[PATCH v13 4/8] bootm: Support boot measurement
Eddie James
eajames at linux.ibm.com
Thu Oct 19 18:21:52 CEST 2023
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>
Reviewed-by: Simon Glass <sjg at chromium.org>
---
Changes since v8:
- Added a configuration option to select to ignore any existing
event log. This would only be selected for systems that know
that U-Boot is the first stage bootloader. This is necessary
because the reserved memory region may persist through resets
and so U-Boot attempts to append to the previous boot's log.
Changes since v6:
- Added comment for bootm_measure
- Fixed line length in bootm_measure
boot/Kconfig | 32 +++++++++++++++++++++
boot/bootm.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++
cmd/booti.c | 1 +
cmd/bootm.c | 2 ++
cmd/bootz.c | 1 +
include/bootm.h | 11 ++++++++
include/image.h | 1 +
7 files changed, 122 insertions(+)
diff --git a/boot/Kconfig b/boot/Kconfig
index a01e6cb8aa..abbc72f4cf 100644
--- a/boot/Kconfig
+++ b/boot/Kconfig
@@ -685,6 +685,38 @@ 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.
+
+ config MEASURE_IGNORE_LOG
+ bool "Ignore the existing event log"
+ default n
+ help
+ On platforms that use an event log memory region that persists
+ through system resets and are the first stage bootloader, then
+ this option should be enabled to ignore any existing data in the
+ event log memory region.
+endif # MEASURED_BOOT
+
config SUPPORT_RAW_INITRD
bool "Enable raw initrd images"
help
diff --git a/boot/bootm.c b/boot/bootm.c
index 8f96a80d42..cb61485c22 100644
--- a/boot/bootm.c
+++ b/boot/bootm.c
@@ -23,6 +23,7 @@
#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
@@ -673,6 +674,75 @@ 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;
+ bool ign;
+
+ elog.log_size = 0;
+ ign = IS_ENABLED(CONFIG_MEASURE_IGNORE_LOG);
+ ret = tcg2_measurement_init(&dev, &elog, ign);
+ 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.
*
@@ -724,6 +794,10 @@ 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 1d531bdd06..a6c7db272c 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 3e504ccfe8..6ded091dd5 100644
--- a/cmd/bootm.c
+++ b/cmd/bootm.c
@@ -147,6 +147,8 @@ 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 742889f21d..dd6fe4904b 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 c3c7336207..10a1bd65a7 100644
--- a/include/bootm.h
+++ b/include/bootm.h
@@ -56,6 +56,17 @@ 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 5f85bf84a2..2e3cf839ee 100644
--- a/include/image.h
+++ b/include/image.h
@@ -409,6 +409,7 @@ 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)
--
2.39.3
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