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NAME

       ssl - The ssl application provides secure communication over
         sockets.

DESCRIPTION

       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.

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  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).

ERROR LOGGER AND EVENT HANDLERS

       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.

SEE ALSO

       application(3erl)