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https://issues.apache.org/jira/browse/TIKA-4098?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17741557#comment-17741557
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ASF GitHub Bot commented on TIKA-4098:
--------------------------------------
SchwingSK opened a new pull request, #1231:
URL: https://github.com/apache/tika/pull/1231
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> Detection fails on PDF with garbage before header
> -------------------------------------------------
>
> Key: TIKA-4098
> URL: https://issues.apache.org/jira/browse/TIKA-4098
> Project: Tika
> Issue Type: Bug
> Components: core
> Affects Versions: 2.8.0
> Reporter: Thierry Guérin
> Priority: Minor
> Attachments: garbageBeforeHeader.pdf
>
>
> PDF detection fails on files that contain too much garbage before the header
> 'PDF%-'.
> Those PDFs do not respect the specification, but are nonetheless correctly
> handled by PDF viewers.
> The joined PDF is an example on the garbage found in a real-life PDF (looks
> like email headers that 'leaked' onto the PDF file). The PDF itself is one
> that I generated so that the exemple si small.
> The current magic for PDFs limits the search for the '%PDF-%' header to 512
> bytes, and in the joined PDF it's located after 702 garbage bytes.
> I looked at the sources of PdfBox and Ghostscript to see how they handle this
> case and:
> * Ghostscript searches through the entire file (see
> [https://github.com/ArtifexSoftware/ghostpdl/blob/master/pdf/ghostpdf.c]
> lines 1323-1339)
> * PdfBox reads the file line by line, and stops looking for the header when
> it encounters a line that starts with a digit (see
> [https://github.com/apache/pdfbox/blob/trunk/pdfbox/src/main/java/org/apache/pdfbox/pdfparser/COSParser.java]
> lines 1561-)
> From the doc in tika-mimetypes.xml for the application/pdf MIME type, I
> understand that increasing the maximum offset can trigger false positives. I
> increased it to 768, and the unit tests pass, but I didn't find any PDF that
> tests this particular case, so either it doesn't exist or there are
> integration tests that aren't part of this repo ?
> How can I go about testing for regressions ? I can provide a pull request for
> this change, but where do I put the test PDF and a unit test?
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