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Diffstat (limited to 'programs/hash/md_hmac_demo.c')
| -rw-r--r-- | programs/hash/md_hmac_demo.c | 147 |
1 files changed, 147 insertions, 0 deletions
diff --git a/programs/hash/md_hmac_demo.c b/programs/hash/md_hmac_demo.c new file mode 100644 index 000000000..d4cc3ccd4 --- /dev/null +++ b/programs/hash/md_hmac_demo.c @@ -0,0 +1,147 @@ +/** + * MD API multi-part HMAC demonstration. + * + * This programs computes the HMAC of two messages using the multi-part API. + * + * This is a companion to psa/hmac_demo.c, doing the same operations with the + * legacy MD API. The goal is that comparing the two programs will help people + * migrating to the PSA Crypto API. + * + * When it comes to multi-part HMAC operations, the `mbedtls_md_context` + * serves a dual purpose (1) hold the key, and (2) save progress information + * for the current operation. With PSA those roles are held by two disinct + * objects: (1) a psa_key_id_t to hold the key, and (2) a psa_operation_t for + * multi-part progress. + * + * This program and its companion psa/hmac_demo.c illustrate this by doing the + * same sequence of multi-part HMAC computation with both APIs; looking at the + * two side by side should make the differences and similarities clear. + */ + +/* + * Copyright The Mbed TLS Contributors + * SPDX-License-Identifier: Apache-2.0 + * + * Licensed 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. + */ + +/* First include Mbed TLS headers to get the Mbed TLS configuration and + * platform definitions that we'll use in this program. Also include + * standard C headers for functions we'll use here. */ +#include "mbedtls/build_info.h" + +#include "mbedtls/md.h" + +#include "mbedtls/platform_util.h" // for mbedtls_platform_zeroize + +#include <stdlib.h> +#include <stdio.h> + +/* If the build options we need are not enabled, compile a placeholder. */ +#if !defined(MBEDTLS_MD_C) +int main( void ) +{ + printf( "MBEDTLS_MD_C not defined\r\n" ); + return( 0 ); +} +#else + +/* The real program starts here. */ + +/* Dummy inputs for HMAC */ +const unsigned char msg1_part1[] = { 0x01, 0x02 }; +const unsigned char msg1_part2[] = { 0x03, 0x04 }; +const unsigned char msg2_part1[] = { 0x05, 0x05 }; +const unsigned char msg2_part2[] = { 0x06, 0x06 }; + +/* Dummy key material - never do this in production! + * This example program uses SHA-256, so a 32-byte key makes sense. */ +const unsigned char key_bytes[32] = { 0 }; + +/* Print the contents of a buffer in hex */ +void print_buf( const char *title, unsigned char *buf, size_t len ) +{ + printf( "%s:", title ); + for( size_t i = 0; i < len; i++ ) + printf( " %02x", buf[i] ); + printf( "\n" ); +} + +/* Run an Mbed TLS function and bail out if it fails. + * A string description of the error code can be recovered with: + * programs/util/strerror <value> */ +#define CHK( expr ) \ + do \ + { \ + ret = ( expr ); \ + if( ret != 0 ) \ + { \ + printf( "Error %d at line %d: %s\n", \ + ret, \ + __LINE__, \ + #expr ); \ + goto exit; \ + } \ + } while( 0 ) + +/* + * This function demonstrates computation of the HMAC of two messages using + * the multipart API. + */ +int hmac_demo(void) +{ + int ret; + const mbedtls_md_type_t alg = MBEDTLS_MD_SHA256; + unsigned char out[MBEDTLS_MD_MAX_SIZE]; // safe but not optimal + + mbedtls_md_context_t ctx; + + mbedtls_md_init( &ctx ); + + /* prepare context and load key */ + // the last argument to setup is 1 to enable HMAC (not just hashing) + const mbedtls_md_info_t *info = mbedtls_md_info_from_type( alg ); + CHK( mbedtls_md_setup( &ctx, info, 1 ) ); + CHK( mbedtls_md_hmac_starts( &ctx, key_bytes, sizeof( key_bytes ) ) ); + + /* compute HMAC(key, msg1_part1 | msg1_part2) */ + CHK( mbedtls_md_hmac_update( &ctx, msg1_part1, sizeof( msg1_part1 ) ) ); + CHK( mbedtls_md_hmac_update( &ctx, msg1_part2, sizeof( msg1_part2 ) ) ); + CHK( mbedtls_md_hmac_finish( &ctx, out ) ); + print_buf( "msg1", out, mbedtls_md_get_size( info ) ); + + /* compute HMAC(key, msg2_part1 | msg2_part2) */ + CHK( mbedtls_md_hmac_reset( &ctx ) ); // prepare for new operation + CHK( mbedtls_md_hmac_update( &ctx, msg2_part1, sizeof( msg2_part1 ) ) ); + CHK( mbedtls_md_hmac_update( &ctx, msg2_part2, sizeof( msg2_part2 ) ) ); + CHK( mbedtls_md_hmac_finish( &ctx, out ) ); + print_buf( "msg2", out, mbedtls_md_get_size( info ) ); + +exit: + mbedtls_md_free( &ctx ); + mbedtls_platform_zeroize( out, sizeof( out ) ); + + return( ret ); +} + +int main(void) +{ + int ret; + + CHK( hmac_demo() ); + +exit: + return( ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE ); +} + +#endif |