boot/bootutil/src/encrypted.c - mirror/mcuboot - TrustedFirmware Git Browser

 /*
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
  * distributed with this work for additional information
  * regarding copyright ownership.  The ASF licenses this file
  * to you under the Apache License, Version 2.0 (the
  * "License"); you may not use this file except in compliance
  * with the License.  You may obtain a copy of the License at
  *
  *  http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing,
  * software distributed under the License is distributed on an
  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  * KIND, either express or implied.  See the License for the
  * specific language governing permissions and limitations
  * under the License.
  */

 #include "mcuboot_config/mcuboot_config.h"

 #if defined(MCUBOOT_ENC_IMAGES)
 #include <assert.h>
 #include <stddef.h>
 #include <inttypes.h>
 #include <string.h>
 #include <stdio.h>

 #include "hal/hal_flash.h"

 #if defined(MCUBOOT_ENCRYPT_RSA)
 #include "mbedtls/rsa.h"
 #include "mbedtls/asn1.h"
 #endif

 #if defined(MCUBOOT_ENCRYPT_KW)
 #  if defined(MCUBOOT_USE_MBED_TLS)
 #    include "mbedtls/nist_kw.h"
 #    include "mbedtls/aes.h"
 #  else
 #    include "tinycrypt/aes.h"
 #  endif
 #endif

 #include "bootutil/image.h"
 #include "bootutil/enc_key.h"
 #include "bootutil/sign_key.h"

 #include "bootutil_priv.h"

 #define TLV_ENC_RSA_SZ  256
 #define TLV_ENC_KW_SZ   24

 #if defined(MCUBOOT_ENCRYPT_KW)
 #if defined(MCUBOOT_USE_MBED_TLS)
 int
 key_unwrap(uint8_t *wrapped, uint8_t *enckey)
 {
     mbedtls_nist_kw_context kw;
     int rc;
     size_t olen;

     mbedtls_nist_kw_init(&kw);

     rc = mbedtls_nist_kw_setkey(&kw, MBEDTLS_CIPHER_ID_AES,
             bootutil_enc_key.key, *bootutil_enc_key.len * 8, 0);
     if (rc) {
         goto done;
     }

     rc = mbedtls_nist_kw_unwrap(&kw, MBEDTLS_KW_MODE_KW, wrapped, TLV_ENC_KW_SZ,
             enckey, &olen, BOOT_ENC_KEY_SIZE);

 done:
     mbedtls_nist_kw_free(&kw);
     return rc;
 }
 #else /* !MCUBOOT_USE_MBED_TLS */
 /*
  * Implements AES key unwrapping following RFC-3394 section 2.2.2, using
  * tinycrypt for AES-128 decryption.
  */
 int
 key_unwrap(uint8_t *wrapped, uint8_t *enckey)
 {
     struct tc_aes_key_sched_struct aes;
     uint8_t A[8];
     uint8_t B[16];
     int8_t i, j, k;

     if (tc_aes128_set_decrypt_key(&aes, bootutil_enc_key.key) == 0) {
         return -1;
     }

     for (k = 0; k < 8; k++) {
         A[k]          = wrapped[k];
         enckey[k]     = wrapped[8 + k];
         enckey[8 + k] = wrapped[16 + k];
     }

     for (j = 5; j >= 0; j--) {
         for (i = 2; i > 0; i--) {
             for (k = 0; k < 8; k++) {
                 B[k] = A[k];
                 B[8 + k] = enckey[((i-1) * 8) + k];
             }
             B[7] ^= 2 * j + i;
             if (tc_aes_decrypt((uint8_t *)&B, (uint8_t *)&B, &aes) == 0) {
                 return -1;
             }
             for (k = 0; k < 8; k++) {
                 A[k] = B[k];
                 enckey[((i-1) * 8) + k] = B[8 + k];
             }
         }
     }

     for (i = 0, k = 0; i < 8; i++) {
         k |= A[i] ^ 0xa6;
     }
     if (k) {
         return -1;
     }
     return 0;
 }
 #endif /* MCUBOOT_USE_MBED_TLS */
 #endif /* MCUBOOT_ENCRYPT_KW */

 #if defined(MCUBOOT_ENCRYPT_RSA)
 static int
 parse_enckey(mbedtls_rsa_context *ctx, uint8_t **p, uint8_t *end)
 {
     int rc;
     size_t len;

     if ((rc = mbedtls_asn1_get_tag(p, end, &len,
                     MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE)) != 0) {
         return -1;
     }

     if (*p + len != end) {
         return -2;
     }

     if ( /* version */
         mbedtls_asn1_get_int(p, end, &ctx->ver) != 0 ||
          /* public modulus */
         mbedtls_asn1_get_mpi(p, end, &ctx->N) != 0 ||
          /* public exponent */
         mbedtls_asn1_get_mpi(p, end, &ctx->E) != 0 ||
          /* private exponent */
         mbedtls_asn1_get_mpi(p, end, &ctx->D) != 0 ||
          /* primes */
         mbedtls_asn1_get_mpi(p, end, &ctx->P) != 0 ||
         mbedtls_asn1_get_mpi(p, end, &ctx->Q) != 0 ||
          /* d mod (p-1) and d mod (q-1) */
         mbedtls_asn1_get_mpi(p, end, &ctx->DP) != 0 ||
         mbedtls_asn1_get_mpi(p, end, &ctx->DQ) != 0 ||
          /* q ^ (-1) mod p */
         mbedtls_asn1_get_mpi(p, end, &ctx->QP) != 0) {
         return -3;
     }

     ctx->len = mbedtls_mpi_size(&ctx->N);

     if (*p != end) {
         return -4;
     }

     if (mbedtls_rsa_check_pubkey(ctx) != 0 ||
         mbedtls_rsa_check_privkey(ctx) != 0) {
         return -5;
     }

     return 0;
 }
 #endif

 int
 boot_enc_set_key(struct enc_key_data *enc_state, uint8_t slot, uint8_t *enckey)
 {
     int rc;

 #if defined(MCUBOOT_USE_MBED_TLS)
     mbedtls_aes_init(&enc_state[slot].aes);
     rc = mbedtls_aes_setkey_enc(&enc_state[slot].aes, enckey, BOOT_ENC_KEY_SIZE_BITS);
     if (rc) {
         mbedtls_aes_free(&enc_state[slot].aes);
         return -1;
     }
 #else
     (void)rc;

     /* set_encrypt and set_decrypt do the same thing in tinycrypt */
     tc_aes128_set_encrypt_key(&enc_state[slot].aes, enckey);
 #endif

     enc_state[slot].valid = 1;

     return 0;
 }

 #if defined(MCUBOOT_ENCRYPT_RSA)
 #    define EXPECTED_ENC_TLV    IMAGE_TLV_ENC_RSA2048
 #    define EXPECTED_ENC_LEN    TLV_ENC_RSA_SZ
 #elif defined(MCUBOOT_ENCRYPT_KW)
 #    define EXPECTED_ENC_TLV    IMAGE_TLV_ENC_KW128
 #    define EXPECTED_ENC_LEN    TLV_ENC_KW_SZ
 #endif

 /*
  * Load encryption key.
  */
 int
 boot_enc_load(struct enc_key_data *enc_state, int image_index,
         const struct image_header *hdr, const struct flash_area *fap,
         uint8_t *enckey)
 {
 #if defined(MCUBOOT_ENCRYPT_RSA)
     mbedtls_rsa_context rsa;
     uint8_t *cp;
     uint8_t *cpend;
     size_t olen;
 #endif
     uint32_t off;
     uint32_t end;
     struct image_tlv_info info;
     struct image_tlv tlv;
     uint8_t buf[TLV_ENC_RSA_SZ];
     uint8_t slot;
     uint8_t enckey_type;
     int rc;

     rc = flash_area_id_to_multi_image_slot(image_index, fap->fa_id);
     if (rc < 0) {
         return rc;
     }
     slot = rc;

     /* Already loaded... */
     if (enc_state[slot].valid) {
         return 1;
     }

     off = hdr->ih_img_size + hdr->ih_hdr_size;

     rc = flash_area_read(fap, off, &info, sizeof(info));
     if (rc) {
         return rc;
     }
     if (info.it_magic != IMAGE_TLV_INFO_MAGIC) {
         return -1;
     }
     end = off + info.it_tlv_tot;
     off += sizeof(info);

     enckey_type = 0;
     for (; off < end; off += sizeof(tlv) + tlv.it_len) {
         rc = flash_area_read(fap, off, &tlv, sizeof tlv);
         if (rc) {
             return rc;
         }

         if (tlv.it_type == EXPECTED_ENC_TLV) {
             if (tlv.it_len != EXPECTED_ENC_LEN) {
                 return -1;
             }
             rc = flash_area_read(fap, off + sizeof(tlv), buf, EXPECTED_ENC_LEN);
             if (rc) {
                 return rc;
             }
             enckey_type = EXPECTED_ENC_TLV;
             break;
         }
     }

     if (enckey_type == 0) {
         return -1;
     }

     if (enckey_type == EXPECTED_ENC_TLV) {
 #if defined(MCUBOOT_ENCRYPT_RSA)
         mbedtls_rsa_init(&rsa, MBEDTLS_RSA_PKCS_V21, MBEDTLS_MD_SHA256);

         cp = (uint8_t *)bootutil_enc_key.key;
         cpend = cp + *bootutil_enc_key.len;

         rc = parse_enckey(&rsa, &cp, cpend);
         if (rc) {
             mbedtls_rsa_free(&rsa);
             return rc;
         }

         rc = mbedtls_rsa_rsaes_oaep_decrypt(&rsa, NULL, NULL, MBEDTLS_RSA_PRIVATE,
                 NULL, 0, &olen, buf, enckey, BOOT_ENC_KEY_SIZE);
         mbedtls_rsa_free(&rsa);

 #elif defined(MCUBOOT_ENCRYPT_KW)
         assert(*bootutil_enc_key.len == 16);
         rc = key_unwrap(buf, enckey);
 #endif
     }

     return rc;
 }

 bool
 boot_enc_valid(struct enc_key_data *enc_state, int image_index,
         const struct flash_area *fap)
 {
     int rc;

     rc = flash_area_id_to_multi_image_slot(image_index, fap->fa_id);
     if (rc < 0) {
         /* can't get proper slot number - skip encryption, */
         /* postpone the error for a upper layer */
         return false;
     }

     return enc_state[rc].valid;
 }

 void
 boot_enc_mark_keys_invalid(struct enc_key_data *enc_state)
 {
     size_t slot;

     for(slot = 0; slot < BOOT_NUM_SLOTS; ++slot) {
         enc_state[slot].valid = 0;
     }
 }

 void
 boot_encrypt(struct enc_key_data *enc_state, int image_index,
         const struct flash_area *fap, uint32_t off, uint32_t sz,
         uint32_t blk_off, uint8_t *buf)
 {
     struct enc_key_data *enc;
     uint32_t i, j;
     uint8_t u8;
     uint8_t nonce[16];
     uint8_t blk[16];
     int rc;

     memset(nonce, 0, 12);
     off >>= 4;
     nonce[12] = (uint8_t)(off >> 24);
     nonce[13] = (uint8_t)(off >> 16);
     nonce[14] = (uint8_t)(off >> 8);
     nonce[15] = (uint8_t)off;

     rc = flash_area_id_to_multi_image_slot(image_index, fap->fa_id);
     if (rc < 0) {
         assert(0);
         return;
     }

     enc = &enc_state[rc];
     assert(enc->valid == 1);
     for (i = 0; i < sz; i++) {
         if (i == 0 || blk_off == 0) {
 #if defined(MCUBOOT_USE_MBED_TLS)
             mbedtls_aes_crypt_ecb(&enc->aes, MBEDTLS_AES_ENCRYPT, nonce, blk);
 #else
             tc_aes_encrypt(blk, nonce, &enc->aes);
 #endif

             for (j = 16; j > 0; --j) {
                 if (++nonce[j - 1] != 0) {
                     break;
                 }
             }
         }

         u8 = *buf;
         *buf++ = u8 ^ blk[blk_off];
         blk_off = (blk_off + 1) & 0x0f;
     }
 }

 /**
  * Clears encrypted state after use.
  */
 void boot_enc_zeroize(struct enc_key_data *enc_state)
 {
     memset(enc_state, 0, sizeof(struct enc_key_data) * BOOT_NUM_SLOTS);
 }

 #endif /* MCUBOOT_ENC_IMAGES */
	/*
	* Licensed to the Apache Software Foundation (ASF) under one
	* or more contributor license agreements. See the NOTICE file
	* distributed with this work for additional information
	* regarding copyright ownership. The ASF licenses this file
	* to you under the Apache License, Version 2.0 (the
	* "License"); you may not use this file except in compliance
	* with the License. You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing,
	* software distributed under the License is distributed on an
	* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
	* KIND, either express or implied. See the License for the
	* specific language governing permissions and limitations
	* under the License.
	*/

	#include "mcuboot_config/mcuboot_config.h"

	#if defined(MCUBOOT_ENC_IMAGES)
	#include <assert.h>
	#include <stddef.h>
	#include <inttypes.h>
	#include <string.h>
	#include <stdio.h>

	#include "hal/hal_flash.h"

	#if defined(MCUBOOT_ENCRYPT_RSA)
	#include "mbedtls/rsa.h"
	#include "mbedtls/asn1.h"
	#endif

	#if defined(MCUBOOT_ENCRYPT_KW)
	# if defined(MCUBOOT_USE_MBED_TLS)
	# include "mbedtls/nist_kw.h"
	# include "mbedtls/aes.h"
	# else
	# include "tinycrypt/aes.h"
	# endif
	#endif

	#include "bootutil/image.h"
	#include "bootutil/enc_key.h"
	#include "bootutil/sign_key.h"

	#include "bootutil_priv.h"

	#define TLV_ENC_RSA_SZ 256
	#define TLV_ENC_KW_SZ 24

	#if defined(MCUBOOT_ENCRYPT_KW)
	#if defined(MCUBOOT_USE_MBED_TLS)
	int
	key_unwrap(uint8_t wrapped, uint8_t enckey)
	{
	mbedtls_nist_kw_context kw;
	int rc;
	size_t olen;

	mbedtls_nist_kw_init(&kw);

	rc = mbedtls_nist_kw_setkey(&kw, MBEDTLS_CIPHER_ID_AES,
	bootutil_enc_key.key, bootutil_enc_key.len 8, 0);
	if (rc) {
	goto done;
	}

	rc = mbedtls_nist_kw_unwrap(&kw, MBEDTLS_KW_MODE_KW, wrapped, TLV_ENC_KW_SZ,
	enckey, &olen, BOOT_ENC_KEY_SIZE);

	done:
	mbedtls_nist_kw_free(&kw);
	return rc;
	}
	#else /* !MCUBOOT_USE_MBED_TLS */
	/*
	* Implements AES key unwrapping following RFC-3394 section 2.2.2, using
	* tinycrypt for AES-128 decryption.
	*/
	int
	key_unwrap(uint8_t wrapped, uint8_t enckey)
	{
	struct tc_aes_key_sched_struct aes;
	uint8_t A[8];
	uint8_t B[16];
	int8_t i, j, k;

	if (tc_aes128_set_decrypt_key(&aes, bootutil_enc_key.key) == 0) {
	return -1;
	}

	for (k = 0; k < 8; k++) {
	A[k] = wrapped[k];
	enckey[k] = wrapped[8 + k];
	enckey[8 + k] = wrapped[16 + k];
	}

	for (j = 5; j >= 0; j--) {
	for (i = 2; i > 0; i--) {
	for (k = 0; k < 8; k++) {
	B[k] = A[k];
	B[8 + k] = enckey[((i-1) * 8) + k];
	}
	B[7] ^= 2 * j + i;
	if (tc_aes_decrypt((uint8_t )&B, (uint8_t )&B, &aes) == 0) {
	return -1;
	}
	for (k = 0; k < 8; k++) {
	A[k] = B[k];
	enckey[((i-1) * 8) + k] = B[8 + k];
	}
	}
	}

	for (i = 0, k = 0; i < 8; i++) {
	k \|= A[i] ^ 0xa6;
	}
	if (k) {
	return -1;
	}
	return 0;
	}
	#endif /* MCUBOOT_USE_MBED_TLS */
	#endif /* MCUBOOT_ENCRYPT_KW */

	#if defined(MCUBOOT_ENCRYPT_RSA)
	static int
	parse_enckey(mbedtls_rsa_context ctx, uint8_t p, uint8_t end)
	{
	int rc;
	size_t len;

	if ((rc = mbedtls_asn1_get_tag(p, end, &len,
	MBEDTLS_ASN1_CONSTRUCTED \| MBEDTLS_ASN1_SEQUENCE)) != 0) {
	return -1;
	}

	if (*p + len != end) {
	return -2;
	}

	if ( /* version */
	mbedtls_asn1_get_int(p, end, &ctx->ver) != 0 \|\|
	/* public modulus */
	mbedtls_asn1_get_mpi(p, end, &ctx->N) != 0 \|\|
	/* public exponent */
	mbedtls_asn1_get_mpi(p, end, &ctx->E) != 0 \|\|
	/* private exponent */
	mbedtls_asn1_get_mpi(p, end, &ctx->D) != 0 \|\|
	/* primes */
	mbedtls_asn1_get_mpi(p, end, &ctx->P) != 0 \|\|
	mbedtls_asn1_get_mpi(p, end, &ctx->Q) != 0 \|\|
	/* d mod (p-1) and d mod (q-1) */
	mbedtls_asn1_get_mpi(p, end, &ctx->DP) != 0 \|\|
	mbedtls_asn1_get_mpi(p, end, &ctx->DQ) != 0 \|\|
	/* q ^ (-1) mod p */
	mbedtls_asn1_get_mpi(p, end, &ctx->QP) != 0) {
	return -3;
	}

	ctx->len = mbedtls_mpi_size(&ctx->N);

	if (*p != end) {
	return -4;
	}

	if (mbedtls_rsa_check_pubkey(ctx) != 0 \|\|
	mbedtls_rsa_check_privkey(ctx) != 0) {
	return -5;
	}

	return 0;
	}
	#endif

	int
	boot_enc_set_key(struct enc_key_data enc_state, uint8_t slot, uint8_t enckey)
	{
	int rc;

	#if defined(MCUBOOT_USE_MBED_TLS)
	mbedtls_aes_init(&enc_state[slot].aes);
	rc = mbedtls_aes_setkey_enc(&enc_state[slot].aes, enckey, BOOT_ENC_KEY_SIZE_BITS);
	if (rc) {
	mbedtls_aes_free(&enc_state[slot].aes);
	return -1;
	}
	#else
	(void)rc;

	/* set_encrypt and set_decrypt do the same thing in tinycrypt */
	tc_aes128_set_encrypt_key(&enc_state[slot].aes, enckey);
	#endif

	enc_state[slot].valid = 1;

	return 0;
	}

	#if defined(MCUBOOT_ENCRYPT_RSA)
	# define EXPECTED_ENC_TLV IMAGE_TLV_ENC_RSA2048
	# define EXPECTED_ENC_LEN TLV_ENC_RSA_SZ
	#elif defined(MCUBOOT_ENCRYPT_KW)
	# define EXPECTED_ENC_TLV IMAGE_TLV_ENC_KW128
	# define EXPECTED_ENC_LEN TLV_ENC_KW_SZ
	#endif

	/*
	* Load encryption key.
	*/
	int
	boot_enc_load(struct enc_key_data *enc_state, int image_index,
	const struct image_header hdr, const struct flash_area fap,
	uint8_t *enckey)
	{
	#if defined(MCUBOOT_ENCRYPT_RSA)
	mbedtls_rsa_context rsa;
	uint8_t *cp;
	uint8_t *cpend;
	size_t olen;
	#endif
	uint32_t off;
	uint32_t end;
	struct image_tlv_info info;
	struct image_tlv tlv;
	uint8_t buf[TLV_ENC_RSA_SZ];
	uint8_t slot;
	uint8_t enckey_type;
	int rc;

	rc = flash_area_id_to_multi_image_slot(image_index, fap->fa_id);
	if (rc < 0) {
	return rc;
	}
	slot = rc;

	/* Already loaded... */
	if (enc_state[slot].valid) {
	return 1;
	}

	off = hdr->ih_img_size + hdr->ih_hdr_size;

	rc = flash_area_read(fap, off, &info, sizeof(info));
	if (rc) {
	return rc;
	}
	if (info.it_magic != IMAGE_TLV_INFO_MAGIC) {
	return -1;
	}
	end = off + info.it_tlv_tot;
	off += sizeof(info);

	enckey_type = 0;
	for (; off < end; off += sizeof(tlv) + tlv.it_len) {
	rc = flash_area_read(fap, off, &tlv, sizeof tlv);
	if (rc) {
	return rc;
	}

	if (tlv.it_type == EXPECTED_ENC_TLV) {
	if (tlv.it_len != EXPECTED_ENC_LEN) {
	return -1;
	}
	rc = flash_area_read(fap, off + sizeof(tlv), buf, EXPECTED_ENC_LEN);
	if (rc) {
	return rc;
	}
	enckey_type = EXPECTED_ENC_TLV;
	break;
	}
	}

	if (enckey_type == 0) {
	return -1;
	}

	if (enckey_type == EXPECTED_ENC_TLV) {
	#if defined(MCUBOOT_ENCRYPT_RSA)
	mbedtls_rsa_init(&rsa, MBEDTLS_RSA_PKCS_V21, MBEDTLS_MD_SHA256);

	cp = (uint8_t *)bootutil_enc_key.key;
	cpend = cp + *bootutil_enc_key.len;

	rc = parse_enckey(&rsa, &cp, cpend);
	if (rc) {
	mbedtls_rsa_free(&rsa);
	return rc;
	}

	rc = mbedtls_rsa_rsaes_oaep_decrypt(&rsa, NULL, NULL, MBEDTLS_RSA_PRIVATE,
	NULL, 0, &olen, buf, enckey, BOOT_ENC_KEY_SIZE);
	mbedtls_rsa_free(&rsa);

	#elif defined(MCUBOOT_ENCRYPT_KW)
	assert(*bootutil_enc_key.len == 16);
	rc = key_unwrap(buf, enckey);
	#endif
	}

	return rc;
	}

	bool
	boot_enc_valid(struct enc_key_data *enc_state, int image_index,
	const struct flash_area *fap)
	{
	int rc;

	rc = flash_area_id_to_multi_image_slot(image_index, fap->fa_id);
	if (rc < 0) {
	/* can't get proper slot number - skip encryption, */
	/* postpone the error for a upper layer */
	return false;
	}

	return enc_state[rc].valid;
	}

	void
	boot_enc_mark_keys_invalid(struct enc_key_data *enc_state)
	{
	size_t slot;

	for(slot = 0; slot < BOOT_NUM_SLOTS; ++slot) {
	enc_state[slot].valid = 0;
	}
	}

	void
	boot_encrypt(struct enc_key_data *enc_state, int image_index,
	const struct flash_area *fap, uint32_t off, uint32_t sz,
	uint32_t blk_off, uint8_t *buf)
	{
	struct enc_key_data *enc;
	uint32_t i, j;
	uint8_t u8;
	uint8_t nonce[16];
	uint8_t blk[16];
	int rc;

	memset(nonce, 0, 12);
	off >>= 4;
	nonce[12] = (uint8_t)(off >> 24);
	nonce[13] = (uint8_t)(off >> 16);
	nonce[14] = (uint8_t)(off >> 8);
	nonce[15] = (uint8_t)off;

	rc = flash_area_id_to_multi_image_slot(image_index, fap->fa_id);
	if (rc < 0) {
	assert(0);
	return;
	}

	enc = &enc_state[rc];
	assert(enc->valid == 1);
	for (i = 0; i < sz; i++) {
	if (i == 0 \|\| blk_off == 0) {
	#if defined(MCUBOOT_USE_MBED_TLS)
	mbedtls_aes_crypt_ecb(&enc->aes, MBEDTLS_AES_ENCRYPT, nonce, blk);
	#else
	tc_aes_encrypt(blk, nonce, &enc->aes);
	#endif

	for (j = 16; j > 0; --j) {
	if (++nonce[j - 1] != 0) {
	break;
	}
	}
	}

	u8 = *buf;
	*buf++ = u8 ^ blk[blk_off];
	blk_off = (blk_off + 1) & 0x0f;
	}
	}

	/**
	* Clears encrypted state after use.
	*/
	void boot_enc_zeroize(struct enc_key_data *enc_state)
	{
	memset(enc_state, 0, sizeof(struct enc_key_data) * BOOT_NUM_SLOTS);
	}

	#endif /* MCUBOOT_ENC_IMAGES */