141 lines
4.7 KiB
Groff
141 lines
4.7 KiB
Groff
.\" $OpenBSD: BIO_new_CMS.3,v 1.9 2023/05/01 07:28:11 tb Exp $
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.\" full merge up to: OpenSSL df75c2bfc Dec 9 01:02:36 2018 +0100
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.\"
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.\" This file was written by Dr. Stephen Henson <steve@openssl.org>.
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.\" Copyright (c) 2008 The OpenSSL Project. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\"
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\"
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in
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.\" the documentation and/or other materials provided with the
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.\" distribution.
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.\"
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.\" 3. All advertising materials mentioning features or use of this
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.\" software must display the following acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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.\"
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.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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.\" endorse or promote products derived from this software without
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.\" prior written permission. For written permission, please contact
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.\" openssl-core@openssl.org.
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.\"
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.\" 5. Products derived from this software may not be called "OpenSSL"
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.\" nor may "OpenSSL" appear in their names without prior written
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.\" permission of the OpenSSL Project.
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.\"
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.\" 6. Redistributions of any form whatsoever must retain the following
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.\" acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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.\" OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd $Mdocdate: May 1 2023 $
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.Dt BIO_NEW_CMS 3
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.Os
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.Sh NAME
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.Nm BIO_new_CMS
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.Nd CMS streaming filter BIO
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.Sh SYNOPSIS
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.In openssl/cms.h
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.Ft BIO *
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.Fo BIO_new_CMS
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.Fa "BIO *out"
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.Fa "CMS_ContentInfo *cms"
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.Fc
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.Sh DESCRIPTION
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.Fn BIO_new_CMS
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returns a streaming filter
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.Vt BIO
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chain based on
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.Fa cms .
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The output of the filter is written to
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.Fa out .
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Any data written to the chain is automatically translated
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to a BER format CMS structure of the appropriate type.
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.Pp
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The chain returned by this function behaves like a standard filter
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.Vt BIO .
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It supports non blocking I/O.
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Content is processed and streamed on the fly and not all held in memory
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at once: so it is possible to encode very large structures.
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After all content has been written through the chain,
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.Xr BIO_flush 3
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must be called to finalise the structure.
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.Pp
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The
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.Dv CMS_STREAM
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flag must be included in the corresponding
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.Fa flags
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parameter of the
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.Fa cms
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creation function.
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.Pp
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If an application wishes to write additional data to
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.Fa out ,
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BIOs should be removed from the chain using
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.Xr BIO_pop 3
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and freed with
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.Xr BIO_free 3
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until
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.Fa out
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is reached.
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If no additional data needs to be written,
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.Xr BIO_free_all 3
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can be called to free up the whole chain.
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.Pp
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Any content written through the filter is used verbatim:
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no canonical translation is performed.
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.Pp
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It is possible to chain multiple BIOs to, for example,
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create a triple wrapped signed, enveloped, signed structure.
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In this case it is the application's responsibility
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to set the inner content type of any outer
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.Vt CMS_ContentInfo
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structures.
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.Pp
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Large numbers of small writes through the chain should be avoided as this
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will produce an output consisting of lots of OCTET STRING structures.
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Prepending a
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.Xr BIO_f_buffer 3
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buffering BIO will prevent this.
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.Sh RETURN VALUES
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.Fn BIO_new_CMS
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returns a
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.Vt BIO
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chain when successful or
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.Dv NULL
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if an error occurred.
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The error can be obtained from
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.Xr ERR_get_error 3 .
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.Sh SEE ALSO
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.Xr BIO_new 3 ,
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.Xr CMS_ContentInfo_new 3 ,
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.Xr CMS_encrypt 3 ,
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.Xr CMS_sign 3
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.Sh HISTORY
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.Fn BIO_new_CMS
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first appeared in OpenSSL 1.0.0
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and has been available since
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.Ox 6.7 .
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.Sh BUGS
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There is currently no corresponding inverse BIO
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which can decode a CMS structure on the fly.
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