CMS_ENCRYPT(3ossl) OpenSSL CMS_ENCRYPT(3ossl)
NAME
CMS_encrypt_ex, CMS_encrypt - create a CMS envelopedData structure
SYNOPSIS
#include <openssl/cms.h>
CMS_ContentInfo *CMS_encrypt_ex(STACK_OF(X509) *certs, BIO *in,
const EVP_CIPHER *cipher, unsigned int flags,
OSSL_LIB_CTX *libctx, const char *propq);
CMS_ContentInfo *CMS_encrypt(STACK_OF(X509) *certs, BIO *in,
const EVP_CIPHER *cipher, unsigned int flags);
DESCRIPTION
CMS_encrypt_ex() creates and returns a CMS EnvelopedData or
AuthEnvelopedData structure. certs is a list of recipient certificates.
in is the content to be encrypted. cipher is the symmetric cipher to
use. flags is an optional set of flags. The library context libctx and
the property query propq are used internally when retrieving algorithms
from providers.
Only certificates carrying RSA, Diffie-Hellman or EC keys are supported
by this function.
EVP_des_ede3_cbc() (triple DES) is the algorithm of choice for S/MIME
use because most clients will support it.
The algorithm passed in the cipher parameter must support ASN1 encoding
of its parameters. If the cipher mode is GCM, then an AuthEnvelopedData
structure containing MAC is used. Otherwise an EnvelopedData structure
is used. Currently the AES variants with GCM mode are the only
supported AEAD algorithms.
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 CMS_encrypt(3).
The following flags can be passed in the flags parameter.
If the CMS_TEXT flag is set MIME headers for type text/plain are
prepended to the data.
Normally the supplied content is translated into MIME canonical format
(as required by the S/MIME specifications) if CMS_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
CMS_BINARY is set then CMS_TEXT is ignored.
OpenSSL will by default identify recipient certificates using issuer
name and serial number. If CMS_USE_KEYID is set it will use the subject
key identifier value instead. An error occurs if all recipient
certificates do not have a subject key identifier extension.
If the CMS_STREAM flag is set a partial CMS_ContentInfo structure is
returned suitable for streaming I/O: no data is read from the BIO in.
If the CMS_PARTIAL flag is set a partial CMS_ContentInfo structure is
returned to which additional recipients and attributes can be added
before finalization.
The data being encrypted is included in the CMS_ContentInfo structure,
unless CMS_DETACHED is set in which case it is omitted. This is rarely
used in practice and is not supported by SMIME_write_CMS().
If the flag CMS_STREAM is set the returned CMS_ContentInfo structure is
not complete and outputting its contents via a function that does not
properly finalize the CMS_ContentInfo structure will give unpredictable
results.
Several functions including SMIME_write_CMS(), i2d_CMS_bio_stream(),
PEM_write_bio_CMS_stream() finalize the structure. Alternatively
finalization can be performed by obtaining the streaming ASN1 BIO
directly using BIO_new_CMS().
The recipients specified in certs use a CMS KeyTransRecipientInfo info
structure. KEKRecipientInfo is also supported using the flag
CMS_PARTIAL and CMS_add0_recipient_key().
The parameter certs may be NULL if CMS_PARTIAL is set and recipients
added later using CMS_add1_recipient_cert() or
CMS_add0_recipient_key().
CMS_encrypt(3) is similar to CMS_encrypt_ex() but uses default values of
NULL for the library context libctx and the property query propq.
RETURN VALUES
CMS_encrypt(3) return either a CMS_ContentInfo
structure or NULL if an error occurred. The error can be obtained from
ERR_get_error(3).
SEE ALSO
ERR_get_error(3), CMS_decrypt(3)
HISTORY
The function CMS_encrypt_ex() was added in OpenSSL 3.0.
The CMS_STREAM flag was first supported in OpenSSL 1.0.0.
COPYRIGHT
Copyright 2008-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>.
3.3.2 2024-09-04 CMS_ENCRYPT(3ossl)
openssl 3.3.2 - Generated Sat Sep 7 14:11:33 CDT 2024