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076fc55527
Document thread-safety issues Have RSA_null return NULL (always fails) Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/2244)
89 lines
3.1 KiB
Plaintext
89 lines
3.1 KiB
Plaintext
=pod
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=head1 NAME
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DH_set_default_method, DH_get_default_method,
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DH_set_method, DH_new_method, DH_OpenSSL - select DH method
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=head1 SYNOPSIS
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#include <openssl/dh.h>
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void DH_set_default_method(const DH_METHOD *meth);
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const DH_METHOD *DH_get_default_method(void);
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int DH_set_method(DH *dh, const DH_METHOD *meth);
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DH *DH_new_method(ENGINE *engine);
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const DH_METHOD *DH_OpenSSL(void);
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=head1 DESCRIPTION
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A B<DH_METHOD> specifies the functions that OpenSSL uses for Diffie-Hellman
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operations. By modifying the method, alternative implementations
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such as hardware accelerators may be used. IMPORTANT: See the NOTES section for
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important information about how these DH API functions are affected by the use
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of B<ENGINE> API calls.
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Initially, the default DH_METHOD is the OpenSSL internal implementation, as
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returned by DH_OpenSSL().
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DH_set_default_method() makes B<meth> the default method for all DH
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structures created later.
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B<NB>: This is true only whilst no ENGINE has been set
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as a default for DH, so this function is no longer recommended.
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This function is not thread-safe and should not be called at the same time
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as other OpenSSL functions.
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DH_get_default_method() returns a pointer to the current default DH_METHOD.
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However, the meaningfulness of this result is dependent on whether the ENGINE
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API is being used, so this function is no longer recommended.
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DH_set_method() selects B<meth> to perform all operations using the key B<dh>.
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This will replace the DH_METHOD used by the DH key and if the previous method
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was supplied by an ENGINE, the handle to that ENGINE will be released during the
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change. It is possible to have DH keys that only work with certain DH_METHOD
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implementations (eg. from an ENGINE module that supports embedded
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hardware-protected keys), and in such cases attempting to change the DH_METHOD
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for the key can have unexpected results.
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DH_new_method() allocates and initializes a DH structure so that B<engine> will
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be used for the DH operations. If B<engine> is NULL, the default ENGINE for DH
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operations is used, and if no default ENGINE is set, the DH_METHOD controlled by
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DH_set_default_method() is used.
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A new DH_METHOD object may be constructed using DH_meth_new() (see
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L<DH_meth_new(3)>).
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=head1 RETURN VALUES
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DH_OpenSSL() and DH_get_default_method() return pointers to the respective
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B<DH_METHOD>s.
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DH_set_default_method() returns no value.
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DH_set_method() returns non-zero if the provided B<meth> was successfully set as
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the method for B<dh> (including unloading the ENGINE handle if the previous
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method was supplied by an ENGINE).
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DH_new_method() returns NULL and sets an error code that can be obtained by
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L<ERR_get_error(3)> if the allocation fails. Otherwise it
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returns a pointer to the newly allocated structure.
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=head1 SEE ALSO
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L<DH_new(3)>, L<DH_new(3)>, L<DH_meth_new(3)>
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=head1 COPYRIGHT
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Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (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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