无法使用使用 Java 加密的 Obj-C 解密 AES 数据

Question

我一直在尝试解密一些由服务器发送到我的应用程序的 AES 加密数据。

为了解决问题，我编写了一个小型 Java 程序来模拟服务器正在做什么。它使用 AES 加密一些测试数据，然后将其编码为 Base64：

AesCipherService cipherService  = new AesCipherService();
cipherService.setKeySize(128);

String stringKey = "2EE1F10212ADD4BE";
byte[] keyAsBytes =  stringKey.getBytes();

String text = "text to encrypt";
byte[] encryptedBytes    = cipherService.encrypt(text.getBytes(), keyAsBytes).getBytes();
String base64String      = Base64.encodeToString(encryptedBytes);
System.out.println(base64String);

// Reverse the process to check can retrieve "text to encrypt":
byte[] bytesToDecode = Base64.decode(base64String);
byte[] decryptedBytes = cipherService.decrypt(bytesToDecode, keyAsBytes).getBytes();         
String decryptedString = new String(decryptedBytes);   
System.out.println(decryptedString);

运行时输出如下：

R5UBpP30YjX9Ae2HoPb2Rrfi5rQJY2d0ac1+zaIX5A4=

要加密的文本

这样我就可以成功加密数据，打印出来。然后，如果我将其解密，则会显示原始文本，因此这里一切正常。

现在这是我的 Obj-C 代码，我尝试在其中解密从 Java 代码加密的数据。我已从 NetBeans IDE 输出窗口复制/粘贴加密数据作为要解密的 obj-c 内容的源数据：

- (void) decryptData
{
    NSData* dataToDecrypt       = [[NSData alloc] initWithBase64EncodedString: @"R5UBpP30YjX9Ae2HoPb2Rrfi5rQJY2d0ac1+zaIX5A4="  options: 0];
    NSString* key               = @"2EE1F10212ADD4BE";

    char keyPtr[kCCKeySizeAES128];
    bzero(keyPtr, sizeof(keyPtr));
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

    NSUInteger dataLength = [dataToDecrypt length];
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);

    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                          kCCAlgorithmAES,
                                          kCCOptionPKCS7Padding,
                                          keyPtr,
                                          kCCBlockSizeAES128,
                                          keyPtr,
                                          [dataToDecrypt bytes],
                                          dataLength,
                                          buffer,
                                          bufferSize,
                                          &numBytesDecrypted);
    if (cryptStatus == kCCSuccess) {
        NSLog(@"Success");
        NSData* unencryptedData = [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
        Byte *unencryptedAsBytes = (Byte*)malloc(unencryptedData.length);
        memcpy(unencryptedAsBytes, [unencryptedData  bytes], unencryptedData.length);
        NSString *decryptedString = [NSString stringWithUTF8String:[unencryptedData bytes]];
        NSLog(@"%@", decryptedString);
    }
}

运行时，状态为 kCCSuccess，numBytesDecrypted 为 32（与 dataLength 相同），但解密后的字符串不是“要加密的文本”，decryptedString 为 nil，如果我在 Xcode 的控制台中输入 unencryptedAsBytes，它会显示：

"\aY|\376\347cD*\320NC\x14\x91C\x88\301\341z\xaca\x11\371

知道这里有什么问题吗？

Answer 1

Java 加密代码生成一个随机 IV 并用它作为加密的前缀。为了解密，IV 从加密中分离出来。

十六进制：

key:       32454531463130323132414444344245  
iv:        479501A4FDF46235FD01ED87A0F6F646 (first 16 binary bytes of the full encryption)  
encrypted: B7E2E6B40963677469CD7ECDA217E40E (rest of binary bytes of the full encryption)  
decrypted: 7465787420746F20656E6372797074

代码：

NSData* fullEncrypted       = [[NSData alloc] initWithBase64EncodedString: @"R5UBpP30YjX9Ae2HoPb2Rrfi5rQJY2d0ac1+zaIX5A4="  options: 0];
NSData *ivData = [fullEncrypted subdataWithRange:NSMakeRange(0, kCCBlockSizeAES128)];
NSData *encryptedData = [fullEncrypted subdataWithRange:NSMakeRange(kCCBlockSizeAES128, fullEncrypted.length-kCCBlockSizeAES128)];
NSLog(@"ivData:          %@", ivData);
NSLog(@"encryptedData:   %@", encryptedData);

NSData *keyData = [@"2EE1F10212ADD4BE" dataUsingEncoding:NSUTF8StringEncoding];
NSLog(@"keyData:         %@", keyData);

NSMutableData *unencryptedData = [NSMutableData dataWithLength:encryptedData.length];
size_t numBytesDecrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                      kCCAlgorithmAES,
                                      kCCOptionPKCS7Padding,
                                      keyData.bytes, keyData.length,
                                      ivData.bytes,
                                      encryptedData.bytes, encryptedData.length,
                                      unencryptedData.mutableBytes, unencryptedData.length,
                                      &numBytesDecrypted);
if (cryptStatus == kCCSuccess) {
    NSLog(@"Success");

    unencryptedData.length = numBytesDecrypted;
    NSLog(@"unencryptedData: %@", unencryptedData);

    NSString *decryptedString = [[NSString alloc] initWithData:unencryptedData encoding:NSUTF8StringEncoding];
    NSLog(@"decryptedString: %@", decryptedString);
}

输出：

ivData:          479501a4 fdf46235 fd01ed87 a0f6f646  
encryptedData:   b7e2e6b4 09636774 69cd7ecd a217e40e  
keyData:         32454531 46313032 31324144 44344245  
Success  
unencryptedData: 74657874 20746f20 656e6372 79707400  
decryptedString: text to encrypt