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=head1 NAME

CMS_add1_recipient_cert, CMS_add0_recipient_key - add recipients to a CMS enveloped data structure

=head1 SYNOPSIS

 #include <openssl/cms.h>

 CMS_RecipientInfo *CMS_add1_recipient_cert(CMS_ContentInfo *cms,
                                            X509 *recip, unsigned int flags);

 CMS_RecipientInfo *CMS_add0_recipient_key(CMS_ContentInfo *cms, int nid,
                                           unsigned char *key, size_t keylen,
                                           unsigned char *id, size_t idlen,
                                           ASN1_GENERALIZEDTIME *date,
                                           ASN1_OBJECT *otherTypeId,
                                           ASN1_TYPE *otherType);

=head1 DESCRIPTION

CMS_add1_recipient_cert() adds recipient B<recip> to CMS_ContentInfo enveloped
data structure B<cms> as a KeyTransRecipientInfo structure.

CMS_add0_recipient_key() adds symmetric key B<key> of length B<keylen> using
wrapping algorithm B<nid>, identifier B<id> of length B<idlen> and optional
values B<date>, B<otherTypeId> and B<otherType> to CMS_ContentInfo enveloped
data structure B<cms> as a KEKRecipientInfo structure.

The CMS_ContentInfo structure should be obtained from an initial call to
CMS_encrypt() with the flag B<CMS_PARTIAL> set.

=head1 NOTES

The main purpose of this function is to provide finer control over a CMS
enveloped data structure where the simpler CMS_encrypt() function defaults are
not appropriate. For example if one or more KEKRecipientInfo structures
need to be added. New attributes can also be added using the returned
CMS_RecipientInfo structure and the CMS attribute utility functions.

OpenSSL will by default identify recipient certificates using issuer name
and serial number. If B<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.

Currently only AES based key wrapping algorithms are supported for B<nid>,
specifically: NID_id_aes128_wrap, NID_id_aes192_wrap and NID_id_aes256_wrap.
If B<nid> is set to B<NID_undef> then an AES wrap algorithm will be used
consistent with B<keylen>.

=head1 RETURN VALUES

CMS_add1_recipient_cert() and CMS_add0_recipient_key() return an internal
pointer to the CMS_RecipientInfo structure just added or NULL if an error
occurs.

=head1 SEE ALSO

L<ERR_get_error(3)>, L<CMS_decrypt(3)>,
L<CMS_final(3)>,

=head1 COPYRIGHT

Copyright 2008-2016 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<https://www.openssl.org/source/license.html>.

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