Bug 66425: Avoid a NullPointerException found via oss-fuzz

We try to avoid throwing NullPointerException, but it was possible
to trigger one here with a specially crafted input-file

Should fix https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=62626

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1912792 13f79535-47bb-0310-9956-ffa450edef68

poi-scratchpad/src/test/java/org/apache/poi/hslf/dev/BaseTestPPTIterating.java

@@ -68,6 +68,7 @@ public abstract class BaseTestPPTIterating {
         EXCLUDED.put("clusterfuzz-testcase-minimized-POIHSLFFuzzer-5962760801091584.ppt", RuntimeException.class);
         EXCLUDED.put("clusterfuzz-testcase-minimized-POIHSLFFuzzer-5231088823566336.ppt", FileNotFoundException.class);
         EXCLUDED.put("clusterfuzz-testcase-minimized-POIFuzzer-6411649193738240.ppt", FileNotFoundException.class);
+        EXCLUDED.put("clusterfuzz-testcase-minimized-POIHSLFFuzzer-4838893004128256.ppt", FileNotFoundException.class);
     }
 
     public static Stream<Arguments> files() {

poi-scratchpad/src/test/java/org/apache/poi/hslf/dev/TestPPTXMLDump.java

@@ -67,7 +67,8 @@ public class TestPPTXMLDump extends BaseTestPPTIterating {
         if (pFile.getName().equals("clusterfuzz-testcase-minimized-POIFuzzer-5429732352851968.ppt") ||
                 pFile.getName().equals("clusterfuzz-testcase-minimized-POIFuzzer-5681320547975168.ppt") ||
                 pFile.getName().equals("clusterfuzz-testcase-minimized-POIHSLFFuzzer-5231088823566336.ppt") ||
-                pFile.getName().equals("clusterfuzz-testcase-minimized-POIFuzzer-6411649193738240.ppt")) {
+                pFile.getName().equals("clusterfuzz-testcase-minimized-POIFuzzer-6411649193738240.ppt") ||
+                pFile.getName().equals("clusterfuzz-testcase-minimized-POIHSLFFuzzer-4838893004128256.ppt")) {
             throw new FileNotFoundException();
         }
     }

poi/src/main/java/org/apache/poi/poifs/crypt/agile/AgileEncryptionHeader.java

@@ -79,10 +79,14 @@ public class AgileEncryptionHeader extends EncryptionHeader {
                     keyData.getHashAlgorithm() + " @ " + hashSize + " bytes");
         }
 
+        if (keyData.getSaltSize() == null) {
+            throw new EncryptedDocumentException("Invalid salt length: " + keyData.getSaltSize());
+        }
+
         int saltLength = keyData.getSaltSize();
         setKeySalt(keyData.getSaltValue());
         if (getKeySalt().length != saltLength) {
-            throw new EncryptedDocumentException("Invalid salt length");
+            throw new EncryptedDocumentException("Invalid salt length: " + getKeySalt().length + " and " + saltLength);
         }
 
         DataIntegrity di = ed.getDataIntegrity();