| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | EVP_MAC-KMAC, EVP_MAC-KMAC128, EVP_MAC-KMAC256
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| 6 | - The KMAC EVP_MAC implementations
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| 7 |
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| 8 | =head1 DESCRIPTION
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| 9 |
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| 10 | Support for computing KMAC MACs through the B<EVP_MAC> API.
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| 11 |
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| 12 | =head2 Identity
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| 13 |
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| 14 | These implementations are identified with one of these names and
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| 15 | properties, to be used with EVP_MAC_fetch():
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| 16 |
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| 17 | =over 4
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| 18 |
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| 19 | =item "KMAC-128", "provider=default" or "provider=fips"
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| 20 |
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| 21 | =item "KMAC-256", "provider=default" or "provider=fips"
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| 22 |
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| 23 | =back
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| 24 |
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| 25 | =head2 Supported parameters
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| 26 |
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| 27 | The general description of these parameters can be found in
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| 28 | L<EVP_MAC(3)/PARAMETERS>.
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| 29 |
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| 30 | All these parameters can be set with EVP_MAC_CTX_set_params().
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| 31 | Furthermore, the "size" parameter can be retrieved with
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| 32 | EVP_MAC_CTX_get_params(), or with EVP_MAC_CTX_get_mac_size().
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| 33 | The length of the "size" parameter should not exceed that of a B<size_t>.
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| 34 | Likewise, the "block-size" parameter can be retrieved with
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| 35 | EVP_MAC_CTX_get_params(), or with EVP_MAC_CTX_get_block_size().
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| 36 |
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| 37 |
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| 38 | =over 4
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| 39 |
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| 40 | =item "key" (B<OSSL_MAC_PARAM_KEY>) <octet string>
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| 41 |
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| 42 | Sets the MAC key.
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| 43 | Setting this parameter is identical to passing a I<key> to L<EVP_MAC_init(3)>.
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| 44 |
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| 45 | =item "custom" (B<OSSL_MAC_PARAM_CUSTOM>) <octet string>
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| 46 |
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| 47 | Sets the custom value.
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| 48 | It is an optional value of at most 256 bytes, and is empty by default.
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| 49 |
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| 50 | =item "size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer>
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| 51 |
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| 52 | Sets the MAC size.
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| 53 | By default, it is 16 for C<KMAC-128> and 32 for C<KMAC-256>.
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| 54 |
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| 55 | =item "block-size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer>
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| 56 |
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| 57 | Gets the MAC block size.
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| 58 | By default, it is 168 for C<KMAC-128> and 136 for C<KMAC-256>.
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| 59 |
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| 60 | =item "xof" (B<OSSL_MAC_PARAM_XOF>) <integer>
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| 61 |
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| 62 | The "xof" parameter value is expected to be 1 or 0. Use 1 to enable XOF mode.
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| 63 | The default value is 0.
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| 64 |
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| 65 | =back
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| 66 |
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| 67 | The "custom" parameter must be set as part of or before the EVP_MAC_init() call.
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| 68 | The "xof" and "size" parameters can be set at any time before EVP_MAC_final().
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| 69 | The "key" parameter is set as part of the EVP_MAC_init() call, but can be
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| 70 | set before it instead.
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| 71 |
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| 72 | =head1 EXAMPLES
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| 73 |
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| 74 | #include <openssl/evp.h>
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| 75 | #include <openssl/params.h>
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| 76 |
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| 77 | static int do_kmac(const unsigned char *in, size_t in_len,
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| 78 | const unsigned char *key, size_t key_len,
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| 79 | const unsigned char *custom, size_t custom_len,
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| 80 | int xof_enabled, unsigned char *out, int out_len)
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| 81 | {
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| 82 | EVP_MAC_CTX *ctx = NULL;
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| 83 | EVP_MAC *mac = NULL;
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| 84 | OSSL_PARAM params[4], *p;
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| 85 | int ret = 0;
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| 86 | size_t l = 0;
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| 87 |
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| 88 | mac = EVP_MAC_fetch(NULL, "KMAC-128", NULL);
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| 89 | if (mac == NULL)
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| 90 | goto err;
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| 91 | ctx = EVP_MAC_CTX_new(mac);
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| 92 | /* The mac can be freed after it is used by EVP_MAC_CTX_new */
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| 93 | EVP_MAC_free(mac);
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| 94 | if (ctx == NULL)
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| 95 | goto err;
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| 96 |
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| 97 | /*
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| 98 | * Setup parameters required before calling EVP_MAC_init()
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| 99 | * The parameters OSSL_MAC_PARAM_XOF and OSSL_MAC_PARAM_SIZE may also be
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| 100 | * used at this point.
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| 101 | */
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| 102 | p = params;
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| 103 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_KEY,
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| 104 | (void *)key, key_len);
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| 105 | if (custom != NULL && custom_len != 0)
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| 106 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_CUSTOM,
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| 107 | (void *)custom, custom_len);
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| 108 | *p = OSSL_PARAM_construct_end();
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| 109 | if (!EVP_MAC_CTX_set_params(ctx, params))
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| 110 | goto err;
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| 111 |
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| 112 | if (!EVP_MAC_init(ctx))
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| 113 | goto err;
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| 114 |
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| 115 | /*
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| 116 | * Note: the following optional parameters can be set any time
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| 117 | * before EVP_MAC_final().
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| 118 | */
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| 119 | p = params;
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| 120 | *p++ = OSSL_PARAM_construct_int(OSSL_MAC_PARAM_XOF, &xof_enabled);
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| 121 | *p++ = OSSL_PARAM_construct_int(OSSL_MAC_PARAM_SIZE, &out_len);
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| 122 | *p = OSSL_PARAM_construct_end();
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| 123 | if (!EVP_MAC_CTX_set_params(ctx, params))
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| 124 | goto err;
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| 125 |
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| 126 | /* The update may be called multiple times here for streamed input */
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| 127 | if (!EVP_MAC_update(ctx, in, in_len))
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| 128 | goto err;
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| 129 | if (!EVP_MAC_final(ctx, out, &l, out_len))
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| 130 | goto err;
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| 131 | ret = 1;
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| 132 | err:
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| 133 | EVP_MAC_CTX_free(ctx);
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| 134 | return ret;
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| 135 | }
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| 136 |
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| 137 | =head1 SEE ALSO
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| 138 |
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| 139 | L<EVP_MAC_CTX_get_params(3)>, L<EVP_MAC_CTX_set_params(3)>,
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| 140 | L<EVP_MAC(3)/PARAMETERS>, L<OSSL_PARAM(3)>
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| 141 |
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| 142 | =head1 COPYRIGHT
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| 143 |
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| 144 | Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved.
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| 145 |
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| 146 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 147 | this file except in compliance with the License. You can obtain a copy
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| 148 | in the file LICENSE in the source distribution or at
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| 149 | L<https://www.openssl.org/source/license.html>.
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| 150 |
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| 151 | =cut
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