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this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
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http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.poi.hslf;
import java.io.FileNotFoundException;
import org.apache.poi.hslf.record.CurrentUserAtom;
import org.apache.poi.hslf.record.DocumentEncryptionAtom;
import org.apache.poi.hslf.record.PersistPtrHolder;
import org.apache.poi.hslf.record.Record;
import org.apache.poi.hslf.record.UserEditAtom;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;
import org.apache.poi.poifs.filesystem.DocumentEntry;
import org.apache.poi.poifs.filesystem.DocumentInputStream;
import org.apache.poi.util.LittleEndian;
/**
* This class provides helper functions for determining if a
* PowerPoint document is Encrypted.
* In future, it may also provide Encryption and Decryption
* functions, but first we'd need to figure out how
* PowerPoint encryption is really done!
*
* @author Nick Burch
*/
public class EncryptedSlideShow
{
/**
* Check to see if a HSLFSlideShow represents an encrypted
* PowerPoint document, or not
* @param hss The HSLFSlideShow to check
* @return true if encrypted, otherwise false
*/
public static boolean checkIfEncrypted(HSLFSlideShow hss) {
// Easy way to check - contains a stream
// "EncryptedSummary"
POIFSFileSystem fs = hss.getPOIFSFileSystem();
try {
fs.getRoot().getEntry("EncryptedSummary");
return true;
} catch(FileNotFoundException fnfe) {
// Doesn't have encrypted properties
}
// If they encrypted the document but not the properties,
// it's harder.
// We need to see what the last record pointed to by the
// first PersistPrtHolder is - if it's a
// DocumentEncryptionAtom, then the file's Encrypted
DocumentEncryptionAtom dea = fetchDocumentEncryptionAtom(hss);
if(dea != null) {
return true;
}
return false;
}
/**
* Return the DocumentEncryptionAtom for a HSLFSlideShow, or
* null if there isn't one.
* @return a DocumentEncryptionAtom, or null if there isn't one
*/
public static DocumentEncryptionAtom fetchDocumentEncryptionAtom(HSLFSlideShow hss) {
// Will be the last Record pointed to by the
// first PersistPrtHolder, if there is one
CurrentUserAtom cua = hss.getCurrentUserAtom();
if(cua.getCurrentEditOffset() != 0) {
// Grab the details of the UserEditAtom there
Record r = Record.buildRecordAtOffset(
hss.getUnderlyingBytes(),
(int)cua.getCurrentEditOffset()
);
if(! (r instanceof UserEditAtom)) { return null; }
UserEditAtom uea = (UserEditAtom)r;
// Now get the PersistPtrHolder
Record r2 = Record.buildRecordAtOffset(
hss.getUnderlyingBytes(),
uea.getPersistPointersOffset()
);
if(! (r2 instanceof PersistPtrHolder)) { return null; }
PersistPtrHolder pph = (PersistPtrHolder)r2;
// Now get the last record
int[] slideIds = pph.getKnownSlideIDs();
int maxSlideId = -1;
for(int i=0; i<slideIds.length; i++) {
if(slideIds[i] > maxSlideId) { maxSlideId = slideIds[i]; }
}
if(maxSlideId == -1) { return null; }
int offset = (
(Integer)pph.getSlideLocationsLookup().get(
new Integer(maxSlideId)
) ).intValue();
Record r3 = Record.buildRecordAtOffset(
hss.getUnderlyingBytes(),
offset
);
// If we have a DocumentEncryptionAtom, it'll be this one
if(r3 instanceof DocumentEncryptionAtom) {
return (DocumentEncryptionAtom)r3;
}
}
return null;
}
}