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Re: -enablefips
From: |
Markus Armbruster |
Subject: |
Re: -enablefips |
Date: |
Wed, 24 Jun 2020 10:34:03 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) |
Gerd Hoffmann <kraxel@redhat.com> writes:
> On Tue, Jun 23, 2020 at 11:51:09PM -0400, John Snow wrote:
>> I never knew what this option did, but the answer is ... strange!
>>
>> It's only defined for linux, in os-posix.c. When called, it calls
>> fips_set_state(true), located in osdep.c.
>>
>> This will read /proc/sys/crypto/fips_enabled and set the static global
>> 'fips_enabled' to true if this setting is on.
>
> IIRC the idea is to have a global switch to enable fips compilance for
> the whole distro. RH specific. rhel-7 kernel has it. rhel-8 kernel
> too, so it probably isn't obsolete. Not present in mainline kernels.
>
> I'm wondering what the point of the -enablefips switch is. Shouldn't
> qemu check /proc/sys/crypto/fips_enabled unconditionally instead?
The switch feels rather silly to me. If you take the trouble to put
your host in FIPS mode, requiring -enable-fips to make QEMU to actually
honor it makes no sense. If you don't, QEMU's -enable-fips has no
effect.
I may well misremember things (it's been years), but I vaguely recall
-enable-fips being a lame compromise between "this ought to be upstream"
and "FIPS is stupid, and I want nothing of it".
>> (Tangent: what does *this* setting actually control? Should QEMU
>> meaningfully change its behavior when it's set?)
>
> fips is a security policy ...
>
>> This static global is exposed via the getter fips_get_state(). This
>> function is called only by vnc.c, and appears to disable the use of the
>> password option for -vnc.
>
> ... yes, "no passwords" is one of the rules. There are probably more.
>
>> (If we really do want to keep it, it should probably go under -global
>> somewhere instead to help reduce flag clutter, but we'd need to have a
>> chat about what fips compliance means for literally every other spot in
>> QEMU that is capable of using or receiving a cleartext password.)
>
> Yep. IIRC for spice this is handled in libspice-server. We need to
> look at blockdev encryption I guess. Any other places where qemu uses
> passwords directly? I think we don't have to worry about indirect usage
> (sasl).
I'd expect the SASL libraries to honor FIPS mode by themselves. But
best ask someone who actually knows how FIPS mode is supposed to work.