static int set_altname(X509 *crt, ...)
	{
	int ret = 0;
	GENERAL_NAMES *gens = NULL;
	GENERAL_NAME *gen = NULL;
	ASN1_IA5STRING *ia5 = NULL;
	va_list ap;
	va_start(ap, crt);
	gens = sk_GENERAL_NAME_new_null();
	if (gens == NULL)
		goto out;
	while (1) {
		int type;
		const char *name;
		type = va_arg(ap, int);
		if (type == 0)
			break;
		name = va_arg(ap, const char *);

		gen = GENERAL_NAME_new();
		if (gen == NULL)
			goto out;
		ia5 = ASN1_IA5STRING_new();
		if (ia5 == NULL)
			goto out;
		if (!ASN1_STRING_set(ia5, name, -1))
			goto out;
		switch (type)
			{
			case GEN_EMAIL:
			case GEN_DNS:
				GENERAL_NAME_set0_value(gen, type, ia5);
				ia5 = NULL;
				break;
			default:
				abort();
			}
		sk_GENERAL_NAME_push(gens, gen);
		gen = NULL;
	}
	if (!X509_add1_ext_i2d(crt, NID_subject_alt_name, gens, 0, 0))
		goto out;
	ret = 1;
 out:
	ASN1_IA5STRING_free(ia5);
	GENERAL_NAME_free(gen);
	GENERAL_NAMES_free(gens);
	va_end(ap);
	return ret;
	}
LWS_VISIBLE LWS_EXTERN int
lws_tls_acme_sni_cert_create(struct lws_vhost *vhost, const char *san_a,
			     const char *san_b)
{
	GENERAL_NAMES *gens = sk_GENERAL_NAME_new_null();
	GENERAL_NAME *gen = NULL;
	ASN1_IA5STRING *ia5 = NULL;
	X509_NAME *name;

	if (!gens)
		return 1;

	vhost->tls.ss = lws_zalloc(sizeof(*vhost->tls.ss), "sni cert");
	if (!vhost->tls.ss) {
		GENERAL_NAMES_free(gens);
		return 1;
	}

	vhost->tls.ss->x509 = X509_new();
	if (!vhost->tls.ss->x509)
		goto bail;

	ASN1_INTEGER_set(X509_get_serialNumber(vhost->tls.ss->x509), 1);
	X509_gmtime_adj(X509_get_notBefore(vhost->tls.ss->x509), 0);
	X509_gmtime_adj(X509_get_notAfter(vhost->tls.ss->x509), 3600);

	vhost->tls.ss->pkey = EVP_PKEY_new();
	if (!vhost->tls.ss->pkey)
		goto bail0;

	if (lws_tls_openssl_rsa_new_key(&vhost->tls.ss->rsa, 4096))
		goto bail1;

	if (!EVP_PKEY_assign_RSA(vhost->tls.ss->pkey, vhost->tls.ss->rsa))
		goto bail2;

	X509_set_pubkey(vhost->tls.ss->x509, vhost->tls.ss->pkey);

	name = X509_get_subject_name(vhost->tls.ss->x509);
	X509_NAME_add_entry_by_txt(name, "C",  MBSTRING_ASC,
				   (unsigned char *)"GB",          -1, -1, 0);
	X509_NAME_add_entry_by_txt(name, "O",  MBSTRING_ASC,
				   (unsigned char *)"somecompany", -1, -1, 0);
	if (X509_NAME_add_entry_by_txt(name, "CN", MBSTRING_UTF8,
				   (unsigned char *)"temp.acme.invalid",
				   	   	   -1, -1, 0) != 1) {
		lwsl_notice("failed to add CN\n");
		goto bail2;
	}
	X509_set_issuer_name(vhost->tls.ss->x509, name);

	/* add the SAN payloads */

	gen = GENERAL_NAME_new();
	ia5 = ASN1_IA5STRING_new();
	if (!ASN1_STRING_set(ia5, san_a, -1)) {
		lwsl_notice("failed to set ia5\n");
		GENERAL_NAME_free(gen);
		goto bail2;
	}
	GENERAL_NAME_set0_value(gen, GEN_DNS, ia5);
	sk_GENERAL_NAME_push(gens, gen);

	if (X509_add1_ext_i2d(vhost->tls.ss->x509, NID_subject_alt_name,
			    gens, 0, X509V3_ADD_APPEND) != 1)
		goto bail2;

	GENERAL_NAMES_free(gens);

	if (san_b && san_b[0]) {
		gens = sk_GENERAL_NAME_new_null();
		gen = GENERAL_NAME_new();
		ia5 = ASN1_IA5STRING_new();
		if (!ASN1_STRING_set(ia5, san_a, -1)) {
			lwsl_notice("failed to set ia5\n");
			GENERAL_NAME_free(gen);
			goto bail2;
		}
		GENERAL_NAME_set0_value(gen, GEN_DNS, ia5);
		sk_GENERAL_NAME_push(gens, gen);

		if (X509_add1_ext_i2d(vhost->tls.ss->x509, NID_subject_alt_name,
				    gens, 0, X509V3_ADD_APPEND) != 1)
			goto bail2;

		GENERAL_NAMES_free(gens);
	}

	/* sign it with our private key */
	if (!X509_sign(vhost->tls.ss->x509, vhost->tls.ss->pkey, EVP_sha256()))
		goto bail2;

#if 0
	{/* useful to take a sample of a working cert for mbedtls to crib */
		FILE *fp = fopen("/tmp/acme-temp-cert", "w+");

		i2d_X509_fp(fp, vhost->tls.ss->x509);
		fclose(fp);
	}
#endif

	/* tell the vhost to use our crafted certificate */
	SSL_CTX_use_certificate(vhost->tls.ssl_ctx, vhost->tls.ss->x509);
	/* and to use our generated private key */
	SSL_CTX_use_PrivateKey(vhost->tls.ssl_ctx, vhost->tls.ss->pkey);

	return 0;

bail2:
	RSA_free(vhost->tls.ss->rsa);
bail1:
	EVP_PKEY_free(vhost->tls.ss->pkey);
bail0:
	X509_free(vhost->tls.ss->x509);
bail:
	lws_free(vhost->tls.ss);
	GENERAL_NAMES_free(gens);

	return 1;
}