* Brijesh Singh (brijesh.singh@xxxxxxx) wrote: > Hi Dov, > > > On 5/13/21 1:26 AM, Dov Murik wrote: > > Confidential computing hardware such as AMD SEV (Secure Encrypted > > Virtualization) allows guest owners to inject secrets into the VMs > > memory without the host/hypervisor being able to read them. In SEV, > > secret injection is performed early in the VM launch process, before the > > guest starts running. > > > > Support for secret injection is already available in OVMF (in its AmdSev > > package; see edk2 commit 01726b6d23d4 "OvmfPkg/AmdSev: Expose the Sev > > Secret area using a configuration table" [1]), but the secrets were not > > available in the guest kernel. > > > > The patch series copies the secrets from the EFI-provided memory to > > kernel reserved memory, and optionally exposes them to userspace via > > securityfs using a new sev_secret kernel module. > > > > The first patch in efi/libstub copies the secret area from the EFI > > memory to specially allocated memory; the second patch reserves that > > memory block; and the third patch introduces the new sev_secret module > > that exposes the content of the secret entries as securityfs files. > > > > This has been tested with AMD SEV guests, but the kernel side of > > handling the secret area has no SEV-specific dependencies, and therefore > > should be usable for any confidential computing hardware that can > > publish the secret area via the standard EFI config table entry. > > > > Here is a simple example for usage of the sev_secret module in a guest to which > > secrets were injected during launch: > > > > # modprobe sev_secret > > # ls -la /sys/kernel/security/sev_secret > > total 0 > > drwxr-xr-x 2 root root 0 May 12 18:03 . > > drwxr-xr-x 3 root root 0 May 12 18:02 .. > > -r--r----- 1 root root 0 May 12 18:03 736870e5-84f0-4973-92ec-06879ce3da0b > > -r--r----- 1 root root 0 May 12 18:03 83c83f7f-1356-4975-8b7e-d3a0b54312c6 > > -r--r----- 1 root root 0 May 12 18:03 9553f55d-3da2-43ee-ab5d-ff17f78864d2 > > -r--r----- 1 root root 0 May 12 18:03 e6f5a162-d67f-4750-a67c-5d065f2a9910 > > > > # xxd /sys/kernel/security/sev_secret/e6f5a162-d67f-4750-a67c-5d065f2a9910 > > 00000000: 7468 6573 652d 6172 652d 7468 652d 6b61 these-are-the-ka > > 00000010: 7461 2d73 6563 7265 7473 0001 0203 0405 ta-secrets...... > > 00000020: 0607 .. > > I am adding a new virt driver to help get the attestation report for the > SEV-SNP guest. I understand they both are different, in case of the SEV > the attestation is already completed and we are simply exposing the > secret provided after the attestation to the userspace, whereas in SNP, > the userspace is querying the attestation and will probably derive keys > etc based on the attestation report. I am wondering if we should merge > both the SEV secret and SNP attestation query in a single driver ? > Should we cover usecases where SEV guest is not booted under the EFI ? > Also, it appears that this driver need to be manually loaded, should we > create a platform device so that the driver binds to platform device and > use the resource structure to find the location of the secret data? The nice thing about Dov's device/file is that it's a simple text file that userspace can then read the secret out of; I'm not sure if there's anything similar in SNP (or for that matter TDX, cc'ing in Andi) Dave > I was trying to answer some of these questions SNP series. See these patches > > https://marc.info/?l=kvm&m=161978514019741&w=2 > > https://marc.info/?l=kvm&m=161978514119744&w=2 > > https://marc.info/?l=kvm&m=161978514219751&w=2 > > > > > > [1] https://github.com/tianocore/edk2/commit/01726b6d23d4 > > > > > > Cc: Laszlo Ersek <lersek@xxxxxxxxxx> > > Cc: Ashish Kalra <ashish.kalra@xxxxxxx> > > Cc: Brijesh Singh <brijesh.singh@xxxxxxx> > > Cc: Tom Lendacky <thomas.lendacky@xxxxxxx> > > Cc: James Bottomley <jejb@xxxxxxxxxxxxx> > > Cc: Ard Biesheuvel <ardb@xxxxxxxxxx> > > Cc: James Morris <jmorris@xxxxxxxxx> > > Cc: "Serge E. Hallyn" <serge@xxxxxxxxxx> > > Cc: linux-efi@xxxxxxxxxxxxxxx > > Cc: linux-security-module@xxxxxxxxxxxxxxx > > Cc: linux-kernel@xxxxxxxxxxxxxxx > > > > Dov Murik (3): > > efi/libstub: Copy confidential computing secret area > > efi: Reserve confidential computing secret area > > virt: Add sev_secret module to expose confidential computing secrets > > > > drivers/firmware/efi/Makefile | 2 +- > > drivers/firmware/efi/confidential-computing.c | 41 +++ > > drivers/firmware/efi/efi.c | 5 + > > drivers/firmware/efi/libstub/Makefile | 3 +- > > .../efi/libstub/confidential-computing.c | 68 +++++ > > drivers/firmware/efi/libstub/efi-stub.c | 2 + > > drivers/firmware/efi/libstub/efistub.h | 2 + > > drivers/firmware/efi/libstub/x86-stub.c | 2 + > > drivers/virt/Kconfig | 2 + > > drivers/virt/Makefile | 1 + > > drivers/virt/sev_secret/Kconfig | 11 + > > drivers/virt/sev_secret/Makefile | 2 + > > drivers/virt/sev_secret/sev_secret.c | 260 ++++++++++++++++++ > > include/linux/efi.h | 11 + > > 14 files changed, 410 insertions(+), 2 deletions(-) > > create mode 100644 drivers/firmware/efi/confidential-computing.c > > create mode 100644 drivers/firmware/efi/libstub/confidential-computing.c > > create mode 100644 drivers/virt/sev_secret/Kconfig > > create mode 100644 drivers/virt/sev_secret/Makefile > > create mode 100644 drivers/virt/sev_secret/sev_secret.c > > > > > > base-commit: c06a2ba62fc401b7aaefd23f5d0bc06d2457ccc1 -- Dr. David Alan Gilbert / dgilbert@xxxxxxxxxx / Manchester, UK
