使用Facebook conceal解密文件时出现OutOfMemoryException异常

Question

我正在开发一个Android应用程序，需要将视频保存在SD卡中，并且不能被转移，这就是为什么我会根据需要使用Facebook Conceal进行加密和解密，如果视频大小较小，则完美运行。但是，当我尝试对大于10MB的视频文件进行加密和解密时，在GenyMotion 2.3.7上会崩溃，并显示OutOfMemoryException，这意味着我正在耗尽分配给我的应用程序的堆内存，这无法处理，但必须予以预防。

已尝试：

- Apache Common Utils IO包 - 各种IO Utils

Facebook Conceal：在解密时表示。

 You must read the entire stream to completion.
 The verification is done at the end of the stream.
 Thus not reading till the end of the stream will cause
 a security bug. For safety, you should not
 use any of the data until it's been fully read or throw
 away the data if an exception occurs.

我正在调用的代码使用 Facebook Conceal 进行加密和解密：

加密：

public void startEncryption() {
    // Creates a new Crypto object with default implementations of
    // a key chain as well as native library.
    // Check for whether the crypto functionality is available
    // This might fail if android does not load libaries correctly.
    if (!crypto.isAvailable()) {
        return;
    }
    OutputStream fileStream;
    try {
        File mEncryptedFile = new File(mPlainFile.getPath().substring(0,
                mPlainFile.getPath().length() - 4)
                + "_encrypted"
                + mPlainFile.getPath().substring(
                        mPlainFile.getPath().length() - 4,
                        mPlainFile.getPath().length()));

        fileStream = new BufferedOutputStream(new FileOutputStream(
                mEncryptedFile));

        // Creates an output stream which encrypts the data as
        // it is written to it and writes it out to the file.
        OutputStream outputStream;
        outputStream = crypto.getCipherOutputStream(fileStream, entity);
        outputStream.write(FileUtils.readFileToByteArray(mPlainFile));
        // fileStream.flush();
        // fileStream.close();
        // outputStream.flush();
        // outputStream.close();
        // outputStream.flush();
        File mRenameTo = new File(mPlainFile.getPath());
        mPlainFile.delete();
        mEncryptedFile.renameTo(mRenameTo);
    } catch (FileNotFoundException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (CryptoInitializationException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (KeyChainException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

Decryption :

public String startDecryption() {
    // Get the file to which ciphertext has been written.
    try {
        FileInputStream fileStream = new FileInputStream(mPlainFile);

        // Creates an input stream which decrypts the data as
        // it is read from it.
        InputStream inputStream;
        inputStream = crypto.getCipherInputStream(fileStream, entity);

        ByteArrayOutputStream out = new ByteArrayOutputStream();
        // org.apache.commons.io.output.ByteArrayOutputStream out = new
        // org.apache.commons.io.output.ByteArrayOutputStream(1024);
        // Read into a byte array.
        // int read;
        // byte[] buffer = new byte[1024];
        // // You must read the entire stream to completion.
        // // The verification is done at the end of the stream.
        // // Thus not reading till the end of the stream will cause
        // // a security bug.
        // int i = 0;
        // while ((read = inputStream.read(buffer)) != -1) {
        // out.write(buffer, 0, read);
        // Log.i(TAG, "bytearrayoutputstream "+i++ + " "+read + " " +
        // buffer.length + " "+out.size());
        // }

        mDecryptedFile = new File(mPlainFile.getPath().substring(0,
                mPlainFile.getPath().length() - 4)
                + "_decrypted"
                + (mPlainFile.getPath().substring(mPlainFile.getPath()
                        .length() - 4, mPlainFile.getPath().length())));

        OutputStream outputStream = new FileOutputStream(mDecryptedFile);
        // IOUtils.copy(inputStream, outputStream);

        try {
            final byte[] buffer = new byte[1024];
            int read;

            while ((read = inputStream.read(buffer)) != -1)
                outputStream.write(buffer, 0, read);

            outputStream.flush();
        } catch (Exception e) {

        } finally {
            outputStream.close();
        }

        // out.writeTo(outputStream);
        // out.flush();
        // out.close();

        // fileStream.close();
        inputStream.close();
        // outputStream.flush();
        outputStream.close();
        return mDecryptedFile.getPath();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (CryptoInitializationException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (KeyChainException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return null;
}

有没有可以解决并加密和解密大型视频文件的解决方案？

- Vikalp Patel

Answer 1

看起来你是将整个文件读入一个字节数组中。你应该创建一个输入流并将其提供给加密引擎。

所以，代码应该改为：

 outputStream.write(FileUtils.readFileToByteArray(mPlainFile));

应该与你的解密循环类似。

BufferedInputStream  bis = new BufferedInputStream(mPlainFile);
InputStream inputStream = crypto.getCipherInputStream(
                             bis,
                             entity);
while ((read = inputStream.read(buffer)) != -1) {
   outputStream.write(buffer, 0, read);
}

不确定您最终得到的是否是这个。我从文档中提取了加密解码部分。我认为这证实了他们的意图是说必须读取流直到结束。

- Bruce

---

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正如Facebook在其文档中明确指出的那样：“您必须完全读取整个流。验证是在流的末尾完成的。因此，如果不读取到流的末尾，将会导致安全漏洞。为了安全起见，在完全读取数据之前不应使用任何数据，或者在发生异常时丢弃数据。”，可以将其表述为Stream没有解密文件。 - Vikalp Patel

@Bruce的回答应该是可行的。Facebook说必须完整地读取整个流，但不必将整个文件加载到内存中。这意味着如果发生任何错误，您应该删除已生成的文件，因为它不安全。 - Anton Krosnev

@AntonK。谢谢AntonK。我已经尝试阅读它，就像Bruce所说的那样，但不幸的是它导致了无法解密表单。如果您知道其他方法，那将非常有帮助 :) - Vikalp Patel

Answer 2

正如Bruce所强调的，加密瓶颈会导致在解密时出现OutOfMemoryException。因此，这里是我在加密和解密时执行的代码，不再导致OutOfMemoryException。

加密：

fileStream = new BufferedOutputStream(new FileOutputStream(mEncryptedFile));
OutputStream outputStream;
outputStream = crypto.getCipherOutputStream(fileStream, entity);
int read;
byte[] buffer = new byte[1024];
BufferedInputStream  bis = new BufferedInputStream(newFileInputStream(mPlainFile));
while ((read = bis.read(buffer)) != -1) {
       outputStream.write(buffer, 0, read);
    }
outputStream.close();
bis.close();

解密：

InputStream inputStream;
inputStream = crypto.getCipherInputStream(fileStream, entity);
ByteArrayOutputStream out = new ByteArrayOutputStream();
OutputStream outputStream = new FileOutputStream(mDecryptedFile);
BufferedInputStream bis = new BufferedInputStream(inputStream);
int mRead;
byte[] mBuffer = new byte[1024];
while ((mRead = bis.read(mBuffer)) != -1) {
   outputStream.write(mBuffer, 0, mRead);
    }
bis.close();
out.writeTo(outputStream);
inputStream.close();
outputStream.close();
out.close();

- Vikalp Patel