=pod =head1 NAME CMS_encrypt - create a CMS envelopedData structure =head1 SYNOPSIS #include CMS_ContentInfo *CMS_encrypt(STACK_OF(X509) *certs, BIO *in, const EVP_CIPHER *cipher, unsigned int flags); =head1 DESCRIPTION CMS_encrypt() creates and returns a CMS EnvelopedData structure. B is a list of recipient certificates. B is the content to be encrypted. B is the symmetric cipher to use. B is an optional set of flags. =head1 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 B 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 B parameter. If the B flag is set MIME headers for type B are prepended to the data. Normally the supplied content is translated into MIME canonical format (as required by the S/MIME specifications) if B 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 B is set then B is ignored. OpenSSL will by default identify recipient certificates using issuer name and serial number. If B 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 B flag is set a partial B structure is returned suitable for streaming I/O: no data is read from the BIO B. If the B flag is set a partial B 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 B is set in which case it is omitted. This is rarely used in practice and is not supported by SMIME_write_CMS(). =head1 NOTES If the flag B is set the returned B structure is B complete and outputting its contents via a function that does not properly finalize the B 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 B directly using BIO_new_CMS(). The recipients specified in B use a CMS KeyTransRecipientInfo info structure. KEKRecipientInfo is also supported using the flag B and CMS_add0_recipient_key(). The parameter B may be NULL if B is set and recipients added later using CMS_add1_recipient_cert() or CMS_add0_recipient_key(). =head1 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). =head1 SEE ALSO L, L =head1 HISTORY The B flag was first supported in OpenSSL 1.0.0. =head1 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 L. =cut