Re: [gentoo-user] hard drive encryption

[Florian Philipp <lists@binarywings.net>]

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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.

Regards,
Florian Philipp


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