Merge tag 'tpm-next-27102023' of https://source.denx.de/u-boot/custod…

…ians/u-boot-tpm

bootX measurements and measurement API moved to u-boot core:

Up to now, U-Boot could perform measurements and EventLog creation as
described by the TCG spec when booting via EFI.

The EFI code was residing in lib/efi_loader/efi_tcg2.c and contained
both EFI specific code + the API needed to access the TPM, extend PCRs
and create an EventLog. The non-EFI part proved modular enough and
moving it around to the TPM subsystem was straightforward.

With that in place we can have a common API for measuring binaries
regardless of the boot command, EFI or boot(m|i|z), and contructing an
EventLog.

I've tested all of the EFI cases -- booting with an empty EventLog and
booting with a previous stage loader providing one and found no
regressions.  Eddie tested the bootX part.

Eddie also fixed the sandbox TPM which couldn't be used for the EFI code
and it now supports all the required capabilities. This had a slight
sideeffect in our testing since the EFI subsystem initializes the TPM
early and 'tpm2 init' failed during some python tests. That code only
opens the device though, so we can replace it with 'tpm2 autostart'
which doesn't error out and still allows you to perfom the rest of the
tests but doesn't report an error if the device is already opened.

There's a few minor issues with this PR as well but since testing and
verifying the changes takes a considerable amount of time, I prefer
merging it now.

Heinrich has already sent a PR for -master containing "efi_loader: fix
EFI_ENTRY point on get_active_pcr_banks" and I am not sure if that will
cause any conflicts, but in any case they should be trivial to resolve.

Both the EFI and non-EFI code have a Kconfig for measuring the loaded
Device Tree.  The reason this is optional is that we can't reason
when/if devices add random info like kaslr-seed, mac addresses etc in
the DT. In that case measurements are random, board specific and
eventually useless.  The reason it was difficult to fix it prior to this
patchset is because the EFI subsystem and thus measurements was brought
up late and DT fixups might have already been applied. With this
patchset we can measure the DT really early in the future.

Heinrich also pointed out that the two Kconfigs for the DTB measurements
can be squashed in a single one and that the documentation only explains
the non-EFI case.  I agree on both but as I said this is a sane working
version, so let's pull this first it's aleady big enough and painful to
test.

arch/sandbox/dts/sandbox.dtsi

@@ -4,11 +4,23 @@
  * and sandbox64 builds.
  */
 
+#include <config.h>
 #include <dt-bindings/input/input.h>
 
 #define USB_CLASS_HUB			9
 
 / {
+	reserved-memory {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		ranges;
+
+		event_log: tcg_event_log {
+			no-map;
+			reg = <(CFG_SYS_SDRAM_SIZE - 0x2000) 0x2000>;
+		};
+	};
+
 	binman {
 	};
 
@@ -342,6 +354,7 @@
 
 	tpm2 {
 		compatible = "sandbox,tpm2";
+		memory-region = <&event_log>;
 	};
 
 	triangle {

arch/sandbox/dts/test.dts

@@ -9,6 +9,7 @@
 
 /dts-v1/;
 
+#include <config.h>
 #include <dt-bindings/gpio/gpio.h>
 #include <dt-bindings/gpio/sandbox-gpio.h>
 #include <dt-bindings/input/input.h>
@@ -69,6 +70,17 @@
 		osd0 = "/osd";
 	};
 
+	reserved-memory {
+		#address-cells = <1>;
+		#size-cells = <1>;
+		ranges;
+
+		event_log: tcg_event_log {
+			no-map;
+			reg = <(CFG_SYS_SDRAM_SIZE - 0x2000) 0x2000>;
+		};
+	};
+
 	binman: binman {
 	};
 
@@ -1436,6 +1448,7 @@
 
 	tpm2 {
 		compatible = "sandbox,tpm2";
+		memory-region = <&event_log>;
 	};
 
 	tpm {

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

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();

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);

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);

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);

configs/sandbox_defconfig

@@ -14,6 +14,7 @@ CONFIG_FIT_RSASSA_PSS=y
 CONFIG_FIT_CIPHER=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_LEGACY_IMAGE_FORMAT=y
+CONFIG_MEASURED_BOOT=y
 CONFIG_DISTRO_DEFAULTS=y
 CONFIG_BOOTSTAGE=y
 CONFIG_BOOTSTAGE_REPORT=y

doc/usage/index.rst

@@ -14,6 +14,7 @@ Use U-Boot
    partitions
    cmdline
    semihosting
+   measured_boot
 
 Shell commands
 --------------

doc/usage/measured_boot.rst

@@ -0,0 +1,31 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Measured Boot
+=====================
+
+U-Boot can perform a measured boot, the process of hashing various components
+of the boot process, extending the results in the TPM and logging the
+component's measurement in memory for the operating system to consume.
+
+By default, U-Boot will measure the operating system (linux) image, the
+initrd image, and the "bootargs" environment variable. By enabling
+CONFIG_MEASURE_DEVICETREE, U-Boot will also measure the devicetree image.
+
+The operating system typically would verify that the hashes found in the
+TPM PCRs match the contents of the event log. This can further be checked
+against the hash results of previous boots.
+
+Requirements
+---------------------
+
+* A hardware TPM 2.0 supported by the U-Boot drivers
+* CONFIG_TPM=y
+* CONFIG_MEASURED_BOOT=y
+* Device-tree configuration of the TPM device to specify the memory area
+  for event logging. The TPM device node must either contain a phandle to
+  a reserved memory region or "linux,sml-base" and "linux,sml-size"
+  indicating the address and size of the memory region. An example can be
+  found in arch/sandbox/dts/test.dts
+* The operating system must also be configured to use the memory regions
+  specified in the U-Boot device-tree in order to make use of the event
+  log.