1 /*
2 * Copyright 2021-2022 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 #include <stdio.h>
11 #include <stdlib.h>
12 #include <openssl/core_names.h>
13 #include <openssl/evp.h>
14 #include <openssl/params.h>
15 #include <openssl/err.h>
16
17 /*
18 * Taken from NIST's GCM Test Vectors
19 * http://csrc.nist.gov/groups/STM/cavp/
20 */
21
22 /*
23 * Hard coding the key into an application is very bad.
24 * It is done here solely for educational purposes.
25 */
26 static unsigned char key[] = {
27 0x77, 0xbe, 0x63, 0x70, 0x89, 0x71, 0xc4, 0xe2,
28 0x40, 0xd1, 0xcb, 0x79, 0xe8, 0xd7, 0x7f, 0xeb
29 };
30
31 /*
32 * The initialisation vector (IV) is better not being hard coded too.
33 * Repeating password/IV pairs compromises the integrity of GMAC.
34 * The IV is not considered secret information and is safe to store with
35 * an encrypted password.
36 */
37 static unsigned char iv[] = {
38 0xe0, 0xe0, 0x0f, 0x19, 0xfe, 0xd7, 0xba,
39 0x01, 0x36, 0xa7, 0x97, 0xf3
40 };
41
42 static unsigned char data[] = {
43 0x7a, 0x43, 0xec, 0x1d, 0x9c, 0x0a, 0x5a, 0x78,
44 0xa0, 0xb1, 0x65, 0x33, 0xa6, 0x21, 0x3c, 0xab
45 };
46
47 static const unsigned char expected_output[] = {
48 0x20, 0x9f, 0xcc, 0x8d, 0x36, 0x75, 0xed, 0x93,
49 0x8e, 0x9c, 0x71, 0x66, 0x70, 0x9d, 0xd9, 0x46
50 };
51
52 /*
53 * A property query used for selecting the GMAC implementation and the
54 * underlying GCM mode cipher.
55 */
56 static char *propq = NULL;
57
main(int argc,char ** argv)58 int main(int argc, char **argv)
59 {
60 int rv = EXIT_FAILURE;
61 EVP_MAC *mac = NULL;
62 EVP_MAC_CTX *mctx = NULL;
63 unsigned char out[16];
64 OSSL_PARAM params[4], *p = params;
65 OSSL_LIB_CTX *library_context = NULL;
66 size_t out_len = 0;
67
68 library_context = OSSL_LIB_CTX_new();
69 if (library_context == NULL) {
70 fprintf(stderr, "OSSL_LIB_CTX_new() returned NULL\n");
71 goto end;
72 }
73
74 /* Fetch the GMAC implementation */
75 mac = EVP_MAC_fetch(library_context, "GMAC", propq);
76 if (mac == NULL) {
77 fprintf(stderr, "EVP_MAC_fetch() returned NULL\n");
78 goto end;
79 }
80
81 /* Create a context for the GMAC operation */
82 mctx = EVP_MAC_CTX_new(mac);
83 if (mctx == NULL) {
84 fprintf(stderr, "EVP_MAC_CTX_new() returned NULL\n");
85 goto end;
86 }
87
88 /* GMAC requires a GCM mode cipher to be specified */
89 *p++ = OSSL_PARAM_construct_utf8_string(OSSL_MAC_PARAM_CIPHER,
90 "AES-128-GCM", 0);
91
92 /*
93 * If a non-default property query is required when fetching the GCM mode
94 * cipher, it needs to be specified too.
95 */
96 if (propq != NULL)
97 *p++ = OSSL_PARAM_construct_utf8_string(OSSL_MAC_PARAM_PROPERTIES,
98 propq, 0);
99
100 /* Set the initialisation vector (IV) */
101 *p++ = OSSL_PARAM_construct_octet_string(OSSL_CIPHER_PARAM_IV,
102 iv, sizeof(iv));
103 *p = OSSL_PARAM_construct_end();
104
105 /* Initialise the GMAC operation */
106 if (!EVP_MAC_init(mctx, key, sizeof(key), params)) {
107 fprintf(stderr, "EVP_MAC_init() failed\n");
108 goto end;
109 }
110
111 /* Make one or more calls to process the data to be authenticated */
112 if (!EVP_MAC_update(mctx, data, sizeof(data))) {
113 fprintf(stderr, "EVP_MAC_update() failed\n");
114 goto end;
115 }
116
117 /* Make one call to the final to get the MAC */
118 if (!EVP_MAC_final(mctx, out, &out_len, sizeof(out))) {
119 fprintf(stderr, "EVP_MAC_final() failed\n");
120 goto end;
121 }
122
123 printf("Generated MAC:\n");
124 BIO_dump_indent_fp(stdout, out, out_len, 2);
125 putchar('\n');
126
127 if (out_len != sizeof(expected_output)) {
128 fprintf(stderr, "Generated MAC has an unexpected length\n");
129 goto end;
130 }
131
132 if (CRYPTO_memcmp(expected_output, out, sizeof(expected_output)) != 0) {
133 fprintf(stderr, "Generated MAC does not match expected value\n");
134 goto end;
135 }
136
137 rv = EXIT_SUCCESS;
138 end:
139 EVP_MAC_CTX_free(mctx);
140 EVP_MAC_free(mac);
141 OSSL_LIB_CTX_free(library_context);
142 if (rv != EXIT_SUCCESS)
143 ERR_print_errors_fp(stderr);
144 return rv;
145 }
146
