ssl - The ssl application provides secure communication over
sockets.
The ssl application is an implementation of the SSL, TLS and DTLS
protocols in Erlang.
For current statement of standards compliance see the User's
Guide.
The SSL application uses the public_key, asn1 and
Crypto application to handle public keys and encryption, hence these
applications must be loaded for the SSL application to work. In an embedded
environment this means they must be started with
application:start/[1,2] before the SSL application is started.
The application environment configuration parameters in this
section are defined for the SSL application. For more information about
configuration parameters, see the application(3erl) manual page in
Kernel.
The environment parameters can be set on the command line, for
example:
erl -ssl protocol_version "['tlsv1.2',
'tlsv1.1']"
- protocol_version
= ssl:ssl_tls_protocol()<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_protocol()<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>:
- Name of the session cache callback module that implements the
ssl_session_cache_api behavior. Defaults to
ssl_session_cache.
- 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.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.
- 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.
The SSL application uses OTP logger. TLS/DTLS alerts are logged on
notice level. Unexpected errors are logged on error level. These log entries
will by default end up in the default Erlang log. The option
log_level may be used to in run-time to set the log level of a
specific TLS connection, which is handy when you want to use level debug to
inspect the TLS handshake setup.