1 /*-
2 * Copyright 2022 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
main(void)66 int main(void)
67 {
68 int rv = 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[] = "aes256";
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 rv = EXIT_SUCCESS;
145 end:
146 if (rv != 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 rv;
154 }
155