293 lines
10 KiB
C
293 lines
10 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/cipher_aead_demo.c, which does the
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* same operations with the legacy Cipher API. The goal is that comparing the
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* two 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/cipher_aead_demo.c illustrate this by
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* doing the same sequence of multi-part AEAD computation with both APIs;
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* looking at the two side by side should make the differences and
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* 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[] =
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"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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/* Maximum total size of the messages */
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#define MSG1_SIZE (sizeof(msg1_part1) + sizeof(msg1_part2))
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#define MSG2_SIZE (sizeof(msg2_part1) + sizeof(msg2_part2))
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#define MSG_MAX_SIZE (MSG1_SIZE > MSG2_SIZE ? MSG1_SIZE : MSG2_SIZE)
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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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}
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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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* The symbolic name of the error code can be recovered using:
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* programs/psa/psa_constant_name status <value> */
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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 attributes */
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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 *part1, size_t part1_len,
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const unsigned char *part2, size_t part2_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, part1, part1_len, p, end - p, &olen));
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p += olen;
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PSA_CHECK(psa_aead_update(&op, part2, part2_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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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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