[X2Go-Commits] page changed: wiki:advanced:x2gobroker:plaintexprotocol
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Old Revision: http://wiki.x2go.org/doku.php/wiki:advanced:x2gobroker:plaintexprotocol?rev=1364322544
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@@ -1,351 +1 @@
- ====== X2Go Session Broker Protocol: Plain Text ======
-
- //Client implementations: X2Go Client (since 3.x.y.z), Python X2Go (planned for 0.6.x.y)//
-
- The X2Go project offers a [[http://code.x2go.org/gitweb?p=x2gobroker.git;a=summary|public X2Go Session Broker implementation]]. However, there also exist several other implementations in large-scale production deployments.
-
- In theory, you can implement your own X2Go Session Broker by meeting some basic
demands.
-
- This documentation explains a minimal broker implementation along the code of a Perl script.
-
- In this example, the X2Go Session Broker consists of two components:
-
- - ''x2gobroker.pm'' (a Perl module, the broker backend)
- - the broker frontend (either of the below):
- - ''x2gobroker.cgi'' (a CGI script written in Perl -> HTTP based broker)
- - ''x2gobroker'' (a command line script written in Perl -> SSH based broker)
-
- ===== X2Go Session Broker: The Backend ====
-
- The package ''x2gobroker.pm'' can be considered as the broker backend. It has to implement two functions at minimal (names are arbitrary):
-
- * listProfiles
- * selectProfile
-
- If you want to use authentication with your session broker, the broker backend also has to provide a function called
-
- * checkAccess
-
- A very small and simple broker backend can look like this:
-
- <code>
- package x2gobroker;
- use strict;
- use base 'Exporter';
- our @EXPORT =
('checkAccess', 'listSessions', 'selectSession');
-
- #we have two sessions
- sub selectSession
- {
- my ($user, $sid)=@_;
- if($sid eq "123456789")
- {
- print "SERVER:x2goserver.org:22\n";
- }
- if($sid eq "abcdefg")
- {
- print "SERVER:x2gotest.org:22\n";
- }
- }
- #do not check authentication data,
- #return true on any
- #combination of username/password
- sub checkAccess
- {
- return 1;
- }
- #configuration for two sessions
- sub listSessions
- {
- my $user=shift;
- print "START_USER_SESSIONS<br>
- <br>[123456789]<br>
- name=X2Go Session<br>
- command=KDE<br>
- host=x2goserver.org<br>
- user=$user<br>
- <br>[abcdefg]<br>
- name= Test X2Go Session 2<br>
- command=startxfce4<br>
- host=x2gotest.org<br>
- user=test<br>
- END_USER_SESSIONS<br>";
- }
-
- 1;
- </code>
-
-
- ==== CLient side ====
-
- FIXME -> TODO
-
- X2Go client can access a broker module using one of two broker methods.
- Via HTTP(S) or SSH.
- HTTP(S) broker is usually CGI
script, which can look like:
- <code>
- #!/usr/bin/perl
-
- use strict;
- use CGI;
- use CGI::Carp qw(fatalsToBrowser);
- use lib "/usr/lib/x2go";
- use x2gobroker;
- my $cgi = new CGI;
-
- my @formValues = $cgi->param();
-
- print $cgi->header(-type =>'text/html',
- -expires =>'+1h'),
- $cgi->start_html( -title =>'X2Go Broker',
- -author =>'team at obviously-nice.de',
- -base =>'true',
- -meta =>{'keywords' =>'x2go',
- 'description'=>'X2Go Broker'});
-
- if (!checkAccess($cgi->param('user'), $cgi->param('password'),
- $cgi->param('authid')) == 1)
- {
- printNoAccess();
- print $cgi->end_html();
- exit (0);
- }
-
- print $cgi->start_form(),
- $cgi->strong('Access granted');
-
- if ($cgi->param('task') eq 'listsessions')
- {
- listSessions($cgi->param('user'));
- }
-
- if ($cgi->param('task') eq 'selectsession')
- {
-
selectSession($cgi->param('user'), $cgi->param('sid'));
- }
- $cgi->hr(),
- $cgi->end_form();
- print $cgi->end_html();
-
- sub printNoAccess
- {
- print $cgi->start_form(),
- $cgi->hr(),
- $cgi->strong('Access denied'),
- $cgi->end_form();
- }
- </code>
-
- SSH broker can be a simple Perl script, which can look like:
- <code>
- #!/usr/bin/perl
- use strict;
- use lib "/usr/lib/x2go";
- use x2gobroker;
- use Getopt::Long;
-
- my $user=getlogin();
- my $authid;
- my $task;
- my $sid;
-
- #you don't need to check password on ssh brocker.
- #But possible you steel want to check auth id
- #if (!checkAccess($user, $authid) == 1)
- #{
- # printNoAccess();
- # exit (0);
- #}
- print "Access granted\n";
- GetOptions('task=s' => \$task,
- 'sid=s' => \$sid);
- if(! $task)
- {
- die "parameter --task is required";
- }
- if ($task eq 'listsessions')
- {
- listSessions($user);
- }
- elsif ($task eq 'selectsession')
- {
-
if(! $sid)
- {
- die "parameter --sid is required";
- }
- selectSession($user, $sid);
- }
- else
- {
- die "task \"".$task."\" not implemented on broker\n";
- }
- sub printNoAccess
- {
- die 'Access denied';
- }
- </code>
-
- 2. How X2Go broker work
-
- 2.1. Authentication
-
- The X2Go client can use different methods of authentication. On HTTP(S)
- broker it could be username and password. On SSH broker a SSH key
- authentication can also be used. With both types of broker you can
- verify additional parameter "authid". It is a user defined string which
- is saved in file. Path to file can be specified as X2Go Client command
- line option "--auth-id". You can configure your broker not to check user
- data as it shown in example above. In such case function checkAccess
- should always return 1. In example of SSH-Broker this function is not
- called at all. The broker just print "Access granted" to let X2Go Client
- know, that authentication is successful.
In some setups can make sense
- to give access to broker without authentication. For example in LAN if
- broker only serve as load balancer for X2Go Servers.
-
- 2.2. List of predefined X2Go sessions
-
- After successful authentication on broker, X2Go Client will request list
- of predefined X2Go Sessions. This list look just the same as session
- file of X2Go Client. The function, that send X2Go sessions to Client
- look like:
- <code>
- sub listSessions
- {
- print "START_USER_SESSIONS<br>
- <br>[ <session 1> ]<br>
- option1=value1<br>
- ....
- optionN=valueN<br>
- <br>[ <session 2> ]<br>
- option1=value1<br>
- ....
- optionN=valueN<br>
- END_USER_SESSIONS<br>";
- }
- </code>
- The options are the same as in X2Go Client configuration file. There is
- only a difference in parameters "host" and "key". And there are two
- parameters which are not supported in configuration file "status" and
- "usebrokerpass".
- The "host" parameter it is not necessary a hostname of X2Go
server. The
- actual address of a server will be provided after session selection. It
- can make sense in a case of load balancing. The best server will be
- chosen after selection and sent to client.
- The "key" parameter is also ignored. Key can be provided to client after
- selection of session too. However, you can set this parameter with some
- value to inform the Client, that passwordless authentication should be
- tried, for example: "key=will be provided later".
- Parameter "usebrokerpass" say, that a user password for this session
- should not be asked, but broker password should be used instead. It can
- be useful if the broker and X2Go Server using same authentication server
- and there is no need to ask the same password twice. It is not
- recommended to use such authentication with HTTP Broker without SSL
- encryption.
- Parameter "status" can be one of two values "S" or "R". It can be used
- to say X2Go Client that an instance (or instances) of this session
- already
running or are suspended on server. X2Go Client will display the
- status on the Session button.
-
- 2.3. Selecting a session
-
- When predefined sessions are listed in X2Go Client, user can choose a
- session from sessions list. The id of chosen session will be sent to
- broker and broker send a connection data back to client. It is
- responsibility of function "selectSession":
- <code>
- sub selectSession
- {
- my ($user, $sid)=@_;
- if($sid eq "123456789")
- {
- print "SERVER:x2goserver.org:22\n";
- }
- }
- </code>
-
- This function send a server address and SSH port for X2Go connection. If
- no other data are specified a new X2Go session will be created.
- Broker can also send to Client information, that suspended session
- should be resumed. In this case broker should also send a session data
- to Client:
- <code>
- sub selectSession
- {
- my ($user, $sid)=@_;
- if($sid eq "123456789")
- {
- print "SERVER:phoca:22\n";
- print
-
"SESSION_INFO:12542|ncryer-53-1348753256_stDstartxfce4_dp24|53|debian|S|2012-09-27T06:40:57|7db77095d8a782f479d509d96f2e3261|188.195.168.12|30004|30005|2012-09-27T06:41:28|ncryer|285|30006|\n";
- }
- </code>
- Broker can get this data from session database or by executing
- "x2golistsessions $user" on X2Go server. If X2Go Client running in
- broker mode, it will not verify if there are existing sessions on X2Go
- server. It is a responsibility of X2Go Broker. Broker should also
- suspend session before providing session data to client if session is
- running.
-
- The broker can also provide a SSH Key to client:
- <code>
- sub selectSession
- {
- my ($user, $sid)=@_;
- if($sid eq "123456789")
- {
- print "SERVER:phoca:22\n";
- print "-----BEGIN DSA PRIVATE KEY-----
- Proc-Type: 4,ENCRYPTED
- DEK-Info: AES-128-CBC,XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
-
- XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
-
yX7XLwCszCLM1FCYpdIGmM98vuHVcpNlVUBVgNcTxE1XCCnPZPjUXiNnUZPk1lme
- XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
- o1q7Q1YmH43qI18lifjUhGZUTYWKQSsj2Am9bnjqaveV2aMEWymC8J9aJOYLpVZG
- XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
- G1DwWnSRgyJaxRm4Ik0/kh78ioUfkVerXaCf2OKCMyiZBWcsNfvQwDa9MBrZ4rYW
- XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
- VR60OGB7dHy+7ozqkjzuX+uB04GIqPJwG797i26Bo4v7uhbALjMa5qsObqXIPM1S
- XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
- XXXXXXXXXXXXXXXX==
- -----END DSA PRIVATE KEY-----";
- }
- }
- </code>
- It can be useful in some cases. It is recommended to transfer such keys
- only over encrypted channels. It is also recommended to transfer only
- temporary keys, which should be removed from known_hosts after
- authorization on X2Go server.
-
- 3. Configuring X2Go client for connection to broker
-
- There are several command line parameters to configure X2Go Client for
- use with
broker:
-
- --broker-name=<name>
- Name of broker to display in X2Go client. This parameter is optional
-
- --broker-url=<protocol>://[username@]<host>[:port]/path
- URL of broker. Protocol is "http", "https" or "ssh". You can specify an
- username in URL. In this case it will be pasted in authorization dialog
- of X2Go Client. Examples of URL:
- --broker-url=https://x2gobroker.org/cgi-bin/x2gobroker.cgi
- --broker-url=ssh://user@x2gobroker.org:22/usr/lib/x2go/x2gobroker.pl
-
- --broker-ssh-key=<path to key>
- Path to SSH key to use for authorization on broker. This parameter is
- valid only for SSH broker.
-
- --broker-autologin
- Use default SSH key or SSH agent for authorization on broker. This
- parameter is valid only for SSH broker.
-
- --broker-noauth
- Do not ask for user credentials for broker authorizations. This can be
- useful if you using HTTP(S) broker without authentication. Username will
- be sent to broker if it specified in broker URL. This option is valid
-
only for HTTP(S) broker.
-
-
-
--
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