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<appref>
  <header>
    <copyright>
      <year>1999</year><year>2015</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at
 
          http://www.apache.org/licenses/LICENSE-2.0

      Unless required by applicable law or agreed to in writing, software
      distributed under the License is distributed on an "AS IS" BASIS,
      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
      See the License for the specific language governing permissions and
      limitations under the License.

    </legalnotice>

    <title>ssl</title>
    <prepared></prepared>
    <docno></docno>
    <date></date>
    <rev></rev>
    <file>ssl_app.sgml</file>
  </header>
  <app>ssl</app>
  <appsummary>The ssl application provides secure communication over
  sockets.</appsummary>

  <description>
    <p>
      The ssl application is an implementation of the SSL/TLS protocol in Erlang.
    </p>
    <list type="bulleted">
      <item>Supported SSL/TLS-versions are SSL-3.0, TLS-1.0,
      TLS-1.1, and TLS-1.2.</item>
      <item>For security reasons SSL-2.0 is not supported.</item>
      <item>For security reasons SSL-3.0 is no longer supported by default,
      but can be configured.</item>
      <item>Ephemeral Diffie-Hellman cipher suites are supported,
      but not Diffie Hellman Certificates cipher suites.</item>
      <item>Elliptic Curve cipher suites are supported if the Crypto 
      application supports it and named curves are used.
      </item>
      <item>Export cipher suites are not supported as the
      U.S. lifted its export restrictions in early 2000.</item>
      <item>IDEA cipher suites are not supported as they have
      become deprecated by the latest TLS specification so it is not 
      motivated to implement them.</item>
      <item>CRL validation is supported.</item>
      <item>Policy certificate extensions are not supported.</item>
      <item>'Server Name Indication' extension client side
      (RFC 6066, Section 3) is supported.</item>
    </list>
   </description>

  <section>
    <title>DEPENDENCIES</title>
    <p>The SSL application uses the <c>public_key</c> 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
    <c>application:start/[1,2]</c> before the SSL application is 
    started.</p>
  </section>

  <section>
    <title>CONFIGURATION</title>
    <p>The application environment configuration parameters in this section 
    are defined for the SSL application. For more information 
    about configuration parameters, see the 
    <seealso marker="kernel:application">application(3)</seealso>
    manual page in Kernel.</p>

    <p>The environment parameters can be set on the command line,
    for example:</p>

    <p><c>erl -ssl protocol_version "['tlsv1.2', 'tlsv1.1']"</c></p>

    <taglist>
      <tag><c>protocol_version = </c><seealso marker="ssl#type-protocol">ssl:protocol()</seealso><c><![CDATA[<optional>]]></c></tag>
      <item><p>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 <c>ssl:connect/[2,3]</c> and <c>ssl:listen/2</c>.</p></item>

      <tag><c><![CDATA[session_lifetime = integer() <optional>]]></c></tag>
      <item><p>Maximum lifetime of the session data in seconds.</p></item>

      <tag><c><![CDATA[session_cb = atom() <optional>]]></c></tag>
      <item><p>Name of the session cache callback module that implements
      the <c>ssl_session_cache_api</c> behavior. Defaults to
      <c>ssl_session_cache</c>.</p></item>

      <tag><c><![CDATA[session_cb_init_args = proplist:proplist() <optional>]]></c></tag>

      <item><p>List of extra user-defined arguments to the <c>init</c> function
      in the session cache callback module. Defaults to <c>[]</c>.</p></item>

      <tag><c><![CDATA[session_cache_client_max = integer() <optional>]]></c><br/>
      <c><![CDATA[session_cache_server_max = integer() <optional>]]></c></tag>
      <item><p>Limits the growth of the clients/servers session cache,
      if the maximum number of sessions is reached, the current cache entries will
      be invalidated regardless of their remaining lifetime. Defaults to 1000.
      </p></item>
      
      <tag><c><![CDATA[ssl_pem_cache_clean = integer() <optional>]]></c></tag>
      <item>
	<p>
	  Number of milliseconds between PEM cache validations.
	</p>
	<seealso
	    marker="ssl#clear_pem_cache-0">ssl:clear_pem_cache/0</seealso>
	
      </item>
      <tag><c><![CDATA[alert_timeout = integer() <optional>]]></c></tag>
      <item>
	<p>
	  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.   
	</p>
      </item>

      
    </taglist>
  </section>

  <section>
    <title>ERROR LOGGER AND EVENT HANDLERS</title>
    <p>The SSL application uses the default <seealso
    marker="kernel:error_logger">OTP error logger</seealso> to log
    unexpected errors and TLS alerts. The logging of TLS alerts may be
    turned off with the <c>log_alert</c> option. </p>
  </section>

  <section>
    <title>SEE ALSO</title>
	<p><seealso marker="kernel:application">application(3)</seealso></p>
  </section>
  
</appref>
