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 .. [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 -- 2.25.1
