#373 Fill NPE when aesKeyStrength is null

src/main/java/net/lingala/zip4j/io/inputstream/AesCipherInputStream.java

@@ -158,6 +158,11 @@ private byte[] getSalt(LocalFileHeader localFileHeader) throws IOException {
     }
 
     AESExtraDataRecord aesExtraDataRecord = localFileHeader.getAesExtraDataRecord();
+
+    if (aesExtraDataRecord.getAesKeyStrength() == null) {
+      throw new IOException("Invalid aes key strength in aes extra data record");
+    }
+
     byte[] saltBytes = new byte[aesExtraDataRecord.getAesKeyStrength().getSaltLength()];
     readRaw(saltBytes);
     return saltBytes;

src/test/java/net/lingala/zip4j/io/inputstream/ZipInputStreamIT.java

@@ -301,6 +301,15 @@ public void testExtractZipFileWithDirectoriesContainingExtendedLocalFileHeader()
         null, InternalZipConstants.BUFF_SIZE, false, 2);
   }
 
+  @Test
+  public void testExtractZipFileWithNullAesExtraDataRecordThrowsException() throws IOException {
+    expectedException.expect(IOException.class);
+    expectedException.expectMessage("Invalid aes key strength in aes extra data record");
+
+    extractZipFileWithInputStreams(TestUtils.getTestArchiveFromResources("null-aes-key-strength-in-aes-extra-data-record"),
+        null, InternalZipConstants.BUFF_SIZE, false, 1);
+  }
+
   private void extractZipFileWithInputStreams(File zipFile, char[] password) throws IOException {
     extractZipFileWithInputStreams(zipFile, password, InternalZipConstants.BUFF_SIZE);
   }