NAME

       ssl - The ssl application provides secure communication over
         sockets.

DESCRIPTION

       The ssl application is an implementation of the SSL/TLS protocol in Erlang.

         * Supported SSL/TLS-versions are SSL-3.0, TLS-1.0, TLS-1.1, and TLS-1.2.

         * For security reasons SSL-2.0 is not supported.

         * For security reasons SSL-3.0 is no longer supported by default, but can be configured.

         * For  security reasons DES cipher suites are no longer supported by default, but can be
           configured.

         *
            Renegotiation Indication Extension RFC 5746 is supported

         * Ephemeral  Diffie-Hellman  cipher  suites  are  supported,  but  not  Diffie   Hellman
           Certificates cipher suites.

         * Elliptic  Curve  cipher suites are supported if the Crypto application supports it and
           named curves are used.

         * Export cipher suites are not supported as the U.S. lifted its export  restrictions  in
           early 2000.

         * IDEA  cipher suites are not supported as they have become deprecated by the latest TLS
           specification so it is not motivated to implement them.

         * Compression is not supported.

         * CRL validation is supported.

         * Policy certificate extensions are not supported.

         * 'Server Name Indication' extension (RFC 6066) is supported.

         * Application  Layer  Protocol  Negotiation  (ALPN)  and  its  successor  Next  Protocol
           Negotiation (NPN) are supported.

         * It  is  possible  to  use Pre-Shared Key (PSK) and Secure Remote Password (SRP) cipher
           suites, but they are not enabled by default.

DEPENDENCIES

       The SSL application uses the public_key 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:protocol()<optional>:
           Protocol  supported  by  started  clients  and  servers. If this option is not set, it
           defaults to all protocols currently supported 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.

         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.

         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. The PEM cache has proven to be a
           bottleneck, until the  implementation  has  been  improved  this  can  be  used  as  a
           workaround. 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.

ERROR LOGGER AND EVENT HANDLERS

       The  SSL  application  uses  the default OTP error logger to log unexpected errors and TLS
       alerts. The logging of TLS alerts may be turned off with the log_alert option.

SEE ALSO

       application(3erl)