LDAP

LDAP Authentication

Complete HOW-TO is available here

LDAP and User Roles

It is recommended that certain user rights are removed when using LDAP for login. The user should not be allowed to change their password or their email address. It is also suggested that the user not be allowed to edit their profile, however I have found certain fields that I would like the user to edit. To set the rights edit the file :

vi /opt/eprints3/archives/yourarchivename/cfg/cfg.d/user_roles.pl

######################################################################
#
# User Roles
#
#  Here you can configure which different types of user are 
#  parts of the system they are allowed to use.
#
######################################################################
$c->{user_roles}->{user} = [qw/
       general
       edit-own-record
       saved-searches
       deposit
/],
$c->{user_roles}->{editor} = [qw/
       general
       edit-own-record
       saved-searches
       deposit
       editor
       view-status
       staff-view
/],
$c->{user_roles}->{admin} = [qw/
       general
       edit-own-record
       saved-searches
       set-password
       deposit
       change-email
       editor
       view-status
       staff-view
       admin
/],
#$c->{user_roles}->{minuser} = [qw/
#       saved-searches
#       set-password
#       change-email
#       change-user
#       no_edit_own_record
#       lock-username-to-email
#/];

After editing restart Apache.

LDAP Testing

Below is test script to check whether you can connect to the LDAP server and get attributes back for a particular user. This should generall be saved in /opt/eprints3/archives/ARCHIVE/bin/ldaplookup It can be called as follows:

/opt/eprints3/archives/ARCHIVE/bin/ldaplookup USERNAME

#!/usr/bin/perl -w

# EPrints Services LDAP test script
use Net::LDAP;
use Net::LDAP::Constant;
use strict;

my ($user_sent) = $ARGV[0];

# Params
my $ldap_host = "ldaps://ad.example.org"; # Active Directory server on example.org domain
my $bind_dn = "cn=USERNAME,ou=root,dc=example,dc=org"; # one or more 'ou's may need to be set
my $bind_pword = "PASSWORD";
my $base = "dc=example,dc=org"; # Likely the same domain as the AD server itself

# Connect to server
my $ldap = Net::LDAP->new( $ldap_host, version => 3, port => 636 ); # Version and port may need changing

die "LDAP connect error: $@\n" unless defined $ldap;

# Try to bind
my $mesg;
if( $bind_dn eq "" && $bind_pword eq "" )
{
       $mesg = $ldap->bind; # anonymous bind
}
else
{
       $mesg = $ldap->bind( $bind_dn, password => $bind_pword );
}
die "LDAP bind error: " . $mesg->error() . "\n" if $mesg->code();

# Search for an account and get all available attributes (by not setting attrs)
$mesg = $ldap->search (
       base    => $base,
       scope   => "sub",
       filter => "uid=$user_sent", # Most likely cn, uid or sAMAccountName
       sizelimit => 1,
);
if( $mesg->code() )
{
       print STDERR "LDAP search error: ".$mesg->error."\n";
       exit;
}

my $entr = $mesg->pop_entry;
unless( defined $entr )
{
       print STDERR "LDAP no search results returned\n";
       exit 1;
}

# See what attributes are set for this user
print $entr->dump;

$ldap->unbind;

LDAP Authentication with Bulk Import of Users

This recipe enables authenticating passwords against an LDAP directory for all users (including administrators). The users will need to already exist in EPrints, most likely created by a bulk import from your LDAP server.

The recommendation for EPrints is not to allow users to alter email and passwords, as these changes are not at present written back to the LDAP database.

LDAP Configuration

Both the scripts for LDAP user login and import/update of users from LDAP require a number of parameters these are best saved in the archive's cfg/cfg.d/ldap.pl file.

 vi /opt/eprints3/archives/yourarchivename/cfg/cfg.d/ldap.pl

 # Configuration required to manage users who can login / be imported to the repository.
 
 $c->{ldap_hostname} = "ldaps://ldap.example.org";

 # Leave empty for anonymous bind to LDAP
 $c->{ldap_bind_username} = "CN=username,OU=Staff,OU=ROOT,DC=example,DC=org";
 $c->{ldap_bind_password} = "CHANGEME";

 # Typically used in bin/update_users
 $c->{ldap_import_base} = "DC=example.org";
 $c->{ldap_import_filter} = "(&(objectClass=person)(memberOf=CN=Staff,OU=Groups,OU=ROOT,DC=example.org))";

 # Typically used in cfg/cfg.d/user_login.pl
 $c->{ldap_login_base} = $c->{ldap_import_base};
 $c->{ldap_login_filter} = "(&(objectClass=person)(memberOf=CN=AdminStaff,OU=Groups,OU=ROOT,DC=example.org))";

LDAP Authentication

All changes for LDAP authentication can be made in a single file, the file contains useful notes on configuration. Here is an example from my site, I have configured a standard Samba Domain using LDAP for authentication, if you have similar then this config may work for you :

See user_login.pl for general information on check_user_password.

Edit the file :

vi /opt/eprints3/archives/yourarchivename/cfg/cfg.d/user_login.pl

# This function allows you to override the default username/password
# authentication. For example, you could apply different authentication rules to 
# different types of user.
#
# Example: LDAP Authentication (Quick Start)
#
# Tip: use the test script to determine your LDAP parameters first! Then put the 
# following parameters in ldap.pl or similarly name file in your archive's 
# cfg/cfg.d directory:  ldap_hostname, ldap_bind_username, ldap_bind_password
# ldap_import_base, ldap_import_filter, ldap_login_base, ldap_login_filter
# Tip: remove the set-password privilege from users and editors in
# user_roles.pl. Also consider removing edit-own-record and 
# change-email.

$c->{check_user_password} = sub {
  my( $session, $username, $password ) = @_;

  # Cannot login with a username
  return 0 if $username =~ /[^a-zA-Z0-9._\-@]/;

  # See if user already exists in EPrints.  .
  my $user = EPrints::DataObj::User::user_with_username( $session, $username );

  # You may wish fail login if the user does not already have an account.
  # return 0 unless defined $user;

  # Get user type from database or assume standard user if no user / user type is set.
  my $usertype = defined $user ? $user->get_type : "user";

  # minuser and local_admin types have local database logins.        
  if( $usertype eq "minuser" || $usertype eq "local_admin" )
  {
    return $session->get_database->valid_login( $username, $password );
  }

  # Connect to the LDAP hostname configured for this repositiory
  use Net::LDAP;
  my $ldap_host = $session->get_repository->get_conf( "ldap_hostname" );
  my $ldap = Net::LDAP->new ( $ldap_host, version => 3 );
  unless( $ldap )
  {
    $session->get_repository->log( "LDAP connect error: $@\n" );
    return 0;
  }

  # Bind using username and password configured for this repository
  my $bind_dn = $session->get_repository->get_conf( "ldap_bind_username" ) || "";
  my $bind_pword = $session->get_repository->get_conf( "ldap_bind_password" ) || "";
  my $mesg;
  if( $bind_dn eq "" && $bind_pword eq "" )
  {
    $mesg = $ldap->bind; # anonymous bind
  }
  else
  {
    $mesg = $ldap->bind( $bind_dn, password => $bind_pword );
  }
  if( $mesg->code() )
  {
    $session->get_repository->log( "LDAP bind error: " . $mesg->error . "\n" );
    return 0;
  }

  # Lookup the user based on the username they provided when logging in.  It is assume this is 
  # the sAMAccountName attribute on your Active Directory LDAP server, it may be uid or cn.
  my $base = $session->get_repository->get_conf( "ldap_login_base" );
  my $filter = $session->get_repository->get_conf( "ldap_login_filter" );
  $mesg = $ldap->search(
    base => $base,
    attrs => [qw( sAMAccountName givenName sn mail displayname description memberOf )],
    scope => "sub",
    filter => "&(sAMAccountName=$username) $filter",
    sizelimit => 2,
    timelimit => 30,
  );
  if( $mesg->code() )
  {
    $session->get_repository->log( "LDAP search error: ".$mesg->error."\n" );
    return 0;
  }
  if( $mesg->count() != 1 )
  {
     return 0;
  }

  # If user could be found in LDAP check the password they provided when logging in is correct.
  my $entr = $mesg->entry(0);
  my $user_dn = $entr->dn();
  $mesg = $ldap->bind( $user_dn, password => $password );
  if( $mesg->code )
  {
    $session->get_repository->log( "Failed authentication for $user_dn: ".$mesg->error."\n" );
    return 0;
  }

  # Uncomment to allow on-demand creation of users
  #unless( defined $user )
  #{
  #  my $data = {
  #    username => $username,
  #    usertype => $usertype, # This will be a standard user
  #  };
  #  my $name;
  #  $name->{given} = $entr->get_value( "givenName" ) if defined $entr->get_value( "givenName" );
  #  $name->{family} = $entr->get_value( "sn" ) if defined $entr->get_value( "sn" );
  #  $data->{name} = $name if defined $name;
  #  $data->{email} = $entr->get_value( "mail" ) if defined $entr->get_value( "mail" );
  #  $data->{dept} = $entr->get_value( "ou" ) if defined $entr->get_value( "ou" );
  # 
  #  $user = EPrints::DataObj::User->create_from_data(
  #    $session,
  #    $data,
  #    $session->get_repository->get_dataset( "user" ) 
  #  );
  #}

    return 1;
}

After editing restart Apache.

LDAP Import

Below is an example of a script to import/update users from LDAP based on them being founder under the ldap_import_filter set in ldap.pl above. Typically you would edit this files as follows:

vi /opt/eprints3/archives/myarchivename/bin/update_users

Before you can run this you will need to change permissions sot it can be run:

chmod u+x /opt/eprints3/archives/myarchivename/bin/update_users

Then to run the script use the following:

/opt/eprints3/archives/myarchivename/bin/update_users myarchivename
 
#!/usr/bin/perl -w

# EPrints LDAP example user import/update script

use FindBin;
use lib "$FindBin::Bin/../../../perl_lib"; 

use EPrints;
use Getopt::Long;
use Net::LDAP;
use Net::LDAP::Control::Paged;
use Net::LDAP::Constant qw( LDAP_CONTROL_PAGED );
use strict;

my $verbose = 0;
GetOptions(
  'verbose+' => \$verbose,
);

my $session = EPrints::Session->new( 1 , $ARGV[0] );
exit( 1 ) unless defined $session;

# Params
my $ldap_host = $session->get_repository->get_conf( "ldap_hostname" );
my $bind_dn = $session->get_repository->get_conf( "ldap_bind_username" );
my $bind_pword = $session->get_repository->get_conf( "ldap_bind_password" );
my $base = $session->get_repository->get_conf( "ldap_import_base" );
my $filter = $session->get_repository->get_conf( "ldap_import_filter" );

# Connect to server
my $ldap = Net::LDAP->new( $ldap_host, version => 3 );
die "LDAP connect error: $@\n" unless defined $ldap;

# Try to bind
my $mesg;
if( $bind_dn eq "" && $bind_pword eq "" )
{
  $mesg = $ldap->bind; # anonymous bind
} 
else
{
  $mesg = $ldap->bind( $bind_dn, password => $bind_pword );
}
die "LDAP bind error: " . $mesg->error() . "\n" if $mesg->code();

my $updated_counter = 0;
my $created_counter = 0;

# Create paging control
my $page = Net::LDAP::Control::Paged->new( size => 100 );

# Build args for the search
my @args = (
  base => $base,
  scope => "sub",
  filter => $filter,
  callback => \&process_entry,
  control => [ $page ],
);

print "\n$created_counter user(s) created.\n $updated_counter user(s) updated.\n" if $verbose;

my $cookie;
while( 1 )
{
  # Perform search
  my $result = $ldap->search( @args );

  # Only continue on LDAP_SUCCESS
  $result->code and last;

  # Get cookie from paged control
  my( $resp ) = $result->control( LDAP_CONTROL_PAGED ) or last;
  $cookie = $resp->cookie or last;

  # Set cookie in paged control
  $page->cookie( $cookie );
}

if( $cookie )
{
  # We had an abnormal exit, so let the server know we do not want any more
  $page->cookie( $cookie );
  $page->size( 0 );
  $ldap->search( @args );
}

$ldap->unbind;
$session->terminate; 

# Process entry
sub process_entry
{
  my( $mesg, $entr ) = @_;

  return unless defined $entr and $entr->can("get_value");

  my $username = $entr->get_value( "sAMAccountName" );
  my $given = $entr->get_value( "givenName" );
  my $family = $entr->get_value( "sn" );
  my $email = $entr->get_value( "mail" );
  my $dept = $entr->get_value( "department" );

  # Assumes that the user account will have a given name, family name, username and email address
  return unless defined $username && defined $given && defined $family && defined $email;

  # Can we find this user already in EPrints by username
  my $user = EPrints::DataObj::User::user_with_username( $session, $username );
  # If not maybe we can find them by email address.
  if( !defined $user )
  {
    my $user = EPrints::DataObj::User::user_with_email( $session, $email );
  }
  if( !defined $user )
  {
    print "Creating for username: $username\n" if $verbose;
    $user = EPrints::DataObj::User::create( $session, "user" );
    $created_counter = $created_counter +1;
  }
  else
  {
    print "Updating for username: $username with ID: ".$user->id."\n" if $verbose;
    $updated_counter = $updated_counter+1;
  }
  my $name = {
    family => $family,
    given => $given,
  }; 
  my $usertype = "user";
  $user->set_value( "usertype", $usertype );
  $user->set_value( "username", $username );
  $user->set_value( "name", $name );
  $user->set_value( "email", $email );
  $user->set_value( "dept", $dept );
  $user->commit();
}

Things to note

• These scripts use a dedicated proxy account which must exist in your LDAP tree and has appropriate permissions (ACL settings) to search for users and read their uid,givenname,sn,mail attributes.
• It gets this proxy accounts' password from a file inside the repository configuration. this file needs to have read permissions for the user your webserver runs as (e.g. www-data on Debian). Use file system permissions to protect this (e.g. chmod 400 ldap.passwd).
• It changes the flow of user_login.pl a little to only check for local admin accounts (no users or editors; we have them all in our LDAP tree) and only when no user is found for ldap authentication. This allows you to have your admins in LDAP (if you want) but still use the local admin for "promoting" other users to admins, among other things (which could also be done with a simple SQL update directly in the RDBMS). If you don't need the local admin, remove those lines and just return 0 since no user was found in LDAP.
• you could change the default role for generated user accounts from user, if you really wanted.

Kerberos Authentication on AD with On-Demand Creation of Users using LDAP

Tested on 3.3.8

Here's another example of a customized /opt/eprints3/archives/ARCHIVEID/cfg/cfg.d/user_login.pl:

• allowing LDAP accounts to login, using the following example
• allowing the local eprints admin account to login w/ database authentication
• creating eprints accounts for all successfully authenticated LDAP users on the fly

$c->{check_user_password} = sub {
  my( $session, $username, $password ) = @_;
  
  # Kerberos authentication for "user", "editor" and "admin" types (roles)
  
  use Net::LDAP; # IO::Socket::SSL also required
  use Authen::Krb5::Simple;
  use Authen::SASL;
  
  # LDAP tunables
  my $ldap_host = "ldap.example.org";
  my $base      = "OU=people,DC=example,DC=org";
  my $proxy_user ="ad_read";
  my $dn        = "CN=$proxy_user,$base";
  
  # Kerberos tunables
  my $krb_host = "example.org";
     
  my $krb 	  = Authen::Krb5::Simple->new(realm => $krb_host);
  unless ( $krb )
  {
  	print STDERR "Kerberos error: $@\n";
  	return 0;
  }
  
  my $ldap      = Net::LDAP->new ( $ldap_host );
  unless( $ldap )
  {
      print STDERR "LDAP error: $@\n";
      return 0;
  }
  
  my $sasl = Authen::SASL->new(
         mechanism => 'GSSAPI', 
         callback => { user => 'ad_read' }
       ) or die "$@";
  
  my $mesg = $ldap->bind(sasl => $sasl);
  
  if( $mesg->code() )
  {
      print STDERR "LDAP Bind error: " . $mesg->error() . "\n";
      return 0;
  }
  
  # Distinguished name (and attribues needed later on) for this user
  my $result = $ldap->search (
      base    => "$base",
      filter  => "(&(sAMAccountName=$username))",
      attrs   =>  ['1.1', 'uid', 'sn', 'givenname', 'mail', 'department', 'title'],
      sizelimit=>1
  );
  
  my $entr = $result->pop_entry;
  unless( defined $entr )
  {
      # Allow local EPrints authentication for admins (accounts not found in LDAP)
      my $user = EPrints::DataObj::User::user_with_username( $session, $username );
      return 0 unless $user;
  
      my $user_type = $user->get_type;
      if( $user_type eq "admin" )
      {
          # internal authentication for "admin" type
          return $session->get_database->valid_login( $username, $password );
      }
      return 0;
  }
  
  # Check password
  if( !$krb->authenticate( $username, $password ) )
  {
  	print STDERR "$username authentication failed: ", $krb->errstr(), "\n";
      return 0;
  }
  
  # Does account already exist?
  my $user = EPrints::DataObj::User::user_with_username( $session, $username );
  if( !defined $user )
  {
      # New account
      $user = EPrints::DataObj::User::create( $session, "user" );
      $user->set_value( "username", $username );
  }
  
  # Set metadata
  my $name = {};
  $name->{family} = $entr->get_value( "sn" );
  $name->{given} = $entr->get_value( "givenName" );
  $name->{honourific} = $entr->get_value( "title");
  $user->set_value( "name", $name );
  $user->set_value( "username", $username );
  $user->set_value( "email", $entr->get_value( "mail" ) );
  $user->set_value( "dept", $entr->get_value("department")  );
  $user->commit();
  
  $ldap->unbind if $ldap;
  
  return 1;
 }

Possible enhancements

Currently this script does not remove local eprints accounts from the database: when accounts get deleted from the LDAP database the corresponding local EPrints accounts sit around forever. But since login isn't possible anymore this is not a risk or of high priority.

Depending on your situation it may be enough to run some kind of cleanup script, e.g. once a year, that get's a list of all local EPrints accounts, loops over them and $user->removes all those, which cannot be found in LDAP anymore (except for those where $user_type eq 'admin', so you don't risk losing your local admins).