mirror of https://github.com/openssl/openssl
142 lines
4.9 KiB
Plaintext
142 lines
4.9 KiB
Plaintext
=pod
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=head1 NAME
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OPENSSL_NO_DEPRECATED_3_2, OSSL_DEPRECATEDIN_3_2,
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OPENSSL_NO_DEPRECATED_3_0, OSSL_DEPRECATEDIN_3_0,
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OPENSSL_NO_DEPRECATED_1_1_1, OSSL_DEPRECATEDIN_1_1_1,
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OPENSSL_NO_DEPRECATED_1_1_0, OSSL_DEPRECATEDIN_1_1_0,
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OPENSSL_NO_DEPRECATED_1_0_2, OSSL_DEPRECATEDIN_1_0_2,
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OPENSSL_NO_DEPRECATED_1_0_1, OSSL_DEPRECATEDIN_1_0_1,
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OPENSSL_NO_DEPRECATED_1_0_0, OSSL_DEPRECATEDIN_1_0_0,
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OPENSSL_NO_DEPRECATED_0_9_8, OSSL_DEPRECATEDIN_0_9_8,
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deprecation - How to do deprecation
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=head1 DESCRIPTION
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Deprecation of a symbol is adding an attribute to the declaration of that
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symbol (function, type, variable, but we currently only do that for
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functions in our public header files, F<< <openssl/*.h> >>).
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Removal of a symbol is not the same thing as deprecation, as it actually
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explicitly removes the symbol from public view.
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OpenSSL configuration supports deprecation as well as simulating removal of
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symbols from public view (with the configuration option C<no-deprecated>, or
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if the user chooses to do so, with L<OPENSSL_NO_DEPRECATED(7)>), and also
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supports doing this in terms of a specified OpenSSL version (with the
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configuration option C<--api>, or if the user chooses to do so, with
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L<OPENSSL_API_COMPAT(7)>).
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Deprecation is done using attribute macros named
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B<OSSL_DEPRECATEDIN_I<version>>, used with any declaration it applies to.
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Simulating removal is done with C<#ifndef> preprocessor guards using macros
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named B<OPENSSL_NO_DEPRECATED_I<version>>.
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B<OSSL_DEPRECATEDIN_I<version>> and B<OPENSSL_NO_DEPRECATED_I<version>> are
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defined in F<< <openssl/macros.h> >>.
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In those macro names, B<I<version>> corresponds to the OpenSSL release since
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which the deprecation applies, with underscores instead of periods. Because
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of the change in version scheme with OpenSSL 3.0, the B<I<version>> for
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versions before that are three numbers (such as C<1_1_0>), while they are
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two numbers (such as C<3_0>) from 3.0 and on.
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The implementation of a deprecated symbol is kept for one of two reasons:
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=over 4
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=item Planned to be removed
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The symbol and its implementation are planned to be removed some time in the
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future, but needs to remain available until that time.
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Such an implementation needs to be guarded appropriately, as shown in
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L</Implementations to be removed> below.
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=item Planned to remain internally
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The symbol is planned to be removed from public view, but will otherwise
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remain for internal purposes. In this case, the implementation doesn't need
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to change or be guarded.
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However, it's necessary to ensure that the declaration remains available for
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the translation unit where the symbol is used or implemented, even when the
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symbol is publicly unavailable through simulated removal. That's done by
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including an internal header file very early in the affected translation
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units. See L</Implementations to remain internally> below.
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In the future, when the deprecated declaration is to actually be removed
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from public view, it should be moved to an internal header file, with the
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deprecation attribute removed, and the translation units that implement or
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use that symbol should adjust their header inclusions accordingly.
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=back
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=head1 EXAMPLES
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=head2 Header files
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In public header files (F<< <openssl/*.h> >>), this is what a deprecation is
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expected to look like, including the preprocessor wrapping for simulated
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removal:
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# ifndef OPENSSL_NO_DEPRECATED_3_0
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/* ... */
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OSSL_DEPRECATEDIN_3_0 RSA *RSA_new_method(ENGINE *engine);
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/* ... */
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# endif
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=head2 Implementations to be removed
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For a deprecated function that we plan to remove in the future, for example
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RSA_new_method(), the following should be found very early (before including
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any OpenSSL header file) in the translation unit that implements it and in
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any translation unit that uses it:
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/*
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* Suppress deprecation warnings for RSA low level implementations that are
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* kept until removal.
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*/
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#define OPENSSL_SUPPRESS_DEPRECATED
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The RSA_new_method() implementation itself must be guarded the same way as
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its declaration in the public header file is:
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#ifndef OPENSSL_NO_DEPRECATED_3_0
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RSA *RSA_new_method(ENGINE *engine)
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{
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/* ... */
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}
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#endif
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=head2 Implementations to remain internally
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For a deprecated function that we plan to keep internally, for example
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RSA_size(), the following should be found very early (before including any
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other OpenSSL header file) in the translation unit that implements it and in
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any translation unit that uses it:
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/*
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* RSA low level APIs are deprecated for public use, but are kept for
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* internal use.
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*/
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#include "internal/deprecated.h"
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=head1 SEE ALSO
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L<openssl_user_macros(7)>
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=head1 COPYRIGHT
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Copyright 2020-2021 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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