Re: [PATCH] os: deprecate the -enable-fips option and QEMU's FIPS enforcement

[Daniel P . Berrangé]

On Wed, Oct 21, 2020 at 11:51:10AM +0200, Paolo Bonzini wrote:
> On 21/10/20 10:38, Daniel P. Berrangé wrote:
> > On Tue, Oct 20, 2020 at 07:22:03PM +0200, Paolo Bonzini wrote:
> >> On 20/10/20 18:22, Daniel P. Berrangé wrote:
> >>> @@ -153,6 +153,9 @@ int os_parse_cmd_args(int index, const char *optarg)
> >>>          break;
> >>>  #if defined(CONFIG_LINUX)
> >>>      case QEMU_OPTION_enablefips:
> >>> +        warn_report("-enable-fips is deprecated, please build QEMU with "
> >>> +                    "the `libgcrypt` library as the cryptography 
> >>> provider "
> >>> +                    "to enable FIPS compliance");
> >>>          fips_set_state(true);
> >>>          break;
> >>>  #endif
> >>
> >> Should you also remove fips_set_state(true) and make fips_get_state()
> >> return the contents of /proc/sys/crypto/fips_enabled, so that VNC
> >> password authentication is disabled?
> > 
> > I did think about doing that, but decided that since my intention is
> > to delete all trace of fips_get_state / fips_set_state at the end of
> > the deprecation period, that it'd be saner just to leave the semantics
> > unchanged during the deprecation period.
> 
> But would it be correct?  In order to have the advertised behavior of
> "enable FIPS compliance just with procfs, no need to do anything in
> QEMU" you need to disable VNC password authentication; so while
> fips_set_state is an abomination, fips_get_state should remain.

There's no need for fips_get_state. Once you build QEMU with
libgcrypt, when  VNC requests a DES cipher handle, gcrypt will
return an error as that algorithm is forbidden in FIPS mode.

This is the primary reason for outsourcing all crypto to a
separate library and ignoring the impls in QEMU.

Claiming QEMU is FIPS compliant without using libgcrypt is a
bit of joke since we don't do any self-tests of ciphers, hence
this deprecation notice is warning people that libgcrypt is
going to be mandatory if you care about FIPS.


> > Deprecation notices shouldn't really be associated with changes in
> > functionality at time they are introduced.
> 
> I think you can consider it a bugfix since no one sets fips_enabled
> without knowing what they're doing.

I just would rather not change semantics of something that we are
intending to remove 

Regards,
Daniel
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