[PATCH v2 3/5] bootm: Support boot measurement

9 Jan 2023

Add a configuration option to measure the boot through the bootm
function.
Signed-off-by: Eddie James eajames@linux.ibm.com
---
 boot/Kconfig    | 23 ++++++++++++++++++
 boot/bootm.c    | 64 +++++++++++++++++++++++++++++++++++++++++++++++++
 cmd/bootm.c     |  2 ++
 include/bootm.h |  2 ++
 include/image.h |  1 +
 5 files changed, 92 insertions(+)

diff --git a/boot/Kconfig b/boot/Kconfig
index 30bc182fcd..e90d61412e 100644
--- a/boot/Kconfig
+++ b/boot/Kconfig
@@ -587,6 +587,29 @@ 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 15fce8ad95..932961ceb7 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 +660,66 @@ int bootm_process_cmdline_env(int flags)
    return 0;
 }
+int bootm_measure(struct bootm_headers *images)
+{
+	int ret = 0;
+
+	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, 8, 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, 9, 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 +771,9 @@ 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))
+		bootm_measure(images);
+
    /* Load the OS */
    if (!ret && (states & BOOTM_STATE_LOADOS)) {
    	iflag = bootm_disable_interrupts();
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/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);
+
 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 bed75ce1b3..bd74e74a75 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


    