octoleo
/
qpdf
mirror of https://github.com/qpdf/qpdf.git
2
1
Fork 0
Code Issues Releases Wiki Activity

Improve stream length recovery 

Eliminate PCRE and find endobj not preceded by endstream. Be more lax
about placement of endstream and endobj.
This commit is contained in:
Jay Berkenbilt 2017-08-09 21:14:48 -04:00
parent 3082e4e606
commit ca5b1d267a
5 changed files with 87 additions and 68 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
ChangeLog
View File

@ -11,6 +11,12 @@
the (bool, T*) version of the constructor instead. If not, just
remove the second parameter.
2017-08-09 Jay Berkenbilt <ejb@ql.org>
* When recovering stream length, find endobj without endstream as
well as just looking for endstream. Be a little more lax about
where we allow it to be found.
2017-08-05 Jay Berkenbilt <ejb@ql.org>
* Add --single-pages option to cause output to be written to a

1
include/qpdf/QPDF.hh
View File

@ -1030,6 +1030,7 @@ class QPDF
// Methods to support pattern finding
bool findHeader();
bool findStartxref();
bool findEndstream();
// methods to support linearization checking -- implemented in
// QPDF_linearization.cc

81
libqpdf/QPDF.cc
View File

@ -1231,76 +1231,43 @@ QPDF::readObject(PointerHolder<InputSource> input,
return object;
}
bool
QPDF::findEndstream()
{
// Find endstream or endobj. Position the input at that token.
QPDFTokenizer::Token t = readToken(this->file, true);
if ((t.getType() == QPDFTokenizer::tt_word) &&
((t.getValue() == "endobj") ||
(t.getValue() == "endstream")));
{
this->file->seek(this->file->getLastOffset(), SEEK_SET);
return true;
}
return false;
}
size_t
QPDF::recoverStreamLength(PointerHolder<InputSource> input,
int objid, int generation,
qpdf_offset_t stream_offset)
{
PCRE endobj_re("^\\s*endobj\\b");
// Try to reconstruct stream length by looking for
// endstream(\r\n?|\n)endobj
// endstream or endobj
warn(QPDFExc(qpdf_e_damaged_pdf, input->getName(),
this->last_object_description, stream_offset,
"attempting to recover stream length"));
input->seek(0, SEEK_END);
qpdf_offset_t eof = input->tell();
input->seek(stream_offset, SEEK_SET);
qpdf_offset_t last_line_offset = 0;
PatternFinder ef(*this, &QPDF::findEndstream);
size_t length = 0;
static int const line_end_length = 12; // room for endstream\r\n\0
char last_line_end[line_end_length];
while (input->tell() < eof)
if (this->file->findFirst("end", stream_offset, 0, ef))
{
std::string line = input->readLine(50);
qpdf_offset_t line_offset = input->getLastOffset();
if (endobj_re.match(line.c_str()))
length = this->file->tell() - stream_offset;
// Reread endstream but, if it was endobj, don't skip that.
QPDFTokenizer::Token t = readToken(this->file);
if (t.getValue() == "endobj")
{
qpdf_offset_t endstream_offset = 0;
if (last_line_offset >= line_end_length)
{
qpdf_offset_t cur_offset = input->tell();
// Read from the end of the last line, guaranteeing
// null termination
qpdf_offset_t search_offset =
line_offset - (line_end_length - 1);
input->seek(search_offset, SEEK_SET);
memset(last_line_end, '\0', line_end_length);
input->read(last_line_end, line_end_length - 1);
input->seek(cur_offset, SEEK_SET);
// if endstream[\r\n] will fit in last_line_end, the
// 'e' has to be in one of the first three spots.
// Check explicitly rather than using strstr directly
// in case there are nulls right before endstream.
char* p = ((last_line_end[0] == 'e') ? last_line_end :
(last_line_end[1] == 'e') ? last_line_end + 1 :
(last_line_end[2] == 'e') ? last_line_end + 2 :
0);
char* endstream_p = 0;
if (p)
{
char* p1 = strstr(p, "endstream\n");
char* p2 = strstr(p, "endstream\r");
endstream_p = (p1 ? p1 : p2);
}
if (endstream_p)
{
endstream_offset =
search_offset + (endstream_p - last_line_end);
}
}
if (endstream_offset > 0)
{
// Stream probably ends right before "endstream"
length = endstream_offset - stream_offset;
// Go back to where we would have been if we had just
// read the endstream.
input->seek(line_offset, SEEK_SET);
break;
}
}
last_line_offset = line_offset;
this->file->seek(this->file->getLastOffset(), SEEK_SET);
}
}
if (length)

27
qpdf/qtest/qpdf/bad24-recover.out
View File

@ -1,10 +1,25 @@
WARNING: bad24.pdf (object 4 0, file position 385): expected endstream
WARNING: bad24.pdf (object 4 0, file position 341): attempting to recover stream length
WARNING: bad24.pdf (object 4 0, file position 341): unable to recover stream data; treating stream as empty
WARNING: bad24.pdf (object 4 0, file position 778): EOF while reading token
/QTest is implicit
/QTest is indirect and has type null (2)
/QTest is null
WARNING: bad24.pdf (object 4 0, file position 341): recovered stream length: 54
/QTest is indirect and has type stream (10)
/QTest is a stream. Dictionary: << /Length 44 >>
Raw stream data:
BT
/F1 24 Tf
72 720 Td
(Potato) Tj
ET
enxstream
Uncompressed stream data:
BT
/F1 24 Tf
72 720 Td
(Potato) Tj
ET
enxstream
End of stream data
unparse: 4 0 R
unparseResolved: null
unparseResolved: 4 0 R
test 1 done

40
qpdf/qtest/qpdf/issue-101.out
View File

@ -5,10 +5,16 @@ WARNING: issue-101.pdf (file position 1242): expected dictionary key but found n
WARNING: issue-101.pdf (file position 1242): dictionary ended prematurely; using null as value for last key
WARNING: issue-101.pdf (object 5 0, file position 1438): /Length key in stream dictionary is not an integer
WARNING: issue-101.pdf (object 5 0, file position 1509): attempting to recover stream length
WARNING: issue-101.pdf (object 5 0, file position 1509): recovered stream length: 205
WARNING: issue-101.pdf (object 5 0, file position 1509): recovered stream length: 8
WARNING: issue-101.pdf (trailer, file position 1631): /Length key in stream dictionary is not an integer
WARNING: issue-101.pdf (trailer, file position 1702): attempting to recover stream length
WARNING: issue-101.pdf (trailer, file position 1702): recovered stream length: 12
WARNING: issue-101.pdf (trailer, file position 2026): /Length key in stream dictionary is not an integer
WARNING: issue-101.pdf (trailer, file position 2097): attempting to recover stream length
WARNING: issue-101.pdf (trailer, file position 2097): recovered stream length: 709
WARNING: issue-101.pdf (trailer, file position 2097): recovered stream length: 12
WARNING: issue-101.pdf (trailer, file position 2613): /Length key in stream dictionary is not an integer
WARNING: issue-101.pdf (trailer, file position 2684): attempting to recover stream length
WARNING: issue-101.pdf (trailer, file position 2684): recovered stream length: 74
WARNING: issue-101.pdf (trailer, file position 2928): unknown token while reading object; treating as string
WARNING: issue-101.pdf (trailer, file position 2929): unknown token while reading object; treating as string
WARNING: issue-101.pdf (trailer, file position 2928): expected dictionary key but found non-name object; inserting key /QPDFFake1
@ -22,8 +28,32 @@ WARNING: issue-101.pdf (trailer, file position 3410): attempting to recover stre
WARNING: issue-101.pdf (trailer, file position 3410): recovered stream length: 12
WARNING: issue-101.pdf (trailer, file position 3560): /Length key in stream dictionary is not an integer
WARNING: issue-101.pdf (trailer, file position 3631): attempting to recover stream length
WARNING: issue-101.pdf (trailer, file position 3631): recovered stream length: 167
WARNING: issue-101.pdf (trailer, file position 3631): recovered stream length: 8
WARNING: issue-101.pdf (trailer, file position 4113): /Length key in stream dictionary is not an integer
WARNING: issue-101.pdf (trailer, file position 4184): attempting to recover stream length
WARNING: issue-101.pdf (trailer, file position 4184): unable to recover stream data; treating stream as empty
issue-101.pdf: unable to find trailer dictionary while recovering damaged file
WARNING: issue-101.pdf (trailer, file position 4184): recovered stream length: 8
WARNING: issue-101.pdf (file position 591): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 625): treating unexpected brace token as null
WARNING: issue-101.pdf (file position 626): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 637): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 639): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 644): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 647): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 687): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 691): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 696): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 698): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 701): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 711): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 742): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 745): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 747): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 777): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 790): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 800): treating unexpected brace token as null
WARNING: issue-101.pdf (file position 801): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 811): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 819): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 832): unknown token while reading object; treating as string
WARNING: issue-101.pdf (file position 856): unexpected >
issue-101.pdf (file position 856): unable to find /Root dictionary