I have been given the challenge to open PDF files with a custom security handler. I have no control over the PDF files or how the security is added to them. The goal is to use a remote server already in place, to retrieve the password for the file. Now here is the catch: the validity is checked using unique data embedded as XML in the custom security handler itself. And indeed, I can see that data when I open the encoded PDF file in a hex editor (it will not open in any other program I tried, including CosEdit).
After some searching I opted for PDFTron for this task and have added the library to my C++ project. I studied the samples and found EncTest, which appeared to be a good start. So I added the class MySecurityHandler to my project.
Then I added this code to main function itself:
PDFNet::RegisterSecurityHandler(“NewSecurityHandler”, “NewSecurityHandler”, MySecurityHandler::Create);
// The rest is just testing to see if I can actually do something
doc.InitSecurityHandler(); // Success: the code I added to MySecurityHandler launches correctly
int c = doc.GetPageCount(); // Success: c = 39
std::string name = doc.GetTrailer().Get(“Encrypt”).Value().Get(“Filter”).Value().GetName(); // Success: name = “NewSecurityHandler”
That appears to be alright so far. Now my problem is that I have no idea how to reach the XML embedded in the custom security handler, so that I can extract the data that I need to make the API call. Is that even possible, and if so how should I go about that?
I don’t mind a challenge, but could really use some help at this point. Please let me know what other information might be needed to answer my question.