452 lines
9.7 KiB
Groff
452 lines
9.7 KiB
Groff
.\" $OpenBSD: ECDSA_SIG_new.3,v 1.20 2023/08/29 10:07:42 tb Exp $
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.\" full merge up to: OpenSSL e9b77246 Jan 20 19:58:49 2017 +0100
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.\" selective merge up to: OpenSSL da4ea0cf Aug 5 16:13:24 2019 +0100
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.\"
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.\" This file was written by Nils Larsch <nils@openssl.org>.
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.\" Copyright (c) 2004, 2005, 2013, 2016 The OpenSSL Project.
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.\" 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: August 29 2023 $
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.Dt ECDSA_SIG_NEW 3
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.Os
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.Sh NAME
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.Nm ECDSA_SIG_new ,
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.Nm ECDSA_SIG_free ,
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.Nm ECDSA_SIG_get0 ,
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.Nm ECDSA_SIG_get0_r ,
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.Nm ECDSA_SIG_get0_s ,
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.Nm ECDSA_SIG_set0 ,
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.Nm i2d_ECDSA_SIG ,
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.Nm d2i_ECDSA_SIG ,
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.Nm ECDSA_size ,
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.Nm ECDSA_sign ,
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.Nm ECDSA_verify ,
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.Nm ECDSA_do_sign ,
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.Nm ECDSA_do_verify
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.Nd Elliptic Curve Digital Signature Algorithm
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.Sh SYNOPSIS
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.In openssl/ec.h
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.Ft ECDSA_SIG*
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.Fo ECDSA_SIG_new
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.Fa void
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.Fc
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.Ft void
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.Fo ECDSA_SIG_free
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.Fa "ECDSA_SIG *sig"
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.Fc
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.Ft void
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.Fo ECDSA_SIG_get0
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.Fa "const ECDSA_SIG *sig"
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.Fa "const BIGNUM **r"
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.Fa "const BIGNUM **s"
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.Fc
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.Ft "const BIGNUM *"
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.Fo ECDSA_SIG_get0_r
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.Fa "const ECDSA_SIG *sig"
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.Fc
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.Ft "const BIGNUM *"
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.Fo ECDSA_SIG_get0_s
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.Fa "const ECDSA_SIG *sig"
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.Fc
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.Ft int
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.Fo ECDSA_SIG_set0
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.Fa "ECDSA_SIG *sig"
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.Fa "BIGNUM *r"
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.Fa "BIGNUM *s"
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.Fc
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.Ft int
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.Fo i2d_ECDSA_SIG
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.Fa "const ECDSA_SIG *sig_in"
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.Fa "unsigned char **der_out"
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.Fc
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.Ft ECDSA_SIG*
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.Fo d2i_ECDSA_SIG
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.Fa "ECDSA_SIG **sig_out"
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.Fa "const unsigned char **der_in"
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.Fa "long len"
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.Fc
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.Ft int
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.Fo ECDSA_size
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.Fa "const EC_KEY *eckey"
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.Fc
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.Ft int
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.Fo ECDSA_sign
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.Fa "int type"
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.Fa "const unsigned char *dgst"
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.Fa "int dgstlen"
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.Fa "unsigned char *sig"
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.Fa "unsigned int *siglen"
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.Fa "EC_KEY *eckey"
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.Fc
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.Ft int
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.Fo ECDSA_verify
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.Fa "int type"
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.Fa "const unsigned char *dgst"
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.Fa "int dgstlen"
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.Fa "const unsigned char *sig"
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.Fa "int siglen"
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.Fa "EC_KEY *eckey"
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.Fc
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.Ft ECDSA_SIG*
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.Fo ECDSA_do_sign
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.Fa "const unsigned char *dgst"
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.Fa "int dgst_len"
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.Fa "EC_KEY *eckey"
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.Fc
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.Ft int
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.Fo ECDSA_do_verify
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.Fa "const unsigned char *dgst"
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.Fa "int dgst_len"
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.Fa "const ECDSA_SIG *sig"
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.Fa "EC_KEY* eckey"
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.Fc
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.Sh DESCRIPTION
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These functions provide a low level interface to ECDSA.
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Most applications should use the higher level EVP interface such as
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.Xr EVP_DigestSignInit 3
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or
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.Xr EVP_DigestVerifyInit 3
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instead.
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Creation of the required
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.Vt EC_KEY
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objects is described in
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.Xr EC_KEY_new 3 .
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.Pp
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The
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.Vt ECDSA_SIG
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structure consists of two
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.Vt BIGNUM Ns s
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for the
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.Fa r
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and
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.Fa s
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value of an ECDSA signature (see X9.62 or FIPS 186-2).
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.Bd -literal -offset indent
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struct {
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BIGNUM *r;
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BIGNUM *s;
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} ECDSA_SIG;
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.Ed
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.Pp
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.Fn ECDSA_SIG_new
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allocates a new
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.Vt ECDSA_SIG
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structure (note: this function also allocates the
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.Vt BIGNUM Ns s )
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and initializes it.
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.Pp
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.Fn ECDSA_SIG_free
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frees the
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.Vt ECDSA_SIG
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structure
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.Fa sig .
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.Pp
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.Fn ECDSA_SIG_get0
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retrieves internal pointers the
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.Fa r
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and
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.Fa s
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values contained in
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.Fa sig .
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The values
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.Fa r
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and
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.Fa s
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can also be retrieved separately by the corresponding function
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.Fn ECDSA_SIG_get0_r
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and
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.Fn ECDSA_SIG_get0_s ,
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respectively.
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.Pp
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.Fn ECDSA_SIG_set0
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sets the
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.Fa r
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and
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.Fa s
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values in
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.Fa sig .
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Calling this function transfers the memory management of the values to
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.Fa sig .
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Therefore, the values that have been passed in
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should not be freed by the caller.
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.Pp
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.Fn i2d_ECDSA_SIG
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creates the DER encoding of the ECDSA signature
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.Fa sig_in
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and writes the encoded signature to
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.Pf * Fa der_out .
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.Fn d2i_ECDSA_SIG
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decodes the DER-encoded signature stored in the buffer
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.Pf * Fa der_in
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which is
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.Fa len
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bytes long into
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.Pf * Fa sig_out .
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For details about the semantics, examples, caveats, and bugs, see
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.Xr ASN1_item_d2i 3 .
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.Pp
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.Fn ECDSA_size
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returns the maximum length of a DER-encoded ECDSA signature created with
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the private EC key
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.Fa eckey .
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.Pp
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.Fn ECDSA_sign
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computes a digital signature of the
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.Fa dgstlen
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bytes hash value
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.Fa dgst
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using the private EC key
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.Fa eckey .
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The DER-encoded signature is stored in
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.Fa sig
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and its length is returned in
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.Fa siglen .
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Note:
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.Fa sig
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must point to
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.Fn ECDSA_size
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bytes of memory.
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The parameter
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.Fa type
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is ignored.
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.Pp
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.Fn ECDSA_verify
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verifies that the signature in
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.Fa sig
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of size
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.Fa siglen
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is a valid ECDSA signature of the hash value
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.Fa dgst
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of size
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.Fa dgstlen
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using the public key
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.Fa eckey .
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The parameter
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.Fa type
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is ignored.
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.Pp
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.Fn ECDSA_do_sign
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computes a digital signature of the
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.Fa dgst_len
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bytes hash value
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.Fa dgst
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using the private key
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.Fa eckey .
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The signature is returned in a newly allocated
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.Vt ECDSA_SIG
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structure (or
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.Dv NULL
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on error).
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.Pp
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.Fn ECDSA_do_verify
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verifies that the signature
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.Fa sig
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is a valid ECDSA signature of the hash value
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.Fa dgst
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of size
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.Fa dgst_len
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using the public key
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.Fa eckey .
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.Sh RETURN VALUES
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.Fn ECDSA_SIG_new
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returns the new
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.Vt ECDSA_SIG
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object or
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.Dv NULL
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if an error occurs.
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.Pp
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.Fn i2d_ECDSA_SIG
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returns the number of bytes successfully encoded
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or a negative value if an error occurs.
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.Pp
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.Fn d2i_ECDSA_SIG
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returns a pointer to the decoded
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.Vt ECDSA_SIG
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structure or
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.Dv NULL
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if an error occurs.
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.Pp
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.Fn ECDSA_size
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returns the maximum length signature or 0 on error.
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.Pp
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.Fn ECDSA_SIG_get0_r
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and
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.Fn ECDSA_SIG_get0_s
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return a pointer owned by the
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.Vt ECDSA_SIG
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object if it has been set or
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.Dv NULL
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otherwise.
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.Pp
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.Fn ECDSA_SIG_set0
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and
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.Fn ECDSA_sign
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return 1 if successful or 0 on error.
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.Pp
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.Fn ECDSA_do_sign
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returns a pointer to an allocated
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.Vt ECDSA_SIG
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structure or
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.Dv NULL
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on error.
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.Pp
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.Fn ECDSA_verify
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and
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.Fn ECDSA_do_verify
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return 1 for a valid signature, 0 for an invalid signature and -1 on
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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 EXAMPLES
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Creating an ECDSA signature of given SHA-1 hash value using the named
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curve secp192k1.
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.Pp
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First step: create an
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.Vt EC_KEY
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object.
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This part is
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.Em not
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ECDSA specific.
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.Bd -literal -offset indent
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int ret;
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ECDSA_SIG *sig;
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EC_KEY *eckey;
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eckey = EC_KEY_new_by_curve_name(NID_secp192k1);
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if (eckey == NULL) {
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/* error */
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}
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if (!EC_KEY_generate_key(eckey)) {
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/* error */
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}
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.Ed
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.Pp
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Second step: compute the ECDSA signature of a SHA-1 hash value using
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.Fn ECDSA_do_sign
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.Bd -literal -offset indent
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sig = ECDSA_do_sign(digest, 20, eckey);
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if (sig == NULL) {
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/* error */
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}
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.Ed
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.Pp
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or using
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.Fn ECDSA_sign
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.Bd -literal -offset indent
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unsigned char *buffer, *pp;
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int buf_len;
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buf_len = ECDSA_size(eckey);
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buffer = malloc(buf_len);
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pp = buffer;
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if (!ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey) {
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/* error */
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}
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.Ed
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.Pp
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Third step: verify the created ECDSA signature using
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.Fn ECDSA_do_verify
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.Pp
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.Dl ret = ECDSA_do_verify(digest, 20, sig, eckey);
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.Pp
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or using
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.Fn ECDSA_verify
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.Pp
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.Dl ret = ECDSA_verify(0, digest, 20, buffer, buf_len, eckey);
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.Pp
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and finally evaluate the return value:
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.Bd -literal -offset indent
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if (ret == -1) {
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/* error */
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} else if (ret == 0) {
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/* incorrect signature */
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} else {
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/* ret == 1 */
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/* signature ok */
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}
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.Ed
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.Sh SEE ALSO
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.Xr crypto 3 ,
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.Xr d2i_ECPKParameters 3 ,
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.Xr DSA_new 3 ,
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.Xr EC_GROUP_new 3 ,
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.Xr EC_KEY_METHOD_new 3 ,
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.Xr EC_KEY_new 3 ,
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.Xr EC_KEY_set_ex_data 3 ,
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.Xr EVP_DigestSignInit 3 ,
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.Xr EVP_DigestVerifyInit 3 ,
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.Xr RSA_new 3
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.Sh STANDARDS
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ANSI X9.62, US Federal Information Processing Standard FIPS 186-5
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(Digital Signature Standard, DSS)
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.Sh HISTORY
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.Fn ECDSA_SIG_new ,
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.Fn ECDSA_SIG_free ,
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.Fn i2d_ECDSA_SIG ,
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.Fn d2i_ECDSA_SIG ,
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.Fn ECDSA_size ,
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.Fn ECDSA_sign ,
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.Fn ECDSA_verify ,
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.Fn ECDSA_do_sign ,
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and
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.Fn ECDSA_do_verify
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first appeared in OpenSSL 0.9.8 and have been available since
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.Ox 4.5 .
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.Pp
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.Fn ECDSA_SIG_get0
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and
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.Fn ECDSA_SIG_set0
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first appeared in OpenSSL 1.1.0 and have been available since
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.Ox 6.3 .
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.Fn ECDSA_SIG_get0_r
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and
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.Fn ECDSA_SIG_get0_s
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first appeared in OpenSSL 1.1.1 and have been available since
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.Ox 7.1 .
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.Sh AUTHORS
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.An Nils Larsch
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for the OpenSSL project.
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