ldapdock

a configurable container running openLDAP

Step by step approach on how to setup and run the openLDAP server on a classic systemd-less Docker image container

note about the dockerfile and running the generated image container on FG (foreground) or BG (background): by default the dockerfile generates an image to be run in FG, it expects to be run into it and launch slapd (openLDAP server) manually; to run the image container in BG and start slapd automatically without any user intervention, uncomment the line number 31 of the dockerfile.

Creating the ldapdock image container

build ldapdock

> docker build -t ldapdock /path/to/dockerfile

after build, check the docker image has been created properly with the given REPOSITORY name

> docker images
REPOSITORY    TAG       IMAGE ID       CREATED       SIZE
ldapdock      latest    0e4a1521b346   6 hours ago   138MB

You can run into the container in an interactive way already with this command:

> docker run -h example.com -i -t ldapdock /bin/bash

If you wish (and it is recommended in development) to save the configuration and LDAP directory structure (also called LDAP database) outside of the container, run this command instead:

> docker run -h example.com -i -t -v ldap_data:/var/lib/ldap -v ldap_config:/etc/ldap/slapd.d ldapdock /bin/bash

With -h we are specifying the name of the host, we are using example.com, this is very important. -i tells docker to run in an interactive way instead of running the container in the background. -t goes in hand with -i, and allocates a tty (terminal) so we can run commands. -v mounts a volume to save information (we use one to save the data and another one to save the configuration).

Explaining DN, parentDN, CN, and DC as parameters

One of the key configuration of LDAP is our "DC" or "parent DN" and other terms, which to explain it in a pure pragmatic way, we will use some examples: we use per defect example.com as our domain, so the DC (Distinguished Name) that we would use it is "dc=example,dc=com", instead, if our domain would be for example "ideas.lab.com", the parent DN would be "dc=ideas,dc=lab,dc=com". This configuration it's very often passed with the CN (Common Name) in concatenation with the DN (Distinguished Name), and the result it's very simple, in the case of the domain example.com, it is DN: "cn=config,dn=example,dn=com", or for ideas.lab.com DN: "cn=config,dn=ideas,dn=lab,dn=com".

Inside the ldapdock image container

make sure to use the following command to start openLDAP

root@example:/# slapd -h "ldap:/// ldapi:///" -g openldap -u openldap -F /etc/ldap/slapd.d

test connectivity to slapd

root@example:/# ldapsearch -x -H ldap://localhost -b "dc=example,dc=com" -s base "(objectclass=*)"
# extended LDIF
#
# LDAPv3
# base <dc=example,dc=com> with scope baseObject
...

Create an Administrator account

In order to create users with different attributes and permits, we need to create a new admin account besides the root one that comes by default.
We will refer to the Administrator account as admin, and in a few cases, the root account as the set by default.

why is this needed? unnecesary long explanation, but just in case: in openLDAP, by default a special administrative account is created as core base to execute first hand tasks, however aside being able to bypass ACLs (Access Control Lists), and therefore any other account created, being allowed to authenthicate for operations like ldapadd, ldapmodify and ldapsearch, etc. it has not an actual entry in the dc=example,dc=com tree (our parentDN). This account it is only configured as olcRootDN in the core base directory/database, cn=config (/etc/ldap/slapd.d/'cn=config') and nothing more. It does not create the corresponding entry in any data tree, therefore the server cannot locate the full entry cn=admin,dc=example,dc=com because it does not exists. In pragmatic terms, we need to create an administrative account for our DN and our parentDN, the later being our domain name as previously explained. tl;dr cn=admin,dc=example,dc=com is only a rootDN and not a admin data entry directory which is what we need to setup Access Control Lists (ACLs) as well as setup password schemas.

Generate a password hash for our admin user

root@example:/# slappasswd -s 1234
{SSHA}yxIgYTzcuRRdlesjfWkIN6K97/8jOrZF

Create the .ldif file that will create the admin user

root@example:/# vim create_admin.ldif
dn: cn=admin,dc=example,dc=com
changetype: add
objectClass: organizationalRole
objectClass: simpleSecurityObject
cn: admin
userPassword: {SSHA}yxIgYTzcuRRdlesjfWkIN6K97/8jOrZF  # Replace with the hash of your password
description: LDAP administrator

Execute create_admin.ldif

root@example:/etc/ldap# ldapadd -x -H ldap:/// -D "cn=admin,dc=example,dc=com" -w 1234 -f /etc/ldap/create_admin.ldif
adding new entry "cn=admin,dc=example,dc=com"

Check the attributes of our new administrator user of our domain (parentDN)

root@example:/# ldapsearch -x -H ldap:/// -D "cn=admin,dc=example,dc=com" -w 1234 -b "cn=admin,dc=example,dc=com" "(objectclass=*)"
# extended LDIF
#
# LDAPv3
# base <cn=admin,dc=example,dc=com> with scope subtree
# filter: (objectclass=*)
# requesting: ALL
#
# admin, example.com
dn: cn=admin,dc=example,dc=com
objectClass: organizationalRole
objectClass: simpleSecurityObject
cn: admin
userPassword:: e1NTSEF9eXhJZ1lUemN1UlJkbGVzamZXa0lONks5Ny84ak9yWkY=
description: LDAP administrator
...

That's all, our administrator user was properly done.

Users administrative tasks

Reset root password

Build line by line, the .ldif file we will need to reset root password, starting with the following command:

root@example:/# ldapsearch -Q -LLL -Y EXTERNAL -H ldapi:/// -b cn=config '(olcSuffix=dc=example,dc=com)' dn > rootpw.ldif

which writes to the rootpw.ldif file, the current rootDN (Distinguised Name): dn: olcDatabase={1}mdb,cn=config
The next command will add the 'changetype' (modify, add, etc.) and what object are we working with:

root@example:/# echo -e 'changetype: modify\nreplace: olcRootPW: ' >> rootpw.ldif
root@example:/etc/ldap# cat rootpw.ldif
dn: olcDatabase={1}mdb,cn=config

changetype: modify
replace: olcRootPW

We run a simple sed command to delete blank lines

root@example:/# sed '/^$/d' rootpw.ldif > chrootpw.ldif
root@example:/# cat chrootpw.ldif
dn: olcDatabase={1}mdb,cn=config
changetype: modify
replace: olcRootPW

It's time to write our new password (newpasswd):

root@example:/# slappasswd -s 1234
{SSHA}2xbd33S4ZumAZW4Oks0GJidBFJYEVBPz

The last line it's our password 1234 hashed in SSHA cryptography. We will need to copy and paste it in the following command:

root@example:/# echo "olcRootPW: {SSHA}2xbd33S4ZumAZW4Oks0GJidBFJYEVBPz" >> chrootpw.ldif

The file that describes the variables needed to change our root password, chrootpw.ldif should be ready, we finally run:

root@example:/etc/ldap# ldapmodify -Q -Y EXTERNAL -H ldapi:/// -f chrootpw.ldif
modifying entry "olcDatabase={1}mdb,cn=config"

If successful, the output will show the modified entry.

Add users

create a new LDAP directory called Supergirls (LDAP OU) with the following data

root@example:/# vim add_ou.ldif
dn: ou=Supergirls,dc=example,dc=com
objectClass: organizationalUnit
ou: Supergirls

create it in our LDAP server, when asked for the root password, remember in the dockerfile by default is admin

root@example:/# ldapadd -x -D "cn=admin,dc=example,dc=com" -W -f add_ou.ldif
Enter LDAP Password:
adding new entry "ou=Supergirls,dc=example,dc=com"

verify the entry in the LDAP server

root@example:/# ldapsearch -x -LLL -b "dc=example,dc=com" "(ou=Supergirls)" dn
dn: ou=Supergirls,dc=example,dc=com

create a new LDAP password to manage our new directory, annotate both the entered plain password and the result hashed password

root@example:/# slappasswd
New password:
Re-enter new password:
{SSHA}hashedpasswd

create a .ldif file with the necessary attributes to insert in our Supergirls directory

root@example:/# vim add_user_supergirls.ldif
dn: uid=marisa,ou=Supergirls,dc=example,dc=com
objectClass: inetOrgPerson
objectClass: posixAccount
cn: Marisa
sn: Kirisame
givenName: Marisa
displayName: Marisa Kirisame
uid: marisa
uidNumber: 1001
gidNumber: 5000
homeDirectory: /home/marisa
loginShell: /bin/bash
userPassword: {SSHA}hashedpasswd
mail: marisa@example.com

insert the new user (marisa) in our Supergirls directory (LDAP OU), still using the root password admin

root@example:/# ldapadd -x -D "cn=admin,dc=example,dc=com" -W -f add_user_supergirls.ldif
Enter LDAP Password:
adding new entry "uid=marisa,ou=Supergirls,dc=example,dc=com"

verify the user (marisa) has been added to the Supergirls OU

root@example:/# ldapsearch -x -LLL -b "dc=example,dc=com" "(uid=marisa)" dn
dn: uid=marisa,ou=Supergirls,dc=example,dc=com

Modify users attributes

create a new .ldif file with the attributes we want to change
in this case we want to modify the mail marisa@example.com of the user (uid) marisa from the group (ou) Supergirls

root@example:/home# vim modify_user.ldif
dn: uid=marisa,ou=Supergirls,dc=example,dc=com
changetype: modify
replace: mail
mail: marisa.kirisame@example.com

run the modify file, when asked for the root password, remember in the dockerfile by default is admin

root@example:/home# ldapmodify -x -D "cn=admin,dc=example,dc=com" -W -f modify_user.ldif
Enter LDAP Password:
modifying entry "uid=marisa,ou=Supergirls,dc=example,dc=com"

verify the mail attribute of the user marisa has been changed to marisa.kirisame@example.com

root@example:/home# ldapsearch -x -LLL -b "dc=example,dc=com" "(uid=marisa)" mail
dn: uid=marisa,ou=Engineering,dc=example,dc=com
mail: marisa.kirisame@example.com

Modify user password

In this examples, we are changing user uid marisa from ou Supergirls password.

In order to change the password interactively (writing in the prompt when asked), we can run this command:

root@example:/etc/ldap# ldappasswd -H ldap:/// -x -D "uid=marisa,ou=Supergirls,dc=example,dc=com" -W -S "uid=marisa,ou=Supergirls,dc=example,dc=com"
New password: newpasswd
Re-enter new password: newpasswd
Enter LDAP Password: oldpasswd

newpasswd being the new password we want to use, and oldpasswd, the last password we were using for the user uid marisa.

To change the password in an non interactive (sending the password directly via the command), we can run this:

root@example:/etc/ldap# ldappasswd -H ldap:/// -x -D "uid=marisa,ou=Supergirls,dc=example,dc=com" -w newpasswd "uid=marisa,ou=Supergirls,dc=example,dc=com"
New password: 6vUj/2lE

newpasswd being the new password we want to use. We can also notice the hashed output of our new password is not a typical LDAP SSHA hash, this is due to security implementations.

Reset user password

In the likely common event that we forgot the password of an specific user, we need to reset it.
In this example we forgot the password of the user uid marisa, we can reset it with this command:

root@example:/etc/ldap# ldappasswd -H ldap:/// -x -D "cn=admin,dc=example,dc=com" -W -S "uid=marisa,ou=Supergirls,dc=example,dc=com"
New password: newpasswd
Re-enter new password: newpasswd
Enter LDAP Password: admin

Note we need to use the root password (admin by default) in the last query ("Enter LDAP Password") to reset an user's password.

Query as an specific user

we already created the user (uid) marisa, and established the user's own password using slappasswd
now we are gonna query our LDAP server using the user (uid) marisa credentials, and the password we entered during slappasswd, called plain password (plainpasswd)

root@example:/etc/ldap# ldapsearch -D uid=marisa,ou=Supergirls,dc=example,dc=com -b "dc=example,dc=com" -w plainpasswd
# extended LDIF
#
# LDAPv3
# base <dc=example,dc=com> with scope subtree
# filter: (objectclass=*)
# requesting: ALL
#

# example.com
dn: dc=example,dc=com
objectClass: top
objectClass: dcObject
objectClass: organization
o: nodomain
dc: example

# Supergirls, example.com
dn: ou=Supergirls,dc=example,dc=com
...

we can narrow this search to get only specific attributes of the user marisa, remember we are using the plainpasswd when asked

root@example:/etc/ldap# ldapsearch -D uid=marisa,ou=Supergirls,dc=example,dc=com -b "dc=example,dc=com" -w plainpasswd givenName uidNumber gidNumber homeDirectory
# extended LDIF
#
# LDAPv3
# base <dc=example,dc=com> with scope subtree
# filter: (objectclass=*)
# requesting: givenName uidNumber gidNumber homeDirectory
#

# example.com
dn: dc=example,dc=com

# Supergirls, example.com
dn: ou=Supergirls,dc=example,dc=com

# marisa, Supergirls, example.com
dn: uid=marisa,ou=Supergirls,dc=example,dc=com
givenName: Marisa
uidNumber: 1001
gidNumber: 5000
homeDirectory: /home/marisa