1.\" $OpenBSD: CMS_encrypt.3,v 1.7 2019/11/02 15:39:46 schwarze Exp $ 2.\" full merge up to: OpenSSL 83cf7abf May 29 13:07:08 2018 +0100 3.\" 4.\" This file was written by Dr. Stephen Henson <steve@openssl.org>. 5.\" Copyright (c) 2008 The OpenSSL Project. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in 16.\" the documentation and/or other materials provided with the 17.\" distribution. 18.\" 19.\" 3. All advertising materials mentioning features or use of this 20.\" software must display the following acknowledgment: 21.\" "This product includes software developed by the OpenSSL Project 22.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 23.\" 24.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 25.\" endorse or promote products derived from this software without 26.\" prior written permission. For written permission, please contact 27.\" openssl-core@openssl.org. 28.\" 29.\" 5. Products derived from this software may not be called "OpenSSL" 30.\" nor may "OpenSSL" appear in their names without prior written 31.\" permission of the OpenSSL Project. 32.\" 33.\" 6. Redistributions of any form whatsoever must retain the following 34.\" acknowledgment: 35.\" "This product includes software developed by the OpenSSL Project 36.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 37.\" 38.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 39.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 40.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 41.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 42.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 43.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 44.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 45.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 46.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 47.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 48.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 49.\" OF THE POSSIBILITY OF SUCH DAMAGE. 50.\" 51.Dd $Mdocdate: November 2 2019 $ 52.Dt CMS_ENCRYPT 3 53.Os 54.Sh NAME 55.Nm CMS_encrypt 56.Nd create a CMS EnvelopedData structure 57.Sh SYNOPSIS 58.In openssl/cms.h 59.Ft CMS_ContentInfo * 60.Fo CMS_encrypt 61.Fa "STACK_OF(X509) *certificates" 62.Fa "BIO *in" 63.Fa "const EVP_CIPHER *cipher" 64.Fa "unsigned int flags" 65.Fc 66.Sh DESCRIPTION 67.Fn CMS_encrypt 68creates a CMS 69.Vt EnvelopedData 70structure, encrypting the content provided by 71.Fa in . 72.Pp 73The recipient 74.Fa certificates 75are added as 76.Vt KeyTransRecipientInfo 77structures by calling the function 78.Xr CMS_add1_recipient_cert 3 79internally. 80Only certificates carrying RSA, Diffie-Hellman or EC keys are supported 81by this function. 82The 83.Fa certificates 84argument can be set to 85.Dv NULL 86if the 87.Dv CMS_PARTIAL 88flag is set and recipients are added later using 89.Xr CMS_add1_recipient_cert 3 90or 91.Xr CMS_add0_recipient_key 3 . 92.Pp 93.Fa cipher 94is the symmetric cipher to use. 95It must support ASN.1 encoding of its parameters. 96.Xr EVP_des_ede3_cbc 3 97(triple DES) is the algorithm of choice for S/MIME use because most 98clients support it. 99.Pp 100Many browsers implement a "sign and encrypt" option which is simply an 101S/MIME 102.Vt EnvelopedData 103containing an S/MIME signed message. 104This can be readily produced by storing the S/MIME signed message in a 105memory BIO and passing it to 106.Fn CMS_encrypt . 107.Pp 108The following flags can be passed in the 109.Fa flags 110parameter: 111.Bl -tag -width Ds 112.It Dv CMS_TEXT 113MIME headers for type text/plain are prepended to the data. 114.It Dv CMS_BINARY 115Do not translate the supplied content into MIME canonical format 116even though that is required by the S/MIME specifications. 117This option should be used if the supplied data is in binary format. 118Otherwise, the translation will corrupt it. 119If 120.Dv CMS_BINARY 121is set, then 122.Dv CMS_TEXT 123is ignored. 124.It Dv CMS_USE_KEYID 125Use the subject key identifier value to identify recipient certificates. 126An error occurs if all recipient certificates do not have a subject key 127identifier extension. 128By default, issuer name and serial number are used instead. 129.It Dv CMS_STREAM 130Return a partial 131.Vt CMS_ContentInfo 132structure suitable for streaming I/O: no data is read from the BIO 133.Fa in . 134Several functions including 135.Xr SMIME_write_CMS 3 , 136.Xr i2d_CMS_bio_stream 3 , 137or 138.Xr PEM_write_bio_CMS_stream 3 139can be used to finalize the structure. 140Alternatively, finalization can be performed by obtaining the streaming 141ASN1 142.Vt BIO 143directly using 144.Xr BIO_new_CMS 3 . 145Outputting the content of the returned 146.Vt CMS_ContentInfo 147structure via a function that does not properly finalize it 148will give unpredictable results. 149.It Dv CMS_PARTIAL 150Return a partial 151.Vt CMS_ContentInfo 152structure to which additional recipients and attributes can 153be added before finalization. 154.It Dv CMS_DETACHED 155Omit the data being encrypted from the 156.Vt CMS_ContentInfo 157structure. 158This is rarely used in practice and is not supported by 159.Xr SMIME_write_CMS 3 . 160.El 161.Sh RETURN VALUES 162.Fn CMS_encrypt 163returns either a 164.Vt CMS_ContentInfo 165structure or 166.Dv NULL 167if an error occurred. 168The error can be obtained from 169.Xr ERR_get_error 3 . 170.Sh SEE ALSO 171.Xr CMS_add0_cert 3 , 172.Xr CMS_add1_recipient_cert 3 , 173.Xr CMS_ContentInfo_new 3 , 174.Xr CMS_decrypt 3 175.Sh STANDARDS 176RFC 5652: Cryptographic Message Syntax (CMS) 177.Bl -dash -compact -offset indent 178.It 179section 6.1: EnvelopedData Type 180.It 181section 6.2.1: KeyTransRecipientInfo Type 182.El 183.Sh HISTORY 184.Fn CMS_encrypt 185first appeared in OpenSSL 0.9.8h 186and has been available since 187.Ox 6.7 . 188.Pp 189The 190.Dv CMS_STREAM 191flag first appeared in OpenSSL 1.0.0. 192