lclean
Documentation
Version 1.0
lclean is a program that allows you to detect, save and clean the
trash sections of OLE style documents.
Note:
This program changes your document! If you use lclean, please keep a backup
of the treated files, until you are sure they did not take any harm!
Why lclean?
- Microsoft's first and still most spreaded OLE implementations had bugs.
One caused that some sections of documents that actually should be filled
with zero bytes contained more or less private data.
- Management of OLE documents is difficult and takes a little time.
A way to fasten this up is not to care about the old data, but simply to
add the new data to the document. Clean up could be done later when
there was time. When switched on the "fast save" option, Microsoft Word
uses this strategy. So, thus saved files contain the new and the old
version of a document. The old data cannot be edited any more and stays
invisible in the document.
- Some programs seem to use the Microsoft OLE library not properly.
For example, the Star Office 3.1. programs create documents, that
always contain 1024 bytes of trash.
- As far as I know, Microsoft offers a bugfix for 32 bit Windows
systems, only.
The program "lclean" can access this kind of garbage in OLE documents.
To do this it uses the laola_modify_trash function of the "laola.pl"
library. This library decides between four different types of trash. To
understand them fully, you will have to look at the source code.
In short:
- Unused "big blocks". These blocks are not used by the document. Each of
these blocks is 512 bytes long.
- Unused "small blocks". These blocks are not used by the document. Each of
these blocks is 64 bytes long.
- File end space. This refers to the "streams" of an OLE document.
The space is made up of all the space between the end of a stream
and the end of a block.
- System space. These sections are required by file format, though
they are not used by OLE system. Actually this data is no garbage.
You can do several things:
- Get a trash report
- lclean -r {document}
Gives a little report about the trash in the document(s).
- Clean the trash
- lclean -c [-n] {document}
The trash sections will be cleaned. Unused blocks are filled with null
bytes. System data will be cleaned with 0xff bytes. File end trash
(type 4) will be cleaned with random bytes. When using switch -n, file
end trash will be filled also with zero bytes (faster on files with
lots of embedded objects).
- Save the trash to files
- lclean -s [-a] [-d] [-z] {document}
The trash sections will be saved to own files. They will be stored to
an directory in your current directory. Normally it will be the directory
"doctrash". E.g., if there is the example file
"legacy.doc" the trashfiles will be stored as:
"doctrash/legacy.tr1", "doctrash/legacy.tr2",
"doctrash/legacy.tr3" and "doctrash/legacy.tr4".
- When using switch -a, all trash will be stored into one big file
"doctrash/legacy.tra".
- When using switch -d, the trash file(s) will not be stored into
directory "doctrash", but into each an own directory. E.g.
into directory "legacy/".
- When using switch -z, zero length files will not be created.
- Example: lclean -cs {document}
This would first save all trash chunks into separate files into
directory "doctrash", then it would clean the document.
- Insert a file into the document (hide it)
- lclean -i <file> [-a] {document}
Instead of trash, some <file> can thus be stored into the
document. This file cannot be seen by the documents application. The
file may of course not be bigger, than the size of the trash in your
documents (plus 20 bytes plus the size to store the filename). Normally,
only trash types 1 and 2 will be used for this. If they offer not
enough space, with switch -a trash type 4 and 8 will be used, too.
- Example: lclean -aci <file> {document}
This would first clean the document, then insert the hidden file
by using all trash types.
- List if there is a file inserted into the documents trash
- lclean -l {document}
- Extract the hidden file
- lclean -e [-f] [-z] {document}
This makes a copy of the hidden file. If the file got corrupted by what
reason ever, it will not be extracted. The file will get the date of its
last modification. If the file already exists, you will be prompted to
overwrite it with the new extracted file. With switch -f you will not be
prompted, but the file will be overwritten. With switch -z, no zero
length files will be created.
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