Re: [gentoo-user] hard drive encryption

[Michael Mol <mikemol@gmail.com>]

On Tue, Mar 13, 2012 at 12:49 PM, Florian Philipp <lists@binarywings.net> wrote:
> Am 13.03.2012 17:26, schrieb Michael Mol:
>> On Tue, Mar 13, 2012 at 12:11 PM, Florian Philipp <lists@binarywings.net> wrote:
>>> Am 13.03.2012 12:55, schrieb Valmor de Almeida:
>>>> On 03/11/2012 02:29 PM, Florian Philipp wrote:
>>>>> Am 11.03.2012 16:38, schrieb Valmor de Almeida:
>>>>>>
>>>>>> Hello,
>>>>>>
>>>>>> I have not looked at encryption before and find myself in a situation
>>>>>> that I have to encrypt my hard drive. I keep /, /boot, and swap outside
>>>>>> LVM, everything else is under LVM. I think all I need to do is to
>>>>>> encrypt /home which is under LVM. I use reiserfs.
>>>>>>
>>>>>> I would appreciate suggestion and pointers on what it is practical and
>>>>>> simple in order to accomplish this task with a minimum of downtime.
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> --
>>>>>> Valmor
>>>>>>
>>>>>
>>>>>
>>>>> Is it acceptable for you to have a commandline prompt for the password
>>>>> when booting? In that case you can use LUKS with the /etc/init.d/dmcrypt
>>>>
>>>> I think so.
>>>>
>>>>> init script. /etc/conf.d/dmcrypt should contain some examples. As you
>>>>> want to encrypt an LVM volume, the lvm init script needs to be started
>>>>> before this. As I see it, there is no strict dependency between those
>>>>> two scripts. You can add this by adding this line to /etc/rc.conf:
>>>>> rc_dmcrypt_after="lvm"
>>>>>
>>>>> For creating a LUKS-encrypted volume, look at
>>>>> http://en.gentoo-wiki.com/wiki/DM-Crypt
>>>>
>>>> Currently looking at this.
>>>>
>>>>>
>>>>> You won't need most of what is written there; just section 9,
>>>>> "Administering LUKS" and the kernel config in section 2, "Assumptions".
>>>>>
>>>>> Concerning downtime, I'm not aware of any solution that avoids copying
>>>>> the data over to the new volume. If downtime is absolutely critical, ask
>>>>> and we can work something out that minimizes the time.
>>>>>
>>>>> Regards,
>>>>> Florian Philipp
>>>>>
>>>>
>>>> Since I am planning to encrypt only home/ under LVM control, what kind
>>>> of overhead should I expect?
>>>>
>>>> Thanks,
>>>>
>>>
>>> What do you mean with overhead? CPU utilization? In that case the
>>> overhead is minimal, especially when you run a 64-bit kernel with the
>>> optimized AES kernel module.
>>
>> Rough guess: Latency. With encryption, you can't DMA disk data
>> directly into a process's address space, because you need the decrypt
>> hop.
>>
>
> Good call. Wouldn't have thought of that.
>
>> Try running bonnie++ on encrypted vs non-encrypted volumes. (Or not; I
>> doubt you have the time and materials to do a good, meaningful set of
>> time trials)
>>
>
> Yeah, that sounds like something for which you need a very dull winter
> day. Besides, I've already lost a poorly cooled HDD on a benchmark.

Sounds like something we can do at my LUG at one of our weekly
socials. The part I don't know is how to set this kind of thing up and
how to tune it; I don't want it to be like Microsoft's comparison of
SQL Server against MySQL from a decade or so ago, where they didn't
tune MySQL for their bench workload.

-- 
:wq