Following kernel's proposal for an arch-agnostic initrd loading mechanism [1] let's implement the U-boot counterpart. This new approach has a number of advantages compared to what we did up to now. The file is loaded into memory only when requested limiting the area of TOCTOU attacks. Users will be allowed to place the initramfs file on any u-boot accessible partition instead of just the ESP one. Finally this is an attempt of a generic interface across architectures in the linux kernel so it makes sense to support that.
The file location is intentionally only supported as a config option argument(CONFIG_EFI_INITRD_FILESPEC), in an effort to enhance security. Although U-boot is not responsible for verifying the integrity of the initramfs, we can enhance the offered security by only accepting a built-in option, which will be naturally verified by UEFI Secure Boot. This can easily change in the future if needed and configure that via ENV or UEFI variable.
[1] https://lore.kernel.org/linux-efi/20200207202637.GA3464906@rani.riverdale.la...
Signed-off-by: Ilias Apalodimas ilias.apalodimas@linaro.org Signed-off-by: Heinrich Schuchardt xypron.glpk@gmx.de --- cmd/efidebug.c | 4 + include/efi_api.h | 17 +++ include/efi_load_initrd.h | 25 ++++ include/efi_loader.h | 1 + lib/efi_loader/Kconfig | 15 +++ lib/efi_loader/Makefile | 1 + lib/efi_loader/efi_load_initrd.c | 198 +++++++++++++++++++++++++++++++ lib/efi_loader/efi_setup.c | 5 + 8 files changed, 266 insertions(+) create mode 100644 include/efi_load_initrd.h create mode 100644 lib/efi_loader/efi_load_initrd.c
diff --git a/cmd/efidebug.c b/cmd/efidebug.c index 576e95b395dc..f450518c9e83 100644 --- a/cmd/efidebug.c +++ b/cmd/efidebug.c @@ -264,6 +264,10 @@ static const struct { "SMBIOS table", SMBIOS_TABLE_GUID, }, + { + "Load File2", + EFI_LOAD_FILE2_PROTOCOL_GUID, + }, };
/** diff --git a/include/efi_api.h b/include/efi_api.h index 22396172e15f..8ffed1334b84 100644 --- a/include/efi_api.h +++ b/include/efi_api.h @@ -319,6 +319,14 @@ struct efi_runtime_services { EFI_GUID(0xeb9d2d31, 0x2d88, 0x11d3, \ 0x9a, 0x16, 0x00, 0x90, 0x27, 0x3f, 0xc1, 0x4d)
+#define EFI_LOAD_FILE_PROTOCOL_GUID \ + EFI_GUID(0x56ec3091, 0x954c, 0x11d2, \ + 0x8e, 0x3f, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b) + +#define EFI_LOAD_FILE2_PROTOCOL_GUID \ + EFI_GUID(0x4006c0c1, 0xfcb3, 0x403e, \ + 0x99, 0x6d, 0x4a, 0x6c, 0x87, 0x24, 0xe0, 0x6d) + struct efi_configuration_table { efi_guid_t guid; void *table; @@ -474,6 +482,7 @@ struct efi_device_path_nvme { #define DEVICE_PATH_TYPE_MEDIA_DEVICE 0x04 # define DEVICE_PATH_SUB_TYPE_HARD_DRIVE_PATH 0x01 # define DEVICE_PATH_SUB_TYPE_CDROM_PATH 0x02 +# define DEVICE_PATH_SUB_TYPE_VENDOR_PATH 0x03 # define DEVICE_PATH_SUB_TYPE_FILE_PATH 0x04
struct efi_device_path_hard_drive_path { @@ -1607,6 +1616,14 @@ struct efi_unicode_collation_protocol { char *supported_languages; };
+struct efi_load_file_protocol { + efi_status_t (EFIAPI *load_file)(struct efi_load_file_protocol *this, + struct efi_device_path *file_path, + bool boot_policy, + efi_uintn_t *buffer_size, + void *buffer); +}; + /* Boot manager load options */ #define LOAD_OPTION_ACTIVE 0x00000001 #define LOAD_OPTION_FORCE_RECONNECT 0x00000002 diff --git a/include/efi_load_initrd.h b/include/efi_load_initrd.h new file mode 100644 index 000000000000..478ae807c685 --- /dev/null +++ b/include/efi_load_initrd.h @@ -0,0 +1,25 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +/* + * Copyright (c) 2020, Linaro Limited + */ + +#if !defined _EFI_LOAD_INITRD_H_ +#define _EFI_LOAD_INITRD_H_ + +#include <efi.h> +#include <efi_api.h> + +/* + * Vendor GUID used by Linux to identify the handle with the + * EFI_LOAD_FILE2_PROTOCOL and load an initial ramdisk. + */ +#define EFI_INITRD_MEDIA_GUID \ + EFI_GUID(0x5568e427, 0x68fc, 0x4f3d, \ + 0xac, 0x74, 0xca, 0x55, 0x52, 0x31, 0xcc, 0x68) + +struct efi_initrd_dp { + struct efi_device_path_vendor vendor; + struct efi_device_path end; +} __packed; + +#endif diff --git a/include/efi_loader.h b/include/efi_loader.h index d4c59b54c48b..8e3437983391 100644 --- a/include/efi_loader.h +++ b/include/efi_loader.h @@ -378,6 +378,7 @@ efi_status_t efi_gop_register(void); efi_status_t efi_net_register(void); /* Called by bootefi to make the watchdog available */ efi_status_t efi_watchdog_register(void); +efi_status_t efi_initrd_register(void); /* Called by bootefi to make SMBIOS tables available */ /** * efi_acpi_register() - write out ACPI tables diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig index a7afa3f29e88..50d4f81e6207 100644 --- a/lib/efi_loader/Kconfig +++ b/lib/efi_loader/Kconfig @@ -130,4 +130,19 @@ config EFI_RNG_PROTOCOL "Support for EFI_RNG_PROTOCOL implementation. Uses the rng device on the platform"
+config EFI_LOAD_FILE2_INITRD + bool "EFI_FILE_LOAD2_PROTOCOL for Linux initial ramdisk" + default n + help + Expose a EFI_FILE_LOAD2_PROTOCOL that the Linux UEFI stub can + use to load the initial ramdisk. Once this is enabled using + initrd=<ramdisk> will stop working. + +config EFI_INITRD_FILESPEC + string "initramfs path" + default "host 0:1 initrd" + depends on EFI_LOAD_FILE2_INITRD + help + Full path of the initramfs file, e.g. mmc 0:2 initramfs.cpio.gz. + endif diff --git a/lib/efi_loader/Makefile b/lib/efi_loader/Makefile index 04dc8648512b..9b3b70447336 100644 --- a/lib/efi_loader/Makefile +++ b/lib/efi_loader/Makefile @@ -43,3 +43,4 @@ obj-$(CONFIG_NET) += efi_net.o obj-$(CONFIG_GENERATE_ACPI_TABLE) += efi_acpi.o obj-$(CONFIG_GENERATE_SMBIOS_TABLE) += efi_smbios.o obj-$(CONFIG_EFI_RNG_PROTOCOL) += efi_rng.o +obj-$(CONFIG_EFI_LOAD_FILE2_INITRD) += efi_load_initrd.o diff --git a/lib/efi_loader/efi_load_initrd.c b/lib/efi_loader/efi_load_initrd.c new file mode 100644 index 000000000000..574a83d7e308 --- /dev/null +++ b/lib/efi_loader/efi_load_initrd.c @@ -0,0 +1,198 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Copyright (c) 2020, Linaro Limited + */ + +#include <common.h> +#include <env.h> +#include <malloc.h> +#include <mapmem.h> +#include <dm.h> +#include <fs.h> +#include <efi_loader.h> +#include <efi_load_initrd.h> + +static const efi_guid_t efi_guid_load_file2_protocol = + EFI_LOAD_FILE2_PROTOCOL_GUID; + +static efi_status_t EFIAPI +efi_load_file2_initrd(struct efi_load_file_protocol *this, + struct efi_device_path *file_path, bool boot_policy, + efi_uintn_t *buffer_size, void *buffer); + +static const struct efi_load_file_protocol efi_lf2_protocol = { + .load_file = efi_load_file2_initrd, +}; + +/* + * Device path defined by Linux to identify the handle providing the + * EFI_LOAD_FILE2_PROTOCOL used for loading the initial ramdisk. + */ +static const struct efi_initrd_dp dp = { + .vendor = { + { + DEVICE_PATH_TYPE_MEDIA_DEVICE, + DEVICE_PATH_SUB_TYPE_VENDOR_PATH, + sizeof(dp.vendor), + }, + EFI_INITRD_MEDIA_GUID, + }, + .end = { + DEVICE_PATH_TYPE_END, + DEVICE_PATH_SUB_TYPE_END, + sizeof(dp.end), + } +}; + +/** + * get_file_size() - retrieve the size of initramfs, set efi status on error + * + * @dev: device to read from. i.e "mmc" + * @part: device partition. i.e "0:1" + * @file: name fo file + * @status: EFI exit code in case of failure + * + * Return: size of file + */ +static loff_t get_file_size(const char *dev, const char *part, const char *file, + efi_status_t *status) +{ + loff_t sz = 0; + int ret; + + ret = fs_set_blk_dev(dev, part, FS_TYPE_ANY); + if (ret) { + *status = EFI_NO_MEDIA; + goto out; + } + + ret = fs_size(file, &sz); + if (ret) { + sz = 0; + *status = EFI_NOT_FOUND; + goto out; + } + +out: + return sz; +} + +/** + * load_file2() - get information about random number generation + * + * This function implement the LoadFile2() service in order to load an initram + * disk requested by the Linux kernel stub. + * See the UEFI spec for details. + * + * @this: loadfile2 protocol instance + * @file_path: relative path of the file. "" in this case + * @boot_policy: must be false for Loadfile2 + * @buffer_size: size of allocated buffer + * @buffer: buffer to load the file + * + * Return: status code + */ +static efi_status_t EFIAPI +efi_load_file2_initrd(struct efi_load_file_protocol *this, + struct efi_device_path *file_path, bool boot_policy, + efi_uintn_t *buffer_size, void *buffer) +{ + const char *filespec = CONFIG_EFI_INITRD_FILESPEC; + efi_status_t status = EFI_NOT_FOUND; + loff_t file_sz = 0, read_sz = 0; + char *dev, *part, *file; + char *s; + int ret; + + EFI_ENTRY("%p, %p, %d, %p, %p", this, file_path, boot_policy, + buffer_size, buffer); + + s = strdup(filespec); + if (!s) + goto out; + + if (!this || this != &efi_lf2_protocol || + !buffer_size) { + status = EFI_INVALID_PARAMETER; + goto out; + } + + if (file_path->type != dp.end.type || + file_path->sub_type != dp.end.sub_type) { + status = EFI_INVALID_PARAMETER; + goto out; + } + + if (boot_policy) { + status = EFI_UNSUPPORTED; + goto out; + } + + /* expect something like 'mmc 0:1 initrd.cpio.gz' */ + dev = strsep(&s, " "); + if (!dev) + goto out; + part = strsep(&s, " "); + if (!part) + goto out; + file = strsep(&s, " "); + if (!file) + goto out; + + file_sz = get_file_size(dev, part, file, &status); + if (!file_sz) + goto out; + + if (!buffer || *buffer_size < file_sz) { + status = EFI_BUFFER_TOO_SMALL; + *buffer_size = file_sz; + } else { + ret = fs_set_blk_dev(dev, part, FS_TYPE_ANY); + if (ret) { + status = EFI_NO_MEDIA; + goto out; + } + + ret = fs_read(file, map_to_sysmem(buffer), 0, *buffer_size, + &read_sz); + if (ret || read_sz != file_sz) + goto out; + *buffer_size = read_sz; + + status = EFI_SUCCESS; + } + +out: + free(s); + return EFI_EXIT(status); +} + +/** + * efi_initrd_register() - Register a handle and loadfile2 protocol + * + * This function creates a new handle and installs a linux specific GUID + * to handle initram disk loading during boot. + * See the UEFI spec for details. + * + * Return: status code + */ +efi_status_t efi_initrd_register(void) +{ + efi_handle_t efi_initrd_handle = NULL; + efi_status_t ret; + + /* + * Set up the handle with the EFI_LOAD_FILE2_PROTOCOL which Linux may + * use to load the initial ramdisk. + */ + ret = EFI_CALL(efi_install_multiple_protocol_interfaces + (&efi_initrd_handle, + /* initramfs */ + &efi_guid_device_path, &dp, + /* LOAD_FILE2 */ + &efi_guid_load_file2_protocol, + (void *)&efi_lf2_protocol, + NULL)); + + return ret; +} diff --git a/lib/efi_loader/efi_setup.c b/lib/efi_loader/efi_setup.c index de7b616c6daa..f03685b11559 100644 --- a/lib/efi_loader/efi_setup.c +++ b/lib/efi_loader/efi_setup.c @@ -155,6 +155,11 @@ efi_status_t efi_init_obj_list(void) if (ret != EFI_SUCCESS) goto out; #endif +#ifdef CONFIG_EFI_LOAD_FILE2_INITRD + ret = efi_initrd_register(); + if (ret != EFI_SUCCESS) + goto out; +#endif #ifdef CONFIG_NET ret = efi_net_register(); if (ret != EFI_SUCCESS)