LDAP

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LDAP Authentication

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 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

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!
# Tip: remove the set-password priviledge from users and editors in
# user_roles.pl. Also consider removing edit-own-record and 
# change-email.
#
use Net::LDAP; # IO::Socket::SSL also required
use Net::LDAP::Util;

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

 my $user = $repo->user_by_username( $username );
 return unless $user;

 $username = $user->value( "username" );

 my $user_type = $user->get_type;
 if( $user_type eq "admin" )
 {
  # internal authentication for "admin" type
  return $repo->database->valid_login( $username, $password );
 }

 # LDAP authentication for "user" and "editor" types
 #
 # LDAP hostname (and port if not the default)
 my $ldap_host = "ldap.yourdomain.ac.uk";
 #my $ldap_host = "ldap.host.name:1234";
 #my $ldap_host = "ldaps://ldap.host.name"; # if server supports LDAPS

 # Distinguished name for this user
 # The distinguished name is a unique name for an LDAP entry.
 # e.g. "cn=John Smith, ou=staff, dc=eprints, dc=org"
 # You will need to derive this from the username or user metadata
 my $ldap_dn = sprintf("uid=%s,ou=People,dc=example,dc=org",
  Net::LDAP::Util::escape_dn_value($username)
 );

 my $ldap = Net::LDAP->new ( $ldap_host, version => 3 );
 unless( $ldap )
 {
  $repo->log( "LDAP error: $@" );
  return;
 }

 # Start secure connection (not needed if using LDAPS)
 my $ssl = $ldap->start_tls( sslversion => "sslv3" );
 if( $ssl->code() )
 {
  $repo->log( "LDAP SSL error: " . $ssl->error() );
  return;
 }
 # Check password
 my $mesg = $ldap->bind( $ldap_dn, password => $password );
 if( $mesg->code() )
 {
  return;
 }

 return $username;
}
# Advanced LDAP Configuration
#
# 1. It is also possible to define additional user types, each with a different
# authentication mechanism. For example, you could keep the default user, 
# editor and admin types and add ldapuser, ldapeditor and ldapadmin types with
# LDAP authentication - this would suit an arrangement where internal staff are 
# authenticated against the LDAP server but user accounts can still be granted 
# to external users.
#
# 2. Sometimes the distinguished name of the user is not computable from the 
# username. You may need to use values from the user metadata (e.g. name_given,
# name_family):
#
#       my $name = $user->get_value( "name" );
#       my $ldap_dn = $name->{family} . ", " . $name->{given} .", ou=yourorg, dc=yourdomain";
#
# or perform an LDAP lookup to determine it (more complicated):
#
#       my $base = "ou=yourorg, dc=yourdomain";
#       my $result = $ldap->search (
#               base    => "$base",
#               scope   => "sub",
#               filter  => "cn=$username",
#               attrs   =>  ['DN'],
#               sizelimit=>1
#       );
#
#       my $entr = $result->pop_entry;
#       unless( defined $entr )
#       {
#               return 0;
#       }
#       my $ldap_dn = $entr->dn
#
# Alternatively, you could store the distinguished name as part of the user 
# metadata when the user account is imported              print STDERR "LDAP SSL error: " . $ssl->error() . "\n";

After editing restart Apache.


LDAP Import

You can use the update_users script and apply the following patch to make it work with eprints3: 

--- update_users.orig   2007-04-23 16:22:26.000000000 +0200
+++ update_users    2007-04-24 21:16:40.000000000 +0200
@@ -1,6 +1,6 @@
-#!/usr/bin/perl -w -I/opt/eprints2/perl_lib
+#!/usr/bin/perl -w -I/opt/eprints3/perl_lib

-use EPrints::User;
+use EPrints::DataObj::User;
 use EPrints::Session;
 use Net::LDAP;
 use strict;
@@ -16,6 +16,7 @@

 # Start connection
 my $ldap = Net::LDAP->new( "ldap.host.name", version => 3 );
+$ldap->start_tls();
 unless( $ldap )
 {
    print STDERR "LDAP error: $@\n";
@@ -74,7 +75,7 @@
        # New account
        if( $forreal )
        {
-           $user = EPrints::User::create_user( $session, "ldapuser" );
+           $user = EPrints::DataObj::User::create( $session, "user" );
            $user->set_value( "username", $username );
            print "CREATING: $username\n";
        }
@@ -118,7 +119,7 @@
        print "FAMILY = " . $entr->get_value( "sn" ) . "\n";
        print "GIVEN = " . $entr->get_value( "givenName" ) . "\n";
        print "EMAIL = " . $entr->get_value( "mail" ) . "\n";
-       print "DN = " . $entr->get_value( "distinguishedName" ) . "\n";
+       print "DN = " . $entr->dn . "\n";

    }

LDAP Authentication with On-Demand Creation of Users

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

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

Most of the code is from the default user_login.pl and from the update_users script (which does not seem to exist anymore, but code & text below seem to have been written by User:Sp not later than May 7th 2007).

Be sure to only use this over HTTPS! 

$c->{check_user_password} = sub {
   my( $session, $username, $password ) = @_;
   
   # LDAP authentication for "user", "editor" and "admin" types (roles)
   
   use Net::LDAP; # IO::Socket::SSL also required
   
   # LDAP tunables
   my $ldap_host = "ldap.example.org";
   my $base      = "dc=example,dc=org";
   my $dn        = "cn=someProxyAccount,ou=accounts,$base";
   
   my $ldap      = Net::LDAP->new ( $ldap_host, version => 3 );
   unless( $ldap )
   {
       print STDERR "LDAP error: $@\n";
       return 0;
   }
   
   # Start secure connection (not needed if using LDAPS)
   my $ssl = $ldap->start_tls();
   if( $ssl->code() )
   {
       print STDERR "LDAP SSL error: " . $ssl->error() . "\n";
       return 0;
   }
   
   # Get password for the search-bind-account
   my $repository = $session->get_repository;
   my $id         = $repository->get_id;
   my $ldappass   = `cat /opt/eprints3/archives/$id/cfg/ldap.passwd`;
   chomp($ldappass);
   
   my $mesg = $ldap->bind( $dn, password=>$password );
   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",
       scope   => "sub",
       filter  => "(&(uid=$username)(objectclass=inetOrgPerson))",
       attrs   =>  ['1.1', 'uid', 'sn', 'givenname', 'mail'],
       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;
   }
   my $ldap_dn = $entr->dn;
   
   # Check password
   my $mesg = $ldap->bind( $ldap_dn, password => $password );
   if( $mesg->code() )
   {
       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" );
   $user->set_value( "name", $name );
   $user->set_value( "username", $username );
   $user->set_value( "email", $entr->get_value( "mail" ) );
   $user->commit();
   
   $ldap->unbind if $ldap;
   
   return 1;
}

Things to note

  • This script uses 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.

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).

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