Swift AES 通用加密 - AES 解密期间的前 16 个字符被省略

问题描述

尝试使用 AES（通用加密）快速执行加密和解密，由于某种原因，在解密前 16 个字符时被修剪掉了。任何人都可以看看下面的操场代码并建议这里可能出了什么问题吗？在解密过程中，decodedString 变量会修剪掉原始 payloadString 的前 16 个字符。

操场代码

import UIKit
import CommonCrypto

class AESNew {

    enum MyError: LocalizedError {
        case first(message: String)
        case second(message: String)

        var errorDescription: String? { return "Some description here!" }
    }
    
    func encrypt(plainText: String,keyData:Data,iv: Data,options:Int = kCcoptionPKCS7Padding) -> Result<Data,Error> {
        let plainData = Data(plainText.utf8)
            
        if let cryptData = NSMutableData(length: Int((plainData.count)) + kCCBlockSizeAES128) {

            let keyLength              = size_t(kCCKeySizeAES128)
            let operation: Ccoperation = UInt32(kCCEncrypt)
            let algoritm:  CCAlgorithm = UInt32(kCCAlgorithmAES128)
            let options:   Ccoptions   = UInt32(options)
            
            var numBytesEncrypted :size_t = 0
            
            //let value = iv.withUnsafeBytes { $0.load(as: UInt32.self) }
            
            let cryptResult = iv.withUnsafeBytes { (dataBytes : UnsafePointer<UInt8>) -> Result<Data,Error> in
                
                print(dataBytes)
                
                print(UnsafeRawPointer(dataBytes))
                
                let cryptStatus = CCCrypt(operation,algoritm,options,(keyData as NSData).bytes,keyLength,UnsafeRawPointer(dataBytes),(plainData as NSData).bytes,plainData.count,cryptData.mutableBytes,cryptData.length,&numBytesEncrypted)
                
                if UInt32(cryptStatus) == UInt32(kCCSuccess) {
                    cryptData.length = Int(numBytesEncrypted)
                    let base64cryptString = cryptData.base64EncodedString(options: .lineLength64Characters)
                    print("base64cryptString: \(base64cryptString)")
                    return .success(cryptData as Data)
                } else {
                    print("failure")
                    return .failure(MyError.first(message: "crypt Failed"))
                }
            }
            
            return cryptResult
        
        }
        return .failure(MyError.second(message: "no value failure"))
    }

    // The iv is prefixed to the encrypted data
    func decrypt(data: Data,keyData: Data) throws -> Data? {
        let keyLength = keyData.count
        let validKeyLengths = [kCCKeySizeAES128,kCCKeySizeAES192,kCCKeySizeAES256]
        if validKeyLengths.contains(keyLength) == false {
            print("validKeyLengths does not match")
        }

        let ivSize = kCCBlockSizeAES128
        let clearLength = size_t(data.count - ivSize)
        var clearData = Data(count: clearLength)

        var numBytesDecrypted: size_t = 0
        let options   = Ccoptions(kCcoptionPKCS7Padding)

        let cryptStatus = clearData.withUnsafeMutableBytes {cryptBytes in
            data.withUnsafeBytes {dataBytes in
                keyData.withUnsafeBytes {keyBytes in
                    CCCrypt(Ccoperation(kCCDecrypt),CCAlgorithm(kCCAlgorithmAES128),keyBytes,dataBytes,dataBytes+kCCBlockSizeAES128,clearLength,cryptBytes,&numBytesDecrypted)
                }
            }
        }
        
        if UInt32(cryptStatus) == UInt32(kCCSuccess) {
            clearData.count = numBytesDecrypted
        } else {
            print("Decryption Failed")
        }
        return clearData
    }
}

func randomGenerateBytes(count: Int) -> Data? {
    let bytes = UnsafeMutableRawPointer.allocate(byteCount: count,alignment: 1)
    defer { bytes.deallocate() }
    let status = CCRandomGenerateBytes(bytes,count)
    guard status == kCCSuccess else { return nil }
    return Data(bytes: bytes,count: count)
}

var ivBytesNew = Data()

if let ivBytes = randomGenerateBytes(count: 16) {
    ivBytesNew = ivBytes
} else {
    print("randomGenerateBytes Failed")
}

let keyString   = "keyData890123456"
let keyData   = "keyData890123456".data(using:String.Encoding.utf8)!

let payloadString = "asdflkasfdkaslfd12345"

let aesObject = AESNew()

let encrytedobject = aesObject.encrypt(plainText: payloadString,keyData: keyData,iv: ivBytesNew,options: kCcoptionPKCS7Padding)

var encryptedData = Data()

switch encrytedobject {
case .success(let encData):
    print(encData)
    encryptedData = encData
case .failure(let error):
    print(error)
default:
    print("enc Failed")
}

if let decrypedData = try? aesObject.decrypt(data: encryptedData,keyData: keyData) {
    if let decodedString = String(data: decrypedData,encoding: .utf8) {
        print(decodedString) // 1234,first 16 characters are omitted. 
    } else {
        print("conversion from data to string Failed")
    }
} else {
    print("decryption Failed")
}

解决方法

看来你已经学会了两种不同的加密和解密。

您是否看到您的 decrypt 没有 AES 解密所需的参数 iv？

您的 decrypt 期望 data 的前 16 个字节为 iv，其余为加密数据。但是您的 encrypt 只返回加密数据。

请尝试将调用 decrypt 的线路更改如下：

if let decrypedData = try? aesObject.decrypt(data: ivBytesNew + encryptedData,keyData: keyData) {

---

通常，您的 encrypt 使用 NSMutableData 并不当处理 bytes。这是脆弱的，它可能会在某些不同的上下文中崩溃。我强烈建议您不要使用当前的 encrypt。

无论如何，你应该使 encrypt 和 decrypt 一致，或者说是对称的，目前它们不是。