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.\" $OpenBSD: SMIME_read_PKCS7.3,v 1.8 2021/12/14 14:30:50 schwarze Exp $
.\" full merge up to: OpenSSL 83cf7abf May 29 13:07:08 2018 +0100
.\"
.\" This file was written by Dr. Stephen Henson <steve@openssl.org>.
.\" Copyright (c) 2002, 2006 The OpenSSL Project. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\"
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in
.\" the documentation and/or other materials provided with the
.\" distribution.
.\"
.\" 3. All advertising materials mentioning features or use of this
.\" software must display the following acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
.\"
.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
.\" endorse or promote products derived from this software without
.\" prior written permission. For written permission, please contact
.\" openssl-core@openssl.org.
.\"
.\" 5. Products derived from this software may not be called "OpenSSL"
.\" nor may "OpenSSL" appear in their names without prior written
.\" permission of the OpenSSL Project.
.\"
.\" 6. Redistributions of any form whatsoever must retain the following
.\" acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
.\" OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: December 14 2021 $
.Dt SMIME_READ_PKCS7 3
.Os
.Sh NAME
.Nm SMIME_read_PKCS7
.Nd extract a PKCS#7 object from an S/MIME message
.Sh SYNOPSIS
.In openssl/pkcs7.h
.Ft PKCS7 *
.Fo SMIME_read_PKCS7
.Fa "BIO *in"
.Fa "BIO **bcont"
.Fc
.Sh DESCRIPTION
.Fn SMIME_read_PKCS7
parses a message in S/MIME format.
.Pp
.Fa in
is a
.Vt BIO
to read the message from.
.Pp
If cleartext signing is used, then the content is saved in a memory
.Vt BIO
which is written to
.Pf * Fa bcont ,
otherwise
.Pf * Fa bcont
is set to
.Dv NULL .
.Pp
The parsed PKCS#7 structure is returned, or
.Dv NULL
if an error occurred.
.Pp
If
.Pf * Fa bcont
is not
.Dv NULL ,
then the message is clear text signed.
.Pf * Fa bcont
can then be passed to
.Xr PKCS7_verify 3
with the
.Dv PKCS7_DETACHED
flag set.
.Pp
Otherwise the type of the returned structure can be determined using the
.Fn PKCS7_type_is_*
macros defined in
.In openssl/pkcs7.h .
.Pp
To support future functionality, if
.Fa bcont
is not
.Dv NULL ,
.Pf * Fa bcont
should be initialized to
.Dv NULL .
For example:
.Bd -literal -offset indent
BIO *cont = NULL;
PKCS7 *p7;
p7 = SMIME_read_PKCS7(in, &cont);
.Ed
.Sh RETURN VALUES
.Fn SMIME_read_PKCS7
returns a valid
.Vt PKCS7
structure or
.Dv NULL
if an error occurred.
The error can be obtained from
.Xr ERR_get_error 3 .
.Sh SEE ALSO
.Xr PKCS7_new 3 ,
.Xr SMIME_read_ASN1 3 ,
.Xr SMIME_write_PKCS7 3
.Sh HISTORY
.Fn SMIME_read_PKCS7
first appeared in OpenSSL 0.9.5 and has been available since
.Ox 2.7 .
.Sh BUGS
The MIME parser used by
.Fn SMIME_read_PKCS7
is somewhat primitive.
While it will handle most S/MIME messages, more complex compound
formats may not work.
.Pp
The parser assumes that the
.Vt PKCS7
structure is always base64 encoded, and it will not handle the case
where it is in binary format or uses quoted printable format.
.Pp
The use of a memory
.Vt BIO
to hold the signed content limits the size of the message which can
be processed due to memory restraints: a streaming single pass
option should be available.
|
