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Posted to dev@pdfbox.apache.org by "Diego Rodrigues Azevedo (JIRA)" <ji...@apache.org> on 2016/02/11 19:21:19 UTC
[jira] [Updated] (PDFBOX-3230) Can't cast CosObject to CosStream
when it is a Stream
[ https://issues.apache.org/jira/browse/PDFBOX-3230?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Diego Rodrigues Azevedo updated PDFBOX-3230:
--------------------------------------------
Attachment: TestFile-assinado.pdf
This is a signed PDF, with a DSS dictionary and DocumentTimeStamp to protect the DSS.
> Can't cast CosObject to CosStream when it is a Stream
> -----------------------------------------------------
>
> Key: PDFBOX-3230
> URL: https://issues.apache.org/jira/browse/PDFBOX-3230
> Project: PDFBox
> Issue Type: Bug
> Affects Versions: 2.0.0
> Environment: Windows 8.1, Java 8 u60, maven 3.2.2, PDFBOX 2.0.0-RC3
> Reporter: Diego Rodrigues Azevedo
> Attachments: TestFile-assinado.pdf
>
>
> Problem:
> When using digital signatures, one can add a DSS dictionary, referencing Certificates, CRLs, OCSPs... saved as Streams (CosStream) in the PDF.
> So, I signed my PDF with a DSS dictionary, and I want to re-sign it, checking if any one of the streams is already there (same certificate chain, maybe same CRLs (if the first signature wasn't made long ago)...)
> How do I do this? I get the latest DSS dictionary and iterate over the COSArray, knowing the elements must be CosStreams. But then I get a ClassCastException, saying CosObject cannot be cast to CosStream. When I check that CosObject in notepad, I can check it is a CosStream
> Code (proof of concept):
> <code>
> private COSStream createStramIfNotExists(byte[] stream, String dssEntry)
> throws IOException {
> COSArray things = (COSArray) this.dictionary
> .getDictionaryObject(dssEntry);
>
> ByteArrayOutputStream out = null;
> for (COSBase thing : things) {
> InputStream input = null;
> byte[] aux = null;
> try {
> System.out.println(thing);
> out = new ByteArrayOutputStream();
> input = ((COSStream) thing.getCOSObject()).createInputStream();
> IOUtils.copy(input, out);
> aux = out.toByteArray();
> } catch (IOException e) {
> e.printStackTrace();
> } finally {
> IOUtils.closeQuietly(input);
> IOUtils.closeQuietly(out);
> }
> if (Arrays.areEqual(stream, aux)) {
> return (COSStream) thing;
> }
> }
> COSStream cosStream = new COSStream();
> OutputStream out1 = cosStream.createOutputStream();
> out1.write(stream);
> out1.close();
>
> return cosStream;
> }
> </code>
> That sysout prints "COSObject{170, 0}" in the PDF attached when my DSS entry is "Certs", and throws the exception on line "input = ((COSStream) thing.getCOSObject()).createInputStream();"
> But if you open the PDF on notepad++ or similar, you'll see that object 170 (170 0 obj) is a stream.
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