drivers/auth/auth_mod.c - filogic/atf - Gitiles

 /*
  * Copyright (c) 2015-2023, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */

 #include <assert.h>
 #include <stdint.h>
 #include <string.h>

 #include <platform_def.h>

 #include <common/debug.h>
 #include <common/tbbr/cot_def.h>
 #include <drivers/auth/auth_common.h>
 #include <drivers/auth/auth_mod.h>
 #include <drivers/auth/crypto_mod.h>
 #include <drivers/auth/img_parser_mod.h>
 #include <drivers/fwu/fwu.h>
 #include <lib/fconf/fconf_tbbr_getter.h>
 #include <plat/common/platform.h>

 /* ASN.1 tags */
 #define ASN1_INTEGER                 0x02

 #define return_if_error(rc) \
 	do { \
 		if (rc != 0) { \
 			return rc; \
 		} \
 	} while (0)

 #pragma weak plat_set_nv_ctr2
 #pragma weak plat_convert_pk

 static int cmp_auth_param_type_desc(const auth_param_type_desc_t *a,
 		const auth_param_type_desc_t *b)
 {
 	if ((a->type == b->type) && (a->cookie == b->cookie)) {
 		return 0;
 	}
 	return 1;
 }

 /*
  * This function obtains the requested authentication parameter data from the
  * information extracted from the parent image after its authentication.
  */
 static int auth_get_param(const auth_param_type_desc_t *param_type_desc,
 			  const auth_img_desc_t *img_desc,
 			  void **param, unsigned int *len)
 {
 	int i;

 	if (img_desc->authenticated_data == NULL)
 		return 1;

 	for (i = 0 ; i < COT_MAX_VERIFIED_PARAMS ; i++) {
 		if (0 == cmp_auth_param_type_desc(param_type_desc,
 				img_desc->authenticated_data[i].type_desc)) {
 			*param = img_desc->authenticated_data[i].data.ptr;
 			*len = img_desc->authenticated_data[i].data.len;
 			return 0;
 		}
 	}

 	return 1;
 }

 /*
  * Authenticate an image by matching the data hash
  *
  * This function implements 'AUTH_METHOD_HASH'. To authenticate an image using
  * this method, the image must contain:
  *
  *   - The data to calculate the hash from
  *
  * The parent image must contain:
  *
  *   - The hash to be matched with (including hash algorithm)
  *
  * For a successful authentication, both hashes must match. The function calls
  * the crypto-module to check this matching.
  *
  * Parameters:
  *   param: parameters to perform the hash authentication
  *   img_desc: pointer to image descriptor so we can know the image type
  *             and parent image
  *   img: pointer to image in memory
  *   img_len: length of image (in bytes)
  *
  * Return:
  *   0 = success, Otherwise = error
  */
 static int auth_hash(const auth_method_param_hash_t *param,
 		     const auth_img_desc_t *img_desc,
 		     void *img, unsigned int img_len)
 {
 	void *data_ptr, *hash_der_ptr;
 	unsigned int data_len, hash_der_len;
 	int rc = 0;

 	/* Get the hash from the parent image. This hash will be DER encoded
 	 * and contain the hash algorithm */
 	rc = auth_get_param(param->hash, img_desc->parent,
 			&hash_der_ptr, &hash_der_len);
 	return_if_error(rc);

 	/* Get the data to be hashed from the current image */
 	rc = img_parser_get_auth_param(img_desc->img_type, param->data,
 			img, img_len, &data_ptr, &data_len);
 	return_if_error(rc);

 	/* Ask the crypto module to verify this hash */
 	rc = crypto_mod_verify_hash(data_ptr, data_len,
 				    hash_der_ptr, hash_der_len);

 	return rc;
 }

 /*
  * Authenticate by digital signature
  *
  * This function implements 'AUTH_METHOD_SIG'. To authenticate an image using
  * this method, the image must contain:
  *
  *   - Data to be signed
  *   - Signature
  *   - Signature algorithm
  *
  * We rely on the image parser module to extract this data from the image.
  * The parent image must contain:
  *
  *   - Public key (or a hash of it)
  *
  * If the parent image contains only a hash of the key, we will try to obtain
  * the public key from the image itself (i.e. self-signed certificates). In that
  * case, the signature verification is considered just an integrity check and
  * the authentication is established by calculating the hash of the key and
  * comparing it with the hash obtained from the parent.
  *
  * If the image has no parent (NULL), it means it has to be authenticated using
  * the ROTPK stored in the platform. Again, this ROTPK could be the key itself
  * or a hash of it.
  *
  * Return: 0 = success, Otherwise = error
  */
 static int auth_signature(const auth_method_param_sig_t *param,
 			  const auth_img_desc_t *img_desc,
 			  void *img, unsigned int img_len)
 {
 	void *data_ptr, *pk_ptr, *pk_plat_ptr, *sig_ptr, *sig_alg_ptr;
 	unsigned int data_len, pk_len, pk_plat_len, sig_len, sig_alg_len;
 	unsigned int flags = 0;
 	int rc = 0;

 	/* Get the data to be signed from current image */
 	rc = img_parser_get_auth_param(img_desc->img_type, param->data,
 			img, img_len, &data_ptr, &data_len);
 	return_if_error(rc);

 	/* Get the signature from current image */
 	rc = img_parser_get_auth_param(img_desc->img_type, param->sig,
 			img, img_len, &sig_ptr, &sig_len);
 	return_if_error(rc);

 	/* Get the signature algorithm from current image */
 	rc = img_parser_get_auth_param(img_desc->img_type, param->alg,
 			img, img_len, &sig_alg_ptr, &sig_alg_len);
 	return_if_error(rc);

 	/* Get the public key from the parent. If there is no parent (NULL),
 	 * the certificate has been signed with the ROTPK, so we have to get
 	 * the PK from the platform */
 	if (img_desc->parent != NULL) {
 		rc = auth_get_param(param->pk, img_desc->parent,
 				&pk_ptr, &pk_len);
 		return_if_error(rc);
 	} else {
 		/*
 		 * Root certificates are signed with the ROTPK, so we have to
 		 * get it from the platform.
 		 */
 		rc = plat_get_rotpk_info(param->pk->cookie, &pk_plat_ptr,
 					 &pk_plat_len, &flags);
 		return_if_error(rc);

 		assert(is_rotpk_flags_valid(flags));

 		/* Also retrieve the key from the image. */
 		rc = img_parser_get_auth_param(img_desc->img_type,
 					       param->pk, img, img_len,
 					       &pk_ptr, &pk_len);
 		return_if_error(rc);

 		/*
 		 * Validate the certificate's key against the platform ROTPK.
 		 *
 		 * Platform may store key in one of the following way -
 		 * 1. Hash of ROTPK
 		 * 2. Hash if prefixed, suffixed or modified ROTPK
 		 * 3. Full ROTPK
 		 */
 		if ((flags & ROTPK_NOT_DEPLOYED) != 0U) {
 			NOTICE("ROTPK is not deployed on platform. "
 				"Skipping ROTPK verification.\n");
 		} else if ((flags & ROTPK_IS_HASH) != 0U) {
 			/*
 			 * platform may store the hash of a prefixed,
 			 * suffixed or modified pk
 			 */
 			rc = plat_convert_pk(pk_ptr, pk_len, &pk_ptr, &pk_len);
 			return_if_error(rc);

 			/*
 			 * The hash of the certificate's public key must match
 			 * the hash of the ROTPK.
 			 */
 			rc = crypto_mod_verify_hash(pk_ptr, pk_len,
 						    pk_plat_ptr, pk_plat_len);
 			return_if_error(rc);
 		} else {
 			/* Platform supports full ROTPK */
 			if ((pk_len != pk_plat_len) ||
 			    (memcmp(pk_plat_ptr, pk_ptr, pk_len) != 0)) {
 				ERROR("plat and cert ROTPK len mismatch\n");
 				return -1;
 			}
 		}
 	}

 	/* Ask the crypto module to verify the signature */
 	rc = crypto_mod_verify_signature(data_ptr, data_len,
 					 sig_ptr, sig_len,
 					 sig_alg_ptr, sig_alg_len,
 					 pk_ptr, pk_len);

 	return rc;
 }

 /*
  * Authenticate by Non-Volatile counter
  *
  * To protect the system against rollback, the platform includes a non-volatile
  * counter whose value can only be increased. All certificates include a counter
  * value that should not be lower than the value stored in the platform. If the
  * value is larger, the counter in the platform must be updated to the new value
  * (provided it has been authenticated).
  *
  * Return: 0 = success, Otherwise = error
  * Returns additionally,
  * cert_nv_ctr -> NV counter value present in the certificate
  * need_nv_ctr_upgrade = 0 -> platform NV counter upgrade is not needed
  * need_nv_ctr_upgrade = 1 -> platform NV counter upgrade is needed
  */
 static int auth_nvctr(const auth_method_param_nv_ctr_t *param,
 		      const auth_img_desc_t *img_desc,
 		      void *img, unsigned int img_len,
 		      unsigned int *cert_nv_ctr,
 		      bool *need_nv_ctr_upgrade)
 {
 	unsigned char *p;
 	void *data_ptr = NULL;
 	unsigned int data_len, len, i;
 	unsigned int plat_nv_ctr;
 	int rc = 0;
 	bool is_trial_run = false;

 	/* Get the counter value from current image. The AM expects the IPM
 	 * to return the counter value as a DER encoded integer */
 	rc = img_parser_get_auth_param(img_desc->img_type, param->cert_nv_ctr,
 				       img, img_len, &data_ptr, &data_len);
 	return_if_error(rc);

 	/* Parse the DER encoded integer */
 	assert(data_ptr);
 	p = (unsigned char *)data_ptr;

 	/*
 	 * Integers must be at least 3 bytes: 1 for tag, 1 for length, and 1
 	 * for value.  The first byte (tag) must be ASN1_INTEGER.
 	 */
 	if ((data_len < 3) || (*p != ASN1_INTEGER)) {
 		/* Invalid ASN.1 integer */
 		return 1;
 	}
 	p++;

 	/*
 	 * NV-counters are unsigned integers up to 31 bits.  Trailing
 	 * padding is not allowed.
 	 */
 	len = (unsigned int)*p;
 	if ((len > 4) || (data_len - 2 != len)) {
 		return 1;
 	}
 	p++;

 	/* Check the number is not negative */
 	if (*p & 0x80) {
 		return 1;
 	}

 	/* Convert to unsigned int. This code is for a little-endian CPU */
 	*cert_nv_ctr = 0;
 	for (i = 0; i < len; i++) {
 		*cert_nv_ctr = (*cert_nv_ctr << 8) | *p++;
 	}

 	/* Get the counter from the platform */
 	rc = plat_get_nv_ctr(param->plat_nv_ctr->cookie, &plat_nv_ctr);
 	return_if_error(rc);

 	if (*cert_nv_ctr < plat_nv_ctr) {
 		/* Invalid NV-counter */
 		return 1;
 	} else if (*cert_nv_ctr > plat_nv_ctr) {
 #if PSA_FWU_SUPPORT && IMAGE_BL2
 		is_trial_run = fwu_is_trial_run_state();
 #endif /* PSA_FWU_SUPPORT && IMAGE_BL2 */
 		*need_nv_ctr_upgrade = !is_trial_run;
 	}

 	return 0;
 }

 int plat_set_nv_ctr2(void *cookie, const auth_img_desc_t *img_desc __unused,
 		unsigned int nv_ctr)
 {
 	return plat_set_nv_ctr(cookie, nv_ctr);
 }

 int plat_convert_pk(void *full_pk_ptr, unsigned int full_pk_len,
 		    void **hashed_pk_ptr, unsigned int *hashed_pk_len)
 {
 	*hashed_pk_ptr = full_pk_ptr;
 	*hashed_pk_len = full_pk_len;

 	return 0;
 }

 /*
  * Return the parent id in the output parameter '*parent_id'
  *
  * Return value:
  *   0 = Image has parent, 1 = Image has no parent or parent is authenticated
  */
 int auth_mod_get_parent_id(unsigned int img_id, unsigned int *parent_id)
 {
 	const auth_img_desc_t *img_desc = NULL;

 	assert(parent_id != NULL);
 	/* Get the image descriptor */
 	img_desc = FCONF_GET_PROPERTY(tbbr, cot, img_id);

 	/* Check if the image has no parent (ROT) */
 	if (img_desc->parent == NULL) {
 		*parent_id = 0;
 		return 1;
 	}

 	/* Check if the parent has already been authenticated */
 	if (auth_img_flags[img_desc->parent->img_id] & IMG_FLAG_AUTHENTICATED) {
 		*parent_id = 0;
 		return 1;
 	}

 	*parent_id = img_desc->parent->img_id;
 	return 0;
 }

 /*
  * Initialize the different modules in the authentication framework
  */
 void auth_mod_init(void)
 {
 	/* Check we have a valid CoT registered */
 	assert(cot_desc_ptr != NULL);

 	/* Image parser module */
 	img_parser_init();
 }

 /*
  * Authenticate a certificate/image
  *
  * Return: 0 = success, Otherwise = error
  */
 int auth_mod_verify_img(unsigned int img_id,
 			void *img_ptr,
 			unsigned int img_len)
 {
 	const auth_img_desc_t *img_desc = NULL;
 	const auth_method_desc_t *auth_method = NULL;
 	void *param_ptr;
 	unsigned int param_len;
 	int rc, i;
 	unsigned int cert_nv_ctr = 0;
 	bool need_nv_ctr_upgrade = false;
 	bool sig_auth_done = false;
 	const auth_method_param_nv_ctr_t *nv_ctr_param = NULL;

 	/* Get the image descriptor from the chain of trust */
 	img_desc = FCONF_GET_PROPERTY(tbbr, cot, img_id);

 	/* Ask the parser to check the image integrity */
 	rc = img_parser_check_integrity(img_desc->img_type, img_ptr, img_len);
 	return_if_error(rc);

 	/* Authenticate the image using the methods indicated in the image
 	 * descriptor. */
 	if (img_desc->img_auth_methods == NULL)
 		return 1;
 	for (i = 0 ; i < AUTH_METHOD_NUM ; i++) {
 		auth_method = &img_desc->img_auth_methods[i];
 		switch (auth_method->type) {
 		case AUTH_METHOD_NONE:
 			rc = 0;
 			break;
 		case AUTH_METHOD_HASH:
 			rc = auth_hash(&auth_method->param.hash,
 					img_desc, img_ptr, img_len);
 			break;
 		case AUTH_METHOD_SIG:
 			rc = auth_signature(&auth_method->param.sig,
 					img_desc, img_ptr, img_len);
 			sig_auth_done = true;
 			break;
 		case AUTH_METHOD_NV_CTR:
 			nv_ctr_param = &auth_method->param.nv_ctr;
 			rc = auth_nvctr(nv_ctr_param,
 					img_desc, img_ptr, img_len,
 					&cert_nv_ctr, &need_nv_ctr_upgrade);
 			break;
 		default:
 			/* Unknown authentication method */
 			rc = 1;
 			break;
 		}
 		return_if_error(rc);
 	}

 	/*
 	 * Do platform NV counter upgrade only if the certificate gets
 	 * authenticated, and platform NV-counter upgrade is needed.
 	 */
 	if (need_nv_ctr_upgrade && sig_auth_done) {
 		rc = plat_set_nv_ctr2(nv_ctr_param->plat_nv_ctr->cookie,
 				      img_desc, cert_nv_ctr);
 		return_if_error(rc);
 	}

 	/* Extract the parameters indicated in the image descriptor to
 	 * authenticate the children images. */
 	if (img_desc->authenticated_data != NULL) {
 		for (i = 0 ; i < COT_MAX_VERIFIED_PARAMS ; i++) {
 			if (img_desc->authenticated_data[i].type_desc == NULL) {
 				continue;
 			}

 			/* Get the parameter from the image parser module */
 			rc = img_parser_get_auth_param(img_desc->img_type,
 					img_desc->authenticated_data[i].type_desc,
 					img_ptr, img_len, &param_ptr, &param_len);
 			return_if_error(rc);

 			/* Check parameter size */
 			if (param_len > img_desc->authenticated_data[i].data.len) {
 				return 1;
 			}

 			/* Copy the parameter for later use */
 			memcpy((void *)img_desc->authenticated_data[i].data.ptr,
 					(void *)param_ptr, param_len);
 		}
 	}

 	/* Mark image as authenticated */
 	auth_img_flags[img_desc->img_id] |= IMG_FLAG_AUTHENTICATED;

 	return 0;
 }
	/*
	* Copyright (c) 2015-2023, Arm Limited and Contributors. All rights reserved.
	*
	* SPDX-License-Identifier: BSD-3-Clause
	*/

	#include <assert.h>
	#include <stdint.h>
	#include <string.h>

	#include <platform_def.h>

	#include <common/debug.h>
	#include <common/tbbr/cot_def.h>
	#include <drivers/auth/auth_common.h>
	#include <drivers/auth/auth_mod.h>
	#include <drivers/auth/crypto_mod.h>
	#include <drivers/auth/img_parser_mod.h>
	#include <drivers/fwu/fwu.h>
	#include <lib/fconf/fconf_tbbr_getter.h>
	#include <plat/common/platform.h>

	/* ASN.1 tags */
	#define ASN1_INTEGER 0x02

	#define return_if_error(rc) \
	do { \
	if (rc != 0) { \
	return rc; \
	} \
	} while (0)

	#pragma weak plat_set_nv_ctr2
	#pragma weak plat_convert_pk

	static int cmp_auth_param_type_desc(const auth_param_type_desc_t *a,
	const auth_param_type_desc_t *b)
	{
	if ((a->type == b->type) && (a->cookie == b->cookie)) {
	return 0;
	}
	return 1;
	}

	/*
	* This function obtains the requested authentication parameter data from the
	* information extracted from the parent image after its authentication.
	*/
	static int auth_get_param(const auth_param_type_desc_t *param_type_desc,
	const auth_img_desc_t *img_desc,
	void *param, unsigned int len)
	{
	int i;

	if (img_desc->authenticated_data == NULL)
	return 1;

	for (i = 0 ; i < COT_MAX_VERIFIED_PARAMS ; i++) {
	if (0 == cmp_auth_param_type_desc(param_type_desc,
	img_desc->authenticated_data[i].type_desc)) {
	*param = img_desc->authenticated_data[i].data.ptr;
	*len = img_desc->authenticated_data[i].data.len;
	return 0;
	}
	}

	return 1;
	}

	/*
	* Authenticate an image by matching the data hash
	*
	* This function implements 'AUTH_METHOD_HASH'. To authenticate an image using
	* this method, the image must contain:
	*
	* - The data to calculate the hash from
	*
	* The parent image must contain:
	*
	* - The hash to be matched with (including hash algorithm)
	*
	* For a successful authentication, both hashes must match. The function calls
	* the crypto-module to check this matching.
	*
	* Parameters:
	* param: parameters to perform the hash authentication
	* img_desc: pointer to image descriptor so we can know the image type
	* and parent image
	* img: pointer to image in memory
	* img_len: length of image (in bytes)
	*
	* Return:
	* 0 = success, Otherwise = error
	*/
	static int auth_hash(const auth_method_param_hash_t *param,
	const auth_img_desc_t *img_desc,
	void *img, unsigned int img_len)
	{
	void data_ptr, hash_der_ptr;
	unsigned int data_len, hash_der_len;
	int rc = 0;

	/* Get the hash from the parent image. This hash will be DER encoded
	* and contain the hash algorithm */
	rc = auth_get_param(param->hash, img_desc->parent,
	&hash_der_ptr, &hash_der_len);
	return_if_error(rc);

	/* Get the data to be hashed from the current image */
	rc = img_parser_get_auth_param(img_desc->img_type, param->data,
	img, img_len, &data_ptr, &data_len);
	return_if_error(rc);

	/* Ask the crypto module to verify this hash */
	rc = crypto_mod_verify_hash(data_ptr, data_len,
	hash_der_ptr, hash_der_len);

	return rc;
	}

	/*
	* Authenticate by digital signature
	*
	* This function implements 'AUTH_METHOD_SIG'. To authenticate an image using
	* this method, the image must contain:
	*
	* - Data to be signed
	* - Signature
	* - Signature algorithm
	*
	* We rely on the image parser module to extract this data from the image.
	* The parent image must contain:
	*
	* - Public key (or a hash of it)
	*
	* If the parent image contains only a hash of the key, we will try to obtain
	* the public key from the image itself (i.e. self-signed certificates). In that
	* case, the signature verification is considered just an integrity check and
	* the authentication is established by calculating the hash of the key and
	* comparing it with the hash obtained from the parent.
	*
	* If the image has no parent (NULL), it means it has to be authenticated using
	* the ROTPK stored in the platform. Again, this ROTPK could be the key itself
	* or a hash of it.
	*
	* Return: 0 = success, Otherwise = error
	*/
	static int auth_signature(const auth_method_param_sig_t *param,
	const auth_img_desc_t *img_desc,
	void *img, unsigned int img_len)
	{
	void data_ptr, pk_ptr, pk_plat_ptr, sig_ptr, *sig_alg_ptr;
	unsigned int data_len, pk_len, pk_plat_len, sig_len, sig_alg_len;
	unsigned int flags = 0;
	int rc = 0;

	/* Get the data to be signed from current image */
	rc = img_parser_get_auth_param(img_desc->img_type, param->data,
	img, img_len, &data_ptr, &data_len);
	return_if_error(rc);

	/* Get the signature from current image */
	rc = img_parser_get_auth_param(img_desc->img_type, param->sig,
	img, img_len, &sig_ptr, &sig_len);
	return_if_error(rc);

	/* Get the signature algorithm from current image */
	rc = img_parser_get_auth_param(img_desc->img_type, param->alg,
	img, img_len, &sig_alg_ptr, &sig_alg_len);
	return_if_error(rc);

	/* Get the public key from the parent. If there is no parent (NULL),
	* the certificate has been signed with the ROTPK, so we have to get
	* the PK from the platform */
	if (img_desc->parent != NULL) {
	rc = auth_get_param(param->pk, img_desc->parent,
	&pk_ptr, &pk_len);
	return_if_error(rc);
	} else {
	/*
	* Root certificates are signed with the ROTPK, so we have to
	* get it from the platform.
	*/
	rc = plat_get_rotpk_info(param->pk->cookie, &pk_plat_ptr,
	&pk_plat_len, &flags);
	return_if_error(rc);

	assert(is_rotpk_flags_valid(flags));

	/* Also retrieve the key from the image. */
	rc = img_parser_get_auth_param(img_desc->img_type,
	param->pk, img, img_len,
	&pk_ptr, &pk_len);
	return_if_error(rc);

	/*
	* Validate the certificate's key against the platform ROTPK.
	*
	* Platform may store key in one of the following way -
	* 1. Hash of ROTPK
	* 2. Hash if prefixed, suffixed or modified ROTPK
	* 3. Full ROTPK
	*/
	if ((flags & ROTPK_NOT_DEPLOYED) != 0U) {
	NOTICE("ROTPK is not deployed on platform. "
	"Skipping ROTPK verification.\n");
	} else if ((flags & ROTPK_IS_HASH) != 0U) {
	/*
	* platform may store the hash of a prefixed,
	* suffixed or modified pk
	*/
	rc = plat_convert_pk(pk_ptr, pk_len, &pk_ptr, &pk_len);
	return_if_error(rc);

	/*
	* The hash of the certificate's public key must match
	* the hash of the ROTPK.
	*/
	rc = crypto_mod_verify_hash(pk_ptr, pk_len,
	pk_plat_ptr, pk_plat_len);
	return_if_error(rc);
	} else {
	/* Platform supports full ROTPK */
	if ((pk_len != pk_plat_len) \|\|
	(memcmp(pk_plat_ptr, pk_ptr, pk_len) != 0)) {
	ERROR("plat and cert ROTPK len mismatch\n");
	return -1;
	}
	}
	}

	/* Ask the crypto module to verify the signature */
	rc = crypto_mod_verify_signature(data_ptr, data_len,
	sig_ptr, sig_len,
	sig_alg_ptr, sig_alg_len,
	pk_ptr, pk_len);

	return rc;
	}

	/*
	* Authenticate by Non-Volatile counter
	*
	* To protect the system against rollback, the platform includes a non-volatile
	* counter whose value can only be increased. All certificates include a counter
	* value that should not be lower than the value stored in the platform. If the
	* value is larger, the counter in the platform must be updated to the new value
	* (provided it has been authenticated).
	*
	* Return: 0 = success, Otherwise = error
	* Returns additionally,
	* cert_nv_ctr -> NV counter value present in the certificate
	* need_nv_ctr_upgrade = 0 -> platform NV counter upgrade is not needed
	* need_nv_ctr_upgrade = 1 -> platform NV counter upgrade is needed
	*/
	static int auth_nvctr(const auth_method_param_nv_ctr_t *param,
	const auth_img_desc_t *img_desc,
	void *img, unsigned int img_len,
	unsigned int *cert_nv_ctr,
	bool *need_nv_ctr_upgrade)
	{
	unsigned char *p;
	void *data_ptr = NULL;
	unsigned int data_len, len, i;
	unsigned int plat_nv_ctr;
	int rc = 0;
	bool is_trial_run = false;

	/* Get the counter value from current image. The AM expects the IPM
	* to return the counter value as a DER encoded integer */
	rc = img_parser_get_auth_param(img_desc->img_type, param->cert_nv_ctr,
	img, img_len, &data_ptr, &data_len);
	return_if_error(rc);

	/* Parse the DER encoded integer */
	assert(data_ptr);
	p = (unsigned char *)data_ptr;

	/*
	* Integers must be at least 3 bytes: 1 for tag, 1 for length, and 1
	* for value. The first byte (tag) must be ASN1_INTEGER.
	*/
	if ((data_len < 3) \|\| (*p != ASN1_INTEGER)) {
	/* Invalid ASN.1 integer */
	return 1;
	}
	p++;

	/*
	* NV-counters are unsigned integers up to 31 bits. Trailing
	* padding is not allowed.
	*/
	len = (unsigned int)*p;
	if ((len > 4) \|\| (data_len - 2 != len)) {
	return 1;
	}
	p++;

	/* Check the number is not negative */
	if (*p & 0x80) {
	return 1;
	}

	/* Convert to unsigned int. This code is for a little-endian CPU */
	*cert_nv_ctr = 0;
	for (i = 0; i < len; i++) {
	cert_nv_ctr = (cert_nv_ctr << 8) \| *p++;
	}

	/* Get the counter from the platform */
	rc = plat_get_nv_ctr(param->plat_nv_ctr->cookie, &plat_nv_ctr);
	return_if_error(rc);

	if (*cert_nv_ctr < plat_nv_ctr) {
	/* Invalid NV-counter */
	return 1;
	} else if (*cert_nv_ctr > plat_nv_ctr) {
	#if PSA_FWU_SUPPORT && IMAGE_BL2
	is_trial_run = fwu_is_trial_run_state();
	#endif /* PSA_FWU_SUPPORT && IMAGE_BL2 */
	*need_nv_ctr_upgrade = !is_trial_run;
	}

	return 0;
	}

	int plat_set_nv_ctr2(void cookie, const auth_img_desc_t img_desc __unused,
	unsigned int nv_ctr)
	{
	return plat_set_nv_ctr(cookie, nv_ctr);
	}

	int plat_convert_pk(void *full_pk_ptr, unsigned int full_pk_len,
	void *hashed_pk_ptr, unsigned int hashed_pk_len)
	{
	*hashed_pk_ptr = full_pk_ptr;
	*hashed_pk_len = full_pk_len;

	return 0;
	}

	/*
	* Return the parent id in the output parameter '*parent_id'
	*
	* Return value:
	* 0 = Image has parent, 1 = Image has no parent or parent is authenticated
	*/
	int auth_mod_get_parent_id(unsigned int img_id, unsigned int *parent_id)
	{
	const auth_img_desc_t *img_desc = NULL;

	assert(parent_id != NULL);
	/* Get the image descriptor */
	img_desc = FCONF_GET_PROPERTY(tbbr, cot, img_id);

	/* Check if the image has no parent (ROT) */
	if (img_desc->parent == NULL) {
	*parent_id = 0;
	return 1;
	}

	/* Check if the parent has already been authenticated */
	if (auth_img_flags[img_desc->parent->img_id] & IMG_FLAG_AUTHENTICATED) {
	*parent_id = 0;
	return 1;
	}

	*parent_id = img_desc->parent->img_id;
	return 0;
	}

	/*
	* Initialize the different modules in the authentication framework
	*/
	void auth_mod_init(void)
	{
	/* Check we have a valid CoT registered */
	assert(cot_desc_ptr != NULL);

	/* Image parser module */
	img_parser_init();
	}

	/*
	* Authenticate a certificate/image
	*
	* Return: 0 = success, Otherwise = error
	*/
	int auth_mod_verify_img(unsigned int img_id,
	void *img_ptr,
	unsigned int img_len)
	{
	const auth_img_desc_t *img_desc = NULL;
	const auth_method_desc_t *auth_method = NULL;
	void *param_ptr;
	unsigned int param_len;
	int rc, i;
	unsigned int cert_nv_ctr = 0;
	bool need_nv_ctr_upgrade = false;
	bool sig_auth_done = false;
	const auth_method_param_nv_ctr_t *nv_ctr_param = NULL;

	/* Get the image descriptor from the chain of trust */
	img_desc = FCONF_GET_PROPERTY(tbbr, cot, img_id);

	/* Ask the parser to check the image integrity */
	rc = img_parser_check_integrity(img_desc->img_type, img_ptr, img_len);
	return_if_error(rc);

	/* Authenticate the image using the methods indicated in the image
	* descriptor. */
	if (img_desc->img_auth_methods == NULL)
	return 1;
	for (i = 0 ; i < AUTH_METHOD_NUM ; i++) {
	auth_method = &img_desc->img_auth_methods[i];
	switch (auth_method->type) {
	case AUTH_METHOD_NONE:
	rc = 0;
	break;
	case AUTH_METHOD_HASH:
	rc = auth_hash(&auth_method->param.hash,
	img_desc, img_ptr, img_len);
	break;
	case AUTH_METHOD_SIG:
	rc = auth_signature(&auth_method->param.sig,
	img_desc, img_ptr, img_len);
	sig_auth_done = true;
	break;
	case AUTH_METHOD_NV_CTR:
	nv_ctr_param = &auth_method->param.nv_ctr;
	rc = auth_nvctr(nv_ctr_param,
	img_desc, img_ptr, img_len,
	&cert_nv_ctr, &need_nv_ctr_upgrade);
	break;
	default:
	/* Unknown authentication method */
	rc = 1;
	break;
	}
	return_if_error(rc);
	}

	/*
	* Do platform NV counter upgrade only if the certificate gets
	* authenticated, and platform NV-counter upgrade is needed.
	*/
	if (need_nv_ctr_upgrade && sig_auth_done) {
	rc = plat_set_nv_ctr2(nv_ctr_param->plat_nv_ctr->cookie,
	img_desc, cert_nv_ctr);
	return_if_error(rc);
	}

	/* Extract the parameters indicated in the image descriptor to
	* authenticate the children images. */
	if (img_desc->authenticated_data != NULL) {
	for (i = 0 ; i < COT_MAX_VERIFIED_PARAMS ; i++) {
	if (img_desc->authenticated_data[i].type_desc == NULL) {
	continue;
	}

	/* Get the parameter from the image parser module */
	rc = img_parser_get_auth_param(img_desc->img_type,
	img_desc->authenticated_data[i].type_desc,
	img_ptr, img_len, &param_ptr, &param_len);
	return_if_error(rc);

	/* Check parameter size */
	if (param_len > img_desc->authenticated_data[i].data.len) {
	return 1;
	}

	/* Copy the parameter for later use */
	memcpy((void *)img_desc->authenticated_data[i].data.ptr,
	(void *)param_ptr, param_len);
	}
	}

	/* Mark image as authenticated */
	auth_img_flags[img_desc->img_id] \|= IMG_FLAG_AUTHENTICATED;

	return 0;
	}