bootm: Support boot measurement

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@linux.ibm.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Ilias: Added some info on Kconfig explaining this is when booting !EFI
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

2 files changed, 106 insertions, 0 deletions

diff --git a/boot/Kconfig b/boot/Kconfig
index a01e6cb8aa..fbc49c5bca 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 when booting without EFI"
+	depends on HASH && TPM_V2
+	help
+	  This option enables measurement of the boot process when booting
+	  without UEFI . 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 b1c3afe0a3..11b6b3c292 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
@@ -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();