288 lines
9.9 KiB
C
288 lines
9.9 KiB
C
/**
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* PSA API multi-part AEAD demonstration.
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*
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* This program AEAD-encrypts a message, using the algorithm and key size
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* specified on the command line, using the multi-part API.
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*
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* It comes with a companion program cipher/aead_demo.c, which does the same
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* operations with the legacy Cipher API. The goal is that comparing the two
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* programs will help people migrating to the PSA Crypto API.
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*
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* When used with multi-part AEAD operations, the `mbedtls_cipher_context`
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* serves a triple purpose (1) hold the key, (2) store the algorithm when no
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* operation is active, and (3) save progress information for the current
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* operation. With PSA those roles are held by disinct objects: (1) a
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* psa_key_id_t to hold the key, a (2) psa_algorithm_t to represent the
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* algorithm, and (3) a psa_operation_t for multi-part progress.
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*
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* On the other hand, with PSA, the algorithms encodes the desired tag length;
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* with Cipher the desired tag length needs to be tracked separately.
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*
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* This program and its companion cipher/aead_demo.c illustrate this by doing the
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* same sequence of multi-part AEAD computation with both APIs; looking at the
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* two side by side should make the differences and similarities clear.
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*/
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/*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/* First include Mbed TLS headers to get the Mbed TLS configuration and
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* platform definitions that we'll use in this program. Also include
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* standard C headers for functions we'll use here. */
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#include "mbedtls/build_info.h"
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#include "psa/crypto.h"
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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/* If the build options we need are not enabled, compile a placeholder. */
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#if !defined(MBEDTLS_PSA_CRYPTO_C) || \
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!defined(MBEDTLS_AES_C) || !defined(MBEDTLS_GCM_C) || \
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!defined(MBEDTLS_CHACHAPOLY_C) || \
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defined(MBEDTLS_PSA_CRYPTO_KEY_ID_ENCODES_OWNER)
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int main( void )
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{
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printf( "MBEDTLS_PSA_CRYPTO_C and/or "
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"MBEDTLS_AES_C and/or MBEDTLS_GCM_C and/or "
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"MBEDTLS_CHACHAPOLY_C not defined, and/or "
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"MBEDTLS_PSA_CRYPTO_KEY_ID_ENCODES_OWNER defined\r\n" );
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return( 0 );
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}
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#else
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/* The real program starts here. */
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const char usage[] = "Usage: aead_demo [aes128-gcm|aes256-gcm|aes128-gcm_8|chachapoly]";
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/* Dummy data for encryption: IV/nonce, additional data, 2-part message */
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const unsigned char iv1[12] = { 0x00 };
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const unsigned char add_data1[] = { 0x01, 0x02 };
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const unsigned char msg1_part1[] = { 0x03, 0x04 };
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const unsigned char msg1_part2[] = { 0x05, 0x06, 0x07 };
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/* Dummy data (2nd message) */
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const unsigned char iv2[12] = { 0x10 };
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const unsigned char add_data2[] = { 0x11, 0x12 };
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const unsigned char msg2_part1[] = { 0x13, 0x14 };
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const unsigned char msg2_part2[] = { 0x15, 0x16, 0x17 };
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/* This must at least the sum of the length of the 2 parts for each message.
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* This is a macro for the sake of compilers with insufficient C99 support. */
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#define MSG_MAX_SIZE 5
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/* Dummy key material - never do this in production!
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* 32-byte is enough to all the key size supported by this program. */
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const unsigned char key_bytes[32] = { 0x2a };
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/* Print the contents of a buffer in hex */
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void print_buf( const char *title, uint8_t *buf, size_t len )
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{
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printf( "%s:", title );
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for( size_t i = 0; i < len; i++ )
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printf( " %02x", buf[i] );
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printf( "\n" );
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}
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/* Run a PSA function and bail out if it fails. */
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#define PSA_CHECK( expr ) \
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do \
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{ \
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status = ( expr ); \
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if( status != PSA_SUCCESS ) \
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{ \
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printf( "Error %d at line %d: %s\n", \
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(int) status, \
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__LINE__, \
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#expr ); \
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goto exit; \
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} \
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} \
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while( 0 )
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/*
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* Prepare encryption material:
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* - interpret command-line argument
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* - set up key
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* - outputs: key and algorithm, which together hold all the information
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*/
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static psa_status_t aead_prepare( const char *info,
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psa_key_id_t *key,
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psa_algorithm_t *alg )
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{
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psa_status_t status;
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/* Convert arg to alg + key_bits + key_type */
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size_t key_bits;
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psa_key_type_t key_type;
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if( strcmp( info, "aes128-gcm" ) == 0 ) {
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*alg = PSA_ALG_GCM;
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key_bits = 128;
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key_type = PSA_KEY_TYPE_AES;
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} else if( strcmp( info, "aes256-gcm" ) == 0 ) {
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*alg = PSA_ALG_GCM;
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key_bits = 256;
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key_type = PSA_KEY_TYPE_AES;
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} else if( strcmp( info, "aes128-gcm_8" ) == 0 ) {
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*alg = PSA_ALG_AEAD_WITH_SHORTENED_TAG(PSA_ALG_GCM, 8);
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key_bits = 128;
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key_type = PSA_KEY_TYPE_AES;
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} else if( strcmp( info, "chachapoly" ) == 0 ) {
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*alg = PSA_ALG_CHACHA20_POLY1305;
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key_bits = 256;
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key_type = PSA_KEY_TYPE_CHACHA20;
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} else {
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puts( usage );
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return( PSA_ERROR_INVALID_ARGUMENT );
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}
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/* Prepare key attibutes */
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psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
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psa_set_key_usage_flags( &attributes, PSA_KEY_USAGE_ENCRYPT );
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psa_set_key_algorithm( &attributes, *alg );
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psa_set_key_type( &attributes, key_type );
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psa_set_key_bits( &attributes, key_bits ); // optional
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/* Import key */
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PSA_CHECK( psa_import_key( &attributes, key_bytes, key_bits / 8, key ) );
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exit:
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return( status );
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}
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/*
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* Print out some information.
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*
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* All of this information was present in the command line argument, but his
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* function demonstrates how each piece can be recovered from (key, alg).
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*/
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static void aead_info( psa_key_id_t key, psa_algorithm_t alg )
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{
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psa_key_attributes_t attr = PSA_KEY_ATTRIBUTES_INIT;
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(void) psa_get_key_attributes( key, &attr );
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psa_key_type_t key_type = psa_get_key_type( &attr );
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size_t key_bits = psa_get_key_bits( &attr );
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psa_algorithm_t base_alg = PSA_ALG_AEAD_WITH_DEFAULT_LENGTH_TAG( alg );
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size_t tag_len = PSA_AEAD_TAG_LENGTH( key_type, key_bits, alg );
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const char *type_str = key_type == PSA_KEY_TYPE_AES ? "AES"
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: key_type == PSA_KEY_TYPE_CHACHA20 ? "Chacha"
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: "???";
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const char *base_str = base_alg == PSA_ALG_GCM ? "GCM"
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: base_alg == PSA_ALG_CHACHA20_POLY1305 ? "ChachaPoly"
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: "???";
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printf( "%s, %u, %s, %u\n",
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type_str, (unsigned) key_bits, base_str, (unsigned) tag_len );
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}
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/*
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* Encrypt a 2-part message.
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*/
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static int aead_encrypt( psa_key_id_t key, psa_algorithm_t alg,
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const unsigned char *iv, size_t iv_len,
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const unsigned char *ad, size_t ad_len,
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const unsigned char *pa, size_t pa_len,
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const unsigned char *pb, size_t pb_len )
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{
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psa_status_t status;
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size_t olen, olen_tag;
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unsigned char out[PSA_AEAD_ENCRYPT_OUTPUT_MAX_SIZE(MSG_MAX_SIZE)];
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unsigned char *p = out, *end = out + sizeof( out );
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unsigned char tag[PSA_AEAD_TAG_MAX_SIZE];
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psa_aead_operation_t op = PSA_AEAD_OPERATION_INIT;
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PSA_CHECK( psa_aead_encrypt_setup( &op, key, alg ) );
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PSA_CHECK( psa_aead_set_nonce( &op, iv, iv_len ) );
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PSA_CHECK( psa_aead_update_ad( &op, ad, ad_len ) );
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PSA_CHECK( psa_aead_update( &op, pa, pa_len, p, end - p, &olen ) );
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p += olen;
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PSA_CHECK( psa_aead_update( &op, pb, pb_len, p, end - p, &olen ) );
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p += olen;
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PSA_CHECK( psa_aead_finish( &op, p, end - p, &olen,
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tag, sizeof( tag ), &olen_tag ) );
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p += olen;
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memcpy( p, tag, olen_tag );
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p += olen_tag;
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olen = p - out;
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print_buf( "out", out, olen );
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exit:
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psa_aead_abort( &op ); // required on errors, harmless on success
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return( status );
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}
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/*
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* AEAD demo: set up key/alg, print out info, encrypt messages.
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*/
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static psa_status_t aead_demo( const char *info )
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{
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psa_status_t status;
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psa_key_id_t key;
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psa_algorithm_t alg;
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PSA_CHECK( aead_prepare( info, &key, &alg ) );
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aead_info( key, alg );
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PSA_CHECK( aead_encrypt( key, alg,
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iv1, sizeof( iv1 ), add_data1, sizeof( add_data1 ),
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msg1_part1, sizeof( msg1_part1 ),
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msg1_part2, sizeof( msg1_part2 ) ) );
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PSA_CHECK( aead_encrypt( key, alg,
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iv2, sizeof( iv2 ), add_data2, sizeof( add_data2 ),
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msg2_part1, sizeof( msg2_part1 ),
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msg2_part2, sizeof( msg2_part2 ) ) );
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exit:
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psa_destroy_key( key );
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return( status );
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}
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/*
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* Main function
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*/
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int main( int argc, char **argv )
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{
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psa_status_t status = PSA_SUCCESS;
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/* Check usage */
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if( argc != 2 )
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{
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puts( usage );
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return( EXIT_FAILURE );
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}
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/* Initialize the PSA crypto library. */
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PSA_CHECK( psa_crypto_init( ) );
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/* Run the demo */
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PSA_CHECK( aead_demo( argv[1] ) );
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/* Deinitialize the PSA crypto library. */
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mbedtls_psa_crypto_free( );
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exit:
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return( status == PSA_SUCCESS ? EXIT_SUCCESS : EXIT_FAILURE );
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}
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#endif
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