Configuring Existing OpenLDAP 2.4+ Directory to Accept TLS Connections

Configuring Existing OpenLDAP 2.4+ Directory to Accept TLS Connections

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This tip assumes that OpenLDAP is currently running properly on port 389 without SSL/TLS configured and that the database is being used to store the config file via cn=config.

1. Generate an SSL key pair

a. private key

openssl genrsa -out slapd.key 2048

b. self-signed certificate


openssl req -new -x509 -key slapd.key -out slapd.crt -days 1095

2. copy the certificate file and key to /etc/openldap/tls or appropriate location — be sure to modify the following LDIF if not maintaining the standard thus far in this tip

3. Create a file called tls.ldif and copy the following contents into it:

# re:  ldapmodify -x -D "cn=admin,cn=config" -w $password -f tls.ldif
dn: cn=config
changetype:  modify
add: olcTLSCACertificateFile
olcTLSCACertificateFile: /etc/openldap/tls/slapd.crt
add: olcTLSCACertificatePath
olcTLSCACertificatePath: /etc/openldap/tls
add: olcTLSCertificateFile
olcTLSCertificateFile: /etc/openldap/tls/slapd.crt
add: olcTLSCertificateKeyFile
olcTLSCertificateKeyFile: /etc/openldap/tls/slapd.key
add: olcTLSCipherSuite
olcTLSCipherSuite: HIGH:MEDIUM:+SSLv2

4. Execute the following command to modify the database, based on the contents in the LDIF, enter the password for the DN cn=admin,cn-config when prompted:

ldapmodify -x -D "cn=admin,cn=config" -W -f tls.ldif

Once that step is complete, TLS connections should succeed. To validate this assumption, execute an ldapsearch with the -ZZ flags to force a successful TLS connection.

ldapsearch -xZZ -D "cn=manager,dc=example,dc=com" -W

5. Once TLS connections have been configured and validated, configure all clients to connect via TLS.

6. The next step is to *require* TLS connections from all clients, using the following LDIF — require-tls.ldif:

dn: cn=config
changetype:  modify
add: olcSecurity
olcSecurity: minssf=256

Do not do this until clients are configured or you will risk being locked out!

7. Run ldapmodify to modify cn=config:

ldapmodify -x -D "cn=admin,cn=config" -W -f require-tls.ldif
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