= nng_tls_config_auth_mode(3tls)
//
// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
// Copyright 2018 Capitar IT Group BV <info@capitar.com>
//
// This document is supplied under the terms of the MIT License, a
// copy of which should be located in the distribution where this
// file was obtained (LICENSE.txt).  A copy of the license may also be
// found online at https://opensource.org/licenses/MIT.
//

== NAME

nng_tls_config_auth_mode - configure authentication mode

== SYNOPSIS

[source, c]
----
#include <nng/nng.h>
#include <nng/supplemental/tls/tls.h>

typedef enum nng_tls_auth_mode {
        NNG_TLS_AUTH_MODE_NONE,
        NNG_TLS_AUTH_MODE_OPTIONAL,
        NNG_TLS_AUTH_MODE_REQUIRED
} nng_tls_auth_mode;

int nng_tls_config_auth_mode(nng_tls_config *cfg, nng_tls_auth_mode mode);
----

== DESCRIPTION

The `nng_tls_config_auth_mode()` function configures the ((authentication mode))
to be used for TLS sessions using this configuration object.

The possible modes are:

((`NNG_TLS_AUTH_MODE_NONE`))::
No authentication of the TLS peer is performed.
This is the default for
TLS servers, which most typically do not authenticate their clients.

((`NNG_TLS_AUTH_MODE_OPTIONAL`))::
If a certificate is presented by the peer, then it is validated.
However, if the peer does not present a valid certificate,
then the session is allowed to proceed without authentication.

((`NNG_TLS_AUTH_MODE_REQUIRED`))::
A check is made to ensure that the peer has presented a valid certificate
used for the session.
If the peer's certificate is invalid or missing, then the session is refused.
This is the default for clients.

== RETURN VALUES

This function returns 0 on success, and non-zero otherwise.

== ERRORS

[horizontal]
`NNG_ENOMEM`:: Insufficient memory is available.
`NNG_EINVAL`:: An invalid _mode_ was specified.
`NNG_EBUSY`:: The configuration _cfg_ is already in use, and cannot be modified.


== SEE ALSO

[.text-left]
xref:nng_strerror.3.adoc[nng_strerror(3)],
xref:nng_tls_config_alloc.3tls.adoc[nng_tls_config_alloc(3tls)],
xref:nng_tls_config_ca_chain.3tls.adoc[nng_tls_config_ca_chain(3tls)],
xref:nng_tls_config_ca_file.3tls.adoc[nng_tls_config_ca_file(3tls)],
xref:nng_tls_config_server_name.3tls.adoc[nng_tls_config_server_name(3tls)],
xref:nng.7.adoc[nng(7)]