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

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

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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
> 
>