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.\" $OpenBSD: CMS_encrypt.3,v 1.5 2019/08/16 11:30:10 schwarze Exp $
.\" full merge up to: OpenSSL 83cf7abf May 29 13:07:08 2018 +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,
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\"
.Dd $Mdocdate: August 16 2019 $
.Dt CMS_ENCRYPT 3
.Os
.Sh NAME
.Nm CMS_encrypt
.Nd create a CMS EnvelopedData structure
.Sh SYNOPSIS
.In openssl/cms.h
.Ft CMS_ContentInfo *
.Fo CMS_encrypt
.Fa "STACK_OF(X509) *certificates"
.Fa "BIO *in"
.Fa "const EVP_CIPHER *cipher"
.Fa "unsigned int flags"
.Fc
.Sh DESCRIPTION
.Fn CMS_encrypt
creates a CMS
.Vt EnvelopedData
structure, encrypting the content provided by
.Fa in .
.Pp
The recipient
.Fa certificates
are added as
.Vt KeyTransRecipientInfo
structures by calling the function
.Xr CMS_add1_recipient_cert 3
internally.
Only certificates carrying RSA, Diffie-Hellman or EC keys are supported
by this function.
The
.Fa certificates
argument can be set to
.Dv NULL
if the
.Dv CMS_PARTIAL
flag is set and recipients are added later using
.Xr CMS_add1_recipient_cert 3
or
.Xr CMS_add0_recipient_key 3 .
.Pp
.Fa cipher
is the symmetric cipher to use.
It must support ASN.1 encoding of its parameters.
.Xr EVP_des_ede3_cbc 3
(triple DES) is the algorithm of choice for S/MIME use because most
clients support it.
.Pp
Many browsers implement a "sign and encrypt" option which is simply an
S/MIME
.Vt EnvelopedData
containing an S/MIME signed message.
This can be readily produced by storing the S/MIME signed message in a
memory BIO and passing it to
.Fn CMS_encrypt .
.Pp
The following flags can be passed in the
.Fa flags
parameter:
.Bl -tag -width Ds
.It Dv CMS_TEXT
MIME headers for type text/plain are prepended 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, then
.Dv CMS_TEXT
is ignored.
.It Dv CMS_USE_KEYID
Use the subject key identifier value to identify recipient certificates.
An error occurs if all recipient certificates do not have a subject key
identifier extension.
By default, issuer name and serial number are used instead.
.It Dv CMS_STREAM
Return a partial
.Vt CMS_ContentInfo
structure suitable for streaming I/O: no data is read from the BIO
.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 content of the returned
.Vt CMS_ContentInfo
structure via a function that does not properly finalize it
will give unpredictable results.
.It Dv CMS_PARTIAL
Return a partial
.Vt CMS_ContentInfo
structure to which additional recipients and attributes can
be added before finalization.
.It Dv CMS_DETACHED
Omit the data being encrypted from the
.Vt CMS_ContentInfo
structure.
This is rarely used in practice and is not supported by
.Xr SMIME_write_CMS 3 .
.El
.Sh RETURN VALUES
.Fn CMS_encrypt
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_decrypt 3
.Sh STANDARDS
RFC 5652: Cryptographic Message Syntax (CMS)
.Bl -dash -compact -offset indent
.It
section 6.1: EnvelopedData Type
.It
section 6.2.1: KeyTransRecipientInfo Type
.El
.Sh HISTORY
.Fn CMS_encrypt
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.
|
