.\" $OpenBSD: CMS_encrypt.3,v 1.4 2019/08/11 12:46:38 schwarze Exp $ .\" full merge up to: OpenSSL 83cf7abf May 29 13:07:08 2018 +0100 .\" .\" This file was written by Dr. Stephen Henson . .\" 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, .\" 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) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: August 11 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) *certs" .Fa "BIO *in" .Fa "const EVP_CIPHER *cipher" .Fa "unsigned int flags" .Fc .Sh DESCRIPTION .Fn CMS_encrypt creates and returns a CMS 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 certificates carrying RSA, Diffie-Hellman or EC keys are supported by this function. .Pp .Xr EVP_des_ede3_cbc 3 (triple DES) is the algorithm of choice for S/MIME use because most clients will support it. .Pp The algorithm passed in the .Fa cipher parameter must support ASN1 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 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 . .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 .Pp If the flag .Dv CMS_STREAM is set, the returned .Vt CMS_ContentInfo structure is .Em not complete and outputting its contents via a function that does not properly finalize the .Vt CMS_ContentInfo structure will give unpredictable results. .Pp Several functions including .Xr SMIME_write_CMS 3 , .Xr i2d_CMS_bio_stream 3 , .Xr PEM_write_bio_CMS_stream 3 finalize the structure. Alternatively finalization can be performed by obtaining the streaming ASN1 .Vt BIO directly using .Xr BIO_new_CMS 3 . .Pp The recipients specified in .Fa certs use a CMS KeyTransRecipientInfo info structure. KEKRecipientInfo is also supported using the flag .Dv CMS_PARTIAL and .Xr CMS_add0_recipient_key 3 . .Pp The parameter .Fa certs may be .Dv NULL if .Dv CMS_PARTIAL is set and recipients are added later using .Xr CMS_add1_recipient_cert 3 or .Xr CMS_add0_recipient_key 3 . .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 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.