166 lines
4.5 KiB
Groff
166 lines
4.5 KiB
Groff
.\" $OpenBSD: BN_copy.3,v 1.10 2021/12/06 19:45:27 schwarze Exp $
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.\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
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.\"
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.\" This file was written by Ulf Moeller <ulf@openssl.org>
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.\" and Matt Caswell <matt@openssl.org>.
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.\" Copyright (c) 2000, 2015 The OpenSSL Project. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\"
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\"
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in
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.\" the documentation and/or other materials provided with the
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.\" distribution.
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.\"
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.\" 3. All advertising materials mentioning features or use of this
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.\" software must display the following acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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.\"
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.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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.\" endorse or promote products derived from this software without
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.\" prior written permission. For written permission, please contact
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.\" openssl-core@openssl.org.
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.\"
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.\" 5. Products derived from this software may not be called "OpenSSL"
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.\" nor may "OpenSSL" appear in their names without prior written
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.\" permission of the OpenSSL Project.
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.\"
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.\" 6. Redistributions of any form whatsoever must retain the following
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.\" acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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.\" OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd $Mdocdate: December 6 2021 $
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.Dt BN_COPY 3
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.Os
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.Sh NAME
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.Nm BN_copy ,
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.Nm BN_dup ,
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.Nm BN_with_flags
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.Nd copy BIGNUMs
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.Sh SYNOPSIS
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.In openssl/bn.h
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.Ft BIGNUM *
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.Fo BN_copy
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.Fa "BIGNUM *to"
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.Fa "const BIGNUM *from"
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.Fc
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.Ft BIGNUM *
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.Fo BN_dup
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.Fa "const BIGNUM *from"
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.Fc
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.Ft void
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.Fo BN_with_flags
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.Fa "BIGNUM *dest"
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.Fa "const BIGNUM *b"
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.Fa "int flags"
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.Fc
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.Sh DESCRIPTION
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.Fn BN_copy
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copies
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.Fa from
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to
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.Fa to .
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.Pp
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.Fn BN_dup
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creates a new
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.Vt BIGNUM
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containing the value
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.Fa from .
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.Pp
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.Fn BN_with_flags
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creates a
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.Em temporary
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shallow copy of
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.Fa b
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in
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.Fa dest .
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It places significant restrictions on the copied data.
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Applications that do not adhere to these restrictions
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may encounter unexpected side effects or crashes.
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For that reason, use of this function is discouraged.
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.Pp
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Any flags provided in
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.Fa flags
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will be set in
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.Fa dest
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in addition to any flags already set in
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.Fa b .
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For example, this can be used to create a temporary copy of a
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.Vt BIGNUM
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with the
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.Dv BN_FLG_CONSTTIME
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flag set for constant time operations.
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.Pp
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The temporary copy in
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.Fa dest
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will share some internal state with
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.Fa b .
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For this reason, the following restrictions apply to the use of
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.Fa dest :
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.Bl -bullet
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.It
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.Fa dest
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should be a newly allocated
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.Vt BIGNUM
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obtained via a call to
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.Xr BN_new 3 .
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It should not have been used for other purposes or initialised in any way.
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.It
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.Fa dest
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must only be used in "read-only" operations, i.e. typically those
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functions where the relevant parameter is declared "const".
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.It
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.Fa dest
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must be used and freed before any further subsequent use of
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.Fa b .
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.El
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.Sh RETURN VALUES
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.Fn BN_copy
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returns
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.Fa to
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on success or
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.Dv NULL
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on error.
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.Fn BN_dup
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returns the new
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.Vt BIGNUM
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or
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.Dv NULL
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on error.
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The error codes can be obtained by
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.Xr ERR_get_error 3 .
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.Sh SEE ALSO
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.Xr BN_new 3 ,
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.Xr BN_set_flags 3
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.Sh HISTORY
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.Fn BN_copy
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and
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.Fn BN_dup
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first appeared in SSLeay 0.5.1 and have been available since
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.Ox 2.4 .
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.Pp
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.Fn BN_with_flags
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first appeared in OpenSSL 0.9.7h and 0.9.8a
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and has been available since
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.Ox 4.0 .
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