FileDocCategorySizeDatePackage
EncryptedSlideShow.javaAPI DocApache Poi 3.0.14643Thu May 31 18:45:28 BST 2007org.apache.poi.hslf

EncryptedSlideShow

public class EncryptedSlideShow extends Object
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

Fields Summary
Constructors Summary
Methods Summary
public static booleancheckIfEncrypted(org.apache.poi.hslf.HSLFSlideShow hss)
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

		// 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;
public static org.apache.poi.hslf.record.DocumentEncryptionAtomfetchDocumentEncryptionAtom(org.apache.poi.hslf.HSLFSlideShow hss)
Return the DocumentEncryptionAtom for a HSLFSlideShow, or null if there isn't one.

return
a DocumentEncryptionAtom, or null if there isn't one

		// Will be the last Record pointed to by the 
		//  first PersistPrtHolder, if there is one
		
		CurrentUserAtom cua = hss.getCurrentUserAtom();
		if(cua.getCurrentEditOffset() != 0) {
			// Check it's not past the end of the file
			if(cua.getCurrentEditOffset() > hss.getUnderlyingBytes().length) {
				throw new CorruptPowerPointFileException("The CurrentUserAtom claims that the offset of last edit details are past the end of the file");
			}
			
			// 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;