Intercepting memory mapped files

[Kunal Baweja]

Hi devendra, it's not necessary to wrap around the characters in caeser
cipher by taking a modulus like you pointed out, there are many variants of
it. Anyways my actual problem is that the encrypted data is not being
written into the file whereas if I don't make a call to the encrypt
function then the contents are written perfectly to the files.

On 5:25pm, Fri 30-Jan-2015 devendra.aaru <devendra.aaru at gmail.com> wrote:

> 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
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>>>>
>>>>
>>>
>>
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