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https://issues.apache.org/jira/browse/PDFBOX-3544?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15608901#comment-15608901
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Tilman Hausherr commented on PDFBOX-3544:
-----------------------------------------
I didn't test your code change (by your own admission, it doesn't work), I
looked at what we do: we take the offset at "<" and after the ">" and that one
is in /ByteRange. So there has to be an adjustment to get the actual
signatzure. Adobe does the same, see the signed files in PDFBOX-3540. Because
of that we have to add 1. I agree that this is in contradiction with the
document you mention - that one sets the offset after the "<".
You can also find a file signed with itext in PDFBOX-1751, and with Adobe in
PDFBOX-3114.
> Invalid ByteRange for getContents() method
> ------------------------------------------
>
> Key: PDFBOX-3544
> URL: https://issues.apache.org/jira/browse/PDFBOX-3544
> Project: PDFBox
> Issue Type: Bug
> Components: Signing
> Affects Versions: 2.0.3
> Reporter: Lonzak
>
> PDSignature.java class, getContents() method, line 325ff.
> {code:title=PDSignature.java|borderStyle=solid}
> /**
> * Will return the embedded signature between the byterange gap.
> *
> * @param pdfFile The signed pdf file as byte array
> * @return a byte array containing the signature
> * @throws IOException if the pdfFile can't be read
> */
> public byte[] getContents(byte[] pdfFile) throws IOException
> {
> int[] byteRange = getByteRange();
> int begin = byteRange[0]+byteRange[1]+1;
> int end = byteRange[2]-begin;
> return getContents(new COSFilterInputStream(pdfFile,new int[]
> {begin,end}));
> }
> {code:}
> Lets asume a byte range of
> /ByteRange[ 0, 840, 960, 240]
> The current implementation would return
> {841, 119} which is from *841 - 960*
> According to
> [adobe|http://www.adobe.com/content/dam/Adobe/en/devnet/acrobat/pdfs/DigitalSignaturesInPDF.pdf]
> (page 5) this is invalid:
> {quote}
> "In this example, the hash is calculated for bytes 0 through 839, and 960
> through 1200."
> {quote}
> Thus the values for the signature should be
> {840, 119} which is from *840 - 959*
> The implementation should be:
> {code:title=PDSignature.java|borderStyle=solid}
> /**
> * Will return the embedded signature between the byterange gap.
> *
> * @param pdfFile The signed pdf file as byte array
> * @return a byte array containing the signature
> * @throws IOException if the pdfFile can't be read
> */
> public byte[] getContents(byte[] pdfFile) throws IOException
> {
> int[] byteRange = getByteRange();
> int begin = byteRange[0]+byteRange[1];
> int end = byteRange[2]-begin-1;
> return getContents(new COSFilterInputStream(pdfFile,new int[]
> {begin,end}));
> }
> {code:}
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