NAME

       CMS_encrypt - create a CMS envelopedData structure

SYNOPSIS

        #include <openssl/cms.h>

        CMS_ContentInfo *CMS_encrypt(STACK_OF(X509) *certs, BIO *in,
                                     const EVP_CIPHER *cipher, unsigned int flags);

DESCRIPTION

       CMS_encrypt() creates and returns a CMS EnvelopedData 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.

NOTES

       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.

       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().

       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().

NOTES

       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().

RETURN VALUES

       CMS_encrypt() returns 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 CMS_STREAM flag was first supported in OpenSSL 1.0.0.

COPYRIGHT

       Copyright 2008-2018 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (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>.