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.\" $OpenBSD: CMS_compress.3,v 1.5 2019/08/15 11:42:53 schwarze Exp $
.\" full merge up to: OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400
.\"
.\" This file is a derived work.
.\" The changes are covered by the following Copyright and license:
.\"
.\" Copyright (c) 2019 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.
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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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.\" 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.
.\"
.\" The original 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:
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.\" notice, this list of conditions and the following disclaimer.
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.\" 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/)"
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.\"
.Dd $Mdocdate: August 15 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
.Vt CompressedData
structure.
.Pp
.Fa comp_nid
is the compression algorithm to use or
.Dv NID_undef
to use the default algorithm.
Currently, the default algorithm
.Dv NID_zlib_compression
is the only supported algorithm.
If zlib support is not compiled in,
.Fn CMS_compress
always returns an error.
.Pp
.Fa in
provides the content to be compressed.
.Pp
Any of the following flags (OR'ed together) can be passed in the
.Fa flags
parameter:
.Bl -tag -width Ds
.It Dv CMS_TEXT
Prepend MIME headers for type text/plain to the data.
.It Dv CMS_BINARY
Do not translate the supplied content into MIME canonical format,
even though that is required by the S/MIME specifications.
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,
.Dv CMS_TEXT
is ignored.
.It Dv CMS_STREAM
Return a partial
.Vt CMS_ContentInfo
structure suitable for streaming I/O: no data is read from
.Fa in .
Several functions including
.Xr SMIME_write_CMS 3 ,
.Xr i2d_CMS_bio_stream 3 ,
or
.Xr PEM_write_bio_CMS_stream 3
can be used to finalize the structure.
Alternatively, finalization can be performed by obtaining the streaming
ASN1
.Vt BIO
directly using
.Xr BIO_new_CMS 3 .
Outputting the contents of the
.Vt CMS_ContentInfo
structure via a function that does not
properly finalize it will give unpredictable results.
.It Dv CMS_DETACHED
Do not include the compressed data in the
.Vt CMS_ContentInfo
structure.
This is rarely used in practice and is not supported by
.Xr SMIME_write_CMS 3 .
.El
.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 STANDARDS
RFC 3274: Compressed Data Content Type for Cryptographic Message Syntax (CMS)
.Sh HISTORY
.Fn CMS_compress
first appeared in OpenSSL 0.9.8h
and has been available since
.Ox 6.6 .
.Pp
The
.Dv CMS_STREAM
flag first appeared in OpenSSL 1.0.0.
|
