I need to prevent a document from being saved / saved as (say from ms word). I've looked around and I havn't quite found a satifying answer. I've considered EFS... but I don't think it prevents the user from saving the document as... (though it prevents access to the original source file). Any ideas outthere?
Run it on completely locked-down system with read-only disk, no network and no removable drives. Access to the computer must be phisically restricted as well.
This should prevent Save As from working, but still won't prevent document from being copied (someone may take photo of the screen and OCR it).
It usually isn't worth it to disable Save As, because you need access to the original in order to open it in the first place. There are always ways to copy a file.
I had the same issue come up when someone asked me to disable Save As for a PDF.
There is no way take an arbitrary document and modify it in such a way that it cannot be saved. You could modify a program such as Word not to allow Save or Save As but that would still allow someone to open and save the document with a different program or on a different machine.
Related
I have a MacOS app coded in swift, and when someone right clicks > show package contents there is a file that reveals some information I do not want the user to see. Is it at all possible to hide that file?
There's no way to secure data on the client (mac) side. If your program can read something, so can a hacker. You can do 3 things about it:
Make it obfuscated enough to make it annoying to deal with, hoping that bad actors would get discouraged.
Make the reward of reading the sensitive data lower, so there's less incentive to do so
Make the sensitive data be black boxed by a server you control and have secured, and have all the sensitive operations be out-sourced to computation on that secure server.
No, you can't hide files in a meaningful way.
If you name the file starting with a dot (".") they are not shown in the Finder by default, but that's very easy to get around.
Better to encrypt the file and decrypt it in your app. That way nosy users can see the file but can't make any sense out of the contents.
I think a student of mine renamed a PNG a Word document and intentionally submitted a corrupted file to buy more time (or something) on an assignment. The student denies everything and claims it was a computer malfunction. Before I submit an honor code violation I want to be sure that there's no explanation that does not involve cheating that I'm somehow overlooking.
Basically, I'm a TA and a student submitted a paper, let's say it was Smith.docx. When I was working on grading and went to open Smith.docx Word wouldn't open it and said that it was corrupted. I eventually had the idea of opening it in a text editor and there it was a massive jumbled file of all sorts of odd characters (total file size: 180kb for what was supposed to be a 5 page paper).
I noticed, though, that the first few characters of the file were:
‰PNG
I renamed the file Smith.png and it opened. Bizarrely, it was an image of the first page of a Word document. More specifically, it looks like a screenshot of a Word doc cropped so as to show just the page. What makes it seem like a screenshot is that the cursor thingy (the vertical bar marking where you're typing) shows up next to the title.
An additional interesting bit of data is that if I scroll further down in the file (opened in notepad) I come to this:
XML:com.adobe.xmp <x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="XMP Core 5.4.0">
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
<rdf:Description rdf:about=""
xmlns:exif="http://ns.adobe.com/exif/1.0/">
<exif:PixelXDimension>996</exif:PixelXDimension>
<exif:PixelYDimension>1286</exif:PixelYDimension>
</rdf:Description>
</rdf:RDF>
</x:xmpmeta>
I'm not sure what all that means but 1286x996 are the dimensions of the png image. The rest suggests to me that the file was created in some Adobe program but I'm not sure if that's right and how to figure out more about that.
So, my actual question: Is there any conceivable explanation of any kind for how I would come to have a file called Smith.docx that is a perfectly functioning png of what sure looks like a screenshot of the first page of a Word document other than that the student did it on purpose? The student claimed that their computer was "corrupting" files and that they had to take it into the Apple for service. I find this incredibly implausible (student has also not provided the receipt for this, which I requested).
Additionally, other than the case I laid out here, is there any positive evidence for my theory (that it was a straightforward case of cheating) that I can present to strengthen my case? eg, is the data from the file that I posted above a smoking gun that it was created in an Adobe program or is there any conceivable way that could come out of a Word document or other sort of corrupted file?
Also, is there anything else I can look for in the PNG file that would be a smoking gun?
Thanks in advance for any help you might be able to offer!
just rename the file with .png at the end instead of .docx and if it was a png then it should open just fine as a png
The key is that you see the cursor in the screenshot, there is no way Word would export (somehow) a docx file as a png AND draw the cursor for typing. Also, any tool that could do that would save the file as png not docx, only the user could deliberately change the file extension.
Also, does the screenshot show an empty document? or it looks like the final document your student delivered at the end?
Short answer:
The student is lying and is in fact a cheater (in my opinion).
Also, even if they were telling the truth, it is still their responsibility to have their work done, ready, and fully functional on time. Your computer is corrupting your files? Tough cookies. No one cares. You should have done your work on another computer. In the real world, excuses don't get you anywhere and they shouldn't get you anywhere in school either.
Lastly, it is very easy to re-name an extension of another file type and claim it's corrupt and very unlikely that a computer is just creating corrupted files. If their computer would otherwise create corrupted files, I would imagine it would be nearly impossible to get the computer to boot. In other words, they probably wouldn't have been able to turn on their "corrupted" computer to create "corrupted" files in the first place.
I find many similar question but i didn't get solution for this.
Is it possible to upload some file like image, document, zip file to upload on iCloud programmatically?
See table 4-1 in the documentation:
How do you manage the data? Manage files and directores using the
NSFileManager class. Open, close, read, and write files using standard
file system routines.
So if you can create a file, you can store it in iCloud. But remember there's a finite, relatively small amount of space available.
iCloud can handle all kinds of files. So if you want rot use an obscure file format or invent your own, go for it. It only can to be converted into a byte stream/NSData, but then again, what isn't?
Check this tutorial walkthrough app. It shows how to create, modify and delete files for iCloud.
http://github.com/lichtschlag/iCloudPlayground
any recommendations for saving four strings into an own file format that is read by the application and can be shared?
In my app, you will be able to enter some text in some boxes and the app shows a view with an background image and those strings. Now, I am already able to save this as a picture, but I actually want to save it to an own file format so that you can save different files that can be modified afterwards as well or even exchanged via email and opened from another iphone with the app.
Now, I wrote the code for accessing the documents folder of the app, as well as saving and deleting. Thing is, i dont know how to store those strings in a file (perhaps in a xml?) and read them easily afterwards from my application.
For the exchanging part, I found that link which would be a nice feature indeed: http://iosdevelopertips.com/cocoa/launching-your-own-application-via-a-custom-url-scheme.html
Parsing xml seems not that difficult (never done it before): http://ipad.about.com/od/iPad-App-Dev/a/How-To-Parse-Xml-Files-In-Xcode-Objective-C.htm
If it's only a small bit of infomation then the easiest way to store your data in a file would be using a plist - there's a good tutorial here - http://www.icodeblog.com/2009/02/14/loading-data-from-plist-files/
In addition to the plist, you could also do the following approaches:
1) simplest - open a file in your documents directory, write the 4 strings (using whatever delimiter/end of string marker is useful - carriage return?) and overwrite them each time through. (i.e. it's your file, you can format it how you like)
2) mildly harder - use Apple's NSArchive to pack and unpack the strings.
3) possible overkill - store them directly in a SQLite database
4) major overkill - store them in CoreData.
Of course, the "overkill" options also provide you with extra features which may be of use if your app functionality extends beyond what you've outlined.
By sharing, I would think that simple copy and paste might be enough, but there's also sending it via email, or tripping another app's URL scheme to make it open it and sending the strings as part of the URL. You'd have to know that the other app would be able to interpret your strings as part of the URL, so you might have to write it yourself.
Okay guys I found that very nice method in the NSString documentation:
–writeToFile:atomically:encoding:error:
I think I am gonna separate my strings by /n and save them to a .txt. When I am gonna read the file afterwards, i am getting the string, divide it to substrings. That will do it, I guess.
One last question: Is it possible to replace the content of my file so that I won't need to create a new file every time i want to change something?
Thanks!
In my app, the user can save his input to disk. This is done with NSKeyedArchiver. Currently I simply name my files with a timestamp. But of course, the user may want to load one of them back in to keep on editing them.
What would be the most reliable / safe strategy to keep track of those files? I need to present the user a list of those files, so that he can choose one to open.
Currently I think of making an archived NSMutableArray which simply stores the file names, but I feel that this strategy is not really good. We all know when we save files sometimes something goes wrong, and this seems very likely to get currupted easily, or not? How would you do it?
If you've got all your files in one directory, and nothing else there, I would use -[NSFileManager contentsOfDirectoryAtPath:error:] to fetch an array of filenames in there. That's a little more robust than tracking these manually.