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Read xref table without PCRE
Also accept more errors than before.
This commit is contained in:
Jay Berkenbilt
parent
98a843c2a2
commit
30f109e244
@ -1,5 +1,8 @@
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2017-08-10 Jay Berkenbilt <ejb@ql.org>
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* Be more forgiving of certain types of errors in the xref table
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that don't interfere with interpreting the table.
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* Remove unused "tracing" parameter from PointerHolder's
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(T*, bool) constructor. This change breaks source code
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compatibility, but since this argument to PointerHolder has not
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@ -652,6 +652,10 @@ class QPDF
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void setTrailer(QPDFObjectHandle obj);
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void read_xref(qpdf_offset_t offset);
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void reconstruct_xref(QPDFExc& e);
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bool parse_xrefFirst(std::string const& line,
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int& obj, int& num, int& bytes);
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bool parse_xrefEntry(std::string const& line,
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qpdf_offset_t& f1, int& f2, char& type);
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qpdf_offset_t read_xrefTable(qpdf_offset_t offset);
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qpdf_offset_t read_xrefStream(qpdf_offset_t offset);
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qpdf_offset_t processXRefStream(
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180
libqpdf/QPDF.cc
180
libqpdf/QPDF.cc
@ -9,7 +9,6 @@
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#include <qpdf/QTC.hh>
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#include <qpdf/QUtil.hh>
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#include <qpdf/PCRE.hh>
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#include <qpdf/Pipeline.hh>
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#include <qpdf/Pl_Discard.hh>
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#include <qpdf/FileInputSource.hh>
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@ -537,12 +536,162 @@ QPDF::read_xref(qpdf_offset_t xref_offset)
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this->deleted_objects.clear();
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}
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bool
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QPDF::parse_xrefFirst(std::string const& line,
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int& obj, int& num, int& bytes)
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{
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// is_space and is_digit both return false on '\0', so this will
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// not overrun the null-terminated buffer.
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char const* p = line.c_str();
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char const* start = line.c_str();
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// Skip zero or more spaces
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while (QUtil::is_space(*p))
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{
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++p;
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}
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// Require digit
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if (! QUtil::is_digit(*p))
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{
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return false;
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}
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// Gather digits
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std::string obj_str;
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while (QUtil::is_digit(*p))
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{
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obj_str.append(1, *p++);
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}
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// Require space
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if (! QUtil::is_space(*p))
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{
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return false;
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}
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// Skip spaces
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while (QUtil::is_space(*p))
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{
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++p;
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}
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// Require digit
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if (! QUtil::is_digit(*p))
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{
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return false;
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}
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// Gather digits
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std::string num_str;
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while (QUtil::is_digit(*p))
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{
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num_str.append(1, *p++);
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}
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// Skip any space including line terminators
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while (QUtil::is_space(*p))
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{
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++p;
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}
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bytes = p - start;
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obj = atoi(obj_str.c_str());
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num = atoi(num_str.c_str());
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return true;
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}
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bool
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QPDF::parse_xrefEntry(std::string const& line,
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qpdf_offset_t& f1, int& f2, char& type)
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{
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// is_space and is_digit both return false on '\0', so this will
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// not overrun the null-terminated buffer.
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char const* p = line.c_str();
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// Skip zero or more spaces. There aren't supposed to be any.
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bool invalid = false;
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while (QUtil::is_space(*p))
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{
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++p;
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QTC::TC("qpdf", "QPDF ignore first space in xref entry");
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invalid = true;
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}
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// Require digit
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if (! QUtil::is_digit(*p))
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{
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return false;
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}
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// Gather digits
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std::string f1_str;
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while (QUtil::is_digit(*p))
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{
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f1_str.append(1, *p++);
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}
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// Require space
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if (! QUtil::is_space(*p))
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{
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return false;
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}
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if (QUtil::is_space(*(p+1)))
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{
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QTC::TC("qpdf", "QPDF ignore first extra space in xref entry");
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invalid = true;
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}
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// Skip spaces
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while (QUtil::is_space(*p))
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{
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++p;
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}
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// Require digit
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if (! QUtil::is_digit(*p))
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{
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return false;
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}
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// Gather digits
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std::string f2_str;
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while (QUtil::is_digit(*p))
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{
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f2_str.append(1, *p++);
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}
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// Require space
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if (! QUtil::is_space(*p))
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{
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return false;
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}
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if (QUtil::is_space(*(p+1)))
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{
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QTC::TC("qpdf", "QPDF ignore second extra space in xref entry");
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invalid = true;
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}
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// Skip spaces
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while (QUtil::is_space(*p))
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{
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++p;
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}
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if ((*p == 'f') || (*p == 'n'))
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{
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type = *p;
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}
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else
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{
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return false;
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}
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if ((f1_str.length() != 10) || (f2_str.length() != 5))
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{
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QTC::TC("qpdf", "QPDF ignore length error xref entry");
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invalid = true;
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}
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if (invalid)
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{
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warn(QPDFExc(qpdf_e_damaged_pdf, this->file->getName(),
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"xref table",
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this->file->getLastOffset(),
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"accepting invalid xref table entry"));
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}
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f1 = QUtil::string_to_ll(f1_str.c_str());
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f2 = atoi(f2_str.c_str());
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return true;
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}
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qpdf_offset_t
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QPDF::read_xrefTable(qpdf_offset_t xref_offset)
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{
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PCRE xref_first_re("^\\s*(\\d+)\\s+(\\d+)\\s*");
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PCRE xref_entry_re("(?s:(^\\d{10}) (\\d{5}) ([fn])\\s*$)");
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std::vector<QPDFObjGen> deleted_items;
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this->file->seek(xref_offset, SEEK_SET);
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@ -553,18 +702,17 @@ QPDF::read_xrefTable(qpdf_offset_t xref_offset)
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memset(linebuf, 0, sizeof(linebuf));
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this->file->read(linebuf, sizeof(linebuf) - 1);
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std::string line = linebuf;
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PCRE::Match m1 = xref_first_re.match(line.c_str());
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if (! m1)
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int obj = 0;
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int num = 0;
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int bytes = 0;
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if (! parse_xrefFirst(line, obj, num, bytes))
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{
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QTC::TC("qpdf", "QPDF invalid xref");
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throw QPDFExc(qpdf_e_damaged_pdf, this->file->getName(),
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"xref table", this->file->getLastOffset(),
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"xref syntax invalid");
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}
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file->seek(this->file->getLastOffset() + m1.getMatch(0).length(),
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SEEK_SET);
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int obj = atoi(m1.getMatch(1).c_str());
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int num = atoi(m1.getMatch(2).c_str());
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this->file->seek(this->file->getLastOffset() + bytes, SEEK_SET);
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for (int i = obj; i < obj + num; ++i)
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{
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if (i == 0)
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@ -573,8 +721,11 @@ QPDF::read_xrefTable(qpdf_offset_t xref_offset)
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this->first_xref_item_offset = this->file->tell();
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}
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std::string xref_entry = this->file->readLine(30);
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PCRE::Match m2 = xref_entry_re.match(xref_entry.c_str());
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if (! m2)
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// For xref_table, these will always be small enough to be ints
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qpdf_offset_t f1 = 0;
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int f2 = 0;
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char type = '\0';
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if (! parse_xrefEntry(xref_entry, f1, f2, type))
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{
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QTC::TC("qpdf", "QPDF invalid xref entry");
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throw QPDFExc(
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@ -583,11 +734,6 @@ QPDF::read_xrefTable(qpdf_offset_t xref_offset)
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"invalid xref entry (obj=" +
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QUtil::int_to_string(i) + ")");
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}
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// For xref_table, these will always be small enough to be ints
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qpdf_offset_t f1 = QUtil::string_to_ll(m2.getMatch(1).c_str());
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int f2 = atoi(m2.getMatch(2).c_str());
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char type = m2.getMatch(3).at(0);
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if (type == 'f')
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{
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// Save deleted items until after we've checked the
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@ -289,3 +289,7 @@ qpdf single-pages %d 0
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qpdf single-pages .pdf 0
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qpdf single-pages other 0
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QPDFTokenizer allowing bad token 0
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QPDF ignore first space in xref entry 0
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QPDF ignore first extra space in xref entry 0
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QPDF ignore second extra space in xref entry 0
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QPDF ignore length error xref entry 0
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@ -232,7 +232,7 @@ foreach my $d (@bug_tests)
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show_ntests();
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# ----------
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$td->notify("--- Miscellaneous Tests ---");
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$n_tests += 86;
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$n_tests += 87;
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$td->runtest("qpdf version",
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{$td->COMMAND => "qpdf --version"},
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@ -669,6 +669,13 @@ $td->runtest("ignore bad token",
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$td->EXIT_STATUS => 0},
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$td->NORMALIZE_NEWLINES);
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$td->runtest("recoverable xref errors",
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{$td->COMMAND =>
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"qpdf --check --show-xref xref-errors.pdf"},
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{$td->FILE => "xref-errors.out",
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$td->EXIT_STATUS => 3},
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$td->NORMALIZE_NEWLINES);
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show_ntests();
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# ----------
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$td->notify("--- Single Page ---");
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15
qpdf/qtest/qpdf/xref-errors.out
Normal file
15
qpdf/qtest/qpdf/xref-errors.out
Normal file
@ -0,0 +1,15 @@
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WARNING: xref-errors.pdf (xref table, file position 585): accepting invalid xref table entry
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WARNING: xref-errors.pdf (xref table, file position 606): accepting invalid xref table entry
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WARNING: xref-errors.pdf (xref table, file position 627): accepting invalid xref table entry
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WARNING: xref-errors.pdf (xref table, file position 648): accepting invalid xref table entry
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WARNING: xref-errors.pdf (xref table, file position 667): accepting invalid xref table entry
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checking xref-errors.pdf
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PDF Version: 1.3
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File is not encrypted
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File is not linearized
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1/0: uncompressed; offset = 9
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2/0: uncompressed; offset = 63
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3/0: uncompressed; offset = 135
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4/0: uncompressed; offset = 307
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5/0: uncompressed; offset = 403
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6/0: uncompressed; offset = 438
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79
qpdf/qtest/qpdf/xref-errors.pdf
Normal file
79
qpdf/qtest/qpdf/xref-errors.pdf
Normal file
@ -0,0 +1,79 @@
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%PDF-1.3
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1 0 obj
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<<
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/Type /Catalog
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/Pages 2 0 R
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>>
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endobj
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2 0 obj
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<<
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/Type /Pages
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/Kids [
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3 0 R
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]
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/Count 1
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>>
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endobj
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3 0 obj
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<<
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/Type /Page
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/Parent 2 0 R
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/MediaBox [0 0 612 792]
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/Contents 4 0 R
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/Resources <<
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/ProcSet 5 0 R
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/Font <<
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/F1 6 0 R
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>>
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>>
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>>
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endobj
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4 0 obj
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<<
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/Length 44
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>>
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stream
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BT
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/F1 24 Tf
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72 720 Td
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(Potato) Tj
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ET
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endstream
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endobj
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5 0 obj
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[
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/PDF
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/Text
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]
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endobj
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6 0 obj
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<<
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/Type /Font
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/Subtype /Type1
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/Name /F1
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/BaseFont /Helvetica
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/Encoding /WinAnsiEncoding
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>>
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endobj
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xref
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0 7
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0000000000 65535 f
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0000000009 00000 n
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0000000063 00000 n
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0000000135 00000 n
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000000307 00000 n
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0000000403 0000 n
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0000000438 00000 n
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trailer <<
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/Size 7
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/Root 1 0 R
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>>
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startxref
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556
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%%EOF
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