Explicitly check root dictionary type

Very badly corrupted files may not have a retrievable root dictionary.
Handle that as a special case so that a more helpful error message can
be provided.

7 files changed, 14 insertions, 7 deletions

diff --git a/libqpdf/QPDF.cc b/libqpdf/QPDF.cc
index b5c1212c..4d5bf67f 100644
--- a/libqpdf/QPDF.cc
+++ b/libqpdf/QPDF.cc
@@ -2028,7 +2028,14 @@ QPDF::getTrailer()
 QPDFObjectHandle
 QPDF::getRoot()
 {
-    return this->trailer.getKey("/Root");
+    QPDFObjectHandle root = this->trailer.getKey("/Root");
+    if (! root.isDictionary())
+    {
+        throw QPDFExc(qpdf_e_damaged_pdf, file->getName(),
+                      "", file->getLastOffset(),
+                      "unable to find /Root dictionary");
+    }
+    return root;
 }
 
 void
diff --git a/qpdf/qtest/qpdf/bad35-recover.out b/qpdf/qtest/qpdf/bad35-recover.out
index db7ff5d9..dec903ec 100644
--- a/qpdf/qtest/qpdf/bad35-recover.out
+++ b/qpdf/qtest/qpdf/bad35-recover.out
@@ -1,2 +1,2 @@
 WARNING: bad35.pdf (object 1 0, file position 521): supposed object stream 1 has wrong type
-operation for Dictionary object attempted on object of wrong type
+bad35.pdf (file position 521): unable to find /Root dictionary
diff --git a/qpdf/qtest/qpdf/bad35.out b/qpdf/qtest/qpdf/bad35.out
index db7ff5d9..dec903ec 100644
--- a/qpdf/qtest/qpdf/bad35.out
+++ b/qpdf/qtest/qpdf/bad35.out
@@ -1,2 +1,2 @@
 WARNING: bad35.pdf (object 1 0, file position 521): supposed object stream 1 has wrong type
-operation for Dictionary object attempted on object of wrong type
+bad35.pdf (file position 521): unable to find /Root dictionary
diff --git a/qpdf/qtest/qpdf/issue-100.out b/qpdf/qtest/qpdf/issue-100.out
index 5ff2dc52..1a04b373 100644
--- a/qpdf/qtest/qpdf/issue-100.out
+++ b/qpdf/qtest/qpdf/issue-100.out
@@ -12,4 +12,4 @@ WARNING: issue-100.pdf (object 5 0, file position 418): /Length key in stream di
 WARNING: issue-100.pdf (object 5 0, file position 489): attempting to recover stream length
 WARNING: issue-100.pdf (trailer, file position 953): expected dictionary key but found non-name object; inserting key /QPDFFake1
 WARNING: issue-100.pdf (trailer, file position 953): dictionary ended prematurely; using null as value for last key
-operation for Dictionary object attempted on object of wrong type
+issue-100.pdf (file position 1138): unable to find /Root dictionary
diff --git a/qpdf/qtest/qpdf/issue-118.out b/qpdf/qtest/qpdf/issue-118.out
index a71c4ba9..58b0778c 100644
--- a/qpdf/qtest/qpdf/issue-118.out
+++ b/qpdf/qtest/qpdf/issue-118.out
@@ -1,3 +1,3 @@
 WARNING: issue-118.pdf (file position 732): loop detected resolving object 2 0
 WARNING: issue-118.pdf (xref stream: object 8 0, file position 732): supposed object stream 2 is not a stream
-operation for Dictionary object attempted on object of wrong type
+issue-118.pdf (file position 732): unable to find /Root dictionary
diff --git a/qpdf/qtest/qpdf/issue-99.out b/qpdf/qtest/qpdf/issue-99.out
index 89d6e174..eb20da6e 100644
--- a/qpdf/qtest/qpdf/issue-99.out
+++ b/qpdf/qtest/qpdf/issue-99.out
@@ -1,4 +1,4 @@
 WARNING: issue-99.pdf: file is damaged
 WARNING: issue-99.pdf (file position 3526): xref not found
 WARNING: issue-99.pdf: Attempting to reconstruct cross-reference table
-operation for Dictionary object attempted on object of wrong type
+issue-99.pdf (file position 4793): unable to find /Root dictionary
diff --git a/qpdf/qtest/qpdf/issue-99b.out b/qpdf/qtest/qpdf/issue-99b.out
index 355701be..8f012b1a 100644
--- a/qpdf/qtest/qpdf/issue-99b.out
+++ b/qpdf/qtest/qpdf/issue-99b.out
@@ -2,4 +2,4 @@ WARNING: issue-99b.pdf: file is damaged
 WARNING: issue-99b.pdf (object 1 0, file position 9): object with ID 0
 WARNING: issue-99b.pdf: Attempting to reconstruct cross-reference table
 WARNING: issue-99b.pdf: object 1 0 not found in file after regenerating cross reference table
-operation for Dictionary object attempted on object of wrong type
+issue-99b.pdf (file position 757): unable to find /Root dictionary