/**
* PSA API multi-part AEAD demonstration.
*
* This program AEAD-encrypts a message, using the algorithm and key size
* specified on the command line, using the multi-part API.
*
* It comes with a companion program cipher/cipher_aead_demo.c, which does the
* same operations with the legacy Cipher API. The goal is that comparing the
* two programs will help people migrating to the PSA Crypto API.
*
* When used with multi-part AEAD operations, the `mbedtls_cipher_context`
* serves a triple purpose (1) hold the key, (2) store the algorithm when no
* operation is active, and (3) save progress information for the current
* operation. With PSA those roles are held by disinct objects: (1) a
* psa_key_id_t to hold the key, a (2) psa_algorithm_t to represent the
* algorithm, and (3) a psa_operation_t for multi-part progress.
*
* On the other hand, with PSA, the algorithms encodes the desired tag length;
* with Cipher the desired tag length needs to be tracked separately.
*
* This program and its companion cipher/cipher_aead_demo.c illustrate this by
* doing the same sequence of multi-part AEAD 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 OR GPL-2.0-or-later
*/
/* 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 "psa/crypto.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
/* If the build options we need are not enabled, compile a placeholder. */
#if !defined(MBEDTLS_PSA_CRYPTO_C) || \
!defined(MBEDTLS_AES_C) || !defined(MBEDTLS_GCM_C) || \
!defined(MBEDTLS_CHACHAPOLY_C) || \
defined(MBEDTLS_PSA_CRYPTO_KEY_ID_ENCODES_OWNER)
int main(void)
{
printf("MBEDTLS_PSA_CRYPTO_C and/or "
"MBEDTLS_AES_C and/or MBEDTLS_GCM_C and/or "
"MBEDTLS_CHACHAPOLY_C not defined, and/or "
"MBEDTLS_PSA_CRYPTO_KEY_ID_ENCODES_OWNER defined\r\n");
return 0;
}
#else
/* The real program starts here. */
const char usage[] =
"Usage: aead_demo [aes128-gcm|aes256-gcm|aes128-gcm_8|chachapoly]";
/* Dummy data for encryption: IV/nonce, additional data, 2-part message */
const unsigned char iv1[12] = { 0x00 };
const unsigned char add_data1[] = { 0x01, 0x02 };
const unsigned char msg1_part1[] = { 0x03, 0x04 };
const unsigned char msg1_part2[] = { 0x05, 0x06, 0x07 };
/* Dummy data (2nd message) */
const unsigned char iv2[12] = { 0x10 };
const unsigned char add_data2[] = { 0x11, 0x12 };
const unsigned char msg2_part1[] = { 0x13, 0x14 };
const unsigned char msg2_part2[] = { 0x15, 0x16, 0x17 };
/* Maximum total size of the messages */
#define MSG1_SIZE (sizeof(msg1_part1) + sizeof(msg1_part2))
#define MSG2_SIZE (sizeof(msg2_part1) + sizeof(msg2_part2))
#define MSG_MAX_SIZE (MSG1_SIZE > MSG2_SIZE ? MSG1_SIZE : MSG2_SIZE)
/* Dummy key material - never do this in production!
* 32-byte is enough to all the key size supported by this program. */
const unsigned char key_bytes[32] = { 0x2a };
/* Print the contents of a buffer in hex */
static void print_buf(const char *title, uint8_t *buf, size_t len)
{
printf("%s:", title);
for (size_t i = 0; i < len; i++) {
printf(" %02x", buf[i]);
}
printf("\n");
}
/* Run a PSA function and bail out if it fails.
* The symbolic name of the error code can be recovered using:
* programs/psa/psa_constant_name status <value> */
#define PSA_CHECK(expr) \
do \
{ \
status = (expr); \
if (status != PSA_SUCCESS) \
{ \
printf("Error %d at line %d: %s\n", \
(int) status, \
__LINE__, \
#expr); \
goto exit; \
} \
} \
while (0)
/*
* Prepare encryption material:
* - interpret command-line argument
* - set up key
* - outputs: key and algorithm, which together hold all the information
*/
static psa_status_t aead_prepare(const char *info,
psa_key_id_t *key,
psa_algorithm_t *alg)
{
psa_status_t status;
/* Convert arg to alg + key_bits + key_type */
size_t key_bits;
psa_key_type_t key_type;
if (strcmp(info, "aes128-gcm") == 0) {
*alg = PSA_ALG_GCM;
key_bits = 128;
key_type = PSA_KEY_TYPE_AES;
} else if (strcmp(info, "aes256-gcm") == 0) {
*alg = PSA_ALG_GCM;
key_bits = 256;
key_type = PSA_KEY_TYPE_AES;
} else if (strcmp(info, "aes128-gcm_8") == 0) {
*alg = PSA_ALG_AEAD_WITH_SHORTENED_TAG(PSA_ALG_GCM, 8);
key_bits = 128;
key_type = PSA_KEY_TYPE_AES;
} else if (strcmp(info, "chachapoly") == 0) {
*alg = PSA_ALG_CHACHA20_POLY1305;
key_bits = 256;
key_type = PSA_KEY_TYPE_CHACHA20;
} else {
puts(usage);
return PSA_ERROR_INVALID_ARGUMENT;
}
/* Prepare key attributes */
psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
psa_set_key_usage_flags(&attributes, PSA_KEY_USAGE_ENCRYPT);
psa_set_key_algorithm(&attributes, *alg);
psa_set_key_type(&attributes, key_type);
psa_set_key_bits(&attributes, key_bits); // optional
/* Import key */
PSA_CHECK(psa_import_key(&attributes, key_bytes, key_bits / 8, key));
exit:
return status;
}
/*
* Print out some information.
*
* All of this information was present in the command line argument, but his
* function demonstrates how each piece can be recovered from (key, alg).
*/
static void aead_info(psa_key_id_t key, psa_algorithm_t alg)
{
psa_key_attributes_t attr = PSA_KEY_ATTRIBUTES_INIT;
(void) psa_get_key_attributes(key, &attr);
psa_key_type_t key_type = psa_get_key_type(&attr);
size_t key_bits = psa_get_key_bits(&attr);
psa_algorithm_t base_alg = PSA_ALG_AEAD_WITH_DEFAULT_LENGTH_TAG(alg);
size_t tag_len = PSA_AEAD_TAG_LENGTH(key_type, key_bits, alg);
const char *type_str = key_type == PSA_KEY_TYPE_AES ? "AES"
: key_type == PSA_KEY_TYPE_CHACHA20 ? "Chacha"
: "???";
const char *base_str = base_alg == PSA_ALG_GCM ? "GCM"
: base_alg == PSA_ALG_CHACHA20_POLY1305 ? "ChachaPoly"
: "???";
printf("%s, %u, %s, %u\n",
type_str, (unsigned) key_bits, base_str, (unsigned) tag_len);
}
/*
* Encrypt a 2-part message.
*/
static int aead_encrypt(psa_key_id_t key, psa_algorithm_t alg,
const unsigned char *iv, size_t iv_len,
const unsigned char *ad, size_t ad_len,
const unsigned char *part1, size_t part1_len,
const unsigned char *part2, size_t part2_len)
{
psa_status_t status;
size_t olen, olen_tag;
unsigned char out[PSA_AEAD_ENCRYPT_OUTPUT_MAX_SIZE(MSG_MAX_SIZE)];
unsigned char *p = out, *end = out + sizeof(out);
unsigned char tag[PSA_AEAD_TAG_MAX_SIZE];
psa_aead_operation_t op = PSA_AEAD_OPERATION_INIT;
PSA_CHECK(psa_aead_encrypt_setup(&op, key, alg));
PSA_CHECK(psa_aead_set_nonce(&op, iv, iv_len));
PSA_CHECK(psa_aead_update_ad(&op, ad, ad_len));
PSA_CHECK(psa_aead_update(&op, part1, part1_len, p, end - p, &olen));
p += olen;
PSA_CHECK(psa_aead_update(&op, part2, part2_len, p, end - p, &olen));
p += olen;
PSA_CHECK(psa_aead_finish(&op, p, end - p, &olen,
tag, sizeof(tag), &olen_tag));
p += olen;
memcpy(p, tag, olen_tag);
p += olen_tag;
olen = p - out;
print_buf("out", out, olen);
exit:
psa_aead_abort(&op); // required on errors, harmless on success
return status;
}
/*
* AEAD demo: set up key/alg, print out info, encrypt messages.
*/
static psa_status_t aead_demo(const char *info)
{
psa_status_t status;
psa_key_id_t key;
psa_algorithm_t alg;
PSA_CHECK(aead_prepare(info, &key, &alg));
aead_info(key, alg);
PSA_CHECK(aead_encrypt(key, alg,
iv1, sizeof(iv1), add_data1, sizeof(add_data1),
msg1_part1, sizeof(msg1_part1),
msg1_part2, sizeof(msg1_part2)));
PSA_CHECK(aead_encrypt(key, alg,
iv2, sizeof(iv2), add_data2, sizeof(add_data2),
msg2_part1, sizeof(msg2_part1),
msg2_part2, sizeof(msg2_part2)));
exit:
psa_destroy_key(key);
return status;
}
/*
* Main function
*/
int main(int argc, char **argv)
{
psa_status_t status = PSA_SUCCESS;
/* Check usage */
if (argc != 2) {
puts(usage);
return EXIT_FAILURE;
}
/* Initialize the PSA crypto library. */
PSA_CHECK(psa_crypto_init());
/* Run the demo */
PSA_CHECK(aead_demo(argv[1]));
/* Deinitialize the PSA crypto library. */
mbedtls_psa_crypto_free();
exit:
return status == PSA_SUCCESS ? EXIT_SUCCESS : EXIT_FAILURE;
}
#endif