192 lines
5.9 KiB
Groff
192 lines
5.9 KiB
Groff
.\" $OpenBSD: CMS_encrypt.3,v 1.7 2019/11/02 15:39:46 schwarze Exp $
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.\" full merge up to: OpenSSL 83cf7abf May 29 13:07:08 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: November 2 2019 $
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.Dt CMS_ENCRYPT 3
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.Os
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.Sh NAME
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.Nm CMS_encrypt
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.Nd create a CMS EnvelopedData structure
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.Sh SYNOPSIS
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.In openssl/cms.h
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.Ft CMS_ContentInfo *
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.Fo CMS_encrypt
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.Fa "STACK_OF(X509) *certificates"
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.Fa "BIO *in"
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.Fa "const EVP_CIPHER *cipher"
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.Fa "unsigned int flags"
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.Fc
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.Sh DESCRIPTION
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.Fn CMS_encrypt
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creates a CMS
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.Vt EnvelopedData
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structure, encrypting the content provided by
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.Fa in .
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.Pp
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The recipient
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.Fa certificates
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are added as
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.Vt KeyTransRecipientInfo
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structures by calling the function
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.Xr CMS_add1_recipient_cert 3
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internally.
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Only certificates carrying RSA, Diffie-Hellman or EC keys are supported
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by this function.
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The
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.Fa certificates
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argument can be set to
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.Dv NULL
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if the
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.Dv CMS_PARTIAL
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flag is set and recipients are added later using
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.Xr CMS_add1_recipient_cert 3
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or
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.Xr CMS_add0_recipient_key 3 .
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.Pp
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.Fa cipher
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is the symmetric cipher to use.
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It must support ASN.1 encoding of its parameters.
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.Xr EVP_des_ede3_cbc 3
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(triple DES) is the algorithm of choice for S/MIME use because most
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clients support it.
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.Pp
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Many browsers implement a "sign and encrypt" option which is simply an
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S/MIME
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.Vt EnvelopedData
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containing an S/MIME signed message.
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This can be readily produced by storing the S/MIME signed message in a
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memory BIO and passing it to
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.Fn CMS_encrypt .
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.Pp
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The following flags can be passed in the
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.Fa flags
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parameter:
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.Bl -tag -width Ds
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.It Dv CMS_TEXT
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MIME headers for type text/plain are prepended to the data.
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.It Dv CMS_BINARY
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Do not translate the supplied content into MIME canonical format
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even though that is required by the S/MIME specifications.
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This option should be used if the supplied data is in binary format.
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Otherwise, the translation will corrupt it.
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If
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.Dv CMS_BINARY
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is set, then
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.Dv CMS_TEXT
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is ignored.
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.It Dv CMS_USE_KEYID
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Use the subject key identifier value to identify recipient certificates.
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An error occurs if all recipient certificates do not have a subject key
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identifier extension.
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By default, issuer name and serial number are used instead.
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.It Dv CMS_STREAM
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Return a partial
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.Vt CMS_ContentInfo
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structure suitable for streaming I/O: no data is read from the BIO
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.Fa in .
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Several functions including
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.Xr SMIME_write_CMS 3 ,
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.Xr i2d_CMS_bio_stream 3 ,
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or
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.Xr PEM_write_bio_CMS_stream 3
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can be used to finalize the structure.
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Alternatively, finalization can be performed by obtaining the streaming
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ASN1
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.Vt BIO
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directly using
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.Xr BIO_new_CMS 3 .
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Outputting the content of the returned
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.Vt CMS_ContentInfo
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structure via a function that does not properly finalize it
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will give unpredictable results.
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.It Dv CMS_PARTIAL
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Return a partial
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.Vt CMS_ContentInfo
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structure to which additional recipients and attributes can
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be added before finalization.
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.It Dv CMS_DETACHED
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Omit the data being encrypted from the
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.Vt CMS_ContentInfo
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structure.
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This is rarely used in practice and is not supported by
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.Xr SMIME_write_CMS 3 .
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.El
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.Sh RETURN VALUES
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.Fn CMS_encrypt
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returns either a
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.Vt CMS_ContentInfo
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structure 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 CMS_add0_cert 3 ,
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.Xr CMS_add1_recipient_cert 3 ,
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.Xr CMS_ContentInfo_new 3 ,
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.Xr CMS_decrypt 3
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.Sh STANDARDS
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RFC 5652: Cryptographic Message Syntax (CMS)
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.Bl -dash -compact -offset indent
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.It
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section 6.1: EnvelopedData Type
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.It
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section 6.2.1: KeyTransRecipientInfo Type
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.El
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.Sh HISTORY
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.Fn CMS_encrypt
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first appeared in OpenSSL 0.9.8h
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and has been available since
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.Ox 6.7 .
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.Pp
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The
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.Dv CMS_STREAM
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flag first appeared in OpenSSL 1.0.0.
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