The ssl application is an implementation of the TLS (previously
known as SSL) and DTLS protocols in Erlang.
For current statement of standards compliance see the User's
Guide.
The application environment configuration parameters in this
section are defined for the SSL application. For more information about
configuration parameters, see the application manual page in
Kernel.
All parameters including the wording 'session_ticket' are TLS-1.3
only configuration and other session parameters are prior to TLS-1.3 only
configuration. DTLS versions are based on TLS versions see standard
compliance for mapping.
The environment parameters can be set on the command line, for
example:
erl -ssl protocol_version "['tlsv1.2',
'tlsv1.1']"
protocol_version = ssl:tls_version/0 | [ssl:tls_version/0]
<optional>
Protocol supported by started clients and servers. If
this option is not set, it defaults to all TLS protocols currently supported,
more might be configurable, by the SSL application. This option can be
overridden by the version option to ssl:connect/2,3 and
ssl:listen/2.
dtls_protocol_version = ssl:dtls_version/0 | [ssl:dtls_version/0]
<optional>
Protocol supported by started clients and servers. If
this option is not set, it defaults to all DTLS protocols currently supported,
more might be configurable, by the SSL application. This option can be
overridden by the version option to ssl:connect/2,3 and
ssl:listen/2.
session_lifetime = integer() <optional>
Maximum lifetime of the session data in seconds. Defaults
to 24 hours which is the maximum recommended lifetime by RFC 5246. However
sessions may be invalidated earlier due to the maximum limitation of the
session cache table.
session_cb = atom() <optional>
Deprecated Since OTP-23.3 replaced by
client_session_cb and server_session_cb
client_session_cb = atom() <optional>
Since OTP-23.3 Name client of the session cache callback
module that implements the ssl_session_cache_api behavior. Defaults to
ssl_client_session_cache_db.
server_session_cb = atom() <optional>
Since OTP-23.3 Name of the server session cache callback
module that implements the ssl_session_cache_api behavior. Defaults to
ssl_server_session_cache_db.
session_cb_init_args = proplist:proplist() <optional>
Deprecated Since OTP-23.3 replaced by
client_session_cb_init_args and server_session_cb_init_args
client_session_cb_init_args = proplist:proplist()
<optional>
List of extra user-defined arguments to the init
function in the session cache callback module. Defaults to [].
server_session_cb_init_args = proplist:proplist()
<optional>
List of extra user-defined arguments to the init
function in the session cache callback module. Defaults to [].
•session_cache_client_max = integer()
<optional> Limits the growth of the clients session cache, that is
how many sessions towards servers that are cached to be used by new client
connections. If the maximum number of sessions is reached, the current cache
entries will be invalidated regardless of their remaining lifetime. Defaults
to 1000. Recommended ssl-8.2.1 or later for this option to work as intended.
session_cache_server_max = integer() <optional>
Limits the growth of the servers session cache, that is
how many client sessions are cached by the server. If the maximum number of
sessions is reached, the current cache entries will be invalidated regardless
of their remaining lifetime. Defaults to 1000. Recommended ssl-8.2.1 or later
for this option to work as intended.
ssl_pem_cache_clean = integer() <optional>
Number of milliseconds between PEM cache validations.
Defaults to 2 minutes.
Note: The cache can be reloaded by calling
ssl:clear_pem_cache/0.
bypass_pem_cache = boolean() <optional>
Introduced in ssl-8.0.2. Disables the PEM-cache. Can be
used as a workaround for the PEM-cache bottleneck before ssl-8.1.1. Defaults
to false.
alert_timeout = integer() <optional>
Number of milliseconds between sending of a fatal alert
and closing the connection. Waiting a little while improves the peers chances
to properly receiving the alert so it may shutdown gracefully. Defaults to
5000 milliseconds.
internal_active_n = integer() <optional>
For TLS connections this value is used to handle the
internal socket. As the implementation was changed from an active once to an
active N behavior (N = 100), for performance reasons, this option exist for
possible tweaking or restoring of the old behavior (internal_active_n = 1) in
unforeseen scenarios. The option will not affect erlang distribution over TLS
that will always run in active N mode. Added in ssl-9.1 (OTP-21.2).
server_session_tickets_amount = integer() <optional>
Number of session tickets sent by the server. It must be
greater than 0. Defaults to 3.
server_session_ticket_lifetime = integer() <optional>
Lifetime of session tickets sent by the server. Servers
must not use any value greater than 604800 seconds (7 days). Expired tickets
are automatically removed. Defaults to 7200 seconds (2 hours).
server_session_ticket_store_size = integer() <optional>
Sets the maximum size of the server session ticket store
(stateful tickets). Defaults to 1000. Size limit is enforced by dropping old
tickets.
server_session_ticket_max_early_data = integer()
<optional>
Sets the maximum size of the early data that the server
accepts and also configures its NewSessionTicket messages to include this same
size limit in their early_data_indication extension. Defaults to 16384. Size
limit is enforced by both client and server.
client_session_ticket_lifetime = integer() <optional>
Lifetime of session tickets in the client ticket store.
Expired tickets are automatically removed. Defaults to 7200 seconds (2 hours).
client_session_ticket_store_size = integer() <optional>
Sets the maximum size of the client session ticket store.
Defaults to 1000. Size limit is enforced by dropping old tickets.