On Thu, Oct 28, 2021 at 01:51:33PM -0400, Stefan Berger wrote: > > On 10/28/21 07:04, Daniel P. Berrangé wrote: > > On Wed, Oct 27, 2021 at 05:48:19PM -0400, Stefan Berger wrote: > > > On 10/27/21 14:17, Marc-André Lureau wrote: > > > > Hi > > > > > > > > On Wed, Oct 27, 2021 at 9:00 PM Stefan Berger <stefanb@xxxxxxxxxxxxx> wrote: > > > > > Extend qemu.conf with a configration option swtpm_active_pcr_banks that > > > > > allows a user to set a comma-separated list of PCR banks to activate > > > > > during 'TPM manufacturing'. Valid PCR banks are sha1,sha256,sha384 and > > > > > sha512. > > > > > > > > > Why not put this option in swtpm_setup.conf instead? > > > That is another option but it depends on when one wants to see the effect or > > > how one wants to control it. With newer libvirt or newer swtpm? > > The obvious reason for putting it in swtpm_setup.conf is that it also > > benefits people using swtpm in a non-libvirt scenario. > > > > IMHO, we should put it in swtpm_setup.conf, and *also* have a build > > time option in swtpm to configure the built-in default. > > > > IOW, I'd expect RHEL-9 RPM swtpm.spec to pass > > > > %configure --default-pcr-banks=sha256 > > > > and then have the swtpm_setup.conf option to allow admins to override > > the distro default if they need a weaker setup on a host. > > I now have a pending PR to swtpm that does this modulo using > --enable-default-pcr-banks=sha256. The selection of the PCR banks to > activate can then be done via swtpm_setup.conf active_pcr_banks = <list of > PCR banks> entry, if provided, otherwise it's back to the configure line > default. > > https://github.com/stefanberger/swtpm/pull/615 Great, that looks good. > > On the libvirt side, I think we could have a domain XML config option > > for PCR banks, to allow the built-in default or admin local default to > > be override per-VM. > > Is there an example of an attribute that can only be set once in the domain > XML and cannot be modified after? The choice of active PCR banks is limited > to 'TPM manufacturing' time, which means swtpm_setup runs once only when the > swtpm's state directory does not exist because later it would overwrite the > entire state and erase all keys etc.. Later manipulations of the PCR banks > would have to be done using the firmware menu, which exist in EDK2, SeaBIOS > and SLOF. Yeah, it is a little unusual, but then I guess we have the similarish with other firmware selection, where setting "secure=yes|no" determines which OVMF binary we pick to use. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
