java - 无法下载整个解密的txt文件

Question

我正在编写一个小型测试应用程序。事情是...... Servlet 将任何 AES 加密文件下载到我的 table ​​面应用程序。然后我的桌面应用程序将其解密并保存在本地硬盘上。它对于二进制视频、图像等工作正常，但由于某种原因，我从 txt 文件中丢失了字符。据我所知，任何 txt 文件都缺少最后 128 位(最后 15 或 16 个字符)。

我不知道为什么会发生这种情况，所以我需要你的建议

这是 servlet 代码:

final int BUFFER_SIZE = 4096;
FileInputStream in = new FileInputStream(file);
OutputStream out = response.getOutputStream();
byte buffer[] = new byte[BUFFER_SIZE];

for (int nread = 0; (nread = in.read(buffer)) != -1;) {
    out.write(buffer, 0, nread);
}

out.flush();
out.close();
in.close();

桌面应用程序代码片段:

response = httpclient.execute(httppost);//it is HttpClient 4...
resEntity = response.getEntity();
InputStream in = resEntity.getContent();
in = new CipherInputStream(in, decipher);//maybe the aes block missing here...
FileOutputStream out= new FileOutputStream(path);
byte[] buffer = new byte[4096];
int numRead = 0;

while ((count = in.read(buffer)) != -1) {
    out.write(buffer, 0, count);
}

out.flush();
out.close();

这就是我解密的方式:

KeyGenerator kgen = KeyGenerator.getInstance("AES");
          kgen.init(128);
          key = kgen.generateKey();

    byte[] ivar = new byte[]
                      {
                          0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f
                  };
AlgorithmParameterSpec params = new IvParameterSpec(ivar );
dcipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
dcipher.init(Cipher.DECRYPT_MODE, key, params );

...这是桌面应用程序上传片段

HttpPost httppost = null;
        HttpResponse response=null;
        HttpEntity resEntity=null;

        try {
          File file = filePath;
          fileLength=file.length();

          HttpClient httpclient = new DefaultHttpClient();
          httpclient.getParams().setParameter(CoreProtocolPNames.
                                              PROTOCOL_VERSION,
                                              HttpVersion.HTTP_1_1);


          String url="http://localhost:8080/testUrl";
          httppost = new HttpPost(url);

String name=file.getName();
InputStreamBody inputStreamBody=new InputStreamBody(new FileInputStream(file),name);

MultiPartEntity multiPartEntity = new MultiPartEntity();
multiPartEntity .addPart("file-name", new StringBody(name, Charset.forName("UTF-8")));
multiPartEntity .addPart("file-stream", inputStreamBody);

和 InputStreamBody writeTo 方法(您可以在此处查看文档 http://hc.apache.org/httpcomponents-client-ga/httpmime/clover/org/apache/http/entity/mime/content/InputStreamBody.html )...

    byte[] ivar = new byte[]
                      {
                              0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f
                      };

    ...
    AlgorithmParameterSpec params = new IvParameterSpec(ivar);

    encipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
    encipher .init(Cipher.ENCRYPT_MODE, key, params);

...

public void writeTo(final OutputStream out) throws IOException {
              if (out == null) {
                  throw new IllegalArgumentException("Output stream may not be null");
              }
              try {

              out = new CipherOutputStream(out, encipher );


              int numRead = 0;
              while ( (count = in.read(buf)) !=-1) {
                out.write(buf, 0, count);


              }
              out.flush();
              in.close();

            }
            catch (java.io.IOException e) {
            }
          }

请帮我解决解密问题。也许二进制文件也丢失了 128 位，但除了文本文件内容之外，这并没有那么引人注目:(我听说这可能是由于不正确的序列流关闭等原因造成的，但我不确定。

听说可能是InputStreamBody内容长度问题，方法:

public long getContentLength() {

             return -1;


         }

但是如果由于加密而导致“in.length!=out.length”，如何正确设置修改后的输出长度(请参阅 writeTo 方法)？

请帮我解决这个问题

任何有用的评论都会受到赞赏:)

Answer 1

因此，我制作了一个测试程序来看看它是如何工作的(见下文)。

它创建这个文件:

O thou, my lovely boy, who in thy power
Dost hold Time's fickle glass, his sickle, hour;
Who hast by waning grown, and therein show'st
Thy lovers withering as thy sweet self grow'st;
If Nature, sovereign mistress over wrack,
As thou goest onwards, still will pluck thee back,
She keeps thee to this purpose, that her skill
May time disgrace and wretched minutes kill.
Yet fear her, O thou minion of her pleasure!
She may detain, but not still keep, her treasure:
Her audit, though delay'd, answer'd must be,
And her quietus is to render thee.

看起来完整(diff 表示它与输入相同)。

为什么你的程序似乎会切断某些东西，我不知道。

您在问题中放入的代码无法编译(需要进行一些修改，请参见下文)，并且还使用随 secret 钥(来自 key 生成器)而不是用于加密示例文本文件的 key 。为了重现性，我在下面的示例中使用了固定 key ，但使用随 secret 钥它也会生成相同的解密文件(显然是另一个加密文件)。

在您的输入文件上运行该类，并将其加密输出与您的加密文件(在服务器和客户端上)进行比较。也许这将有助于找到问题。

这里是示例代码。main 方法接受三个文件名作为参数，第一个是原始文件(并且必须存在)，第二个是加密文件，第三个是解密文件(如果存在，都将被覆盖)。如果给出第四个参数，它将使用随 secret 钥。

package de.fencing_game.paul.examples;

import java.io.*;
import java.security.*;
import java.security.spec.*;
import javax.crypto.*;
import javax.crypto.spec.*;

public class EncryptDecrypt {


    AlgorithmParameterSpec params;

    public EncryptDecrypt()
        throws Exception
    {
        byte[] ivar = new byte[] {
            0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
            0x08, 0x09,0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f
        };
        params = new IvParameterSpec(ivar );
    }


    public void encrypt(SecretKey key, File from, File to)
        throws  Exception
    {
        Cipher ourCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        ourCipher.init(Cipher.ENCRYPT_MODE, key, params );
        crypt(ourCipher, from, to);
    }

    public void decrypt(SecretKey key, File from, File to)
        throws Exception
    {
        Cipher ourCipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        ourCipher.init(Cipher.DECRYPT_MODE, key, params );
        crypt(ourCipher, from, to);
    }


    private void crypt(Cipher c, File from, File to) 
        throws IOException
    {
        InputStream in = new CipherInputStream(new FileInputStream(from), c);
        OutputStream out = new FileOutputStream(to);
        copyStream(in, out);
    }

    private void copyStream(InputStream in, OutputStream out)
        throws IOException
    {
        byte[] buffer = new byte[4096];
        int count = 0;

        while ((count = in.read(buffer)) != -1) {
            out.write(buffer, 0, count);
        }
        out.flush();
        out.close();
        in.close();
    }


    public static void main(String[] params)
        throws Exception
    {
        EncryptDecrypt ed = new EncryptDecrypt();

        if(params.length > 3) {
            KeyGenerator kgen = KeyGenerator.getInstance("AES");
            kgen.init(128);
            SecretKey key = kgen.generateKey();
        }
        else {
            SecretKeyFactory factory = SecretKeyFactory.getInstance("AES");
            // AES needs 128 bits = 16 bytes
            KeySpec spec =
                new SecretKeySpec("Test-KeyTest-Key".getBytes("US-ASCII"),
                                  "AES");
            System.out.println(spec);

            SecretKey key = factory.generateSecret(spec);
            System.out.println(key);
        }


        ed.encrypt(key, new File(params[0]), new File(params[1]));
        ed.decrypt(key, new File(params[1]), new File(params[2]));
    }

}