264 lines
8.6 KiB
C
264 lines
8.6 KiB
C
/**
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* Cipher 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 aead_psa.c, which does the same
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* operations with the PSA Crypto 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 aead_psa.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 "mbedtls/cipher.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_CIPHER_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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int main( void )
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{
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printf( "MBEDTLS_MD_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\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_psa [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, unsigned char *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 an Mbed TLS function and bail out if it fails. */
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#define CHK( expr ) \
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do \
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{ \
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ret = ( expr ); \
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if( ret != 0 ) \
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{ \
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printf( "Error %d at line %d: %s\n", \
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ret, \
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__LINE__, \
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#expr ); \
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goto exit; \
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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: context and tag length, which together hold all the information
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*/
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static int aead_prepare( const char *info,
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mbedtls_cipher_context_t *ctx,
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size_t *tag_len )
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{
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int ret;
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/* Convert arg to type + tag_len */
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mbedtls_cipher_type_t type;
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if( strcmp( info, "aes128-gcm" ) == 0 ) {
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type = MBEDTLS_CIPHER_AES_128_GCM;
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*tag_len = 16;
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} else if( strcmp( info, "aes256-gcm" ) == 0 ) {
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type = MBEDTLS_CIPHER_AES_256_GCM;
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*tag_len = 16;
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} else if( strcmp( info, "aes128-gcm_8" ) == 0 ) {
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type = MBEDTLS_CIPHER_AES_128_GCM;
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*tag_len = 8;
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} else if( strcmp( info, "chachapoly" ) == 0 ) {
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type = MBEDTLS_CIPHER_CHACHA20_POLY1305;
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*tag_len = 16;
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} else {
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puts( usage );
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return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
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}
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/* Prepare context for the given type */
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CHK( mbedtls_cipher_setup( ctx,
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mbedtls_cipher_info_from_type( type ) ) );
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/* Import key */
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int key_len = mbedtls_cipher_get_key_bitlen( ctx );
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CHK( mbedtls_cipher_setkey( ctx, key_bytes, key_len, MBEDTLS_ENCRYPT ) );
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exit:
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return( ret );
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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 (ctx, tag_len).
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*/
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static void aead_info( const mbedtls_cipher_context_t *ctx, size_t tag_len )
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{
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// no convenient way to get the just cipher type (for example, AES)
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const char *ciph = "???";
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int key_bits = mbedtls_cipher_get_key_bitlen( ctx );
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mbedtls_cipher_mode_t mode = mbedtls_cipher_get_cipher_mode( ctx );
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const char *mode_str = mode == MBEDTLS_MODE_GCM ? "GCM"
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: mode == MBEDTLS_MODE_CHACHAPOLY ? "ChachaPoly"
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: "???";
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printf( "cipher: %s, %d, %s, %u\n", ciph, key_bits, mode_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( mbedtls_cipher_context_t *ctx, size_t tag_len,
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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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int ret;
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size_t olen;
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unsigned char out[MSG_MAX_SIZE + 16];
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unsigned char *p = out;
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CHK( mbedtls_cipher_set_iv( ctx, iv, iv_len ) );
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CHK( mbedtls_cipher_reset( ctx ) );
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CHK( mbedtls_cipher_update_ad( ctx, ad, ad_len ) );
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CHK( mbedtls_cipher_update( ctx, pa, pa_len, p, &olen ) );
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p += olen;
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CHK( mbedtls_cipher_update( ctx, pb, pb_len, p, &olen ) );
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p += olen;
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CHK( mbedtls_cipher_finish( ctx, p, &olen ) );
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p += olen;
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CHK( mbedtls_cipher_write_tag( ctx, p, tag_len ) );
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p += tag_len;
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olen = p - out;
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print_buf( "cipher", out, olen );
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exit:
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return( ret );
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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 int aead_demo( const char *info )
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{
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int ret = 0;
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mbedtls_cipher_context_t ctx;
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size_t tag_len;
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mbedtls_cipher_init( &ctx );
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CHK( aead_prepare( info, &ctx, &tag_len ) );
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aead_info( &ctx, tag_len );
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CHK( aead_encrypt( &ctx, tag_len,
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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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CHK( aead_encrypt( &ctx, tag_len,
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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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mbedtls_cipher_free( &ctx );
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return( ret );
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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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/* Check usage */
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if( argc != 2 )
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{
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puts( usage );
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return( 1 );
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}
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int ret;
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/* Run the demo */
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CHK( aead_demo( argv[1] ) );
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exit:
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return( ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE );
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}
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#endif
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