Hi Jan On Tue, 9 Nov 2021 at 13:58, Jan Kiszka <[email protected]> wrote:
> On 09.11.21 13:43, François Ozog wrote: > > Hi > > > > as we are in design discussions, I would promote the idea of not pushing > > non hardware related things in the DTB that is passed to the kernel. > > This was never proposed. The public keys go into the *control* FDTs. > > great ;-) > > Is your use case to allow U-Boot to verify the kernel's signature ? > > Why not putting it into an environment variable? > > This is both about validating OS FIT containers as well as SPL checking > U-Boot proper before continuing the boot there. The former case can be > replaced with UEFI logic and likely taking the key from TEE (we do that > as well in first prototypes), but the latter can't (yet). > > > > > If your use case is on Arm or RISC-V, both environments are working > > heavily to make https://arm-software.github.io/ebbr/ > > <https://arm-software.github.io/ebbr/> standard available on a large > > number of boards. > > This offers UEFI interface and SecureBoot (and later MeasuredBoot) > > services. For Arm boards just check for SystemReady compliance. > > In this context, traditional UEFI secure variables are used to deal with > > certificates and hashes: PK, KEK, db... > > You can obviously do differently but you will be on your own to extend > > the chain of trust to IMA, secure containers (rooted down to hRoT) and > > other security facilities in the Linux side. > > Could you describe your use case in more details? > > doc/uImage.FIT/signature.txt ;) > > More concrete: We are currently massaging board/siemens/iot2050 to close > its static chain of trust between SPL and U-Boot main, using software > means (vendor means do not work because FSBL key != TF-A/TEE/U-Boot key). > > And will the chain of trust be continuous or with a very brief breakage with this approach? I other words, can you enroll the TF-A/TEE/U-Boot key so that it can be trusted by FSBL key? Jan > > > > > On Tue, 9 Nov 2021 at 11:07, Jan Kiszka <[email protected] > > <mailto:[email protected]>> wrote: > > > > On 09.11.21 10:37, Roman Kopytin wrote: > > > Can we have discussion with code lines? For me it is not very > > clear, because it isn't my code. > > > > > > > Please do not top-post. > > > > > -----Original Message----- > > > From: Jan Kiszka <[email protected] > > <mailto:[email protected]>> > > > Sent: Tuesday, November 9, 2021 12:17 PM > > > To: Roman Kopytin <[email protected] > > <mailto:[email protected]>>; [email protected] > > <mailto:[email protected]>; Rasmus Villemoes > > <[email protected] <mailto:[email protected]>> > > > Subject: Re: [PATCH 0/2] RFC: add fdt_add_pubkey tool > > > > > > On 08.11.21 16:28, Roman Kopytin wrote: > > >> In order to reduce the coupling between building the kernel and > > >> U-Boot, I'd like a tool that can add a public key to U-Boot's dtb > > >> without simultaneously signing a FIT image. That tool doesn't > > seem to > > >> exist, so I stole the necessary pieces from mkimage et al and put > it > > >> in a single .c file. > > >> > > >> I'm still working on the details of my proposed "require just k > out > > >> these n required keys" and how it should be implemented, but it > will > > >> probably involve teaching this tool a bunch of new options. These > > >> patches are not necessarily ready for inclusion (unless someone > else > > >> finds fdt_add_pubkey useful as is), but I thought I might as well > > send > > >> it out for early comments. > > > > > > I'd also like to see the usage of this hooked into the build > process. > > > > > > And to my understanding of [1], that approach will provide a > > feature that permits hooking with the build but would expect the key > > as dtsi fragment. Can we consolidate the approaches? > > > > > > My current vision of a user interface would be a Kconfig option > > that takes a list of key files to be injected. Maybe make that three > > lists, one for "required=image", one for "required=conf", and one > > for optional keys (if that has a use case in practice, no idea). > > > > > > Jan > > > > > > [1] > > > > > > https://lore.kernel.org/u-boot/[email protected]/ > > < > https://lore.kernel.org/u-boot/[email protected]/ > > > > > > > > -- > > > Siemens AG, T RDA IOT > > > Corporate Competence Center Embedded Linux > > > > > > > For what would you like to have code? The kconfig addition? > > > > diff --git a/common/Kconfig.boot b/common/Kconfig.boot > > index d3a12be228..a9ed4d4ec4 100644 > > --- a/common/Kconfig.boot > > +++ b/common/Kconfig.boot > > @@ -279,6 +279,14 @@ config SPL_FIT_GENERATOR > > > > endif # SPL > > > > +config FIT_SIGNATURE_PUB_KEYS > > + string "Public keys to use for FIT image verification" > > + depends on FIT_SIGNATURE || SPL_FIT_SIGNATURE > > + help > > + Public keys, or certificate files to extract them from, > > that shall > > + be used to verify signed FIT images. The keys will be > > embedded into > > + the control device tree of U-Boot. > > + > > endif # FIT > > > > config LEGACY_IMAGE_FORMAT > > > > > > But note that we are in a design discussion here, and I'm at least > > reluctant to code up n-versions without having some common idea where > > things should move. > > > > Jan > > > > -- > > Siemens AG, T RDA IOT > > Corporate Competence Center Embedded Linux > > > > > > > > -- > > > > François-Frédéric Ozog | /Director Business Development/ > > T: +33.67221.6485 > > [email protected] <mailto:[email protected] > > | Skype: ffozog > > > > > > -- > Siemens AG, T RDA IOT > Corporate Competence Center Embedded Linux > -- François-Frédéric Ozog | *Director Business Development* T: +33.67221.6485 [email protected] | Skype: ffozog
