8bbeaaa4fc
X963 KDF is used for CMS ec keyagree Recipient Info. The X963 KDF that is used by CMS EC Key Agreement has been moved into a EVP_KDF object. This KDF is almost identical to the the SSKDF hash variant, so it has been implemented inside the SSKDF code with its own method table. Reviewed-by: Matt Caswell <matt@openssl.org> Reviewed-by: Paul Dale <paul.dale@oracle.com> (Merged from https://github.com/openssl/openssl/pull/8902)
136 lines
3.2 KiB
Text
136 lines
3.2 KiB
Text
=pod
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=head1 NAME
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EVP_KDF_X963 - The X9.63-2001 EVP_KDF implementation
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=head1 DESCRIPTION
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The EVP_KDF_X963 algorithm implements the key derivation function (X963KDF).
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X963KDF is used by Cryptographic Message Syntax (CMS) for EC KeyAgreement, to
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derive a key using input such as a shared secret key and shared info.
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=head2 Numeric identity
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B<EVP_KDF_X963> is the numeric identity for this implementation; it
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can be used with the EVP_KDF_CTX_new_id() function.
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=head2 Supported controls
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The supported controls are:
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=over 4
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=item B<EVP_KDF_CTRL_SET_MD>
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This control works as described in L<EVP_KDF_CTX(3)/CONTROLS>.
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=item B<EVP_KDF_CTRL_SET_KEY>
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This control expects two arguments: C<unsigned char *secret>, C<size_t secretlen>
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The shared secret used for key derivation. This control sets the secret.
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EVP_KDF_ctrl_str() takes two type strings for this control:
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=over 4
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=item "secret"
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The value string is used as is.
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=item "hexsecret"
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The value string is expected to be a hexadecimal number, which will be
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decoded before being passed on as the control value.
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=back
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=item B<EVP_KDF_CTRL_SET_SHARED_INFO>
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This control expects two arguments: C<unsigned char *info>, C<size_t infolen>
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An optional value for shared info. This control sets the shared info.
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EVP_KDF_ctrl_str() takes two type strings for this control:
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=over 4
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=item "info"
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The value string is used as is.
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=item "hexinfo"
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The value string is expected to be a hexadecimal number, which will be
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decoded before being passed on as the control value.
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=back
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=back
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=head1 NOTES
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X963KDF is very similar to the SSKDF that uses a digest as the auxilary function,
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X963KDF appends the counter to the secret, whereas SSKDF prepends the counter.
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A context for X963KDF can be obtained by calling:
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EVP_KDF_CTX *kctx = EVP_KDF_CTX_new_id(EVP_KDF_X963);
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The output length of an X963KDF is specified via the C<keylen>
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parameter to the L<EVP_KDF_derive(3)> function.
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=head1 EXAMPLE
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This example derives 10 bytes, with the secret key "secret" and sharedinfo
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value "label":
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EVP_KDF_CTX *kctx;
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unsigned char out[10];
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kctx = EVP_KDF_CTX_new_id(EVP_KDF_X963);
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if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_MD, EVP_sha256()) <= 0) {
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error("EVP_KDF_CTRL_SET_MD");
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}
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if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_KEY, "secret", (size_t)6) <= 0) {
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error("EVP_KDF_CTRL_SET_KEY");
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}
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if (EVP_KDF_ctrl(kctx, EVP_KDF_CTRL_SET_SHARED_INFO, "label", (size_t)5) <= 0) {
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error("EVP_KDF_CTRL_SET_SHARED_INFO");
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}
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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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}
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EVP_KDF_CTX_free(kctx);
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=head1 CONFORMING TO
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"SEC 1: Elliptic Curve Cryptography"
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=head1 SEE ALSO
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L<EVP_KDF_CTX>,
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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_CTX(3)/CONTROLS>
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=head1 HISTORY
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This functionality was added to OpenSSL 3.0.0.
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=head1 COPYRIGHT
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Copyright 2019 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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