Avoid some NullPointerExceptions and ClassCastExceptions found when fuzzing Apache POI

This mostly only makes thrown exceptions a bit more consistent
or may allow some broken documents to be still read.

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1906322 13f79535-47bb-0310-9956-ffa450edef68

5 files changed, 19 insertions, 0 deletions

diff --git a/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/ReadOnlySharedStringsTable.java b/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/ReadOnlySharedStringsTable.java
index 8d90c78cce..6336836821 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/ReadOnlySharedStringsTable.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/ReadOnlySharedStringsTable.java
@@ -224,6 +224,9 @@ public class ReadOnlySharedStringsTable extends DefaultHandler implements Shared
 
     @Override
     public RichTextString getItemAt(int idx) {
+        if (strings == null || idx >= strings.size()) {
+            throw new IllegalStateException("Cannot get item at " + idx + " with strings: " + strings);
+        }
         return new XSSFRichTextString(strings.get(idx));
     }
 
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/XSSFReader.java b/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/XSSFReader.java
index 8a2fd78c3c..c4062e1cd6 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/XSSFReader.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xssf/eventusermodel/XSSFReader.java
@@ -300,6 +300,9 @@ public class XSSFReader {
          * @throws IOException if there is an I/O issue reading the data
          */
         protected SheetIterator(PackagePart wb) throws IOException, InvalidFormatException {
+            if (wb == null) {
+                throw new InvalidFormatException("Cannot create sheet-iterator with missing package part for workbook");
+            }
 
             /*
              * The order of sheets is defined by the order of CTSheet elements in workbook.xml
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFSheet.java b/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFSheet.java
index 7dec278354..3cc13f1d9c 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFSheet.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xssf/usermodel/XSSFSheet.java
@@ -3751,6 +3751,10 @@ public class XSSFSheet extends POIXMLDocumentPart implements Sheet, OoxmlSheetEx
     }
 
     protected void write(OutputStream out) throws IOException {
+        if (worksheet == null) {
+            throw new POIXMLException("Cannot write invalid sheet, internal data is missing");
+        }
+
         boolean setToNull = false;
         if(worksheet.sizeOfColsArray() == 1) {
             CTCols col = worksheet.getColsArray(0);
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xwpf/usermodel/XWPFComments.java b/poi-ooxml/src/main/java/org/apache/poi/xwpf/usermodel/XWPFComments.java
index 203ac46288..1aff90af29 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xwpf/usermodel/XWPFComments.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xwpf/usermodel/XWPFComments.java
@@ -59,6 +59,10 @@ public class XWPFComments extends POIXMLDocumentPart {
      */
     public XWPFComments(POIXMLDocumentPart parent, PackagePart part) {
         super(parent, part);
+
+        if (!(getParent() instanceof XWPFDocument)) {
+            throw new IllegalStateException("Parent is not a XWPFDocuemnt: " + getParent());
+        }
         this.document = (XWPFDocument) getParent();
 
         if (this.document == null) {
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xwpf/usermodel/XWPFPicture.java b/poi-ooxml/src/main/java/org/apache/poi/xwpf/usermodel/XWPFPicture.java
index da22abe359..03deae1cd1 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xwpf/usermodel/XWPFPicture.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xwpf/usermodel/XWPFPicture.java
@@ -32,6 +32,11 @@ public class XWPFPicture {
     public XWPFPicture(CTPicture ctPic, XWPFRun run) {
         this.run = run;
         this.ctPic = ctPic;
+
+        if (ctPic == null || ctPic.getNvPicPr() == null || ctPic.getNvPicPr().getCNvPr() == null) {
+            throw new IllegalArgumentException("Found missing data while reading picture data from " + ctPic);
+        }
+
         description = ctPic.getNvPicPr().getCNvPr().getDescr();
     }