Re: [PATCH 00/11] Kernel: Improve hardening

["Peter Müller" <peter.mueller@ipfire.org>]

[-- Attachment #1: Type: text/plain, Size: 4471 bytes --]

For the records: I spoke to Arne regarding this on the phone the other day. He confirmed to
me that this is by no means a severe issue from his point of view, and will check whether
firmware flashing continues to work with the hardened kernel.

> Could you please check with Arne how severe this is for the sensors?
> 
>> On 13 Apr 2022, at 10:18, Peter Müller <peter.mueller(a)ipfire.org> wrote:
>>
>> Hello Michael,
>>
>> thanks for your e-mail.
>>
>> This is caused by the kernel lockdown patch, since /dev/ports apparently can be used to alter
>> the running kernel, hence it is no longer available if LSM runs in "integrity" mode.
>>
>> On my testing machine, sensors and sensors-detect continue to work, but any sensor that requires
>> /dev/ports access is no longer available. On my testing hardware, that does not make a difference,
>> but I presume it will on other hardware with more or different sensors.
>>
>> sensors-detect does not implement any option to probe non-/dev/ports-sensors only, so I guess
>> there is nothing we can do besides a "> /dev/null 2>&1". I will change the collectd initscript
>> to reflect that.
>>
>> Thanks, and best regards,
>> Peter Müller
>>
>>
>>> Hello,
>>>
>>> I don’t know exactly which patch is responsible for this, but /dev/port is no longer accessible by sensors-detect.
>>>
>>> This leads to ugly messages when the system is booting up for the first time. Please see the attached screenshot.
>>>
>>> At least the message needs to be silenced, but you should investigate whether sensors will still work and is able to access readings for its hardware sensors.
>>>
>>>
>>>
>>> -Michael
>>>
>>>> On 19 Mar 2022, at 21:08, Peter Müller <peter.mueller(a)ipfire.org> wrote:
>>>>
>>>> This patchset improves hardening of our Linux kernel configurations for all
>>>> architectures. Most importantly, it features the activation of the "Linux
>>>> Security Module", also known as "kernel lockdown" (a phrase coined before the
>>>> pandemic), or LSM for short.
>>>>
>>>> Being set to "integrity" mode for a start, LSM prevents the kernel from being
>>>> modified by various mechanisms, of which we have some already covered. However,
>>>> it comes as a more holistic approach, which is why enabling it is desirable
>>>> for our userbase.
>>>>
>>>> Most of this patchset is based on recommendations by the "kconfig-hardened-check"
>>>> tool (https://github.com/a13xp0p0v/kconfig-hardened-check/), with some inspiration
>>>> taken directly from KSPP and grsecurity.
>>>>
>>>> Being unable to cross-compile IPFire for non-x86_64-architectures on my own,
>>>> and my VM on the Mustang currently being offline, this patchset does not come
>>>> with aligned kernel rootfiles for other architectures than x86_64. I am sorry
>>>> for any inconvenience and extra workload caused by this.
>>>>
>>>> Also, for the sake of completeness, the effect of LSM on virtualisation has not
>>>> been tested due to time constraints, and a lack of oversight _which_ virtualisation
>>>> features we officially support and which we don't. In doubt, however, I believe
>>>> the security benefit gained from LSM outweighs a partial functional loss of
>>>> virtualisation - but that is a highly biased opinion. :-)
>>>>
>>>> Peter Müller (11):
>>>> Kernel: Set CONFIG_ARCH_MMAP_RND_BITS to 32 bits
>>>> Kernel: Disable support for tracing block I/O actions
>>>> Kernel: Pin loading kernel files to one filesystem
>>>> Kernel: Enable undefined behaviour sanity checker
>>>> Kernel: Gate SETID transitions to limit CAP_SET(G|U)ID capabilities
>>>> Kernel: Enable LSM support and set security level to "integrity"
>>>> Kernel: Trigger BUG if data corruption is detected
>>>> Kernel: Do not automatically load TTY line disciplines, only if
>>>>   necessary
>>>> Kernel: Enable SVA support for both Intel and AMD CPUs
>>>> Kernel: Disable function and stack tracers
>>>> Kernel: Update rootfile for x86_64
>>>>
>>>> config/kernel/kernel.config.aarch64-ipfire | 47 ++++++++++--------
>>>> config/kernel/kernel.config.armv6l-ipfire  | 47 ++++++++++--------
>>>> config/kernel/kernel.config.riscv64-ipfire | 47 ++++++++++--------
>>>> config/kernel/kernel.config.x86_64-ipfire  | 57 ++++++++++++----------
>>>> config/rootfiles/common/x86_64/linux       | 33 +++++++------
>>>> 5 files changed, 131 insertions(+), 100 deletions(-)
>>>>
>>>> -- 
>>>> 2.34.1
>>>
>>>
>