Flutter IOS(swift)平台 AES8加解密（PKCS7模式）大文件 实现

1. flutter通过new plugin创建(语言要选swift)模版进行修改

encryptIos_until.dart

import 'encrypt_ios_platform_interface.dart';

export 'package:encrypt_ios/encrypt_ios_until.dart';

class EncryptIosUntil {

  String KEY;

  String IV;

  EncryptIosUntil({this.KEY = "xxxxxxxxxxxxxxxx", this.IV = "vvvvvvvvvvvvvvvv"});//这里是配置默认的key和iv，各16字节

  Future<String?> encryptStr({required String str,String? key, String? iv}){
    return EncryptIosPlatform.instance.encryptStr(key??KEY,iv??IV,str);
  }

  Future<String?> decryptStr({required String str,String? key, String? iv}){
    return EncryptIosPlatform.instance.decryptStr(key??KEY,iv??IV,str);
  }

  Future<bool?> encryptFile({required String src,required String desc,String? key, String? iv}){
    return EncryptIosPlatform.instance.encryptFile(key??KEY,iv??IV, src, desc);
  }

  Future<bool?> decryptFile({required String src,required String desc,String? key, String? iv}){
    return EncryptIosPlatform.instance.decryptFile(key??KEY,iv??IV, src, desc);
  }


}

encrypt_ios_platform_interface.dart

import 'package:plugin_platform_interface/plugin_platform_interface.dart';

import 'encrypt_ios_method_channel.dart';

abstract class EncryptIosPlatform extends PlatformInterface {

  EncryptIosPlatform() : super(token: _token);

  static final Object _token = Object();

  static EncryptIosPlatform _instance = MethodChannelEncryptIos();
  
  static EncryptIosPlatform get instance => _instance;

  static set instance(EncryptIosPlatform instance) {
    PlatformInterface.verifyToken(instance, _token);
    _instance = instance;
  }

  Future<String?> encryptStr(String key,String iv,String str){
    throw UnimplementedError('encryptStr() has not been implemented.');
  }

  Future<String?> decryptStr(String key,String iv,String str){
    throw UnimplementedError('decryptStr() has not been implemented.');
  }

  Future<bool?> encryptFile(String key,String iv,String src,String desc){
    throw UnimplementedError('encryptFile() has not been implemented.');
  }

  Future<bool?> decryptFile(String key,String iv,String src,String desc){
    throw UnimplementedError('decryptFile() has not been implemented.');
  }
}

encrypt_ios_method_channel.dart

import 'package:flutter/foundation.dart';
import 'package:flutter/services.dart';

import 'encrypt_ios_platform_interface.dart';

/// An implementation of [EncryptIosPlatform] that uses method channels.
class MethodChannelEncryptIos extends EncryptIosPlatform {
  /// The method channel used to interact with the native platform.
  @visibleForTesting
  final methodChannel = const MethodChannel('encrypt_ios');

  @override
  Future<String?> encryptStr(String key,String iv,String str) async {
    final enStr = await methodChannel.invokeMethod<String>('encryptStr',<String, dynamic>{
      'key': key,
      'iv': iv,
      'str': str
    });
    return enStr;
  }

  @override
  Future<String?> decryptStr(String key,String iv,String str) async {
    final deStr = await methodChannel.invokeMethod<String>('decryptStr',<String, dynamic>{
      'key': key,
      'iv': iv,
      'str': str
    });
    return deStr;
  }

  @override
  Future<bool?> decryptFile(String key, String iv, String src, String desc) async {
    final result = await methodChannel.invokeMethod<bool>('decryptFile',<String, dynamic>{
      'key': key,
      'iv': iv,
      'src': src,
      'desc': desc
    });
    return result;
  }

  @override
  Future<bool?> encryptFile(String key, String iv, String src, String desc) async {
    final result = await methodChannel.invokeMethod<bool>('encryptFile',<String, dynamic>{
      'key': key,
      'iv': iv,
      'src': src,
      'desc': desc
    });
    return result;
  }
}

2. 通过Xcode打开example中的ios的.xcworkspace文件打开项目（强烈建议不要在Android studio内写swift代码）

添加 s.dependency ‘CommonCryptoModule’

# To learn more about a Podspec see http://guides.cocoapods.org/syntax/podspec.html.
# Run `pod lib lint encrypt.podspec` to validate before publishing.
#
Pod::Spec.new do |s|
  s.name             = 'encrypt'
  s.version          = '0.0.1'
  s.summary          = 'A new Flutter project.'
  s.description      = <<-DESC
A new Flutter project.
                       DESC
  s.homepage         = 'http://example.com'
  s.license          = { :file => '../LICENSE' }
  s.author           = { 'Your Company' => '[email protected]' }
  s.source           = { :path => '.' }
  s.source_files = 'Classes/**/*'
  s.dependency 'Flutter'
  s.dependency 'CommonCryptoModule'
  s.platform = :ios, '9.0'

  # Flutter.framework does not contain a i386 slice.
  s.pod_target_xcconfig = { 'DEFINES_MODULE' => 'YES', 'EXCLUDED_ARCHS[sdk=iphonesimulator*]' => 'i386' }
  s.swift_version = '5.0'
end

3. 通过cmd运行（在example/ios内运行） pod install （避免导入CommonCrypto头文件产生复杂操作）

搜索Swift找到对应的.swift文件进行修改
SwiftEncrypIosPlugin.swift

import Flutter
import UIKit
import CryptoSwift
import CommonCrypto

public class SwiftEncryptIosPlugin: NSObject, FlutterPlugin {

    public static func register(with registrar: FlutterPluginRegistrar) {
        let channel = FlutterMethodChannel(name: "encrypt_ios", binaryMessenger: registrar.messenger())
        let instance = SwiftEncryptIosPlugin()
        registrar.addMethodCallDelegate(instance, channel: channel)
    }

    public func handle(_ call: FlutterMethodCall, result: @escaping FlutterResult) {

        //传入参数
        let arg = call.arguments
        //获取必要的key与iv
        if let args = arg as? [String: Any],
        let key = args["key"] as? String,
        let iv = args["iv"] as? String
        {
            let keyData = Data(bytes: key, count: key.count)
            let ivData = Data(bytes: iv, count: iv.count)
            switch call.method {//区分调用方法
                case "encryptStr":
                if let str = args["str"] as? String{
                    debugPrint("encryptStr->str:"+str)
                    let deData = aesCBC(operation: kCCEncrypt, data: Data(bytes: str.bytes, count: str.count), keyData: keyData, ivData: ivData)
                    debugPrint("encryptStr->destr:"+deData.base64EncodedString())
                    result(deData.base64EncodedString())//编码base64返回，与Android端相同
                }else{
                    result(FlutterError(code: "-1", message: "iOS could not extract " +
                                        "flutter arguments in method: (encryptStr),missing parameter 'str'", details: nil))
                }
                case "decryptStr":
                if let str = args["str"] as? String{
                    debugPrint("decryptStr->str:"+str)
                    let strData = Data(base64Encoded: str)//需要先解码base64，再进行解密
                    let deData = aesCBC(operation: kCCDecrypt, data:strData!, keyData: keyData, ivData: ivData)
                    let deStr = String(bytes: deData.bytes,encoding: String.Encoding.utf8)//转utf-8输出
                    debugPrint("decryptStr->destr:",deStr)
                    result(deStr)
                }else{
                    result(FlutterError(code: "-1", message: "iOS could not extract " +
                                        "flutter arguments in method: (encryptStr),missing parameter 'str'", details: nil))
                }
                case "encryptFile":
                if let src = args["src"] as? String,
                let desc = args["desc"] as? String{
                    var isSuccess = false
                    do{
                        isSuccess = try aesCBCFile(operation: kCCEncrypt, keyData: keyData, ivData: ivData, _srcPath: src, _descPath: desc)
                        result(isSuccess)
                    }catch{
                        result(FlutterError(code: "-1", message: error.localizedDescription, details: nil))
                    }
                }else{
                    result(FlutterError(code: "-1", message: "iOS could not extract " +
                                        "flutter arguments in method: (encryptFile),missing parameter 'src/desc'", details: nil))
                }
                case "decryptFile":
                if let src = args["src"] as? String,
                let desc = args["desc"] as? String{
                    var isSuccess = false
                    do{
                        isSuccess = try aesCBCFile(operation: kCCDecrypt, keyData: keyData, ivData: ivData, _srcPath: src, _descPath: desc)
                        result(isSuccess)
                    }catch{
                        result(FlutterError(code: "-1", message: error.localizedDescription, details: nil))
                    }
                }else{
                    result(FlutterError(code: "-1", message: "iOS could not extract " +
                                        "flutter arguments in method: (decryptFile),missing parameter 'src/desc'", details: nil))
                }
                default :
                result("iOS " + UIDevice.current.systemVersion)
            }
        }else{
            result(FlutterError(code: "-1", message: "iOS could not extract " +
                                "flutter arguments in : missing parameter(key or iv)", details: nil))
        }
    }
    // AES加解密
    public func aesCBC(operation: Int, data:Data, keyData: Data, ivData: Data) -> Data {
        let dataLength = data.count
        let cryptLength  = size_t(dataLength + kCCBlockSizeAES128)
        var cryptData = Data(count:cryptLength)

        let keyLength = size_t(kCCKeySizeAES128)
        let options = CCOptions(kCCOptionPKCS7Padding)


        var numBytesEncrypted :size_t = 0

        let cryptStatus = cryptData.withUnsafeMutableBytes {cryptBytes in
                                                            data.withUnsafeBytes {dataBytes in
                                  ivData.withUnsafeBytes {ivBytes in
                                        keyData.withUnsafeBytes {keyBytes in
                                             CCCrypt(CCOperation(operation),
                                CCAlgorithm(kCCAlgorithmAES),
                                options,
                                keyBytes, keyLength,
                                ivBytes,
                                dataBytes, dataLength,
                                cryptBytes, cryptLength,
                                &numBytesEncrypted)
                                            }
                                       }
                                 }
                                                           }

        if UInt32(cryptStatus) == UInt32(kCCSuccess) {
            cryptData.removeSubrange(numBytesEncrypted..<cryptData.count)

        } else {
            print("Error: \(cryptStatus)")
        }

        return cryptData;
    }

    public func aesCBCFile(operation: Int, keyData: Data, ivData: Data, _srcPath:String,_descPath:String) throws -> Bool{

        debugPrint("FileSrc:"+_srcPath)
        debugPrint("FileDesc:"+_descPath)

        let startTime = CFAbsoluteTimeGetCurrent()//记录方法开始时间

        if !(FileManager.default.fileExists(atPath: _srcPath)) {//判断源文件是否存在
            throw URLError(URLError.cannotWriteToFile,userInfo: ["message":"can't find file by srcPath"])
        }
        let inputStream = InputStream(fileAtPath: _srcPath)
        if inputStream == nil {//判断源文件流是否存在
            throw URLError(URLError.cannotWriteToFile,userInfo: ["message":"can't find file by srcPath"])
        }

        var srcFileSize : Int = 0
        let src = try FileManager.default.attributesOfItem(atPath: _srcPath)
        srcFileSize = Int(src[FileAttributeKey.size] as! UInt64)
        debugPrint("Begin,SrcFileSize:",srcFileSize)

        //初始化目标文件流,如果存在目标文件，进行移除
        if(FileManager.default.fileExists(atPath: _descPath)){
            try FileManager.default.removeItem(atPath: _descPath)
        }
        FileManager.default.createFile(atPath: _descPath, contents: nil)
        let outputStream = OutputStream(toFileAtPath: _descPath, append: true)!
        outputStream.open()

        //初始化加解密
        let keyLength = size_t(kCCKeySizeAES128)
        let options = CCOptions(kCCOptionPKCS7Padding)
        var cryptor: CCCryptorRef?
        //        defer {
        //            CCCryptorRelease(cryptor)
        //        }
        let status = keyData.withUnsafeBytes {keyBytes in
                                              ivData.withUnsafeBytes {ivBytes in
                                    CCCryptorCreate(CCOperation(operation), CCAlgorithm(kCCAlgorithmAES), options, keyBytes, keyLength, ivBytes, &cryptor)
                                   }
                                             }//创建加解密对象

        inputStream?.open()//开启输入流

        var bufused = 0//bufused为实际加解密所进行的字符个数
        var finalPointer:UnsafeMutablePointer<UInt8> = UnsafeMutablePointer<UInt8>.allocate(capacity: 1)//保存CCCryptorUpdate的结果
        let bufferSize = 1024*1024//缓冲区大小

        while inputStream!.hasBytesAvailable{

            let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: bufferSize)//缓冲区
            let read = inputStream!.read(buffer, maxLength: bufferSize)//读取数据流到缓冲区

            if (read == 0){
                buffer.deallocate()//清空缓冲区
                break
            }
            var readData = Data(bytes: buffer, count: read)
            var readLength  = readData.count

            let resultLength = size_t(readData.count + kCCBlockSizeAES128)//保存加解密后数组的长度
            var updateData = [UInt8](repeating: 0, count: resultLength)//保存加解密后的数据

            var cryptStatus = readData.withUnsafeBytes {readBytes in
                                                        CCCryptorUpdate(cryptor, readBytes, readLength, &updateData, resultLength , &bufused)//进行加解密
                                                       }

            if UInt32(cryptStatus) == UInt32(kCCSuccess) {
                updateData.removeSubrange(bufused..<resultLength)//保存实际进行的加解密个数，去除原本多余的字符

            } else {
                print("Error: \(cryptStatus)")
            }

            outputStream.write(updateData, maxLength: updateData.count)//写入文件

            finalPointer.initialize(from: updateData, count: 1)//记录修改,直接地址相连接，避免了内存溢出

            buffer.deallocate()//清空缓冲区
        }

        //数据读取完毕,关闭读取文件流
        inputStream!.close()

        CCCryptorFinal(cryptor, finalPointer, srcFileSize, &bufused)//通过CCCryptorFinal可以获得srcFileSize-updateResult.count大小的且合并后不影响updateResult的数组

        CCCryptorRelease(cryptor)//释放内存

        let bufferPointer = UnsafeMutableBufferPointer(start: finalPointer, count: bufused)//截取有效地址

        let result = outputStream.write(Array(bufferPointer), maxLength: bufused)//转为数组并写入文件

        //数据写入完毕,关闭写入文件流
        outputStream.close()

        var descFileSize : Int = 0
        let desc = try FileManager.default.attributesOfItem(atPath: _descPath)
        descFileSize = Int(desc[FileAttributeKey.size] as! UInt64)
        debugPrint("Finish,DescFileSize:",descFileSize)
        //记录结束时间
        let endTime = CFAbsoluteTimeGetCurrent()
        debugPrint(String(format:"aesCBCFile Function usage time ：%.2f second", (endTime - startTime)))
        return true
    }
}

4. 最重要的一点，最外层pubspec.yaml内IOS平台的要指定到自己编写的.swift文件！

pubspec.yaml

flutter:
  plugin:
  platforms:
  	# android:
  	# 	package: com.handcent.encrypt
  	# 	pluginClass: EncryptUntil
  	ios:
  		pluginClass: SwiftEncrypIosPlugin

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