Intercepting memory mapped files

[Kunal Baweja]

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;
    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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