- NAME
- SYNOPSIS
- DESCRIPTION
- NOTES
- RETURN VALUES
- SEE ALSO
- HISTORY
- COPYRIGHT

# NAME

CMS_add1_recipient, CMS_add1_recipient_cert, CMS_add0_recipient_key - add recipients to a CMS enveloped data structure

# SYNOPSIS

     #include <openssl/cms.h>

     CMS_RecipientInfo *CMS_add1_recipient(CMS_ContentInfo *cms, X509 *recip,
                                           EVP_PKEY *originatorPrivKey,
                                           X509 *originator, unsigned int flags);

     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);

# DESCRIPTION

CMS_add1_recipient() adds recipient recip and provides the originator pkey originatorPrivKey and originator certificate originator to CMS_ContentInfo. The originator-related fields are relevant only in case when the keyAgreement method of providing of the shared key is in use.

CMS_add1_recipient_cert() adds recipient recip to CMS_ContentInfo enveloped data structure cms as a KeyTransRecipientInfo or KEMRecipientInfo structure, or as a KeyAgreeRecipientInfo structure with an ephemeral key.

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

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

# 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 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 nid, specifically: NID_id_aes128_wrap, NID_id_aes192_wrap and NID_id_aes256_wrap. If nid is set to NID_undef then an AES wrap algorithm will be used consistent with keylen.

# 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.

# SEE ALSO

ERR_get_error(3), CMS_decrypt(3), CMS_final(3),

# HISTORY

CMS_add1_recipient_cert and CMS_add0_recipient_key were added in OpenSSL 3.0.

# COPYRIGHT

Copyright 2008-2025 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.