Handle more broken files

Space rather than newline after xref, missing /ID in trailer for encrypted file. This enables qpdf to handle some files that xpdf can handle. Adobe reader can't necessarily handle them.

Handle more broken files
Space rather than newline after xref, missing /ID in trailer for encrypted file. This enables qpdf to handle some files that xpdf can handle. Adobe reader can't necessarily handle them.
Jay Berkenbilt
1 parent a1d5a3e9
Showing 7 changed files with 59 additions and 11 deletions
ChangeLog
libqpdf/QPDF.cc
libqpdf/QPDF_encryption.cc
qpdf/qpdf.testcov
qpdf/qtest/qpdf.test
qpdf/qtest/qpdf/invalid-id-xref.out
qpdf/qtest/qpdf/invalid-id-xref.pdf
+2013-06-15  Jay Berkenbilt  <ejb@ql.org>
+
+	* Handle some additional broken files with missing /ID in trailer
+	for encrypted files and with space rather than newline after xref.
+
 2013-06-14  Jay Berkenbilt  <ejb@ql.org>
  
 	* Detect and correct /Outlines dictionary being a direct object
@@ -430,11 +430,22 @@ QPDF::read_xref(qpdf_offset_t xref_offset)
     std::map<int, int> free_table;
     while (xref_offset)
     {
+        char buf[7];
+        memset(buf, 0, sizeof(buf));
 	this->file->seek(xref_offset, SEEK_SET);
-	std::string line = this->file->readLine(50);
-	if (line == "xref")
+	this->file->read(buf, sizeof(buf) - 1);
+        // The PDF spec says xref must be followed by a line
+        // terminator, but files exist in the wild where it is
+        // terminated by arbitrary whitespace.
+        PCRE xref_re("^xref\\s+");
+	PCRE::Match m = xref_re.match(buf);
+	if (m)
 	{
-	    xref_offset = read_xrefTable(this->file->tell());
+            QTC::TC("qpdf", "QPDF xref space",
+                    ((buf[4] == '\n') ? 0 :
+                     (buf[4] == '\r') ? 1 :
+                     (buf[4] == ' ') ? 2 : 9999));
+	    xref_offset = read_xrefTable(xref_offset + m.getMatch(0).length());
 	}
 	else
 	{
@@ -791,17 +791,24 @@ QPDF::initializeEncryption()
     // encryption dictionary.
     this->encrypted = true;
  
+    std::string id1;
     QPDFObjectHandle id_obj = this->trailer.getKey("/ID");
-    if (! (id_obj.isArray() &&
-	   (id_obj.getArrayNItems() == 2) &&
-	   id_obj.getArrayItem(0).isString()))
+    if ((id_obj.isArray() &&
+         (id_obj.getArrayNItems() == 2) &&
+         id_obj.getArrayItem(0).isString()))
     {
-	throw QPDFExc(qpdf_e_damaged_pdf, this->file->getName(),
-		      "trailer", this->file->getLastOffset(),
-		      "invalid /ID in trailer dictionary");
+        id1 = id_obj.getArrayItem(0).getStringValue();
+    }
+    else
+    {
+        // Treating a missing ID as the empty string enables qpdf to
+        // decrypt some invalid encrypted files with no /ID that
+        // poppler can read but Adobe Reader can't.
+	warn(QPDFExc(qpdf_e_damaged_pdf, this->file->getName(),
+                     "trailer", this->file->getLastOffset(),
+                     "invalid /ID in trailer dictionary"));
     }
  
-    std::string id1 = id_obj.getArrayItem(0).getStringValue();
     QPDFObjectHandle encryption_dict = this->trailer.getKey("/Encrypt");
     if (! encryption_dict.isDictionary())
     {
@@ -264,3 +264,4 @@ QPDFObjectHandle inline image token 0
 QPDF not caching overridden objstm object 0
 QPDFWriter original obj non-zero gen 0
 QPDF_optimization indirect outlines 0
+QPDF xref space 2
@@ -199,7 +199,7 @@ $td-&gt;runtest(&quot;remove page we don&#39;t have&quot;,
 show_ntests();
 # ----------
 $td->notify("--- Miscellaneous Tests ---");
-$n_tests += 64;
+$n_tests += 65;
  
 $td->runtest("qpdf version",
 	     {$td->COMMAND => "qpdf --version"},
@@ -509,6 +509,14 @@ $td-&gt;runtest(&quot;check file&quot;,
              {$td->FILE => "a.pdf"},
              {$td->FILE => "gen1.qdf"});
  
+# This file, from a user, is missing /ID in its trailer even though it
+# is encrypted and also has a space instead of a newline after its
+# xref keyword.  xpdf can open it, but Adobe reader can't.
+$td->runtest("check broken file",
+             {$td->COMMAND => "qpdf --check invalid-id-xref.pdf"},
+             {$td->FILE => "invalid-id-xref.out", $td->EXIT_STATUS => 3},
+             $td->NORMALIZE_NEWLINES);
+
 show_ntests();
 # ----------
 $td->notify("--- Numeric range parsing tests ---");
+WARNING: invalid-id-xref.pdf (trailer, file position 2493795): invalid /ID in trailer dictionary
+checking invalid-id-xref.pdf
+PDF Version: 1.1
+R = 3
+P = -1804
+User password = 
+extract for accessibility: not allowed
+extract for any purpose: allowed
+print low resolution: allowed
+print high resolution: allowed
+modify document assembly: not allowed
+modify forms: not allowed
+modify annotations: allowed
+modify other: not allowed
+modify anything: not allowed
+File is not linearized