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     printf( "\n" );
103 }
104 
105 /* Run a PSA function and bail out if it fails.
106  * The symbolic name of the error code can be recovered using:
107  * programs/psa/psa_constant_name status <value> */
108 #define PSA_CHECK( expr )                                       \
109     do                                                          \
110     {                                                           \
111         status = ( expr );                                      \
112         if( status != PSA_SUCCESS )                             \
113         {                                                       \
114             printf( "Error %d at line %d: %s\n",                \
115                     (int) status,                               \
116                     __LINE__,                                   \
117                     #expr );                                    \
118             goto exit;                                          \
119         }                                                       \
120     }                                                           \
121     while( 0 )
122 
123 /*
124  * Prepare encryption material:
125  * - interpret command-line argument
126  * - set up key
127  * - outputs: key and algorithm, which together hold all the information
128  */
aead_prepare(const char * info,psa_key_id_t * key,psa_algorithm_t * alg)129 static psa_status_t aead_prepare( const char *info,
130                                   psa_key_id_t *key,
131                                   psa_algorithm_t *alg )
132 {
133     psa_status_t status;
134 
135     /* Convert arg to alg + key_bits + key_type */
136     size_t key_bits;
137     psa_key_type_t key_type;
138     if( strcmp( info, "aes128-gcm" ) == 0 ) {
139         *alg = PSA_ALG_GCM;
140         key_bits = 128;
141         key_type = PSA_KEY_TYPE_AES;
142     } else if( strcmp( info, "aes256-gcm" ) == 0 ) {
143         *alg = PSA_ALG_GCM;
144         key_bits = 256;
145         key_type = PSA_KEY_TYPE_AES;
146     } else if( strcmp( info, "aes128-gcm_8" ) == 0 ) {
147         *alg = PSA_ALG_AEAD_WITH_SHORTENED_TAG(PSA_ALG_GCM, 8);
148         key_bits = 128;
149         key_type = PSA_KEY_TYPE_AES;
150     } else if( strcmp( info, "chachapoly" ) == 0 ) {
151         *alg = PSA_ALG_CHACHA20_POLY1305;
152         key_bits = 256;
153         key_type = PSA_KEY_TYPE_CHACHA20;
154     } else {
155         puts( usage );
156         return( PSA_ERROR_INVALID_ARGUMENT );
157     }
158 
159     /* Prepare key attributes */
160     psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
161     psa_set_key_usage_flags( &attributes, PSA_KEY_USAGE_ENCRYPT );
162     psa_set_key_algorithm( &attributes, *alg );
163     psa_set_key_type( &attributes, key_type );
164     psa_set_key_bits( &attributes, key_bits ); // optional
165 
166     /* Import key */
167     PSA_CHECK( psa_import_key( &attributes, key_bytes, key_bits / 8, key ) );
168 
169 exit:
170     return( status );
171 }
172 
173 /*
174  * Print out some information.
175  *
176  * All of this information was present in the command line argument, but his
177  * function demonstrates how each piece can be recovered from (key, alg).
178  */
aead_info(psa_key_id_t key,psa_algorithm_t alg)179 static void aead_info( psa_key_id_t key, psa_algorithm_t alg )
180 {
181     psa_key_attributes_t attr = PSA_KEY_ATTRIBUTES_INIT;
182     (void) psa_get_key_attributes( key, &attr );
183     psa_key_type_t key_type = psa_get_key_type( &attr );
184     size_t key_bits = psa_get_key_bits( &attr );
185     psa_algorithm_t base_alg = PSA_ALG_AEAD_WITH_DEFAULT_LENGTH_TAG( alg );
186     size_t tag_len = PSA_AEAD_TAG_LENGTH( key_type, key_bits, alg );
187 
188     const char *type_str = key_type == PSA_KEY_TYPE_AES ? "AES"
189                          : key_type == PSA_KEY_TYPE_CHACHA20 ? "Chacha"
190                          : "???";
191     const char *base_str = base_alg == PSA_ALG_GCM ? "GCM"
192                          : base_alg == PSA_ALG_CHACHA20_POLY1305 ? "ChachaPoly"
193                          : "???";
194 
195     printf( "%s, %u, %s, %u\n",
196             type_str, (unsigned) key_bits, base_str, (unsigned) tag_len );
197 }
198 
199 /*
200  * Encrypt a 2-part message.
201  */
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)202 static int aead_encrypt( psa_key_id_t key, psa_algorithm_t alg,
203         const unsigned char *iv, size_t iv_len,
204         const unsigned char *ad, size_t ad_len,
205         const unsigned char *part1, size_t part1_len,
206         const unsigned char *part2, size_t part2_len )
207 {
208     psa_status_t status;
209     size_t olen, olen_tag;
210     unsigned char out[PSA_AEAD_ENCRYPT_OUTPUT_MAX_SIZE(MSG_MAX_SIZE)];
211     unsigned char *p = out, *end = out + sizeof( out );
212     unsigned char tag[PSA_AEAD_TAG_MAX_SIZE];
213 
214     psa_aead_operation_t op = PSA_AEAD_OPERATION_INIT;
215     PSA_CHECK( psa_aead_encrypt_setup( &op, key, alg ) );
216 
217     PSA_CHECK( psa_aead_set_nonce( &op, iv, iv_len ) );
218     PSA_CHECK( psa_aead_update_ad( &op, ad, ad_len ) );
219     PSA_CHECK( psa_aead_update( &op, part1, part1_len, p, end - p, &olen ) );
220     p += olen;
221     PSA_CHECK( psa_aead_update( &op, part2, part2_len, p, end - p, &olen ) );
222     p += olen;
223     PSA_CHECK( psa_aead_finish( &op, p, end - p, &olen,
224                                tag, sizeof( tag ), &olen_tag ) );
225     p += olen;
226     memcpy( p, tag, olen_tag );
227     p += olen_tag;
228 
229     olen = p - out;
230     print_buf( "out", out, olen );
231 
232 exit:
233     psa_aead_abort( &op ); // required on errors, harmless on success
234     return( status );
235 }
236 
237 /*
238  * AEAD demo: set up key/alg, print out info, encrypt messages.
239  */
aead_demo(const char * info)240 static psa_status_t aead_demo( const char *info )
241 {
242     psa_status_t status;
243 
244     psa_key_id_t key;
245     psa_algorithm_t alg;
246 
247     PSA_CHECK( aead_prepare( info, &key, &alg ) );
248 
249     aead_info( key, alg );
250 
251     PSA_CHECK( aead_encrypt( key, alg,
252                        iv1, sizeof( iv1 ), add_data1, sizeof( add_data1 ),
253                        msg1_part1, sizeof( msg1_part1 ),
254                        msg1_part2, sizeof( msg1_part2 ) ) );
255     PSA_CHECK( aead_encrypt( key, alg,
256                        iv2, sizeof( iv2 ), add_data2, sizeof( add_data2 ),
257                        msg2_part1, sizeof( msg2_part1 ),
258                        msg2_part2, sizeof( msg2_part2 ) ) );
259 
260 exit:
261     psa_destroy_key( key );
262 
263     return( status );
264 }
265 
266 /*
267  * Main function
268  */
main(int argc,char ** argv)269 int main( int argc, char **argv )
270 {
271     psa_status_t status = PSA_SUCCESS;
272 
273     /* Check usage */
274     if( argc != 2 )
275     {
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