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)
main(void)60 int 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 
72 const 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 */
76 const unsigned char iv1[12] = { 0x00 };
77 const unsigned char add_data1[] = { 0x01, 0x02 };
78 const unsigned char msg1_part1[] = { 0x03, 0x04 };
79 const unsigned char msg1_part2[] = { 0x05, 0x06, 0x07 };
80 
81 /* Dummy data (2nd message) */
82 const unsigned char iv2[12] = { 0x10 };
83 const unsigned char add_data2[] = { 0x11, 0x12 };
84 const unsigned char msg2_part1[] = { 0x13, 0x14 };
85 const 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. */
94 const unsigned char key_bytes[32] = { 0x2a };
95 
96 /* Print the contents of a buffer in hex */
print_buf(const char * title,uint8_t * buf,size_t len)97 void 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  */
aead_prepare(const char * info,psa_key_id_t * key,psa_algorithm_t * alg)130 static 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 
170 exit:
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  */
aead_info(psa_key_id_t key,psa_algorithm_t alg)180 static 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  */
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)203 static 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 
233 exit:
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  */
aead_demo(const char * info)241 static 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 
261 exit:
262     psa_destroy_key(key);
263 
264     return status;
265 }
266 
267 /*
268  * Main function
269  */
main(int argc,char ** argv)270 int 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 
289 exit:
290     return status == PSA_SUCCESS ? EXIT_SUCCESS : EXIT_FAILURE;
291 }
292 
293 #endif
294