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Hallyn" , Andi Kleen , "Dr. David Alan Gilbert" , James Bottomley , Tobin Feldman-Fitzthum , Jim Cadden , linux-coco@lists.linux.dev, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/3] efi/libstub: Copy confidential computing secret area Date: Mon, 9 Aug 2021 19:01:55 +0000 Message-Id: <20210809190157.279332-2-dovmurik@linux.ibm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210809190157.279332-1-dovmurik@linux.ibm.com> References: <20210809190157.279332-1-dovmurik@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: d4qlvm2jATro-gsdv75DoPFaV86j-nPb X-Proofpoint-ORIG-GUID: abc141FOsCHp-J3-s_772oha95FxN3nM X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-08-09_07:2021-08-06,2021-08-09 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 mlxlogscore=999 mlxscore=0 clxscore=1011 spamscore=0 priorityscore=1501 suspectscore=0 malwarescore=0 bulkscore=0 adultscore=0 impostorscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2107140000 definitions=main-2108090131 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Confidential computing (coco) hardware such as AMD SEV (Secure Encrypted Virtualization) allows a guest owner to inject secrets into the VMs memory without the host/hypervisor being able to read them. Firmware support for secret injection is available in OVMF, which reserves a memory area for secret injection and includes a pointer to it the in EFI config table entry LINUX_EFI_COCO_SECRET_TABLE_GUID. However, OVMF doesn't force the guest OS to keep this memory area reserved. If EFI exposes such a table entry, efi/libstub will copy this area to a reserved memory for future use inside the kernel. A pointer to the new copy is kept in the EFI table under LINUX_EFI_COCO_SECRET_AREA_GUID. Signed-off-by: Dov Murik --- drivers/firmware/efi/libstub/Makefile | 2 +- drivers/firmware/efi/libstub/coco.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 + include/linux/efi.h | 6 +++ 6 files changed, 81 insertions(+), 1 deletion(-) create mode 100644 drivers/firmware/efi/libstub/coco.c diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index d0537573501e..d77690b7dfb9 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -55,7 +55,7 @@ KCOV_INSTRUMENT := n lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \ file.o mem.o random.o randomalloc.o pci.o \ skip_spaces.o lib-cmdline.o lib-ctype.o \ - alignedmem.o relocate.o vsprintf.o + alignedmem.o relocate.o vsprintf.o coco.o # include the stub's generic dependencies from lib/ when building for ARM/arm64 efi-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c diff --git a/drivers/firmware/efi/libstub/coco.c b/drivers/firmware/efi/libstub/coco.c new file mode 100644 index 000000000000..bf546b6a3f72 --- /dev/null +++ b/drivers/firmware/efi/libstub/coco.c @@ -0,0 +1,68 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Confidential computing (coco) secret area handling + * + * Copyright (C) 2021 IBM Corporation + * Author: Dov Murik + */ + +#include +#include +#include + +#include "efistub.h" + +#define LINUX_EFI_COCO_SECRET_TABLE_GUID \ + EFI_GUID(0xadf956ad, 0xe98c, 0x484c, 0xae, 0x11, 0xb5, 0x1c, 0x7d, 0x33, 0x64, 0x47) + +/** + * struct efi_coco_secret_table - EFI config table that points to the + * confidential computing secret area. The guid + * LINUX_EFI_COCO_SECRET_TABLE_GUID holds this table. + * @base: Physical address of the EFI secret area + * @size: Size (in bytes) of the EFI secret area + */ +struct efi_coco_secret_table { + u64 base; + u64 size; +} __attribute((packed)); + +/* + * Create a copy of EFI's confidential computing secret area (if available) so + * that the secrets are accessible in the kernel after ExitBootServices. + */ +void efi_copy_coco_secret_area(void) +{ + efi_guid_t linux_secret_area_guid = LINUX_EFI_COCO_SECRET_AREA_GUID; + efi_status_t status; + struct efi_coco_secret_table *secret_table; + struct linux_efi_coco_secret_area *secret_area; + + secret_table = get_efi_config_table(LINUX_EFI_COCO_SECRET_TABLE_GUID); + if (!secret_table) + return; + + if (secret_table->size == 0 || secret_table->size >= SZ_4G) + return; + + /* Allocate space for the secret area and copy it */ + status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, + sizeof(*secret_area) + secret_table->size, (void **)&secret_area); + + if (status != EFI_SUCCESS) { + efi_err("Unable to allocate memory for confidential computing secret area copy\n"); + return; + } + + secret_area->size = secret_table->size; + memcpy(secret_area->area, (void *)(unsigned long)secret_table->base, secret_table->size); + + status = efi_bs_call(install_configuration_table, &linux_secret_area_guid, secret_area); + if (status != EFI_SUCCESS) + goto err_free; + + return; + +err_free: + efi_bs_call(free_pool, secret_area); +} diff --git a/drivers/firmware/efi/libstub/efi-stub.c b/drivers/firmware/efi/libstub/efi-stub.c index 26e69788f27a..18b3acd15c85 100644 --- a/drivers/firmware/efi/libstub/efi-stub.c +++ b/drivers/firmware/efi/libstub/efi-stub.c @@ -205,6 +205,8 @@ efi_status_t __efiapi efi_pe_entry(efi_handle_t handle, efi_retrieve_tpm2_eventlog(); + efi_copy_coco_secret_area(); + /* Ask the firmware to clear memory on unclean shutdown */ efi_enable_reset_attack_mitigation(); diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h index cde0a2ef507d..d604c6744cef 100644 --- a/drivers/firmware/efi/libstub/efistub.h +++ b/drivers/firmware/efi/libstub/efistub.h @@ -858,4 +858,6 @@ efi_enable_reset_attack_mitigation(void) { } void efi_retrieve_tpm2_eventlog(void); +void efi_copy_coco_secret_area(void); + #endif diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c index f14c4ff5839f..4ad85e1b6191 100644 --- a/drivers/firmware/efi/libstub/x86-stub.c +++ b/drivers/firmware/efi/libstub/x86-stub.c @@ -793,6 +793,8 @@ unsigned long efi_main(efi_handle_t handle, efi_retrieve_tpm2_eventlog(); + efi_copy_coco_secret_area(); + setup_graphics(boot_params); setup_efi_pci(boot_params); diff --git a/include/linux/efi.h b/include/linux/efi.h index 6b5d36babfcc..9021dd521302 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -359,6 +359,7 @@ void efi_native_runtime_setup(void); #define LINUX_EFI_MEMRESERVE_TABLE_GUID EFI_GUID(0x888eb0c6, 0x8ede, 0x4ff5, 0xa8, 0xf0, 0x9a, 0xee, 0x5c, 0xb9, 0x77, 0xc2) #define LINUX_EFI_INITRD_MEDIA_GUID EFI_GUID(0x5568e427, 0x68fc, 0x4f3d, 0xac, 0x74, 0xca, 0x55, 0x52, 0x31, 0xcc, 0x68) #define LINUX_EFI_MOK_VARIABLE_TABLE_GUID EFI_GUID(0xc451ed2b, 0x9694, 0x45d3, 0xba, 0xba, 0xed, 0x9f, 0x89, 0x88, 0xa3, 0x89) +#define LINUX_EFI_COCO_SECRET_AREA_GUID EFI_GUID(0x940ed1e9, 0xd3da, 0x408b, 0xb3, 0x07, 0xe3, 0x2d, 0x25, 0x4a, 0x65, 0x16) /* OEM GUIDs */ #define DELLEMC_EFI_RCI2_TABLE_GUID EFI_GUID(0x2d9f28a2, 0xa886, 0x456a, 0x97, 0xa8, 0xf1, 0x1e, 0xf2, 0x4f, 0xf4, 0x55) @@ -1282,4 +1283,9 @@ static inline struct efi_mokvar_table_entry *efi_mokvar_entry_find( } #endif +struct linux_efi_coco_secret_area { + u32 size; + u8 area[]; +}; + #endif /* _LINUX_EFI_H */ -- 2.25.1