使用 AES 256 CBC 解密 pdf 文件给出不可读的输出

Question

我有一些加密的 PDF 文件列表。单击每个 pdf 文件后，它应该使用 PDF.Js 使用 AES 256 CBC 进行解密和查看。我有以下代码（抱歉，它有点长，我在 JSFiddle 中尝试过，但遇到了保存和附加加密和解密文件的问题）：

app.php

<?php

if($_POST['action'] == 'encrypt') {
    my_encrypt($_POST['filename']);
}

if($_POST['action'] == 'decrypt') {
    $result = my_decrypt($_POST['filename']);
    echo $result;
}

function my_encrypt($filename) {
    
    $filedata = file_get_contents($filename);
    // Remove the base64 encoding from our key
    $key = '8479768f48481eeb9c8304ce0a58481eeb9c8304ce0a5e3cb5e3cb58479768f4';
    $encryption_key = base64_decode($key);
    // Generate an initialization vector
    $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length('aes-256-cbc'));
    // Encrypt the data using AES 256 encryption in CBC mode using our encryption key and initialization vector.
    $encrypted = openssl_encrypt($filedata, 'aes-256-cbc', $encryption_key, 0, $iv);
    // The $iv is just as important as the key for decrypting, so save it with our encrypted data using a unique separator (::)
    $result =  base64_encode($encrypted . '::' . $iv);
    $file = fopen('./files/Sampleencrypt.pdf', 'wb');
    fwrite($file, $result);
    fclose($file);
    echo $result;
    return $result;
}

function my_decrypt($filename) {
    $filedata = file_get_contents($filename);
    // Remove the base64 encoding from our key
    $key = '8479768f48481eeb9c8304ce0a58481eeb9c8304ce0a5e3cb5e3cb58479768f4';
    $encryption_key = base64_decode($key);
    // To decrypt, split the encrypted data from our IV - our unique separator used was "::"
    list($encrypted_data, $iv) = explode('::', base64_decode($filedata), 2);
    $result = openssl_decrypt($encrypted_data, 'aes-256-cbc', $encryption_key, 0, $iv);

    return $result;
}
?>

index.html

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <title></title>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <script src="build/pdf.js"></script>
    <link rel="stylesheet" href="style.css">

    <script>
        function encrypt(filename){
           
            $.ajax({
                type: "POST",
                url: "app.php",
                data: { action:'encrypt', filename: filename }
            }).done(function( msg ) {
                alert( "Data returned: " + msg );
            });

            return false;
        }

        function decrypt(filename){
            
           $.ajax({
               type: "POST",
               url: "app.php",
               data: { action:'decrypt', filename: filename },
               success: function (response) {
                alert(response);
                showPdf(response);
                }
            })
           return false;
       }
    </script>
</head>
<body>
    
    <a href="./files/Sampleencrypt.pdf" onclick="return decrypt(this.href);">Decrypt Sample</a> </br>
    <a href="./files/A Sample PDF.pdf" onclick="return encrypt(this.href);">Encrypt Sample</a><br>
    <br>
    
    <h1>PDF.js Previous/Next example</h1>
    <div>
      <button id="prev">Previous</button>
      <button id="next">Next</button>
      &nbsp; &nbsp;
      <span>Page: <span id="page_num"></span> / <span id="page_count"></span></span>
    </div>
    <div>
        <canvas id="can"></canvas>
    </div>
    <script type="text/javascript" src="test.js"></script>
</body>
</html>

test.js

var canvas = document.getElementById('can');
var context = canvas.getContext('2d');

var pdfDoc = null,
  pageNum = 1,
  pageRendering = false,
  pageNumPending = null,
  scale = 1.5;

  function renderPage(num) {
    pageRendering = true;
    // Using promise to fetch the page
    pdfDoc.getPage(num).then(function(page) {
      var viewport = page.getViewport({scale: scale});
      canvas.height = viewport.height;
      canvas.width = viewport.width;
  
      // Render PDF page into canvas context
      var renderContext = {
        canvasContext: context,
        viewport: viewport
      };
      var renderTask = page.render(renderContext);
  
      // Wait for rendering to finish
      renderTask.promise.then(function() {
        pageRendering = false;
        if (pageNumPending !== null) {
          // New page rendering is pending
          renderPage(pageNumPending);
          pageNumPending = null;
        }
      });
    });
  
    // Update page counters
    document.getElementById('page_num').textContent = num;
  }

function queueRenderPage(num) {
    if (pageRendering) {
      pageNumPending = num;
    } else {
      renderPage(num);
    }
  }
  
  function onPrevPage() {
    if (pageNum <= 1) {
      return;
    }
    pageNum--;
    queueRenderPage(pageNum);
  }
  document.getElementById('prev').addEventListener('click', onPrevPage);
  
  function onNextPage() {
    if (pageNum >= pdfDoc.numPages) {
      return;
    }
    pageNum++;
    queueRenderPage(pageNum);
  }
  document.getElementById('next').addEventListener('click', onNextPage);


function showPdf(pdfData){
      // Loaded via <script> tag, create shortcut to access PDF.js exports.
      var pdfjsLib = window['pdfjs-dist/build/pdf'];
      
      // The workerSrc property shall be specified.
      pdfjsLib.GlobalWorkerOptions.workerSrc = './build/pdf.worker.js';
      
      // Using DocumentInitParameters object to load binary data.
      var loadingTask = pdfjsLib.getDocument({data: pdfData});
      loadingTask.promise.then(function(pdf) {
        console.log('PDF loaded');
        
        pdfDoc = pdf;
        //display total page number.
        document.getElementById('page_count').textContent = pdf.numPages;

        renderPage(pageNum);
      }, function (reason) {
        // PDF loading error
        console.error(reason);
      });

}

我正在使用 PDFJS（文档中的 base64 编码 PDF 示例）来显示 pdf 文件。有些文件可以使用此功能（非常小的示例文件）。但是对于其他pdf文件，加密文件的解密给出了字符串输出，其中一些文本不可读（如S��*��AK��^��0）并且它们使用pdf.js加载但是没有得到显示。如果我将这个解密的输出保存在一个文件中并打开该文件，它是预期的。只有 PDFJS 无法显示它。我没有得到确切的问题。问题出在解密还是 PDFJS 代码中？请帮忙。

Answer 1

得到解决方案，将解密文件结果转换为base64，并在PDF.js中解码这个base-64编码的字符串。添加了以下代码：

app.php

    function my_decrypt($filename) {
    $filedata = file_get_contents($filename);
    // Remove the base64 encoding from our key
    $key = '8479768f48481eeb9c8304ce0a58481eeb9c8304ce0a5e3cb5e3cb58479768f4';
    $encryption_key = base64_decode($key);
    // To decrypt, split the encrypted data from our IV - our unique separator used was "::"
    list($encrypted_data, $iv) = explode('::', base64_decode($filedata), 2);
    $result = openssl_decrypt($encrypted_data, 'aes-256-cbc', $encryption_key, 0, $iv);
    $result =  base64_encode($result);
    return $result;
}

test.js

    function showPdf(pdfData){
    
      // Loaded via <script> tag, create shortcut to access PDF.js exports.
      var pdfjsLib = window['pdfjs-dist/build/pdf'];
      
      // The workerSrc property shall be specified.
      pdfjsLib.GlobalWorkerOptions.workerSrc = './build/pdf.worker.js';
      
      // Using DocumentInitParameters object to load binary data.
      var loadingTask = pdfjsLib.getDocument({data: atob(pdfData)});
      loadingTask.promise.then(function(pdf) {
        console.log('PDF loaded');
        
        pdfDoc = pdf;
        //display total page number.
        document.getElementById('page_count').textContent = pdf.numPages;

        renderPage(pageNum);
      }, function (reason) {
        // PDF loading error
        console.error(reason);
      });

}

谢谢！

使用 AES 256 CBC 解密 pdf 文件给出不可读的输出

Decryption of pdf file using AES 256 CBC gives non readable output

javascript

php

pdf

aes

pdf.js