.\" $OpenBSD: ASN1_item_digest.3,v 1.2 2022/09/11 04:39:46 jsg Exp $
.\"
.\" Copyright (c) 2021 Ingo Schwarze <schwarze@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: September 11 2022 $
.Dt ASN1_ITEM_DIGEST 3
.Os
.Sh NAME
.Nm ASN1_item_digest
.Nd DER-encode and hash an ASN.1 value
.Sh SYNOPSIS
.In openssl/x509.h
.Ft int
.Fo ASN1_item_digest
.Fa "const ASN1_ITEM *it"
.Fa "const EVP_MD *type"
.Fa "void *val_in"
.Fa "unsigned char *md"
.Fa "unsigned int *s"
.Fc
.Sh DESCRIPTION
.Fn ASN1_item_digest
assumes that
.Fa val_in
is an
.Vt ASN1_VALUE
of the type specified by
.Fa it ,
encodes it into DER format by calling
.Xr ASN1_item_i2d 3 ,
hashes the resulting byte array using the digest
.Fa type
by calling
.Xr EVP_Digest 3 ,
places the digest value into
.Pf * Fa md ,
and, unless
.Fa s
is
.Dv NULL ,
places the length in bytes of the digest into
.Pf * Fa s .
Providing a buffer
.Pf * Fa md
large enough to contain the digest is the responsibility of the caller;
providing a buffer of
.Dv EVP_MAX_MD_SIZE
bytes is recommended.
.Sh RETURN VALUES
.Fn ASN1_item_digest
returns 1 for success or 0 if encoding or hashing fails.
.Sh SEE ALSO
.Xr ASN1_item_i2d 3 ,
.Xr ASN1_item_sign 3 ,
.Xr EVP_Digest 3
.Sh HISTORY
.Fn ASN1_item_digest
first appeared in OpenSSL 0.9.7 and has been available since
.Ox 3.1 .