Intercepting memory mapped files

[devendra.aaru]

On Fri, Jan 30, 2015 at 6:48 AM, Kunal Baweja <bawejakunal15 at gmail.com>
wrote:

> Yeah I was trying something similar only but with a much simpler Caeser
> cipher function of my own written as below:
>
> void encrypt(char *data, char *encrypted, size_t size)
> {
>     unsigned int i;
>     for(i=0;i<(unsigned int)size;i++)
>         encrypted[i] = data[i] + 3;
>

This is not caesar's cipher. If your buffer contains alphabets then only
you can apply caesar cipher.

It should be something like

          encrypted[i] = (data[i] - 3) % 26;



>     printk(KERN_INFO "%s",encrypted);
>     return;
> }
>
> So in the given code wherever u see the calls to *wrapfs_encrypt*, I have
> replaced with my simpler encryption function.
>
> But I am not able to figure out why calling this function creates a
> problem, the printk() statement inside the function shows me the correctly
> encrypted contents but the file is still blank.
>
> Thanks
>
> *Kunal Baweja*
>
> Undergraduate B.E. (Hons.) Computer Science
> Birla Institute Of Technology & Science, Pilani
> K.K. Birla Goa Campus
> +91 9049655665
>
> On Fri, Jan 30, 2015 at 4:03 PM, Saket Sinha <saket.sinha89 at gmail.com>
> wrote:
>
>> HI,
>>
>> Kindly refer the following link that implements a minimal encryption over
>> wrapfs.
>> https://github.com/piekill/wrapfs
>>
>> Go through the wrapfs_encrypt in wrapfs_readpage and wrapfs_decrypt in
>> wrapfs_writepage.
>>
>> Regards,
>> Saket Sinha
>>
>> On Fri, Jan 30, 2015 at 3:56 PM, Kunal Baweja <bawejakunal15 at gmail.com>
>> wrote:
>>
>>> Hi,
>>> I am currently working on implementing a simple encrypted file system
>>> using a stackable file system WrapFS <http://wrapfs.filesystems.org/>.
>>> In order to do so, as I read in the WrapFS mailing list
>>> <http://www.fsl.cs.sunysb.edu/pipermail/wrapfs/2011-November/000058.html>
>>> one needs to implement address space operations, which I have done and
>>> posted on my github at this link
>>> <https://github.com/bawejakunal/wrapfs-addresspace-operations/blob/master/mmap.c>
>>> and it works fine. But now when I am trying to modify the data before being
>>> written in wrapfs_lower() function I get a blank output in files written
>>> out.
>>> Please guide where am I going wrong in modifying the data to be written
>>> and what could be the best way to decrypt it ?
>>>
>>> Thanks
>>>
>>> *Kunal Baweja*
>>>
>>> Undergraduate B.E. (Hons.) Computer Science
>>> Birla Institute Of Technology & Science, Pilani
>>> K.K. Birla Goa Campus
>>> +91 9049655665
>>>
>>> _______________________________________________
>>> Kernelnewbies mailing list
>>> Kernelnewbies at kernelnewbies.org
>>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>>
>>>
>>
>
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