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.\" $OpenBSD: CMS_compress.3,v 1.3 2019/08/10 23:41:22 schwarze Exp $
.\" full merge up to: OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400
.\"
.\" 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: August 10 2019 $
.Dt CMS_COMPRESS 3
.Os
.Sh NAME
.Nm CMS_compress
.Nd create a CMS CompressedData structure
.Sh SYNOPSIS
.In openssl/cms.h
.Ft CMS_ContentInfo *
.Fo CMS_compress
.Fa "BIO *in"
.Fa "int comp_nid"
.Fa "unsigned int flags"
.Fc
.Sh DESCRIPTION
.Fn CMS_compress
creates and returns a CMS CompressedData structure.
.Fa comp_nid
is the compression algorithm to use or
.Dv NID_undef
to use the default algorithm (zlib compression).
.Fa in
is the content to be compressed.
.Fa flags
is an optional set of flags.
.Pp
The only currently supported compression algorithm is zlib using the NID
.Dv NID_zlib_compression .
.Pp
If zlib support is not compiled in, then
.Fn CMS_compress
will return an error.
.Pp
If the
.Dv CMS_TEXT
flag is set, MIME headers for type text/plain are prepended to the data.
.Pp
Normally the supplied content is translated into MIME canonical format
(as required by the S/MIME specifications); if
.Dv CMS_BINARY
is set, no translation occurs.
This option should be used if the supplied data is in binary format.
Otherwise, the translation will corrupt it.
If
.Dv CMS_BINARY
is set then
.Dv CMS_TEXT
is ignored.
.Pp
If the
.Dv CMS_STREAM
flag is set, a partial
.Vt CMS_ContentInfo
structure is returned suitable for streaming I/O: no data is read from
the BIO
.Fa in .
.Pp
The compressed data is included in the
.Vt CMS_ContentInfo
structure unless
.Dv CMS_DETACHED
is set, in which case it is omitted.
This is rarely used in practice and is not supported by
.Xr SMIME_write_CMS 3 .
.Pp
If the flag
.Dv CMS_STREAM
is set, the returned
.Vt CMS_ContentInfo
structure is
.Em not
complete and outputting its contents via a function that does not
properly finalize the
.Vt CMS_ContentInfo
structure will give unpredictable results.
.Pp
Several functions including
.Xr SMIME_write_CMS 3 ,
.Xr i2d_CMS_bio_stream 3 ,
and
.Xr PEM_write_bio_CMS_stream 3
finalize the structure.
Alternatively finalization can be performed by obtaining the streaming
ASN1
.Vt BIO
directly using
.Xr BIO_new_CMS 3 .
.Pp
Additional compression parameters such as the zlib compression level
cannot currently be set.
.Sh RETURN VALUES
.Fn CMS_compress
returns either a
.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_uncompress 3
.Sh HISTORY
.Fn CMS_compress
was added to OpenSSL 0.9.8.
The
.Dv CMS_STREAM
flag was added in OpenSSL 1.0.0.
|
