| 1 | /*
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| 2 | * Copyright 2021 The OpenSSL Project Authors. All Rights Reserved.
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| 3 | *
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| 4 | * Licensed under the Apache License 2.0 (the "License"). You may not use
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| 5 | * this file except in compliance with the License. You can obtain a copy
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| 6 | * in the file LICENSE in the source distribution or at
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| 7 | * https://www.openssl.org/source/license.html
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| 8 | */
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| 9 |
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| 10 | #include <stdio.h>
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| 11 | #include <stdlib.h>
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| 12 | #include <openssl/core_names.h>
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| 13 | #include <openssl/evp.h>
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| 14 | #include <openssl/params.h>
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| 15 | #include <openssl/err.h>
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| 16 |
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| 17 | /*
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| 18 | * Taken from NIST's GCM Test Vectors
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| 19 | * http://csrc.nist.gov/groups/STM/cavp/
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| 20 | */
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| 21 |
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| 22 | /*
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| 23 | * Hard coding the key into an application is very bad.
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| 24 | * It is done here solely for educational purposes.
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| 25 | */
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| 26 | static unsigned char key[] = {
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| 27 | 0x77, 0xbe, 0x63, 0x70, 0x89, 0x71, 0xc4, 0xe2,
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| 28 | 0x40, 0xd1, 0xcb, 0x79, 0xe8, 0xd7, 0x7f, 0xeb
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| 29 | };
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| 30 |
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| 31 | /*
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| 32 | * The initialisation vector (IV) is better not being hard coded too.
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| 33 | * Repeating password/IV pairs compromises the integrity of GMAC.
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| 34 | * The IV is not considered secret information and is safe to store with
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| 35 | * an encrypted password.
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| 36 | */
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| 37 | static unsigned char iv[] = {
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| 38 | 0xe0, 0xe0, 0x0f, 0x19, 0xfe, 0xd7, 0xba,
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| 39 | 0x01, 0x36, 0xa7, 0x97, 0xf3
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| 40 | };
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| 41 |
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| 42 | static unsigned char data[] = {
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| 43 | 0x7a, 0x43, 0xec, 0x1d, 0x9c, 0x0a, 0x5a, 0x78,
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| 44 | 0xa0, 0xb1, 0x65, 0x33, 0xa6, 0x21, 0x3c, 0xab
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| 45 | };
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| 46 |
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| 47 | static const unsigned char expected_output[] = {
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| 48 | 0x20, 0x9f, 0xcc, 0x8d, 0x36, 0x75, 0xed, 0x93,
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| 49 | 0x8e, 0x9c, 0x71, 0x66, 0x70, 0x9d, 0xd9, 0x46
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| 50 | };
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| 51 |
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| 52 | /*
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| 53 | * A property query used for selecting the GMAC implementation and the
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| 54 | * underlying GCM mode cipher.
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| 55 | */
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| 56 | static char *propq = NULL;
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| 57 |
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| 58 | int main(int argc, char **argv)
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| 59 | {
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| 60 | int rv = EXIT_FAILURE;
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| 61 | EVP_MAC *mac = NULL;
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| 62 | EVP_MAC_CTX *mctx = NULL;
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| 63 | unsigned char out[16];
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| 64 | OSSL_PARAM params[4], *p = params;
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| 65 | OSSL_LIB_CTX *library_context = NULL;
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| 66 | size_t out_len = 0;
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| 67 |
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| 68 | library_context = OSSL_LIB_CTX_new();
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| 69 | if (library_context == NULL) {
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| 70 | fprintf(stderr, "OSSL_LIB_CTX_new() returned NULL\n");
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| 71 | goto end;
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| 72 | }
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| 73 |
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| 74 | /* Fetch the GMAC implementation */
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| 75 | mac = EVP_MAC_fetch(library_context, "GMAC", propq);
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| 76 | if (mac == NULL) {
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| 77 | fprintf(stderr, "EVP_MAC_fetch() returned NULL\n");
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| 78 | goto end;
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| 79 | }
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| 80 |
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| 81 | /* Create a context for the GMAC operation */
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| 82 | mctx = EVP_MAC_CTX_new(mac);
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| 83 | if (mctx == NULL) {
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| 84 | fprintf(stderr, "EVP_MAC_CTX_new() returned NULL\n");
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| 85 | goto end;
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| 86 | }
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| 87 |
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| 88 | /* GMAC requries a GCM mode cipher to be specified */
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| 89 | *p++ = OSSL_PARAM_construct_utf8_string(OSSL_MAC_PARAM_CIPHER,
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| 90 | "AES-128-GCM", 0);
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| 91 |
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| 92 | /*
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| 93 | * If a non-default property query is required when fetching the GCM mode
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| 94 | * cipher, it needs to be specified too.
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| 95 | */
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| 96 | if (propq != NULL)
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| 97 | *p++ = OSSL_PARAM_construct_utf8_string(OSSL_MAC_PARAM_PROPERTIES,
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| 98 | propq, 0);
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| 99 |
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| 100 | /* Set the initialisation vector (IV) */
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| 101 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_CIPHER_PARAM_IV,
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| 102 | iv, sizeof(iv));
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| 103 | *p = OSSL_PARAM_construct_end();
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| 104 |
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| 105 | /* Initialise the GMAC operation */
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| 106 | if (!EVP_MAC_init(mctx, key, sizeof(key), params)) {
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| 107 | fprintf(stderr, "EVP_MAC_init() failed\n");
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| 108 | goto end;
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| 109 | }
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| 110 |
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| 111 | /* Make one or more calls to process the data to be authenticated */
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| 112 | if (!EVP_MAC_update(mctx, data, sizeof(data))) {
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| 113 | fprintf(stderr, "EVP_MAC_update() failed\n");
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| 114 | goto end;
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| 115 | }
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| 116 |
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| 117 | /* Make one call to the final to get the MAC */
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| 118 | if (!EVP_MAC_final(mctx, out, &out_len, sizeof(out))) {
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| 119 | fprintf(stderr, "EVP_MAC_final() failed\n");
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| 120 | goto end;
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| 121 | }
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| 122 |
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| 123 | printf("Generated MAC:\n");
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| 124 | BIO_dump_indent_fp(stdout, out, out_len, 2);
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| 125 | putchar('\n');
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| 126 |
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| 127 | if (out_len != sizeof(expected_output)) {
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| 128 | fprintf(stderr, "Generated MAC has an unexpected length\n");
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| 129 | goto end;
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| 130 | }
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| 131 |
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| 132 | if (CRYPTO_memcmp(expected_output, out, sizeof(expected_output)) != 0) {
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| 133 | fprintf(stderr, "Generated MAC does not match expected value\n");
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| 134 | goto end;
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| 135 | }
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| 136 |
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| 137 | rv = EXIT_SUCCESS;
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| 138 | end:
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| 139 | EVP_MAC_CTX_free(mctx);
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| 140 | EVP_MAC_free(mac);
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| 141 | OSSL_LIB_CTX_free(library_context);
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| 142 | if (rv != EXIT_SUCCESS)
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| 143 | ERR_print_errors_fp(stderr);
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| 144 | return rv;
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| 145 | }
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