[Poppler-bugs] [Bug 48679] New: "Error: Invalid XRef entry" messages for a valid PDF

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=48679

             Bug #: 48679
           Summary: "Error: Invalid XRef entry" messages for a valid PDF
    Classification: Unclassified
           Product: poppler
           Version: unspecified
          Platform: Other
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: general
        AssignedTo: poppler-bugs at lists.freedesktop.org
        ReportedBy: Thomas.Freitag at alfa.de


Created attachment 59961
  --> https://bugs.freedesktop.org/attachment.cgi?id=59961
Patch to suppress wrong "Error: Invalid XRef entry" messages

I have a valid PDF, where I get several "Error: Invalid XRef entry" messages
when I call i.e. pdftoppm. The PDF is too huge to attach it to this bug report,
so I try to describe the problem:
The PDF has an object with a big string:
56 0 obj <</CharSet
(þÿ^@\(^@/^@S^@/^@t^@/^@r^@/^@a^@/egmrnabdsl^@/^@e^@/^@n^@/^@b^@/^@u^@/psca^@e^@/yhhpne^@/^@T^@/^@i^@/^@f^@/^@c^@/^@h^@/^@o^@/^@w^@/^@k^@/^@N^@/^@s^@/^@C^@/^@l^@/^@D^@/inen^@/^@A^@/no^@e^@/hter^@e^@/ifev^@/^@x^@/wt^@o^@/^@m^@/ezor^@/ofru^@/^@E^@/epirdo^@/^@d^@/^@G^@/^@H^@/maepsrna^@d^@/^@K^@/dueieris^@s^@/^@g^@\))
/CapHeight 500 /Ascent 728 /Flags 32 /FontFile 58 0 R /ItalicAngle 0 /Descent
-210 /XHeight 250 /FontName /ZJIGIZ+ArialMT,Bold /Leading 150 /FontBBox [-628
-376 2000 1010 ] /MaxWidth 2628 /AvgWidth 479 /Type /FontDescriptor /StemV 0 >>
endobj
Parsing this string in Lexer::getObj it exceeds the token buffer size (128
bytes), therefore xref->getNumEntry(curStr.streamGetPos()) is called to check
if the document is not malformed and we are growing too much.
XRef::getNumEntry walks over every xref entry to get the obj num for the actual
stream position, so it calls also XRef::getEntry with parameter 2. But in this
PDF the obj num's from 2 to 4 are not used:
xref
0 2
0000000002 65535 f
0000000015 00000 n
5 145
0000000236 00000 n
:  :  :
But therefore XRef::getEntry i.e. with parameter 2 rescans the xref section,
encounters that obj num is not used and give the error message.
Because getNumEntry is called only to check for malformed documents and returns
the obj num for a given stream position, it shouldn't check for xrefEntryNone
entries. The attached patch solves this.

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