Adding a signature to an encrypted pdfdocument. 2006-07-12 - By Paulo Soares
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It's a porting bug. In PdfEncryption.cs replace:
public PdfEncryption(PdfEncryption enc) : base() {
with
public PdfEncryption(PdfEncryption enc) : this() {
Paulo
> -- --Original Message-- --
> From: itext-questions-bounces@(protected)
> [mailto:itext-questions-bounces@(protected)] On
> Behalf Of David Saier
> Sent: Wednesday, July 12, 2006 3:03 PM
> To: Post all your questions about iText here
> Subject: Re: [iText-questions] Adding a signature to an
> encrypted pdfdocument.
>
> Hi,
>
> Thanks for the reply, this is the stack trace I get from the
> exception:
> System.NullReferenceException was unhandled
> Message="Object reference not set to an instance of an object."
> Source="iTextSharpSign"
> StackTrace:
> at iTextSharpSign.PDFSigner.Sign(String SigReason, String
> SigContact, String SigLocation, Boolean visible) in
> D:\Documents\PDFcreator\PDFcreator\iTextSharpSign\PDFSigner.cs
> :line 298
> at iTextSharpSign.Form1.button1_Click(Object sender,
> EventArgs e) in
> D:\Documents\PDFcreator\PDFcreator\iTextSharpSign\Form1.cs:line 109
> at System.Windows.Forms.Control.OnClick(EventArgs e)
> at System.Windows.Forms.Button.OnClick(EventArgs e)
> at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
> at System.Windows.Forms.Control.WmMouseUp(Message& m,
> MouseButtons button, Int32 clicks)
> at System.Windows.Forms.Control.WndProc(Message& m)
> at System.Windows.Forms.ButtonBase.WndProc(Message& m)
> at System.Windows.Forms.Button.WndProc(Message& m)
> at
> System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
> at
> System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
> at
> System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr
> hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
> at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
> at
> System.Windows.Forms.Application.ComponentManager.System.Windo
> ws.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessage
> Loop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
> at
> System.Windows.Forms.Application.ThreadContext.RunMessageLoopI
> nner(Int32 reason, ApplicationContext context)
> at
> System.Windows.Forms.Application.ThreadContext.RunMessageLoop(
> Int32 reason, ApplicationContext context)
> at System.Windows.Forms.Application.Run(Form mainForm)
> at iTextSharpSign.Program.Main() in
> D:\Documents\PDFcreator\PDFcreator\iTextSharpSign\Program.cs:line 17
> at System.AppDomain.nExecuteAssembly(Assembly assembly, String[] args)
> at System.AppDomain.ExecuteAssembly(String assemblyFile,
> Evidence assemblySecurity, String[] args)
> at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
> at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
> at System.Threading.ExecutionContext.Run(ExecutionContext
> executionContext, ContextCallback callback, Object state)
> at System.Threading.ThreadHelper.ThreadStart()
>
> I didn't think that this was particularly useful so I found
> the exact line that was causing the exception. The line is in
> the SetHashKey Method in PdfEncryption.cs:
>
> md5.Initialize();
> ...
>
> This can be traced back up to PdfStamper.Close() method.
> I put a break point at this line and got the stack calls at
> that point:
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfEncryption.SetHashKe
> y(int number = 38, int generation = 0) Line 293
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfIndirectObject.PdfIn
> directObject(int number = 38, int generation = 0,
> iTextSharp.text.pdf.PdfObject objecti = {Dictionary of type:
> /XObject}, iTextSharp.text.pdf.PdfWriter writer =
> {iTextSharp.text.pdf.PdfStamperImp}) Line 119 + 0xe bytes
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfIndirectObject.PdfIn
> directObject(int number = 38, iTextSharp.text.pdf.PdfObject
> objecti = {Dictionary of type: /XObject},
> iTextSharp.text.pdf.PdfWriter writer =
> {iTextSharp.text.pdf.PdfStamperImp}) Line 97 + 0x11 bytes
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfWriter.PdfBody.Add(i
> TextSharp.text.pdf.PdfObject objecta = {Dictionary of type:
> /XObject}, int refNumber = 38, bool inObjStm = true) Line 355
> + 0x1c bytes
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfWriter.PdfBody.Add(i
> TextSharp.text.pdf.PdfObject objecta = {Dictionary of type:
> /XObject}, int refNumber = 38) Line 343 + 0xe bytes
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfWriter.PdfBody.Add(i
> TextSharp.text.pdf.PdfObject objecta = {Dictionary of type:
> /XObject}) Line 292 + 0x1b bytes
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfWriter.AddToBody(iTe
> xtSharp.text.pdf.PdfObject objecta = {Dictionary of type:
> /XObject}) Line 1866 + 0xc bytes
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfWriter.Add(iTextShar
> p.text.pdf.PdfImage pdfImage = {Dictionary of type:
> /XObject}, iTextSharp.text.pdf.PdfIndirectReference fixedRef
> = null) Line 991 + 0xa bytes
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfWriter.AddDirectImag
> eSimple(iTextSharp.text.Image image = {Rectangle: 125x35
> (rot: 0 degrees)}, iTextSharp.text.pdf.PdfIndirectReference
> fixedRef = null) Line 967 + 0x11 bytes
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfWriter.AddDirectImag
> eSimple(iTextSharp.text.Image image = {Rectangle: 125x35
> (rot: 0 degrees)}) Line 905 + 0xb bytes
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfContentByte.AddImage
> (iTextSharp.text.Image image = {Rectangle: 125x35 (rot: 0
> degrees)}, float a = 250.0, float b = 0.0, float c = 0.0,
> float d = 75.0, float e = 0.0, float f = 0.0, bool
> inlineImage = false) Line 1211 + 0x10 bytes
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfContentByte.AddImage
> (iTextSharp.text.Image image = {Rectangle: 125x35 (rot: 0
> degrees)}, float a = 250.0, float b = 0.0, float c = 0.0,
> float d = 75.0, float e = 0.0, float f = 0.0) Line 1133 + 0x1d bytes
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfSignatureAppearance.
> GetAppearance() Line 329 + 0x79 bytes
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfSignatureAppearance.
> PreClose(System.Collections.Hashtable exclusionSizes = null)
> Line 732 + 0x11 bytes
>
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfSignatureAppearance.
> PreClose() Line 677 + 0x9 bytes
> iTextSharpSign.exe!iTextSharp.text.pdf.PdfStamper.Close()
> Line 189 + 0xa bytes
> iTextSharpSign.exe!iTextSharpSign.PDFSigner.Sign(string
> SigReason = "", string SigContact = "", string SigLocation =
> "", bool visible = true) Line 294 + 0xa bytes
>
> iTextSharpSign.exe!iTextSharpSign.Form1.button1_Click(object
> sender = {Text = "Sign"}, System.EventArgs e = {X = 33 Y = 14
> Button = Left}) Line 109 + 0x61 bytes
> [External Code]
> iTextSharpSign.exe!iTextSharpSign.Program.Main() Line 17 +
> 0x1a bytes
> [External Code]
>
> Thank you
> David
>
> Paulo Soares <psoares@(protected)> wrote:
>
> What you're tying is possible because PdfReader(string
> file, byte[]
> ownerPassword) will remove the encryption and will
> allow the PDF to be
> signed. I've no idea where the error comes from as you
> don't show any stack
> strace.
>
> Paulo
>
> -- -- Original Message -- --
> From: "David Saier"
> To:
> Sent: Tuesday, July 11, 2006 9:05 PM
> Subject: [iText-questions] Adding a signature to an
> encrypted pdf document.
>
>
> Hello,
>
> I have been trying to use iText to create a signature
> in an encrypted pdf
> document. Basically I have a pdf document which is
> password encrypted with a
> known owner password, and I want to add a signature to
> it. When I try it it
> gives me an "Object reference set to null" error,
> making me believe the
> problem is in accessing the document. I have gotten my
> code to work if the
> pdf is not encrypted, however this is not an option for
> me, I have to have
> the document locked before I add a signature to it.
>
> Using the PdfReader(string file, byte[] ownerPassword)
> constructor for the
> PdfReader I pass into the PdfStamper.CreateSignature
> does not seem to work.
>
> Is what I am trying to do possible?
>
> Thanks,
> David
>
>
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