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 the test vector from the paper "SipHash: a fast short-input PRF".
19 * https://www.aumasson.jp/siphash/siphash.pdf
20 */
21
22/*
23 * Hard coding the key into an application is very bad.
24 * It is done here solely for educational purposes.
25 */
26static unsigned char key[] = {
27    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
28    0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f
29};
30
31static unsigned char data[] = {
32    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
33    0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e
34};
35
36static const unsigned char expected_output[] = {
37    0xe5, 0x45, 0xbe, 0x49, 0x61, 0xca, 0x29, 0xa1
38};
39
40/*
41 * A property query used for selecting the SIPHASH implementation.
42 */
43static char *propq = NULL;
44
45int main(int argc, char **argv)
46{
47    int rv = EXIT_FAILURE;
48    EVP_MAC *mac = NULL;
49    EVP_MAC_CTX *mctx = NULL;
50    unsigned char out[8];
51    OSSL_PARAM params[4], *p = params;
52    OSSL_LIB_CTX *library_context = NULL;
53    unsigned int digest_len = 8, c_rounds = 2, d_rounds = 4;
54    size_t out_len = 0;
55
56    library_context = OSSL_LIB_CTX_new();
57    if (library_context == NULL) {
58        fprintf(stderr, "OSSL_LIB_CTX_new() returned NULL\n");
59        goto end;
60    }
61
62    /* Fetch the SipHash implementation */
63    mac = EVP_MAC_fetch(library_context, "SIPHASH", propq);
64    if (mac == NULL) {
65        fprintf(stderr, "EVP_MAC_fetch() returned NULL\n");
66        goto end;
67    }
68
69    /* Create a context for the SipHash operation */
70    mctx = EVP_MAC_CTX_new(mac);
71    if (mctx == NULL) {
72        fprintf(stderr, "EVP_MAC_CTX_new() returned NULL\n");
73        goto end;
74    }
75
76    /* SipHash can support either 8 or 16-byte digests. */
77    *p++ = OSSL_PARAM_construct_uint(OSSL_MAC_PARAM_SIZE, &digest_len);
78
79    /*
80     * The number of C-rounds and D-rounds is configurable. Standard SipHash
81     * uses values of 2 and 4 respectively. The following lines are unnecessary
82     * as they set the default, but demonstrate how to change these values.
83     */
84    *p++ = OSSL_PARAM_construct_uint(OSSL_MAC_PARAM_C_ROUNDS, &c_rounds);
85    *p++ = OSSL_PARAM_construct_uint(OSSL_MAC_PARAM_D_ROUNDS, &d_rounds);
86
87    *p = OSSL_PARAM_construct_end();
88
89    /* Initialise the SIPHASH operation */
90    if (!EVP_MAC_init(mctx, key, sizeof(key), params)) {
91        fprintf(stderr, "EVP_MAC_init() failed\n");
92        goto end;
93    }
94
95    /* Make one or more calls to process the data to be authenticated */
96    if (!EVP_MAC_update(mctx, data, sizeof(data))) {
97        fprintf(stderr, "EVP_MAC_update() failed\n");
98        goto end;
99    }
100
101    /* Make one call to the final to get the MAC */
102    if (!EVP_MAC_final(mctx, out, &out_len, sizeof(out))) {
103        fprintf(stderr, "EVP_MAC_final() failed\n");
104        goto end;
105    }
106
107    printf("Generated MAC:\n");
108    BIO_dump_indent_fp(stdout, out, out_len, 2);
109    putchar('\n');
110
111    if (out_len != sizeof(expected_output)) {
112        fprintf(stderr, "Generated MAC has an unexpected length\n");
113        goto end;
114    }
115
116    if (CRYPTO_memcmp(expected_output, out, sizeof(expected_output)) != 0) {
117        fprintf(stderr, "Generated MAC does not match expected value\n");
118        goto end;
119    }
120
121    rv = EXIT_SUCCESS;
122end:
123    EVP_MAC_CTX_free(mctx);
124    EVP_MAC_free(mac);
125    OSSL_LIB_CTX_free(library_context);
126    if (rv != EXIT_SUCCESS)
127        ERR_print_errors_fp(stderr);
128    return rv;
129}
130