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3dbf824380
There was recently an instance where a user was confused by the deprecation warnings in the docs. They believed the warning applied to the immediately preceding function declarations, when it fact it applied to the following function declarations. https://mta.openssl.org/pipermail/openssl-users/2021-December/014665.html We clarify the wording to make it clear that the warning applies to the following functions. Reviewed-by: Paul Dale <pauli@openssl.org> Reviewed-by: Tomas Mraz <tomas@openssl.org> Reviewed-by: Richard Levitte <levitte@openssl.org> (Merged from https://github.com/openssl/openssl/pull/17180)
83 lines
2.7 KiB
Plaintext
83 lines
2.7 KiB
Plaintext
=pod
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=head1 NAME
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DH_generate_key, DH_compute_key, DH_compute_key_padded - perform
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Diffie-Hellman key exchange
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=head1 SYNOPSIS
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#include <openssl/dh.h>
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The following functions have been deprecated since OpenSSL 3.0, and can be
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hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
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see L<openssl_user_macros(7)>:
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int DH_generate_key(DH *dh);
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int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);
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int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh);
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=head1 DESCRIPTION
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All of the functions described on this page are deprecated.
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Applications should instead use L<EVP_PKEY_derive_init(3)>
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and L<EVP_PKEY_derive(3)>.
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DH_generate_key() performs the first step of a Diffie-Hellman key
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exchange by generating private and public DH values. By calling
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DH_compute_key() or DH_compute_key_padded(), these are combined with
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the other party's public value to compute the shared key.
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DH_generate_key() expects B<dh> to contain the shared parameters
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B<dh-E<gt>p> and B<dh-E<gt>g>. It generates a random private DH value
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unless B<dh-E<gt>priv_key> is already set, and computes the
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corresponding public value B<dh-E<gt>pub_key>, which can then be
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published.
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DH_compute_key() computes the shared secret from the private DH value
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in B<dh> and the other party's public value in B<pub_key> and stores
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it in B<key>. B<key> must point to B<DH_size(dh)> bytes of memory.
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The padding style is RFC 5246 (8.1.2) that strips leading zero bytes.
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It is not constant time due to the leading zero bytes being stripped.
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The return value should be considered public.
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DH_compute_key_padded() is similar but stores a fixed number of bytes.
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The padding style is NIST SP 800-56A (C.1) that retains leading zero bytes.
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It is constant time due to the leading zero bytes being retained.
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The return value should be considered public.
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=head1 RETURN VALUES
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DH_generate_key() returns 1 on success, 0 otherwise.
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DH_compute_key() returns the size of the shared secret on success, -1
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on error.
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DH_compute_key_padded() returns B<DH_size(dh)> on success, -1 on error.
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The error codes can be obtained by L<ERR_get_error(3)>.
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=head1 SEE ALSO
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L<EVP_PKEY_derive(3)>,
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L<DH_new(3)>, L<ERR_get_error(3)>, L<RAND_bytes(3)>, L<DH_size(3)>
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=head1 HISTORY
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DH_compute_key_padded() was added in OpenSSL 1.0.2.
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All of these functions were deprecated in OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2000-2021 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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