Use Gmail to crack protected PDF files

Gmail functions are being improved and improved. For example, in Gmail, we can not only open the image in the attachment of the email, but also directly open PDF and other files. This is a very practical function for users who do not have a PDF Reader installed. That is to say, when you need to open a PDF file, but the PDF reader is not installed on your computer, you can send the PDF file to your Gmail in the form of an email attachment, then use Gmail to directly view the PDF document and open it. But Gmail can do more than that. It can also be used to crack some protected PDF files.

Andreas (via BoingBoing) recently found that Gmail can directly crack some protected PDF files. For example, some PDF documents are encrypted and can only be read, but cannot be printed or copied. However, using the direct viewing function of Gmail attachments can make these encryption functions useless. Below is my own test.

1. Find a protected PDF document. For example, Adobe officially provides a template (Click here to download). The content in the template can be printed, but cannot be edited or extracted (copied ). To verify that this document has such protection, I used Adobe Acrobat 7.0 Professional edition to open it and view the related protection:

300) {this. resized = true; this. width = 300;} "resized =" true ">

300) {this. resized = true; this. width = 300;} ">

It can be seen that this PDF document is indeed encrypted.

2. Send this document as an email attachment to Gmail. You can use the direct view function of Gmail to open the PDF file in HTML format:



3. Open the PDF file in HTML format and find that the file can be copied:

300) {this. resized = true; this. width = 300;} "resized =" true "> that is to say, the copy protection of this PDF file has been completely removed by Gmail. It should be noted that the password-protected PDF file (that is, the password is required to be opened) cannot be opened using Gmail. It is estimated that this is a Gmail bug, because such a "function" is a little too powerful. I believe Google will fix this issue soon.