drivers/crypto/crypto_mtls_shim.c - third_party/github/zephyrproject-rtos/zephyr - Git at Google

 /*
  * Copyright (c) 2017 Intel Corporation.
  *
  * SPDX-License-Identifier: Apache-2.0
  */

 /**
  * @file Shim layer for mbedTLS, crypto API compliant.
  */


 #include <kernel.h>
 #include <init.h>
 #include <errno.h>
 #include <crypto/cipher.h>

 #if !defined(CONFIG_MBEDTLS_CFG_FILE)
 #include "mbedtls/config.h"
 #else
 #include CONFIG_MBEDTLS_CFG_FILE
 #endif /* CONFIG_MBEDTLS_CFG_FILE */

 #include <mbedtls/ccm.h>
 #include <mbedtls/aes.h>

 #define MTLS_SUPPORT (CAP_RAW_KEY | CAP_SEPARATE_IO_BUFS | CAP_SYNC_OPS)

 #define LOG_LEVEL CONFIG_CRYPTO_LOG_LEVEL
 #include <logging/log.h>
 LOG_MODULE_REGISTER(mbedtls);

 struct mtls_shim_session {
 	union {
 		mbedtls_ccm_context mtls_ccm;
 		mbedtls_aes_context mtls_aes;
 	};
 	bool in_use;
 	enum cipher_mode mode;
 };

 #define CRYPTO_MAX_SESSION CONFIG_CRYPTO_MBEDTLS_SHIM_MAX_SESSION

 struct mtls_shim_session mtls_sessions[CRYPTO_MAX_SESSION];

 #if defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C)
 #include "mbedtls/memory_buffer_alloc.h"
 #else
 #error "You need to define MBEDTLS_MEMORY_BUFFER_ALLOC_C"
 #endif /* MBEDTLS_MEMORY_BUFFER_ALLOC_C */

 #define MTLS_GET_CTX(c, m) \
 	(&((struct mtls_shim_session *)c->drv_sessn_state)->mtls_ ## m)

 int mtls_ecb_encrypt(struct cipher_ctx *ctx, struct cipher_pkt *pkt)
 {
 	int ret;
 	mbedtls_aes_context *ecb_ctx = MTLS_GET_CTX(ctx, aes);

 	/* For security reasons, ECB mode should not be used to encrypt
 	 * more than one block. Use CBC mode instead.
 	 */
 	if (pkt->in_len > 16) {
 		LOG_ERR("Cannot encrypt more than 1 block");
 		return -EINVAL;
 	}

 	ret = mbedtls_aes_crypt_ecb(ecb_ctx, MBEDTLS_AES_ENCRYPT,
 				    pkt->in_buf, pkt->out_buf);
 	if (ret) {
 		LOG_ERR("Could not encrypt (%d)", ret);
 		return -EINVAL;
 	}

 	pkt->out_len = 16;

 	return 0;
 }

 int mtls_ecb_decrypt(struct cipher_ctx *ctx, struct cipher_pkt *pkt)
 {
 	int ret;
 	mbedtls_aes_context *ecb_ctx = MTLS_GET_CTX(ctx, aes);

 	/* For security reasons, ECB mode should not be used to decrypt
 	 * more than one block. Use CBC mode instead.
 	 */
 	if (pkt->in_len > 16) {
 		LOG_ERR("Cannot decrypt more than 1 block");
 		return -EINVAL;
 	}

 	ret = mbedtls_aes_crypt_ecb(ecb_ctx, MBEDTLS_AES_DECRYPT,
 				    pkt->in_buf, pkt->out_buf);
 	if (ret) {
 		LOG_ERR("Could not encrypt (%d)", ret);
 		return -EINVAL;
 	}

 	pkt->out_len = 16;

 	return 0;
 }

 int mtls_cbc_encrypt(struct cipher_ctx *ctx, struct cipher_pkt *pkt, u8_t *iv)
 {
 	int ret;
 	mbedtls_aes_context *cbc_ctx = MTLS_GET_CTX(ctx, aes);

 	/* Prefix IV to ciphertext */
 	memcpy(pkt->out_buf, iv, 16);
 	ret = mbedtls_aes_crypt_cbc(cbc_ctx, MBEDTLS_AES_ENCRYPT, pkt->in_len,
 				    iv, pkt->in_buf, pkt->out_buf + 16);
 	if (ret) {
 		LOG_ERR("Could not encrypt (%d)", ret);
 		return -EINVAL;
 	}

 	pkt->out_len = pkt->in_len + 16;

 	return 0;
 }

 int mtls_cbc_decrypt(struct cipher_ctx *ctx, struct cipher_pkt *pkt, u8_t *iv)
 {
 	int ret;
 	mbedtls_aes_context *cbc_ctx = MTLS_GET_CTX(ctx, aes);

 	ret = mbedtls_aes_crypt_cbc(cbc_ctx, MBEDTLS_AES_DECRYPT, pkt->in_len,
 				    iv, pkt->in_buf + 16, pkt->out_buf);
 	if (ret) {
 		LOG_ERR("Could not encrypt (%d)", ret);
 		return -EINVAL;
 	}

 	pkt->out_len = pkt->in_len - 16;

 	return 0;
 }

 static int mtls_ccm_encrypt_auth(struct cipher_ctx *ctx,
 				 struct cipher_aead_pkt *apkt,
 				 u8_t *nonce)
 {
 	mbedtls_ccm_context *mtls_ctx = MTLS_GET_CTX(ctx, ccm);
 	int ret;

 	ret = mbedtls_ccm_encrypt_and_tag(mtls_ctx, apkt->pkt->in_len, nonce,
 					  ctx->mode_params.ccm_info.nonce_len,
 					  apkt->ad, apkt->ad_len,
 					  apkt->pkt->in_buf,
 					  apkt->pkt->out_buf, apkt->tag,
 					  ctx->mode_params.ccm_info.tag_len);
 	if (ret) {
 		LOG_ERR("Could not encrypt/auth (%d)", ret);

 		/*ToDo: try to return relevant code depending on ret? */
 		return -EINVAL;
 	}

 	/* This is equivalent to what the TinyCrypt shim does in
 	 * do_ccm_encrypt_mac().
 	 */
 	apkt->pkt->out_len = apkt->pkt->in_len;
 	apkt->pkt->out_len += ctx->mode_params.ccm_info.tag_len;

 	return 0;
 }

 static int mtls_ccm_decrypt_auth(struct cipher_ctx *ctx,
 				 struct cipher_aead_pkt *apkt,
 				 u8_t *nonce)
 {
 	mbedtls_ccm_context *mtls_ctx = MTLS_GET_CTX(ctx, ccm);
 	int ret;

 	ret = mbedtls_ccm_auth_decrypt(mtls_ctx, apkt->pkt->in_len, nonce,
 				       ctx->mode_params.ccm_info.nonce_len,
 				       apkt->ad, apkt->ad_len,
 				       apkt->pkt->in_buf,
 				       apkt->pkt->out_buf, apkt->tag,
 				       ctx->mode_params.ccm_info.tag_len);
 	if (ret) {
 		LOG_ERR("Could non decrypt/auth (%d)", ret);

 		/*ToDo: try to return relevant code depending on ret? */
 		return -EINVAL;
 	}

 	apkt->pkt->out_len = apkt->pkt->in_len;
 	apkt->pkt->out_len += ctx->mode_params.ccm_info.tag_len;

 	return 0;
 }

 static int mtls_get_unused_session_index(void)
 {
 	int i;

 	for (i = 0; i < CRYPTO_MAX_SESSION; i++) {
 		if (!mtls_sessions[i].in_use) {
 			mtls_sessions[i].in_use = true;
 			return i;
 		}
 	}

 	return -1;
 }

 static int mtls_session_setup(struct device *dev, struct cipher_ctx *ctx,
 		       enum cipher_algo algo, enum cipher_mode mode,
 		       enum cipher_op op_type)
 {
 	mbedtls_ccm_context *ccm_ctx;
 	mbedtls_aes_context *aes_ctx;
 	int ctx_idx;
 	int ret;

 	if (ctx->flags & ~(MTLS_SUPPORT)) {
 		LOG_ERR("Unsupported flag");
 		return -EINVAL;
 	}

 	if (algo != CRYPTO_CIPHER_ALGO_AES) {
 		LOG_ERR("Unsupported algo");
 		return -EINVAL;
 	}

 	if (mode != CRYPTO_CIPHER_MODE_CCM &&
 	    mode != CRYPTO_CIPHER_MODE_CBC &&
 	    mode != CRYPTO_CIPHER_MODE_ECB) {
 		LOG_ERR("Unsupported mode");
 		return -EINVAL;
 	}

 	if (ctx->keylen != 16U) {
 		LOG_ERR("%u key size is not supported", ctx->keylen);
 		return -EINVAL;
 	}

 	ctx_idx = mtls_get_unused_session_index();
 	if (ctx_idx < 0) {
 		LOG_ERR("No free session for now");
 		return -ENOSPC;
 	}


 	switch (mode) {
 	case CRYPTO_CIPHER_MODE_ECB:
 		aes_ctx = &mtls_sessions[ctx_idx].mtls_aes;
 		mbedtls_aes_init(aes_ctx);
 		if (op_type == CRYPTO_CIPHER_OP_ENCRYPT) {
 			ret = mbedtls_aes_setkey_enc(aes_ctx,
 					ctx->key.bit_stream, ctx->keylen * 8U);
 			ctx->ops.block_crypt_hndlr = mtls_ecb_encrypt;
 		} else {
 			ret = mbedtls_aes_setkey_dec(aes_ctx,
 					ctx->key.bit_stream, ctx->keylen * 8U);
 			ctx->ops.block_crypt_hndlr = mtls_ecb_decrypt;
 		}
 		if (ret) {
 			LOG_ERR("AES_ECB: failed at setkey (%d)", ret);
 			ctx->ops.block_crypt_hndlr = NULL;
 			mtls_sessions[ctx_idx].in_use = false;
 			return -EINVAL;
 		}
 		break;
 	case CRYPTO_CIPHER_MODE_CTR:
 		break;
 	case CRYPTO_CIPHER_MODE_CBC:
 		aes_ctx = &mtls_sessions[ctx_idx].mtls_aes;
 		mbedtls_aes_init(aes_ctx);
 		if (op_type == CRYPTO_CIPHER_OP_ENCRYPT) {
 			ret = mbedtls_aes_setkey_enc(aes_ctx,
 					ctx->key.bit_stream, ctx->keylen * 8U);
 			ctx->ops.cbc_crypt_hndlr = mtls_cbc_encrypt;
 		} else {
 			ret = mbedtls_aes_setkey_dec(aes_ctx,
 					ctx->key.bit_stream, ctx->keylen * 8U);
 			ctx->ops.cbc_crypt_hndlr = mtls_cbc_decrypt;
 		}
 		if (ret) {
 			LOG_ERR("AES_CBC: failed at setkey (%d)", ret);
 			ctx->ops.cbc_crypt_hndlr = NULL;
 			mtls_sessions[ctx_idx].in_use = false;
 			return -EINVAL;
 		}
 		break;
 	case CRYPTO_CIPHER_MODE_CCM:
 		ccm_ctx = &mtls_sessions[ctx_idx].mtls_ccm;
 		mbedtls_ccm_init(ccm_ctx);
 		ret = mbedtls_ccm_setkey(ccm_ctx, MBEDTLS_CIPHER_ID_AES,
 					 ctx->key.bit_stream, ctx->keylen * 8U);
 		if (ret) {
 			LOG_ERR("Could not setup the key (%d)", ret);
 			mtls_sessions[ctx_idx].in_use = false;

 			return -EINVAL;
 		}
 		if (op_type == CRYPTO_CIPHER_OP_ENCRYPT) {
 			ctx->ops.ccm_crypt_hndlr = mtls_ccm_encrypt_auth;
 		} else {
 			ctx->ops.ccm_crypt_hndlr = mtls_ccm_decrypt_auth;
 		}
 		break;
 	}

 	mtls_sessions[ctx_idx].mode = mode;
 	ctx->drv_sessn_state = &mtls_sessions[ctx_idx];

 	return ret;
 }

 static int mtls_session_free(struct device *dev, struct cipher_ctx *ctx)
 {
 	struct mtls_shim_session *mtls_session =
 		(struct mtls_shim_session *)ctx->drv_sessn_state;

 	if (mtls_session->mode == CRYPTO_CIPHER_MODE_CCM) {
 		mbedtls_ccm_free(&mtls_session->mtls_ccm);
 	} else {
 		mbedtls_aes_free(&mtls_session->mtls_aes);
 	}
 	mtls_session->in_use = false;

 	return 0;
 }

 static int mtls_query_caps(struct device *dev)
 {
 	return MTLS_SUPPORT;
 }

 static int mtls_shim_init(struct device *dev)
 {
 	return 0;
 }

 static struct crypto_driver_api mtls_crypto_funcs = {
 	.begin_session = mtls_session_setup,
 	.free_session = mtls_session_free,
 	.crypto_async_callback_set = NULL,
 	.query_hw_caps = mtls_query_caps,
 };

 DEVICE_AND_API_INIT(crypto_mtls, CONFIG_CRYPTO_MBEDTLS_SHIM_DRV_NAME,
 		    &mtls_shim_init, NULL, NULL,
 		    POST_KERNEL, CONFIG_CRYPTO_INIT_PRIORITY,
 		    (void *)&mtls_crypto_funcs);
	/*
	* Copyright (c) 2017 Intel Corporation.
	*
	* SPDX-License-Identifier: Apache-2.0
	*/

	/**
	* @file Shim layer for mbedTLS, crypto API compliant.
	*/


	#include <kernel.h>
	#include <init.h>
	#include <errno.h>
	#include <crypto/cipher.h>

	#if !defined(CONFIG_MBEDTLS_CFG_FILE)
	#include "mbedtls/config.h"
	#else
	#include CONFIG_MBEDTLS_CFG_FILE
	#endif /* CONFIG_MBEDTLS_CFG_FILE */

	#include <mbedtls/ccm.h>
	#include <mbedtls/aes.h>

	#define MTLS_SUPPORT (CAP_RAW_KEY \| CAP_SEPARATE_IO_BUFS \| CAP_SYNC_OPS)

	#define LOG_LEVEL CONFIG_CRYPTO_LOG_LEVEL
	#include <logging/log.h>
	LOG_MODULE_REGISTER(mbedtls);

	struct mtls_shim_session {
	union {
	mbedtls_ccm_context mtls_ccm;
	mbedtls_aes_context mtls_aes;
	};
	bool in_use;
	enum cipher_mode mode;
	};

	#define CRYPTO_MAX_SESSION CONFIG_CRYPTO_MBEDTLS_SHIM_MAX_SESSION

	struct mtls_shim_session mtls_sessions[CRYPTO_MAX_SESSION];

	#if defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C)
	#include "mbedtls/memory_buffer_alloc.h"
	#else
	#error "You need to define MBEDTLS_MEMORY_BUFFER_ALLOC_C"
	#endif /* MBEDTLS_MEMORY_BUFFER_ALLOC_C */

	#define MTLS_GET_CTX(c, m) \
	(&((struct mtls_shim_session *)c->drv_sessn_state)->mtls_ ## m)

	int mtls_ecb_encrypt(struct cipher_ctx ctx, struct cipher_pkt pkt)
	{
	int ret;
	mbedtls_aes_context *ecb_ctx = MTLS_GET_CTX(ctx, aes);

	/* For security reasons, ECB mode should not be used to encrypt
	* more than one block. Use CBC mode instead.
	*/
	if (pkt->in_len > 16) {
	LOG_ERR("Cannot encrypt more than 1 block");
	return -EINVAL;
	}

	ret = mbedtls_aes_crypt_ecb(ecb_ctx, MBEDTLS_AES_ENCRYPT,
	pkt->in_buf, pkt->out_buf);
	if (ret) {
	LOG_ERR("Could not encrypt (%d)", ret);
	return -EINVAL;
	}

	pkt->out_len = 16;

	return 0;
	}

	int mtls_ecb_decrypt(struct cipher_ctx ctx, struct cipher_pkt pkt)
	{
	int ret;
	mbedtls_aes_context *ecb_ctx = MTLS_GET_CTX(ctx, aes);

	/* For security reasons, ECB mode should not be used to decrypt
	* more than one block. Use CBC mode instead.
	*/
	if (pkt->in_len > 16) {
	LOG_ERR("Cannot decrypt more than 1 block");
	return -EINVAL;
	}

	ret = mbedtls_aes_crypt_ecb(ecb_ctx, MBEDTLS_AES_DECRYPT,
	pkt->in_buf, pkt->out_buf);
	if (ret) {
	LOG_ERR("Could not encrypt (%d)", ret);
	return -EINVAL;
	}

	pkt->out_len = 16;

	return 0;
	}

	int mtls_cbc_encrypt(struct cipher_ctx ctx, struct cipher_pkt pkt, u8_t *iv)
	{
	int ret;
	mbedtls_aes_context *cbc_ctx = MTLS_GET_CTX(ctx, aes);

	/* Prefix IV to ciphertext */
	memcpy(pkt->out_buf, iv, 16);
	ret = mbedtls_aes_crypt_cbc(cbc_ctx, MBEDTLS_AES_ENCRYPT, pkt->in_len,
	iv, pkt->in_buf, pkt->out_buf + 16);
	if (ret) {
	LOG_ERR("Could not encrypt (%d)", ret);
	return -EINVAL;
	}

	pkt->out_len = pkt->in_len + 16;

	return 0;
	}

	int mtls_cbc_decrypt(struct cipher_ctx ctx, struct cipher_pkt pkt, u8_t *iv)
	{
	int ret;
	mbedtls_aes_context *cbc_ctx = MTLS_GET_CTX(ctx, aes);

	ret = mbedtls_aes_crypt_cbc(cbc_ctx, MBEDTLS_AES_DECRYPT, pkt->in_len,
	iv, pkt->in_buf + 16, pkt->out_buf);
	if (ret) {
	LOG_ERR("Could not encrypt (%d)", ret);
	return -EINVAL;
	}

	pkt->out_len = pkt->in_len - 16;

	return 0;
	}

	static int mtls_ccm_encrypt_auth(struct cipher_ctx *ctx,
	struct cipher_aead_pkt *apkt,
	u8_t *nonce)
	{
	mbedtls_ccm_context *mtls_ctx = MTLS_GET_CTX(ctx, ccm);
	int ret;

	ret = mbedtls_ccm_encrypt_and_tag(mtls_ctx, apkt->pkt->in_len, nonce,
	ctx->mode_params.ccm_info.nonce_len,
	apkt->ad, apkt->ad_len,
	apkt->pkt->in_buf,
	apkt->pkt->out_buf, apkt->tag,
	ctx->mode_params.ccm_info.tag_len);
	if (ret) {
	LOG_ERR("Could not encrypt/auth (%d)", ret);

	/ToDo: try to return relevant code depending on ret? /
	return -EINVAL;
	}

	/* This is equivalent to what the TinyCrypt shim does in
	* do_ccm_encrypt_mac().
	*/
	apkt->pkt->out_len = apkt->pkt->in_len;
	apkt->pkt->out_len += ctx->mode_params.ccm_info.tag_len;

	return 0;
	}

	static int mtls_ccm_decrypt_auth(struct cipher_ctx *ctx,
	struct cipher_aead_pkt *apkt,
	u8_t *nonce)
	{
	mbedtls_ccm_context *mtls_ctx = MTLS_GET_CTX(ctx, ccm);
	int ret;

	ret = mbedtls_ccm_auth_decrypt(mtls_ctx, apkt->pkt->in_len, nonce,
	ctx->mode_params.ccm_info.nonce_len,
	apkt->ad, apkt->ad_len,
	apkt->pkt->in_buf,
	apkt->pkt->out_buf, apkt->tag,
	ctx->mode_params.ccm_info.tag_len);
	if (ret) {
	LOG_ERR("Could non decrypt/auth (%d)", ret);

	/ToDo: try to return relevant code depending on ret? /
	return -EINVAL;
	}

	apkt->pkt->out_len = apkt->pkt->in_len;
	apkt->pkt->out_len += ctx->mode_params.ccm_info.tag_len;

	return 0;
	}

	static int mtls_get_unused_session_index(void)
	{
	int i;

	for (i = 0; i < CRYPTO_MAX_SESSION; i++) {
	if (!mtls_sessions[i].in_use) {
	mtls_sessions[i].in_use = true;
	return i;
	}
	}

	return -1;
	}

	static int mtls_session_setup(struct device dev, struct cipher_ctx ctx,
	enum cipher_algo algo, enum cipher_mode mode,
	enum cipher_op op_type)
	{
	mbedtls_ccm_context *ccm_ctx;
	mbedtls_aes_context *aes_ctx;
	int ctx_idx;
	int ret;

	if (ctx->flags & ~(MTLS_SUPPORT)) {
	LOG_ERR("Unsupported flag");
	return -EINVAL;
	}

	if (algo != CRYPTO_CIPHER_ALGO_AES) {
	LOG_ERR("Unsupported algo");
	return -EINVAL;
	}

	if (mode != CRYPTO_CIPHER_MODE_CCM &&
	mode != CRYPTO_CIPHER_MODE_CBC &&
	mode != CRYPTO_CIPHER_MODE_ECB) {
	LOG_ERR("Unsupported mode");
	return -EINVAL;
	}

	if (ctx->keylen != 16U) {
	LOG_ERR("%u key size is not supported", ctx->keylen);
	return -EINVAL;
	}

	ctx_idx = mtls_get_unused_session_index();
	if (ctx_idx < 0) {
	LOG_ERR("No free session for now");
	return -ENOSPC;
	}


	switch (mode) {
	case CRYPTO_CIPHER_MODE_ECB:
	aes_ctx = &mtls_sessions[ctx_idx].mtls_aes;
	mbedtls_aes_init(aes_ctx);
	if (op_type == CRYPTO_CIPHER_OP_ENCRYPT) {
	ret = mbedtls_aes_setkey_enc(aes_ctx,
	ctx->key.bit_stream, ctx->keylen * 8U);
	ctx->ops.block_crypt_hndlr = mtls_ecb_encrypt;
	} else {
	ret = mbedtls_aes_setkey_dec(aes_ctx,
	ctx->key.bit_stream, ctx->keylen * 8U);
	ctx->ops.block_crypt_hndlr = mtls_ecb_decrypt;
	}
	if (ret) {
	LOG_ERR("AES_ECB: failed at setkey (%d)", ret);
	ctx->ops.block_crypt_hndlr = NULL;
	mtls_sessions[ctx_idx].in_use = false;
	return -EINVAL;
	}
	break;
	case CRYPTO_CIPHER_MODE_CTR:
	break;
	case CRYPTO_CIPHER_MODE_CBC:
	aes_ctx = &mtls_sessions[ctx_idx].mtls_aes;
	mbedtls_aes_init(aes_ctx);
	if (op_type == CRYPTO_CIPHER_OP_ENCRYPT) {
	ret = mbedtls_aes_setkey_enc(aes_ctx,
	ctx->key.bit_stream, ctx->keylen * 8U);
	ctx->ops.cbc_crypt_hndlr = mtls_cbc_encrypt;
	} else {
	ret = mbedtls_aes_setkey_dec(aes_ctx,
	ctx->key.bit_stream, ctx->keylen * 8U);
	ctx->ops.cbc_crypt_hndlr = mtls_cbc_decrypt;
	}
	if (ret) {
	LOG_ERR("AES_CBC: failed at setkey (%d)", ret);
	ctx->ops.cbc_crypt_hndlr = NULL;
	mtls_sessions[ctx_idx].in_use = false;
	return -EINVAL;
	}
	break;
	case CRYPTO_CIPHER_MODE_CCM:
	ccm_ctx = &mtls_sessions[ctx_idx].mtls_ccm;
	mbedtls_ccm_init(ccm_ctx);
	ret = mbedtls_ccm_setkey(ccm_ctx, MBEDTLS_CIPHER_ID_AES,
	ctx->key.bit_stream, ctx->keylen * 8U);
	if (ret) {
	LOG_ERR("Could not setup the key (%d)", ret);
	mtls_sessions[ctx_idx].in_use = false;

	return -EINVAL;
	}
	if (op_type == CRYPTO_CIPHER_OP_ENCRYPT) {
	ctx->ops.ccm_crypt_hndlr = mtls_ccm_encrypt_auth;
	} else {
	ctx->ops.ccm_crypt_hndlr = mtls_ccm_decrypt_auth;
	}
	break;
	}

	mtls_sessions[ctx_idx].mode = mode;
	ctx->drv_sessn_state = &mtls_sessions[ctx_idx];

	return ret;
	}

	static int mtls_session_free(struct device dev, struct cipher_ctx ctx)
	{
	struct mtls_shim_session *mtls_session =
	(struct mtls_shim_session *)ctx->drv_sessn_state;

	if (mtls_session->mode == CRYPTO_CIPHER_MODE_CCM) {
	mbedtls_ccm_free(&mtls_session->mtls_ccm);
	} else {
	mbedtls_aes_free(&mtls_session->mtls_aes);
	}
	mtls_session->in_use = false;

	return 0;
	}

	static int mtls_query_caps(struct device *dev)
	{
	return MTLS_SUPPORT;
	}

	static int mtls_shim_init(struct device *dev)
	{
	return 0;
	}

	static struct crypto_driver_api mtls_crypto_funcs = {
	.begin_session = mtls_session_setup,
	.free_session = mtls_session_free,
	.crypto_async_callback_set = NULL,
	.query_hw_caps = mtls_query_caps,
	};

	DEVICE_AND_API_INIT(crypto_mtls, CONFIG_CRYPTO_MBEDTLS_SHIM_DRV_NAME,
	&mtls_shim_init, NULL, NULL,
	POST_KERNEL, CONFIG_CRYPTO_INIT_PRIORITY,
	(void *)&mtls_crypto_funcs);