Re: [PATCH v7 4/6] bootm: Support boot measurement

Ilias Apalodimas
2023-03-02T10:28:11Z

Hi Eddie,

[...]

>
> +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;

This is nice. Basically measuring becomes the boot command responsibility.

> +
> + 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;
> +
> + elog.log_size = 0;
> + 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 +778,10 @@ 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))
> + 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..76e8e38c82 100644
> --- a/include/bootm.h
> +++ b/include/bootm.h
> @@ -55,6 +55,17 @@ ulong bootm_disable_interrupts(void);
> int bootm_find_images(int flag, int argc, char *const argv[], ulong start,
> ulong size);
>
> +/*
> + * Measure the boot images. Measurement is the process of hashing some binary
> + * data and storing it into secure memory, i.e. TPM PCRs. In addition, each
> + * measurement is logged into the platform event log such that the operating
> + * system can access it and perform attestation of the boot.
> + *
> + * @images: The structure containing the various images to boot (linux,
> + * initrd, dts, etc.)
> + */
> +int bootm_measure(struct bootm_headers *images);
> +
> 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
>

Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>