1/**
2 * PSA API multi-part AEAD demonstration.
3 *
4 * This program AEAD-encrypts a message, using the algorithm and key size
5 * specified on the command line, using the multi-part API.
6 *
7 * It comes with a companion program cipher/cipher_aead_demo.c, which does the
8 * same operations with the legacy Cipher API. The goal is that comparing the
9 * two programs will help people migrating to the PSA Crypto API.
10 *
11 * When used with multi-part AEAD operations, the `mbedtls_cipher_context`
12 * serves a triple purpose (1) hold the key, (2) store the algorithm when no
13 * operation is active, and (3) save progress information for the current
14 * operation. With PSA those roles are held by disinct objects: (1) a
15 * psa_key_id_t to hold the key, a (2) psa_algorithm_t to represent the
16 * algorithm, and (3) a psa_operation_t for multi-part progress.
17 *
18 * On the other hand, with PSA, the algorithms encodes the desired tag length;
19 * with Cipher the desired tag length needs to be tracked separately.
20 *
21 * This program and its companion cipher/cipher_aead_demo.c illustrate this by
22 * doing the same sequence of multi-part AEAD computation with both APIs;
23 * looking at the two side by side should make the differences and
24 * similarities clear.
25 */
26
27/*
28 *  Copyright The Mbed TLS Contributors
29 *  SPDX-License-Identifier: Apache-2.0
30 *
31 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
32 *  not use this file except in compliance with the License.
33 *  You may obtain a copy of the License at
34 *
35 *  http://www.apache.org/licenses/LICENSE-2.0
36 *
37 *  Unless required by applicable law or agreed to in writing, software
38 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
39 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
40 *  See the License for the specific language governing permissions and
41 *  limitations under the License.
42 */
43
44/* First include Mbed TLS headers to get the Mbed TLS configuration and
45 * platform definitions that we'll use in this program. Also include
46 * standard C headers for functions we'll use here. */
47#include "mbedtls/build_info.h"
48
49#include "psa/crypto.h"
50
51#include <stdlib.h>
52#include <stdio.h>
53#include <string.h>
54
55/* If the build options we need are not enabled, compile a placeholder. */
56#if !defined(MBEDTLS_PSA_CRYPTO_C) || \
57    !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_GCM_C) || \
58    !defined(MBEDTLS_CHACHAPOLY_C) || \
59    defined(MBEDTLS_PSA_CRYPTO_KEY_ID_ENCODES_OWNER)
60int main(void)
61{
62    printf("MBEDTLS_PSA_CRYPTO_C and/or "
63           "MBEDTLS_AES_C and/or MBEDTLS_GCM_C and/or "
64           "MBEDTLS_CHACHAPOLY_C not defined, and/or "
65           "MBEDTLS_PSA_CRYPTO_KEY_ID_ENCODES_OWNER defined\r\n");
66    return 0;
67}
68#else
69
70/* The real program starts here. */
71
72const char usage[] =
73    "Usage: aead_demo [aes128-gcm|aes256-gcm|aes128-gcm_8|chachapoly]";
74
75/* Dummy data for encryption: IV/nonce, additional data, 2-part message */
76const unsigned char iv1[12] = { 0x00 };
77const unsigned char add_data1[] = { 0x01, 0x02 };
78const unsigned char msg1_part1[] = { 0x03, 0x04 };
79const unsigned char msg1_part2[] = { 0x05, 0x06, 0x07 };
80
81/* Dummy data (2nd message) */
82const unsigned char iv2[12] = { 0x10 };
83const unsigned char add_data2[] = { 0x11, 0x12 };
84const unsigned char msg2_part1[] = { 0x13, 0x14 };
85const unsigned char msg2_part2[] = { 0x15, 0x16, 0x17 };
86
87/* Maximum total size of the messages */
88#define MSG1_SIZE (sizeof(msg1_part1) + sizeof(msg1_part2))
89#define MSG2_SIZE (sizeof(msg2_part1) + sizeof(msg2_part2))
90#define MSG_MAX_SIZE (MSG1_SIZE > MSG2_SIZE ? MSG1_SIZE : MSG2_SIZE)
91
92/* Dummy key material - never do this in production!
93 * 32-byte is enough to all the key size supported by this program. */
94const unsigned char key_bytes[32] = { 0x2a };
95
96/* Print the contents of a buffer in hex */
97void print_buf(const char *title, uint8_t *buf, size_t len)
98{
99    printf("%s:", title);
100    for (size_t i = 0; i < len; i++) {
101        printf(" %02x", buf[i]);
102    }
103    printf("\n");
104}
105
106/* Run a PSA function and bail out if it fails.
107 * The symbolic name of the error code can be recovered using:
108 * programs/psa/psa_constant_name status <value> */
109#define PSA_CHECK(expr)                                       \
110    do                                                          \
111    {                                                           \
112        status = (expr);                                      \
113        if (status != PSA_SUCCESS)                             \
114        {                                                       \
115            printf("Error %d at line %d: %s\n",                \
116                   (int) status,                               \
117                   __LINE__,                                   \
118                   #expr);                                    \
119            goto exit;                                          \
120        }                                                       \
121    }                                                           \
122    while (0)
123
124/*
125 * Prepare encryption material:
126 * - interpret command-line argument
127 * - set up key
128 * - outputs: key and algorithm, which together hold all the information
129 */
130static psa_status_t aead_prepare(const char *info,
131                                 psa_key_id_t *key,
132                                 psa_algorithm_t *alg)
133{
134    psa_status_t status;
135
136    /* Convert arg to alg + key_bits + key_type */
137    size_t key_bits;
138    psa_key_type_t key_type;
139    if (strcmp(info, "aes128-gcm") == 0) {
140        *alg = PSA_ALG_GCM;
141        key_bits = 128;
142        key_type = PSA_KEY_TYPE_AES;
143    } else if (strcmp(info, "aes256-gcm") == 0) {
144        *alg = PSA_ALG_GCM;
145        key_bits = 256;
146        key_type = PSA_KEY_TYPE_AES;
147    } else if (strcmp(info, "aes128-gcm_8") == 0) {
148        *alg = PSA_ALG_AEAD_WITH_SHORTENED_TAG(PSA_ALG_GCM, 8);
149        key_bits = 128;
150        key_type = PSA_KEY_TYPE_AES;
151    } else if (strcmp(info, "chachapoly") == 0) {
152        *alg = PSA_ALG_CHACHA20_POLY1305;
153        key_bits = 256;
154        key_type = PSA_KEY_TYPE_CHACHA20;
155    } else {
156        puts(usage);
157        return PSA_ERROR_INVALID_ARGUMENT;
158    }
159
160    /* Prepare key attributes */
161    psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
162    psa_set_key_usage_flags(&attributes, PSA_KEY_USAGE_ENCRYPT);
163    psa_set_key_algorithm(&attributes, *alg);
164    psa_set_key_type(&attributes, key_type);
165    psa_set_key_bits(&attributes, key_bits);   // optional
166
167    /* Import key */
168    PSA_CHECK(psa_import_key(&attributes, key_bytes, key_bits / 8, key));
169
170exit:
171    return status;
172}
173
174/*
175 * Print out some information.
176 *
177 * All of this information was present in the command line argument, but his
178 * function demonstrates how each piece can be recovered from (key, alg).
179 */
180static void aead_info(psa_key_id_t key, psa_algorithm_t alg)
181{
182    psa_key_attributes_t attr = PSA_KEY_ATTRIBUTES_INIT;
183    (void) psa_get_key_attributes(key, &attr);
184    psa_key_type_t key_type = psa_get_key_type(&attr);
185    size_t key_bits = psa_get_key_bits(&attr);
186    psa_algorithm_t base_alg = PSA_ALG_AEAD_WITH_DEFAULT_LENGTH_TAG(alg);
187    size_t tag_len = PSA_AEAD_TAG_LENGTH(key_type, key_bits, alg);
188
189    const char *type_str = key_type == PSA_KEY_TYPE_AES ? "AES"
190                         : key_type == PSA_KEY_TYPE_CHACHA20 ? "Chacha"
191                         : "???";
192    const char *base_str = base_alg == PSA_ALG_GCM ? "GCM"
193                         : base_alg == PSA_ALG_CHACHA20_POLY1305 ? "ChachaPoly"
194                         : "???";
195
196    printf("%s, %u, %s, %u\n",
197           type_str, (unsigned) key_bits, base_str, (unsigned) tag_len);
198}
199
200/*
201 * Encrypt a 2-part message.
202 */
203static int aead_encrypt(psa_key_id_t key, psa_algorithm_t alg,
204                        const unsigned char *iv, size_t iv_len,
205                        const unsigned char *ad, size_t ad_len,
206                        const unsigned char *part1, size_t part1_len,
207                        const unsigned char *part2, size_t part2_len)
208{
209    psa_status_t status;
210    size_t olen, olen_tag;
211    unsigned char out[PSA_AEAD_ENCRYPT_OUTPUT_MAX_SIZE(MSG_MAX_SIZE)];
212    unsigned char *p = out, *end = out + sizeof(out);
213    unsigned char tag[PSA_AEAD_TAG_MAX_SIZE];
214
215    psa_aead_operation_t op = PSA_AEAD_OPERATION_INIT;
216    PSA_CHECK(psa_aead_encrypt_setup(&op, key, alg));
217
218    PSA_CHECK(psa_aead_set_nonce(&op, iv, iv_len));
219    PSA_CHECK(psa_aead_update_ad(&op, ad, ad_len));
220    PSA_CHECK(psa_aead_update(&op, part1, part1_len, p, end - p, &olen));
221    p += olen;
222    PSA_CHECK(psa_aead_update(&op, part2, part2_len, p, end - p, &olen));
223    p += olen;
224    PSA_CHECK(psa_aead_finish(&op, p, end - p, &olen,
225                              tag, sizeof(tag), &olen_tag));
226    p += olen;
227    memcpy(p, tag, olen_tag);
228    p += olen_tag;
229
230    olen = p - out;
231    print_buf("out", out, olen);
232
233exit:
234    psa_aead_abort(&op);   // required on errors, harmless on success
235    return status;
236}
237
238/*
239 * AEAD demo: set up key/alg, print out info, encrypt messages.
240 */
241static psa_status_t aead_demo(const char *info)
242{
243    psa_status_t status;
244
245    psa_key_id_t key;
246    psa_algorithm_t alg;
247
248    PSA_CHECK(aead_prepare(info, &key, &alg));
249
250    aead_info(key, alg);
251
252    PSA_CHECK(aead_encrypt(key, alg,
253                           iv1, sizeof(iv1), add_data1, sizeof(add_data1),
254                           msg1_part1, sizeof(msg1_part1),
255                           msg1_part2, sizeof(msg1_part2)));
256    PSA_CHECK(aead_encrypt(key, alg,
257                           iv2, sizeof(iv2), add_data2, sizeof(add_data2),
258                           msg2_part1, sizeof(msg2_part1),
259                           msg2_part2, sizeof(msg2_part2)));
260
261exit:
262    psa_destroy_key(key);
263
264    return status;
265}
266
267/*
268 * Main function
269 */
270int main(int argc, char **argv)
271{
272    psa_status_t status = PSA_SUCCESS;
273
274    /* Check usage */
275    if (argc != 2) {
276        puts(usage);
277        return EXIT_FAILURE;
278    }
279
280    /* Initialize the PSA crypto library. */
281    PSA_CHECK(psa_crypto_init());
282
283    /* Run the demo */
284    PSA_CHECK(aead_demo(argv[1]));
285
286    /* Deinitialize the PSA crypto library. */
287    mbedtls_psa_crypto_free();
288
289exit:
290    return status == PSA_SUCCESS ? EXIT_SUCCESS : EXIT_FAILURE;
291}
292
293#endif
294