OpenSSL::PKCS7#add_signer

static VALUE
ossl_pkcs7_add_signer(VALUE self, VALUE signer)
{
    PKCS7 *pkcs7;
    PKCS7_SIGNER_INFO *p7si;

    p7si = DupPKCS7SignerPtr(signer); /* NEED TO DUP */
    GetPKCS7(self, pkcs7);
    if (!PKCS7_add_signer(pkcs7, p7si)) {
        PKCS7_SIGNER_INFO_free(p7si);
        ossl_raise(ePKCS7Error, "Could not add signer.");
    }
    if (PKCS7_type_is_signed(pkcs7)){
        PKCS7_add_signed_attribute(p7si, NID_pkcs9_contentType,
                                   V_ASN1_OBJECT, OBJ_nid2obj(NID_pkcs7_data));
    }

    return self;
}