1=pod 2 3=head1 NAME 4 5EVP_MAC-KMAC, EVP_MAC-KMAC128, EVP_MAC-KMAC256 6- The KMAC EVP_MAC implementations 7 8=head1 DESCRIPTION 9 10Support for computing KMAC MACs through the B<EVP_MAC> API. 11 12=head2 Identity 13 14These implementations are identified with one of these names and 15properties, to be used with EVP_MAC_fetch(): 16 17=over 4 18 19=item "KMAC-128", "provider=default" or "provider=fips" 20 21=item "KMAC-256", "provider=default" or "provider=fips" 22 23=back 24 25=head2 Supported parameters 26 27The general description of these parameters can be found in 28L<EVP_MAC(3)/PARAMETERS>. 29 30All these parameters can be set with EVP_MAC_CTX_set_params(). 31Furthermore, the "size" parameter can be retrieved with 32EVP_MAC_CTX_get_params(), or with EVP_MAC_CTX_get_mac_size(). 33The length of the "size" parameter should not exceed that of a B<size_t>. 34Likewise, the "block-size" parameter can be retrieved with 35EVP_MAC_CTX_get_params(), or with EVP_MAC_CTX_get_block_size(). 36 37 38=over 4 39 40=item "key" (B<OSSL_MAC_PARAM_KEY>) <octet string> 41 42Sets the MAC key. 43Setting this parameter is identical to passing a I<key> to L<EVP_MAC_init(3)>. 44 45=item "custom" (B<OSSL_MAC_PARAM_CUSTOM>) <octet string> 46 47Sets the custom value. 48It is an optional value of at most 256 bytes, and is empty by default. 49 50=item "size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer> 51 52Sets the MAC size. 53By default, it is 16 for C<KMAC-128> and 32 for C<KMAC-256>. 54 55=item "block-size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer> 56 57Gets the MAC block size. 58By default, it is 168 for C<KMAC-128> and 136 for C<KMAC-256>. 59 60=item "xof" (B<OSSL_MAC_PARAM_XOF>) <integer> 61 62The "xof" parameter value is expected to be 1 or 0. Use 1 to enable XOF mode. 63The default value is 0. 64 65=back 66 67The "custom" parameter must be set as part of or before the EVP_MAC_init() call. 68The "xof" and "size" parameters can be set at any time before EVP_MAC_final(). 69The "key" parameter is set as part of the EVP_MAC_init() call, but can be 70set before it instead. 71 72=head1 EXAMPLES 73 74 #include <openssl/evp.h> 75 #include <openssl/params.h> 76 77 static int do_kmac(const unsigned char *in, size_t in_len, 78 const unsigned char *key, size_t key_len, 79 const unsigned char *custom, size_t custom_len, 80 int xof_enabled, unsigned char *out, int out_len) 81 { 82 EVP_MAC_CTX *ctx = NULL; 83 EVP_MAC *mac = NULL; 84 OSSL_PARAM params[4], *p; 85 int ret = 0; 86 size_t l = 0; 87 88 mac = EVP_MAC_fetch(NULL, "KMAC-128", NULL); 89 if (mac == NULL) 90 goto err; 91 ctx = EVP_MAC_CTX_new(mac); 92 /* The mac can be freed after it is used by EVP_MAC_CTX_new */ 93 EVP_MAC_free(mac); 94 if (ctx == NULL) 95 goto err; 96 97 /* 98 * Setup parameters required before calling EVP_MAC_init() 99 * The parameters OSSL_MAC_PARAM_XOF and OSSL_MAC_PARAM_SIZE may also be 100 * used at this point. 101 */ 102 p = params; 103 *p++ = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_KEY, 104 (void *)key, key_len); 105 if (custom != NULL && custom_len != 0) 106 *p++ = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_CUSTOM, 107 (void *)custom, custom_len); 108 *p = OSSL_PARAM_construct_end(); 109 if (!EVP_MAC_CTX_set_params(ctx, params)) 110 goto err; 111 112 if (!EVP_MAC_init(ctx)) 113 goto err; 114 115 /* 116 * Note: the following optional parameters can be set any time 117 * before EVP_MAC_final(). 118 */ 119 p = params; 120 *p++ = OSSL_PARAM_construct_int(OSSL_MAC_PARAM_XOF, &xof_enabled); 121 *p++ = OSSL_PARAM_construct_int(OSSL_MAC_PARAM_SIZE, &out_len); 122 *p = OSSL_PARAM_construct_end(); 123 if (!EVP_MAC_CTX_set_params(ctx, params)) 124 goto err; 125 126 /* The update may be called multiple times here for streamed input */ 127 if (!EVP_MAC_update(ctx, in, in_len)) 128 goto err; 129 if (!EVP_MAC_final(ctx, out, &l, out_len)) 130 goto err; 131 ret = 1; 132 err: 133 EVP_MAC_CTX_free(ctx); 134 return ret; 135 } 136 137=head1 SEE ALSO 138 139L<EVP_MAC_CTX_get_params(3)>, L<EVP_MAC_CTX_set_params(3)>, 140L<EVP_MAC(3)/PARAMETERS>, L<OSSL_PARAM(3)> 141 142=head1 COPYRIGHT 143 144Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved. 145 146Licensed under the Apache License 2.0 (the "License"). You may not use 147this file except in compliance with the License. You can obtain a copy 148in the file LICENSE in the source distribution or at 149L<https://www.openssl.org/source/license.html>. 150 151=cut 152
