[PATCH 1/3 v2] efi_capsule: Move signature from DTB to .rodata
Simon Glass
sjg at chromium.org
Tue Jul 20 14:33:19 CEST 2021
Hi Ilias,
On Sat, 17 Jul 2021 at 08:27, Ilias Apalodimas
<ilias.apalodimas at linaro.org> wrote:
>
> The capsule signature is now part of our DTB. This is problematic when a
> user is allowed to change/fixup that DTB from U-Boots command line since he
> can overwrite the signature as well.
Just to repeat my question since it looks like I didn't get a response
on the last patch:
Do you mean with the 'fdt' command?
>
If you mean the FDT fixups, they happen to a different DT, the one
being passed to Linux.
> So Instead of adding the key on the DTB, embed it in the u-boot binary it
> self as part of it's .rodata. This assumes that the U-Boot binary we load
> is authenticated by a previous boot stage loader.
As I mentioned, this means you need to build U-Boot from source and
include the key. I don't think that is a good idea at all. Signing
should be a separate step from building.
- Simon
>
> Reviewed-by: Masami Hiramatsu <masami.hiramatsu at linaro.org>
> Tested-by: Masami Hiramatsu <masami.hiramatsu at linaro.org>
> Tested-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> ---
> changes since v1:
> - added static keyword on efi_get_public_key_data()
> - added missing config.h on efi_capsule_key.S
>
> board/emulation/common/Makefile | 1 -
> board/emulation/common/qemu_capsule.c | 43 ---------------------------
> include/asm-generic/sections.h | 2 ++
> lib/efi_loader/Kconfig | 7 +++++
> lib/efi_loader/Makefile | 8 +++++
> lib/efi_loader/efi_capsule.c | 18 +++++++++--
> lib/efi_loader/efi_capsule_key.S | 17 +++++++++++
> 7 files changed, 49 insertions(+), 47 deletions(-)
> delete mode 100644 board/emulation/common/qemu_capsule.c
> create mode 100644 lib/efi_loader/efi_capsule_key.S
>
> diff --git a/board/emulation/common/Makefile b/board/emulation/common/Makefile
> index 7ed447a69dce..c5b452e7e341 100644
> --- a/board/emulation/common/Makefile
> +++ b/board/emulation/common/Makefile
> @@ -2,4 +2,3 @@
>
> obj-$(CONFIG_SYS_MTDPARTS_RUNTIME) += qemu_mtdparts.o
> obj-$(CONFIG_SET_DFU_ALT_INFO) += qemu_dfu.o
> -obj-$(CONFIG_EFI_CAPSULE_FIRMWARE_MANAGEMENT) += qemu_capsule.o
> diff --git a/board/emulation/common/qemu_capsule.c b/board/emulation/common/qemu_capsule.c
> deleted file mode 100644
> index 6b8a87022a4c..000000000000
> --- a/board/emulation/common/qemu_capsule.c
> +++ /dev/null
> @@ -1,43 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0+
> -/*
> - * Copyright (c) 2020 Linaro Limited
> - */
> -
> -#include <common.h>
> -#include <efi_api.h>
> -#include <efi_loader.h>
> -#include <env.h>
> -#include <fdtdec.h>
> -#include <asm/global_data.h>
> -
> -DECLARE_GLOBAL_DATA_PTR;
> -
> -int efi_get_public_key_data(void **pkey, efi_uintn_t *pkey_len)
> -{
> - const void *fdt_blob = gd->fdt_blob;
> - const void *blob;
> - const char *cnode_name = "capsule-key";
> - const char *snode_name = "signature";
> - int sig_node;
> - int len;
> -
> - sig_node = fdt_subnode_offset(fdt_blob, 0, snode_name);
> - if (sig_node < 0) {
> - EFI_PRINT("Unable to get signature node offset\n");
> - return -FDT_ERR_NOTFOUND;
> - }
> -
> - blob = fdt_getprop(fdt_blob, sig_node, cnode_name, &len);
> -
> - if (!blob || len < 0) {
> - EFI_PRINT("Unable to get capsule-key value\n");
> - *pkey = NULL;
> - *pkey_len = 0;
> - return -FDT_ERR_NOTFOUND;
> - }
> -
> - *pkey = (void *)blob;
> - *pkey_len = len;
> -
> - return 0;
> -}
> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index 267f1db73f23..ec992b0c2e3f 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -27,6 +27,8 @@ extern char __efi_helloworld_begin[];
> extern char __efi_helloworld_end[];
> extern char __efi_var_file_begin[];
> extern char __efi_var_file_end[];
> +extern char __efi_capsule_sig_begin[];
> +extern char __efi_capsule_sig_end[];
>
> /* Private data used by of-platdata devices/uclasses */
> extern char __priv_data_start[], __priv_data_end[];
> diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
> index 156b39152112..cf6ff2d537f4 100644
> --- a/lib/efi_loader/Kconfig
> +++ b/lib/efi_loader/Kconfig
> @@ -213,6 +213,13 @@ config EFI_CAPSULE_AUTHENTICATE
> Select this option if you want to enable capsule
> authentication
>
> +config EFI_CAPSULE_KEY_PATH
> + string "Path to .esl cert for capsule authentication"
> + depends on EFI_CAPSULE_AUTHENTICATE
> + help
> + Provide the EFI signature list (esl) certificate used for capsule
> + authentication
> +
> config EFI_DEVICE_PATH_TO_TEXT
> bool "Device path to text protocol"
> default y
> diff --git a/lib/efi_loader/Makefile b/lib/efi_loader/Makefile
> index fd344cea29b0..9b369430e258 100644
> --- a/lib/efi_loader/Makefile
> +++ b/lib/efi_loader/Makefile
> @@ -20,11 +20,19 @@ always += helloworld.efi
> targets += helloworld.o
> endif
>
> +ifeq ($(CONFIG_EFI_CAPSULE_AUTHENTICATE),y)
> +EFI_CAPSULE_KEY_PATH := $(subst $\",,$(CONFIG_EFI_CAPSULE_KEY_PATH))
> +ifeq ("$(wildcard $(EFI_CAPSULE_KEY_PATH))","")
> +$(error .esl cerificate not found. Configure your CONFIG_EFI_CAPSULE_KEY_PATH)
> +endif
> +endif
> +
> obj-$(CONFIG_CMD_BOOTEFI_HELLO) += helloworld_efi.o
> obj-$(CONFIG_CMD_BOOTEFI_BOOTMGR) += efi_bootmgr.o
> obj-y += efi_boottime.o
> obj-y += efi_helper.o
> obj-$(CONFIG_EFI_HAVE_CAPSULE_SUPPORT) += efi_capsule.o
> +obj-$(CONFIG_EFI_CAPSULE_AUTHENTICATE) += efi_capsule_key.o
> obj-$(CONFIG_EFI_CAPSULE_FIRMWARE) += efi_firmware.o
> obj-y += efi_console.o
> obj-y += efi_device_path.o
> diff --git a/lib/efi_loader/efi_capsule.c b/lib/efi_loader/efi_capsule.c
> index b878e71438b8..1900a938c140 100644
> --- a/lib/efi_loader/efi_capsule.c
> +++ b/lib/efi_loader/efi_capsule.c
> @@ -16,6 +16,7 @@
> #include <mapmem.h>
> #include <sort.h>
>
> +#include <asm/sections.h>
> #include <crypto/pkcs7.h>
> #include <crypto/pkcs7_parser.h>
> #include <linux/err.h>
> @@ -222,12 +223,23 @@ skip:
> const efi_guid_t efi_guid_capsule_root_cert_guid =
> EFI_FIRMWARE_MANAGEMENT_CAPSULE_ID_GUID;
>
> +static int efi_get_public_key_data(void **pkey, efi_uintn_t *pkey_len)
> +{
> + const void *blob = __efi_capsule_sig_begin;
> + const int len = __efi_capsule_sig_end - __efi_capsule_sig_begin;
> +
> + *pkey = (void *)blob;
> + *pkey_len = len;
> +
> + return 0;
> +}
> +
> efi_status_t efi_capsule_authenticate(const void *capsule, efi_uintn_t capsule_size,
> void **image, efi_uintn_t *image_size)
> {
> u8 *buf;
> int ret;
> - void *fdt_pkey, *pkey;
> + void *stored_pkey, *pkey;
> efi_uintn_t pkey_len;
> uint64_t monotonic_count;
> struct efi_signature_store *truststore;
> @@ -286,7 +298,7 @@ efi_status_t efi_capsule_authenticate(const void *capsule, efi_uintn_t capsule_s
> goto out;
> }
>
> - ret = efi_get_public_key_data(&fdt_pkey, &pkey_len);
> + ret = efi_get_public_key_data(&stored_pkey, &pkey_len);
> if (ret < 0)
> goto out;
>
> @@ -294,7 +306,7 @@ efi_status_t efi_capsule_authenticate(const void *capsule, efi_uintn_t capsule_s
> if (!pkey)
> goto out;
>
> - memcpy(pkey, fdt_pkey, pkey_len);
> + memcpy(pkey, stored_pkey, pkey_len);
> truststore = efi_build_signature_store(pkey, pkey_len);
> if (!truststore)
> goto out;
> diff --git a/lib/efi_loader/efi_capsule_key.S b/lib/efi_loader/efi_capsule_key.S
> new file mode 100644
> index 000000000000..58f00b8e4bcb
> --- /dev/null
> +++ b/lib/efi_loader/efi_capsule_key.S
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +/*
> + * .esl cert for capsule authentication
> + *
> + * Copyright (c) 2021, Ilias Apalodimas <ilias.apalodimas at linaro.org>
> + */
> +
> +#include <config.h>
> +
> +.section .rodata.capsule_key.init,"a"
> +.balign 16
> +.global __efi_capsule_sig_begin
> +__efi_capsule_sig_begin:
> +.incbin CONFIG_EFI_CAPSULE_KEY_PATH
> +__efi_capsule_sig_end:
> +.global __efi_capsule_sig_end
> +.balign 16
> --
> 2.31.1
>
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