NAME

CMS_add1_recipient_cert, CMS_add0_recipient_key — add recipients to a CMS EnvelopedData structure

SYNOPSIS

#include <openssl/cms.h>

CMS_RecipientInfo *
CMS_add1_recipient_cert(CMS_ContentInfo *cms, X509 *certificate, 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

These functions add a new RecipientInfo structure to the recipientInfos field of the EnvelopedData structure cms, which should have been obtained from an initial call to CMS_encrypt(3) with the flag CMS_PARTIAL set.

CMS_add1_recipient_cert() adds the recipient certificate as a KeyTransRecipientInfo structure.

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

The main purpose of these functions is to provide finer control over a CMS EnvelopedData structure where the simpler CMS_encrypt(3) 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.

By default, recipient certificates are identified using issuer name and serial number. If the flag CMS_USE_KEYID is set, the subject key identifier value is used 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

CMS_ContentInfo_new(3), CMS_encrypt(3), CMS_final(3), ERR_get_error(3)

STANDARDS

RFC 5652: Cryptographic Message Syntax

• section 6.1: EnvelopedData Type
• section 6.2.1: KeyTransRecipientInfo Type
• section 6.2.3: KEKRecipientInfo Type

HISTORY

CMS_add1_recipient_cert() and CMS_add0_recipient_key() first appeared in OpenSSL 0.9.8h and have been available since OpenBSD 6.7.