smartmontools and kern.securelevel

[Warner Losh]

On Fri, Feb 23, 2018 at 9:46 AM, Ben RUBSON <ben.rubson at gmail.com> wrote:

> On 23 Feb 2018, Warner Losh wrote:
>
> On Fri, Feb 23, 2018 at 8:20 AM, Ben RUBSON <ben.rubson at gmail.com> wrote:
>>
>> Hi,
>>>
>>> I run smartmontools on my storage servers, to launch periodic disk tests
>>> and alert on disk errors.
>>>
>>> Unfortunately, if we set sysctl kern.securelevel >=2, smartmontools does
>>> not work anymore.
>>> Certainly because it needs to write directly to raw devices.
>>> (details of the levels, -1 to 3, in security(7))
>>>
>>> Any workaround to this ?
>>>
>>> Perhaps we could think about allowing SMART commands to be written to
>>> disks when sysctl kern.securelevel >=2 ?
>>> (I assume smartmontools writes SMART commands)
>>>
>>
>> Sending raw disks commands is inherently insecure. It's hard to create a
>> list of those commands that are OK because of the complexity and diversity
>> of the needed functionality. That complexity also makes it hard to put the
>> commands into a series of ioctls which could be made more secure.
>>
>
> Thank you for your feedback Warner.
>
> Can't all SMART commands be easily identified among the others ? (when a
> command arrives, does kernel sees it is SMART flagged ?)
> Perhaps you assume some SMART commands may be dangerous for the disks'
> data itself ?
>

Yes. I do. They can be.

Warner