ARCv2

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lib/Arc/Connection/Client.pod  view on Meta::CPAN

=head1 NAME

Arc::Connection::Client - Client class for ARCv2

=head1 DESCRIPTION

ARC allows non-privileged users to run privileged commands on the server.
The server decides if the user is allowed to run this command through ACL.

This file is a part of the Perl ARCv2 module suite. ARCv2 is a 
rewrite of ARC by R.Toebbicke, CERN, Switzerland in Perl. 

=head1 ABSTRACT

From ARC by R. Toebbicke, modified by me:
User requests are shipped from a client machine to a server using a
SASL-authenticated socket connection. The purpose is to convey
requests such as privileged commands (e.g. AFS, Crontab) to be executed on the
server under appropriate privileges. Given that all privileges are
confined to the server and the server can be programmed as to filter and
check the command to be executed, the client machine can be less trusted
than the server.

Because ARC-v1-Commands are written in perl anyway, implementing the client/server
in perl makes sense. Platform-independence and "easy-to-read" source code are welcome
too. This package provides two perl command line scripts (arcx, arcxd). They can
be used for working with the ARC server from the command line, resp. to start the
server.

=head1 SYNOPSIS

Arc::Connection::Client - Client class for ARCv2

 my $arc = new Arc::Connection::Client(
  server => "hyade11",
  port => 4242,
  timeout => 30,
  loglevel=> 7,
  logdestination => 'stderr',
  service => 'arc',
  sasl_mechanism => undef,
  sasl_cb_user => \&username,
  sasl_cb_auth => \&username,
  sasl_cb_pass => \&password,
 );

 if (my $m = $arc->IsError()) {
  die $m;
 }

 if ($arc->StartSession) {
  $arc->CommandStart("test");
  $arc->CommandWrite("hallo\n");
  if (my $t = $arc->CommandRead()) {
   print $t,"\n"; # should give 'all'
  }
  $arc->CommandEnd();
 }

 sub username
 {
  return $ENV{'USER'};
 }

 sub password
 {
  return <>;
 }


=head1 Class VARIABLES

=head3 PUBLIC MEMBERS

=over 2

=item logdestination I<reimplemented from Arc>

B<Default value>: "stderr"

=item logfileprefix I<reimplemented from Arc>

B<Default value>: "client"

=item port 

B<Description>: Port to connect to

lib/Arc/Connection/Client.pod  view on Meta::CPAN

B<Default value>: 1

=back 

=over 2

=back 

=head3 PRIVATE MEMBERS

=head1 Class METHODS

=head3 PUBLIC METHODS

=over 2

=item CommandEnd (  ) 

B<Description>: end the command on the server side.
Closes the command connection and ends the command.


B<Returns:> true if successful, false if not. (IsError is set appropriatly)


B<Example:>

$arc->CommandEnd();


=item CommandEOF (  ) 

B<Description>: close the write part of the netsock.
This function closes the write-part of the command connection.


B<Returns:> true if successful, false if not. (IsError is set appropriatly)


B<Example:>

last unless $arc->CommandEOF();


=item CommandRead (  ) 

B<Description>: read data from the Command connection.


B<Returns:> if successful the received data is returned, otherwise false.


B<Example:>

while (my $data = $arc->CommandRead()) { ... }


=item CommandStart ( ... (command and its parameters) ) 

B<Description>: start an ARCv2 command
This function starts the given ARCv2 Command and enables the Command* functions.


B<Returns:> true if successful, false if not. (IsError is set appropriatly)


B<Example:>

if ($arc->CommandStart()) { ... }


=item CommandWrite ( ... (data) ) 

B<Description>: write something to the command.
Write something to the standard input of the command started by C<CommandStart>.


B<Returns:> true if successful, false if not. (IsError is set appropriatly)


B<Example:>

last unless $this->CommandWrite();


=item ProcessCommand ( ... (command and its parameters) ) 

B<Description>: process a command.
This function runs a command with STDIN and STDOUT as clients 
in- and output control.


B<Returns:> true if successful, false if not. (IsError is set appropriatly)


B<Example:>

$arc->ProcessCommand("whoami");


=item Quit (  ) 

B<Description>: ends the connection.
Tells the server that we want to end the conversation. (Userlevel)
Protocol command: QUIT\r\n


B<Returns:> always true


B<Example:>

$arc->Quit();


=item StartSession (  ) 

B<Description>: start an ARCv2 session.
This function which will change the status of the connection into a
authenticated status. Users have to call this function
to be able to run ARCv2 commands afterwards.


B<Returns:> true if authentication was successful, otherwise false.


B<Example:>

if ($arc->StartSession()) { .. }


=back 

=over 2

=item clean (  ) I<inherited from Arc::Connection>

=item IsConnected (  ) I<inherited from Arc::Connection>

B<Description>: are we connected?


B<Returns:> true, if the ARCv2 control connection is connected, otherwise false


B<Example:>

last unless $arc->IsConnected;


=back 

=over 2

=item DESTROY (  ) I<inherited from Arc>

B<Description>: Destructor


=item IsError (  ) I<inherited from Arc>

B<Description>: User function to get the error msg.


B<Returns:> the error message if any otherwise undef


B<Example:>

unless (my $err = $arc->IsError()) { .. } else { print STDERR $err; }


=item Log ( $facility, ... (message) ) I<inherited from Arc>

B<Description>: Log function.
Logs messages to 'logdestination' if 'loglevel' is is set appropriatly.
loglevel behaviour has changed in the 1.0 release of ARCv2, the "Arc"-class can export
LOG_AUTH (authentication information), LOG_USER (connection information), LOG_ERR (errors), 

lib/Arc/Connection/Client.pod  view on Meta::CPAN

B<Example:>

while (my $cmd = $this->_RecvCommand() && $this->_ProcessLine($cmd)) {}


=item _ReadWriteBinary ( *locfdin, *locfdout ) I<inherited from Arc::Connection>

B<Description>: function for reading and writing on the command connection.
This function is always used by the C<Arc::Connection::Server> to handle 
command data. When calling the C<ProcessCommand> from C<Arc::Connection::Client> 
this function is also used.
Data is read from the local socket resp. pipe and is written encrypted 
to the network socket. The other side reads the data from network socket, 
decrypts it and writes it to its local socket. This function behaves differently on 
client and server sides, when the local or network socket is closed.


B<Returns:> always true


B<Example:>

$this->ReadWriteBinary(*STDIN,*STDOUT);


=item _RecvCommand (  ) I<inherited from Arc::Connection>

B<Description>: receives an ARCv2 Command. (protocol)
This function gets a line from C<_RecvLine> and extracts the ARCv2 command and
the optional command parameter C<_cmdparameter>.


B<Returns:> ARCv2 command and true if everything works fine, otherwise false


B<Example:>

while (my $cmd = $this->_RecvCommand()) { ... }


=item _RecvLine (  ) I<inherited from Arc::Connection>

B<Description>: receive a line (command). (protocol)
This function receives data from the ARCv2 connection and
fills the internal C<__linequeue> and C<__partial>. It returns 
a line from the internal buffer if there is any. It also handles
timeouts and "connection closed by foreign host"'s.


B<Returns:> true (and the line) if everything worked fine, otherwise false (undef)


B<Example:>

if (my $line = $this->_RecvLine()) { ... }


=item _Sasl ( $saslstr ) I<inherited from Arc::Connection>

B<Description>: send the ARCv2 SASL command. (protocol)
This function encodes the output from sasl_*_start and sasl_*_step with Base-64 and sends
it to the other side


B<Returns:> true if successful, otherwise false


B<Example:>

$this->_Sasl($sasl->client_start());


=item _SendCommand ( $cmd, $parameter ) I<inherited from Arc::Connection>

B<Description>: send a command. (protocol)  
Send a command to the ARCv2 socket.


B<Returns:> true if successful, otherwise false


B<Example:>

$this->_SendCommand("CMDPASV",$consock->sockhost.':'.$consock->sockport);


=item _SendLine ( ... (line) ) I<inherited from Arc::Connection>

B<Description>: send a line. (protocol)
This function sends a command line to the ARCv2 socket.


B<Returns:> true if writing has succeeded, otherwise false.


B<Example:>

$this->_SendLine($cmd,"test"); 


=back 

=over 2

=item _Debug ( ... (message) ) I<inherited from Arc>

B<Description>: Debug function.
Logs messages with "DEBUG" 


B<Returns:> always false


B<Example:>

$this->_Debug("hello","world"); # message will be "hello world"


=item _SetError ( ... (message)  ) I<inherited from Arc>

B<Description>: SetError function.
This function prepends the error message (@_) to an existing error message (if any) and
logs the message with LOG_ERR facility.
Use this function for setting an error from class level. Users should use IsError 
to get the message if a function failed.


B<Returns:> always false