| 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_KDF-X942-ASN1 - The X9.42-2003 asn1 EVP_KDF implementation
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| 6 |
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| 7 | =head1 DESCRIPTION
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| 8 |
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| 9 | The EVP_KDF-X942-ASN1 algorithm implements the key derivation function
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| 10 | X942KDF-ASN1. It is used by DH KeyAgreement, to derive a key using input such as
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| 11 | a shared secret key and other info. The other info is DER encoded data that
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| 12 | contains a 32 bit counter as well as optional fields for "partyu-info",
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| 13 | "partyv-info", "supp-pubinfo" and "supp-privinfo".
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| 14 | This kdf is used by Cryptographic Message Syntax (CMS).
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| 15 |
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| 16 | =head2 Identity
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| 17 |
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| 18 | "X942KDF-ASN1" or "X942KDF" is the name for this implementation; it
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| 19 | can be used with the EVP_KDF_fetch() function.
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| 20 |
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| 21 | =head2 Supported parameters
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| 22 |
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| 23 | The supported parameters are:
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| 24 |
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| 25 | =over 4
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| 26 |
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| 27 | =item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
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| 28 |
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| 29 | =item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
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| 30 |
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| 31 | These parameters work as described in L<EVP_KDF(3)/PARAMETERS>.
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| 32 |
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| 33 | =item "key" (B<OSSL_KDF_PARAM_KEY>) <octet string>
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| 34 |
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| 35 | The shared secret used for key derivation. This parameter sets the secret.
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| 36 |
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| 37 | =item "acvp-info" (B<OSSL_KDF_PARAM_X942_ACVPINFO>) <octet string>
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| 38 |
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| 39 | This value should not be used in production and should only be used for ACVP
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| 40 | testing. It is an optional octet string containing a combined DER encoded blob
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| 41 | of any of the optional fields related to "partyu-info", "partyv-info",
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| 42 | "supp-pubinfo" and "supp-privinfo". If it is specified then none of these other
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| 43 | fields should be used.
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| 44 |
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| 45 | =item "partyu-info" (B<OSSL_KDF_PARAM_X942_PARTYUINFO>) <octet string>
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| 46 |
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| 47 | An optional octet string containing public info contributed by the initiator.
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| 48 |
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| 49 | =item "ukm" (B<OSSL_KDF_PARAM_UKM>) <octet string>
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| 50 |
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| 51 | An alias for "partyu-info".
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| 52 | In CMS this is the user keying material.
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| 53 |
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| 54 | =item "partyv-info" (B<OSSL_KDF_PARAM_X942_PARTYVINFO>) <octet string>
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| 55 |
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| 56 | An optional octet string containing public info contributed by the responder.
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| 57 |
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| 58 | =item "supp-pubinfo" (B<OSSL_KDF_PARAM_X942_SUPP_PUBINFO>) <octet string>
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| 59 |
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| 60 | An optional octet string containing some additional, mutually-known public
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| 61 | information. Setting this value also sets "use-keybits" to 0.
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| 62 |
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| 63 | =item "use-keybits" (B<OSSL_KDF_PARAM_X942_SUPP_PRIVINFO>) <integer>
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| 64 |
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| 65 | The default value of 1 will use the KEK key length (in bits) as the
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| 66 | "supp-pubinfo". A value of 0 disables setting the "supp-pubinfo".
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| 67 |
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| 68 | =item "supp-privinfo" (B<OSSL_KDF_PARAM_X942_SUPP_PRIVINFO>) <octet string>
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| 69 |
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| 70 | An optional octet string containing some additional, mutually-known private
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| 71 | information.
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| 72 |
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| 73 | =item "cekalg" (B<OSSL_KDF_PARAM_CEK_ALG>) <UTF8 string>
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| 74 |
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| 75 | This parameter sets the CEK wrapping algorithm name.
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| 76 | Valid values are "AES-128-WRAP", "AES-192-WRAP", "AES-256-WRAP" and "DES3-WRAP".
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| 77 |
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| 78 | =back
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| 79 |
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| 80 | =head1 NOTES
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| 81 |
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| 82 | A context for X942KDF can be obtained by calling:
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| 83 |
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| 84 | EVP_KDF *kdf = EVP_KDF_fetch(NULL, "X942KDF", NULL);
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| 85 | EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
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| 86 |
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| 87 | The output length of an X942KDF is specified via the I<keylen>
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| 88 | parameter to the L<EVP_KDF_derive(3)> function.
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| 89 |
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| 90 | =head1 EXAMPLES
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| 91 |
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| 92 | This example derives 24 bytes, with the secret key "secret" and random user
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| 93 | keying material:
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| 94 |
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| 95 | EVP_KDF_CTX *kctx;
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| 96 | EVP_KDF_CTX *kctx;
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| 97 | unsigned char out[192/8];
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| 98 | unsignred char ukm[64];
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| 99 | OSSL_PARAM params[5], *p = params;
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| 100 |
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| 101 | if (RAND_bytes(ukm, sizeof(ukm)) <= 0)
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| 102 | error("RAND_bytes");
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| 103 |
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| 104 | kdf = EVP_KDF_fetch(NULL, "X942KDF", NULL);
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| 105 | if (kctx == NULL)
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| 106 | error("EVP_KDF_fetch");
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| 107 | kctx = EVP_KDF_CTX_new(kdf);
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| 108 | EVP_KDF_free(kdf);
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| 109 | if (kctx == NULL)
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| 110 | error("EVP_KDF_CTX_new");
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| 111 |
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| 112 | *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST, "SHA256", 0);
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| 113 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SECRET,
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| 114 | "secret", (size_t)6);
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| 115 | *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_UKM, ukm, sizeof(ukm));
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| 116 | *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_CEK_ALG, "AES-256-WRAP, 0);
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| 117 | *p = OSSL_PARAM_construct_end();
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| 118 | if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0)
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| 119 | error("EVP_KDF_derive");
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| 120 |
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| 121 | EVP_KDF_CTX_free(kctx);
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| 122 |
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| 123 | =head1 CONFORMING TO
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| 124 |
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| 125 | ANS1 X9.42-2003
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| 126 | RFC 2631
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| 127 |
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| 128 | =head1 SEE ALSO
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| 129 |
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| 130 | L<EVP_KDF(3)>,
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| 131 | L<EVP_KDF_CTX_new(3)>,
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| 132 | L<EVP_KDF_CTX_free(3)>,
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| 133 | L<EVP_KDF_CTX_set_params(3)>,
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| 134 | L<EVP_KDF_CTX_get_kdf_size(3)>,
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| 135 | L<EVP_KDF_derive(3)>,
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| 136 | L<EVP_KDF(3)/PARAMETERS>
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| 137 |
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| 138 | =head1 HISTORY
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| 139 |
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| 140 | This functionality was added to OpenSSL 3.0.
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| 141 |
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| 142 | =head1 COPYRIGHT
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| 143 |
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| 144 | Copyright 2019-2021 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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