加密要通过 Amazon S3 发送的大型流

Question

我想加密流，然后使用 Amazon S3 发送它。我正在使用遗留代码并有两个重要参数：未加密的InputStream 及其长度。这很重要，因为 AmazonS3Client 想在上传流之前知道流的长度。

加密流并不是很困难的任务：

        InputStream in = new FileInputStream("path-to-file");
        KeyGenerator keygen = KeyGenerator.getInstance("AES");
        Key key = keygen.generateKey();

        Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
        cipher.init(Cipher.ENCRYPT_MODE, key);

        OutputStream encryptedStream = new ByteArrayOutputStream();
        CipherOutputStream out = new CipherOutputStream(encryptedStream, cipher);
        out.write(in.read());
        out.flush();

        byte[] bytes = ((ByteArrayOutputStream) encryptedStream).toByteArray();
        InputStream encryptedInput = new ByteArrayInputStream(bytes);

但是，这种方法只能用于小文件，因为它们被写入内存中的字节数组。问题是我想加密大文件（> 1TB）。我该怎么做呢？更具体地说，我得到 InputStream，我的工作是返回将由 Amazon S3 使用的加密 InputStream。

Answer 1

不要使用ByteArrayOutputStream

    InputStream in = new FileInputStream("path-to-file");
    KeyGenerator keygen = KeyGenerator.getInstance("AES");
    Key key = keygen.generateKey();

    Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
    cipher.init(Cipher.ENCRYPT_MODE, key);

    try(CipherOutputStream out = new CipherOutputStream(
            new FileOutputStream(new File("path to enc file")), cipher))
    {
        byte[] buffer = new byte[8192];
        int count;
        while ((count = in.read(buffer)) > 0)
        {
            out.write(buffer, 0, count);
        }
    }

    return new FileInputStream(new File("path to enc file"));

管道流的另一个答案。

    InputStream in = new FileInputStream("path-to-file");
    KeyGenerator keygen = KeyGenerator.getInstance("AES");
    Key key = keygen.generateKey();

    Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
    cipher.init(Cipher.ENCRYPT_MODE, key);

    PipedOutputStream pout = new PipedOutputStream();
    //write data in a separate thread.
    new Thread(() -> {
        try(CipherOutputStream out = new CipherOutputStream(
                pout, cipher))
        {
            byte[] buffer = new byte[8192];
            int count;
            while ((count = in.read(buffer)) > 0)
            {
                out.write(buffer, 0, count);
            }
        } catch (IOException  e)
        {
            e.printStackTrace();
        }
    }).start();

    return new PipedInputStream(pout);