OpenLDAP Directory Administration OpenLDAP

OpenLDAP Directory Administration

OpenLDAP

Table of Contents● Obtaining the OpenLDAP Distribution

● Software Requirements

● Compiling OpenLDAP 2

● OpenLDAP Clients and Servers

● The slapd.conf Configuration File

● Access Control Lists (ACLs)







Obtaining the OpenLDAP Distribution

● OpenLDAP ?

– Popular, open source LDAP-v3-compliant server

– Attractive for several reasons:● Source code is available for download● Compliant with the core LDAPv3 specifications● Available on multiple platforms, including Linux, Solaris, Mac

OS 10.2, and Windows● Continuation of original University of Michigan LDAP server

● Compiling OpenLDAP = lots of dependencies

● Try to obtain binary packages (eg. http://www.symas.com/ for Solaris & HP/UX)

● Source code: http://www.openldap.org/

http://www.symas.com/

http://www.openldap.org/







Software Requirements● OpenLDAP server will require several external software

packages:

– Support for POSIX threads (either by OS or an external library)

It is possible to compile OpenLDAP without thread support, but slurpd requires it

– SSL/TLS libraries, such as OpenSSL

http://www.openssl.org/

– Database manager library that supports DBM type storage facilities.

● Current library of choice is BerkeleyDB 4.1

http://www.sleepycat.com/● ldbm can also be used

http://www.fsf.org/

– Release 2.1 of the SASL libraries from Carnegie Mellon University

http://asg.web.cmu.edu/sasl/sasl-library.html

http://www.openssl.org/

http://www.sleepycat.com/

http://www.fsf.org/

http://asg.web.cmu.edu/sasl/sasl-library.html







Compiling OpenLDAP● Compiling:

(untar)

./configure --enable-wrappers

make depend

make

make test

make install

● Things to check when encountering problems

– (if your system supports it) Use ldd tool to verify that binaries (eg. slapd) have been compiled against correct libraries

● Change /etc/ld.so.conf and run ldconfig -v or set LD_LIBRARY_PATH

– Verify that DNS is configured correctly (reverse DNS!)

– Verify network connectivity

enables support for TCP wrappers







OpenLDAP Clients and Servers

Name Descriptionlibexec/slapd The LDAP serverlibexec/slurpd The LDAP replication helperbin/ldapaddbin/ldapmodifybin/ldapdeletebin/ldapmodrdnbin/ldapsearchbin/ldapcomparebin/ldappasswd

sbin/slapaddsbin/slapcatsbin/slapindexsbin/slappasswd

lib/libldap* The OpenLDAP client SDKlib/liblber*include/ldap*.hinclude/lber*.h

Command-line tools for adding, modifiying, and deleting entries on an LDAP server (commands support both LDAPv2 and LDAPv3)Command-line utilities for searching an LDAP directory or testing a compare A tool for changing the password attribute in LDAP entries. This tool is the equivalent of /bin/passwdTools for manipulating the local backend data store used by the slapd daemon

A simple utility to generate password hashes suitable for use in slapd.conf







The slapd.conf Configuration File● Central source of configuration information

● Used by slapd, slurpd, and related tools, such as slapcat and slapadd

● Tools like slapmodify and slapsearch use ldap.conf (not slapd.conf) for default settings

● Can be broken into two sections

– Parameters that affect overall behavior of the servers

– Parameters that relate to a specific database backend used by the slapd daemon

The slapd.conf Configuration FileSchema Files

include /etc/ldap/schema/...

corba.schema

Schema for storing Corba Objects in LDAP (RFC 2714)

core.schema

OpenLDAP required core schemas: basic LDAPv3 attributes and objects described in RFCs 2251-2256

cosine.schema

For supporting COSINE and X.500 directory pilots (RFC 1274)

inetorgperson.schema

Defined inetOrgPerson object class & attributes (RFC 2798)

java.schema

For storing Java objects (RFC 2713)

misc.schema

Miscellaneous objects (eg LDAP-based mail routing with sendmail)

nis.schema

Attributes and objects necessary for using LDAP+NIS (RFC 2307)

openldap.schema

Miscelaneous objects used by the OpenLDAP project

The slapd.conf Configuration FileLogging

loglevel 296

pidfile /var/run/slapd.pid

argsfile /var/run/slapd.args

loglevel is a set of bit flags that should be OR'ed together

Level I nformation recorded-1 All logging information0 No logging information1 Trace function calls2 Packet-handling debugging information4 Heavy trace debugging8 Connection management16 Packets sent and received32 Search filter processing64 Configuration file processing128 Access Control List processing256 Statistics for connection, operations, and results512 Statistics for results returned to cients1024 Communication with shell backends2048 Print entry parsing debug information

The slapd.conf Configuration FileSASL Options

– SASL is not needed if only simple binds will be used

– However, often useful to allow a combination of simple binds and SASL mechanisms for user connections, eg.:

● Normal users can do lookups via a simple bind● Administrators must authenticate via SASL

– slapd.conf has three SASL-related global options:● sasl-host hostname● sasl-realm string● sasl-secprops properties

– sasl-host and sasl-realm are respectively the FQDN and SASL domain used for authentication

Use sasldblistusers to dump the /etc/sasldb database

– sasl-secprops allows you to define conditions that affect SASL security properties (see next slide)

The slapd.conf Configuration FileSASL Options (cont.)

– sasl-secprops parameter values and descriptions:

Flag DescriptionNonenoplain

noactive Disables mechanisms vulnerable to active attacksnodict

noanonymous Disables mechanisms that support anonymous loginsforwardsec Requires forward secrecy between sessionspasscred Requires mechanisms that pass client credentialsminssf=factor

maxssf=factor

maxbufsize=size

Clears the default security properties (noplain,noanonymous)Disables mechanisms vulnerable to passive attacks, such as viewing network packets to examine passwords

Disables mechanisms that are vulnerable to dictionary-based password attacks

Defines the minimum security strength enforced. Possible values include: 0 (no protection), 1 (integrity protection only), 56 (allow DES encryption), 112 (allow 3DES or other string encryption methods), and 128 (allow RC4, Blowfish, or other encryption algorithms of this class)Defines the maximum security strength setting. The possible values are identical to those of minssfDefines the maximum size of the security layer receive buffer. A value of 0 disables the security layer. The default value is the maximum of INT_MAX (ie. 65536)


– Various cyrus-sasl plugins:

maxssfANONYMOUS NOPLAIN 0CRAM-MD5 NOPLAIN 0DIGEST-MD5

GSSAPI 56

KERBEROS_V4 56

LOGIN NOANONYMOUS 0PLAIN NOANONYMOUS 0SCRAM-MD5 NONE 0SRP NOPLAIN 0

SASL Mechanisms

Security Property Flags

NOPLAIN NOANONYMOUS

128 if compiled with RC4; 112 if compiled with DES; 0 if compiled with neither RC4 not DES

NOPLAIN NOACTIVE NOANONYMOUSNOPLAIN NOACTIVE NOANONYMOUS


– If you had this in slapd.conf:

– the following machanisms for authentication would be allowed:

● DIGEST-MD5● GSSAPI● KERBEROS_4

## No PLAIN or ANONYMOUS mechanisms; use DES encryptionsasl-secprops noplain,noanonymous,minssf=56## No PLAIN or ANONYMOUS mechanisms; use DES encryptionsasl-secprops noplain,noanonymous,minssf=56

The slapd.conf Configuration FileSSL/TLS Options

– Parameters:

TLSCipherSuite cipher-suite-specification

TLSCertificateFile filename

TLSCertificateKeyFile filename

The slapd.conf Configuration FileServing Up Data

– After global section: one or more database sections, eachdefining directory partition

– database directive, possible values:

bdb: BerkeleyDB 4 database manager, makes extensive use of indexing and caching; recommended OpenLDAP backend

ldbm: GNU Database Manager or Sleepycat BerkeleyDB; older implementation

passwd: Quick and dirty means of providing directory interface to the system passwd file

shell: Allows the use of alternative (external) databases

The slapd.conf Configuration FileServing Up Data (cont.)

– Example:

# Begin a new database sectiondatabase bdb

# Define the root suffix you servesuffix “dc=plainjoe,dc=org”

# Define root DN for superuser privilegesrootdn “cn=Manager,dc=plainjoe,dc=org”

# Define root DN's password: salted secure hash of 'secret'rootpw {SSHA}2aksIaicAvwc+DhCrXUFlhgWsbBJPLxy

# Directory containing the database filesdirectory /var/ldap/plainjoe.org

# Files should be created rw for the owner *only*mode 0600

# Begin a new database sectiondatabase bdb

# Define the root suffix you servesuffix “dc=plainjoe,dc=org”

# Define root DN for superuser privilegesrootdn “cn=Manager,dc=plainjoe,dc=org”

# Define root DN's password: salted secure hash of 'secret'rootpw {SSHA}2aksIaicAvwc+DhCrXUFlhgWsbBJPLxy

# Directory containing the database filesdirectory /var/ldap/plainjoe.org

# Files should be created rw for the owner *only*mode 0600







Access Control Lists● OpenLDAP ACLs are simple in syntax, yet very flexible

and powerful

● Basic idea:

WHO has ACCESS to WHAT ?

Access Control Lists (cont.)WHO has ACCESS to WHAT ?

WHO can be:

*

Any connected user, including anonymous connections

self

DN of currently connected user

anonymous

Nonauthenticated user connections

users

Authenticated user connections

Regular expression

Matches a DN or a SASL identity

Note: login name can be DN (dn=“cn=gerald carter,ou=people,dc=plainjoe,dc=org”) or SASL identity (dn=“uid=jerry,cn=gssapi,cn=auth”)

Access Control Lists (cont.)WHO has ACCESS to WHAT ? (cont.)

ACCESS can be:

write

Access to update attribute values

read

Access to read search results (eg. show all entries with a telephoneNumber of 555*)

search

Access to apply search filters (eg. are there any entries with a telephoneNumber of 555*)

compare

Access to compare attributes

auth

Access to bind (authenticate). Requires that the client send a username (DN) and some type of credentials

none

No access

Access Control Lists (cont.)WHO has ACCESS to WHAT ? (cont.)

WHAT can be:

Regular expression defining the DN of the proposed target of the ACL

Syntax is dn.targetstyle=regex

where:– targetstyle is one of base, subtree, one, or children– regex is a regular expresion representing a DN

targetstyle is used to broaden or narrow the scope (default subtree)

An LDAP search filter that confirms to RFC 2254

Syntax is filter=ldapFilter

A comma-separated list of attribute names

Syntax is attrs=attributeList

Access Control Lists (cont.)Examples

● Simple ACL granting read access to the world:

● Restrict access to the userPassword attribute

● User should be allowed to modify her own password:

access to *by * read

access to *by * read

access to attrs=userPasswordby * auth


access to attrs=userPasswordby self writeby * auth


Access Control Lists (cont.)Examples (cont.)

● ACLs are evaluated on a first-match-wins basis: more restrictive ACLs should be listed prior to more general ones

● eg.

● better:










● Assume:

– Administrative accounts are located beneath the DN ou=admins,ou=eng,dc=plainjoe,dc=org

– Normal user accounts are located beneath ou=users,ou=eng,dc=plainjoe,dc=org

– Normal users should not be allowed to see other users' passwords

– A user should be able to modify his password

– Admin users should be able to modify any user's password

● Gives:

access to dn=”.*,ou=eng,dc=plainjoe,dc=org”attrs=userPasswordby self writeby * authby dn=”.*,ou=admins,ou=eng,dc=plainjoe,dc=org” write



● This example:

● Can also be written as:



access to dn.children==”ou=eng,dc=plainjoe,dc=org”attrs=userPasswordby self writeby * authby dn.children=”ou=admins,ou=eng,dc=plainjoe,dc=org” write

access to dn.children==”ou=eng,dc=plainjoe,dc=org”attrs=userPasswordby self writeby * authby dn.children=”ou=admins,ou=eng,dc=plainjoe,dc=org” write

Documents

OpenLDAP Directory Administration OpenLDAP