Category: Work

Creating an LDAP Addressbook / Directory

This article will describe my experiences in creating a read-only LDAP address book (with Thunderbird as a proof of concept); also known as a corporate directory. This is written by someone who has (to put it mildly) hated LDAP for years and dies a little every time he reads an introduction to LDAP that describes it in terms of DNS.

There is one important point to make before we start – while these instructions should apply to any *nix distribution, it uses OpenLDAP/slapd version 2.4 which uses the newer runtime dynamic configuration engine. All of the below performed on Ubuntu 12.10.

Installing OpenLDAP is as easy as (root user is assumed in all of the following):

apt-get install slapd ldap-utils

As part of this process, you’ll be asked to enter an admin password – record this as it will be stored in hashed format.

You can immediately run some LDAP queries to test / get to know your system:

  • Dump your entire configuration:
ldapsearch -Y EXTERNAL -H ldapi:/// -b cn=config
  • List all configuration objects:
ldapsearch -Q -LLL -Y EXTERNAL -H ldapi:/// -b cn=config dn
  • List all installed schemas:
ldapsearch -Q -LLL -Y EXTERNAL -H ldapi:/// -b cn=schema,cn=config dn

In the output from the last command, you’ll see core, cosine, nis and inetorgperson. These are all we need for an address book directory. If you are so inclined, there is a published but neglected schema for Thunderbird specifically but it is not a standard and those fields may not (and probably will not) be supported by other clients.

One thing you might want to do before you start is up the logging level (from none by default) as follows. Don’t forget to change it back when you’re up and running as your logs will fill up fast.

cat <ldapmodify -Y EXTERNAL -H ldapi:///
dn: cn=config
changetype: modify
replace: olcLogLevel
olcLogLevel: 296
EOF

The installation will have created an organisation object based on your domain (or nodomain). E.g.

 ldapsearch -Q -LLL -Y EXTERNAL -H ldapi:/// -b dc=nodomain
dn: dc=nodomain
objectClass: top
objectClass: dcObject
objectClass: organization
o: nodomain
dc: nodomain

dn: cn=admin,dc=nodomain
objectClass: simpleSecurityObject
objectClass: organizationalRole
cn: admin
description: LDAP administrator

You can find out what domain yours is under by examining the olcSuffix field of the output of:

ldapsearch -Q -LLL -Y EXTERNAL -H ldapi:/// -b olcDatabase={1}hdb,cn=config

You may want to modify this to suit or add new objects. We’re going to add new objects – which will work fine as long as the new olcSuffix does not conflict with the output from the above.

Let’s start with creating a database for our directory. First we need a directory on the filesystem:

mkdir -p /var/lib/ldap/opensolutions
chown openldap: /var/lib/ldap/opensolutions

Now create a file (say db-create.ldif) with something like:

# Database creation
dn: olcDatabase=hdb,cn=config
objectClass: olcDatabaseConfig
objectClass: olcHdbConfig
olcDatabase: hdb
olcSuffix: dc=opensolutions,dc=ie
olcDbDirectory: /var/lib/ldap/opensolutions
olcRootDN: cn=admin,dc=opensolutions,dc=ie
olcRootPW: gOeBTo5vfBdUs
olcDbConfig: set_cachesize 0 2097152 0
olcDbConfig: set_lk_max_objects 1500
olcDbConfig: set_lk_max_locks 1500
olcDbConfig: set_lk_max_lockers 1500
olcDbIndex: cn,sn,uid,mail pres,eq,approx,sub
olcDbIndex: objectClass eq
olcLastMod: TRUE
olcDbCheckpoint: 512 30
olcAccess: to attrs=userPassword 
  by dn="cn=ldapadmin,dc=opensolutions,dc=ie" write 
  by anonymous auth 
  by self write 
  by * none
olcAccess: to attrs=shadowLastChange 
  by self write 
  by * read
olcAccess: to dn.base="" by * read
olcAccess: to * 
  by dn="cn=admin,dc=opensolutions,dc=ie" write 
  by * read

And instruct LDAP to create the database:

ldapadd -Y EXTERNAL -H ldapi:/// -f db-create.ldif

The above creates a new LDAP database with some useful indexes. You can ignore the olcAccess for now as we’ll come back and address this later. What is above is fairly typically of a default installation.

Now, we need to add an organization object, an admin user to manage that (i.e. add, edit and remove entries from the corporate database) and an organisationalUnit object to hold our staff information. Create a file (say opensolutions.ldif) containing:

# Organisation object
dn: dc=opensolutions,dc=ie
dc: opensolutions
description: Open Solutions Corporate Directory
objectClass: top
objectClass: dcObject
objectClass: organization
o: Open Source Solutions Limited

# Admin user
dn: cn=ldapadmin,dc=opensolutions,dc=ie
objectClass: simpleSecurityObject
objectClass: organizationalRole
cn: ldapadmin
description: Corporate Directory Administrator
userPassword: Jh90Ckb.c.Tp6

# Unit for our corporate directory
dn: ou=people,dc=opensolutions,dc=ie
ou: people
description: All people in Open Solutions
objectclass: organizationalUnit

And add these objects to the database:

ldapadd -x -D cn=admin,dc=opensolutions,dc=ie -W -f opensolutions.ldif

Note the password is as specified in the database creation object (ie. gOeBTo5vfBdUs in this case).

A quick work on security and access control. By default, anonymous users / anyone can read all your entries. If you are publishing a public directory, this may be okay. If not, create and auth.ldif file with (for example):

dn: olcDatabase={2}hdb,cn=config
changetype: modify
replace: olcAccess
olcAccess: {0}to attrs=userPassword,shadowLastChange
  by dn="cn=ldapadmin,dc=opensolutions,dc=ie" write
  by self read
  by anonymous auth
  by * none
olcAccess: {1}to dn.subtree="dc=opensolutions,dc=ie"
  by dn="cn=ldapadmin,dc=opensolutions,dc=ie" write
  by users read

And apply it with:

ldapmodify -Y EXTERNAL -H ldapi:/// -f auth.ldif

This will:

  • allow access to user password fields for authentication purposes (not for reading);
  • allow any authenticated user to read the corporate directory;
  • allow the ldap admin to make changes;
  • deny all other access to this database (implicit rule).

See OpenLDAP’s Access Control page for more information.

Now, let’s add two sample entries. Create a file people.ldif with:

dn: cn=Barry O'Donovan,ou=people,dc=opensolutions,dc=ie
objectClass: inetOrgPerson
uid: barryo
sn: O'Donovan
givenName: Barry
cn: Barry O'Donovan
cn: barry odonovan
displayName: Barry O'Donovan
userPassword: testpw123
mail: sample-email@opensolutions.ie
mail: sample-email@barryodonovan.com
o: Open Solutions
mobile: +353 86 123 456
title: Chief Packet Pusher
initials: BOD
carlicense: HISCAR 123
ou: Computer Services

dn: Joe Bloggs,ou=people,dc=opensolutions,dc=ie
objectClass: inetOrgPerson
uid: joeb
sn: Bloggs
givenName: Joe
cn: Joe Bloggs
displayName: Joe Bloggs
userPassword: testpw124
mail: joeb@opensolutions.ie
o: Open Solutions
title: Chief Coffee Maker
ou: Kitchen

Add these to the directory using the ldapadmin user:

ldapadd -x -D "cn=ldapadmin,dc=opensolutions,dc=ie" -w Jh90Ckb.c.Tp6 -f people.ldif

You can test this with a couple of searches:

ldapsearch -xLLL -D "cn=Barry O'Donovan,ou=people,dc=opensolutions,dc=ie" -w testpw123 \
    -b dc=opensolutions,dc=ie
ldapsearch -xLLL -D "cn=Barry O'Donovan,ou=people,dc=opensolutions,dc=ie" -w testpw123 \
    -b ou=people,dc=opensolutions,dc=ie mail=sample-email@opensolutions.ie

slapd will listen on all interfaces on the standard port (389) when installed on Ubuntu. So, to test, we turn to Thunderbird:

  1. Open the address book (e.g. Tools -> Address Book)
  2. Add a new directory (File -> New -> LDAP Directory…)
  3. In the General tab (assuming we’re setting up Barry O’Donovan’s Thunderbird), set:

Name: Corporate Directory (whatever you like)
Hostname: 127.0.0.1 (or as appropriate)
Base DN: ou=people,dc=opensolutions,dc=ie
Port number: 389
Bind DN: cn=Barry O’Donovan,ou=people,dc=opensolutions,dc=ie

  1. In the Advanced tab:

Don’t return more than 100 results – change if you wish

Scope: Subtree

Login method: Simple

  1. Click okay to save the settings
  2. Right click on the directory in the left pane and select Properties
  3. Test by going to the Offline tab and click Download Now
  4. Enter your password (and use the password manager) – password is as per the person object above and so in this case: testpw123
  5. Test by typing Joe into the search bar on the top right
  6. Joe Bloggs should appear in the results.

Congratulations! You have a corporate directory.

Next Steps

References

For OpenVPN Fans – Optimising for GE Networks

I came across this article today which discusses OpenVPN optimisations for Gigebit Ethernet networks.

http://community.openvpn.net/openvpn/wiki/Gigabit_Networks_Linux

It also shows the phenomenal improvement that can be made thanks to the AES-NI instruction set on newer Intel and AMD chips.

Git Web Applications (aka GitHub Alternatives)

I’ve been through the mill with a few of these and it’s a growing list of options. I should start by saying that I love GitHub and use it regularly for a large number of projects (including some of my own, some for my company and some for my customers). The only problem I have with GitHub is that I just haven’t made the jump to trust it with our proprietary code – the primary asset of the company. Particularly after a high profile security breech.

Now, nothing I’ve come across yet comes close to GitHub. But two we use daily have good matching features:

  • Gitorious –  whether they intended it or not, it’s a good clone of GitHub but always a little behind on features. It’s also a Ruby on Rails application and the documentation is getting far better. When we started, it was pretty… shite, to be honest. Installing and upgrading was a pain. They have addressed this with http://getgitorious.com/ which includes a virtual appliance for VirtualBox so you can be up and running in minutes.
  • Atlassian Stash – if you’re a small team (<= 10 users) then this could be for you. Installation is pretty easy, it looks great, is very fast (over HTTP/S, but it’s inbuilt SSH client is extremely slow) and is very easy to use. Pull requests are also done really really well. It’s a full Java webapp so it does require some CPU and memory. For <= 10 users, my definite favorite. Thereafter though it gets expensive – e.g. for up to 25 users you’ll fork out $1,800 / annum. That’s not entirely unaffordable but if you’re using Stash, then you may also be using their other products such as Jira, Confluence, Bamboo, Fisheye and Crucible. Now that adds up to a hefty bill!

One’s I have not tested and so cannot speak authoritively on include:

  • GitLab – Looks like a very interesting alternative.
  • RhodeCode – they say it will “change the way you manage your code”.
  • Gitolite – a quick look at the available information for this definitely puts it in the also ran category. There’s no polish or anything nice to entice one to even try it.
  • Gitosis – in their own words: “Manage git repositories, provide access to them over SSH, with tight access control and not needing shell accounts”. The project appears dead.

 

Apple OS X as an NFS Server (with Linux Clients)

For a customer, I had to set up a Linux-based virtualised environment on a MacBook Pro using VirtualBox. This environment included making a couple of 8TB external hard drives available under NFS to the Linux hosts.

In all fairness, what better use can one put OS X to than to virtualise Linux?!?  Just kidding fanboys… well, sort of 😉

Let’s begin with a quick description of the environment:

  • A MacBook Pro (MBP) with OS X 10.8.2
  • VirtualBox with it’s own network (MBP: 192.168.56.1/24) for NFS as well as bridged adapters for general Internet access;
  • Multiple external HDDs – for simplicity, let’s just do one here which is mounted under /Volumes/DATA-1.

We want to export the DATA-1 volume to the Linux clients. That bit’s actually not too hard (see below), the main issue is we needed to match what on Linux is call no_root_squash – i.e. so the root user on the Linux clients would have root access to the NFS shares. That bit was harder.

I’ll assume root access / sudo use in the following commands.

To configure NFS, we edit / create /etc/exports (e.g. nano /etc/exports) such as:

/Volumes/DATA-1 -maproot=root:wheel -network 192.168.56.0 -mask 255.255.255.0

In other words:

  • export /Volumes/DATA-1
  • map the clients root user to local root user and the clients root group to local group wheel (gid = 0)
  • allow the export to be accessed by any host on the private VirtualBox network.

With that entry, NFS can be enabled at boot and started via:

nfsd enable
nfsd start

On a Linux client, this can then be mounted at boot with an /etc/fstab entry:

192.168.56.1:/Volumes/DATA-1 /mnt/data-1 nfs defaults 0 0

The problem was that no matter what variation of options I used, I could not get root access from the Linux clients.

The answer came by chance when I glanced an odd mount option on the external HDD:

/dev/disk2s2 on /Volumes/DATA-1 (hfs, NFS exported, local, nodev, nosuid, journaled, noowners)

noowners? What pray-tell is this? The internet provided some insight:

In Leopard, due to an unfortunate design decision by Apple, “admin” authentication is now required to make this change (no noowners) and non-admin users are no longer able to use “Get Info” to change this setting, even on devices they own and have mounted themselves.

An unfortunate design decision indeed. The temporary solutions is to execute:

mount -u -o owners /Volumes/DATA-1

Thereafter, I now have root access / effective UID from the Linux clients. This of course needs to be entered each time – if someone has a more permanent solution, I’m all ears (see below for a cron script I have implemented for this).

Just as an aside, we have a lot of NFS activity which required some tuning. First, additional NFS threads by adding nfs.server.nfsd_threads=16 to /etc/nfs.conf (execute nfsd restart after that). I’ve also added the following line to /etc/rc.local:

sysctl -w kern.aiomax=64 kern.aioprocmax=32 kern.aiothreads=4

Cron Script for Automatically Removing noowners

As mentioned above, removing this mount option every time you connect these HDDs is damn annoying at best and error prone at worst. I have a script for this now which I locate in /var/root/bin/mount-check.sh which is:

#! /bin/bash

NOOWNERS=`/sbin/mount | grep "/Volumes/DATA-1" | grep noowners | wc -l`

if [[ "X${NOOWNERS//[[:space:]]/}X" = "X1X" ]]; then
    /sbin/mount -u -o owners /Volumes/DATA-1;
fi

This is then executed via a new line in /etc/crontab:

* * * * *    root    /var/root/bin/mount-check.sh

 

Monitoring SSL Certificate Expiry Dates with Nagios

It is good practice to separate Nagios checks of your web server being available from checking SSL certificate expiry. The latter need only be run once per day and should not add unnecessary noise to a more immediately important web service failure.

To use check_http to monitor SSL certificate expiry dates, first ensure you have a daily service definition – let’s call this service-daily. Now create two service commands as follows:

define command{
    command_name check_cert
    command_line /usr/lib/nagios/plugins/check_http -S \
        -I $HOSTADDRESS$ -w 5 -c 10 -p $ARG1$ -C $ARG2$
}

define command{
    command_name check_named_cert
    command_line /usr/lib/nagios/plugins/check_http -S \
        -I $ARG3$ -w 5 -c 10 -p $ARG1$ -C $ARG2$
}

The second is useful for checking named certificates on additional IP addresses on web servers serving multiple SSL domains.

We can use these to check SSL certificates for POP3, IMAP, SMTP and HTTP:

define service{
    use service-daily
    host_name mailserver
    service_description POP3 SSL Certificate
    check_command check_cert!993!21
}

define service{
    use service-daily
    host_name mailserver
    service_description IMAP SSL Certificate
    check_command check_cert!995!21
}

define service{
    use service-daily
    host_name mailserver
    service_description SMPT SSL Certificate
    check_command check_cert!465!21
}

define service{
    use service-daily
    host_name webserver
    service_description SSL Cert: www.example.com
    check_command check_named_cert!443!21!www.example.com
}

define service{
    use service-daily
    host_name webserver
    service_description SSL Cert: www.example.net
    check_command check_named_cert!443!21!www.example.net
}

Nagios Plugin for Checking Backups via rsnapshot

We’ve just added a check_rsnapshot.php script to our nagios-plugins bundle on Github. This script will verify rsnapshot backups via Nagios using a number of checks / tests:

  • minfiles – checks the number of files in a snapshot against a minimum expected number;
  • minsize – checks the size of a snapshot against a minimum expected size;
  • log – parses the rsnapshot log to ensure the most recent runs for each retention period completed successfully;
  • timestamp – checks for files created server side containing a timestamp and thus ensuring snapshots are succeeding;
  • rotation – checks that retention directories are being rotated; and
  • dir-creation – checks that retention directories are being created.

Please see this Github wiki page for more information including instructions.

Analysing MySQL Slow Query Logs

MySQL has a really useful feature that allows it to log slow queries where slow is a minimum time defined by you in micro seconds. It helps a lot is diagnosing website outages or slow responsiveness issues after the fact.

Unfortunately I couldn’t find any nice graphical tools for analysing these but there are a few command line tools:

mysqldumpslow

MySQL’s own tool, mysqldumpslow, which aggregates queries and allows you to sort them by: query time or average query time; lock time or average lock time; rows sent or average rows sent; or the number of queries.

Percona’s MySQL Slow Query Log Analyser

Dating from 2006, Percona’s Peter Zaitsev wrote about their own version of a slow query log analyser (local copy) which has given me good results. Note that their micro time patch has since been incorporated into MySQL mainstream.

One of the main differences over MySQL’s own version is that as well as printing the aggregated query (with number and string literals wildcarded), it also prints a real example of the query allowing a copy and paste to MySQL for execution with EXPLAIN.

Example output with query details redacted:

### 230 Queries 
### Total time: 4708.948293, Average time: 20.4736882304348
### Taking 0.093420 to 203.693466 seconds to complete
### Rows analyzed 0 - 141008
SET timestamp=XXX;
SELECT ... FROM ... AS A 
        INNER JOIN ... AS C ON C.item_id = A.item_id 
    WHERE XXX AND C.item_lang = 'XXX' AND ... 
    ORDER BY CATALOG.item_sort LIMIT XXX;

SET timestamp=1348032761;
SELECT ... FROM ... AS A 
        INNER JOIN ... AS C ON C.item_id = A.item_id 
    WHERE 1 AND C.item_lang = '1' AND ... 
    ORDER BY C.item_sort LIMIT 1;

 

So it’s finally happened…

RIPE put out a press release today:

RIPE NCC Begins to Allocate IPv4 Address Space From the Last /8

14 Sep 2012

On Friday 14 September, 2012, the RIPE NCC, the Regional Internet Registry (RIR) for Europe, the Middle East and parts of Central Asia, distributed the last blocks of IPv4 address space from the available pool.

This means that we are now distributing IPv4 address space to Local Internet Registries (LIRs) from the last /8 according tosection 5.6 of “IPv4 Address Allocation and Assignment Policies for the RIPE NCC Service Region“.

This section states that an LIR may receive one /22 allocation (1,024 IPv4 addresses), even if they can justify a larger allocation. This /22 allocation will only be made to LIRs if they have already received an IPv6 allocation from an upstream LIR or the RIPE NCC. No new IPv4 Provider Independent (PI) space will be assigned.

It is now imperative that all stakeholders deploy IPv6 on their networks to ensure the continuity of their online operations and the future growth of the Internet.

In other words, for all intents and purposes, Europe (and Central Asia and the Middle East) is out of IPv4 addresses. Funnily enough, I’m actually happy that this long predicted day has arrived and we can start the next phase of IPv6 deployment.

Anonymous Objects in PHP

A little known but often useful feature of PHP’s object oriented functionality is anonymous objects which are generally used as value stores. Here’s an example:

$valueStore = (object) array(
    'name' => 'John Smith',
    'address' => array(
        '1 Some Street',
        'Some Town, Post Code',
        'Ireland'
    )
);

If you were to dump the resultant object, you’d get:

object(stdClass)#1 (2) {
    ["name"] => string(10) "John Smith"
    ["address"] => array(3) {
        [0] => string(13) "1 Some Street"
        [1] => string(20) "Some Town, Post Code"
        [2] => string(7) "Ireland"
    }
}

You can now add new items ($valueStore->item = 'qwerty'), check is items are set (isset()), remove items (unset()), and retrieve items ($valueStore->item).

But why? Well, a reason I use these anonymous objects for frequently is when I need to pass around a value store between different functions, objects, registries and so forth. With standard arrays, these are passed by value meaning you are making copies but also that changes on one won’t affect another.

If we use anonymous objects then these are passed by reference and no copies are created. We could use the reference operator I hear you scream. Yes, we could. But that is more prone to forgetful errors and is not as elegant as the above!

If you want to take it further, you can add functionality via anonymous functions and closures.

Two Git Branching Models

In current projects, we tend to float between two branching models depending on the requirements of the customer / project and the planned deployment process.

git-flow

This was previously known as A successful Git branching model with an extremely detailed overview and instructions here. It has since spawned a project to help make using this model easier – git-flow.

This is a great branching model for a team of people who work towards creating planned versioned deployments (whether it be time based such as every second Tuesday, or milestone based).

In essence, this model uses two main branches:

  • origin/master – the main branch where the source code of HEAD always reflects aproduction-ready state.
  • origin/develop - where the source code of HEAD always reflects a state with the latest delivered development changes for the next release. Some would call this the “integration branch”. This is where any automatic nightly builds are built from.

Then developers create supporting branches as part of their development process:

  • feature branches – branched off origin/develop for active development of a new feature / enhancement;
  • hotfix branches – a branch off origin/master to apply a critical fix to production code;
  • release branches – short lived branches off origin/develop which are used for final testing and patched before being merged to origin/master.

The model works very well in practice and the above linked document is a excellent read on Git branching practices in general as well as git-flow in particular.

Github Flow

This is the model used at Github and discussed by Github developer Scott Chacon here.

This is suited for projects that deploy continuously rather than around the concept of releases and so it’s less constrained than git-flow. These are two very different models and Scott puts forth his arguments in favour of the Github model in his post linked above.

In essence, Github flow works as follows:

  • origin/master is always deployable. Always.
  • Similarly to git-flow, new features are done in their own branch – but off of origin/master in this case.
  • Now, when you believe your new feature is complete, a merge request is opened so someone else can review and check your work. This is the QA process.
  • Once someone else signs off, you merge back into origin/master.
  • This is now deployable and can and will be deployed at anytime.