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.\" $OpenBSD: PKCS7_encrypt.3,v 1.10 2019/06/10 14:58:48 schwarze Exp $
.\" OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400
.\"
.\" This file was written by Dr. Stephen Henson <steve@openssl.org>.
.\" Copyright (c) 2002, 2006, 2007, 2008, 2009 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,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
.\" OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: June 10 2019 $
.Dt PKCS7_ENCRYPT 3
.Os
.Sh NAME
.Nm PKCS7_encrypt
.Nd create a PKCS#7 envelopedData structure
.Sh SYNOPSIS
.In openssl/pkcs7.h
.Ft PKCS7 *
.Fo PKCS7_encrypt
.Fa "STACK_OF(X509) *certs"
.Fa "BIO *in"
.Fa "const EVP_CIPHER *cipher"
.Fa "int flags"
.Fc
.Sh DESCRIPTION
.Fn PKCS7_encrypt
creates and returns a PKCS#7 envelopedData structure.
.Fa certs
is a list of recipient certificates.
.Fa in
is the content to be encrypted.
.Fa cipher
is the symmetric cipher to use.
.Fa flags
is an optional set of flags.
.Pp
Only RSA keys are supported in PKCS#7 and envelopedData so the recipient
certificates supplied to this function must all contain RSA public keys,
though they do not have to be signed using the RSA algorithm.
.Pp
The algorithm passed in the
.Fa cipher
parameter must support ASN.1 encoding of its parameters.
.Pp
Many browsers implement a "sign and encrypt" option which is simply an
S/MIME envelopedData containing an S/MIME signed message.
This can be readily produced by storing the S/MIME signed message in a
memory
.Vt BIO
and passing it to
.Fn PKCS7_encrypt .
.Pp
The following flags can be passed in the
.Fa flags
parameter.
.Pp
If the
.Dv PKCS7_TEXT
flag is set, MIME headers for type
.Sy text/plain
are prepended to the data.
.Pp
Normally the supplied content is translated into MIME canonical format
(as required by the S/MIME specifications).
If
.Dv PKCS7_BINARY
is set, no translation occurs.
This option should be used if the supplied data is in binary format;
otherwise, the translation will corrupt it.
If
.Dv PKCS7_BINARY
is set, then
.Dv PKCS7_TEXT
is ignored.
.Pp
If the
.Dv PKCS7_STREAM
flag is set, a partial
.Vt PKCS7
structure is output suitable for streaming I/O: no data is read from
.Fa in .
.Pp
If the flag
.Dv PKCS7_STREAM
is set, the returned
.Vt PKCS7
structure is
.Sy not
complete and outputting its contents via a function that does not
properly finalize the
.Vt PKCS7
structure will give unpredictable results.
.Pp
Several functions, including
.Xr SMIME_write_PKCS7 3 ,
.Xr i2d_PKCS7_bio_stream 3 ,
and
.Xr PEM_write_bio_PKCS7_stream 3 ,
finalize the structure.
Alternatively finalization can be performed by obtaining the streaming
ASN.1
.Vt BIO
directly using
.Fn BIO_new_PKCS7 .
.Sh RETURN VALUES
.Fn PKCS7_encrypt
returns either a
.Vt PKCS7
structure or
.Dv NULL
if an error occurred.
The error can be obtained from
.Xr ERR_get_error 3 .
.Sh SEE ALSO
.Xr PKCS7_decrypt 3 ,
.Xr PKCS7_new 3 ,
.Xr PKCS7_sign 3
.Sh HISTORY
.Fn PKCS7_encrypt
first appeared in OpenSSL 0.9.5 and has been available since
.Ox 2.7 .
.Pp
The
.Dv PKCS7_STREAM
flag was first supported in OpenSSL 1.0.0.
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