ssl(7) Erlang Application Definition ssl(7)
NAME
ssl - The ssl application provides secure communication over
sockets.
DESCRIPTION
The ssl application is an implementation of the SSL, TLS and DTLS pro-
tocols in Erlang.
For current statement of standards compliance see the User's Guide.
DEPENDENCIES
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.
CONFIGURATION
The application environment configuration parameters in this section
are defined for the SSL application. For more information about config-
uration 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. How-
ever sessions may be invalidated earlier due to the maximum limita-
tion 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 cur-
rent cache entries will be invalidated regardless of their remain-
ing 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. Recom-
mended 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. De-
faults 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 (in-
ternal_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.
ERROR LOGGER AND EVENT HANDLERS
The SSL application uses OTP logger. TLS/DTLS alerts are logged on no-
tice level. Unexpected errors are logged on error level. These log en-
tries 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 in-
spect the TLS handshake setup.
SEE ALSO
application(3erl)
Ericsson AB ssl 10.0 ssl(7)