path: root/lib/ssl/doc/src/ssl.xml

<?xml version="1.0" encoding="latin1" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>1999</year><year>2010</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      The contents of this file are subject to the Erlang Public License,
      Version 1.1, (the "License"); you may not use this file except in
      compliance with the License. You should have received a copy of the
      Erlang Public License along with this software. If not, it can be
      retrieved online at http://www.erlang.org/.

      Software distributed under the License is distributed on an "AS IS"
      basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
      the License for the specific language governing rights and limitations
      under the License.

    </legalnotice>
    <title>ssl</title>
    <file>ssl.xml</file>
  </header>
  <module>ssl</module>
  <modulesummary>Interface Functions for Secure Socket Layer</modulesummary>
  <description>
    <p>This module contains interface functions to the Secure Socket
      Layer. 
    </p>
  </description>
  
  <section>
    <title>SSL</title>

    <list type="bulleted">
      <item>ssl requires the crypto an public_key applications.</item>
      <item>Supported SSL/TLS-versions are SSL-3.0 and TLS-1.0 </item>
      <item>For security reasons sslv2 is not supported.</item>
      <item>Ephemeral Diffie-Hellman cipher suites are supported
      but not Diffie Hellman Certificates cipher suites.</item>
      <item>Export cipher suites are not supported as the
      U.S. lifted its export restrictions in early 2000.</item>
      <item>CRL and policy certificate
            extensions are not supported yet. </item>
    </list>
 
  </section>
  
  <section>
    <title>COMMON DATA TYPES</title>
    <p>The following data types are used in the functions below:
    </p>

    <p><c>boolean() = true | false</c></p> 
    
    <p><c>property() = atom()</c></p>
    
    <p><c>option() = socketoption() | ssloption() | transportoption()</c></p>

     <p><c>socketoption() = [{property(), term()}] - defaults to
      [{mode,list},{packet, 0},{header, 0},{active, true}].
    </c></p>

    <p>For valid options
      see <seealso marker="kernel:inet">inet(3) </seealso> and
      <seealso marker="kernel:gen_tcp">gen_tcp(3) </seealso>.
    </p>
    
    <p> <c>ssloption() = {verify, verify_type()} |
      {fail_if_no_peer_cert, boolean()}
      {depth, integer()} |
      {certfile, path()} | {keyfile, path()} | {password, string()} |
      {cacertfile, path()} | {dhfile, path()} | {ciphers, ciphers()} |
      {ssl_imp, ssl_imp()} | {reuse_sessions, boolean()} | {reuse_session, fun()} 
    </c></p>

    <p><c>transportoption() = {CallbackModule, DataTag, ClosedTag}
	- defaults to {gen_tcp, tcp, tcp_closed}. Ssl may be
	run over any reliable transport protocol that has
	an equivalent API to gen_tcp's.</c></p>
    
    <p><c>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; CallbackModule =
	atom()</c>
    </p> <p><c>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; DataTag =
	atom() - tag used in socket data message.</c></p>
    <p><c>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ClosedTag = atom() - tag used in
    socket close message.</c></p>

    <p><c>verify_type() = verify_none | verify_peer</c></p>
    
    <p><c>path() = string() - representing a file path.</c></p>
    
    <p><c>host() = hostname() | ipaddress()</c></p>
        
    <p><c>hostname() = string()</c></p>
    
    <p><c>
      ip_address() = {N1,N2,N3,N4}  % IPv4
      | {K1,K2,K3,K4,K5,K6,K7,K8}  % IPv6    </c></p>

    <p><c>sslsocket() - opaque to the user. </c></p>
    
    <p><c>protocol() = sslv3 | tlsv1 </c></p>
    
    <p><c>ciphers() = [ciphersuite()] | string() (according to old API)</c></p>
    
    <p><c>ciphersuite() =
      {key_exchange(), cipher(), hash()}</c></p>
    
    <p><c>key_exchange() =  rsa | dhe_dss | dhe_rsa
    </c></p>

   <p><c>cipher() = rc4_128 | des_cbc | '3des_ede_cbc'
      | aes_128_cbc | aes_256_cbc </c></p>

   <p> <c>hash() = md5 | sha
    </c></p>

    <p><c>ssl_imp() = new | old - default is new.</c></p>
    
  </section>
  
<section>
    <title>SSL OPTION DESCRIPTIONS</title>
    
    <taglist>
      <tag>{verify, verify_type()}</tag>
      <item> If <c>verify_none</c> is specified x509-certificate
      path validation errors at the client side
      will not  automatically cause the connection to fail, as
      it will if the verify type is <c>verify_peer</c>. See also
      the option verify_fun.
      Servers only do the path validation if <c>verify_peer</c> is set to
      true, as it then will 
      send a certificate request to
      the client (this message is not sent if the verify option is
      <c>verify_none</c>) and you may then also want to specify
      the option <c>fail_if_no_peer_cert</c>.
      </item>

      <tag>{fail_if_no_peer_cert, boolean()}</tag>
      <item>Used together with {verify, verify_peer} by a ssl server.
      If set to true,
      the server will fail if the client does not have a certificate
      to send, e.i sends a empty certificate, if set to false it will
      only fail if the client sends a invalid certificate (an empty
      certificate is considered valid).
      </item>
      
      <tag>{verify_fun, fun(ErrorList) -> boolean()}</tag>
      <item>Used by the ssl client to determine if 
	x509-certificate path validations errors are acceptable or
	if the connection should fail. Defaults to:
       
<code>
fun(ErrorList) ->
	case lists:foldl(fun({bad_cert,unknown_ca}, Acc) ->
						  Acc;
			    (Other, Acc) ->
				 [Other | Acc]
			 end, [], ErrorList) of
	    [] ->
		true;
	    [_|_] ->
		false
	end
end
</code>
       I.e. by default if the only error found was that the CA-certificate
       holder was unknown this will be accepted.

       Possible errors in the error list are: 
       {bad_cert, cert_expired}, {bad_cert, invalid_issuer},
       {bad_cert, invalid_signature}, {bad_cert, name_not_permitted},
       {bad_cert, unknown_ca},
       {bad_cert, cert_expired}, {bad_cert, invalid_issuer},
       {bad_cert, invalid_signature}, {bad_cert, name_not_permitted},
       {bad_cert, cert_revoked} (not implemented yet),
       {bad_cert, unknown_critical_extension} or {bad_cert, term()}
      </item>

      
      <tag>{validate_extensions_fun, fun()}</tag>
      <item>
	This options makes it possible to supply a fun to validate
	possible application specific certificate extensions
	during the certificat path validation. This option
	will be better documented onec the public_key API is more
	mature.
      </item>
      
      <tag>{depth, integer()}</tag>
      <item>Specifies the maximum
      verification depth, i.e. how far in a chain of certificates the
      verification process can proceed before the verification is
      considered to fail. Peer certificate = 0, CA certificate = 1,
      higher level CA certificate = 2, etc.  The value 2 thus means
      that a chain can at most contain peer cert, CA cert, next CA
      cert, and an additional CA cert. The default value is 1.
      </item>

      <tag>{certfile, path()}</tag>
      <item>Path to a file containing the
          user's certificate. Optional for clients but note
      that some servers requires that the client can certify
      itself. </item>
      <tag>{keyfile, path()}</tag>
      <item>Path to file containing user's
      private PEM encoded key. As PEM-files may contain several
      entries this option defaults to the same file as given by
      certfile option.</item>
      <tag>{password, string()}</tag>
      <item>String containing the user's password.
	Only used if the private keyfile is password protected.
      </item>
      <tag>{cacertfile, path()}</tag>
      <item>Path to file containing PEM encoded
      CA certificates (trusted certificates used for verifying a peer
      certificate). May be omitted if you do not want to verify
      the peer.</item>

      <tag>{dhfile, path()}</tag>
      <item>Path to file containing PEM encoded Diffie Hellman parameters,
      for the server to use if a cipher suite using Diffie Hellman key exchange
      is negotiated. If not specified hardcode parameters will be used.
      </item>
      
      <tag>{ciphers, ciphers()}</tag>
      <item>The function <c>ciphers_suites/0</c> can
	be used to find all available ciphers.
      </item>

      <tag>{ssl_imp, ssl_imp()}</tag>
      <item>Specify which ssl implementation you want to use. Defaults to
      new.
      </item>

      <tag>{reuse_sessions, boolean()}</tag>
      <item>Specifies if ssl sessions should be reused
	when possible.
      </item>

       <tag>{reuse_session, fun(SuggestedSessionId,
       PeerCert, Compression, CipherSuite) -> boolean()}</tag>
      <item>Enables the ssl server to have a local policy
      for deciding if a session should be reused or not,
      only meaning full if <c>reuse_sessions</c> is set to true.
      SuggestedSessionId is a binary(),  PeerCert is a DER encoded
      certificate, Compression is an enumeration integer
      and CipherSuite of type ciphersuite().      
      </item>

      <tag>{secure_renegotiate, boolean()}</tag>
      <item>Specifies if to reject renegotiation attempt that does
      not live up to RFC 5746. By default secure_renegotiate is
      set to false e.i. secure renegotiation will be used if possible
      but it will fallback to unsecure renegotiation if the peer
      does not support  RFC 5746.
      </item>

    </taglist>
  </section>
  
  <section>
    <title>General</title>
      
    <p>When a ssl socket is in active mode (the default), data from the
      socket is delivered to the owner of the socket in the form of
      messages:
    </p>
    <list type="bulleted">
      <item>{ssl, Socket, Data}
      </item>
      <item>{ssl_closed, Socket}
      </item>
      <item>
        {ssl_error, Socket, Reason}
      </item>
    </list>
    
    <p>A <c>Timeout</c> argument specifies a timeout in milliseconds. The 
      default value for a <c>Timeout</c> argument is <c>infinity</c>.
    </p>
  </section>
  
  <funcs>
    <func>
      <name>cipher_suites() -></name>
      <name>cipher_suites(Type) -> ciphers()</name>
      <fsummary> Returns a list of supported cipher suites</fsummary>
      <type>
        <v>Type = erlang | openssl</v>

      </type>
      <desc><p>Returns a list of supported cipher suites.
	cipher_suites() is equivalent to cipher_suites(erlang).
	Type openssl is provided for backwards compatibility with
	old ssl that used openssl.
	</p>
    </desc>
    </func>
    
    <func>
      <name>connect(Socket, SslOptions) -> </name>
      <name>connect(Socket, SslOptions, Timeout) -> {ok, SslSocket}
	| {error, Reason}</name>
      <fsummary> Upgrades a gen_tcp, or
	equivalent, connected socket to a ssl socket. </fsummary>
      <type>
        <v>Socket = socket()</v>
        <v>SslOptions = [ssloption()]</v>
	<v>Timeout = integer() | infinity</v>
	<v>SslSocket = sslsocket()</v>
	<v>Reason = term()</v>
      </type>
      <desc> <p>Upgrades a gen_tcp, or equivalent,
	  connected socket to a ssl socket e.i performs the
	  client-side ssl handshake.</p>
    </desc>
    </func>

    <func>
      <name>connect(Host, Port, Options) -></name>
      <name>connect(Host, Port, Options, Timeout) ->
	  {ok, SslSocket} | {error, Reason}</name>
      <fsummary>Opens an ssl connection to Host, Port. </fsummary>
      <type>
	  <v>Host = host()</v>
	  <v>Port = integer()</v>
	  <v>Options = [option()]</v>
	  <v>Timeout = integer() | infinity</v>
	  <v>SslSocket = sslsocket()</v>
	  <v>Reason = term()</v>
      </type>
      <desc> <p>Opens an ssl connection to Host, Port.</p> </desc>
    </func>

    <func>
      <name>close(SslSocket) -> ok | {error, Reason}</name>
      <fsummary>Close a ssl connection</fsummary>
      <type>
	  <v>SslSocket = sslsocket()</v>
	  <v>Reason = term()</v>
      </type>
      <desc><p>Close a ssl connection.</p>
      </desc>
    </func>

    <func>
      <name>controlling_process(SslSocket, NewOwner) ->
	ok | {error, Reason}</name>
      
	<fsummary>Assigns a new controlling process to the
	ssl-socket.</fsummary>
      
	<type>
	  <v>SslSocket = sslsocket()</v>
	  <v>NewOwner = pid()</v>
	  <v>Reason = term()</v>
	</type>
	<desc><p>Assigns a new controlling process to the ssl-socket. A
      controlling process is the owner of a ssl-socket, and receives
      all messages from the socket.</p>
      </desc>
    </func>

    <func>
	<name>connection_info(SslSocket) ->
	  {ok, {ProtocolVersion, CipherSuite}} |  {error, Reason} </name>
      <fsummary>Returns the negotiated protocol version and cipher suite.
      </fsummary>
      <type>
        <v>CipherSuite = ciphersuite()</v>
        <v>ProtocolVersion = protocol()</v>
      </type>
      <desc><p>Returns the negotiated protocol version and cipher suite.</p> 
      </desc>
    </func>

     <func>
      <name>format_error(Reason) -> string()</name>
      <fsummary>Return an error string.</fsummary>
      <type>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>Presents the error returned by an ssl function as a printable string.</p>
      </desc>
    </func>
   
    <func>
      <name>getopts(Socket) -> </name>
      <name>getopts(Socket, OptionNames) ->
	{ok, [socketoption()]} | {error, Reason}</name>
      <fsummary>Get the value of the specified options.</fsummary>
      <type>
	<v>Socket = sslsocket()</v>
	<v>OptionNames = [property()]</v>
      </type>
      <desc>
	<p>Get the value of the specified socket options, if no
	  options are specified all options are returned.
	</p>
      </desc>
    </func>

    <func>
      <name>listen(Port, Options) ->
	{ok, ListenSocket} | {error, Reason}</name>
      <fsummary>Creates a ssl listen socket.</fsummary>
      <type>
	<v>Port = integer()</v>
	<v>Options = options()</v>
	<v>ListenSocket = sslsocket()</v>
      </type>
      <desc>
	<p>Creates a ssl listen socket.</p>
      </desc>
    </func>

    <func>
      <name>peercert(Socket) -> {ok, Cert} | {error, Reason}</name>
      <fsummary>Return the peer certificate.</fsummary>
     <type>
        <v>Socket = sslsocket()</v>
        <v>Cert = binary()</v>
      </type>
      <desc>
        <p>The peer certificate is returned as a DER encoded binary.
	  The certificate can be decoded with <c>public_key:pkix_decode_cert/2</c>.
        </p>
      </desc>
    </func>
    <func>
      <name>peername(Socket) -> {ok, {Address, Port}} |
	{error, Reason}</name>
      <fsummary>Return peer address and port.</fsummary>
      <type>
        <v>Socket = sslsocket()</v>
        <v>Address = ipaddress()</v>
        <v>Port = integer()</v>
      </type>
      <desc>
        <p>Returns the address and port number of the peer.</p>
      </desc>
    </func>
    
    <func>
      <name>recv(Socket, Length) -> </name>
      <name>recv(Socket, Length, Timeout) -> {ok, Data} | {error,
	Reason}</name>
      <fsummary>Receive data on a socket.</fsummary>
      <type>
        <v>Socket = sslsocket()</v>
        <v>Length = integer()</v>
        <v>Timeout = integer()</v>
        <v>Data = [char()] | binary()</v>
      </type>
      <desc>
        <p>This function receives a packet from a socket in passive
          mode. A closed socket is indicated by a return value
          <c>{error, closed}</c>.</p>
        <p>The <c>Length</c> argument is only meaningful when
          the socket is in <c>raw</c> mode and denotes the number of
          bytes to read. If <c>Length</c> = 0, all available bytes are
          returned. If <c>Length</c> &gt; 0, exactly <c>Length</c>
          bytes are returned, or an error; possibly discarding less
          than <c>Length</c> bytes of data when the socket gets closed
          from the other side.</p>
        <p>The optional <c>Timeout</c> parameter specifies a timeout in
          milliseconds. The default value is <c>infinity</c>.</p>
      </desc>
    </func>
    
    <func>
      <name>renegotiate(Socket) -> ok | {error, Reason}</name>
      <fsummary> Initiates a new handshake.</fsummary>
      <type>
	<v>Socket = sslsocket()</v>
      </type>
      <desc><p>Initiates a new handshake. A notable return value is
      <c>{error, renegotiation_rejected}</c> indicating that the peer
      refused to go through with the renegotiation but the connection
      is still active using the previously negotiated session.</p>
      </desc>
    </func>
    
    <func>
      <name>send(Socket, Data) -> ok | {error, Reason}</name>
      <fsummary>Write data to a socket.</fsummary>
      <type>
        <v>Socket = sslsocket()</v>
        <v>Data = iolist() | binary()</v>
      </type>
      <desc>
        <p>Writes <c>Data</c> to <c>Socket</c>. </p>
        <p>A notable return value is <c>{error, closed}</c> indicating that
          the socket is closed.</p>
      </desc>
    </func>
    <func>
      <name>setopts(Socket, Options) -> ok | {error, Reason}</name>
      <fsummary>Set socket options.</fsummary>
      <type>
        <v>Socket = sslsocket()</v>
        <v>Options = [socketoption]()</v>
      </type>
      <desc>
        <p>Sets options according to <c>Options</c> for the socket 
          <c>Socket</c>. </p>
      </desc>
    </func>

    <func>
      <name>shutdown(Socket, How) -> ok | {error, Reason}</name>
      <fsummary>Immediately close a socket</fsummary>
      <type>
        <v>Socket = sslsocket()</v>
        <v>How = read | write | read_write</v>
        <v>Reason = reason()</v>
      </type>
      <desc>
        <p>Immediately close a socket in one or two directions.</p>
        <p><c>How == write</c> means closing the socket for writing,
          reading from it is still possible.</p>
        <p>To be able to handle that the peer has done a shutdown on
          the write side, the <c>{exit_on_close, false}</c> option
          is useful.</p>
      </desc>
    </func>
    
    <func>
      <name>ssl_accept(ListenSocket) -> </name>
      <name>ssl_accept(ListenSocket, Timeout) -> ok | {error, Reason}</name>
      <fsummary>Perform server-side SSL handshake</fsummary>
      <type>
        <v>ListenSocket = sslsocket()</v>
        <v>Timeout = integer()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p>The <c>ssl_accept</c> function establish the SSL connection
          on the server side. It should be called directly after
          <c>transport_accept</c>, in the spawned server-loop.</p>
      </desc>
    </func>

    <func>
      <name>ssl_accept(ListenSocket, SslOptions) -> </name>
      <name>ssl_accept(ListenSocket, SslOptions, Timeout) -> {ok, Socket} | {error, Reason}</name>
      <fsummary>Perform server-side SSL handshake</fsummary>
      <type>
        <v>ListenSocket = socket()</v>
	<v>SslOptions = ssloptions()</v>
        <v>Timeout = integer()</v>
        <v>Reason = term()</v>
      </type>
      <desc>
        <p> Upgrades a gen_tcp, or
	  equivalent, socket to a ssl socket e.i performs the
	ssl server-side handshake.</p>
	<p><note>Note that the listen socket should be in {active, false} mode
	before telling the client that the server is ready to upgrade
	and calling this function, otherwise the upgrade may
	or may not succeed depending on timing.</note></p>
      </desc>
    </func>
    
    <func>
      <name>sockname(Socket) -> {ok, {Address, Port}} |
	{error, Reason}</name>
      <fsummary>Return the local address and port.</fsummary>
      <type>
        <v>Socket = sslsocket()</v>
        <v>Address = ipaddress()</v>
        <v>Port = integer()</v>
      </type>
      <desc>
        <p>Returns the local address and port number of the socket
          <c>Socket</c>.</p>
      </desc>
    </func>
    
    <func>
      <name>start() -> </name>
      <name>start(Type) -> ok | {error, Reason}</name>
      <fsummary>Starts the Ssl application. </fsummary>
      <type>
        <v>Type =  permanent | transient | temporary</v>
      </type>
      <desc>
        <p>Starts the Ssl application. Default type
          is temporary.
          <seealso marker="kernel:application">application(3)</seealso></p>
      </desc>
    </func>
    <func>
      <name>stop() -> ok </name>
      <fsummary>Stops the Ssl application.</fsummary>
      <desc>
        <p>Stops the Ssl application.
          <seealso marker="kernel:application">application(3)</seealso></p>
      </desc>
    </func>

    <func>
      <name>transport_accept(Socket) -></name>
      <name>transport_accept(Socket, Timeout) ->
	{ok, NewSocket} | {error, Reason}</name>
      <fsummary>Accept an incoming connection and
	prepare for <c>ssl_accept</c></fsummary>
      <type>
        <v>Socket = NewSocket = sslsocket()</v>
        <v>Timeout = integer()</v>
        <v>Reason = reason()</v>
      </type>
      <desc>
        <p>Accepts an incoming connection request on a listen socket.
          <c>ListenSocket</c> must be a socket returned from
          <c>listen/2</c>.  The socket returned should be passed to
          <c>ssl_accept</c> to complete ssl handshaking and
          establishing the connection.</p>
        <warning>
          <p>The socket returned can only be used with <c>ssl_accept</c>,
            no traffic can be sent or received before that call.</p>
        </warning>
        <p>The accepted socket inherits the options set for
          <c>ListenSocket</c> in <c>listen/2</c>.</p>
	<p>The default
          value for <c>Timeout</c> is <c>infinity</c>. If
          <c>Timeout</c> is specified, and no connection is accepted
          within the given time, <c>{error, timeout}</c> is
          returned.</p>
      </desc>
    </func>
    
    <func>
      <name>versions() ->
	[{SslAppVer, SupportedSslVer, AvailableSslVsn}]</name>
      <fsummary>Returns version information relevant for the
	ssl application.</fsummary>
      <type>
	<v>SslAppVer = string()</v>
      	<v>SupportedSslVer = [protocol()]</v>
      	<v>AvailableSslVsn = [protocol()]</v>
      </type>
      <desc>
	<p>
	  Returns version information relevant for the
	  ssl application.</p>
      </desc>
    </func>
  </funcs> 
      
  <section>
    <title>SEE ALSO</title>
    <p><seealso marker="kernel:inet">inet(3) </seealso> and 
      <seealso marker="kernel:gen_tcp">gen_tcp(3) </seealso>
    </p>
  </section>

</erlref>