[PATCH v6 4/6] bootm: Support boot measurement

Simon Glass sjg at chromium.org
Wed Feb 22 20:17:00 CET 2023


Hi Eddie,

On Wed, 22 Feb 2023 at 11:02, Eddie James <eajames at linux.ibm.com> wrote:
>
> Add a configuration option to measure the boot through the bootm
> function. Add the measurement state to the booti and bootz paths
> as well.
>
> Signed-off-by: Eddie James <eajames at linux.ibm.com>
> ---
>  boot/Kconfig    | 23 ++++++++++++++++
>  boot/bootm.c    | 70 +++++++++++++++++++++++++++++++++++++++++++++++++
>  cmd/booti.c     |  1 +
>  cmd/bootm.c     |  2 ++
>  cmd/bootz.c     |  1 +
>  include/bootm.h |  2 ++
>  include/image.h |  1 +
>  7 files changed, 100 insertions(+)

Reviewed-by: Simon Glass <sjg at chromium.org>

>
> diff --git a/boot/Kconfig b/boot/Kconfig
> index 5f491625c8..d0d5e5794c 100644
> --- a/boot/Kconfig
> +++ b/boot/Kconfig
> @@ -629,6 +629,29 @@ config LEGACY_IMAGE_FORMAT
>           loaded. If a board needs the legacy image format support in this
>           case, enable it here.
>
> +config MEASURED_BOOT
> +       bool "Measure boot images and configuration to TPM and event log"
> +       depends on HASH && TPM_V2
> +       help
> +         This option enables measurement of the boot process. Measurement
> +         involves creating cryptographic hashes of the binary images that
> +         are booting and storing them in the TPM. In addition, a log of
> +         these hashes is stored in memory for the OS to verify the booted
> +         images and configuration. Enable this if the OS has configured
> +         some memory area for the event log and you intend to use some
> +         attestation tools on your system.
> +
> +if MEASURED_BOOT
> +       config MEASURE_DEVICETREE
> +       bool "Measure the devicetree image"
> +       default y if MEASURED_BOOT
> +       help
> +         On some platforms, the devicetree is not static as it may contain
> +         random MAC addresses or other such data that changes each boot.
> +         Therefore, it should not be measured into the TPM. In that case,
> +         disable the measurement here.
> +endif # MEASURED_BOOT
> +
>  config SUPPORT_RAW_INITRD
>         bool "Enable raw initrd images"
>         help
> diff --git a/boot/bootm.c b/boot/bootm.c
> index 2eec60ec7b..10b4848c7e 100644
> --- a/boot/bootm.c
> +++ b/boot/bootm.c
> @@ -22,6 +22,7 @@
>  #include <asm/global_data.h>
>  #include <asm/io.h>
>  #include <linux/sizes.h>
> +#include <tpm-v2.h>
>  #if defined(CONFIG_CMD_USB)
>  #include <usb.h>
>  #endif
> @@ -659,6 +660,72 @@ int bootm_process_cmdline_env(int flags)
>         return 0;
>  }
>
> +int bootm_measure(struct bootm_headers *images)
> +{
> +       int ret = 0;
> +
> +       /* Skip measurement if EFI is going to do it */
> +       if (images->os.os == IH_OS_EFI &&
> +           IS_ENABLED(CONFIG_EFI_TCG2_PROTOCOL) &&
> +           IS_ENABLED(CONFIG_BOOTM_EFI))
> +               return ret;
> +
> +       if (IS_ENABLED(CONFIG_MEASURED_BOOT)) {
> +               struct tcg2_event_log elog;
> +               struct udevice *dev;
> +               void *initrd_buf;
> +               void *image_buf;
> +               const char *s;
> +               u32 rd_len;
> +
> +               ret = tcg2_measurement_init(&dev, &elog);
> +               if (ret)
> +                       return ret;
> +
> +               image_buf = map_sysmem(images->os.image_start,
> +                                      images->os.image_len);
> +               ret = tcg2_measure_data(dev, &elog, 8, images->os.image_len,
> +                                       image_buf, EV_COMPACT_HASH,
> +                                       strlen("linux") + 1, (u8 *)"linux");
> +               if (ret)
> +                       goto unmap_image;
> +
> +               rd_len = images->rd_end - images->rd_start;
> +               initrd_buf = map_sysmem(images->rd_start, rd_len);
> +               ret = tcg2_measure_data(dev, &elog, 9, rd_len, initrd_buf,
> +                                       EV_COMPACT_HASH, strlen("initrd") + 1,
> +                                       (u8 *)"initrd");
> +               if (ret)
> +                       goto unmap_initrd;
> +
> +               if (IS_ENABLED(CONFIG_MEASURE_DEVICETREE)) {
> +                       ret = tcg2_measure_data(dev, &elog, 0, images->ft_len,
> +                                               (u8 *)images->ft_addr,
> +                                               EV_TABLE_OF_DEVICES,
> +                                               strlen("dts") + 1,
> +                                               (u8 *)"dts");
> +                       if (ret)
> +                               goto unmap_initrd;
> +               }
> +
> +               s = env_get("bootargs");
> +               if (!s)
> +                       s = "";
> +               ret = tcg2_measure_data(dev, &elog, 1, strlen(s) + 1, (u8 *)s,
> +                                       EV_PLATFORM_CONFIG_FLAGS,
> +                                       strlen(s) + 1, (u8 *)s);
> +
> +unmap_initrd:
> +               unmap_sysmem(initrd_buf);
> +
> +unmap_image:
> +               unmap_sysmem(image_buf);
> +               tcg2_measurement_term(dev, &elog, ret != 0);
> +       }
> +
> +       return ret;
> +}
> +
>  /**
>   * Execute selected states of the bootm command.
>   *
> @@ -710,6 +777,9 @@ int do_bootm_states(struct cmd_tbl *cmdtp, int flag, int argc,
>         if (!ret && (states & BOOTM_STATE_FINDOTHER))
>                 ret = bootm_find_other(cmdtp, flag, argc, argv);
>
> +       if (IS_ENABLED(CONFIG_MEASURED_BOOT) && !ret && (states & BOOTM_STATE_MEASURE))

line length?

> +               bootm_measure(images);
> +
>         /* Load the OS */
>         if (!ret && (states & BOOTM_STATE_LOADOS)) {
>                 iflag = bootm_disable_interrupts();
> diff --git a/cmd/booti.c b/cmd/booti.c
> index 6ac39193db..659bb10549 100644
> --- a/cmd/booti.c
> +++ b/cmd/booti.c
> @@ -127,6 +127,7 @@ int do_booti(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
>  #ifdef CONFIG_SYS_BOOT_RAMDISK_HIGH
>                               BOOTM_STATE_RAMDISK |
>  #endif
> +                             BOOTM_STATE_MEASURE |
>                               BOOTM_STATE_OS_PREP | BOOTM_STATE_OS_FAKE_GO |
>                               BOOTM_STATE_OS_GO,
>                               &images, 1);
> diff --git a/cmd/bootm.c b/cmd/bootm.c
> index 37c2af96e0..0c4a713e02 100644
> --- a/cmd/bootm.c
> +++ b/cmd/bootm.c
> @@ -161,6 +161,8 @@ int do_bootm(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
>                 BOOTM_STATE_OS_GO;
>         if (IS_ENABLED(CONFIG_SYS_BOOT_RAMDISK_HIGH))
>                 states |= BOOTM_STATE_RAMDISK;
> +       if (IS_ENABLED(CONFIG_MEASURED_BOOT))
> +               states |= BOOTM_STATE_MEASURE;
>         if (IS_ENABLED(CONFIG_PPC) || IS_ENABLED(CONFIG_MIPS))
>                 states |= BOOTM_STATE_OS_CMDLINE;
>         ret = do_bootm_states(cmdtp, flag, argc, argv, states, &images, 1);
> diff --git a/cmd/bootz.c b/cmd/bootz.c
> index f1423573d2..87922bfc3c 100644
> --- a/cmd/bootz.c
> +++ b/cmd/bootz.c
> @@ -81,6 +81,7 @@ int do_bootz(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
>  #ifdef CONFIG_SYS_BOOT_RAMDISK_HIGH
>                               BOOTM_STATE_RAMDISK |
>  #endif
> +                             BOOTM_STATE_MEASURE |
>                               BOOTM_STATE_OS_PREP | BOOTM_STATE_OS_FAKE_GO |
>                               BOOTM_STATE_OS_GO,
>                               &images, 1);
> diff --git a/include/bootm.h b/include/bootm.h
> index 044a4797ed..06d8b1acd8 100644
> --- a/include/bootm.h
> +++ b/include/bootm.h
> @@ -55,6 +55,8 @@ ulong bootm_disable_interrupts(void);
>  int bootm_find_images(int flag, int argc, char *const argv[], ulong start,
>                       ulong size);
>
> +int bootm_measure(struct bootm_headers *images);

please add a full comment for this, including what it actually does /
'measures' and what 'measure' means.

> +
>  int do_bootm_states(struct cmd_tbl *cmdtp, int flag, int argc,
>                     char *const argv[], int states, struct bootm_headers *images,
>                     int boot_progress);
> diff --git a/include/image.h b/include/image.h
> index 7717a4c13d..f7414b5338 100644
> --- a/include/image.h
> +++ b/include/image.h
> @@ -407,6 +407,7 @@ struct bootm_headers {
>  #define BOOTM_STATE_OS_FAKE_GO 0x00000200      /* 'Almost' run the OS */
>  #define BOOTM_STATE_OS_GO      0x00000400
>  #define BOOTM_STATE_PRE_LOAD   0x00000800
> +#define BOOTM_STATE_MEASURE    0x00001000
>         int             state;
>
>  #if defined(CONFIG_LMB) && !defined(USE_HOSTCC)
> --
> 2.31.1
>

Regards,
Simon


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