=head1 NAME

Net::LDAP::FAQ - Frequently Asked Questions about Net::LDAP

=head1 SYNOPSIS

 perldoc Net::LDAP::FAQ

=head1 DESCRIPTION

This document serves to answer the most frequently asked questions on both the
perl-ldap Mailing List and those sent to Graham Barr.

The latest version of this FAQ can be found at 

 http://ldap.perl.org/FAQ.html

=head1 GENERAL

=head2 What is perl-ldap ?

perl-ldap is the distribution name. The perl-ldap distribution contains
the Net::LDAP modules.

=head2 Why another perl LDAP implementation ?

perl-ldap's goal is to be as portable as possible. It does this by
being implemented completely in perl. So basically anywhere that perl
runs perl-ldap will run. This is not true for other implementations
which require a C compiler.

=head2 Where can I get it ?

Perl-ldap is available from CPAN. You will find it in the
authors/id/GBARR directory. Alternatively you can download
the latest version from 

 http://www.cpan.org/search?dist=perl-ldap

B<WARNING:>  The perl-ldap module is stored on CPAN as a *.gz file.
Netscape on Windows systems sometimes has a problem storing the module
with the correct name, it will replace the *.tar.gz with *_tar.tar.
To correct the problem, with the pointer on the link, do a right click
and then select B<save link as> to save the file with the correct file
name.

=head2 Is there a web page for perl-ldap ?

Yes there is at http://ldap.perl.org/

=head2 Is there a mailing list ?

Yes there is at perl-ldap@perl.org

You can subscribe to this list by mailing perl-ldap-subscribe@perl.org

=head2 Is the mailing list archived ?

Yes, at http://nntp.perl.org/group/perl.ldap

Archives with messages before we switched to using perl.org can be
found at

 http://marc.theaimsgroup.com/?l=perl-ldap-dev

There is also an archive of the perl-ldap mailing list at

 http://www.xray.mpe.mpg.de/mailing-lists/perl-ldap/

which also has messages from before the move.

=head2 Is there any online documentation ?

Yes. perl-ldap has online documentation at

 http://ldap.perl.org/ 

which will have the latest documentation available.

=head2 Is there a public CVS repository ?

No, but there is a public SVN repository at

 http://svn.mutatus.co.uk

=head2 Can I get perl-ldap from the public SVN repository?

Yes, any one can pull perl-ldap from the public SVN repository
on perl.ldap.org.

There are several ways this can be done.

=over 4

=item Web

You can download it from CPAN by following the release link:  

The 2 lines in the following example should be put together as 
one continuous line.  Example;

 http://search.cpan.org/CPAN/authors/id/G/GB/GBARR/perl-ldap-0.33.tar.gz

B<WARNING:>  The perl-ldap module is stored on CPAN as a *.gz file.
Netscape on Windows systems sometimes has a problem storing the module
with the correct name, it will replace the *.tar.gz with *_tar.tar.
To correct the problem, with the pointer on the link, do a right click
and then select B<save link as> to save the file with the correct file
name.

=item SVN

You can download latest development version of perl-ldap from
svn.mutatus.co.uk by executing a anonymous SVN "checkout" command.

The 2 lines in the following example should be put together as 
one continuous line.  Example;

 svn co http://svn.mutatus.co.uk/repos/perl-ldap/trunk

=item Web page

Most of the time there is a URL link on the perl-ldap 
home page on ldap.perl.org that points to the latest released
version of perl-ldap.  Due to the fact that humans must
update the web page to point to a new release it sometimes does
not get updated as quickly as it should.

B<WARNING:>  The perl-ldap module is stored on CPAN as a *.gz file.
Netscape on Windows systems sometimes has a problem storing the module
with the correct name, it will replace the *.tar.gz with *_tar.tar.
To correct the problem, with the pointer on the link, do a right click
and then select B<save link as> to save the file with the correct file
name.

=back

=head2 What is SVN.

"SVN" is an abbreviation for "Subversion" (see http://subversion.tigris.org).
Subversion is a "Source Control" or "Revision Control" tool
designed to keep track of source changes made by groups of
developers working on the same files, allowing them to
stay in sync with each other as each individual chooses.

=head1 LDAP AND DIRECTORY TERMINOLOGY.

In order to help the user understand the perl-ldap module better
some key LDAP terminology is defined here.

=head2 What is a directory.

A directory is a special purpose hierarchical database that usually
contains typed information such as text strings, binary data, or X.509
certificates.

=head2 What is LDAP.

LDAP stands for Lightweight Directory Access Protocol.
The word I<Protocol> is the key word in the definition given in
the preceding sentence, LDAP is I<NOT> hardware or software.
It is a protocol that defines how a client and server will
communicate with one another.

The Lightweight Directory Access Protocol is defined in a series of
Requests For Comments, better known as RFCs. The RFCs can be found on
the Internet at http://www.ietf.org/ (the master repository) and many
other places. There's a link to all the LDAP-related RFCs at
Perl-LDAP's web site, http://ldap.perl.org/rfc.html. Some of the more
important RFC numbers are RFC 451i0 - 4519 for LDAP (previously called
LDAPv3) and the historic RFC 1777 for LDAPv2.

=head2 What is a LDAP Directory.

In the strictest terms of the definition there is no such thing as a
LDAP directory.  To be practical about this situation every day
directory professionals refer to their directory as " a LDAP
directory" because it is easy to say and it does convey the type of
protocol used to communicate with their directory.  Using this
definition a LDAP directory is a directory whose server software
conforms to the Lightweight Directory Access Protocol when
communicating with a client.

=head2 What is an Entry.

The traditional directory definition of a directory object 
is called an Entry. Entries are composed of attributes that
contain the information to be recorded about the object.

(An entry in LDAP is somewhat analogous to a record in a table in an
SQL database, but don't get too hung up about this analogy!)

Entries are held in an upside-down tree structure. Entries can
therefore contain subordinate entries, and entries B<must> have one
direct superior entry.

Entries with subordinate entries are called 'non-leaf' entries.

Entries without subordinate entries are called 'leaf' entries.

An entry's direct superior entry is called the entry's 'parent'.

'Non-leaf' entries are also said to have 'child' entries.

=head2 What is an attribute.

The entry(s) in a directory are composed of attributes that contain
information about the object.  Each attribute has a type
and can contain one or more values.  

For example:

  cn=Road Runner

is an attribute with a type named "cn", and one value.

Each attribute is described by a 'syntax' which defines what kind of
information can be stored in the attributes values.  Trying to store a
value that doesn't conform to the attribute's syntax will result in an
error.

For example:

  jpegPhoto=unknown

is not permitted by the directory, because jpegPhotos may only contain
JPEG-formatted images.

Most syntaxes used in LDAP however describe text strings rather than
binary objects (like JPEGs or certificates.)

In LDAPv3 most of these syntaxes support Unicode encoded using
UTF-8. Because the Net::LDAP modules do not change the strings that
you pass in as attribute values (they get sent to the LDAP server
as-is) to use accented characters you simply need to encode your
strings in UTF-8. There are modules on CPAN that will help you here.

Note that LDAPv2 servers used something called T.61 instead of Unicode
and UTF-8. Most servers do not implement T.61 correctly, and it is
recommended that you use LDAPv3 instead.

Attributes may also be searched.  The algorithms used to perform
different kinds of searches are described by the attribute's 'matching
rules'.  Some matching rules are case-sensitive and some are
case-insensitive, for example.  Sometimes matching rules aren't
defined for a particular attribute: there's no way to search for
jpegPhotos that contain a substring!

You can examine all of a server's attribute definitions by reading the
schema from the server.

=head2 What is an object class.

An object class is the name associated with a group of attributes that
B<must> be present in an entry, and the group of attributes that
B<may> also be present in an entry.

Object classes may be derived (subclassed) from other object classes.
For example the widely used 'inetOrgPerson' object class is derived
from 'organizationalPerson', which is itself derived from 'person'
which is itself derived from 'top'.

Every entry has an attribute called 'objectClass' that lists all the
names of object classes (and their superclasses) being used with the
entry.

You can examine all of a server's objectclass definitions by reading
the schema from the server.

=head2 What is a Distinguished Name (DN).

Every entry in a directory has a Distinguished Name, or DN.  It is a
unique Entry identifier throughout the complete directory.  No two
Entries can have the same DN within the same directory.

Examples of DNs:

 cn=Road Runner, ou=bird, dc=cartoon, dc=com
 ou=bird, dc=cartoon, dc=com
 dc=cartoon, dc=com
 dc=com

=head2 What is a Relative Distinguished Name.

Every DN is made up of a sequence of Relative Distinguished Names, or
RDNs.  The sequences of RDNs are separated by commas (,). In LDAPv2
semi-colons (;) were also allowed.  There can be more than one
identical RDN in a directory, but they must have different parent
entries.

Technically, an RDN contains attribute-value assertions, or AVAs. When
an AVA is written down, the attribute name is separated from the
attribute value with an equals (=) sign.

Example of a DN: 

 cn=Road Runner,ou=bird,dc=cartoon,dc=com

 RDNs of the proceeding DN: 
 RDN => cn=Road Runner
 RDN => ou=bird
 RDN => dc=cartoon
 RDN => dc=com

RDNs can contain multiple attributes, though this is somewhat
ususual. They are called multi-AVA RDNs, and each AVA is separated in
the RDN from the others with a plus sign (+).

Example of a DN with a multi-AVA RDN:

 cn=Road Runner+l=Arizona,ou=bird,dc=cartoon,dc=com

=head2 Where is an entry's name held?

Entries do B<not> contain their DN. When you retrieve an entry from
a search, the server will tell you the DN of each entry.

On the other hand, entries B<do> contain their RDN. Recall that the RDN
is formed from one or more attribute-value assertions (AVAs); each entry
must contain all the attributes and values in the RDN.

For example the entry:

 cn=Road Runner+l=Arizona,ou=bird,dc=cartoon,dc=com

B<must> contain a 'cn' attribute containing at least the value
"Road Runner", B<and> an 'l' attribute containing at least the value
"Arizona".

The attributes used in the RDN may contain additional values, but the
entry still only has one DN.

=head2 What is a search base.

A search base is a Distinguished Name that is the 
starting point of search queries.

Example of a DN:

 cn=Road Runner,ou=bird,dc=cartoon,dc=com  

Possible search base(s) for the proceeding DN:

 Base => cn=Road Runner,ou=bird,dc=cartoon,dc=com  
 Base => ou=bird,dc=cartoon,dc=com  
 Base => dc=cartoon,dc=com  
 Base => dc=com  

Setting the search base to the lowest possible branch of
the directory will speed up searches considerably.

=head2 What is the difference between a LDAP server and a relational database.

The most basic difference is that a directory server is  a
specialized database designed to provide fast searches. While a relational
database is optimized for transactions (where a series of operations is
counted as 1, thus if one of the steps fails, the RDBMS can roll-back to
the state it was in before you started).

Directories also typically are hierarchical in nature (RDBMS is typically
flat, but you can implement a hierarchy using tables and queries),
networkable, distributed and replicated.

LDAP provides an open-standard to a directory service.

Typically we use LDAP for email directories (all popular email clients
provide an LDAP client now) and authorization services (authentication and
access control).

You could use a RDBMS for these types of queries but there's no
set standard, in particular over TCP/IP to connect to databases over the
network. There's language specific protocols (like Perl's DBI and Java's
JDBC) that hide this problem behind an API abstraction, but that's not a
replacement for a standard access protocol.

LDAP is starting to be used on roles traditionally played by RDBMS in 
terms of general data management because it's easier to setup a LDAP 
server (once you understand the basic nomenclature) and you don't need 
a DBA to write your queries and more importantly all LDAP servers speak 
the same essential protocol, thus you don't have to fuss with a 
database driver trying to connect it to the Internet. Once you have an 
LDAP server up and running, it's automatically available over the 'net. 
It's possible to connect to a LDAP server from a variety of mechanisms, 
including just about every possible programming language.

More information on this topic can be found on the following URLs;

 http://www.openldap.org/faq/data/cache/378.html

 http://www.isode.com/whitepapers/ic-6055.html

=head2 What is the difference between a ldap reference and a ldap referral?

A referral is returned when the B<entire> operation must be resent to
another server.

A continuation reference is returned when B<part> of the operation must be
resent to another server.

See RFC 2251 section 4.5.3 for more details.

=head1 PERL-LDAP INSTALLATION

=head2 How do I install perl-ldap ?

To install the modules that are in the perl-ldap distribution follow the
same steps that you would for most other distributions found on CPAN, that
is

   # replace 0.33 with the version you have

   gunzip perl-ldap-0.33.tar.gz
   tar xvf perl-ldap-0.33.tar       
   cd perl-ldap-0.33

   perl Makefile.PL
   make
   make test
   make install

=head2 But I do not have make, how can I install perl-ldap ?

Well as luck would have it the modules in perl-ldap do not do anything
complex, so a simple copy is enough to install. First run

  perl -V

This will output information about the version of perl you have
installed. Near the bottom you will find something like

  @INC:
    /usr/local/perl/perl5.005/lib/5.00502/sun4-solaris
    /usr/local/perl/perl5.005/lib/5.00502
    /usr/local/perl/perl5.005/lib/site_perl/5.005/sun4-solaris
    /usr/local/perl/perl5.005/lib/site_perl/5.005
    .

This is a list of directories that perl searches when it is looking for
a module. The directory you need is the site_perl directory, but without
the system architecture name, in this case it is
C</usr/local/perl/perl5.005/lib/site_perl/5.005>. The files required
can then be installed with

   # replace 0.33 with the version you have

   gunzip perl-ldap-0.33.tar.gz
   tar xvf perl-ldap-0.33.tar       
   cd perl-ldap-0.33/lib

   cp * /usr/local/perl/perl5.005/lib/site_perl/5.005

=head2 How can I load Perl-LDAP into an ActiveState Perl installation.

There are several ways that Perl-LDAP can be installed into an
ActiveState Perl tree.

=over 4

=item 1.

The ActiveState ppm command can be used to install Perl-LDAP.
When a new version of Perl-LDAP is released, it takes ActiveState
a period of time to get the new release into the ActiveState ppm
system. 

=item 2.

If the user has nmake installed, the user can do a normal perl 
module install using nmake instead of make.

=item 3.

If the user does not have nmake or make, the user can install 
Perl-LDAP using the install-nomake script by issuing the 
following command.

 perl install-nomake

The install-nomake script can be used on any system that does not
have make installed. 

=back

=head2 What other modules will I need ?

perl-ldap does use other modules. Some are required, but some are
optional (ie required to use certain features)

=over 4

=item Convert::ASN1

This module is required for perl-ldap to work.

You can obtain the latest release from
  http://search.cpan.org/search?module=Convert::ASN1

=item Authen::SASL

This module is optional.  You only need to install Authen::SASL
if you want to use the SASL authentication method.

You can obtain the latest release from
  http://search.cpan.org/search?module=Authen::SASL

=item Digest::MD5

This module is optional. It also requires a C compiler when installing.
You only need to install Digest::MD5 if you want to use the SASL
DIGEST-MD5 authentication method.

You can obtain the latest release from
  http://search.cpan.org/search?module=Digest::MD5

=item URI::ldap

This module is optional. You only need to install URI::ldap if you are
going to need to parse ldap referrals. L<Net::LDAP> does not do this
automatically yet, so this module is not used by perl-ldap.

You can obtain the latest release from
  http://search.cpan.org/search?module=URI::ldap

=item OpenSSL and IO::Socket::SSL for Net::LDAPS

If you want to use Net::LDAP::LDAPS you will need this module
and the OpenSSL software package.

You can obtain the latest release of IO::Socket::SSL from
  http://search.cpan.org/search?module=IO::Socket::SSL

You can obtain the latest release of OpenSSL from
  http://www.openssl.org/

If you are using a Linux system, many of the distributions
have RPM packages that you can install.  Use your favorite
web search engine to find the package that you need.

=item XML::SAX and XML::SAX::Writer

If you want to use Net::LDAP::DSML you will need these modules.

You can obtain the latest releases from
  http://search.cpan.org/search?module=XML::SAX 
  http://search.cpan.org/search?module=XML::SAX::Writer


=item ResourcePool::Factory::Net::LDAP

If you want to use failover the ResourcePool::Factory::Net::LDAP
perl module provides methods to do this.

You can obtain the latest release from
  http://search.cpan.org/search?module=ResourcePool::Factory::Net::LDAP

=back

=head1 USING NET::LDAP

=head2 How do I connect to my server ?

The connection to the server is created when you create a new Net::LDAP
object, e.g.

  $ldap = Net::LDAP->new($server);

=head2 Net::LDAP-E<gt>new sometimes returns undef, why ?

The constructor will return undef if there was a problem connecting
to the specified server. Any error message will be available in $@

=head2 What is the proper format of the bind DN.

The DN used to bind to a directory is a FULLY QUALIFIED DN.  The exact
structure of the DN will depend on what data has been stored in the
server.

The following are valid examples.

  uid=clif,ou=People,dc=umich,dc=edu

  cn=directory manager,ou=admins,dc=umich,dc=edu

In some servers the following would be a valid fully qualified DN of
the directory manager.

  cn=directory manager

=head2 How can I tell when the server returns an error, bind() always returns
true ?

Most methods in Net::LDAP return a L<Net::LDAP::Message> 
object, or a sub-class of that. This object will hold the results 
from the server, including the result code.

So, for example, to determine the result of the bind operation.

  $mesg = $ldap->bind( $dn, password => $passwd );

  if ( $mesg->code ) {
    # Handle error codes here
  }

=head2 How can I set the LDAP version of a connection to my ldap server?

This is done by adding the version option when connecting or binding
to the LDAP server.

For example;

  $ldap = Net::LDAP->new( $server, version => 3 );

or

  $mesg = $ldap->bind( $dn, password => $passwd, version => 3 );

Valid version numbers are 2 and 3.
As of perl-ldap 0.27 the default LDAP version is 3.

=head2 I did a search on my directory using the 'search' method. Where did
the results go ?

Your search results are stored in a 'search object'.
Consider the following:

 use Net::LDAP;

 $ldap = Net::LDAP->new('ldap.acme.com') or die "$@";
 $mesg = $ldap->search(
                       base   => "o=acme.com",
                       filter => "uid=jsmith",
                      );

$mesg is a search object. It is a reference blessed into the
L<Net::LDAP::Search> package. By calling methods on this object you
can obtain information about the result and also the individual
entries.

The first thing to check is if the search was successful. This is done
with with the method $mesg-E<gt>code. This method will return the
status code that the server returned. A success will yield a zero
value, but there are other values, some of which could also be
considered a success.  See L<Net::LDAP::Constant>

  use Net::LDAP::Util qw(ldap_error_text);

  die ldap_error_text($mesg->code)
    if $mesg->code;

There are two ways in which you can access the entries. You can access
then with an index or you can treat the container like a stack and
shift each entry in turn. For example

  # as an array

  # How many entries were returned from the search
  my $max = $mesg->count; 

  for( my $index = 0 ; $index < $max ; $index++) {
    my $entry = $mesg->entry($index);
    # ...
  }

  # or as a stack

  while( my $entry = $mesg->shift_entry) {
    # ...
  }

In each case $entry is an entry object. It is a reference blessed into
the L<Net::LDAP::Entry> package. By calling methods on this object you
can obtain information about the entry.

For example, to obtain the DN for the entry

  $dn = $entry->dn;

To obtain the attributes that a given entry has

  @attrs = $entry->attributes;

And to get the list of values for a given attribute

  @values = $entry->get( 'sn' );

And to get the first of the values for a given attribute

  $values = $entry->get( 'cn' );

One thing to remember is that attribute names are case 
insensitive, so 'sn', 'Sn', 'sN' and 'SN' are all the same.

So, if you want to print all the values for the attribute C<'ou'> then this
is as simple as

  foreach ($entry->get_value( 'ou' )) {
      print $_,"\n";
    }

Now if you just want to print all the values for all the attributes you
can do

  foreach my $attr ($entry->attributes) {
    foreach my $value ($entry->get_value($attr)) {
      print $attr, ": ", $value, "\n";
    }
  }

=head2 How do I limit the scope of a directory search.

You limit the scope of a directory search by setting the
scope parameter of search request. 
Consider the following:

 use Net::LDAP;

 $ldap = Net::LDAP->new('ldap.acme.com') or die "$@";
 $mesg = $ldap->search(
                       base   => "o=acme.com",
                       scope  => 'sub',
                       filter => "uid=jsmith",
                      );

Values for the scope parameter are as follows.

=over 4

=item base

Search only the base object.

=item one

Search the entries immediately below the base object.

=item sub

Search the whole tree below the base object.
This is the default.                                         

=back

=head1 GETTING SEARCH RESULTS

There are two ways of retrieving the results of a requested
LDAP search; inline and by using a callback subroutine.

=head2 USING THE INLINE APPROACH

Using the inline approach involves requesting the data and
then waiting for all of the data to be returned before the
user starts processing the data.

Example: 

 use Net::LDAP;

 $ldap = Net::LDAP->new('ldap.acme.com') or die "$@";
 $mesg = $ldap->search(
                       base   => "o=acme.com",
                       scope  => 'sub',
                       filter => "sn=smith",
                      );
  #
  # At this point the user can get the returned data as an array
  # or as a stack.
  # In this example we will use an array

  # How many entries were returned from the search
  my $max = $mesg->count; 

  for( my $index = 0 ; $index < $max ; $index++) 
  {
    my $entry = $mesg->entry($index);
    my $dn = $entry->dn; # Obtain DN of this entry

    @attrs = $entry->attributes; # Obtain attributes for this entry.
    foreach my $var (@attrs)
    {
     #get a list of values for a given attribute
     $attr = $entry->get_value( $var, asref => 1 );
     if ( defined($attr) )         
     {          
         foreach my $value ( @$attr )          
         {           
          print "$var: $value\n";  # Print each value for the attribute.
         }         
     }                                                                       
    }
  }

As you can see the example is straight forward, but there is one
drawback to this approach.  You must wait until all entries for the
request search to be returned before you can process the data.  If
there several thousand entries that match the search filter this 
could take quite a long time period.

=head2 USING THE CALLBACK SUBROUTINE APPROACH

Using the callback approach involves requesting the data be sent
to a callback subroutine as each entry arrives at the client.

A callback is just a subroutine that is passed two parameters when
it is called, the mesg and entry objects.

Example: 

 use Net::LDAP;

 $ldap = Net::LDAP->new('ldap.acme.com') or die "$@";
 $mesg = $ldap->search(
                       base   => "o=acme.com",
                       scope  => 'sub',
                       filter => "sn=smith",
                       callback => \&callback,
                      );
 #
 # At this point the user needs to check the status of the
 # ldap search.
 # 

 if ( $mesg->code )
 {
    $errstr = $mesg->code;
    print "Error code:  $errstr\n";
    $errstr = ldap_error_text($errstr);
    print "$errstr\n";
 } 


 sub callback
 {
 my ( $mesg, $entry) = @_;

   #
   # First you must check to see if something was returned.
   # Last execution of callback subroutine will have no
   # defined entry and mesg object
   #
   if ( !defined($entry) )
   {
     print "No records found matching filter $match.\n"
     if ($mesg->count == 0) ; # if mesg is not defined nothing will print.
     return;
   }

   my $dn = $entry->dn; # Obtain DN of this entry

   @attrs = $entry->attributes; # Obtain attributes for this entry.
   foreach my $var (@attrs)
   {
    #get a list of values for a given attribute
    $attr = $entry->get_value( $var, asref => 1 );
    if ( defined($attr) )         
    {          
      foreach my $value ( @$attr )          
      {           
        print "$var: $value\n";  # Print each value for the attribute.
      }         
    }                                                                       
   }
   #
   # For large search requests the following 2 lines of code
   # may be very important, they will reduce the amount of memory 
   # used by the search results.
   #
   # If the user is not worried about memory useage then the 2 lines
   # of code can be omitted.
   #
   $mesg->pop_entry;

 }  # End of callback subroutine

As you can see the example is straight forward and it does not waste
time waiting for all of the entries to be returned.  However if the
pop_entry method is not used the callback approach can allocate a 
lot of memory to the search request.

=head1 USING NET::LDAPS

=head2 Using an SSL network connection, how do I connect to my server?

This class is a subclass of Net::LDAP so all the normal
Net::LDAP methods can be used with a Net::LDAPS object;
see the documentation for Net::LDAP to find out how to
query a directory server using the LDAP protocol.                        

The connection to the server is created when you create a new Net::LDAPS
object, e.g.

  $ldaps = Net::LDAPS->new($server,
                           port => '10000',
                           verify => 'require',
                           capath => '/usr/local/cacerts/',
                           );

Starting with version 0.28 perl-ldap also supports URIs in the new method.
So, the above can also be expressed as:

  $ldaps = Net::LDAP->new("ldaps://$server",
                           port => '10000',
                           verify => 'require',
                           capath => '/usr/local/cacerts/',
                           );

There are additional options to the new method with LDAPS URIs 
and the LDAPS new method and several additional methods are
included in the LDAPS object class.  

For further information and code examples read the LDAPS
module documentation;  perldoc Net::LDAPS

=head1 USING LDAP GROUPS.

=head2 What are LDAP groups.

LDAP groups are object classes that contain an attribute that can
store multiple DN values.  Two standard object classes are
'groupOfNames' (which has a 'member' attribute) and
'groupOfUniqueNames' (which has a 'uniqueMember' attribute.)

According to the RFCs a group can be a member of another group,
but some LDAP server vendors restrict this flexibility by not
allowing nested groups in their servers.

Two scripts for working with groups are available in the contrib
directory.  They are isMember.pl and printMembers.pl. 

=head2 How do you format a filter to search for entries whose 'member'
attribute has a particular value? 

Asking for (member=*) is OK - the directory uses the equality matching 
rule which is defined for the member attribute.

Asking for (member=c*) is not OK - there is no defined substring 
matching rule for the member attribute. That's because the member 
values are *not* strings, but distinguished names. There is no 
substring matching rule for DNs, see RFC 2256 section 5.50.

What you have to do is get the results of (member=*) and then select 
the required results from the returned values. You need to do this 
using knowledge of the string representation of DNs defined in RFC 
2253, which is important because the same DN can have different string 
representations. So you need to perform some canonicalization if you 
want to be correct.


=head1 USING DSML.

=head2 How can I access DSML features from PERL-LDAP.

Directory Service Markup Language (DSML) is the XML
standard for representing directory service information in
XML.

Support for DSML is included in PERL-LDAP starting with version
.20.

At the moment this module only reads and writes DSML entry
entities. It cannot process any schema entities because
schema entities are processed differently than elements.

Eventually this module will be a full level 2 consumer and
producer enabling you to give you full DSML conformance.

The specification for DSML is at http://www.oasis-open.org/specs/

For further information and code examples read the DSML
module documentation;  perldoc Net::LDAP::DSML

=head1 USING CONTROLS AND VIRTUAL LISTS.

=head2 How do I access the Control features.

Support for LDAP version 3 Control objects is included in 
perl-ldap starting with version .20.

For further information and code examples read the Control
module documentation;  perldoc Net::LDAP::Control

=head2 How do I access the Virtual List features.

Support for Virtual Lists is included in perl-ldap starting 
with version .20.

For further information and code examples read the Control
module documentation;  perldoc Net::LDAP::Control

=head1 GENERAL QUESTIONS.

=head2 Are there any other code examples.

Yes, there is an Examples pod file.  To view the pod
do the following command;  perldoc Net::LDAP::Examples

There is user contributed software in the contrib directory
that is supplied with the PERL-LDAP distribution.  This is an
excellent source of information on how to use the PERL-LDAP module.

=head2 Are there any performance issues with perl-ldap ?

In the vast majority of use cases (one user has suggested 9 out of 10)
there are no performance issues with perl-ldap.

Where you may wish to use perl-ldap to perform, for example, a very
large number of queries (e.g. 10,000) in succession you may find a
noticeable performance difference between perl-ldap and non pure-perl
modules. This is not because of perl-ldap itself but because of the
pure-perl Convert::ASN1 module that it depends on.

You should make up your own mind, based upon your own situation
(performance requirements, hardware etc.) as to whether you should use
perl-ldap or not. The figures quoted in this answer are only
indicative, and will differ for different people.

=head2 Can I contribute perl scripts that use perl-ldap
to the contrib section? 

Any one can submit a perl script that uses perl-ldap for inclusion
in the contrib section.  Graham Barr will determine if the script
will be included and will do the initial check in of the script
to the SVN system on http://svn.mutatus.co.uk.  Graham will make you
the owner/developer of the script. 

There are a couple of requirements for consideration.

You must supply a one line description of your script to be included
in the contrib readme file.

Inside the script will be the pod documentation for the script.
No auxiliary documentation will be allowed.  For examples of how
to do this see the tklkup script currently in the contrib section.

=head2 Is it possible to get a complete entry, DN and attributes 
without specifying the attributes name?

Yes, just specify you want a list of no attributes back. The RFC says 
that this tells the server to return all readable attributes back 
(there may be access controls to prevent some from being returned.)

So in the search method, just set (for LDAPv2):

		attrs => [ ]

If you are using LDAPv3, you can specify an attribute called "*" 
instead, which lets you ask for additional (i.g. operational) attributes 
in the same search.

		attrs => [ "*" ]

To get all operational attributes in a search, some servers allow
the use of the "+" pseudo attribute. So that with these servers

		attrs => [ "*", "+" ]

will return the most information from the server.		

=head2 How do I put a JPEG photo into a entry in the directory.

Follow the following code example, replacing the (...) with
whatever is relevant to your setup. 

  use Net::LDAP;
  use Net::LDAP::Util qw(ldap_error_text);
  use CGI;

  local $/ = undef;
  my $jpeg = <$filename>;

  my $ldap = Net::LDAP->new(...);
  my $res = $ldap->bind(...);
     $res = $ldap->modify(...,
                   add => [ 'jpegPhoto' => [ $jpeg ] ]);
     $res = $ldap->unbind();


=head2 How do I add a jpeg photo into a entry in the directory via html-forms.

Follow the following code example, replacing the (...) with
whatever is relevant to your setup. 

  use Net::LDAP;
  use Net::LDAP::Util qw(ldap_error_text);
  use CGI;

  my $q = new CGI;

  print $q->header;
  print $q->start_html(-title => 'Change JPEG photo');

  if ($q->param('Update')) {
          my $filename = $q->param('jpeg');
          local $/ = undef;
          my $jpeg = <$filename>;

          my $ldap = Net::LDAP->new(...);
          my $res = $ldap->bind(...);
          $res = $ldap->modify(...,
                          add => [ 'jpegPhoto' => [ $jpeg ] ]);
          $res = $ldap->unbind();
  } else {
          print $q->start_multipart_form();
          print $q->filefield(-name => 'jpeg', -size => 50);
          print $q->submit('Update');
          print $q->end_form();
  }

  print $q->end_html();

=head2 What happens when you delete an attribute that does not exist.

It is an error to delete an attribute that doesn't exist.  When you 
get the error back the server ignores the entire modify operation
you sent it, so you need to make sure the error doesn't happen.

Another approach, if you are using LDAPv3 (note beginning with version .27
Net::LDAP uses LDAPv3 by default) is to use a 'replace' with your
attribute name and no values.
In LDAPv3, this is defined to always work even if that attribute
doesn't exist in the entry.

ie:

  my $mesg = $ldap->modify( $entry, replace => { %qv_del_arry } );

But make sure you are using LDAPv3, because that is defined to B<not> work
in LDAPv2. (A nice incompatibility between LDAPv2 and LDAPv3.)

=head2 How can I delete a referral from an LDAP tree.

Since this is a proprietary feature, you will have to check your
server's documentation. You might find that you need to use a control. If
there is a control called something like managedsait, that's the one you
should probably use.  For proper operation you will need the oid number
for managedsait; 2.16.840.1.113730.3.4.2 and do not specify a value for
type.

The code required will look similar to the following code snippet.

  $mesg =  $ldap->delete("ref=\"ldap://acme/c=us,o=bricks\",o=clay",
                  control => {type => "2.16.840.1.113730.3.4.2"} ); 

=head2 How do I add an ACI/ACL entry to a directory server with
Perl-LDAP.

ACIs and ACLs are proprietary features in LDAP. The following code
snippet works with a Netscape directory server. You will need the
specify the correct DN (-DN-) and correct attribute(s) (-nom attr-).

  my $aci = '(target="ldap:///-DN-")(targetattr="-nom attr-")(version 3.0;
              acl "-nom acl-"; deny(all) userdn = "ldap:///self";)' ;

  $ldap->modify($dn_modif, add => {'aci' => $aci });

=head2 How do I avoid file type and data type mis-matching when loading
data from a Win32 system.

When loading a binary attribute with data read from a file on a Win32
system, it has been noted that you should set "binmode" on the file
before reading the file contents into the data array.

Another possible solution to this problem is to convert the 
binary data into a base64 encoded string and then store the encoded string
in the file.  Then when reading the file, decode the base64 encoded 
string back to binary and then use perl ldap to store the data
in the directory.

=head2 How do I create a Microsoft Exchange 5.x user.

This is a solution provide by a perl-ldap user.

This code works with ActiveState Perl running on WinNT 4. Please note that
this requires the Win32::Perms module, and needs valid NT account info to
replace the placeholders. 

  use Net::LDAP;
  use Net::LDAP::Util;
  use Win32::Perms;

  #Constants taken from ADSI Type Library
  $ADS_RIGHT_EXCH_ADD_CHILD = 1;
  $ADS_RIGHT_EXCH_DELETE = 0x10000;
  $ADS_RIGHT_EXCH_DS_REPLICATION = 64;
  $ADS_RIGHT_EXCH_DS_SEARCH = 256;
  $ADS_RIGHT_EXCH_MAIL_ADMIN_AS = 32;
  $ADS_RIGHT_EXCH_MAIL_RECEIVE_AS = 16;
  $ADS_RIGHT_EXCH_MAIL_SEND_AS = 8;
  $ADS_RIGHT_EXCH_MODIFY_ADMIN_ATT = 4;
  $ADS_RIGHT_EXCH_MODIFY_SEC_ATT = 128;
  $ADS_RIGHT_EXCH_MODIFY_USER_ATT = 2;

  $EXCH_USER_RIGHTS = $ADS_RIGHT_EXCH_MAIL_RECEIVE_AS |
  $ADS_RIGHT_EXCH_MAIL_SEND_AS |
  $ADS_RIGHT_EXCH_MODIFY_USER_ATT;

  $exch = Net::LDAP->new('server', debug =>0) || die $@;

  $exch->bind( 'cn=admin_user,cn=nt_domain,cn=admin', version =>3,
  password=>'password');

  $myObj = Win32::Perms->new();
  $Result = $myObj->Owner('nt_domain\user_name');
  $myObj->Group('nt_domain\Everyone');
  $myObj->Allow('nt_domain\user_name',
  $EXCH_USER_RIGHTS,OBJECT_INHERIT_ACE);
  $BinarySD = $myObj->GetSD(SD_RELATIVE);
  $TextSD = uc(unpack( "H*", $BinarySD ));
  Win32::Perms::ResolveSid('nt_domain\user_name', $sid);
  $mysid = uc(unpack("H*",$sid));

  $result = $exch->add ( dn   =>
                'cn=user_name,cn=container,ou=site,o=organisation',
                attr => [ 'objectClass' => ['organizationalPerson'],
                          'cn'   => 'directory_name',
                          'uid' => 'mail_nickname',
                          'mail' => 'smtp_address',
                        'assoc-nt-account' => [ $mysid ],
                        'nt-security-descriptor' => [ $TextSD ],
                        'mailPreferenceOption'  => 0
                        ]
              );


  print ldap_error_name($result->code);

=head2 Ho do I reset a user's password ...

=head3 Z<>... in most LDAP servers ?

Most LDAP servers use the standard userPassword attribute as the
attribute to set when you want to change a user's password.

They usually allow to set the password either using the regular 
modify operation on the userPassword attribute or using the
extended LDAP Password Modify operation defined in RFC3062.

The recommended method is the extended Password Modify operation,
which offers a standardized way to set user passwords but 
unfortunately is not available on all LDAP servers.

Whether the extended Password Modify operation is available can be
found out by searching the attribute supportedExtension for the
value 1.3.6.1.4.1.4203.1.11.1 in the RootDSE object.

If the extended Password Modify operation is not available the
alternative is the regular modification of the userPassword attribute.

But this method has some drawbacks:

=over 4

=item *

Depending on the type of the server the arguments to the modify
operations may vary. Some want the modify done with replace,
some want it done by explicitly deleting the old password
and add of the new one.
This may even depend on whether you change the password for the bound
user or as an administrator for another user.

=item *

With the modify operation some servers expect the client to
do the hashing of the password on the client side. I.e. all
clients that set passwords need to agree on the algorithm
and the format of the hashed password.

=item *

Some LDAP servers do not allow setting the password if the
connection is not sufficiently secured. I.e. require SSL or TLS
support to set the password (which is heavily recommended anyway ;-)

=back

Here is an example of how to change your own password (for brevity's 
sake error checking is left out):

  use Net::LDAP;

  my $ldap = Net::LDAP->new('ldaps://server.domain')  or  die "$@";
  my $mesg = $ldap->bind('cn=Joe User,dc=perl,dc=ldap,dc=org',
                         password => 'oldPW');

  my $rootdse = $ldap->root_dse();

  if ($rootdse->supported_extension('1.3.6.1.4.1.4203.1.11.1') {

      require Net::LDAP::Extension::SetPassword;

      $mesg = $ldap->set_password(user => 'cn=Joe User,dc=perl,dc=ldap,dc=org',
                                  oldpasswd => 'oldPW',
                                  newpasswd => 'newPW');
  }
  else {
      $mesg = $ldap->modify('cn=Joe User,dc=perl,dc=ldap,dc=org',
                            changes => [
                                delete => [ userPassword => $oldPW ]
                                add    => [ userPassword => $newPW ] ]);
  }

  $ldap->unbind();

=head3 Z<>... in MS Active Directory ?

With Active Directory a user's password is stored in the unicodePwd
attribute and changed using the regular modify operation.

ADS expects this password to be encoded in Unicode - UTF-16 to be exact.
Before the unicode conversion is done the password needs to be
surrounded by double quotes which do not belong to the user's password.

For the password modify operation to succeed SSL is required.

When changing the password for the user bound to the directory
ADS expects it to be done by deleting the old password and
adding the new one.
When doing it as a user with administrative priviledges replacing
the unicodePwd's value with a new one is allowed too.

Here's an example that demonstrates setting your own password
(again almost no error checking):

  use Net::LDAP;
  use Unicode::Map8;
  use Unicode::String qw(utf16);

  # build the conversion map from your local character set to Unicode
  my $charmap = Unicode::Map8->new('latin1')  or  die;

  # surround the PW with double quotes and convert it to UTF-16
  # byteswap() was necessary in experiments on i386 Linux, YMMV
  my $oldUniPW = $charmap->tou('"'.$oldPW.'"')->byteswap()->utf16();
  my $newUniPW = $charmap->tou('"'.$newPW.'"')->byteswap()->utf16();

  my $ldap = Net::LDAP->new('ldaps://ads.domain.controller')  or  die "$@";

  my $mesg = $ldap->bind('cn=Joe User,dc=your,dc=ads,dc=domain',
                         password => 'oldPW');

  $mesg = $ldap->modify('cn=Joe User,dc=your,dc=ads,dc=domain',
                        changes => [
                            delete => [ unicodePwd => $oldUniPW ]
                            add    => [ unicodePwd => $newUniPW ] ]);

  $ldap->unbind();


=head2 How can I simulate server failover.

Perl-LDAP does not do server failover, however there are several
programming options for getting around this situation.

Here is one possible solution.

  unless ( $ldaps =
            Net::LDAPS->new($ldapserverone,
                            port=>636,timeout=>5) ) 
          {
              $ldaps = Net::LDAPS->new($ldapservertwo,
                                       port=>636,timeout=>20) || 
              return 
              "Can't connect to $ldapserverone or $ldapservertwo via LDAPS: $@";
          }

As of version 0.27 of perl-ldap the above can be expressed much simpler:

  $ldaps = Net::LDAPS->new([ $ldapserverone, $ldapservertwo ],
                           port=>636, timeout=>5)  or  die "$@";


=head1 Using X.509 certificates.

=head2 How do I store X.509 certificates in the directory?

The first problem here is that there are many different formats to hold
certificates in, for example PEM, DER, PKCS#7 and PKCS#12. The directory
B<only> uses the DER format (more correctly, it only uses the BER format)
which is a binary format.

Your first job is to ensure that your certificates are therefore in DER/BER
format. You could use OpenSSL to convert from PEM like this:

  openssl x509 -inform PEM -in cert.pem -outform DER -out cert.der

Consult the OpenSSL documentation to find out how to perform other
conversions.

To add a certificate to the directory, just slurp in the DER/BER
certificate into a scalar variable, and add it to the entry's
userCertificate attribute. How you do that will depend on which version of
LDAP you are using.

To slurp in the certificate try something like this:

  my $cert;
  {
      local $/ = undef; # Slurp mode
      open CERT, "cert.der" or die;
      binmode CERT;
      $cert = <CERT>;
      close CERT;
  }
  # The certificate is now in $cert

For LDAPv2, because most directory vendors ignore the string representation
of certificates defined in RFC 1778, you should add this value to the
directory like this:

  $res = $ldap->modify("cn=My User, o=My Company,c=XY",
                       add => [
                               'userCertificate' => [ $cert ]
                              ]);
  die "Modify failed (" . ldap_error_name($res->code) . ")\n"
      if $res->code;

For LDAPv3, you must do this instead:

  $res = $ldap->modify("cn=My User, o=My Company, c=XY",
                       add => [
                               'userCertificate;binary' => [ $cert ]
                              ]);
  die "Modify failed (" . ldap_error_name($res->code) . ")\n"
      if $res->code;

Of course, the entry you are trying to add the certificate to must use
object classes that permit the userCertificate attribute, otherwise the
modify will fail with an object class violation error. The inetOrgPerson
structural object class permits userCertificates, as does the
strongAuthenticationUser auxiliary object class. Others might also.

=head1 ADDITIONAL DIRECTORY AND LDAP RESOURCES.

=head2 URLs.

Directory Services Mark Language (DSML)
http://www.oasis-open.org/specs/

eMailman LDAP information
http://www.emailman.com/ldap/

Rafael Corvalan's LDAP shell
http://sf.net/projects/ldapsh

LDAPS, also known as LDAPGURU.
I<This web site has a nasty habit of resizing the browser
to cover the WHOLE screen.>
http://www.ldaps.com

Jeff Hodges's Kings Mountain LDAP 
http://www.kingsmountain.com/ldapRoadmap.shtml

Mark Wahl's LDAP World at Innosoft.
http://www.innosoft.com/ldapworld/
(outdated: last update was in 1998)

Open Source LDAP Directory Server.
http://www.openldap.org/

CriticalPath
http://www.cp.net/

IBM Directory Server
http://www-306.ibm.com/software/network/directory/server/

Innosoft
http://www.innosoft.com
(acquired by Sun)

Isode (was MessagingDirect)
http://www.isode.com/

Netscape Directory Developers Area
http://developer.netscape.com/directory/

Nexor's X.500 and Internet Directories
http://www.nexor.com/info/directory.htm/

Novell's eDirectory
http://www.novell.com/

Novell's LDAPzone
http://ldapzone.com/

Octet String
http://www.octetstring.com/

SUN JAVA JNDI (Java Naming and Directory Interface)
http://www.java.sun.com/jndi/

Sun One, formerly Iplanet.
http://wwws.sun.com/software/

Eine deutsche LDAP Website 
A german LDAP Website
http://verzeichnisdienst.de/ldap/Perl/index.html

The 2 following URLs deal mainly with Microsoft's
Active Directory.

Directory Works
http://directoryworks.com/

ActiveX LDAP Client
http://www.polonia-online.com/ldap/

=head2 BOOKS

Developing LDAP and ADSI Clients for Microsoft(R) Exchange.
By Sven B. Schreiber.  ISBN:  0201657775

Implementing LDAP.
By Mark Wilcox.  ISBN:  1861002211

LDAP: Programming Directory-Enabled Applications With 
Lightweight Directory Access Protocol. 
By Tim Howes, Mark Smith.  ISBN:  1578700000

LDAP Programming; Directory Management and Integration.
By Clayton Donley.  ISBN:  1884777910

LDAP Programming with Java. 
By Rob Weltman, Tony Dahbura.  ISBN:  0201657589

LDAP System Administration.
By Gerald Carter.  ISBN:  1565924916

Managing Enterprise Active Directory Services. 
By Robbie Allen, Richard Puckett.  ISBN:  0672321254

Solaris and LDAP Naming Services.
By Tom Bialaski, Michael Haines. ISBN:  0-13-030678-9

Understanding and Deploying LDAP Directory Services (2ed).
By Tim Howes, Mark Smith, Gordon Good.
ISBN:  0672323168

LDAP Directories Explained.
By Brian Arkills. ISBN 0-201-78792-X

=head1 AUTHORS

Any good FAQ is made up of many authors, everyone that contributes
information to the perl-ldap mail list is a potential author.

An attempt to maintain this FAQ is being done by Chris Ridd
E<lt>chris.ridd@isode.comE<gt> and Peter Marschall <peter@adpm.de>.
It was previously updated by Clif Harden E<lt>charden@pobox.comE<gt>.

The original author of this FAQ was Graham Barr E<lt>gbarr@pobox.comE<gt>

Please report any bugs, or post any suggestions, to the 
perl-ldap mailing list E<lt>perl-ldap@perl.orgE<gt>.

=head1 COPYRIGHT

Copyright (c) 1999-2004 Graham Barr. All rights reserved. This document is
distributed, and may be redistributed, under the same terms as Perl itself.

=cut