165 lines
5 KiB
Groff
165 lines
5 KiB
Groff
.\" $OpenBSD: BN_new.3,v 1.31 2023/07/26 20:08:59 tb Exp $
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.\" full merge up to: OpenSSL man3/BN_new 2457c19d Mar 6 08:43:36 2004 +0000
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.\" selective merge up to: man3/BN_new 681acb31 Sep 29 13:10:34 2017 +0200
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.\" full merge up to: OpenSSL man7/bn 05ea606a May 20 20:52:46 2016 -0400
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.\"
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.\" This file was written by Ulf Moeller <ulf@openssl.org>.
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.\" Copyright (c) 2000, 2004 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: July 26 2023 $
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.Dt BN_NEW 3
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.Os
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.Sh NAME
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.Nm BN_new ,
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.Nm BN_clear ,
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.Nm BN_free ,
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.Nm BN_clear_free
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.Nd allocate and free 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_new
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.Fa void
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.Fc
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.Ft void
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.Fo BN_clear
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.Fa "BIGNUM *a"
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.Fc
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.Ft void
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.Fo BN_free
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.Fa "BIGNUM *a"
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.Fc
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.Ft void
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.Fo BN_clear_free
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.Fa "BIGNUM *a"
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.Fc
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.Sh DESCRIPTION
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The BN library performs arithmetic operations on integers of arbitrary
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size.
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It was written for use in public key cryptography, such as RSA and
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Diffie-Hellman.
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.Pp
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It uses dynamic memory allocation for storing its data structures.
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That means that there is no limit on the size of the numbers manipulated
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by these functions, but return values must always be checked in case a
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memory allocation error has occurred.
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.Pp
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The basic object in this library is a
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.Vt BIGNUM .
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It is used to hold a single large integer.
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This type should be considered opaque and fields should not be modified
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or accessed directly.
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.Pp
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.Fn BN_new
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allocates and initializes a
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.Vt BIGNUM
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structure, in particular setting the value to zero and the flags to
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.Dv BN_FLG_MALLOCED .
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The security-relevant flag
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.Dv BN_FLG_CONSTTIME
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is not set by default.
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.Pp
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.Fn BN_clear
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is used to destroy sensitive data such as keys when they are no longer
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needed.
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It erases the memory used by
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.Fa a
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and sets it to the value 0.
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.Pp
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.Fn BN_free
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frees the components of the
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.Vt BIGNUM
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and, if it was created by
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.Fn BN_new ,
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also the structure itself.
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.Fn BN_clear_free
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additionally overwrites the data before the memory is returned to the
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system.
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If
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.Fa a
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is a
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.Dv NULL
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pointer, no action occurs.
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.Sh RETURN VALUES
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.Fn BN_new
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returns a pointer to the
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.Vt BIGNUM .
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If the allocation fails, it returns
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.Dv NULL
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and sets an error code that 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_add 3 ,
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.Xr BN_add_word 3 ,
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.Xr BN_bn2bin 3 ,
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.Xr BN_cmp 3 ,
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.Xr BN_copy 3 ,
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.Xr BN_CTX_new 3 ,
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.Xr BN_CTX_start 3 ,
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.Xr BN_generate_prime 3 ,
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.Xr BN_get_rfc3526_prime_8192 3 ,
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.Xr BN_kronecker 3 ,
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.Xr BN_mod_inverse 3 ,
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.Xr BN_mod_mul_montgomery 3 ,
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.Xr BN_mod_sqrt 3 ,
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.Xr BN_num_bytes 3 ,
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.Xr BN_rand 3 ,
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.Xr BN_security_bits 3 ,
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.Xr BN_set_bit 3 ,
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.Xr BN_set_flags 3 ,
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.Xr BN_set_negative 3 ,
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.Xr BN_swap 3 ,
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.Xr BN_zero 3 ,
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.Xr crypto 3
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.Sh HISTORY
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.Fn BN_new ,
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.Fn BN_clear ,
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.Fn BN_free ,
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and
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.Fn BN_clear_free
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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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