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147 lines
4.2 KiB
Plaintext
147 lines
4.2 KiB
Plaintext
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=pod
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=head1 NAME
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EVP_KDF-X942-ASN1 - The X9.42-2003 asn1 EVP_KDF implementation
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=head1 DESCRIPTION
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The EVP_KDF-X942-ASN1 algorithm implements the key derivation function
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X942KDF-ASN1. It is used by DH KeyAgreement, to derive a key using input such as
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a shared secret key and other info. The other info is DER encoded data that
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contains a 32 bit counter as well as optional fields for "partyu-info",
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"partyv-info", "supp-pubinfo" and "supp-privinfo".
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This kdf is used by Cryptographic Message Syntax (CMS).
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=head2 Identity
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"X942KDF-ASN1" or "X942KDF" is the name for this implementation; it
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can be used with the EVP_KDF_fetch() function.
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=head2 Supported parameters
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The supported parameters are:
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=over 4
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=item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
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=item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
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These parameters work as described in L<EVP_KDF(3)/PARAMETERS>.
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=item "key" (B<OSSL_KDF_PARAM_KEY>) <octet string>
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The shared secret used for key derivation. This parameter sets the secret.
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=item "partyu-info" (B<OSSL_KDF_PARAM_X942_PARTYUINFO>) <octet string>
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An optional octet string containing public info contributed by the initiator.
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=item "ukm" (B<OSSL_KDF_PARAM_UKM>) <octet string>
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An alias for "partyu-info".
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In CMS this is the user keying material.
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=item "partyv-info" (B<OSSL_KDF_PARAM_X942_PARTYVINFO>) <octet string>
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An optional octet string containing public info contributed by the responder.
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=item "supp-pubinfo" (B<OSSL_KDF_PARAM_X942_SUPP_PUBINFO>) <octet string>
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An optional octet string containing some additional, mutually-known public
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information. Setting this value also sets "use-keybits" to 0.
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=item "use-keybits" (B<OSSL_KDF_PARAM_X942_SUPP_PRIVINFO>) <integer>
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The default value of 1 will use the KEK key length (in bits) as the
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"supp-pubinfo". A value of 0 disables setting the "supp-pubinfo".
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=item "supp-privinfo" (B<OSSL_KDF_PARAM_X942_SUPP_PRIVINFO>) <octet string>
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An optional octet string containing some additional, mutually-known private
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information.
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=item "cekalg" (B<OSSL_KDF_PARAM_CEK_ALG>) <UTF8 string>
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This parameter sets the CEK wrapping algorithm name.
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Valid values are "AES-128-WRAP", "AES-192-WRAP", "AES-256-WRAP" and "DES3-WRAP".
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=back
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=head1 NOTES
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A context for X942KDF can be obtained by calling:
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EVP_KDF *kdf = EVP_KDF_fetch(NULL, "X942KDF", NULL);
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EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
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The output length of an X942KDF is specified via the I<keylen>
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parameter to the L<EVP_KDF_derive(3)> function.
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=head1 EXAMPLES
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This example derives 24 bytes, with the secret key "secret" and random user
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keying material:
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EVP_KDF_CTX *kctx;
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EVP_KDF_CTX *kctx;
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unsigned char out[192/8];
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unsignred char ukm[64];
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OSSL_PARAM params[5], *p = params;
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if (RAND_bytes(ukm, sizeof(ukm)) <= 0)
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error("RAND_bytes");
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kdf = EVP_KDF_fetch(NULL, "X942KDF", NULL);
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if (kctx == NULL)
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error("EVP_KDF_fetch");
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kctx = EVP_KDF_CTX_new(kdf);
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EVP_KDF_free(kdf);
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if (kctx == NULL)
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error("EVP_KDF_CTX_new");
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*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST, "SHA256", 0);
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SECRET,
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"secret", (size_t)6);
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_UKM, ukm, sizeof(ukm));
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*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_CEK_ALG, "AES-256-WRAP, 0);
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*p = OSSL_PARAM_construct_end();
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if (EVP_KDF_CTX_set_params(kctx, params) <= 0)
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error("EVP_KDF_CTX_set_params");
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if (EVP_KDF_derive(kctx, out, sizeof(out)) <= 0)
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error("EVP_KDF_derive");
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EVP_KDF_CTX_free(kctx);
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=head1 CONFORMING TO
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ANS1 X9.42-2003
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RFC 2631
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=head1 SEE ALSO
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L<EVP_KDF(3)>,
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L<EVP_KDF_CTX_new(3)>,
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L<EVP_KDF_CTX_free(3)>,
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L<EVP_KDF_CTX_set_params(3)>,
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L<EVP_KDF_CTX_get_kdf_size(3)>,
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L<EVP_KDF_derive(3)>,
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L<EVP_KDF(3)/PARAMETERS>
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=head1 HISTORY
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This functionality was added to OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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