PdfReader not opened with owner password - c#

I am using iTextSharp version 4.1.6.0 and my code throws the "PdfReader not opened with owner password" exception. The strange thing is that I can open all single PDF files, but on merging them it fails. Following other threads I was trying:
PdfReader.unethicalreading = true;
but this parameter is not accepted and I get:
'PDFReader' does not contain a definition for 'unethicalreading'
Martin

Taking a look at the source of PdfReader here, the static property unethicalreading is available after v5.0.2.
but on merging them it fails
Yes, because copying and merging are operations that require special permissions which require the user/owner password.

Related

Check if file is in use - additional question

I'm trying to find an alternative to using the Restart Manager for checking if a file is locked. I found this accepted answer to the same question. However, the accepted answer contains the following comment that I do not understand: "this solution will not work if the file doesn't have a Write or Read lock on it, i.e. it has been opened (for reading or writing) with FileShare.Read or FileShare.Write access."
I tested this using the following code (ommitted using blocks and Close() for brevity):
static void Main(string[] args)
{
const string fileName = "test.txt";
// This should open the file as described, shouldn't it?
var fi1 = new FileInfo(fileName);
// Test with FileShare.Read / FileShare.Write / FileShare.ReadWrite gives the same result
var fs1 = fi1.Open(FileMode.OpenOrCreate, FileAccess.Write, FileShare.Write);
var fi2 = new FileInfo(fileName);
Console.WriteLine($"Is file locked? {IsFileLocked(fi2)}");
// Displays always: "Is file locked? True"
Console.ReadLine();
}
This displays always "Is file locked? True" whereas it should display "False" according to the comment.
I tested also the code of this answer which has a similar comment with no luck. Tested also with two seperate processes - as expected no difference.
Looking at the docs, my test results seem resonably - but I'm puzzled by the above mentioned comments.
How else would I open a file e.g. for reading without creating a lock?
The part of the answer that you quoted is incorrect. The mechanism that prevents you from opening an already open file is the share mode, not the desired access type.
When you attempt to open a file that is already in use, the share mode requested is compared against the share mode that the file was opened with. If they don't match up, your call fails.
EDIT: Just to cover all of my bases, the above only holds true on Windows. It is possible to open a file without any sort of mutual exclusion on POSIX-based systems. However, .NET was exclusive to Windows at the time of the quoted answer.

PdfReader.unethicalreading = true; not working

We have an interface that allows users to send back copies of the receipts to our customers. The user feeds in up to a five or so PDFs and they all get merged using itextsharp's (v5.5.13.1) PdfReader.
Unfortunately some users somehow password-protect a file or two here and there... I want to avoid the issue of needing to trust the user to supply us with unprotected files.
Relevant code
PdfReader.unethicalreading = true;
PdfReader reader = null;
foreach(string pdf in pdfs)
{
reader = new PdfReader(pdf);//iTextSharp.text.exceptions.BadPasswordException : 'Bad user password'
}
If there are no password-protected files, the merge goes off without a hitch. Otherwise when it comes to the offending file, the above will throw at the line with the thrown exception.
From what I understood unethicalreading was all that was needed. I even tried to assign it immediately before the line that throws but it gives me the same result.
Does this flag work on C# since most of the help I see online for this library is written for Java (normal, I know, but I wonder if this part of the library has been properly ported)?

Visible signature created using iText 7 not shown in chrome

I am using iText 7 to sign pdf documents.
This works without problems, and the signature is shown as valid.
In addition to the digital signature, i want to show a visual representation on the pdf. This is described in the digital signature book chapter 2.4 Creating different signature appearances.
The produced pdf shows this appearance if i open it using adobe reader.
The first image is a pdf created using word and the save as pdf functionality.
The second image is a demo pdf i just downloaded random.
If i open the first pdf in chrome, the signature appearance text is not shown, but if i open the pdf which was initially created using word, the signature apperance is missing.
Any ideas on whats wrong with the pdf which doesn't show the signature appearance in chrome?
edit: Links to the documents
Pdf which shows signature in chrome
https://1drv.ms/b/s!AkROTDoCWFJnkd5VOFjUHZfpQXzJWQ?e=MeyZje
Pdf which doesn't show signature in chrome
https://1drv.ms/b/s!AkROTDoCWFJnkd5W5P3MCbb8fwLASA?e=zsmks0
edit 2: Code sample
The following code sample will sign a pdf document using a local certificate and place some text into the SignatureAppearance which is not shown in chrome.
using iText.Kernel.Geom;
using iText.Kernel.Pdf;
using iText.Signatures;
using System.IO;
using System.Security.Cryptography.X509Certificates;
namespace PdfSigning.Lib.Helpers
{
public class SignPdfTest
{
public static byte[] SingPdfUsingCertificate(X509Certificate2 cert2, byte[] pdfToSign)
{
var apk = Org.BouncyCastle.Security.DotNetUtilities.GetKeyPair(cert2.PrivateKey).Private;
IExternalSignature pks = new PrivateKeySignature(apk, DigestAlgorithms.SHA512);
var cp = new Org.BouncyCastle.X509.X509CertificateParser();
var chain = new[] { cp.ReadCertificate(cert2.RawData) };
using (PdfReader reader = new PdfReader(new MemoryStream(pdfToSign)))
{
using (MemoryStream fout = new MemoryStream())
{
StampingProperties sp = new StampingProperties();
sp.UseAppendMode();
PdfSigner signer = new PdfSigner(reader, fout, sp);
PdfSignatureAppearance appearance = signer.GetSignatureAppearance();
appearance.SetPageNumber(1);
appearance.SetLayer2Text("Hello world");
appearance.SetLayer2FontSize(8);
Rectangle pr = new Rectangle(10, 10, 200, 100);
appearance.SetPageRect(pr);
appearance.SetRenderingMode(PdfSignatureAppearance.RenderingMode.DESCRIPTION);
appearance.SetPageRect(pr);
signer.SignDetached(pks, chain, null, null, null, 0, PdfSigner.CryptoStandard.CMS);
return fout.ToArray();
}
}
}
}
}
private static void SignDocumentUsingCertificateConfiguration()
{
try
{
var certificateSignatureConfiguration = new CertificateSignatureConfiguration();
var cert2 = new X509Certificate2(#"C:\temp\MyCertificate.pfx", "mypassword", X509KeyStorageFlags.Exportable);
CertificatePdfSigner certPdfSigner = new CertificatePdfSigner(certificateSignatureConfiguration);
byte[] signedPdf = PdfSigning.Lib.Helpers.SignPdfTest.SingPdfUsingCertificate(cert2, File.ReadAllBytes(#"C:\temp\WordSaveAsPdf.pdf"));
File.WriteAllBytes(#"C:\temp\WordSaveAsPdf_Signed.pdf", signedPdf);
Console.WriteLine("Done");
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
In short
Chrome appears to not read object streams of hybrid reference PDFs, in particular not in the incremental update added during signature creation.
iText, on the other hand, puts nearly all its changes during signing into an object stream.
Thus, Chrome is not aware of the added signature and its appearance.
One can resolve the situation by forcing iText not to create an object stream here.
What is special about the Word generated source PDF?
PDF files contain object cross reference information which map object numbers to offsets of the respective starts of these objects in the file. These information can be stored in two ways, as cross reference table and (since PDF 1.5) also as cross reference stream. Also since PDF 1.5 the format allows to put non-stream objects into so called object streams which allows superior compression as only stream contents can be compressed.
As most PDF viewers at the time PDF 1.5 has been introduced did not support cross reference and object streams, a mixed, hybrid reference style was also introduced then. In this style the basic objects in a PDF which are strictly necessary to display it, are added normally (not in object streams) and are referenced from cross reference tables. Extra information which is not strictly necessary is then added in object streams and referenced from cross reference streams.
MS Word creates PDFs in this hybrid style and is virtually the only software to do so.
What is special about the iText signed result PDF?
iText put nearly all the changes into an object stream in a new incremental update.
Apparently, though, Chrome does not fully support object and cross reference streams, in particular not if combined with further incremental updates.
Thus, Chrome is not aware of the added signature and its visualization.
How to resolve the problem?
What we need to do, therefore, is convince iText that it shall not add important data in an object stream during signing. Due to member variable visibilities this is not as easy as one would like; I used reflection here for that.
In your code simply use the following PdfSignerNoObjectStream instead of PdfSigner:
public class PdfSignerNoObjectStream : PdfSigner
{
public PdfSignerNoObjectStream(PdfReader reader, Stream outputStream, StampingProperties properties) : base(reader, outputStream, properties)
{
}
protected override PdfDocument InitDocument(PdfReader reader, PdfWriter writer, StampingProperties properties)
{
try
{
return base.InitDocument(reader, writer, properties);
}
finally
{
FieldInfo propertiesField = typeof(PdfWriter).GetField("properties", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
WriterProperties writerProperties = (WriterProperties) propertiesField.GetValue(writer);
writerProperties.SetFullCompressionMode(false);
}
}
}
Beware, though, tweaking iText functionality like this is not guaranteed to work across versions. I tested it for a recent iText-7.1.7-SNAPSHOT development state; I expect it to also work for the previous 7.1.x versions.
Is this a Chrome bug? Or an iText bug? Or what?
Most likely it's kind of both.
On one hand the Chrome PDF viewer appears to have issues with hybrid reference PDFs. Considering how long they have been part of the PDF format, that is somewhat disappointing.
And on the other hand the PDF specification requires in the context of hybrid reference documents:
In general, the objects that may be hidden are optional objects specified by indirect references. [...]
Items that shall be visible include the entire page tree, fonts, font descriptors, and width tables. Objects that may be hidden in a hybrid-reference file include the structure tree, the outline tree, article threads, annotations, destinations, Web Capture information, and page labels.
(ISO 32000-1, section 7.5.8.4 Compatibility with Applications That Do Not Support Compressed Reference Streams)
In the case at hand an (updated) page object is in the object stream, i.e. hidden from viewers not supporting cross reference and object streams.
Currently iText 7 PdfDocument attempts to enforce FullCompression on PdfWriters if the underlying PdfReader has any cross reference stream (HasXrefStm):
writer.properties.isFullCompression = reader.HasXrefStm();
(PdfDocument method Open)
Probably it shouldn't enforce that if the PdfReader also is identified as hybrid reference stream (HasHybridXref).
This might be simply caused by the chrome build-in PDF reader. As far as I understood his case, the person who requested help from Chrome devs in this question has received some answers and was redirected to another part of the forum where he could get help. I can try to recreate the problem with itext-sharp 5 (I used that in a previous project) and see if that signature is not shown in Chrome but the odds won't be good.
This sounds an awful lot like a case of the "Needs Appearances" flag not being set. Back in my day (wheeze) iText form fields were generated with as little graphical data as possible, and would set the \NeedsAppearances flag to true, letting the PDF viewer in question (Acrobat Reader was about it back then) that it needed to generate the form fields' appearances before trying to draw them to screen.
And visible PDF Signatures are held in form fields.
So its at least theoretically possible that you can fix this programmatically by telling iText to (re?)generate the form field appearances.

How to Check PDF is Reader enabled or not using C#?

My only requirement is to find a selected pdf in a folder is Reader enabled or not, more specifically if usage rights are defined in a way that allows people to add annotations (e.g. comments).
I am doing this in windows application. If I click a button, an event is triggered searching a folder for PDF files. This event needs to check whether or not the PDFs in the folder are Reader enabled for comments. If they are, I need to remove the comment usage rights or revert the PDF back to its original version.
My code can only find PDF files in the folder. I don`t know how to check if the selected PDF is comment enabled or not. Please be gentle and suggest solution.
Here's my code:
private void button1_Click(object sender, EventArgs e)
{
{
string[] filePaths = Directory.GetFiles("D:\\myfolder\\pdffolder");
List<ListViewItem> files = new List<ListViewItem>();
foreach (string filePath in filePaths)
{
---need to check comment enabled or not---
}
}
}
You want to know if a PDF is Reader enabled or not. Reader enabling is established by adding a digital signature known as a Usage Rights (UR) signature. If you have an instance of PdfReader, you can check whether or not a PDF is Reader enabled by using the hasUsageRights() method:
PdfReader reader = new PdfReader(path_to_file);
boolean isReaderEnabled = reader.hasUsageRights();
Usage rights can encompass many different things, such as allowing people to comment, allowing people to save a filled out form, allowing people to sign a document,...
To find out which rights are enabled, you have to inspect either the UR or the UR3 dictionary (note that UR is deprecated, but there may still be PDFs out there that have a UR dictionary):
PdfDictionary catalog = reader.getCatalog();
PdfDictionary perms = catalog.getAsDict(PdfName.PERMS);
PdfDictionary ur = null;
if (perms != null) {
PdfDictionary ur = perms.getAsDict(PdfName.UR);
if (ur == null)
ur = perms.getAsDict(PdfName.UR3);
}
}
If ur remains null, there are no usage rights. If you only want to check if commenting is enabled, you'll have to inspect the entries of the ur dictionary. There will be an /Annots entry with as value an array with values such as Create, Delete, Modify, Copy, Import, Export, Online and SummaryView. FOr the full overview of possible entries, see Table 255 "Entries in the UR transform parameters dictionary" of ISO-32000-1.
You can remove all usage rights like this:
PdfReader reader = new PdfReader(path_to_file);
if (reader.hasUsageRights()) {
reader.removeUsageRights();
PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(path_to_new_file));
stamper.close();
}
It is impossible to remove only the usage rights for commenting while preserving other usage rights (if present). Just removing the /Annots entry from the /UR or /UR3 dictionary will break the digital signature that enables usage rights. This digital signature is created with a private key owned by Adobe and no third party tool (other than an Adobe product) is allowed to use that key.
Final note:
all code snippet were written in Java, but iTextSharp has corresponding methods or properties in C#. It shouldn't be a problem to port the snippets to C#.
In many cases, it's sufficient to change a lower case into an upper case:
Java: object.add(something);
C#: object.Add(something);
Or you have to remove the set/get:
Java: object.setSomething(something);
C#: object.Something = something;
Thanks for all who takes effect to my question. I finally found the answer in a similar way by reading the PDF and check for a particular string (particular string presented if Comment enabled on the PDF).
The particular string starts with /Annot ....., First I read the PDF thru System.IO, then store in a string and looking for the particular string, If the searching string available then the PDF is comment enabled else not.

Can I fill in an encrypted PDF with iTextSharp?

I have a fillable, saveable PDF file that has an owner password (that I don't have access to). I can fill it out in Adobe reader, export the FDF file, modify the FDF file, and then import it.
Then I tried to do it with iText for .NET. I can't create a PdfStamper from my PdfReader because I didn't provide the owner password to the reader. Is there any way to do this programmatically or must I recreate the document?
Even using FdfReader requires a PdfStamper. Am I missing anything? Anything legal that is - I'm pretty sure I could hack the document, but I can't. Ironically, recreating it would probably be ok.
This line will bypass edit password checking in iTextSharp:
PdfReader.unethicalreading = true;
[I found this question several months after it was posted and I'm posting this solution now for anyone who comes across this question in a search.]
I was in the exact same situation: my customer had a PDF with fillable fields that I needed to programmatically access. Unfortunately the PDF was password protected and they didn't have the password so I found couldn't work with their file.
What I discovered was that iTextSharp version 4.0.4 (and later) enforces password restrictions, earlier versions did not.
So I downloaded version 4.0.3 and sure enough it worked. In my case I didn't even have to change my code to use this older version.
You can download 4.0.3 (and all other versions) at SourceForge.
Two important things
Set PdfReader.unethicalreading = true to prevent BadPasswordException.
Set append mode in PdfStamper's constructor, otherwise the Adobe Reader Extensions signature becomes broken and Adobe Reader will display following message: "This document contained certain rights to enable special features in Adobe Reader. The document has been changed since it was created and these rights are no longer valid. Please contact the author for the original version of this document."
So all you need to do is this:
PdfReader.unethicalreading = true;
using (var pdfReader = new PdfReader("form.pdf"))
{
using (var outputStream = new FileStream("filled.pdf", FileMode.Create, FileAccess.Write))
{
using (var stamper = new iTextSharp.text.pdf.PdfStamper(pdfReader, outputStream, '\0', true))
{
stamper.AcroFields.Xfa.FillXfaForm("data.xml");
}
}
}
See How to fill XFA form using iText?
Unless someone else chimes in, I'll assume the answer is "No"
I wound up regenerating the PDF in an unencrypted form.

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