On 10:29-20231005, Manorit Chawdhry wrote: > Hi Nishanth, > > On 07:24-20231004, Nishanth Menon wrote: > > On 10:43-20231004, Manorit Chawdhry wrote: > > > > > These are required to remove the firewall configurations that are done > > > by ROM, those are not the ones that are being handled by OIDs. The > > > > I am not sure I understand this clearly. OIDs are setup to open up > > firewalls or close firewalls as the system requires and since it > > is authenticated, not compromiseable.- U-boot by itself (even if > > authenticated), is not a secure entity for it to dictate the firewall > > configuration (u-boot must be assumed to be compromised after > > authentication is complete). So, doing firewall configuration via APIs > > after boot, to me looks broken approach. > > > > I know U-boot ain't that secure given the most trusted entity is always > gonna be the software that starts up the system, we can't expect those > to be doing all the work and based on that we have the secure boot > designed to configure firewalls (that are not owned by anymore) and > U-boot R5 being one of the early bootloaders do come as a part of it. > > Regarding the OIDs thing, I don't think the OID in question is looked by > ROM and ROM always configures some firewalls for it's usecase that are > present in those arrays. > > The OID that we are using in the series that you had shared is looked by > TIFS instead of ROM and TIFS is the entity that is authenticating the > binary along with setting up the firewalls. > > > > current series that is being worked on is to add additional firewalling > > > support with OIDs that TIFS will be handling. > > > The above patch is > > > essentially added to have the same development experience on GP devices > > > similar to HS after the secure boot is done so that people don't end up > > > > huh? the code seems to blindly call the > > remove_fwl_configs(cbass_hc_cfg0_fwls, ARRAY_SIZE(cbass_hc_cfg0_fwls)); > > where is the distinction of HS vs GP here? This implementation looks > > completely broken to me at least.. please correct what I missed here. > > Since this call is used across all SoCs there wasn't any point to make > the differentiation between GP and HS here, remove_fwl_configs > internally handles looking at the firewalls and disabling them if they > are enabled ( Which would be only in the case of HS devices ), for GP it > would automatically by a noop.
Correct me if I understand the security chain here: ROM sets up firewalls that are needed by itself TIFS (in multicertificate will setup it's own firewalls) R5 SPL comes along and opens up other firewalls Each stage beyond this: such as tispl.bin containing TFA/OPTEE uses OIDs to set up firewalls to protect themselves (enforced by TIFS) A53 SPL and U-boot itself startups but has no ability to change the protection firewalls enforced by x509 OIDs. Further, firewalls have lockdown bit that enforces the setting (and cannot be over-ridden) till system restart is requested Is this correct? If so, needs to be clearly documented. -- Regards, Nishanth Menon Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3 1A34 DDB5 849D 1736 249D
