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116 lines
3.2 KiB
Plaintext
116 lines
3.2 KiB
Plaintext
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=pod
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=head1 NAME
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EVP_KDF-KB - The Key-Based EVP_KDF implementation
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=head1 DESCRIPTION
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The EVP_KDF-KB algorithm implements the Key-Based key derivation function
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(KBKDF). KBKDF derives a key from repeated application of a keyed MAC to an
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input secret (and other optional values).
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=head2 Identity
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"KBKDF" is the name for this implementation; it can be used with the
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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 B<OSSL_KDF_PARAM_PROPERTIES> ("properties") <UTF8 string>
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=item B<OSSL_KDF_PARAM_DIGEST> ("digest") <UTF8 string>
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=item B<OSSL_KDF_PARAM_DIGEST> ("mac") <UTF8 string>
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=item B<OSSL_KDF_PARAM_KEY> ("key") <octet string>
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=item B<OSSL_KDF_PARAM_SALT> ("salt") <octet string>
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=item B<OSSL_KDF_PARAM_INFO> ("info") <octet string>
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=back
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The parameters key, salt, and info correspond to KI, Label, and Context
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(respectively) in SP800-108. As in that document, salt and info are optional
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and may be omitted. Currently, only HMAC is supported for mac.
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=head1 NOTES
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A context for KBKDF can be obtained by calling:
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EVP_KDF *kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL);
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EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
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The output length of an KBKDF is specified via the C<keylen>
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parameter to the L<EVP_KDF_derive(3)> function.
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Note that currently OpenSSL only implements Counter mode with HMAC. Other
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variants may be supported in the future.
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=head1 EXAMPLES
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This example derives 10 bytes using COUNTER-HMAC-SHA256, with KI "secret",
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Label "label", and Context "context".
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EVP_KDF *kdf;
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EVP_KDF_CTX *kctx;
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unsigned char out[10];
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OSSL_PARAM params[6], *p = params;
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kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL);
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kctx = EVP_KDF_CTX_new(kdf);
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EVP_KDF_free(kdf);
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*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
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"SHA256", 0);
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*p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC,
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"HMAC", 0);
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY,
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"secret", strlen("secret"))
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
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"context", strlen("context"));
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*p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
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"label", strlen("label"));
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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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else 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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NIST SP800-108, IETF RFC 8009.
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=head1 SEE ALSO
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L<EVP_KDF(3)>,
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L<EVP_KDF_CTX_new_id(3)>,
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L<EVP_KDF_CTX_free(3)>,
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L<EVP_KDF_ctrl(3)>,
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L<EVP_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 The OpenSSL Project Authors. All Rights Reserved.
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Copyright 2019 Red Hat, Inc.
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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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