PDF证书无效：“文档自签署后已被更改或损坏”

Question

我正在为我的应用程序做一个PDF签名功能。以下是工作流程：

1. PDF存储在服务器上。
2. 我将所有必需的签名字段包含到文件中，并使用ZendPDF的扩展名为FaritPDF计算字节长度等。
3. 我根据使用SHA256计算的字节长度计算哈希。
4. 哈希将发送到客户端。
5. 客户端使用PFX文件对哈希进行签名，并创建包含哈希的PKCS7对象。
6. 将PKCS7对象发送到服务器。
7. PKCS7对象包含在PDF中，并呈现PDF。

这导致我出现以下错误：“Document has been altied or corrupted sond it was signed”。ByteRange是正确的，我没有修改任何字节的文件。我正在使用与Acrobat Reader相同的算法。我会做错什么？

这是我的PDF文件，很抱歉我不能从工作中上传：

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%âãÏÓ

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( This is a small demonstration .pdf file - ) Tj
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( just for use in the Virtual Mechanics tutorials. More text. And more ) Tj
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( text. And more text. And more text. And more text. ) Tj
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( And more text. And more text. And more text. And more text. And more ) Tj
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( text. And more text. Boring, zzzzz. And more text. And more text. And ) Tj
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( text. And more text. And more text. Even more. Continued on page 2 ...) Tj
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( ...continued from page 1. Yet more text. And more text. And more text. ) Tj
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( And more text. And more text. And more text. And more text. And more ) Tj
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( text. Oh, how boring typing this stuff. But not as boring as watching ) Tj
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( paint dry. And more text. And more text. And more text. And more text. ) Tj
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( Boring.  More, a little more text. The end, and just as well. ) Tj
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Answer 1

您没有修改文件的任何字节的断言与步骤7相矛盾。您可能希望区分步骤7的before和after,并确保将PKCS7对象写入文件的部分,该部分不是用于计算哈希的byterange的一部分。