demos/mac/cmac-aes256.c

   1 /*-
   2  * Copyright 2022-2023 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 /*
  11  * Example of using EVP_MAC_ methods to calculate
  12  * a CMAC of static buffers
  13  */
  14
  15 #include <string.h>
  16 #include <stdio.h>
  17 #include <openssl/crypto.h>
  18 #include <openssl/core_names.h>
  19 #include <openssl/err.h>
  20 #include <openssl/evp.h>
  21 #include <openssl/cmac.h>
  22 #include <openssl/params.h>
  23
  24 /*
  25  * Hard coding the key into an application is very bad.
  26  * It is done here solely for educational purposes.
  27  */
  28 static unsigned char key[] = {
  29     0x6c, 0xde, 0x14, 0xf5, 0xd5, 0x2a, 0x4a, 0xdf,
  30     0x12, 0x39, 0x1e, 0xbf, 0x36, 0xf9, 0x6a, 0x46,
  31     0x48, 0xd0, 0xb6, 0x51, 0x89, 0xfc, 0x24, 0x85,
  32     0xa8, 0x8d, 0xdf, 0x7e, 0x80, 0x14, 0xc8, 0xce,
  33 };
  34
  35 static const unsigned char data[] =
  36     "To be, or not to be, that is the question,\n"
  37     "Whether tis nobler in the minde to suffer\n"
  38     "The ſlings and arrowes of outragious fortune,\n"
  39     "Or to take Armes again in a sea of troubles,\n"
  40     "And by opposing, end them, to die to sleep;\n"
  41     "No more, and by a sleep, to say we end\n"
  42     "The heart-ache, and the thousand natural shocks\n"
  43     "That flesh is heir to? tis a consumation\n"
  44     "Devoutly to be wished. To die to sleep,\n"
  45     "To sleepe, perchance to dreame, Aye, there's the rub,\n"
  46     "For in that sleep of death what dreams may come\n"
  47     "When we haue shuffled off this mortal coil\n"
  48     "Must give us pause. There's the respect\n"
  49     "That makes calamity of so long life:\n"
  50     "For who would bear the Ships and Scorns of time,\n"
  51     "The oppressor's wrong, the proud man's Contumely,\n"
  52     "The pangs of dispised love, the Law's delay,\n"
  53 ;
  54
  55 /* The known value of the CMAC/AES256 MAC of the above soliloqy */
  56 static const unsigned char expected_output[] = {
  57     0x67, 0x92, 0x32, 0x23, 0x50, 0x3d, 0xc5, 0xba,
  58     0x78, 0xd4, 0x6d, 0x63, 0xf2, 0x2b, 0xe9, 0x56,
  59 };
  60
  61 /*
  62  * A property query used for selecting the MAC implementation.
  63  */
  64 static const char *propq = NULL;
  65
  66 int main(void)
  67 {
  68     int ret = EXIT_FAILURE;
  69     OSSL_LIB_CTX *library_context = NULL;
  70     EVP_MAC *mac = NULL;
  71     EVP_MAC_CTX *mctx = NULL;
  72     unsigned char *out = NULL;
  73     size_t out_len = 0;
  74     OSSL_PARAM params[4], *p = params;
  75     char cipher_name[] = "AES-256-CBC";
  76
  77     library_context = OSSL_LIB_CTX_new();
  78     if (library_context == NULL) {
  79         fprintf(stderr, "OSSL_LIB_CTX_new() returned NULL\n");
  80         goto end;
  81     }
  82
  83     /* Fetch the CMAC implementation */
  84     mac = EVP_MAC_fetch(library_context, "CMAC", propq);
  85     if (mac == NULL) {
  86         fprintf(stderr, "EVP_MAC_fetch() returned NULL\n");
  87         goto end;
  88     }
  89
  90     /* Create a context for the CMAC operation */
  91     mctx = EVP_MAC_CTX_new(mac);
  92     if (mctx == NULL) {
  93         fprintf(stderr, "EVP_MAC_CTX_new() returned NULL\n");
  94         goto end;
  95     }
  96
  97     /* The underlying cipher to be used */
  98     *p++ = OSSL_PARAM_construct_utf8_string(OSSL_MAC_PARAM_CIPHER, cipher_name,
  99                                             sizeof(cipher_name));
 100     *p = OSSL_PARAM_construct_end();
 101
 102     /* Initialise the CMAC operation */
 103     if (!EVP_MAC_init(mctx, key, sizeof(key), params)) {
 104         fprintf(stderr, "EVP_MAC_init() failed\n");
 105         goto end;
 106     }
 107
 108     /* Make one or more calls to process the data to be authenticated */
 109     if (!EVP_MAC_update(mctx, data, sizeof(data))) {
 110         fprintf(stderr, "EVP_MAC_update() failed\n");
 111         goto end;
 112     }
 113
 114     /* Make a call to the final with a NULL buffer to get the length of the MAC */
 115     if (!EVP_MAC_final(mctx, NULL, &out_len, 0)) {
 116         fprintf(stderr, "EVP_MAC_final() failed\n");
 117         goto end;
 118     }
 119     out = OPENSSL_malloc(out_len);
 120     if (out == NULL) {
 121         fprintf(stderr, "malloc failed\n");
 122         goto end;
 123     }
 124     /* Make one call to the final to get the MAC */
 125     if (!EVP_MAC_final(mctx, out, &out_len, out_len)) {
 126         fprintf(stderr, "EVP_MAC_final() failed\n");
 127         goto end;
 128     }
 129
 130     printf("Generated MAC:\n");
 131     BIO_dump_indent_fp(stdout, out, out_len, 2);
 132     putchar('\n');
 133
 134     if (out_len != sizeof(expected_output)) {
 135         fprintf(stderr, "Generated MAC has an unexpected length\n");
 136         goto end;
 137     }
 138
 139     if (CRYPTO_memcmp(expected_output, out, sizeof(expected_output)) != 0) {
 140         fprintf(stderr, "Generated MAC does not match expected value\n");
 141         goto end;
 142     }
 143
 144     ret = EXIT_SUCCESS;
 145 end:
 146     if (ret != EXIT_SUCCESS)
 147         ERR_print_errors_fp(stderr);
 148     /* OpenSSL free functions will ignore NULL arguments */
 149     OPENSSL_free(out);
 150     EVP_MAC_CTX_free(mctx);
 151     EVP_MAC_free(mac);
 152     OSSL_LIB_CTX_free(library_context);
 153     return ret;
 154 }