了点东西，拿出来分享一下。
  鉴于行业数据的保密性，公司要求在集成了融云及时聊天的App中对消息做加、解密处理，保证在消息转发过程中，消息是以密文传输的。关于如何加、解密以及密钥的传输、存放我就不说了，自己百度去，下面来谈谈怎么对RCTextMessage做加解密。
  由于官方的SDK只对开发者暴露了头文件，对里面的实现方式我们并不能知道，怀着研究的心态，我给它反编译（class-dump）了，多少能看到点东西~~~😝😝😝

#import "RCMessageContent.h"
#import "NSCoding.h"

@class NSString;

@interface RCTextMessage : RCMessageContent <NSCoding>
{
    NSString *_content;
    NSString *_extra;
}

+ (id)getObjectName;
+ (unsigned long long)persistentFlag;
+ (id)messageWithContent:(id)arg1;
@property(retain, nonatomic) NSString *extra; // @synthesize extra=_extra;
@property(retain, nonatomic) NSString *content; // @synthesize content=_content;
- (void).cxx_destruct;
- (id)conversationDigest;
- (id)getSearchableWords;
- (void)decodeWithData:(id)arg1;
- (id)encode;
- (void)encodeWithCoder:(id)arg1;
- (id)initWithCoder:(id)arg1;

@end

  看到了吗，我们要的东西出来了，"encodeWithCoder:"、 "encode"、 "decodeWithData:"。自然而然，思路也就顺了——在它编码、解码的时候，做加、解密。
  怎么做呢？原本我是想用继承的，后来考虑到代码侵入性太大，不如使用Category给它重写了，不要谢我，就是这么刚，这么邪恶~~ 😝😝😝言简意赅，能用代码解决的就不逼逼，自己看代码去吧。

#import "RCTextMessage+Custom.h"

@implementation RCTextMessage (Custom)

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wobjc-protocol-method-implementation"
/// NSCoding
- (instancetype)initWithCoder:(NSCoder *)aDecoder {
    self = [super init];
    if (self) {
        self.content = [aDecoder decodeObjectForKey:@"content"];
        self.extra = [aDecoder decodeObjectForKey:@"extra"];
    }
    return self;
}

/// NSCoding
- (void)encodeWithCoder:(NSCoder *)aCoder {
    [aCoder encodeObject:self.content.ib_encrypt forKey:@"content"];
    [aCoder encodeObject:self.extra forKey:@"extra"];
}

///将消息内容编码成json
- (NSData *)encode {
    NSMutableDictionary *dataDict = [NSMutableDictionary dictionary];
    [dataDict setObject:self.content.ib_encrypt forKey:@"content"];
    if (self.extra) {
        [dataDict setObject:self.extra forKey:@"extra"];
    }
    
    if (self.senderUserInfo) {
        NSMutableDictionary *userInfoDic = [[NSMutableDictionary alloc] init];
        if (self.senderUserInfo.name) {
            [userInfoDic setObject:self.senderUserInfo.name forKeyedSubscript:@"name"];
        }
        if (self.senderUserInfo.portraitUri) {
            [userInfoDic setObject:self.senderUserInfo.portraitUri forKeyedSubscript:@"portrait"];
        }
        if (self.senderUserInfo.userId) {
            [userInfoDic setObject:self.senderUserInfo.userId forKeyedSubscript:@"id"];
        }
        [dataDict setObject:userInfoDic forKey:@"user"];
    }
    NSData *data = [NSJSONSerialization dataWithJSONObject:dataDict options:kNilOptions error:nil];
    return data;
}

///将json解码生成消息内容
- (void)decodeWithData:(NSData *)data {
    if (data) {
        __autoreleasing NSError *error = nil;
        NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
        if (dictionary) {
            self.extra = dictionary[@"extra"];
            NSString *originContent = dictionary[@"content"];
            self.content = originContent.ib_decrypt;
            
            NSDictionary *userinfoDic = dictionary[@"user"];
            [self decodeUserInfo:userinfoDic];
        }
    }
}
#pragma clang diagnostic pop

@end

  "ib_encrypt"、"ib_decrypt"为加、解密方法。其他类型的Message也可以这样做，当然，这里我只对content做了加、解密，如果对data直接做加、解密也是可以的。
  欢迎前辈给予指点，谢谢！