documentencryption.java

非常有用的操作pdf文件的java源码

        if( isUserPassword )
        {
            encryptionKey =
                encryption.computeEncryptedKey(
                    password.getBytes(), o,
                    permissions, id.getBytes(), revision, length );
        }
        else if( isOwnerPassword )
        {
            byte[] computedUserPassword =
                encryption.getUserPassword(
                    password.getBytes(),
                    o,
                    revision,
                    length );
            encryptionKey =
                encryption.computeEncryptedKey(
                    computedUserPassword, o,
                    permissions, id.getBytes(), revision, length );
        }
        else
        {
            throw new InvalidPasswordException( "Error: The supplied password does not match " +
                                                "either the owner or user password in the document." );
        }
        
        COSDictionary trailer = document.getTrailer();
        COSArray fields = (COSArray)trailer.getObjectFromPath( "Root/AcroForm/Fields" );
        
        //We need to collect all the signature dictionaries, for some
        //reason the 'Contents' entry of signatures is not really encrypted
        if( fields != null )
        {
            for( int i=0; i<fields.size(); i++ )
            {
                COSDictionary field = (COSDictionary)fields.getObject( i );
                addDictionaryAndSubDictionary( potentialSignatures, field );
            }
        }

        List allObjects = document.getObjects();
        Iterator objectIter = allObjects.iterator();
        while( objectIter.hasNext() )
        {
            decryptObject( (COSObject)objectIter.next() );
        }
        document.setEncryptionDictionary( null );
    }
    
    private void addDictionaryAndSubDictionary( Set set, COSDictionary dic )
    {
        set.add( dic );
        COSArray kids = (COSArray)dic.getDictionaryObject( "Kids" );
        for( int i=0; kids != null && i<kids.size(); i++ )
        {
            addDictionaryAndSubDictionary( set, (COSDictionary)kids.getObject( i ) );
        }
        COSBase value = dic.getDictionaryObject( "V" );
        if( value instanceof COSDictionary )
        {
            addDictionaryAndSubDictionary( set, (COSDictionary)value );
        }
    }

    /**
     * This will decrypt an object in the document.
     *
     * @param object The object to decrypt.
     *
     * @throws CryptographyException If there is an error decrypting the stream.
     * @throws IOException If there is an error getting the stream data.
     */
    private void decryptObject( COSObject object )
        throws CryptographyException, IOException
    {
        long objNum = object.getObjectNumber().intValue();
        long genNum = object.getGenerationNumber().intValue();
        COSBase base = object.getObject();
        decrypt( base, objNum, genNum );
    }

    /**
     * This will dispatch to the correct method.
     *
     * @param obj The object to decrypt.
     * @param objNum The object number.
     * @param genNum The object generation Number.
     *
     * @throws CryptographyException If there is an error decrypting the stream.
     * @throws IOException If there is an error getting the stream data.
     */
    public void decrypt( Object obj, long objNum, long genNum )
        throws CryptographyException, IOException
    {
        if( !objects.contains( obj ) )
        {
            objects.add( obj );

            if( obj instanceof COSString )
            {
                decryptString( (COSString)obj, objNum, genNum );
            }
            else if( obj instanceof COSStream )
            {
                decryptStream( (COSStream)obj, objNum, genNum );
            }
            else if( obj instanceof COSDictionary )
            {
                decryptDictionary( (COSDictionary)obj, objNum, genNum );
            }
            else if( obj instanceof COSArray )
            {
                decryptArray( (COSArray)obj, objNum, genNum );
            }
        }
    }

    /**
     * This will decrypt a stream.
     *
     * @param stream The stream to decrypt.
     * @param objNum The object number.
     * @param genNum The object generation number.
     *
     * @throws CryptographyException If there is an error getting the stream.
     * @throws IOException If there is an error getting the stream data.
     */
    private void decryptStream( COSStream stream, long objNum, long genNum )
        throws CryptographyException, IOException
    {
        decryptDictionary( stream, objNum, genNum );
        InputStream encryptedStream = stream.getFilteredStream();
        encryption.encryptData( objNum,
                                genNum,
                                encryptionKey,
                                encryptedStream,
                                stream.createFilteredStream() );
    }

    /**
     * This will decrypt a dictionary.
     *
     * @param dictionary The dictionary to decrypt.
     * @param objNum The object number.
     * @param genNum The object generation number.
     *
     * @throws CryptographyException If there is an error decrypting the document.
     * @throws IOException If there is an error creating a new string.
     */
    private void decryptDictionary( COSDictionary dictionary, long objNum, long genNum )
        throws CryptographyException, IOException
    {
        Iterator keys = dictionary.keyList().iterator();
        while( keys.hasNext() )
        {
            COSName key = (COSName)keys.next();
            Object value = dictionary.getItem( key );
            //if we are a signature dictionary and contain a Contents entry then
            //we don't decrypt it.
            if( !(key.getName().equals( "Contents" ) && 
                  value instanceof COSString && 
                  potentialSignatures.contains( dictionary )))
            {
                decrypt( value, objNum, genNum );
            }
        }
    }

    /**
     * This will decrypt a string.
     *
     * @param string the string to decrypt.
     * @param objNum The object number.
     * @param genNum The object generation number.
     *
     * @throws CryptographyException If an error occurs during decryption.
     * @throws IOException If an error occurs writing the new string.
     */
    private void decryptString( COSString string, long objNum, long genNum )
        throws CryptographyException, IOException
    {
        ByteArrayInputStream data = new ByteArrayInputStream( string.getBytes() );
        ByteArrayOutputStream buffer = new ByteArrayOutputStream();
        encryption.encryptData( objNum,
                                genNum,
                                encryptionKey,
                                data,
                                buffer );
        string.reset();
        string.append( buffer.toByteArray() );
    }

    /**
     * This will decrypt an array.
     *
     * @param array The array to decrypt.
     * @param objNum The object number.
     * @param genNum The object generation number.
     *
     * @throws CryptographyException If an error occurs during decryption.
     * @throws IOException If there is an error accessing the data.
     */
    private void decryptArray( COSArray array, long objNum, long genNum )
        throws CryptographyException, IOException
    {
        for( int i=0; i<array.size(); i++ )
        {
            decrypt( array.get( i ), objNum, genNum );
        }
    }
}