[iText-questions] SigDict /Contents illegal data in signed pdf file

[Tamas Nemeth]

Hi,

I have created a simple pdf signer application in iText.
I wanted to add external pkcs7 signature to a pdf file. First I
created a hash from pdf data, then I created a pkcs7 signature or
timestamp file with this hash, after that I added the created hash to
the pdf file.
After that, when I wanted to open the pdf file with Adobe acrobat 7,
then I always get "Signature contains incorrect, unrecognized, corrupt
or  suspicious data. Support Information: SigDict /Contents illegal
data." When the signature is invalid (wrong hash), then I get
different error.
The same happens when I copies a pkcs7 data from a signed pdf with
valid signature.
Below you can see my code, maybe someone can spot the bug.
Unfortunatelly I could not find! :(

First function makes the hash and second function makes the signature.
I have attached my output pdf file.

    public static void hash_pdf (String pdfname) throws Exception
    {

        PdfReader reader = new PdfReader(pdfname);

        PdfStamper stp = PdfStamper.createSignature(reader, null,
'\0', new File ("d:\\temp\\"));
        PdfSignatureAppearance sap = stp.getSignatureAppearance();
        // comment next line to have an invisible signature
        sap.setVisibleSignature(new Rectangle(100, 100, 200, 200), 1, null);
        sap.setLayer2Text("Alairas.");
        PdfDictionary dic = new PdfDictionary();
        dic.put(PdfName.FT, PdfName.SIG);
        //dic.put(PdfName.FILTER, new PdfName("Adobe.PPKMS"));
        dic.put(PdfName.FILTER, new PdfName("Adobe.PPKLite"));
        dic.put(PdfName.SUBFILTER, new PdfName("adbe.pkcs7.detached"));
        sap.setCryptoDictionary(dic);
        HashMap exc = new HashMap();
        exc.put(PdfName.CONTENTS, new Integer(0x3502));
        sap.preClose(exc);

        MessageDigest messageDigest = MessageDigest.getInstance("SHA1");
        byte buf[] = new byte[8192];
        int n;

        InputStream inp = sap.getRangeStream();

        while ((n = inp.read(buf)) > 0) {
            messageDigest.update(buf, 0, n);
        }

        byte hash[] = messageDigest.digest();

        String outhash = convertToHexString (hash);

        System.out.println(outhash);

    }

    public static void create_pdf (String pdfname, String
pkcs7signature, String outputfilename) throws Exception
    {


        PdfReader reader = new PdfReader(pdfname);
        FileOutputStream fout = new FileOutputStream(outputfilename);
        PdfStamper stp = PdfStamper.createSignature(reader, fout,
'\0',new File ("d:\\temp\\"));
        PdfSignatureAppearance sap = stp.getSignatureAppearance();
        // comment next line to have an invisible signature
        sap.setVisibleSignature(new Rectangle(100, 100, 200, 200), 1, null);
        sap.setLayer2Text("Alairas.");
        PdfDictionary dic = new PdfDictionary();
        dic.put(PdfName.FT, PdfName.SIG);
        //dic.put(PdfName.FILTER, new PdfName("Adobe.PPKMS"));
        dic.put(PdfName.FILTER, new PdfName("Adobe.PPKLite"));
        dic.put(PdfName.SUBFILTER, new PdfName("adbe.pkcs7.detached"));
        sap.setCryptoDictionary(dic);
        HashMap exc = new HashMap();
        exc.put(PdfName.CONTENTS, new Integer(0x3502));
        //exc.put(PdfName.M, new Integer(0x19));
        //exc.put(PdfName.NAME, new Integer(0x1f));
        sap.preClose(exc);


        PdfDictionary dic2 = new PdfDictionary();

        byte[] pdfsignature = convertHexString (pkcs7signature);

        dic2.put(PdfName.CONTENTS, new
PdfString(pdfsignature).setHexWriting(true));
        sap.close(dic2);
    }


Thanks your help in advance!
Best regards!
Tamas

hello-timestamped.pdf
Description: Adobe PDF document