Apache ESME

Wednesday Apr 13, 2011

LDAP-based Authentication with Apache ESME and Apache Directory Server

This blog was written by our new committer Vladimir Ivanov who implemented a feature that users have been wanting for a long time. 

In this blog, I'll discuss how container-managed authentication works with an LDAP server and how to connect and get additional information from it. I'll use Jetty and Apache Tomcat web servers with Apache Directory Server (ADS) 1.5.7 - a certified LDAPv3 compatible server. It is also possible to use different LDAP compatible server such as a 389 Directory Server or MS Active Directory.

An LDAP server is a directory service that contains objects organized in a hierarchical manner.

Apache Directory Server (ADS)

The ADS project page provides a detailed server installation and configuration guide, but here are the basic steps: during the installation, the default server instance will be created. The configuration settings for this instance are defined in the server.xml file as Spring bean definitions. Below is an excerpt from the configuration file that was used for this blog.

server.xml

First of all, it is necessary to create a new partition:

...

<partitions>

...

<jdbmPartition id="lester" suffix="dc=lester,dc=org" />

</partitions>

Ports that LDAP server will use are specified as tcpTransport elements:

<ldapServer id="ldapServer"

allowAnonymousAccess="false"

saslHost="ldap.example.com"

saslPrincipal="ldap/ldap.example.com@EXAMPLE.COM"

searchBaseDn="ou=users,ou=system"

maxTimeLimit="15000"

maxSizeLimit="1000">

<transports>

<tcpTransport address="0.0.0.0" port="10389" nbThreads="8" backLog="50" enableSSL="false"/>

<tcpTransport address="localhost" port="10636" enableSSL="true"/>

</transports>

</ldapServer>

The local path to the directory containing LDIF files should also be specified:

<apacheDS id="apacheDS">

<ldapServer>#ldapServer</ldapServer>

<ldifDirectory>PATH_TO_ADS_INSTALL_DIR/instances/default/ldif</ldifDirectory>

</apacheDS> 

Other configuration settings were left unchanged.

Now It is time to create the directory structure. I used the popular open source tool JXplorer for this task.

It is possible to export the directory structure from the JXplorer tool to the LDIF file — directory content in text format. Let's review the generated file.

lester.ldif

Below is a record list beginning from the top. Note that each record has specific set of object classes defined in this schema. Each object class defines specific set of attributes, for example, person class defines Surname (sn) and Given Name (givenName) attributes. One object class can extend another, for example organizationalPerson class extends person class. top is a superclass for all other classes.

Domain lester.org is the root of this hierarchy:

dn: dc=lester,dc=org

objectClass: extensibleObject

objectClass: domain

objectClass: top

dc: lester

The Organizational Unit esme is placed one level lower:

dn: ou=esme,dc=lester,dc=org

objectClass: organizationalUnit

objectClass: top

ou: esme

The Organizational Unit Groups resides under the esme Organizational Unit:

dn: ou=Groups,ou=esme,dc=lester,dc=org

objectClass: organizationalUnit

objectClass: top

ou: Groups

There is only one group esme-users on the lowest level of the hierarchy and it has the vivanov user (specified by a full path) as a unique member:

dn: cn=esme-users,ou=Groups,ou=esme,dc=lester,dc=org

objectClass: groupOfUniqueNames

objectClass: top

cn: esme-users

ou: Groups

uniqueMember: uid=vivanov,ou=Users,ou=esme,dc=lester,dc=org

The Organizational Unit Users resides under the esme organizational unit:

dn: ou=Users,ou=esme,dc=lester,dc=org

objectClass: organizationalUnit

objectClass: top

ou: Users

The user vivanov and its corresponding attributes are defined on the lowest level of the hierarchy:

dn: uid=vivanov,ou=Users,ou=esme,dc=lester,dc=org

objectClass: organizationalPerson

objectClass: person

objectClass: uidObject

objectClass: inetOrgPerson

objectClass: top

cn: vivanov

givenName: Vladimir

mail: vivanov@lester.org

ou: Users

sn: Ivanov

telephoneNumber: +7 111 222 33 44

uid: vivanov

userPassword:: cXdlcnR5

There is also a special user with administrative rights: uid=admin,ou=system (default password: secret) defined in system schema. It was used to connect to ADS from JXplorer.

Those were all basic steps necessary to configure ADS for purpose of this b log. Let's move to the configuration of the web servers.

Configuration

Before digging into the configuration details specific for each web server, let's review the common properties used to connect to the LDAP server.

First of all, it is necessary to specify the hostname / ip address and the port of our LDAP server — localhost:10389, as well as the credentials for an account that has rights to perform search operation and get attributes for users and roles in a directory tree. The special admin user described in previous section was also used for this purpose in this blog. Sometimes anonymous access is also permitted.

The next set of properties, user base and group base, specify the base context with which to lookup users and groups. For our configuration web server will search users under ou=Users,ou=esme,dc=lester,dc=org and groups under ou=Groups,ou=esme,dc=lester,dc=org paths in the directory tree accordingly.

The user id and role name attributes specify the prefix for user/group search filter. In our example, it has the uid value for users and the cn value for groups.

The uniqueMember attribute is used to check whether the user belongs to the specified group.

Now it is time to review the configuration for each of the web servers.

Note: The required lift-ldap dependency has been already included in pom.xml.

Jetty

In order to configure Jetty to use LDAP server, two additional Maven dependencies: jetty-plus and jetty-ldap-jaas should be added to the pom.xml file. Configuration of maven-jetty-plugin includes the following steps: set the JAASUserRealm as an user realm implementation and specify the ldaploginmodule as the login module name. It is also necessary to set the system property java.security.auth.login.config with the ldap-loginModule.conf value:

pom.xml

<dependency>

<groupId>org.mortbay.jetty</groupId>

<artifactId>jetty-plus</artifactId>

<version>[6.1.6,)</version>

<scope>compile</scope>

</dependency>

<dependency>

<groupId>org.mortbay.jetty</groupId>

<artifactId>jetty-ldap-jaas</artifactId>

<version>[6.1.6,)</version>

<scope>compile</scope>

</dependency>

<plugin>

<groupId>org.mortbay.jetty</groupId>

<artifactId>maven-jetty-plugin</artifactId>

<configuration>

<contextPath>/</contextPath>

<scanIntervalSeconds>0</scanIntervalSeconds>

<userRealms>

<userRealm implementation="org.mortbay.jetty.plus.jaas.JAASUserRealm">

<name>ESMERealm</name>

<loginModuleName>ldaploginmodule</loginModuleName>

</userRealm>

</userRealms>

<systemProperties>

<systemProperty>

<name>java.security.auth.login.config</name>

<value>ldap-loginModule.conf</value>

</systemProperty>

</systemProperties>

</configuration>

</plugin>

The file ldap-loginModule.conf is placed under the ESME_ROOT/server folder. It specifies login module implementation class - LdapLoginModule as well as LDAP-specific connection properties:

ldap-loginModule.conf

ldaploginmodule {

org.mortbay.jetty.plus.jaas.ldap.LdapLoginModule required

debug="true"

useLdaps="false"

contextFactory="com.sun.jndi.ldap.LdapCtxFactory"

hostname="localhost"

port="10389"

bindDn="uid=admin,ou=system"

bindPassword="secret"

authenticationMethod="simple"

forceBindingLogin="false"

userBaseDn="ou=Users,ou=esme,dc=lester,dc=org"

userRdnAttribute="uid"

userIdAttribute="uid"

userPasswordAttribute="userPassword"

userObjectClass="inetOrgPerson"

roleBaseDn="ou=Groups,ou=esme,dc=lester,dc=org"

roleNameAttribute="cn"

roleMemberAttribute="uniqueMember"

roleObjectClass="groupOfUniqueNames";

};

Note that for some environments forceBindingLogin attribute must also be set to true.

Tomcat

The only required change in the Tomcat's server.xml configuration file (compared to the changes described in the last blog) is a different realm - JNDIRealm. This realm is used to connect to LDAP server and search users/groups:

server.xml

...

<Realm className="org.apache.catalina.realm.JNDIRealm"

connectionName="uid=admin,ou=system"

connectionPassword="secret"

connectionURL="ldap://localhost:10389" debug="99"

referrals="follow"

roleBase="ou=Groups,ou=esme,dc=lester,dc=org"

roleName="cn"

roleSearch="(uniqueMember={0})"

roleSubtree="true"

userBase="ou=Users,ou=esme,dc=lester,dc=org"

userSearch="(uid={0})"

userSubtree="true"/>

LDAPVendor and ESMELdap.properties file

The web server is now configured to perform CMA. But the Servlet API makes only the user principal available for application. In order to fill ESME user's profile, additional attributes such as firstname, lastname and email are needed. We will use LDAP server to retrieve these attributes. Let's review changes in UserAuth.scala, specifically in ContainerManagedAuthModule object:

UserAuth.scala

To connect to the LDAP server from application first of all, it is necessary to create aq subclass of net.lift.ldap.LDAPVendor class:

object myLdapVendor extends LDAPVendor

All LDAP-specific connection properties are placed into a resource bundle — plaintext property file with key-value pairs. It is possible to get property values by key with the S.? method:

def myLdap : LDAPVendor = {

val ldapSrvHost = S.?("ldap.server.host")

val ldapSrvPort = S.?("ldap.server.port")

val ldapSrvBase = S.?("ldap.server.base")

val ldapSrvUsrName = S.?("ldap.server.userName")

val ldapSrvPwd = S.?("ldap.server.password")

val ldapSrvAuthType = S.?("ldap.server.authType")

val ldapSrvReferral= S.?("ldap.server.referral")

val ldapSrvCtxFactory = S.?("ldap.server.initial_context_factory")

The next step is to configure the LDAPVendor subclass with these values:

myLdapVendor.configure(Map("ldap.url" -> "ldap://%s:%s".format(ldapSrvHost, ldapSrvPort),

"ldap.base" -> ldapSrvBase,

"ldap.userName" -> ldapSrvUsrName,

"ldap.password" -> ldapSrvPwd,

"ldap.authType" -> ldapSrvAuthType,

"referral" -> ldapSrvReferral,

"ldap.initial_context_factory" -> ldapSrvCtxFactory))

myLdapVendor

}

The method getAttrs takes the username as a parameter and returns a map of [attribute name / list of attribute values] pairs (attribute in LDAP might contain more than one value) for this user. Let's review the method definition. It is possible to get attributes for user with LDAPVendor.attributesFromDn() method. It takes the distinguished name as a parameter, so it is necessary to append the prefix and the user base from the property file to the username to construct it. Note that the attributesFromDn method returns javax.naming.directory.Attributes therefore the interfaces from javax.naming.directory package must be imported correctly:

import _root_.javax.naming.directory.{Attributes, Attribute => Attr}

The shorthand Attr is used for the javax.naming.directory.Attribute because the scala.xml.Attribute trait has already been imported and placed in scope.

Then attribute's id and values are used to populate the result map.

The getAttrs method definition is shown below:

def getAttrs(who : String) : Map[String, List[String]] = {

</o:p>

val uidPrefix = S.?("ldap.uidPrefix")

val userBase = S.?("ldap.userBase")

</o:p>

var attrsMap = Map.empty[String, List[String]]

val dn = "%s=%s,%s".format(uidPrefix, who, userBase)

</o:p>

val attrs : Attributes = myLdap.attributesFromDn(dn)

if (attrs != null) {

val allAttrs = attrs.getAll();

if (allAttrs != null) {

while(allAttrs.hasMore()) {

val attribute = allAttrs.next().asInstanceOf[Attr];

var attrValues = List.empty[String]

for(i <- 0 until attribute.size()) {

attrValues ::= attribute.get(i).toString

}

attrsMap += (attribute.getID() -> attrValues)

}

}

}

attrsMap

}

The last step is to modify the performInit method. First of all, it is necessary to check if LDAP is enabled as configured in the property file. Then the values for attributes givenName, sn and mail are extracted from the map, returned via the getAttrs method call and then used to populate User instance.

def performInit(): Unit = {

...

val usr = User.createAndPopulate.nickname(username).saveMe

//find and save additional attributes in LDAP if It is enabled

val ldapEnabled = S.?("ldap.enabled")

if(ldapEnabled.toBoolean) {

val ldapAttrs = getAttrs(username)

val firstName = ldapAttrs("givenName").head

val lastName = ldapAttrs("sn").head

val mail = ldapAttrs("mail").head

usr.firstName(firstName).lastName(lastName).save

}

...

}

The ESMELdap property file is shown below. It essentially resembles connection properties in web server configuration files that we have seen previously.

ESMELdap.properties file

#This flag specifies whether LDAP should be used

ldap.enabled=true

# Hostname or IP of LDAP server

ldap.server.host=localhost

# Port of LDAP server

ldap.server.port=10389

# Base DN from the LDAP Server

ldap.server.base=ou=esme,dc=lester,dc=org

# User that has access to LDAP server to perform search operations

ldap.server.userName=uid=admin,ou=system

# Password for user above

ldap.server.password=secret

# Authentication type

ldap.server.authType=simple

# Referral

ldap.server.referral=follow

# Initial context factory class

ldap.server.initial_context_factory=com.sun.jndi.ldap.LdapCtxFactory

# Prefix for user to whom additional LDAP attributes belong, for example 'uid' or 'sAMAccountName'

ldap.cnPrefix=uid

# User base DN for user to whom additional LDAP attributes belong

ldap.userBase=ou=Users,ou=esme,dc=lester,dc=org

The last thing that must be done is to tell Lift where to look for the ESMELdap.properties file. The list of resource file names is assigned to LiftRules.resourceNames var in Boot.scala:

Boot.scala

LiftRules.resourceNames = "ESMELdap" :: "ESMECustom" :: "ESMEBase" :: "ESMEUI" :: Nil

Conclusion

We have just configured both web servers - Jetty and Tomcat - to perform authentication and authorization via LDAP. We have also improved ContainerManagedAuthModule to get additional attributes for authenticated user from LDAP with Lift LDAP API.

Links

1. Apache Directory Server: http://directory.apache.org/apacheds/1.5/

2. Jxplorer: http://jxplorer.org/

3. Jetty login modules: http://docs.codehaus.org/display/JETTY/JAAS

http://jetty.codehaus.org/jetty/jetty-6/apidocs/org/mortbay/jetty/plus/jaas/ldap/LdapLoginModule.html

4. Tomcat user realms: http://tomcat.apache.org/tomcat-6.0-doc/realm-howto.html

5. Lift API: http://scala-tools.org/mvnsites/liftweb-2.3/

Comments:

Instead of JXplorer you can of course also use another Apache product: Apache Directory Studio (http://directory.apache.org/studio)

Posted by Stefan Seelmann on April 13, 2011 at 05:01 PM UTC #

Resorce bundle was misused in this article. Lift's net.liftweb.util.Props class should have been used instead. I moved LDAP settings to default.props. Follwoing changes have been applied to UserAuth class: -To check if LDAP is enabled val ldapEnabled = Props.getBool("ldap.enabled") openOr false -To get other string properties: val ldapSrvHost = Props.get("ldap.server.host") openOr "" Thanks Derek Chen-Becker who pointed to this issue in Lift Google Group.

Posted by Vladimir Ivanov on April 15, 2011 at 08:02 AM UTC #

??? ?? ?????? ?????????, ????? ? ???? ??? ??????

Posted by Inquisitor on April 28, 2011 at 08:51 AM UTC #

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