lib/efi_loader/efi_signature.c - platform/external/u-boot - Gitiles

 // SPDX-License-Identifier: GPL-2.0+
 /*
  * Copyright (c) 2018 Patrick Wildt <patrick@blueri.se>
  * Copyright (c) 2019 Linaro Limited, Author: AKASHI Takahiro
  */

 #include <common.h>
 #include <charset.h>
 #include <efi_loader.h>
 #include <image.h>
 #include <hexdump.h>
 #include <malloc.h>
 #include <crypto/pkcs7.h>
 #include <crypto/pkcs7_parser.h>
 #include <crypto/public_key.h>
 #include <linux/compat.h>
 #include <linux/oid_registry.h>
 #include <u-boot/rsa.h>
 #include <u-boot/sha256.h>

 const efi_guid_t efi_guid_image_security_database =
 		EFI_IMAGE_SECURITY_DATABASE_GUID;
 const efi_guid_t efi_guid_sha256 = EFI_CERT_SHA256_GUID;
 const efi_guid_t efi_guid_cert_rsa2048 = EFI_CERT_RSA2048_GUID;
 const efi_guid_t efi_guid_cert_x509 = EFI_CERT_X509_GUID;
 const efi_guid_t efi_guid_cert_x509_sha256 = EFI_CERT_X509_SHA256_GUID;
 const efi_guid_t efi_guid_cert_type_pkcs7 = EFI_CERT_TYPE_PKCS7_GUID;

 #ifdef CONFIG_EFI_SECURE_BOOT

 /**
  * efi_hash_regions - calculate a hash value
  * @regs:	Array of regions
  * @count:	Number of regions
  * @hash:	Pointer to a pointer to buffer holding a hash value
  * @size:	Size of buffer to be returned
  *
  * Calculate a sha256 value of @regs and return a value in @hash.
  *
  * Return:	true on success, false on error
  */
 static bool efi_hash_regions(struct image_region *regs, int count,
 			     void **hash, size_t *size)
 {
 	if (!*hash) {
 		*hash = calloc(1, SHA256_SUM_LEN);
 		if (!*hash) {
 			EFI_PRINT("Out of memory\n");
 			return false;
 		}
 	}
 	if (size)
 		*size = SHA256_SUM_LEN;

 	hash_calculate("sha256", regs, count, *hash);
 #ifdef DEBUG
 	EFI_PRINT("hash calculated:\n");
 	print_hex_dump("    ", DUMP_PREFIX_OFFSET, 16, 1,
 		       *hash, SHA256_SUM_LEN, false);
 #endif

 	return true;
 }

 /**
  * efi_signature_lookup_digest - search for an image's digest in sigdb
  * @regs:	List of regions to be authenticated
  * @db:		Signature database for trusted certificates
  *
  * A message digest of image pointed to by @regs is calculated and
  * its hash value is compared to entries in signature database pointed
  * to by @db.
  *
  * Return:	true if found, false if not
  */
 bool efi_signature_lookup_digest(struct efi_image_regions *regs,
 				 struct efi_signature_store *db)
 {
 	struct efi_signature_store *siglist;
 	struct efi_sig_data *sig_data;
 	void *hash = NULL;
 	size_t size = 0;
 	bool found = false;

 	EFI_PRINT("%s: Enter, %p, %p\n", __func__, regs, db);

 	if (!regs || !db || !db->sig_data_list)
 		goto out;

 	for (siglist = db; siglist; siglist = siglist->next) {
 		/* TODO: support other hash algorithms */
 		if (guidcmp(&siglist->sig_type, &efi_guid_sha256)) {
 			EFI_PRINT("Digest algorithm is not supported: %pUl\n",
 				  &siglist->sig_type);
 			break;
 		}

 		if (!efi_hash_regions(regs->reg, regs->num, &hash, &size)) {
 			EFI_PRINT("Digesting an image failed\n");
 			break;
 		}

 		for (sig_data = siglist->sig_data_list; sig_data;
 		     sig_data = sig_data->next) {
 #ifdef DEBUG
 			EFI_PRINT("Msg digest in database:\n");
 			print_hex_dump("    ", DUMP_PREFIX_OFFSET, 16, 1,
 				       sig_data->data, sig_data->size, false);
 #endif
 			if (sig_data->size == size &&
 			    !memcmp(sig_data->data, hash, size)) {
 				found = true;
 				free(hash);
 				goto out;
 			}
 		}

 		free(hash);
 		hash = NULL;
 	}

 out:
 	EFI_PRINT("%s: Exit, found: %d\n", __func__, found);
 	return found;
 }

 /**
  * efi_lookup_certificate - find a certificate within db
  * @msg:	Signature
  * @db:		Signature database
  *
  * Search signature database pointed to by @db and find a certificate
  * pointed to by @cert.
  *
  * Return:	true if found, false otherwise.
  */
 static bool efi_lookup_certificate(struct x509_certificate *cert,
 				   struct efi_signature_store *db)
 {
 	struct efi_signature_store *siglist;
 	struct efi_sig_data *sig_data;
 	struct image_region reg[1];
 	void *hash = NULL, *hash_tmp = NULL;
 	size_t size = 0;
 	bool found = false;

 	EFI_PRINT("%s: Enter, %p, %p\n", __func__, cert, db);

 	if (!cert || !db || !db->sig_data_list)
 		goto out;

 	/*
 	 * TODO: identify a certificate using sha256 digest
 	 * Is there any better way?
 	 */
 	/* calculate hash of TBSCertificate */
 	reg[0].data = cert->tbs;
 	reg[0].size = cert->tbs_size;
 	if (!efi_hash_regions(reg, 1, &hash, &size))
 		goto out;

 	EFI_PRINT("%s: searching for %s\n", __func__, cert->subject);
 	for (siglist = db; siglist; siglist = siglist->next) {
 		/* only with x509 certificate */
 		if (guidcmp(&siglist->sig_type, &efi_guid_cert_x509))
 			continue;

 		for (sig_data = siglist->sig_data_list; sig_data;
 		     sig_data = sig_data->next) {
 			struct x509_certificate *cert_tmp;

 			cert_tmp = x509_cert_parse(sig_data->data,
 						   sig_data->size);
 			if (IS_ERR_OR_NULL(cert_tmp))
 				continue;

 			EFI_PRINT("%s: against %s\n", __func__,
 				  cert_tmp->subject);
 			reg[0].data = cert_tmp->tbs;
 			reg[0].size = cert_tmp->tbs_size;
 			if (!efi_hash_regions(reg, 1, &hash_tmp, NULL))
 				goto out;

 			x509_free_certificate(cert_tmp);

 			if (!memcmp(hash, hash_tmp, size)) {
 				found = true;
 				goto out;
 			}
 		}
 	}
 out:
 	free(hash);
 	free(hash_tmp);

 	EFI_PRINT("%s: Exit, found: %d\n", __func__, found);
 	return found;
 }

 /**
  * efi_verify_certificate - verify certificate's signature with database
  * @signer:	Certificate
  * @db:		Signature database
  * @root:	Certificate to verify @signer
  *
  * Determine if certificate pointed to by @signer may be verified
  * by one of certificates in signature database pointed to by @db.
  *
  * Return:	true if certificate is verified, false otherwise.
  */
 static bool efi_verify_certificate(struct x509_certificate *signer,
 				   struct efi_signature_store *db,
 				   struct x509_certificate **root)
 {
 	struct efi_signature_store *siglist;
 	struct efi_sig_data *sig_data;
 	struct x509_certificate *cert;
 	bool verified = false;
 	int ret;

 	EFI_PRINT("%s: Enter, %p, %p\n", __func__, signer, db);

 	if (!signer || !db || !db->sig_data_list)
 		goto out;

 	for (siglist = db; siglist; siglist = siglist->next) {
 		/* only with x509 certificate */
 		if (guidcmp(&siglist->sig_type, &efi_guid_cert_x509))
 			continue;

 		for (sig_data = siglist->sig_data_list; sig_data;
 		     sig_data = sig_data->next) {
 			cert = x509_cert_parse(sig_data->data, sig_data->size);
 			if (IS_ERR_OR_NULL(cert)) {
 				EFI_PRINT("Cannot parse x509 certificate\n");
 				continue;
 			}

 			ret = public_key_verify_signature(cert->pub,
 							  signer->sig);
 			if (!ret) {
 				verified = true;
 				if (root)
 					*root = cert;
 				else
 					x509_free_certificate(cert);
 				goto out;
 			}
 			x509_free_certificate(cert);
 		}
 	}

 out:
 	EFI_PRINT("%s: Exit, verified: %d\n", __func__, verified);
 	return verified;
 }

 /**
  * efi_signature_check_revocation - check revocation with dbx
  * @sinfo:	Signer's info
  * @cert:	x509 certificate
  * @dbx:	Revocation signature database
  *
  * Search revocation signature database pointed to by @dbx and find
  * an entry matching to certificate pointed to by @cert.
  *
  * While this entry contains revocation time, we don't support timestamp
  * protocol at this time and any image will be unconditionally revoked
  * when this match occurs.
  *
  * Return:	true if check passed (not found), false otherwise.
  */
 static bool efi_signature_check_revocation(struct pkcs7_signed_info *sinfo,
 					   struct x509_certificate *cert,
 					   struct efi_signature_store *dbx)
 {
 	struct efi_signature_store *siglist;
 	struct efi_sig_data *sig_data;
 	struct image_region reg[1];
 	void *hash = NULL;
 	size_t size = 0;
 	time64_t revoc_time;
 	bool revoked = false;

 	EFI_PRINT("%s: Enter, %p, %p, %p\n", __func__, sinfo, cert, dbx);

 	if (!sinfo || !cert || !dbx || !dbx->sig_data_list)
 		goto out;

 	EFI_PRINT("Checking revocation against %s\n", cert->subject);
 	for (siglist = dbx; siglist; siglist = siglist->next) {
 		if (guidcmp(&siglist->sig_type, &efi_guid_cert_x509_sha256))
 			continue;

 		/* calculate hash of TBSCertificate */
 		reg[0].data = cert->tbs;
 		reg[0].size = cert->tbs_size;
 		if (!efi_hash_regions(reg, 1, &hash, &size))
 			goto out;

 		for (sig_data = siglist->sig_data_list; sig_data;
 		     sig_data = sig_data->next) {
 			/*
 			 * struct efi_cert_x509_sha256 {
 			 *	u8 tbs_hash[256/8];
 			 *	time64_t revocation_time;
 			 * };
 			 */
 #ifdef DEBUG
 			if (sig_data->size >= size) {
 				EFI_PRINT("hash in db:\n");
 				print_hex_dump("    ", DUMP_PREFIX_OFFSET,
 					       16, 1,
 					       sig_data->data, size, false);
 			}
 #endif
 			if ((sig_data->size < size + sizeof(time64_t)) ||
 			    memcmp(sig_data->data, hash, size))
 				continue;

 			memcpy(&revoc_time, sig_data->data + size,
 			       sizeof(revoc_time));
 			EFI_PRINT("revocation time: 0x%llx\n", revoc_time);
 			/*
 			 * TODO: compare signing timestamp in sinfo
 			 * with revocation time
 			 */

 			revoked = true;
 			free(hash);
 			goto out;
 		}
 		free(hash);
 		hash = NULL;
 	}
 out:
 	EFI_PRINT("%s: Exit, revoked: %d\n", __func__, revoked);
 	return !revoked;
 }

 /*
  * efi_signature_verify - verify signatures with db and dbx
  * @regs:	List of regions to be authenticated
  * @msg:	Signature
  * @db:		Signature database for trusted certificates
  * @dbx:	Revocation signature database
  *
  * All the signature pointed to by @msg against image pointed to by @regs
  * will be verified by signature database pointed to by @db and @dbx.
  *
  * Return:	true if verification for all signatures passed, false otherwise
  */
 bool efi_signature_verify(struct efi_image_regions *regs,
 			  struct pkcs7_message *msg,
 			  struct efi_signature_store *db,
 			  struct efi_signature_store *dbx)
 {
 	struct pkcs7_signed_info *sinfo;
 	struct x509_certificate *signer, *root;
 	bool verified = false;
 	int ret;

 	EFI_PRINT("%s: Enter, %p, %p, %p, %p\n", __func__, regs, msg, db, dbx);

 	if (!regs || !msg || !db || !db->sig_data_list)
 		goto out;

 	for (sinfo = msg->signed_infos; sinfo; sinfo = sinfo->next) {
 		EFI_PRINT("Signed Info: digest algo: %s, pkey algo: %s\n",
 			  sinfo->sig->hash_algo, sinfo->sig->pkey_algo);

 		/*
 		 * only for authenticated variable.
 		 *
 		 * If this function is called for image,
 		 * hash calculation will be done in
 		 * pkcs7_verify_one().
 		 */
 		if (!msg->data &&
 		    !efi_hash_regions(regs->reg, regs->num,
 				      (void **)&sinfo->sig->digest, NULL)) {
 			EFI_PRINT("Digesting an image failed\n");
 			goto out;
 		}

 		EFI_PRINT("Verifying certificate chain\n");
 		signer = NULL;
 		ret = pkcs7_verify_one(msg, sinfo, &signer);
 		if (ret == -ENOPKG)
 			continue;

 		if (ret < 0 || !signer)
 			goto out;

 		if (sinfo->blacklisted)
 			goto out;

 		EFI_PRINT("Verifying last certificate in chain\n");
 		if (signer->self_signed) {
 			if (efi_lookup_certificate(signer, db))
 				if (efi_signature_check_revocation(sinfo,
 								   signer, dbx))
 					break;
 		} else if (efi_verify_certificate(signer, db, &root)) {
 			bool check;

 			check = efi_signature_check_revocation(sinfo, root,
 							       dbx);
 			x509_free_certificate(root);
 			if (check)
 				break;
 		}

 		EFI_PRINT("Certificate chain didn't reach trusted CA\n");
 	}
 	if (sinfo)
 		verified = true;
 out:
 	EFI_PRINT("%s: Exit, verified: %d\n", __func__, verified);
 	return verified;
 }

 /**
  * efi_signature_check_signers - check revocation against all signers with dbx
  * @msg:	Signature
  * @dbx:	Revocation signature database
  *
  * Determine if none of signers' certificates in @msg are revoked
  * by signature database pointed to by @dbx.
  *
  * Return:	true if all signers passed, false otherwise.
  */
 bool efi_signature_check_signers(struct pkcs7_message *msg,
 				 struct efi_signature_store *dbx)
 {
 	struct pkcs7_signed_info *sinfo;
 	bool revoked = false;

 	EFI_PRINT("%s: Enter, %p, %p\n", __func__, msg, dbx);

 	if (!msg || !dbx)
 		goto out;

 	for (sinfo = msg->signed_infos; sinfo; sinfo = sinfo->next) {
 		if (sinfo->signer &&
 		    !efi_signature_check_revocation(sinfo, sinfo->signer,
 						    dbx)) {
 			revoked = true;
 			break;
 		}
 	}
 out:
 	EFI_PRINT("%s: Exit, revoked: %d\n", __func__, revoked);
 	return !revoked;
 }

 /**
  * efi_image_region_add() - add an entry of region
  * @regs:	Pointer to array of regions
  * @start:	Start address of region (included)
  * @end:	End address of region (excluded)
  * @nocheck:	flag against overlapped regions
  *
  * Take one entry of region [@start, @end[ and insert it into the list.
  *
  * * If @nocheck is false, the list will be sorted ascending by address.
  *   Overlapping entries will not be allowed.
  *
  * * If @nocheck is true, the list will be sorted ascending by sequence
  *   of adding the entries. Overlapping is allowed.
  *
  * Return:	status code
  */
 efi_status_t efi_image_region_add(struct efi_image_regions *regs,
 				  const void *start, const void *end,
 				  int nocheck)
 {
 	struct image_region *reg;
 	int i, j;

 	if (regs->num >= regs->max) {
 		EFI_PRINT("%s: no more room for regions\n", __func__);
 		return EFI_OUT_OF_RESOURCES;
 	}

 	if (end < start)
 		return EFI_INVALID_PARAMETER;

 	for (i = 0; i < regs->num; i++) {
 		reg = &regs->reg[i];
 		if (nocheck)
 			continue;

 		/* new data after registered region */
 		if (start >= reg->data + reg->size)
 			continue;

 		/* new data preceding registered region */
 		if (end <= reg->data) {
 			for (j = regs->num - 1; j >= i; j--)
 				memcpy(&regs->reg[j + 1], &regs->reg[j],
 				       sizeof(*reg));
 			break;
 		}

 		/* new data overlapping registered region */
 		EFI_PRINT("%s: new region already part of another\n", __func__);
 		return EFI_INVALID_PARAMETER;
 	}

 	reg = &regs->reg[i];
 	reg->data = start;
 	reg->size = end - start;
 	regs->num++;

 	return EFI_SUCCESS;
 }

 /**
  * efi_sigstore_free - free signature store
  * @sigstore:	Pointer to signature store structure
  *
  * Feee all the memories held in signature store and itself,
  * which were allocated by efi_sigstore_parse_sigdb().
  */
 void efi_sigstore_free(struct efi_signature_store *sigstore)
 {
 	struct efi_signature_store *sigstore_next;
 	struct efi_sig_data *sig_data, *sig_data_next;

 	while (sigstore) {
 		sigstore_next = sigstore->next;

 		sig_data = sigstore->sig_data_list;
 		while (sig_data) {
 			sig_data_next = sig_data->next;
 			free(sig_data->data);
 			free(sig_data);
 			sig_data = sig_data_next;
 		}

 		free(sigstore);
 		sigstore = sigstore_next;
 	}
 }

 /**
  * efi_sigstore_parse_siglist - parse a signature list
  * @name:	Pointer to signature list
  *
  * Parse signature list and instantiate a signature store structure.
  * Signature database is a simple concatenation of one or more
  * signature list(s).
  *
  * Return:	Pointer to signature store on success, NULL on error
  */
 static struct efi_signature_store *
 efi_sigstore_parse_siglist(struct efi_signature_list *esl)
 {
 	struct efi_signature_store *siglist = NULL;
 	struct efi_sig_data *sig_data, *sig_data_next;
 	struct efi_signature_data *esd;
 	size_t left;

 	/*
 	 * UEFI specification defines certificate types:
 	 *   for non-signed images,
 	 *	EFI_CERT_SHA256_GUID
 	 *	EFI_CERT_RSA2048_GUID
 	 *	EFI_CERT_RSA2048_SHA256_GUID
 	 *	EFI_CERT_SHA1_GUID
 	 *	EFI_CERT_RSA2048_SHA_GUID
 	 *	EFI_CERT_SHA224_GUID
 	 *	EFI_CERT_SHA384_GUID
 	 *	EFI_CERT_SHA512_GUID
 	 *
 	 *   for signed images,
 	 *	EFI_CERT_X509_GUID
 	 *	NOTE: Each certificate will normally be in a separate
 	 *	EFI_SIGNATURE_LIST as the size may vary depending on
 	 *	its algo's.
 	 *
 	 *   for timestamp revocation of certificate,
 	 *	EFI_CERT_X509_SHA512_GUID
 	 *	EFI_CERT_X509_SHA256_GUID
 	 *	EFI_CERT_X509_SHA384_GUID
 	 */

 	if (esl->signature_list_size
 			<= (sizeof(*esl) + esl->signature_header_size)) {
 		EFI_PRINT("Siglist in wrong format\n");
 		return NULL;
 	}

 	/* Create a head */
 	siglist = calloc(sizeof(*siglist), 1);
 	if (!siglist) {
 		EFI_PRINT("Out of memory\n");
 		goto err;
 	}
 	memcpy(&siglist->sig_type, &esl->signature_type, sizeof(efi_guid_t));

 	/* Go through the list */
 	sig_data_next = NULL;
 	left = esl->signature_list_size
 			- (sizeof(*esl) + esl->signature_header_size);
 	esd = (struct efi_signature_data *)
 			((u8 *)esl + sizeof(*esl) + esl->signature_header_size);

 	while (left > 0) {
 		/* Signature must exist if there is remaining data. */
 		if (left < esl->signature_size) {
 			EFI_PRINT("Certificate is too small\n");
 			goto err;
 		}

 		sig_data = calloc(esl->signature_size
 					- sizeof(esd->signature_owner), 1);
 		if (!sig_data) {
 			EFI_PRINT("Out of memory\n");
 			goto err;
 		}

 		/* Append signature data */
 		memcpy(&sig_data->owner, &esd->signature_owner,
 		       sizeof(efi_guid_t));
 		sig_data->size = esl->signature_size
 					- sizeof(esd->signature_owner);
 		sig_data->data = malloc(sig_data->size);
 		if (!sig_data->data) {
 			EFI_PRINT("Out of memory\n");
 			goto err;
 		}
 		memcpy(sig_data->data, esd->signature_data, sig_data->size);

 		sig_data->next = sig_data_next;
 		sig_data_next = sig_data;

 		/* Next */
 		esd = (struct efi_signature_data *)
 				((u8 *)esd + esl->signature_size);
 		left -= esl->signature_size;
 	}
 	siglist->sig_data_list = sig_data_next;

 	return siglist;

 err:
 	efi_sigstore_free(siglist);

 	return NULL;
 }

 /**
  * efi_sigstore_parse_sigdb - parse a signature database variable
  * @name:	Variable's name
  *
  * Read in a value of signature database variable pointed to by
  * @name, parse it and instantiate a signature store structure.
  *
  * Return:	Pointer to signature store on success, NULL on error
  */
 struct efi_signature_store *efi_sigstore_parse_sigdb(u16 *name)
 {
 	struct efi_signature_store *sigstore = NULL, *siglist;
 	struct efi_signature_list *esl;
 	const efi_guid_t *vendor;
 	void *db;
 	efi_uintn_t db_size;
 	efi_status_t ret;

 	if (!u16_strcmp(name, L"PK") || !u16_strcmp(name, L"KEK")) {
 		vendor = &efi_global_variable_guid;
 	} else if (!u16_strcmp(name, L"db") || !u16_strcmp(name, L"dbx")) {
 		vendor = &efi_guid_image_security_database;
 	} else {
 		EFI_PRINT("unknown signature database, %ls\n", name);
 		return NULL;
 	}

 	/* retrieve variable data */
 	db_size = 0;
 	ret = EFI_CALL(efi_get_variable(name, vendor, NULL, &db_size, NULL));
 	if (ret == EFI_NOT_FOUND) {
 		EFI_PRINT("variable, %ls, not found\n", name);
 		sigstore = calloc(sizeof(*sigstore), 1);
 		return sigstore;
 	} else if (ret != EFI_BUFFER_TOO_SMALL) {
 		EFI_PRINT("Getting variable, %ls, failed\n", name);
 		return NULL;
 	}

 	db = malloc(db_size);
 	if (!db) {
 		EFI_PRINT("Out of memory\n");
 		return NULL;
 	}

 	ret = EFI_CALL(efi_get_variable(name, vendor, NULL, &db_size, db));
 	if (ret != EFI_SUCCESS) {
 		EFI_PRINT("Getting variable, %ls, failed\n", name);
 		goto err;
 	}

 	/* Parse siglist list */
 	esl = db;
 	while (db_size > 0) {
 		/* List must exist if there is remaining data. */
 		if (db_size < sizeof(*esl)) {
 			EFI_PRINT("variable, %ls, in wrong format\n", name);
 			goto err;
 		}

 		if (db_size < esl->signature_list_size) {
 			EFI_PRINT("variable, %ls, in wrong format\n", name);
 			goto err;
 		}

 		/* Parse a single siglist. */
 		siglist = efi_sigstore_parse_siglist(esl);
 		if (!siglist) {
 			EFI_PRINT("Parsing signature list of %ls failed\n",
 				  name);
 			goto err;
 		}

 		/* Append siglist */
 		siglist->next = sigstore;
 		sigstore = siglist;

 		/* Next */
 		db_size -= esl->signature_list_size;
 		esl = (void *)esl + esl->signature_list_size;
 	}
 	free(db);

 	return sigstore;

 err:
 	efi_sigstore_free(sigstore);
 	free(db);

 	return NULL;
 }
 #endif /* CONFIG_EFI_SECURE_BOOT */
	// SPDX-License-Identifier: GPL-2.0+
	/*
	* Copyright (c) 2018 Patrick Wildt <patrick@blueri.se>
	* Copyright (c) 2019 Linaro Limited, Author: AKASHI Takahiro
	*/

	#include <common.h>
	#include <charset.h>
	#include <efi_loader.h>
	#include <image.h>
	#include <hexdump.h>
	#include <malloc.h>
	#include <crypto/pkcs7.h>
	#include <crypto/pkcs7_parser.h>
	#include <crypto/public_key.h>
	#include <linux/compat.h>
	#include <linux/oid_registry.h>
	#include <u-boot/rsa.h>
	#include <u-boot/sha256.h>

	const efi_guid_t efi_guid_image_security_database =
	EFI_IMAGE_SECURITY_DATABASE_GUID;
	const efi_guid_t efi_guid_sha256 = EFI_CERT_SHA256_GUID;
	const efi_guid_t efi_guid_cert_rsa2048 = EFI_CERT_RSA2048_GUID;
	const efi_guid_t efi_guid_cert_x509 = EFI_CERT_X509_GUID;
	const efi_guid_t efi_guid_cert_x509_sha256 = EFI_CERT_X509_SHA256_GUID;
	const efi_guid_t efi_guid_cert_type_pkcs7 = EFI_CERT_TYPE_PKCS7_GUID;

	#ifdef CONFIG_EFI_SECURE_BOOT

	/**
	* efi_hash_regions - calculate a hash value
	* @regs: Array of regions
	* @count: Number of regions
	* @hash: Pointer to a pointer to buffer holding a hash value
	* @size: Size of buffer to be returned
	*
	* Calculate a sha256 value of @regs and return a value in @hash.
	*
	* Return: true on success, false on error
	*/
	static bool efi_hash_regions(struct image_region *regs, int count,
	void *hash, size_t size)
	{
	if (!*hash) {
	*hash = calloc(1, SHA256_SUM_LEN);
	if (!*hash) {
	EFI_PRINT("Out of memory\n");
	return false;
	}
	}
	if (size)
	*size = SHA256_SUM_LEN;

	hash_calculate("sha256", regs, count, *hash);
	#ifdef DEBUG
	EFI_PRINT("hash calculated:\n");
	print_hex_dump(" ", DUMP_PREFIX_OFFSET, 16, 1,
	*hash, SHA256_SUM_LEN, false);
	#endif

	return true;
	}

	/**
	* efi_signature_lookup_digest - search for an image's digest in sigdb
	* @regs: List of regions to be authenticated
	* @db: Signature database for trusted certificates
	*
	* A message digest of image pointed to by @regs is calculated and
	* its hash value is compared to entries in signature database pointed
	* to by @db.
	*
	* Return: true if found, false if not
	*/
	bool efi_signature_lookup_digest(struct efi_image_regions *regs,
	struct efi_signature_store *db)
	{
	struct efi_signature_store *siglist;
	struct efi_sig_data *sig_data;
	void *hash = NULL;
	size_t size = 0;
	bool found = false;

	EFI_PRINT("%s: Enter, %p, %p\n", __func__, regs, db);

	if (!regs \|\| !db \|\| !db->sig_data_list)
	goto out;

	for (siglist = db; siglist; siglist = siglist->next) {
	/* TODO: support other hash algorithms */
	if (guidcmp(&siglist->sig_type, &efi_guid_sha256)) {
	EFI_PRINT("Digest algorithm is not supported: %pUl\n",
	&siglist->sig_type);
	break;
	}

	if (!efi_hash_regions(regs->reg, regs->num, &hash, &size)) {
	EFI_PRINT("Digesting an image failed\n");
	break;
	}

	for (sig_data = siglist->sig_data_list; sig_data;
	sig_data = sig_data->next) {
	#ifdef DEBUG
	EFI_PRINT("Msg digest in database:\n");
	print_hex_dump(" ", DUMP_PREFIX_OFFSET, 16, 1,
	sig_data->data, sig_data->size, false);
	#endif
	if (sig_data->size == size &&
	!memcmp(sig_data->data, hash, size)) {
	found = true;
	free(hash);
	goto out;
	}
	}

	free(hash);
	hash = NULL;
	}

	out:
	EFI_PRINT("%s: Exit, found: %d\n", __func__, found);
	return found;
	}

	/**
	* efi_lookup_certificate - find a certificate within db
	* @msg: Signature
	* @db: Signature database
	*
	* Search signature database pointed to by @db and find a certificate
	* pointed to by @cert.
	*
	* Return: true if found, false otherwise.
	*/
	static bool efi_lookup_certificate(struct x509_certificate *cert,
	struct efi_signature_store *db)
	{
	struct efi_signature_store *siglist;
	struct efi_sig_data *sig_data;
	struct image_region reg[1];
	void hash = NULL, hash_tmp = NULL;
	size_t size = 0;
	bool found = false;

	EFI_PRINT("%s: Enter, %p, %p\n", __func__, cert, db);

	if (!cert \|\| !db \|\| !db->sig_data_list)
	goto out;

	/*
	* TODO: identify a certificate using sha256 digest
	* Is there any better way?
	*/
	/* calculate hash of TBSCertificate */
	reg[0].data = cert->tbs;
	reg[0].size = cert->tbs_size;
	if (!efi_hash_regions(reg, 1, &hash, &size))
	goto out;

	EFI_PRINT("%s: searching for %s\n", __func__, cert->subject);
	for (siglist = db; siglist; siglist = siglist->next) {
	/* only with x509 certificate */
	if (guidcmp(&siglist->sig_type, &efi_guid_cert_x509))
	continue;

	for (sig_data = siglist->sig_data_list; sig_data;
	sig_data = sig_data->next) {
	struct x509_certificate *cert_tmp;

	cert_tmp = x509_cert_parse(sig_data->data,
	sig_data->size);
	if (IS_ERR_OR_NULL(cert_tmp))
	continue;

	EFI_PRINT("%s: against %s\n", __func__,
	cert_tmp->subject);
	reg[0].data = cert_tmp->tbs;
	reg[0].size = cert_tmp->tbs_size;
	if (!efi_hash_regions(reg, 1, &hash_tmp, NULL))
	goto out;

	x509_free_certificate(cert_tmp);

	if (!memcmp(hash, hash_tmp, size)) {
	found = true;
	goto out;
	}
	}
	}
	out:
	free(hash);
	free(hash_tmp);

	EFI_PRINT("%s: Exit, found: %d\n", __func__, found);
	return found;
	}

	/**
	* efi_verify_certificate - verify certificate's signature with database
	* @signer: Certificate
	* @db: Signature database
	* @root: Certificate to verify @signer
	*
	* Determine if certificate pointed to by @signer may be verified
	* by one of certificates in signature database pointed to by @db.
	*
	* Return: true if certificate is verified, false otherwise.
	*/
	static bool efi_verify_certificate(struct x509_certificate *signer,
	struct efi_signature_store *db,
	struct x509_certificate **root)
	{
	struct efi_signature_store *siglist;
	struct efi_sig_data *sig_data;
	struct x509_certificate *cert;
	bool verified = false;
	int ret;

	EFI_PRINT("%s: Enter, %p, %p\n", __func__, signer, db);

	if (!signer \|\| !db \|\| !db->sig_data_list)
	goto out;

	for (siglist = db; siglist; siglist = siglist->next) {
	/* only with x509 certificate */
	if (guidcmp(&siglist->sig_type, &efi_guid_cert_x509))
	continue;

	for (sig_data = siglist->sig_data_list; sig_data;
	sig_data = sig_data->next) {
	cert = x509_cert_parse(sig_data->data, sig_data->size);
	if (IS_ERR_OR_NULL(cert)) {
	EFI_PRINT("Cannot parse x509 certificate\n");
	continue;
	}

	ret = public_key_verify_signature(cert->pub,
	signer->sig);
	if (!ret) {
	verified = true;
	if (root)
	*root = cert;
	else
	x509_free_certificate(cert);
	goto out;
	}
	x509_free_certificate(cert);
	}
	}

	out:
	EFI_PRINT("%s: Exit, verified: %d\n", __func__, verified);
	return verified;
	}

	/**
	* efi_signature_check_revocation - check revocation with dbx
	* @sinfo: Signer's info
	* @cert: x509 certificate
	* @dbx: Revocation signature database
	*
	* Search revocation signature database pointed to by @dbx and find
	* an entry matching to certificate pointed to by @cert.
	*
	* While this entry contains revocation time, we don't support timestamp
	* protocol at this time and any image will be unconditionally revoked
	* when this match occurs.
	*
	* Return: true if check passed (not found), false otherwise.
	*/
	static bool efi_signature_check_revocation(struct pkcs7_signed_info *sinfo,
	struct x509_certificate *cert,
	struct efi_signature_store *dbx)
	{
	struct efi_signature_store *siglist;
	struct efi_sig_data *sig_data;
	struct image_region reg[1];
	void *hash = NULL;
	size_t size = 0;
	time64_t revoc_time;
	bool revoked = false;

	EFI_PRINT("%s: Enter, %p, %p, %p\n", __func__, sinfo, cert, dbx);

	if (!sinfo \|\| !cert \|\| !dbx \|\| !dbx->sig_data_list)
	goto out;

	EFI_PRINT("Checking revocation against %s\n", cert->subject);
	for (siglist = dbx; siglist; siglist = siglist->next) {
	if (guidcmp(&siglist->sig_type, &efi_guid_cert_x509_sha256))
	continue;

	/* calculate hash of TBSCertificate */
	reg[0].data = cert->tbs;
	reg[0].size = cert->tbs_size;
	if (!efi_hash_regions(reg, 1, &hash, &size))
	goto out;

	for (sig_data = siglist->sig_data_list; sig_data;
	sig_data = sig_data->next) {
	/*
	* struct efi_cert_x509_sha256 {
	* u8 tbs_hash[256/8];
	* time64_t revocation_time;
	* };
	*/
	#ifdef DEBUG
	if (sig_data->size >= size) {
	EFI_PRINT("hash in db:\n");
	print_hex_dump(" ", DUMP_PREFIX_OFFSET,
	16, 1,
	sig_data->data, size, false);
	}
	#endif
	if ((sig_data->size < size + sizeof(time64_t)) \|\|
	memcmp(sig_data->data, hash, size))
	continue;

	memcpy(&revoc_time, sig_data->data + size,
	sizeof(revoc_time));
	EFI_PRINT("revocation time: 0x%llx\n", revoc_time);
	/*
	* TODO: compare signing timestamp in sinfo
	* with revocation time
	*/

	revoked = true;
	free(hash);
	goto out;
	}
	free(hash);
	hash = NULL;
	}
	out:
	EFI_PRINT("%s: Exit, revoked: %d\n", __func__, revoked);
	return !revoked;
	}

	/*
	* efi_signature_verify - verify signatures with db and dbx
	* @regs: List of regions to be authenticated
	* @msg: Signature
	* @db: Signature database for trusted certificates
	* @dbx: Revocation signature database
	*
	* All the signature pointed to by @msg against image pointed to by @regs
	* will be verified by signature database pointed to by @db and @dbx.
	*
	* Return: true if verification for all signatures passed, false otherwise
	*/
	bool efi_signature_verify(struct efi_image_regions *regs,
	struct pkcs7_message *msg,
	struct efi_signature_store *db,
	struct efi_signature_store *dbx)
	{
	struct pkcs7_signed_info *sinfo;
	struct x509_certificate signer, root;
	bool verified = false;
	int ret;

	EFI_PRINT("%s: Enter, %p, %p, %p, %p\n", __func__, regs, msg, db, dbx);

	if (!regs \|\| !msg \|\| !db \|\| !db->sig_data_list)
	goto out;

	for (sinfo = msg->signed_infos; sinfo; sinfo = sinfo->next) {
	EFI_PRINT("Signed Info: digest algo: %s, pkey algo: %s\n",
	sinfo->sig->hash_algo, sinfo->sig->pkey_algo);

	/*
	* only for authenticated variable.
	*
	* If this function is called for image,
	* hash calculation will be done in
	* pkcs7_verify_one().
	*/
	if (!msg->data &&
	!efi_hash_regions(regs->reg, regs->num,
	(void **)&sinfo->sig->digest, NULL)) {
	EFI_PRINT("Digesting an image failed\n");
	goto out;
	}

	EFI_PRINT("Verifying certificate chain\n");
	signer = NULL;
	ret = pkcs7_verify_one(msg, sinfo, &signer);
	if (ret == -ENOPKG)
	continue;

	if (ret < 0 \|\| !signer)
	goto out;

	if (sinfo->blacklisted)
	goto out;

	EFI_PRINT("Verifying last certificate in chain\n");
	if (signer->self_signed) {
	if (efi_lookup_certificate(signer, db))
	if (efi_signature_check_revocation(sinfo,
	signer, dbx))
	break;
	} else if (efi_verify_certificate(signer, db, &root)) {
	bool check;

	check = efi_signature_check_revocation(sinfo, root,
	dbx);
	x509_free_certificate(root);
	if (check)
	break;
	}

	EFI_PRINT("Certificate chain didn't reach trusted CA\n");
	}
	if (sinfo)
	verified = true;
	out:
	EFI_PRINT("%s: Exit, verified: %d\n", __func__, verified);
	return verified;
	}

	/**
	* efi_signature_check_signers - check revocation against all signers with dbx
	* @msg: Signature
	* @dbx: Revocation signature database
	*
	* Determine if none of signers' certificates in @msg are revoked
	* by signature database pointed to by @dbx.
	*
	* Return: true if all signers passed, false otherwise.
	*/
	bool efi_signature_check_signers(struct pkcs7_message *msg,
	struct efi_signature_store *dbx)
	{
	struct pkcs7_signed_info *sinfo;
	bool revoked = false;

	EFI_PRINT("%s: Enter, %p, %p\n", __func__, msg, dbx);

	if (!msg \|\| !dbx)
	goto out;

	for (sinfo = msg->signed_infos; sinfo; sinfo = sinfo->next) {
	if (sinfo->signer &&
	!efi_signature_check_revocation(sinfo, sinfo->signer,
	dbx)) {
	revoked = true;
	break;
	}
	}
	out:
	EFI_PRINT("%s: Exit, revoked: %d\n", __func__, revoked);
	return !revoked;
	}

	/**
	* efi_image_region_add() - add an entry of region
	* @regs: Pointer to array of regions
	* @start: Start address of region (included)
	* @end: End address of region (excluded)
	* @nocheck: flag against overlapped regions
	*
	* Take one entry of region [@start, @end[ and insert it into the list.
	*
	* * If @nocheck is false, the list will be sorted ascending by address.
	* Overlapping entries will not be allowed.
	*
	* * If @nocheck is true, the list will be sorted ascending by sequence
	* of adding the entries. Overlapping is allowed.
	*
	* Return: status code
	*/
	efi_status_t efi_image_region_add(struct efi_image_regions *regs,
	const void start, const void end,
	int nocheck)
	{
	struct image_region *reg;
	int i, j;

	if (regs->num >= regs->max) {
	EFI_PRINT("%s: no more room for regions\n", __func__);
	return EFI_OUT_OF_RESOURCES;
	}

	if (end < start)
	return EFI_INVALID_PARAMETER;

	for (i = 0; i < regs->num; i++) {
	reg = &regs->reg[i];
	if (nocheck)
	continue;

	/* new data after registered region */
	if (start >= reg->data + reg->size)
	continue;

	/* new data preceding registered region */
	if (end <= reg->data) {
	for (j = regs->num - 1; j >= i; j--)
	memcpy(&regs->reg[j + 1], &regs->reg[j],
	sizeof(*reg));
	break;
	}

	/* new data overlapping registered region */
	EFI_PRINT("%s: new region already part of another\n", __func__);
	return EFI_INVALID_PARAMETER;
	}

	reg = &regs->reg[i];
	reg->data = start;
	reg->size = end - start;
	regs->num++;

	return EFI_SUCCESS;
	}

	/**
	* efi_sigstore_free - free signature store
	* @sigstore: Pointer to signature store structure
	*
	* Feee all the memories held in signature store and itself,
	* which were allocated by efi_sigstore_parse_sigdb().
	*/
	void efi_sigstore_free(struct efi_signature_store *sigstore)
	{
	struct efi_signature_store *sigstore_next;
	struct efi_sig_data sig_data, sig_data_next;

	while (sigstore) {
	sigstore_next = sigstore->next;

	sig_data = sigstore->sig_data_list;
	while (sig_data) {
	sig_data_next = sig_data->next;
	free(sig_data->data);
	free(sig_data);
	sig_data = sig_data_next;
	}

	free(sigstore);
	sigstore = sigstore_next;
	}
	}

	/**
	* efi_sigstore_parse_siglist - parse a signature list
	* @name: Pointer to signature list
	*
	* Parse signature list and instantiate a signature store structure.
	* Signature database is a simple concatenation of one or more
	* signature list(s).
	*
	* Return: Pointer to signature store on success, NULL on error
	*/
	static struct efi_signature_store *
	efi_sigstore_parse_siglist(struct efi_signature_list *esl)
	{
	struct efi_signature_store *siglist = NULL;
	struct efi_sig_data sig_data, sig_data_next;
	struct efi_signature_data *esd;
	size_t left;

	/*
	* UEFI specification defines certificate types:
	* for non-signed images,
	* EFI_CERT_SHA256_GUID
	* EFI_CERT_RSA2048_GUID
	* EFI_CERT_RSA2048_SHA256_GUID
	* EFI_CERT_SHA1_GUID
	* EFI_CERT_RSA2048_SHA_GUID
	* EFI_CERT_SHA224_GUID
	* EFI_CERT_SHA384_GUID
	* EFI_CERT_SHA512_GUID
	*
	* for signed images,
	* EFI_CERT_X509_GUID
	* NOTE: Each certificate will normally be in a separate
	* EFI_SIGNATURE_LIST as the size may vary depending on
	* its algo's.
	*
	* for timestamp revocation of certificate,
	* EFI_CERT_X509_SHA512_GUID
	* EFI_CERT_X509_SHA256_GUID
	* EFI_CERT_X509_SHA384_GUID
	*/

	if (esl->signature_list_size
	<= (sizeof(*esl) + esl->signature_header_size)) {
	EFI_PRINT("Siglist in wrong format\n");
	return NULL;
	}

	/* Create a head */
	siglist = calloc(sizeof(*siglist), 1);
	if (!siglist) {
	EFI_PRINT("Out of memory\n");
	goto err;
	}
	memcpy(&siglist->sig_type, &esl->signature_type, sizeof(efi_guid_t));

	/* Go through the list */
	sig_data_next = NULL;
	left = esl->signature_list_size
	- (sizeof(*esl) + esl->signature_header_size);
	esd = (struct efi_signature_data *)
	((u8 )esl + sizeof(esl) + esl->signature_header_size);

	while (left > 0) {
	/* Signature must exist if there is remaining data. */
	if (left < esl->signature_size) {
	EFI_PRINT("Certificate is too small\n");
	goto err;
	}

	sig_data = calloc(esl->signature_size
	- sizeof(esd->signature_owner), 1);
	if (!sig_data) {
	EFI_PRINT("Out of memory\n");
	goto err;
	}

	/* Append signature data */
	memcpy(&sig_data->owner, &esd->signature_owner,
	sizeof(efi_guid_t));
	sig_data->size = esl->signature_size
	- sizeof(esd->signature_owner);
	sig_data->data = malloc(sig_data->size);
	if (!sig_data->data) {
	EFI_PRINT("Out of memory\n");
	goto err;
	}
	memcpy(sig_data->data, esd->signature_data, sig_data->size);

	sig_data->next = sig_data_next;
	sig_data_next = sig_data;

	/* Next */
	esd = (struct efi_signature_data *)
	((u8 *)esd + esl->signature_size);
	left -= esl->signature_size;
	}
	siglist->sig_data_list = sig_data_next;

	return siglist;

	err:
	efi_sigstore_free(siglist);

	return NULL;
	}

	/**
	* efi_sigstore_parse_sigdb - parse a signature database variable
	* @name: Variable's name
	*
	* Read in a value of signature database variable pointed to by
	* @name, parse it and instantiate a signature store structure.
	*
	* Return: Pointer to signature store on success, NULL on error
	*/
	struct efi_signature_store efi_sigstore_parse_sigdb(u16 name)
	{
	struct efi_signature_store sigstore = NULL, siglist;
	struct efi_signature_list *esl;
	const efi_guid_t *vendor;
	void *db;
	efi_uintn_t db_size;
	efi_status_t ret;

	if (!u16_strcmp(name, L"PK") \|\| !u16_strcmp(name, L"KEK")) {
	vendor = &efi_global_variable_guid;
	} else if (!u16_strcmp(name, L"db") \|\| !u16_strcmp(name, L"dbx")) {
	vendor = &efi_guid_image_security_database;
	} else {
	EFI_PRINT("unknown signature database, %ls\n", name);
	return NULL;
	}

	/* retrieve variable data */
	db_size = 0;
	ret = EFI_CALL(efi_get_variable(name, vendor, NULL, &db_size, NULL));
	if (ret == EFI_NOT_FOUND) {
	EFI_PRINT("variable, %ls, not found\n", name);
	sigstore = calloc(sizeof(*sigstore), 1);
	return sigstore;
	} else if (ret != EFI_BUFFER_TOO_SMALL) {
	EFI_PRINT("Getting variable, %ls, failed\n", name);
	return NULL;
	}

	db = malloc(db_size);
	if (!db) {
	EFI_PRINT("Out of memory\n");
	return NULL;
	}

	ret = EFI_CALL(efi_get_variable(name, vendor, NULL, &db_size, db));
	if (ret != EFI_SUCCESS) {
	EFI_PRINT("Getting variable, %ls, failed\n", name);
	goto err;
	}

	/* Parse siglist list */
	esl = db;
	while (db_size > 0) {
	/* List must exist if there is remaining data. */
	if (db_size < sizeof(*esl)) {
	EFI_PRINT("variable, %ls, in wrong format\n", name);
	goto err;
	}

	if (db_size < esl->signature_list_size) {
	EFI_PRINT("variable, %ls, in wrong format\n", name);
	goto err;
	}

	/* Parse a single siglist. */
	siglist = efi_sigstore_parse_siglist(esl);
	if (!siglist) {
	EFI_PRINT("Parsing signature list of %ls failed\n",
	name);
	goto err;
	}

	/* Append siglist */
	siglist->next = sigstore;
	sigstore = siglist;

	/* Next */
	db_size -= esl->signature_list_size;
	esl = (void *)esl + esl->signature_list_size;
	}
	free(db);

	return sigstore;

	err:
	efi_sigstore_free(sigstore);
	free(db);

	return NULL;
	}
	#endif /* CONFIG_EFI_SECURE_BOOT */