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 HMAC 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/hmac.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 */
28static unsigned char key[] = {
29    0x25, 0xfd, 0x12, 0x99, 0xdf, 0xad, 0x1a, 0x03,
30    0x0a, 0x81, 0x3c, 0x2d, 0xcc, 0x05, 0xd1, 0x5c,
31    0x17, 0x7a, 0x36, 0x73, 0x17, 0xef, 0x41, 0x75,
32    0x71, 0x18, 0xe0, 0x1a, 0xda, 0x99, 0xc3, 0x61,
33    0x38, 0xb5, 0xb1, 0xe0, 0x82, 0x2c, 0x70, 0xa4,
34    0xc0, 0x8e, 0x5e, 0xf9, 0x93, 0x9f, 0xcf, 0xf7,
35    0x32, 0x4d, 0x0c, 0xbd, 0x31, 0x12, 0x0f, 0x9a,
36    0x15, 0xee, 0x82, 0xdb, 0x8d, 0x29, 0x54, 0x14,
37};
38
39static const unsigned char data[] =
40    "To be, or not to be, that is the question,\n"
41    "Whether tis nobler in the minde to suffer\n"
42    "The ��lings and arrowes of outragious fortune,\n"
43    "Or to take Armes again in a sea of troubles,\n"
44    "And by opposing, end them, to die to sleep;\n"
45    "No more, and by a sleep, to say we end\n"
46    "The heart-ache, and the thousand natural shocks\n"
47    "That flesh is heir to? tis a consumation\n"
48    "Devoutly to be wished. To die to sleep,\n"
49    "To sleepe, perchance to dreame, Aye, there's the rub,\n"
50    "For in that sleep of death what dreams may come\n"
51    "When we haue shuffled off this mortal coil\n"
52    "Must give us pause. There's the respect\n"
53    "That makes calamity of so long life:\n"
54    "For who would bear the Ships and Scorns of time,\n"
55    "The oppressor's wrong, the proud man's Contumely,\n"
56    "The pangs of dispised love, the Law's delay,\n"
57;
58
59/* The known value of the HMAC/SHA3-512 MAC of the above soliloqy */
60static const unsigned char expected_output[] = {
61    0x3b, 0x77, 0x5f, 0xf1, 0x4f, 0x9e, 0xb9, 0x23,
62    0x8f, 0xdc, 0xa0, 0x68, 0x15, 0x7b, 0x8a, 0xf1,
63    0x96, 0x23, 0xaa, 0x3c, 0x1f, 0xe9, 0xdc, 0x89,
64    0x11, 0x7d, 0x58, 0x07, 0xe7, 0x96, 0x17, 0xe3,
65    0x44, 0x8b, 0x03, 0x37, 0x91, 0xc0, 0x6e, 0x06,
66    0x7c, 0x54, 0xe4, 0xa4, 0xcc, 0xd5, 0x16, 0xbb,
67    0x5e, 0x4d, 0x64, 0x7d, 0x88, 0x23, 0xc9, 0xb7,
68    0x25, 0xda, 0xbe, 0x4b, 0xe4, 0xd5, 0x34, 0x30,
69};
70
71/*
72 * A property query used for selecting the MAC implementation.
73 */
74static const char *propq = NULL;
75
76int main(void)
77{
78    int rv = EXIT_FAILURE;
79    OSSL_LIB_CTX *library_context = NULL;
80    EVP_MAC *mac = NULL;
81    EVP_MAC_CTX *mctx = NULL;
82    EVP_MD_CTX *digest_context = NULL;
83    unsigned char *out = NULL;
84    size_t out_len = 0;
85    OSSL_PARAM params[4], *p = params;
86    char digest_name[] = "SHA3-512";
87
88    library_context = OSSL_LIB_CTX_new();
89    if (library_context == NULL) {
90        fprintf(stderr, "OSSL_LIB_CTX_new() returned NULL\n");
91        goto end;
92    }
93
94    /* Fetch the HMAC implementation */
95    mac = EVP_MAC_fetch(library_context, "HMAC", propq);
96    if (mac == NULL) {
97        fprintf(stderr, "EVP_MAC_fetch() returned NULL\n");
98        goto end;
99    }
100
101    /* Create a context for the HMAC operation */
102    mctx = EVP_MAC_CTX_new(mac);
103    if (mctx == NULL) {
104        fprintf(stderr, "EVP_MAC_CTX_new() returned NULL\n");
105        goto end;
106    }
107
108    /* The underlying digest to be used */
109    *p++ = OSSL_PARAM_construct_utf8_string(OSSL_MAC_PARAM_DIGEST, digest_name,
110                                            sizeof(digest_name));
111    *p = OSSL_PARAM_construct_end();
112
113    /* Initialise the HMAC operation */
114    if (!EVP_MAC_init(mctx, key, sizeof(key), params)) {
115        fprintf(stderr, "EVP_MAC_init() failed\n");
116        goto end;
117    }
118
119    /* Make one or more calls to process the data to be authenticated */
120    if (!EVP_MAC_update(mctx, data, sizeof(data))) {
121        fprintf(stderr, "EVP_MAC_update() failed\n");
122        goto end;
123    }
124
125    /* Make a call to the final with a NULL buffer to get the length of the MAC */
126    if (!EVP_MAC_final(mctx, NULL, &out_len, 0)) {
127        fprintf(stderr, "EVP_MAC_final() failed\n");
128        goto end;
129    }
130    out = OPENSSL_malloc(out_len);
131    if (out == NULL) {
132        fprintf(stderr, "malloc failed\n");
133        goto end;
134    }
135    /* Make one call to the final to get the MAC */
136    if (!EVP_MAC_final(mctx, out, &out_len, out_len)) {
137        fprintf(stderr, "EVP_MAC_final() failed\n");
138        goto end;
139    }
140
141    printf("Generated MAC:\n");
142    BIO_dump_indent_fp(stdout, out, out_len, 2);
143    putchar('\n');
144
145    if (out_len != sizeof(expected_output)) {
146        fprintf(stderr, "Generated MAC has an unexpected length\n");
147        goto end;
148    }
149
150    if (CRYPTO_memcmp(expected_output, out, sizeof(expected_output)) != 0) {
151        fprintf(stderr, "Generated MAC does not match expected value\n");
152        goto end;
153    }
154
155    rv = EXIT_SUCCESS;
156end:
157    if (rv != EXIT_SUCCESS)
158        ERR_print_errors_fp(stderr);
159    /* OpenSSL free functions will ignore NULL arguments */
160    OPENSSL_free(out);
161    EVP_MD_CTX_free(digest_context);
162    EVP_MAC_CTX_free(mctx);
163    EVP_MAC_free(mac);
164    OSSL_LIB_CTX_free(library_context);
165    return rv;
166}
167