.\" $OpenBSD: CMS_uncompress.3,v 1.7 2019/11/02 15:39:46 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>.
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.Dd $Mdocdate: November 2 2019 $
.Dt CMS_UNCOMPRESS 3
.Os
.Sh NAME
.Nm CMS_uncompress
.Nd uncompress a CMS CompressedData structure
.Sh SYNOPSIS
.In openssl/cms.h
.Ft int
.Fo CMS_uncompress
.Fa "CMS_ContentInfo *cms"
.Fa "BIO *dcont"
.Fa "BIO *out"
.Fa "unsigned int flags"
.Fc
.Sh DESCRIPTION
.Fn CMS_uncompress
extracts and uncompresses the content of a CMS
.Vt CompressedData
structure
.Fa cms
and writes it to
.Fa out .
.Pp
In the rare case where the compressed content is detached,
pass it in via
.Fa dcont .
For normal use, set
.Fa dcont
to
.Dv NULL .
.Pp
The only currently supported compression algorithm is zlib: if the
structure indicates the use of any other algorithm, an error is returned.
If zlib support is not compiled in,
.Fn CMS_uncompress
always returns an error.
.Pp
If the
.Dv CMS_TEXT
bit is set in
.Fa flags ,
MIME headers for type text/plain are deleted from the content.
If the content is not of type text/plain, an error is returned.
.Sh RETURN VALUES
.Fn CMS_uncompress
returns 1 for success or 0 for failure.
The error can be obtained from
.Xr ERR_get_error 3 .
.Sh SEE ALSO
.Xr CMS_compress 3 ,
.Xr CMS_ContentInfo_new 3
.Sh STANDARDS
RFC 3274: Compressed Data Content Type for Cryptographic Message Syntax (CMS)
.Sh HISTORY
.Fn CMS_uncompress
first appeared in OpenSSL 0.9.8h
and has been available since
.Ox 6.7 .
.Sh BUGS
The lack of single pass processing and the need to hold all data in
memory as mentioned in
.Xr CMS_verify 3
also applies to
.Fn CMS_uncompress .