=head1 NAME

Authen::SASL::XS	- XS code to glue Perl SASL to Cyrus SASL

=head1 SYNOPSIS

  use Authen::SASL;

  my $sasl = Authen::SASL->new(
         mechanism => 'NAME',
         callback => { NAME => VALUE, NAME => VALUE, ... },
  );

  my $conn = $sasl->client_new(<service>, <server>, <iplocalport>, <ipremoteport>);

  my $conn = $sasl->server_new(<service>, <host>, <iplocalport>, <ipremoteport>);

=head1 DESCRIPTION

SASL is a generic mechanism for authentication used by several
network protocols. B<Authen::SASL::XS> provides an implementation
framework that all protocols should be able to share.

The XS framework makes calls into the existing libsasl.so resp. libsasl2
shared library to perform SASL client connection functionality, including
loading existing shared library mechanisms.

=head1 CONSTRUCTOR

The constructor may be called with or without arguments. Passing arguments is
just a short cut to calling the C<mechanism> and C<callback> methods.

You have to use the C<Authen::SASL> new-constructor to create a SASL object.
The C<Authen::SASL> object then holds all necessary variables and callbacks, which
you gave when creating the object.
C<client_new> and C<server_new> will retrieve needed information from this
object.

=pod

=head1 CALLBACKS

Callbacks are very important. It depends on the mechanism which callbacks
have to be set. It is not a failure to set callbacks even they aren't used.
(e.g. password-callback when using GSSAPI or KERBEROS_V4)

The Cyrus-SASL library uses callbacks when the application
needs some information. Common reasons are getting
usernames and passwords.

Authen::SASL::XS allows Cyrus-SASL to use perl-variables and perl-subs
as callback-targets.

Currently Authen::SASL::XS supports the following Callback types:
(for a more detailed description on what the callback type is used for
see the respective man pages)

B<Remark>: All callbacks, which have to return some values (e.g.: **result in
C<sasl_getsimple_t>) do this by returning the value(s). See example below.

=over 4

=item user (client)

=item auth (client)

=item language (client)

This callbacks represent the C<sasl_getsimple_t> from the library.

Input: none

Output: C<username>, C<authname> or C<language>

=item password (client)

=item pass (client)

This callbacks represent the C<sasl_getsecret_t> from the library.

Input: none

Output: C<password>

=item realm <client>

This callback represents the C<sasl_getrealm_t> from the library.

Input: a list of available realms

Output: the chosen realm

(This has nothing to do with GSSAPI or KERBEROS_V4 realm).

=item checkpass (server, SASL v2 only)

This callback represents the C<sasl_server_userdb_checkpass_t> from the
library.

Input: C<username>, C<password>

Output: true or false


=item getsecret (server, SASL v1 only)

This callback represents the C<sasl_server_getsecret_t> from the library. Sasl
will check if the passwords are matching.

Input: C<mechanism>, C<username>, C<default_realm>

Output: C<secret_phrase (password)>

B<Remark>: Programmers that are using should specify both callbacks (getsecret and checkpass).
Then, depending on you Cyrus SASL library either the one or the other is called. Cyrus SASL v1
ignores checkpass and Cyrus SASL v2 ignores getsecret.

=item putsecret (SASL v1) and setpass (SASL v2)

are currently not supported (and won't be, unless someone needs it).

=item canonuser (server/client in SASL v2, server only in SASL v1)

This callback name represents the C<sasl_canon_user_t> from the library.

Input: C<Type of principal>, C<principal>, C<userrealm> and maximal allowed length of the output.

Output: canonicalised C<principal>

C<Type of principal> is "AUTHID" for Authentication ID or "AUTHZID"
for Authorisation ID.

B<Remark>: This callback is ideal to get the username of the user using your service.
If C<Authen::SASL::XS> is linked to Cyrus SASL v1, which doesn't have a canonuser callback,
it will simulate this callback by using the authorize callback internally. Don't worry, the
authorize callback is available anyway.

=item authorize (server)

This callback represents the C<sasl_authorize_t> from the library.

Input: C<authenticated_username>, C<requested_username>, (C<default_realm> SASL v2 only)

Output: C<canonicalised_username> SASL v1 resp. true or false when using SASL v2 lib
There is something TODO, I think.

=item setpass (server, SASL v2 only)

This callback represents the C<sasl_server_userdb_setpass_t> from the library.

Input: C<username>, C<new_password>, C<flags> (0x01 CREATE, 0x02 DISABLE,
0x04 NOPLAIN)

Out: true or false

=back

=head2 Ways to pass a callback

Authen::SASL::XS supports three different ways to pass a callback

=over 4

=item CODEREF

If the value passed is a code reference then, when needed, it will be called.

=item ARRAYREF

If the value passed is an array reference, the first element in the array
must be a code reference. When the callback is called the code reference
will be called with the value from the array passed after.

=item SCALAR
All other values passed will be returned directly to the SASL library
as the answer to the callback.

=back

=head2 Example of setting callbacks

$sasl = new Authen::SASL (
  mechanism => "PLAIN",
    callback => {
      # Scalar
      user => "mannfred",
      pass => $password,
      language => 1,

      # Coderef
      auth => sub { return "klaus", }
      realm => \&getrealm,

      # Arrayref
      canonuser => [ \&canon, $self ],
   }
);

The last example is ideal for using object methods as callback functions.
Then you can do something like this:

sub canon
{
  my ($this,$type,$realm,$maxlen,$user) = @_;
  $this->{_username} = $user if ($type eq "AUTHID");
  return $user;
}

=head1 Authen::SASL::XS METHODS

=over 4

=item server_new ( SERVICE , HOST = "" , IPLOCALPORT , IPREMOTEPORT )

Constructor for creating server-side sasl contexts.

Creates and returns a new connection object blessed into Authen::SASL::XS.
It is on that returned reference that the following methods are available.
The SERVICE is the name of the service being implemented, which may be used
by the underlying mechanism. An example service therefore is "ldap".

=pod

=item client_new ( SERVICE , HOST , IPLOCALPORT , IPREMOTEPORT )

Constructor for creating server-side sasl contexts.

Creates and returns a new connection object blessed into Authen::SASL::XS.
It is on that returned reference that the following methods are available.
The SERVICE is the name of the service being implemented, which may be used
by the underlying mechanism. An example service is "ldap". The HOST is the
name of the server being contacted, which may also be used
by the underlying mechanism.

=back

B<Remark>:
This and the C<server_new> function are called by L<Authen::SASL> when using
its C<*_new> function. Since the user has to use Authen::SASL anyway, normally
it is not necessary to call this function directly.

IPLOCALPORT and IPREMOTEPORT arguments are only available, when ASC is
linked against Cyrus SASL 2.x. This arguments are needed for KERBEROS_V4
and CS 2.x on the server side. Don't know if it necessary for the client
side. Format of this arguments in an IPv4 environment should be: a.b.c.d;port.
See sasl_server_new(3) for details.

=over 4

See SYNOPSIS for an example.

=pod

=item server_start ( CHALLENGE )

C<server_start> begins the authentication using the chosen mechanism.
If the mechanism is not supported by the installed Cyrus-SASL it fails.
Because for some mechanisms the client has to start the negotiation,
you can give the client challenge as a parameter.

=pod

=item client_start ( )

The initial step to be performed. Returns the initial value to pass to the server.
Client has to start the negotiation always.

=pod

=item server_step ( CHALLENGE )

C<server_step> performs the next step in the negotiation process. The
first parameter you give is the clients challenge/response.

=pod

=item client_step ( CHALLENGE )

=back

B<Remark>:
C<client_start>, C<client_step>, C<server_start> and C<server_step>
will return the respective sasl response or undef. The returned value
says nothing about the current negotiation status. It is absolutely possible
that one of these functions return undef and everything is fine for SASL,
there is only another step needed.

Therefore you have to check C<need_step> and C<code> during negotiation.

See example below.

=over 4

=pod

=item listmech( START , SEPARATOR , END )

C<listmech> returns a string containing all mechanisms allowed for the user
set by C<user>. START is the token which will be put at the beginning of the
string, SEPARATOR is the token which will be used to separate the mechanisms
and END is the token which will be put at the end of returned string.

=pod

=item setpass(user, newpassword, oldpassword, flags)

=item checkpass(user, password)

C<setpass> and C<checkpass> is only available when using Cyrus-SASL 2.x library.

C<setpass> sets a new password (depends on the mechanism if the setpass callback
is called). C<checkpass> checks a password for the user (calls the checkpass
callback).

For both function see the man pages of the Cyrus SASL for a detailed description.

Both functions return true on success, false otherwise.

=pod

=item global_listmech ( )

C<global_listmech> is only available when using Cyrus-SASL 2.x library.

It returns an array with all mechanisms loaded by the library.

=pod

=item encode ( STRING )

=item decode ( STRING )

Cyrus-SASL developers suggest using the C<encode> and C<decode> functions
for every traffic which will run over the network after a successful authentication

C<encode> returns the encrypted string generated from STRING.
C<decode> returns the decrypted string generated from STRING.

It depends on the used mechanism how secure the encryption will be.

=pod

=item error ( )

C<error> returns an array with all known error messages.
Basicly the sasl_errstring function is called with the current error_code.
When using Cyrus-SASL 2.x library also the string returned by sasl_errdetail
is given back. Additionally the special Authen::SASL::XS advise is
returned if set.
After calling the C<error> function, the error code and the special advice
are thrown away.

=pod

=item code ( )

C<code> returns the current Cyrus-SASL error code.

=pod

=item mechanism ( )

C<mechanism> returns the current used authentication mechanism.

=pod

=item need_step ( )

C<need_step> returns true if another step is need by the SASL library. Otherwise
false is returned. You can also use C<code == 1> but it looks smarter I think.
That's why we all using perl, eh?

=pod

=back

=head1 EXAMPLE

=head2 Server-side

 # The example uses Cyrus-SASL v2
 # Set the SASL_PATH to the location of the SASL-Plugins
 # default is /usr/lib/sasl2
 $ENV{'SASL_PATH'} = "/opt/products/sasl/2.1.15/lib/sasl2";

 #
 my $sasl = Authen::SASL->new (
    mechanism => "PLAIN",
    callback => {
      checkpass => \&checkpass,
      canonuser => \&canonuser,
    }
 );

 # Creating the Authen::SASL::XS object
 my $conn = $sasl->server_new("service","","ip;port local","ip;port remote");

 # Clients first string (maybe "", depends on mechanism)
 # Client has to start always
 sendreply( $conn->server_start( &getreply() ) );

 while ($conn->need_step) {
    sendreply( $conn->server_step( &getreply() ) );
 }

 if ($conn->code == 0) {
    print "Negotiation succeeded.\n";
 } else {
    print "Negotiation failed.\n";
 }

=head2 Client-side

 # The example uses Cyrus-SASL v2
 # Set the SASL_PATH to the location of the SASL-Plugins
 # default is /usr/lib/sasl2
 $ENV{'SASL_PATH'} = "/opt/products/sasl/2.1.15/lib/sasl2";

 #
 my $sasl = Authen::SASL->new (
    mechanism => "PLAIN",
    callback => {
      user => \&getusername,
      pass => \&getpassword,
    }
 );

 # Creating the Authen::SASL::XS object
 my $conn = $sasl->client_new("service", "hostname.domain.tld");

 # Client begins always
 sendreply($conn->client_start());

 while ($conn->need_step) {
    sendreply($conn->client_step( &getreply() ) );
 }

 if ($conn->code == 0) {
    print STDERR "Negotiation succeeded.\n";
 } else {
    print STDERR "Negotiation failed.\n";
 }

See t/plain.t for working script.

=head1 TESTING

I tested ASC (server and client) with the following mechanisms:

=over 4

=item GSSAPI

Don't forget to create keytab. Non-root keytabs can be specify through $ENV{'KRB5_KTNAME'} (Heimdal >= 0.6, MIT).

=item KERBEROS_V4

Available since 0.10, you have to add IPLOCALPORT and IPREMOTEPORT to *_new functions.

=item  PLAIN

=back

=head1 SEE ALSO

L<Authen::SASL>

man pages for sasl_* library functions.

=head1 AUTHOR

Originally written by Mark Adamson <mark@nb.net>

Cyrus-SASL 2.x support by Leif Johansson

Glue for server_* and many other structural improvements by Patrick Boettcher <patrick.boettcher@desy.de>

Please report any bugs, or post any suggestions, to the authors.

=head1 THANKS

 - Guillaume Filion for testing the server part and for giving hints about
   some bugs (documentation).
 - Wolfgang Friebel for bother around with rpm building of test releases.

=head1 COPYRIGHT

Copyright (c) 2003-5 Patrick Boettcher, DESY Zeuthen. All rights reserved.
Copyright (c) 2003 Carnegie Mellon University. All rights reserved.

This program is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.