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

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<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>2004</year><year>2012</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>ssh</title>
    <prepared>Ingela Anderton Andin</prepared>
    <responsible>H&aring;kan Mattsson</responsible>
    <docno></docno>
    <approved>H&aring;kan Mattsson</approved>
    <checked></checked>
    <date>2007-10-06</date>
    <rev>PA1</rev>
  </header>
  <module>ssh</module>
  <modulesummary>Main API of the SSH application</modulesummary>
  <description>
    <p>Interface module for the SSH application. </p>
  </description>

   <section>
    <title>SSH</title>

    <list type="bulleted">
      <item>ssh requires the crypto and public_key applications.</item>
      <item>Supported SSH-version is 2.0 </item>
      <item>Currently supports only a minimum of mac and encryption algorithms i.e.
      hmac-sha1, and aes128-cb and 3des-cbc.</item>
    </list>
 
  </section>
  
  <section>
    <title>COMMON DATA TYPES </title>
    <p>Type definitions that are used more than once in
    this module:</p>
    <p><c>boolean() = true | false </c></p>
    <p><c>string() = list of ASCII characters</c></p>
    <p><c>ssh_daemon_ref() - opaque to the user
    returned by ssh:daemon/[1,2,3]</c></p>
    <p><c>ssh_connection_ref() - opaque to the user
    returned by ssh:connect/3</c></p>
    <p><c>ip_address() - {N1,N2,N3,N4} % IPv4 |
    {K1,K2,K3,K4,K5,K6,K7,K8} % IPv6</c></p>
    <p><c>subsystem_spec() = {subsystem_name(), {channel_callback(), channel_init_args()}} </c></p>  
    <p><c>subsystem_name() = string() </c></p>
    <p><c>channel_callback() = atom() - Name of the erlang module
    implementing the subsystem using the ssh_channel behavior see</c>
    <seealso marker="ssh_channel">ssh_channel(3)</seealso></p>
    <p><c>channel_init_args() = list()</c></p>
 </section>
  
 <funcs>
   
   <func>
     <name>close(ConnectionRef) -> ok </name>
      <fsummary>Closes a ssh connection</fsummary>
      <type>
	<v>ConnectionRef = ssh_connection_ref()</v>
      </type>
      <desc><p>Closes a ssh connection.</p> 
      </desc>
    </func>
    
    <func>
      <name>connect(Host, Port, Options) -> </name>
      <name>connect(Host, Port, Options, Timeout) -> {ok, ssh_connection_ref()}
      | {error, Reason}</name>
      <fsummary>Connect to an ssh server.</fsummary>
      <type>
        <v>Host = string()</v>
	<v>Port = integer()</v>
	<d>The default is <c><![CDATA[22]]></c>, the registered port for SSH.</d>
	<v>Options = [{Option, Value}]</v>
	<v>Timeout = infinity | integer(milliseconds)</v>
      </type>
      <desc>
	<p>Connects to an SSH server. No channel is started this is done
	by calling ssh_connect:session_channel/2.</p>
	<p>Options are:</p>
	<taglist>
          <tag><c><![CDATA[{user_dir, string()}]]></c></tag>
	  <item>
	    <p>Sets the user directory e.i. the directory containing
	    ssh configuration files for the user such as
	    <c><![CDATA[known_hosts]]></c>, <c><![CDATA[id_rsa, id_dsa]]></c> and
	    <c><![CDATA[authorized_key]]></c>. Defaults to the directory normally
	    referred to as <c><![CDATA[~/.ssh]]></c> </p>
	  </item>
	  <tag><c><![CDATA[{dsa_pass_phrase, string()}]]></c></tag>
	  <item>
	    <p>If the user dsa key is protected by a pass phrase it can be
	    supplied with this option.
	    </p>
	  </item>
	  <tag><c><![CDATA[{rsa_pass_phrase, string()}]]></c></tag>
	  <item>
	    <p>If the user rsa key is protected by a pass phrase it can be
	    supplied with this option.
	    </p>
	  </item>
          <tag><c><![CDATA[{silently_accept_hosts, boolean()}]]></c></tag>
	  <item>
	    <p>When true hosts are added to the
	    file <c><![CDATA[known_hosts]]></c> without asking the user.
	    Defaults to false.
	    </p>
	  </item>
	  <tag><c><![CDATA[{user_interaction, boolean()}]]></c></tag>
	  <item>
	    <p>If false disables the client to connect to the server
	    if any user interaction is needed such as accepting that
	    the server will be added to the <c>known_hosts</c> file or
	    supplying a password. Defaults to true.
	    Even if user interaction is allowed it can be
	    suppressed by other options such as silently_accept_hosts and
	    password. Do note that it may not always be desirable to use
	    those options from a security point of view.</p>
	  </item>
	  <tag><c><![CDATA[{public_key_alg, ssh_rsa | ssh_dsa}]]></c></tag>
	  <item>
            <p>Sets the preferred public key algorithm to use for user
	    authentication. If the the preferred algorithm fails of
	    some reason, the other algorithm is tried. The  default is
	    to try <c><![CDATA[ssh_rsa]]></c> first.</p>
	  </item>
	  <tag><c><![CDATA[{pref_public_key_algs, list()}]]></c></tag>
	  <item>
            <p>List of public key algorithms to try to use, ssh_rsa and ssh_dsa available. 
	    Will override <c><![CDATA[{public_key_alg, ssh_rsa | ssh_dsa}]]></c></p>
	  </item>
	  <tag><c><![CDATA[{connect_timeout, timeout()}]]></c></tag>
	  <item>
	    <p>Sets a timeout on the transport layer connection. Defaults to infinity.</p>
	  </item>
	  <tag><c><![CDATA[{user, String}]]></c></tag>
          <item>
	    <p>Provide a user name. If this option is not given, ssh
	    reads from the environment (<c><![CDATA[LOGNAME]]></c> or
	    <c><![CDATA[USER]]></c> on unix,
	    <c><![CDATA[USERNAME]]></c> on Windows).</p>
          </item>
	  <tag><c><![CDATA[{password, string()}]]></c></tag>
          <item>
	    <p>Provide a password for password authentication.  If
	    this option is not given, the user will be asked for a
	    password if the password authentication method is
	    attempted.</p>
          </item>
          <tag><c><![CDATA[{user_auth, Fun/3}]]></c></tag>
          <item>
	    <p>Provide a fun for password authentication. The fun
	    will be called as <c><![CDATA[fun(User, Password, Opts)]]></c> and
	    should return <c><![CDATA[true]]></c> or <c><![CDATA[false]]></c>.</p>
	  </item>
	  <tag><c><![CDATA[{key_cb, atom() = KeyCallbackModule}]]></c></tag>
	  <item>
	    <p>Provide a special call-back module for key handling.
	    The call-back module should be modeled after the
	    <c><![CDATA[ssh_file]]></c> module. The functions that must
	    be exported are:
	    <c><![CDATA[private_host_rsa_key/2]]></c>,
	    <c><![CDATA[private_host_dsa_key/2]]></c>,
	    <c><![CDATA[lookup_host_key/3]]></c> and
	    <c><![CDATA[add_host_key/3]]></c>. This is considered
	    somewhat experimental and will be better documented later on.</p>
	  </item>
	  <tag><c><![CDATA[{quiet_mode, atom() = boolean()}]]></c></tag>
	  <item>
	    <p>If true, the client will not print out anything on authorization.</p>
	  </item>
	  <tag><c><![CDATA[{fd, file_descriptor()}]]></c></tag>
	  <item>
	    <p>Allow an existing file-descriptor to be used
	  (simply passed on to the transport protocol).</p></item>
	  <tag><c><![CDATA[{ip_v6_disabled, boolean()}]]></c></tag>
	  <item>
	    <p>Determines if SSH shall use IPv6 or not.</p>
	  </item>
	  <tag><c><![CDATA[{rekey_limit, integer()}]]></c></tag>
	  <item>
	    <p>Provide, in bytes, when rekeying should be initiated, 
	    defaults to one time each GB and one time per hour.</p>
	  </item>
	</taglist>
      </desc>   
    </func>

    <func>
      <name>connection_info(ConnectionRef, [Option]) ->[{Option, Value}] </name>
      <fsummary> Retrieves information about a connection. </fsummary>
      <type>
        <v>Option = client_version | server_version | peer</v>
	<v>Value = term() </v>
      </type>
      <desc>
        <p> Retrieves information about a connection. 
	</p>
      </desc>
    </func>
    
    <func>
      <name>daemon(Port) -> </name>
      <name>daemon(Port, Options) -> </name>
      <name>daemon(HostAddress, Port, Options) -> ssh_daemon_ref()</name>
      <fsummary>Starts a server listening for SSH connections 
      on the given port.</fsummary>
      <type>
        <v>Port = integer()</v>
	<v>HostAddress = ip_address() | any</v>
	<v>Options = [{Option, Value}]</v>
        <v>Option = atom()</v>
	<v>Value = term()</v>
      </type>
      <desc>
        <p>Starts a server listening for SSH connections on the given port.</p>
      
        <p>Options are:</p>
        <taglist>
	  <tag><c><![CDATA[{subsystems, [subsystem_spec()]]]></c></tag>
	  <item>
	    Provides specifications for handling of subsystems.  The
	    "sftp" subsystem-spec can be retrieved by calling
	    ssh_sftpd:subsystem_spec/1. If the subsystems option in not present
	    the value of <c>[ssh_sftpd:subsystem_spec([])]</c> will be used.
	    It is of course possible to set the option to the empty list
	    if you do not want the daemon to run any subsystems at all.
	  </item>
	  <tag><c><![CDATA[{shell, {Module, Function, Args} | fun(string() = User) - > pid() |
	  fun(string() = User, ip_address() = PeerAddr) -> pid()}]]></c></tag>
	  <item>
	    Defines the read-eval-print loop used when a shell is requested
	    by the client. Example use the
	    erlang shell: <c><![CDATA[{shell, start, []}]]></c> which is
	    the default behavior.
	  </item>
	  <tag><c><![CDATA[{ssh_cli,{channel_callback(), channel_init_args()}}]]></c></tag>
	  <item>
	    Provide your own cli implementation, e.i. a channel callback
	    module that implements a shell and command execution. Note
	    that you may customize the shell read-eval-print loop using the
	    option <c>shell</c> which is much less work than implementing
	    your own cli channel.
	  </item>
	  <tag><c><![CDATA[{user_dir, String}]]></c></tag>
	  <item>
	    <p>Sets the user directory e.i. the directory containing
	    ssh configuration files for the user such as
	    <c><![CDATA[known_hosts]]></c>, <c><![CDATA[id_rsa, id_dsa]]></c> and
	    <c><![CDATA[authorized_key]]></c>. Defaults to the directory normally
	    referred to as <c><![CDATA[~/.ssh]]></c> </p>
	  </item>
          <tag><c><![CDATA[{system_dir, string()}]]></c></tag>
          <item>
            <p>Sets the system directory, containing the host files
            that identifies the host for ssh. The default is
            <c><![CDATA[/etc/ssh]]></c>, note that SSH normally
            requires the host files there to be readable only by
	    root.</p>
	  </item>
	  <tag><c><![CDATA[{auth_methods, string()}]]></c></tag>
	  <item>
	    <p>Comma separated string that determines which authentication methodes that the server
	    should support and in what order they will be tried. Defaults to
	    <c><![CDATA["publickey,keyboard-interactive,password"]]></c></p>
          </item>
	  <tag><c><![CDATA[{user_passwords, [{string() = User, string() = Password}]}]]></c></tag>
	  <item>
            <p>Provide passwords for password authentication.They will
	    be used when someone tries to connect to the server and
	    public key user authentication fails. The option provides
	    a list of valid user names and the corresponding password.
	    </p>
          </item>
          <tag><c><![CDATA[{password, string()}]]></c></tag>
          <item>
            <p>Provide a global password that will authenticate any
              user. From a security perspective this option makes
	      the server very vulnerable.</p>
	  </item>
	  <tag><c><![CDATA[{pwdfun, fun/2}]]></c></tag>
	  <item>
	    <p>Provide a function for password validation. This is called
	      with user and password as strings, and should return
	      <c><![CDATA[true]]></c> if the password is valid and
	      <c><![CDATA[false]]></c> otherwise.</p>
	  </item>
	  <tag><c><![CDATA[{fd, file_descriptor()}]]></c></tag>
	  <item>
	    <p>Allow an existing file-descriptor to be used
	  (simply passed on to the transport protocol).</p></item>
	  <tag><c><![CDATA[{ip_v6_disabled, boolean()}]]></c></tag>
	  <item>
	    <p>Determines if SSH shall use IPv6 or not (only used when 
               HostAddress is set to any).</p></item>
        </taglist>
      </desc>
    </func>

    <func>
      <name>shell(Host) -> </name>
      <name>shell(Host, Option) -> </name>
      <name>shell(Host, Port, Option) -> _</name>
      <fsummary> </fsummary>
      <type>
        <v> Host = string()</v>
	<v> Port = integer()</v>
	<v> Options - see ssh:connect/3</v>
      </type>
      <desc>
        <p>Starts an interactive shell to an SSH server on the
	given <c>Host</c>. The function waits for user input,
	and will not return until the remote shell is ended (e.g. on
	exit from the shell).
	</p>
      </desc>
    </func>

    <func>
      <name>start() -> </name>
      <name>start(Type) -> ok | {error, Reason}</name>
      <fsummary>Starts the Ssh application. </fsummary>
      <type>
        <v>Type =  permanent | transient | temporary</v>
	<v>Reason = term() </v>
      </type>
      <desc>
        <p>Starts the Ssh application. Default type
          is temporary. See also
          <seealso marker="kernel:application">application(3)</seealso>
	  Requires that the crypto application has been started.
	</p>
      </desc>
    </func>

    <func>
      <name>stop() -> ok </name>
      <fsummary>Stops the Ssh application.</fsummary>
      <desc>
        <p>Stops the Ssh application. See also
          <seealso marker="kernel:application">application(3)</seealso></p>
      </desc>
    </func>
    
    <func>
      <name>stop_daemon(DaemonRef) -> </name>
      <name>stop_daemon(Address, Port) -> ok </name>
      <fsummary>Stops the listener and all connections started by 
      the listener.</fsummary>
      <type>
	<v>DaemonRef = ssh_daemon_ref()</v>
	<v>Address = ip_address()</v>
	<v>Port = integer()</v>
      </type>
      <desc>
	<p>Stops the listener and all connections started by 
	the listener.</p>
      </desc>
    </func>

    <func>
      <name>stop_listener(DaemonRef) -> </name>
      <name>stop_listener(Address, Port) -> ok </name>
      <fsummary>Stops the listener, but leaves existing connections started
	by the listener up and running.</fsummary>
      <type>
	<v>DaemonRef = ssh_daemon_ref()</v>
        <v>Address = ip_address()</v>
	<v>Port = integer()</v>
      </type>
      <desc>
	<p>Stops the listener, but leaves existing connections started
	by the listener up and running.</p>
      </desc>
    </func>

  </funcs>
  
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