boot/image-fit-sig.c - filogic/uboot - Gitiles

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Copyright (c) 2013, Google Inc.
  */

 #ifdef USE_HOSTCC
 #include "mkimage.h"
 #include <time.h>
 #else
 #include <log.h>
 #include <malloc.h>
 #include <asm/global_data.h>
 DECLARE_GLOBAL_DATA_PTR;
 #endif /* !USE_HOSTCC*/
 #include <fdt_region.h>
 #include <image.h>
 #include <u-boot/rsa.h>
 #include <u-boot/hash-checksum.h>

 #define IMAGE_MAX_HASHED_NODES		100

 /**
  * fit_region_make_list() - Make a list of image regions
  *
  * Given a list of fdt_regions, create a list of image_regions. This is a
  * simple conversion routine since the FDT and image code use different
  * structures.
  *
  * @fit: FIT image
  * @fdt_regions: Pointer to FDT regions
  * @count: Number of FDT regions
  * @region: Pointer to image regions, which must hold @count records. If
  * region is NULL, then (except for an SPL build) the array will be
  * allocated.
  * @return: Pointer to image regions
  */
 struct image_region *fit_region_make_list(const void *fit,
 					  struct fdt_region *fdt_regions,
 					  int count,
 					  struct image_region *region)
 {
 	int i;

 	debug("Hash regions:\n");
 	debug("%10s %10s\n", "Offset", "Size");

 	/*
 	 * Use malloc() except in SPL (to save code size). In SPL the caller
 	 * must allocate the array.
 	 */
 	if (!IS_ENABLED(CONFIG_XPL_BUILD) && !region)
 		region = calloc(sizeof(*region), count);
 	if (!region)
 		return NULL;
 	for (i = 0; i < count; i++) {
 		debug("%10x %10x\n", fdt_regions[i].offset,
 		      fdt_regions[i].size);
 		region[i].data = fit + fdt_regions[i].offset;
 		region[i].size = fdt_regions[i].size;
 	}

 	return region;
 }

 static int fit_image_setup_verify(struct image_sign_info *info,
 				  const void *fit, int noffset,
 				  const void *key_blob, int required_keynode,
 				  char **err_msgp)
 {
 	const char *algo_name;
 	const char *padding_name;

 	if (fdt_totalsize(fit) > CONFIG_VAL(FIT_SIGNATURE_MAX_SIZE)) {
 		*err_msgp = "Total size too large";
 		return 1;
 	}
 	if (fit_image_hash_get_algo(fit, noffset, &algo_name)) {
 		*err_msgp = "Can't get hash algo property";
 		return -1;
 	}

 	padding_name = fdt_getprop(fit, noffset, "padding", NULL);
 	if (!padding_name)
 		padding_name = RSA_DEFAULT_PADDING_NAME;

 	memset(info, '\0', sizeof(*info));
 	info->keyname = fdt_getprop(fit, noffset, FIT_KEY_HINT, NULL);
 	info->fit = fit;
 	info->node_offset = noffset;
 	info->name = algo_name;
 	info->checksum = image_get_checksum_algo(algo_name);
 	info->crypto = image_get_crypto_algo(algo_name);
 	info->padding = image_get_padding_algo(padding_name);
 	info->fdt_blob = key_blob;
 	info->required_keynode = required_keynode;
 	printf("%s:%s", algo_name, info->keyname);

 	if (!info->checksum || !info->crypto) {
 		*err_msgp = "Unknown signature algorithm";
 		return -1;
 	}

 	return 0;
 }

 int fit_image_check_sig(const void *fit, int noffset, const void *data,
 			size_t size, const void *key_blob, int required_keynode,
 			char **err_msgp)
 {
 	struct image_sign_info info;
 	struct image_region region;
 	uint8_t *fit_value;
 	int fit_value_len;

 	*err_msgp = NULL;
 	if (fit_image_setup_verify(&info, fit, noffset, key_blob,
 				   required_keynode, err_msgp))
 		return -1;

 	if (fit_image_hash_get_value(fit, noffset, &fit_value,
 				     &fit_value_len)) {
 		*err_msgp = "Can't get hash value property";
 		return -1;
 	}

 	region.data = data;
 	region.size = size;

 	if (info.crypto->verify(&info, &region, 1, fit_value, fit_value_len)) {
 		*err_msgp = "Verification failed";
 		return -1;
 	}

 	return 0;
 }

 static int fit_image_verify_sig(const void *fit, int image_noffset,
 				const char *data, size_t size,
 				const void *key_blob, int key_offset)
 {
 	int noffset;
 	char *err_msg = "";
 	int verified = 0;
 	int ret;

 	/* Process all hash subnodes of the component image node */
 	fdt_for_each_subnode(noffset, fit, image_noffset) {
 		const char *name = fit_get_name(fit, noffset, NULL);

 		/*
 		 * We don't support this since libfdt considers names with the
 		 * name root but different @ suffix to be equal
 		 */
 		if (strchr(name, '@')) {
 			err_msg = "Node name contains @";
 			goto error;
 		}
 		if (!strncmp(name, FIT_SIG_NODENAME,
 			     strlen(FIT_SIG_NODENAME))) {
 			ret = fit_image_check_sig(fit, noffset, data, size,
 						  key_blob, -1, &err_msg);
 			if (ret) {
 				puts("- ");
 			} else {
 				puts("+ ");
 				verified = 1;
 				break;
 			}
 		}
 	}

 	if (noffset == -FDT_ERR_TRUNCATED || noffset == -FDT_ERR_BADSTRUCTURE) {
 		err_msg = "Corrupted or truncated tree";
 		goto error;
 	}

 	return verified ? 0 : -EPERM;

 error:
 	printf(" error!\n%s for '%s' hash node in '%s' image node\n",
 	       err_msg, fit_get_name(fit, noffset, NULL),
 	       fit_get_name(fit, image_noffset, NULL));
 	return -1;
 }

 int fit_image_verify_required_sigs(const void *fit, int image_noffset,
 				   const char *data, size_t size,
 				   const void *key_blob, int *no_sigsp)
 {
 	int verify_count = 0;
 	int noffset;
 	int key_node;

 	/* Work out what we need to verify */
 	*no_sigsp = 1;
 	key_node = fdt_subnode_offset(key_blob, 0, FIT_SIG_NODENAME);
 	if (key_node < 0) {
 		debug("%s: No signature node found: %s\n", __func__,
 		      fdt_strerror(key_node));
 		return 0;
 	}

 	fdt_for_each_subnode(noffset, key_blob, key_node) {
 		const char *required;
 		int ret;

 		required = fdt_getprop(key_blob, noffset, FIT_KEY_REQUIRED,
 				       NULL);
 		if (!required || strcmp(required, "image"))
 			continue;
 		ret = fit_image_verify_sig(fit, image_noffset, data, size,
 					   key_blob, noffset);
 		if (ret) {
 			printf("Failed to verify required signature '%s'\n",
 			       fit_get_name(key_blob, noffset, NULL));
 			return ret;
 		}
 		verify_count++;
 	}

 	if (verify_count)
 		*no_sigsp = 0;

 	return 0;
 }

 /**
  * fit_config_check_sig() - Check the signature of a config
  *
  * Here we are looking at a particular signature that needs verification (here
  * signature-1):
  *
  *	configurations {
  *		default = "conf-1";
  *		conf-1 {
  *			kernel = "kernel-1";
  *			fdt = "fdt-1";
  *			signature-1 {
  *				algo = "sha1,rsa2048";
  *				value = <...conf 1 signature...>;
  *			};
  *		};
  *
  * @fit: FIT to check
  * @noffset: Offset of the signature node being checked (e.g.
  *	 /configurations/conf-1/signature-1)
  * @conf_noffset: Offset of configuration node (e.g. /configurations/conf-1)
  * @key_blob: Blob containing the keys to check against
  * @required_keynode:	Offset in @key_blob of the required key node,
  *			if any. If this is given, then the configuration wil not
  *			pass verification unless that key is used. If this is
  *			-1 then any signature will do.
  * @err_msgp:		In the event of an error, this will be pointed to a
  *			help error string to display to the user.
  * Return: 0 if all verified ok, <0 on error
  */
 static int fit_config_check_sig(const void *fit, int noffset, int conf_noffset,
 				const void *key_blob, int required_keynode,
 				char **err_msgp)
 {
 	static char * const exc_prop[] = {
 		FIT_DATA_PROP,
 		FIT_DATA_SIZE_PROP,
 		FIT_DATA_POSITION_PROP,
 		FIT_DATA_OFFSET_PROP,
 	};

 	const char *prop, *end, *name;
 	struct image_sign_info info;
 	const uint32_t *strings;
 	const char *config_name;
 	uint8_t *fit_value;
 	int fit_value_len;
 	bool found_config;
 	int max_regions;
 	int i, prop_len;
 	char path[200];
 	int count;

 	config_name = fit_get_name(fit, conf_noffset, NULL);
 	debug("%s: fdt=%p, conf='%s', sig='%s'\n", __func__, key_blob,
 	      fit_get_name(fit, noffset, NULL),
 	      fit_get_name(key_blob, required_keynode, NULL));
 	*err_msgp = NULL;
 	if (fit_image_setup_verify(&info, fit, noffset, key_blob,
 				   required_keynode, err_msgp))
 		return -1;

 	if (fit_image_hash_get_value(fit, noffset, &fit_value,
 				     &fit_value_len)) {
 		*err_msgp = "Can't get hash value property";
 		return -1;
 	}

 	/* Count the number of strings in the property */
 	prop = fdt_getprop(fit, noffset, "hashed-nodes", &prop_len);
 	end = prop ? prop + prop_len : prop;
 	for (name = prop, count = 0; name < end; name++)
 		if (!*name)
 			count++;
 	if (!count) {
 		*err_msgp = "Can't get hashed-nodes property";
 		return -1;
 	}

 	if (prop && prop_len > 0 && prop[prop_len - 1] != '\0') {
 		*err_msgp = "hashed-nodes property must be null-terminated";
 		return -1;
 	}

 	/* Add a sanity check here since we are using the stack */
 	if (count > IMAGE_MAX_HASHED_NODES) {
 		*err_msgp = "Number of hashed nodes exceeds maximum";
 		return -1;
 	}

 	/* Create a list of node names from those strings */
 	char *node_inc[count];

 	debug("Hash nodes (%d):\n", count);
 	found_config = false;
 	for (name = prop, i = 0; name < end; name += strlen(name) + 1, i++) {
 		debug("   '%s'\n", name);
 		node_inc[i] = (char *)name;
 		if (!strncmp(FIT_CONFS_PATH, name, strlen(FIT_CONFS_PATH)) &&
 		    name[sizeof(FIT_CONFS_PATH) - 1] == '/' &&
 		    !strcmp(name + sizeof(FIT_CONFS_PATH), config_name)) {
 			debug("      (found config node %s)", config_name);
 			found_config = true;
 		}
 	}
 	if (!found_config) {
 		*err_msgp = "Selected config not in hashed nodes";
 		return -1;
 	}

 	/*
 	 * Each node can generate one region for each sub-node. Allow for
 	 * 7 sub-nodes (hash-1, signature-1, etc.) and some extra.
 	 */
 	max_regions = 20 + count * 7;
 	struct fdt_region fdt_regions[max_regions];

 	/* Get a list of regions to hash */
 	count = fdt_find_regions(fit, node_inc, count,
 				 exc_prop, ARRAY_SIZE(exc_prop),
 				 fdt_regions, max_regions - 1,
 				 path, sizeof(path), 0);
 	if (count < 0) {
 		*err_msgp = "Failed to hash configuration";
 		return -1;
 	}
 	if (count == 0) {
 		*err_msgp = "No data to hash";
 		return -1;
 	}
 	if (count >= max_regions - 1) {
 		*err_msgp = "Too many hash regions";
 		return -1;
 	}

 	/* Add the strings */
 	strings = fdt_getprop(fit, noffset, "hashed-strings", NULL);
 	if (strings) {
 		/*
 		 * The strings region offset must be a static 0x0.
 		 * This is set in tool/image-host.c
 		 */
 		fdt_regions[count].offset = fdt_off_dt_strings(fit);
 		fdt_regions[count].size = fdt32_to_cpu(strings[1]);
 		count++;
 	}

 	/* Allocate the region list on the stack */
 	struct image_region region[count];

 	fit_region_make_list(fit, fdt_regions, count, region);
 	if (info.crypto->verify(&info, region, count, fit_value,
 				fit_value_len)) {
 		*err_msgp = "Verification failed";
 		return -1;
 	}

 	return 0;
 }

 /**
  * fit_config_verify_key() - Verify that a configuration is signed with a key
  *
  * Here we are looking at a particular configuration that needs verification:
  *
  *	configurations {
  *		default = "conf-1";
  *		conf-1 {
  *			kernel = "kernel-1";
  *			fdt = "fdt-1";
  *			signature-1 {
  *				algo = "sha1,rsa2048";
  *				value = <...conf 1 signature...>;
  *			};
  *		};
  *
  * We must check each of the signature subnodes of conf-1. Hopefully one of them
  * will match the key at key_offset.
  *
  * @fit: FIT to check
  * @conf_noffset: Offset of the configuration node to check (e.g.
  *	/configurations/conf-1)
  * @key_blob: Blob containing the keys to check against
  * @key_offset: Offset of the key to check within @key_blob
  * @return 0 if OK, -EPERM if any signatures did not verify, or the
  *	configuration node has an invalid name
  */
 static int fit_config_verify_key(const void *fit, int conf_noffset,
 				 const void *key_blob, int key_offset)
 {
 	int noffset;
 	char *err_msg = "No 'signature' subnode found";
 	int verified = 0;
 	int ret;

 	/* Process all hash subnodes of the component conf node */
 	fdt_for_each_subnode(noffset, fit, conf_noffset) {
 		const char *name = fit_get_name(fit, noffset, NULL);

 		if (!strncmp(name, FIT_SIG_NODENAME,
 			     strlen(FIT_SIG_NODENAME))) {
 			ret = fit_config_check_sig(fit, noffset, conf_noffset,
 						   key_blob, key_offset,
 						   &err_msg);
 			if (ret) {
 				puts("- ");
 			} else {
 				puts("+ ");
 				verified = 1;
 				break;
 			}
 		}
 	}

 	if (noffset == -FDT_ERR_TRUNCATED || noffset == -FDT_ERR_BADSTRUCTURE) {
 		err_msg = "Corrupted or truncated tree";
 		goto error;
 	}

 	if (verified)
 		return 0;

 error:
 	printf(" error!\n%s for '%s' hash node in '%s' config node\n",
 	       err_msg, fit_get_name(fit, noffset, NULL),
 	       fit_get_name(fit, conf_noffset, NULL));
 	return -EPERM;
 }

 /**
  * fit_config_verify_required_keys() - verify any required signatures for config
  *
  * This looks through all the signatures we expect and verifies that at least
  * all the required ones are valid signatures for the configuration
  *
  * @fit: FIT to check
  * @conf_noffset: Offset of the configuration node to check (e.g.
  *	/configurations/conf-1)
  * @key_blob: Blob containing the keys to check against
  * @return 0 if OK, -EPERM if any signatures did not verify, or the
  *	configuration node has an invalid name
  */
 static int fit_config_verify_required_keys(const void *fit, int conf_noffset,
 					   const void *key_blob)
 {
 	const char *name = fit_get_name(fit, conf_noffset, NULL);
 	int noffset;
 	int key_node;
 	int verified = 0;
 	int reqd_sigs = 0;
 	bool reqd_policy_all = true;
 	const char *reqd_mode;

 	/*
 	 * We don't support this since libfdt considers names with the
 	 * name root but different @ suffix to be equal
 	 */
 	if (strchr(name, '@')) {
 		printf("Configuration node '%s' contains '@'\n", name);
 		return -EPERM;
 	}

 	/* Work out what we need to verify */
 	key_node = fdt_subnode_offset(key_blob, 0, FIT_SIG_NODENAME);
 	if (key_node < 0) {
 		debug("%s: No signature node found: %s\n", __func__,
 		      fdt_strerror(key_node));
 		return 0;
 	}

 	/* Get required-mode policy property from DTB */
 	reqd_mode = fdt_getprop(key_blob, key_node, "required-mode", NULL);
 	if (reqd_mode && !strcmp(reqd_mode, "any"))
 		reqd_policy_all = false;

 	debug("%s: required-mode policy set to '%s'\n", __func__,
 	      reqd_policy_all ? "all" : "any");

 	/*
 	 * The algorithm here is a little convoluted due to how we want it to
 	 * work. Here we work through each of the signature nodes in the
 	 * public-key area. These are in the U-Boot control devicetree. Each
 	 * node was created by signing a configuration, so we check if it is
 	 * 'required' and if so, request that it be verified.
 	 */
 	fdt_for_each_subnode(noffset, key_blob, key_node) {
 		const char *required;
 		int ret;

 		required = fdt_getprop(key_blob, noffset, FIT_KEY_REQUIRED,
 				       NULL);
 		if (!required || strcmp(required, "conf"))
 			continue;

 		reqd_sigs++;

 		ret = fit_config_verify_key(fit, conf_noffset, key_blob,
 					    noffset);
 		if (ret) {
 			if (reqd_policy_all) {
 				printf("Failed to verify required signature '%s'\n",
 				       fit_get_name(key_blob, noffset, NULL));
 				return ret;
 			}
 		} else {
 			verified++;
 			if (!reqd_policy_all)
 				break;
 		}
 	}

 	if (reqd_sigs && !verified) {
 		printf("Failed to verify 'any' of the required signature(s)\n");
 		return -EPERM;
 	}

 	return 0;
 }

 int fit_config_verify(const void *fit, int conf_noffset)
 {
 	return fit_config_verify_required_keys(fit, conf_noffset,
 					       gd_fdt_blob());
 }
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Copyright (c) 2013, Google Inc.
	*/

	#ifdef USE_HOSTCC
	#include "mkimage.h"
	#include <time.h>
	#else
	#include <log.h>
	#include <malloc.h>
	#include <asm/global_data.h>
	DECLARE_GLOBAL_DATA_PTR;
	#endif /* !USE_HOSTCC*/
	#include <fdt_region.h>
	#include <image.h>
	#include <u-boot/rsa.h>
	#include <u-boot/hash-checksum.h>

	#define IMAGE_MAX_HASHED_NODES 100

	/**
	* fit_region_make_list() - Make a list of image regions
	*
	* Given a list of fdt_regions, create a list of image_regions. This is a
	* simple conversion routine since the FDT and image code use different
	* structures.
	*
	* @fit: FIT image
	* @fdt_regions: Pointer to FDT regions
	* @count: Number of FDT regions
	* @region: Pointer to image regions, which must hold @count records. If
	* region is NULL, then (except for an SPL build) the array will be
	* allocated.
	* @return: Pointer to image regions
	*/
	struct image_region fit_region_make_list(const void fit,
	struct fdt_region *fdt_regions,
	int count,
	struct image_region *region)
	{
	int i;

	debug("Hash regions:\n");
	debug("%10s %10s\n", "Offset", "Size");

	/*
	* Use malloc() except in SPL (to save code size). In SPL the caller
	* must allocate the array.
	*/
	if (!IS_ENABLED(CONFIG_XPL_BUILD) && !region)
	region = calloc(sizeof(*region), count);
	if (!region)
	return NULL;
	for (i = 0; i < count; i++) {
	debug("%10x %10x\n", fdt_regions[i].offset,
	fdt_regions[i].size);
	region[i].data = fit + fdt_regions[i].offset;
	region[i].size = fdt_regions[i].size;
	}

	return region;
	}

	static int fit_image_setup_verify(struct image_sign_info *info,
	const void *fit, int noffset,
	const void *key_blob, int required_keynode,
	char **err_msgp)
	{
	const char *algo_name;
	const char *padding_name;

	if (fdt_totalsize(fit) > CONFIG_VAL(FIT_SIGNATURE_MAX_SIZE)) {
	*err_msgp = "Total size too large";
	return 1;
	}
	if (fit_image_hash_get_algo(fit, noffset, &algo_name)) {
	*err_msgp = "Can't get hash algo property";
	return -1;
	}

	padding_name = fdt_getprop(fit, noffset, "padding", NULL);
	if (!padding_name)
	padding_name = RSA_DEFAULT_PADDING_NAME;

	memset(info, '\0', sizeof(*info));
	info->keyname = fdt_getprop(fit, noffset, FIT_KEY_HINT, NULL);
	info->fit = fit;
	info->node_offset = noffset;
	info->name = algo_name;
	info->checksum = image_get_checksum_algo(algo_name);
	info->crypto = image_get_crypto_algo(algo_name);
	info->padding = image_get_padding_algo(padding_name);
	info->fdt_blob = key_blob;
	info->required_keynode = required_keynode;
	printf("%s:%s", algo_name, info->keyname);

	if (!info->checksum \|\| !info->crypto) {
	*err_msgp = "Unknown signature algorithm";
	return -1;
	}

	return 0;
	}

	int fit_image_check_sig(const void fit, int noffset, const void data,
	size_t size, const void *key_blob, int required_keynode,
	char **err_msgp)
	{
	struct image_sign_info info;
	struct image_region region;
	uint8_t *fit_value;
	int fit_value_len;

	*err_msgp = NULL;
	if (fit_image_setup_verify(&info, fit, noffset, key_blob,
	required_keynode, err_msgp))
	return -1;

	if (fit_image_hash_get_value(fit, noffset, &fit_value,
	&fit_value_len)) {
	*err_msgp = "Can't get hash value property";
	return -1;
	}

	region.data = data;
	region.size = size;

	if (info.crypto->verify(&info, &region, 1, fit_value, fit_value_len)) {
	*err_msgp = "Verification failed";
	return -1;
	}

	return 0;
	}

	static int fit_image_verify_sig(const void *fit, int image_noffset,
	const char *data, size_t size,
	const void *key_blob, int key_offset)
	{
	int noffset;
	char *err_msg = "";
	int verified = 0;
	int ret;

	/* Process all hash subnodes of the component image node */
	fdt_for_each_subnode(noffset, fit, image_noffset) {
	const char *name = fit_get_name(fit, noffset, NULL);

	/*
	* We don't support this since libfdt considers names with the
	* name root but different @ suffix to be equal
	*/
	if (strchr(name, '@')) {
	err_msg = "Node name contains @";
	goto error;
	}
	if (!strncmp(name, FIT_SIG_NODENAME,
	strlen(FIT_SIG_NODENAME))) {
	ret = fit_image_check_sig(fit, noffset, data, size,
	key_blob, -1, &err_msg);
	if (ret) {
	puts("- ");
	} else {
	puts("+ ");
	verified = 1;
	break;
	}
	}
	}

	if (noffset == -FDT_ERR_TRUNCATED \|\| noffset == -FDT_ERR_BADSTRUCTURE) {
	err_msg = "Corrupted or truncated tree";
	goto error;
	}

	return verified ? 0 : -EPERM;

	error:
	printf(" error!\n%s for '%s' hash node in '%s' image node\n",
	err_msg, fit_get_name(fit, noffset, NULL),
	fit_get_name(fit, image_noffset, NULL));
	return -1;
	}

	int fit_image_verify_required_sigs(const void *fit, int image_noffset,
	const char *data, size_t size,
	const void key_blob, int no_sigsp)
	{
	int verify_count = 0;
	int noffset;
	int key_node;

	/* Work out what we need to verify */
	*no_sigsp = 1;
	key_node = fdt_subnode_offset(key_blob, 0, FIT_SIG_NODENAME);
	if (key_node < 0) {
	debug("%s: No signature node found: %s\n", __func__,
	fdt_strerror(key_node));
	return 0;
	}

	fdt_for_each_subnode(noffset, key_blob, key_node) {
	const char *required;
	int ret;

	required = fdt_getprop(key_blob, noffset, FIT_KEY_REQUIRED,
	NULL);
	if (!required \|\| strcmp(required, "image"))
	continue;
	ret = fit_image_verify_sig(fit, image_noffset, data, size,
	key_blob, noffset);
	if (ret) {
	printf("Failed to verify required signature '%s'\n",
	fit_get_name(key_blob, noffset, NULL));
	return ret;
	}
	verify_count++;
	}

	if (verify_count)
	*no_sigsp = 0;

	return 0;
	}

	/**
	* fit_config_check_sig() - Check the signature of a config
	*
	* Here we are looking at a particular signature that needs verification (here
	* signature-1):
	*
	* configurations {
	* default = "conf-1";
	* conf-1 {
	* kernel = "kernel-1";
	* fdt = "fdt-1";
	* signature-1 {
	* algo = "sha1,rsa2048";
	* value = <...conf 1 signature...>;
	* };
	* };
	*
	* @fit: FIT to check
	* @noffset: Offset of the signature node being checked (e.g.
	* /configurations/conf-1/signature-1)
	* @conf_noffset: Offset of configuration node (e.g. /configurations/conf-1)
	* @key_blob: Blob containing the keys to check against
	* @required_keynode: Offset in @key_blob of the required key node,
	* if any. If this is given, then the configuration wil not
	* pass verification unless that key is used. If this is
	* -1 then any signature will do.
	* @err_msgp: In the event of an error, this will be pointed to a
	* help error string to display to the user.
	* Return: 0 if all verified ok, <0 on error
	*/
	static int fit_config_check_sig(const void *fit, int noffset, int conf_noffset,
	const void *key_blob, int required_keynode,
	char **err_msgp)
	{
	static char * const exc_prop[] = {
	FIT_DATA_PROP,
	FIT_DATA_SIZE_PROP,
	FIT_DATA_POSITION_PROP,
	FIT_DATA_OFFSET_PROP,
	};

	const char prop, end, *name;
	struct image_sign_info info;
	const uint32_t *strings;
	const char *config_name;
	uint8_t *fit_value;
	int fit_value_len;
	bool found_config;
	int max_regions;
	int i, prop_len;
	char path[200];
	int count;

	config_name = fit_get_name(fit, conf_noffset, NULL);
	debug("%s: fdt=%p, conf='%s', sig='%s'\n", __func__, key_blob,
	fit_get_name(fit, noffset, NULL),
	fit_get_name(key_blob, required_keynode, NULL));
	*err_msgp = NULL;
	if (fit_image_setup_verify(&info, fit, noffset, key_blob,
	required_keynode, err_msgp))
	return -1;

	if (fit_image_hash_get_value(fit, noffset, &fit_value,
	&fit_value_len)) {
	*err_msgp = "Can't get hash value property";
	return -1;
	}

	/* Count the number of strings in the property */
	prop = fdt_getprop(fit, noffset, "hashed-nodes", &prop_len);
	end = prop ? prop + prop_len : prop;
	for (name = prop, count = 0; name < end; name++)
	if (!*name)
	count++;
	if (!count) {
	*err_msgp = "Can't get hashed-nodes property";
	return -1;
	}

	if (prop && prop_len > 0 && prop[prop_len - 1] != '\0') {
	*err_msgp = "hashed-nodes property must be null-terminated";
	return -1;
	}

	/* Add a sanity check here since we are using the stack */
	if (count > IMAGE_MAX_HASHED_NODES) {
	*err_msgp = "Number of hashed nodes exceeds maximum";
	return -1;
	}

	/* Create a list of node names from those strings */
	char *node_inc[count];

	debug("Hash nodes (%d):\n", count);
	found_config = false;
	for (name = prop, i = 0; name < end; name += strlen(name) + 1, i++) {
	debug(" '%s'\n", name);
	node_inc[i] = (char *)name;
	if (!strncmp(FIT_CONFS_PATH, name, strlen(FIT_CONFS_PATH)) &&
	name[sizeof(FIT_CONFS_PATH) - 1] == '/' &&
	!strcmp(name + sizeof(FIT_CONFS_PATH), config_name)) {
	debug(" (found config node %s)", config_name);
	found_config = true;
	}
	}
	if (!found_config) {
	*err_msgp = "Selected config not in hashed nodes";
	return -1;
	}

	/*
	* Each node can generate one region for each sub-node. Allow for
	* 7 sub-nodes (hash-1, signature-1, etc.) and some extra.
	*/
	max_regions = 20 + count * 7;
	struct fdt_region fdt_regions[max_regions];

	/* Get a list of regions to hash */
	count = fdt_find_regions(fit, node_inc, count,
	exc_prop, ARRAY_SIZE(exc_prop),
	fdt_regions, max_regions - 1,
	path, sizeof(path), 0);
	if (count < 0) {
	*err_msgp = "Failed to hash configuration";
	return -1;
	}
	if (count == 0) {
	*err_msgp = "No data to hash";
	return -1;
	}
	if (count >= max_regions - 1) {
	*err_msgp = "Too many hash regions";
	return -1;
	}

	/* Add the strings */
	strings = fdt_getprop(fit, noffset, "hashed-strings", NULL);
	if (strings) {
	/*
	* The strings region offset must be a static 0x0.
	* This is set in tool/image-host.c
	*/
	fdt_regions[count].offset = fdt_off_dt_strings(fit);
	fdt_regions[count].size = fdt32_to_cpu(strings[1]);
	count++;
	}

	/* Allocate the region list on the stack */
	struct image_region region[count];

	fit_region_make_list(fit, fdt_regions, count, region);
	if (info.crypto->verify(&info, region, count, fit_value,
	fit_value_len)) {
	*err_msgp = "Verification failed";
	return -1;
	}

	return 0;
	}

	/**
	* fit_config_verify_key() - Verify that a configuration is signed with a key
	*
	* Here we are looking at a particular configuration that needs verification:
	*
	* configurations {
	* default = "conf-1";
	* conf-1 {
	* kernel = "kernel-1";
	* fdt = "fdt-1";
	* signature-1 {
	* algo = "sha1,rsa2048";
	* value = <...conf 1 signature...>;
	* };
	* };
	*
	* We must check each of the signature subnodes of conf-1. Hopefully one of them
	* will match the key at key_offset.
	*
	* @fit: FIT to check
	* @conf_noffset: Offset of the configuration node to check (e.g.
	* /configurations/conf-1)
	* @key_blob: Blob containing the keys to check against
	* @key_offset: Offset of the key to check within @key_blob
	* @return 0 if OK, -EPERM if any signatures did not verify, or the
	* configuration node has an invalid name
	*/
	static int fit_config_verify_key(const void *fit, int conf_noffset,
	const void *key_blob, int key_offset)
	{
	int noffset;
	char *err_msg = "No 'signature' subnode found";
	int verified = 0;
	int ret;

	/* Process all hash subnodes of the component conf node */
	fdt_for_each_subnode(noffset, fit, conf_noffset) {
	const char *name = fit_get_name(fit, noffset, NULL);

	if (!strncmp(name, FIT_SIG_NODENAME,
	strlen(FIT_SIG_NODENAME))) {
	ret = fit_config_check_sig(fit, noffset, conf_noffset,
	key_blob, key_offset,
	&err_msg);
	if (ret) {
	puts("- ");
	} else {
	puts("+ ");
	verified = 1;
	break;
	}
	}
	}

	if (noffset == -FDT_ERR_TRUNCATED \|\| noffset == -FDT_ERR_BADSTRUCTURE) {
	err_msg = "Corrupted or truncated tree";
	goto error;
	}

	if (verified)
	return 0;

	error:
	printf(" error!\n%s for '%s' hash node in '%s' config node\n",
	err_msg, fit_get_name(fit, noffset, NULL),
	fit_get_name(fit, conf_noffset, NULL));
	return -EPERM;
	}

	/**
	* fit_config_verify_required_keys() - verify any required signatures for config
	*
	* This looks through all the signatures we expect and verifies that at least
	* all the required ones are valid signatures for the configuration
	*
	* @fit: FIT to check
	* @conf_noffset: Offset of the configuration node to check (e.g.
	* /configurations/conf-1)
	* @key_blob: Blob containing the keys to check against
	* @return 0 if OK, -EPERM if any signatures did not verify, or the
	* configuration node has an invalid name
	*/
	static int fit_config_verify_required_keys(const void *fit, int conf_noffset,
	const void *key_blob)
	{
	const char *name = fit_get_name(fit, conf_noffset, NULL);
	int noffset;
	int key_node;
	int verified = 0;
	int reqd_sigs = 0;
	bool reqd_policy_all = true;
	const char *reqd_mode;

	/*
	* We don't support this since libfdt considers names with the
	* name root but different @ suffix to be equal
	*/
	if (strchr(name, '@')) {
	printf("Configuration node '%s' contains '@'\n", name);
	return -EPERM;
	}

	/* Work out what we need to verify */
	key_node = fdt_subnode_offset(key_blob, 0, FIT_SIG_NODENAME);
	if (key_node < 0) {
	debug("%s: No signature node found: %s\n", __func__,
	fdt_strerror(key_node));
	return 0;
	}

	/* Get required-mode policy property from DTB */
	reqd_mode = fdt_getprop(key_blob, key_node, "required-mode", NULL);
	if (reqd_mode && !strcmp(reqd_mode, "any"))
	reqd_policy_all = false;

	debug("%s: required-mode policy set to '%s'\n", __func__,
	reqd_policy_all ? "all" : "any");

	/*
	* The algorithm here is a little convoluted due to how we want it to
	* work. Here we work through each of the signature nodes in the
	* public-key area. These are in the U-Boot control devicetree. Each
	* node was created by signing a configuration, so we check if it is
	* 'required' and if so, request that it be verified.
	*/
	fdt_for_each_subnode(noffset, key_blob, key_node) {
	const char *required;
	int ret;

	required = fdt_getprop(key_blob, noffset, FIT_KEY_REQUIRED,
	NULL);
	if (!required \|\| strcmp(required, "conf"))
	continue;

	reqd_sigs++;

	ret = fit_config_verify_key(fit, conf_noffset, key_blob,
	noffset);
	if (ret) {
	if (reqd_policy_all) {
	printf("Failed to verify required signature '%s'\n",
	fit_get_name(key_blob, noffset, NULL));
	return ret;
	}
	} else {
	verified++;
	if (!reqd_policy_all)
	break;
	}
	}

	if (reqd_sigs && !verified) {
	printf("Failed to verify 'any' of the required signature(s)\n");
	return -EPERM;
	}

	return 0;
	}

	int fit_config_verify(const void *fit, int conf_noffset)
	{
	return fit_config_verify_required_keys(fit, conf_noffset,
	gd_fdt_blob());
	}