Re[2]: Encryption/password protected excel/word files

[Yegor Kozlov <ye...@dinom.ru>]

I wonder if Microsoft uses encryption compatible with
javax.crypto.*. If yes, we have a chance to decode it. Otherwise it is
not worth the trouble.

Yegor

NB> On Tue, 17 Apr 2007, Justin Warren wrote:
>> I should mention that the exceptions don't really tell if the files are 
>> password protected or not. For word, I catch an 
>> ArrayIndexOutOfBoundsException, or java.lang.NegativeArraySizeException. 
>> I'm guessing that is not the expected behaviour.

NB> With powerpoint, we did find one record we could look for early on that 
NB> indicates if the file is encrypted or not. For the others, we haven't 
NB> spotted anything suitable.

NB> The problem is that if the file is encrypted, lots of the core records are 
NB> there, but there data is encrytped, and hence garbage if you try to read 
NB> it as if it wasn't. Unless we can tell very early on that a file is 
NB> encrypted, we can't just look through the record list looking for the 
NB> encrypted record flag, since the parent records can't be read properly. 
NB> Instead, we must find either a absolute offset to an indicator, or one 
NB> non encrypted record at a given location that'll have a child that tells 
NB> you it's encrypted.


NB> If someone encrypts both the properties and the document, it's easy, as 
NB> you can tell at the poifs level. If they just encrypt the document, it's 
NB> hard. See EncryptedSlideShow in hslf for an example of how to do it for 
NB> powerpoint. Any suggestions for a similar way to do it for word or excel 
NB> gratefully received :)

NB> Nick

NB> ---------------------------------------------------------------------
NB> To unsubscribe, e-mail: poi-user-unsubscribe@jakarta.apache.org
NB> Mailing List:     http://jakarta.apache.org/site/mail2.html#poi
NB> The Apache Jakarta Poi Project:  http://jakarta.apache.org/poi/


---------------------------------------------------------------------
To unsubscribe, e-mail: poi-user-unsubscribe@jakarta.apache.org
Mailing List:     http://jakarta.apache.org/site/mail2.html#poi
The Apache Jakarta Poi Project:  http://jakarta.apache.org/poi/

Re[2]: Encryption/password protected excel/word files

[Nick Burch <ni...@torchbox.com>]

On Tue, 17 Apr 2007, Yegor Kozlov wrote:
> I wonder if Microsoft uses encryption compatible with javax.crypto.*. If 
> yes, we have a chance to decode it. Otherwise it is not worth the 
> trouble.

I don't think they do. For PPT, there's a choice of about 10 different 
encryption options, almost all of which have very similar names, and most 
of them have Microsoft somewhere in their name...

I think that supporting encrypting / decrypting the files is not going to 
be possible. However, we might be able to detect encrypted files (as we do 
for ppt), but it'll take some work.

Nick

---------------------------------------------------------------------
To unsubscribe, e-mail: poi-user-unsubscribe@jakarta.apache.org
Mailing List:     http://jakarta.apache.org/site/mail2.html#poi
The Apache Jakarta Poi Project:  http://jakarta.apache.org/poi/