1.\" $OpenBSD: BN_copy.3,v 1.10 2021/12/06 19:45:27 schwarze Exp $ 2.\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100 3.\" 4.\" This file was written by Ulf Moeller <ulf@openssl.org> 5.\" and Matt Caswell <matt@openssl.org>. 6.\" Copyright (c) 2000, 2015 The OpenSSL Project. All rights reserved. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in 17.\" the documentation and/or other materials provided with the 18.\" distribution. 19.\" 20.\" 3. All advertising materials mentioning features or use of this 21.\" software must display the following acknowledgment: 22.\" "This product includes software developed by the OpenSSL Project 23.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 24.\" 25.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 26.\" endorse or promote products derived from this software without 27.\" prior written permission. For written permission, please contact 28.\" openssl-core@openssl.org. 29.\" 30.\" 5. Products derived from this software may not be called "OpenSSL" 31.\" nor may "OpenSSL" appear in their names without prior written 32.\" permission of the OpenSSL Project. 33.\" 34.\" 6. Redistributions of any form whatsoever must retain the following 35.\" acknowledgment: 36.\" "This product includes software developed by the OpenSSL Project 37.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 38.\" 39.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 40.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 41.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 42.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 43.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 44.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 45.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 46.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 47.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 48.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 49.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 50.\" OF THE POSSIBILITY OF SUCH DAMAGE. 51.\" 52.Dd $Mdocdate: December 6 2021 $ 53.Dt BN_COPY 3 54.Os 55.Sh NAME 56.Nm BN_copy , 57.Nm BN_dup , 58.Nm BN_with_flags 59.Nd copy BIGNUMs 60.Sh SYNOPSIS 61.In openssl/bn.h 62.Ft BIGNUM * 63.Fo BN_copy 64.Fa "BIGNUM *to" 65.Fa "const BIGNUM *from" 66.Fc 67.Ft BIGNUM * 68.Fo BN_dup 69.Fa "const BIGNUM *from" 70.Fc 71.Ft void 72.Fo BN_with_flags 73.Fa "BIGNUM *dest" 74.Fa "const BIGNUM *b" 75.Fa "int flags" 76.Fc 77.Sh DESCRIPTION 78.Fn BN_copy 79copies 80.Fa from 81to 82.Fa to . 83.Pp 84.Fn BN_dup 85creates a new 86.Vt BIGNUM 87containing the value 88.Fa from . 89.Pp 90.Fn BN_with_flags 91creates a 92.Em temporary 93shallow copy of 94.Fa b 95in 96.Fa dest . 97It places significant restrictions on the copied data. 98Applications that do not adhere to these restrictions 99may encounter unexpected side effects or crashes. 100For that reason, use of this function is discouraged. 101.Pp 102Any flags provided in 103.Fa flags 104will be set in 105.Fa dest 106in addition to any flags already set in 107.Fa b . 108For example, this can be used to create a temporary copy of a 109.Vt BIGNUM 110with the 111.Dv BN_FLG_CONSTTIME 112flag set for constant time operations. 113.Pp 114The temporary copy in 115.Fa dest 116will share some internal state with 117.Fa b . 118For this reason, the following restrictions apply to the use of 119.Fa dest : 120.Bl -bullet 121.It 122.Fa dest 123should be a newly allocated 124.Vt BIGNUM 125obtained via a call to 126.Xr BN_new 3 . 127It should not have been used for other purposes or initialised in any way. 128.It 129.Fa dest 130must only be used in "read-only" operations, i.e. typically those 131functions where the relevant parameter is declared "const". 132.It 133.Fa dest 134must be used and freed before any further subsequent use of 135.Fa b . 136.El 137.Sh RETURN VALUES 138.Fn BN_copy 139returns 140.Fa to 141on success or 142.Dv NULL 143on error. 144.Fn BN_dup 145returns the new 146.Vt BIGNUM 147or 148.Dv NULL 149on error. 150The error codes can be obtained by 151.Xr ERR_get_error 3 . 152.Sh SEE ALSO 153.Xr BN_new 3 , 154.Xr BN_set_flags 3 155.Sh HISTORY 156.Fn BN_copy 157and 158.Fn BN_dup 159first appeared in SSLeay 0.5.1 and have been available since 160.Ox 2.4 . 161.Pp 162.Fn BN_with_flags 163first appeared in OpenSSL 0.9.7h and 0.9.8a 164and has been available since 165.Ox 4.0 . 166