cipher_aead_demo.c (8500B)
1 /** 2 * Cipher 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 psa/aead_demo.c, which does the same 8 * operations with the PSA Crypto API. The goal is that comparing the two 9 * 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 psa/aead_demo.c illustrate this by doing the 22 * same sequence of multi-part AEAD computation with both APIs; looking at the 23 * two side by side should make the differences and similarities clear. 24 */ 25 26 /* 27 * Copyright The Mbed TLS Contributors 28 * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later 29 */ 30 31 /* First include Mbed TLS headers to get the Mbed TLS configuration and 32 * platform definitions that we'll use in this program. Also include 33 * standard C headers for functions we'll use here. */ 34 #include "mbedtls/build_info.h" 35 36 #include "mbedtls/cipher.h" 37 38 #include <stdlib.h> 39 #include <stdio.h> 40 #include <string.h> 41 42 /* If the build options we need are not enabled, compile a placeholder. */ 43 #if !defined(MBEDTLS_CIPHER_C) || \ 44 !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_GCM_C) || \ 45 !defined(MBEDTLS_CHACHAPOLY_C) 46 int main(void) 47 { 48 printf("MBEDTLS_MD_C and/or " 49 "MBEDTLS_AES_C and/or MBEDTLS_GCM_C and/or " 50 "MBEDTLS_CHACHAPOLY_C not defined\r\n"); 51 return 0; 52 } 53 #else 54 55 /* The real program starts here. */ 56 57 const char usage[] = 58 "Usage: cipher_aead_demo [aes128-gcm|aes256-gcm|aes128-gcm_8|chachapoly]"; 59 60 /* Dummy data for encryption: IV/nonce, additional data, 2-part message */ 61 const unsigned char iv1[12] = { 0x00 }; 62 const unsigned char add_data1[] = { 0x01, 0x02 }; 63 const unsigned char msg1_part1[] = { 0x03, 0x04 }; 64 const unsigned char msg1_part2[] = { 0x05, 0x06, 0x07 }; 65 66 /* Dummy data (2nd message) */ 67 const unsigned char iv2[12] = { 0x10 }; 68 const unsigned char add_data2[] = { 0x11, 0x12 }; 69 const unsigned char msg2_part1[] = { 0x13, 0x14 }; 70 const unsigned char msg2_part2[] = { 0x15, 0x16, 0x17 }; 71 72 /* Maximum total size of the messages */ 73 #define MSG1_SIZE (sizeof(msg1_part1) + sizeof(msg1_part2)) 74 #define MSG2_SIZE (sizeof(msg2_part1) + sizeof(msg2_part2)) 75 #define MSG_MAX_SIZE (MSG1_SIZE > MSG2_SIZE ? MSG1_SIZE : MSG2_SIZE) 76 77 /* Dummy key material - never do this in production! 78 * 32-byte is enough to all the key size supported by this program. */ 79 const unsigned char key_bytes[32] = { 0x2a }; 80 81 /* Print the contents of a buffer in hex */ 82 static void print_buf(const char *title, unsigned char *buf, size_t len) 83 { 84 printf("%s:", title); 85 for (size_t i = 0; i < len; i++) { 86 printf(" %02x", buf[i]); 87 } 88 printf("\n"); 89 } 90 91 /* Run an Mbed TLS function and bail out if it fails. 92 * A string description of the error code can be recovered with: 93 * programs/util/strerror <value> */ 94 #define CHK(expr) \ 95 do \ 96 { \ 97 ret = (expr); \ 98 if (ret != 0) \ 99 { \ 100 printf("Error %d at line %d: %s\n", \ 101 ret, \ 102 __LINE__, \ 103 #expr); \ 104 goto exit; \ 105 } \ 106 } while (0) 107 108 /* 109 * Prepare encryption material: 110 * - interpret command-line argument 111 * - set up key 112 * - outputs: context and tag length, which together hold all the information 113 */ 114 static int aead_prepare(const char *info, 115 mbedtls_cipher_context_t *ctx, 116 size_t *tag_len) 117 { 118 int ret; 119 120 /* Convert arg to type + tag_len */ 121 mbedtls_cipher_type_t type; 122 if (strcmp(info, "aes128-gcm") == 0) { 123 type = MBEDTLS_CIPHER_AES_128_GCM; 124 *tag_len = 16; 125 } else if (strcmp(info, "aes256-gcm") == 0) { 126 type = MBEDTLS_CIPHER_AES_256_GCM; 127 *tag_len = 16; 128 } else if (strcmp(info, "aes128-gcm_8") == 0) { 129 type = MBEDTLS_CIPHER_AES_128_GCM; 130 *tag_len = 8; 131 } else if (strcmp(info, "chachapoly") == 0) { 132 type = MBEDTLS_CIPHER_CHACHA20_POLY1305; 133 *tag_len = 16; 134 } else { 135 puts(usage); 136 return MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA; 137 } 138 139 /* Prepare context for the given type */ 140 CHK(mbedtls_cipher_setup(ctx, 141 mbedtls_cipher_info_from_type(type))); 142 143 /* Import key */ 144 int key_len = mbedtls_cipher_get_key_bitlen(ctx); 145 CHK(mbedtls_cipher_setkey(ctx, key_bytes, key_len, MBEDTLS_ENCRYPT)); 146 147 exit: 148 return ret; 149 } 150 151 /* 152 * Print out some information. 153 * 154 * All of this information was present in the command line argument, but his 155 * function demonstrates how each piece can be recovered from (ctx, tag_len). 156 */ 157 static void aead_info(const mbedtls_cipher_context_t *ctx, size_t tag_len) 158 { 159 mbedtls_cipher_type_t type = mbedtls_cipher_get_type(ctx); 160 const mbedtls_cipher_info_t *info = mbedtls_cipher_info_from_type(type); 161 const char *ciph = mbedtls_cipher_info_get_name(info); 162 int key_bits = mbedtls_cipher_get_key_bitlen(ctx); 163 mbedtls_cipher_mode_t mode = mbedtls_cipher_get_cipher_mode(ctx); 164 165 const char *mode_str = mode == MBEDTLS_MODE_GCM ? "GCM" 166 : mode == MBEDTLS_MODE_CHACHAPOLY ? "ChachaPoly" 167 : "???"; 168 169 printf("%s, %d, %s, %u\n", 170 ciph, key_bits, mode_str, (unsigned) tag_len); 171 } 172 173 /* 174 * Encrypt a 2-part message. 175 */ 176 static int aead_encrypt(mbedtls_cipher_context_t *ctx, size_t tag_len, 177 const unsigned char *iv, size_t iv_len, 178 const unsigned char *ad, size_t ad_len, 179 const unsigned char *part1, size_t part1_len, 180 const unsigned char *part2, size_t part2_len) 181 { 182 int ret; 183 size_t olen; 184 #define MAX_TAG_LENGTH 16 185 unsigned char out[MSG_MAX_SIZE + MAX_TAG_LENGTH]; 186 unsigned char *p = out; 187 188 CHK(mbedtls_cipher_set_iv(ctx, iv, iv_len)); 189 CHK(mbedtls_cipher_reset(ctx)); 190 CHK(mbedtls_cipher_update_ad(ctx, ad, ad_len)); 191 CHK(mbedtls_cipher_update(ctx, part1, part1_len, p, &olen)); 192 p += olen; 193 CHK(mbedtls_cipher_update(ctx, part2, part2_len, p, &olen)); 194 p += olen; 195 CHK(mbedtls_cipher_finish(ctx, p, &olen)); 196 p += olen; 197 CHK(mbedtls_cipher_write_tag(ctx, p, tag_len)); 198 p += tag_len; 199 200 olen = p - out; 201 print_buf("out", out, olen); 202 203 exit: 204 return ret; 205 } 206 207 /* 208 * AEAD demo: set up key/alg, print out info, encrypt messages. 209 */ 210 static int aead_demo(const char *info) 211 { 212 int ret = 0; 213 214 mbedtls_cipher_context_t ctx; 215 size_t tag_len; 216 217 mbedtls_cipher_init(&ctx); 218 219 CHK(aead_prepare(info, &ctx, &tag_len)); 220 221 aead_info(&ctx, tag_len); 222 223 CHK(aead_encrypt(&ctx, tag_len, 224 iv1, sizeof(iv1), add_data1, sizeof(add_data1), 225 msg1_part1, sizeof(msg1_part1), 226 msg1_part2, sizeof(msg1_part2))); 227 CHK(aead_encrypt(&ctx, tag_len, 228 iv2, sizeof(iv2), add_data2, sizeof(add_data2), 229 msg2_part1, sizeof(msg2_part1), 230 msg2_part2, sizeof(msg2_part2))); 231 232 exit: 233 mbedtls_cipher_free(&ctx); 234 235 return ret; 236 } 237 238 239 /* 240 * Main function 241 */ 242 int main(int argc, char **argv) 243 { 244 /* Check usage */ 245 if (argc != 2) { 246 puts(usage); 247 return 1; 248 } 249 250 int ret; 251 252 /* Run the demo */ 253 CHK(aead_demo(argv[1])); 254 255 exit: 256 return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE; 257 } 258 259 #endif