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Project:Infrastructure/LDAP Guide

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This is a guide to using the Gentoo Infrastructure LDAP system for developers, recruiters and administrators.

Key Concepts

Introduction

LDAP stands for Lightweight Directory Access Protocol, a lightweight client-server protocol for accessing directory services. LDAP directory service is based on a client-server model. One or more servers contain the data making up the LDAP directory tree. An LDAP client connects to an LDAP server and requests information. The server responds with the data or points the client to another source (typically another LDAP server).

Just like a database, an entry in LDAP consists of fields of data or 'Attributes'. This collection of attributes is called a 'Schema'. This guide will explain which attributes are available, who can change them and give role based examples for modifying the Gentoo LDAP Schema.

When a developer accesses a resource, like dev.gentoo.org (woodpecker.gentoo.org), the resource acts as an LDAP client and queries the LDAP server (ldap1, ldap2, ldap3, ldap4) to see if that user is in the database and authorized for access.

LDAP Access Levels

LDAP is used by Gentoo to secure the infrastructure. Gentoo resources are spread across the globe and LDAP gives us a central location to manage them. There are four levels of access: anonymous, user, recruiter and infra that are used to control what can be changed in the LDAP database. These are controlled via special values in the gentooAccess attribute.

You must connect or bind to the LDAP database either anonymously, or as a known user. Binding anonymously will always grant only the anonymous level, while binding as a known user will grant you the level based on your user and potentially where you are connecting from.

The anonymous level is used for simple read only informational queries. All developers and staff can bind to LDAP as anonymous. If you don't specify a mode when you bind, anonymous is assumed.

The user level is used to add or change information in your own LDAP record. Things like your latitude and longitude, ssh public key and so on. All users can access the user level, by binding as themselves with the mode specified, and providing their password.

The recruiter level enables recruiters to add new users, and perform some administrative changes to users.

The infra level enables the infrastructure team full power over LDAP, and is additionally protected by only being available from ldap1.gentoo.org.

Note
All write operations performed by infra must be performed on ldap1.gentoo.org. Normal user and recruiter write operations may be performed on any LDAP-connected Gentoo box, however it is strongly recommended that you use dev.gentoo.org.

Gentoo LDAP Implementation

LDAP Servers

Currently we have four LDAP servers available. The master server and three slave servers. The master LDAP server is reachable at ldap1.gentoo.org. The slave servers are ldap2.gentoo.org, ldap3.gentoo.org, ldap4.gentoo.org and they connect every 60 seconds to the master to replicate changes from the master.

Every update operation must be done on ldap1.gentoo.org, if an update (which means writing some entry) is performed on the slave a referral to the master is issued. This is transparently handled and all attempts to update against the slave will be redirected to the master. Connections are validated via TLS + password. The password is your dev one and is the same for all LDAP-aware boxes.

We use a custom script, perl_ldap that uses Net::LDAP, for accessing and modifying the database, it allows only a predefined set of actions but it should cover 95% of the cases. In the following chapters we explain how to use it.

Note
dev.gentoo.org is currently using ldap2.gentoo.org as its first server so any update you do could take up to 60 seconds for being seen on dev.gentoo.org. We usenscd (Name Service Caching Daemon) to cache negative and positive lookups. This means that your changes may not become active for some time. If you need to force the change we can restart nscd for you. Ask in #gentoo-infra for help with this. Additionally, we use nsscache to provide resiliency against LDAP servers being temporarily unavailable for NSS lookups, but we do NOT keep local copies of SSH keys.

Available Attributes

The following attributes are included in the Gentoo Schema. Note the 'Access Level' needed to write each attribute. Anonymous reading is allowed unless otherwise noted. Required fields are emphasised.

Attribute Name Access Level Description Type Format
birthday user (not globally readable) developer birthday single, optional UTF-8
gentooAccess infra, top level recruiters only developer access level multiple, required UTF-8
gentooAlias infra, recruiters alternate names for this developer multiple, optional UTF-8
gentooDevBug infra, recruiters (not globally readable) bug numbers for any recruitment, retirement or developer relations bugs multiple, optional integer
gentooGPGFingerprint, gpgfingerprint user GPG key fingerprint multiple, optional UTF-8
gentooGPGkey, gpgkey user GPG key uid multiple, required UTF-8
gentooIM user instant messaging ID multiple, optional UTF-8
gentooJoin infra, recruiters developer join date multiple, required UTF-8
gentooLatitude, lat user latitude coordinate single, optional signed decimal string
gentooLocation user developer location single, required UTF-8
gentooLongitude, lon user longitude coordinate single, optional signed decimal string
gentooMentor infra, recruiters username of mentors multiple, optional UTF-8
gentooRetire infra, recruiters developer retirement date multiple, optional UTF-8
gentooRoles user developer projects single, required UTF-8
gentooSPF user developer SPF record single, optional ASCII
gentooStatus infra, recruiters developer status single, required UTF-8
sshPublicKey user OpenSSH public key multiple, required UTF-8
Note
All dates must be formatted as ISO8601, YYYY/MM/DD.

The following attributes were in use at some point in the past, but have been retired: gentooHerd/herd, gentooAltMail/altMail, gentooForumsUID/forumsUID.

Additionally, we use a number of standard LDAP schemas for user records: inetOrgPerson, organizationalPerson, person, posixAccount, shadowAccount. Some of the attributes in these schemas are listed below.

Attribute Name Access Level Description Type Format
mail user alternative email addresses multiple, required UTF-8
cn, sn, givenName recruiters real name of developer single, required UTF-8
gecos recruiters real name of developer for script usage single, required ASCII, 7-bit clean
initials recruiters real name of developer single, optional UTF-8
loginShell user login shell, change with chsh single, required ASCII
userPassword user password, change with passwd ONLY single, required ASCII, hashed


LDAP management with perl_ldap

These are the main concepts of the perl_ldap script used for user administration. Invoking perl_ldap without arguments shows a nice help. Your own LDAP password is required when binding.

The script is the infra supported method for managing entries, nothing prevents you from using any LDAP browser you like for modifying your attributes. If you like to use something else, ask infra for connection details but keep in mind that we won't support and/or troubleshoot other browser's issues.

The following are the most common options.

  • -b MODE used to bind to the LDAP server. If you don't specify user, the script will default to anonymous and be read only.
  • -s <username> shows the entire LDAP record for the user username
  • -S ATTRIBUTE searches for a specific attribute across all users
  • -M ATTRIBUTE NEWVALUE <username> overwrites the value of an attribute for the specified user
  • -C ATTRIBUTE NEWVALUE <username> creates a new attribute for the specified user
  • -E ATTRIBUTE OLDVALUE <username> erases an attribute

Examples

Users

Gentoo Developers and Staff members (recruiters and infra please refer to the following sections) can update their LDAP record directly. Here are examples of the most commonly changed attributes. The most common error is using a actual username in place of the -b MODE argument, which takes user as the parameter.

Show attributes for a user entry (substitute <username> for an actual user name)
user $ perl_ldap -s <username>
Binding as 'user' will show additional information
user $ perl_ldap -b user -s <username>


Change your roles
user $ perl_ldap -b user -M gentooRoles "<role string>" <username>


Change your GPG key (substitute <*keyid> with your GPG key ID, with the leading 0x included)
user $ perl_ldap -b user -C gentooGPGkey "<newkeyid>" <username>
user $ perl_ldap -b user -E gentooGPGkey "<oldkeyid>" <username>


Add a new public SSH key (substitute 'pubkey' with the path to your public SSH key. ex: "~/.ssh/id_dsa.pub")
You should have one sshPublicKey attribute per key! No newlines! Only replace <username>, not "user"
user $ perl_ldap -b user -C sshPublicKey "$(cat pubkey)" <username>
Erase an old public SSH key
user $ perl_ldap -b user -E sshPublicKey "$(cat oldpubkey)" <username>


Change your LDAP password
To change your password, simply use the normal passwd command on any LDAP-enabled server.
Do not use perl_ldap to change your password, as it does not perform any password hashing.
user $ passwd


Change your login shell
To change your login shell, simply use the normal chsh command on any LDAP-enabled server.
If you want to use a shell other than bash, ask infra about it's availability on other machines
user $ chsh


Change your SPF rules
user $ perl_ldap -b user -M gentooSPF "<SPF string>" <username>

Recruiters

Recruiters can change their own attributes or those of another user. You must bind as recruiters to change any attributes including your own. The following examples show how to change attributes for other users. To change your own attributes use the examples from the "users" section above but bind as a recruiter.

When dealing with users that belong to a sub-OU the -o OU option must be used, this will be clarified in the examples. The command -o OU must be used if the target user belongs to a sub-OU.

The following examples will show you how to change attributes for users, recruiters and infra. All write operations performed by infra against another user must be performed on dev.gentoo.org (woodpecker.gentoo.org).

Some attributes, like sshPublickey, and mail, allow multi-values. To append an additional value to the exiting ones use -C. You may not use -M with multi-valued attributes.

Modify (overwrite) an existing single-instance attribute for a user
user $ perl_ldap -b user -M gentooLocation "new location" <username>
Modify (overwrite) an existing multiple-instance attribute for a user
user $ perl_ldap -b user -C gentooGPGkey "<newkeyid>" <username>
user $ perl_ldap -b user -E gentooGPGkey "<oldkeyid>" <username>
Delete an attribute for a user
user $ perl_ldap -b user -E mail "myoldaddress@example.com" <username>


Add a new user (infra, recruiters)
user $ perl_ldap -b user -A <username>
Delete a user (infra)
user $ perl_ldap -b user -D <username>


Create or modify multi-value attributes
Create a new attribute while preserving the existing ones. Use the command multiple times to add addtional attributes
user $ perl_ldap -b user -C mail "myaltaddress@example.com" <username>
user $ perl_ldap -b user -C mail "backup@example.com" <username>


Reset a user password
Only available to senior recruiters and infrastructure admins in the useradmin group on woodpecker, as well as either the recruiters or infra-ldapadmin groups in LDAP. You will be prompted for YOUR password. The new user password will NOT be shown to you, it will only be placed in /home/<username>/passwd.
user $ sudo /usr/local/bin/newpasswd <username>

Infra

Infra can change their own attributes or those of another user. You must bind as user to change any attributes, including your own. To change your own attributes use the examples from the "users" section above from any LDAP-aware machine. To change another users record, you must be using perl_ldap from ldap1.gentoo.org (duck.gentoo.org).

The attribute gentooAccess controls which boxes a user can login to. Only infra and a few selected recruiters are allowed to create and modify this multi-value attribute. The FQDN must be used (ex. roadrunner.gentoo.org). Some special values also exist: infra.group, infra-ldapadmin.group, infra-cvsadmin.group, infra-system.group, recruiters.group.

External Resources

Acknowledgements

We would like to thank the following authors and editors for their contributions to this guide:

  • Andrea Barisani
  • Robin H. Johnson
  • Luis Medinas
  • Curtis Napier