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.\" $OpenBSD: SMIME_read_CMS.3,v 1.7 2021/12/14 14:30:50 schwarze Exp $
.\" full merge up to: OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
.\"
.\" This file was written by Dr. Stephen Henson <steve@openssl.org>.
.\" Copyright (c) 2008 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_CMS 3
.Os
.Sh NAME
.Nm SMIME_read_CMS
.Nd extract CMS ContentInfo from an S/MIME message
.Sh SYNOPSIS
.In openssl/cms.h
.Ft CMS_ContentInfo *
.Fo SMIME_read_CMS
.Fa "BIO *in"
.Fa "BIO **bcont"
.Fc
.Sh DESCRIPTION
.Fn SMIME_read_CMS
parses a message in S/MIME format from
.Fa in .
.Pp
If the message uses cleartext signing, the content is saved in a memory BIO
which is written to
.Pf * Fa bcont
and which can then be passed to
.Xr CMS_verify 3
with the
.Dv CMS_DETACHED
flag set.
Otherwise,
.Pf * Fa bcont
is set to
.Dv NULL
and the type of the returned structure can be determined using
.Xr CMS_get0_type 3 .
.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;
CMS_ContentInfo *cms = SMIME_read_CMS(in, &cont);
.Ed
.Sh RETURN VALUES
.Fn SMIME_read_CMS
returns a valid
.Vt CMS_ContentInfo
structure or
.Dv NULL
if an error occurred.
The error can be obtained from
.Xr ERR_get_error 3 .
.Sh SEE ALSO
.Xr CMS_ContentInfo_new 3 ,
.Xr CMS_decrypt 3 ,
.Xr CMS_get0_type 3 ,
.Xr CMS_verify 3 ,
.Xr d2i_CMS_ContentInfo 3 ,
.Xr SMIME_read_ASN1 3 ,
.Xr SMIME_write_CMS 3
.Sh HISTORY
.Fn SMIME_read_CMS
first appeared in OpenSSL 0.9.8h
and has been available since
.Ox 6.7 .
.Sh BUGS
The MIME parser used by
.Fn SMIME_read_CMS
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 CMS_ContentInfo
structure is always base64 encoded and will not handle the case
where it is in binary format or uses quoted printable format.
.Pp
The use of a memory 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.
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