warning: SASL authentication failure: cannot connect to saslauthd server: No such file or directory

There's nothing quite like being in a complete coding frenzy, communicating with your customers to get feedback on critical bugs, and your mail server going to SMTP heaven on you.

The Setup
My MTA (postfix) is set up to do secure SMTP-AUTH and TLS via Cyrus SASL library (a.k.a. saslauthd via the sasl2-bin package) on an Ubuntu box.

Postfix SASL support (RFC 4954, formerly RFC 2554) is used to authenticate remote SMTP clients to the MTA and the Postfix SMTP client to a remote SMTP server.

The Error
I originally set things up via the Postfix-SMTP-AUTH-TLS-Howto and everything was working fine until earlier today when I started seeing the following log entries when trying to send mail vi the MTA:

May 30 03:03:36 pyxidis postfix/smtpd[2840]: connect from unknown[x.x.x.x]
May 30 03:03:37 pyxidis postfix/smtpd[2840]: setting up TLS connection from unknown[x.x.x.x]
May 30 03:03:40 pyxidis postfix/smtpd[2840]: Anonymous TLS connection established from unknown[x.x.x.x]: TLSv1 with cipher AES128-SHA (128/128 bits)
May 30 03:03:40 pyxidis postfix/smtpd[2840]: warning: SASL authentication failure: cannot connect to saslauthd server: No such file or directory
May 30 03:03:40 pyxidis postfix/smtpd[2840]: warning: SASL authentication failure: Password verification failed
May 30 03:03:40 pyxidis postfix/smtpd[2840]: warning: unknown[x.x.x.x]: SASL PLAIN authentication failed: generic failure
May 30 03:03:46 pyxidis postfix/smtpd[2840]: lost connection after AUTH from unknown[x.x.x.x]
May 30 03:03:46 pyxidis postfix/smtpd[2840]: disconnect from unknown[x.x.x.x]

The Solution
I checked and the saslauthd process was happily running. Next up I had a peek in /var/spool/postfix/var/run/saslauthd/ (which I had previously created as per the HOWTO above) but there were no *mux* files to be seen as there should have been.

I then dawned on me that postfix runs in a chrooted jail and that saslauthd for some reason had stopped writing the required info to the chrooted jail where postfix was running. A quick look at the saslauthd rc script and its default file showed that it no longer had the required config to do this properly.

Why? Dunno. I'll have to go do some snooping a little later.

For now thought the fix was as simple as modifying the OPTIONS variable in the /etc/defaults/saslauthd config file to be something like this:

OPTIONS="-c -m /var/spool/postfix/var/run/saslauthd"

Restart saslauthd and things start appearing where they should and mail is back in business.

Cacti Segfaults

I recently did a cacti installation for a customer and ended up skipping step #3 from the Install and Configure Cacti guide.

Step in question:

shell> mysql cacti 

Why would I have skipped this very crucial step you might say?

Well, the installation was done in two sessions with enough time having elapsed between the initial and final sessions that I had gotten hazy on what was and wasn't done. I had created the database but just never took the next step.

After completing the rest of the configuration I fired Cacti but via my browser and php promptly did a segfault and lay there on the ground haemorrhaging. From my recent experience php has a propensity to do this in two specific cases:

• Something went awry with a database connection or using a database resource
• You're pushing the php boundaries with recursive regexps in a pre_match*() function

Once I sat down and went through each of the steps required to set the beastie up I realized I simply needed to import the db schema and initial data to get things going.

Presto!

Tales from the (PHP and Perl) Crypt - AES Encryption in MySQL

I was looking for a way to share encrypted information between two systems where a table in MySQL was the integration point.

The one system is based on php while the other component is a perl daemon.

Let's get cryptic

My first stab at this was a perl based solution using the Crypt::CBC and Crypt::Blowfish libraries plus a shared secret/key. This meant I had to develop a perl script which I called from php to do the encryption which is a rather inelegant solution.

At first I could not find the right libs in php to get this done but later stumbled upon the Mcrypt suit off php and MCrypt perl functions that allow you to do encryption between the two different subsystems.

Unfortunately this means you have double the amount of hassle when it comes to updates and ensuring things Just Work™.

Move it back to the source
Some more checking brought me to the MySQL AES encryption functions that are built into MySQL. They provide the best cryptographic algorithms MySQL currently has to offer and are pretty respectable from a academic encryption perspective.

This means en/decryption is dealt with at one integration point across all languages involved which is much more elegant.

Tales from the Crypt
The MySQL AES encryption functions allow you to en/decrypt data quite easily. To encrypt a string you simply issue the following, assuming your shared secret is lesser-spotted-mountain-squid:

mysql> INSERT INTO test_table (test_column) VALUES(AES_ENCRYPT('this is a super-secret message', 'lesser-spotted-mountain-squid'));
Query OK, 1 row affected (0.09 sec)

mysql> SELECT * FROM test_table;
+----------------------------------+
| test_column                      |
+----------------------------------+
| Aÿ„1
ý#ôärO™é=:Žï   ¼Ñ†kWA |
+----------------------------------+
1 row in set (0.00 sec)

Et voila!

One thing you need to keep in mind is that the field you want to store your encrypted data in must be a MySQL BLOB data type.

Sucking our super secret string back out into a usable form is as simple as:

mysql> SELECT AES_DECRYPT(test_column, 'lesser-spotted-mountain-squid') AS top_secret FROM test_table;
+--------------------------------+
| top_secret                     |
+--------------------------------+
| this is a super-secret message |
+--------------------------------+
1 row in set (0.00 sec)

The security lesson
This is rather obvious but your security is only as strong as the weakest link in the chain. In this specific case I did not want to have clear text data in the db and achieved that amicably.

Because my secret is in clear text in two different systems I am rather exposed if those systems are not as secure as they could be. Lucky for my they are pretty much locked away from daylight so I'm not too concerned.

Ubuntu 8.04 and PAM SMB Password

For those of you who have taken the plunge to Ubuntu v8.04 (Hardy Heron) you may have noticed that your auth.log is being filled with the following:

May  4 03:17:01 example CRON[10796]: PAM adding faulty module: /lib/security/pam_smbpass.so
May  4 04:17:01 example CRON[10799]: PAM unable to dlopen(/lib/security/pam_smbpass.so)
May  4 04:17:01 example CRON[10799]: PAM [error: /lib/security/pam_smbpass.so: cannot open shared object file: No such file or directory]

What's up?
For some reason the Ubuntu gods have decided by default to include PAM configuration for the PAM SMB password module without actually installing the PAM SMB password module.

Hence the complaints in your logs.

Make it go away!
Sure, simply install the libpam-smbpass package or edit two config files on your system like this:

$ perl -p -i -e 's/(password\s+optional\s+pam_smbpass.so nullok use_authtok use_first_pass)/#$1/' /etc/pam.d/common-password
$ perl -p -i -e 's/(auth\s+optional\s+pam_smbpass.so migrate)/#$1/' /etc/pam.d/common-auth

You can find some more info on this boog here.

Baking CakePHP with nginx

I've switched all my web server related infrastructure to nginx which is a high performance HTTP server (amongst other things) which blows apache out of the water (IMNSHO).

If you're a CakePHP user you'll know that it has some special rewriting requirements which can be found in $ROOT/.htaccess:

$ cat .htaccess

RewriteEngine on
RewriteRule    ^$ app/webroot/    [L]
RewriteRule    (.*) app/webroot/$1 [L]

Unfortunately this .htaccess file is an apache mechanism to achieve the URL rewriting that is required to get CakePHP to play nice. The apache rewrite rules do not translate directly to something nginx can use though so some work is required to get things going.

Being lazy (and believing that no problem I discover is unique to me) I had a look a round and found this article by Chris Hartjes which needed a some mods for it to work for my setup:

# CakePHP rewrite rules
location / {
  root /opt/local/html/live_site;
  index index.php;

  # Serve static page immediately
    if (-f $request_filename) {
    break;
  }

  if (!-f $request_filename) {
    rewrite ^/(.+)$ /index.php?url=$1 last;
    break;
  }
}

Here's my complete nginx.conf to give you an idea of how everything fits together:

user  nobody;
worker_processes  1;

#error_log  logs/error.log;
#error_log  logs/error.log  notice;
#error_log  logs/error.log  info;

#pid        logs/nginx.pid;


events {
  worker_connections  1024;
}

http {
  include       etc/nginx/mime.types;
  default_type  application/octet-stream;
  server_names_hash_bucket_size  128;

  sendfile           on;
  keepalive_timeout  20;
  tcp_nodelay        on;

  server {
    listen       80;
    server_name  localhost;
    rewrite_log on;

    #error_page  404              /404.html;
    # redirect server error pages to the static page /50x.html
    #
    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
    root   share/nginx/html;
    }

    # Serve static content directly with some caching goodness
    location ~* ^.+.(jpg|jpeg|gif|css|png|js|ico)$ {
      root /opt/local/html/live_site/app/webroot;
      access_log        off;
      expires           1d;
    }

    # CakePHP rewrite rules
    location / {
      root /opt/local/html/live_site;
      index index.php;

      # Serve static pages immediately
      if (-f $request_filename) {
        break;
      }
      
      # Rewrite all other URLs
      if (!-f $request_filename) {
        rewrite ^/(.+)$ /index.php?url=$1 last;
        break;
      }
    }

    # Pass PHP scripts to FastCGI server listening on 127.0.0.1:9000
    #
    location ~ \.php$ {
    root /opt/local/html/live_site;
    fastcgi_pass   127.0.0.1:9000;
    fastcgi_index  index.php;
    include        /opt/local/etc/nginx/fastcgi_params;
    }
  }
}

PHP5 SimpleXML and CDATA

I am in the process of porting a rather large PHP4 application to PHP5 (just in time for PHP6, yes, yes, I know) for one of my customers. Most of the application is pure imperative programming so the switch has been rather painless.

Unfortunately (for me) they have made rather judicious use of the PHP4 domxml extension libraries which no longer exist in PHP5 (where they have been replaced with the dom extension).

Moving from domxml to dom was straight forward (looping over tags, tags, attributes and text inside tags are addresses differently) so I chose to simply re-write the code to use the new dom extensions instead of opting for a translation library like the one provided by Alexandre Alapetite.

One exception to this was the use of < !--[CDATA[...]]--> blocks which SimpleXML simply seemed to discard when creating a new object.

A quick look around Google (here, here and here) and I found what needed to be done to address SimpleXML's ignorant behaviour.

The SimpleXML constructor allows you to pass in extra libxml2 parameters which allow you to get further functionality out of the library. The one I was interested was of course:

LIBXML_NOCDATA  (integer)
Merge CDATA as text nodes

So, simply changing my constructor from:

$xml = new SimpleXMLElement($text)

to:

$xml = new SimpleXMLElement($text, LIBXML_NOCDATA)

was all that was required for me to gain access to those < !--[CDATA[...]]--> structures.

Aspell, PSPELL, PHP and OS X

Until quite recently there was no way to use Aspell (via the PSPELL PHP libs) on an OS X host that was using the MacPorts system for package management.

This was simply because of the lack of a pspell variant for the php{45} packages.

Port of call
The ports system has the notion of a variant for packages that are conditional modifications of port installation behaviour.

There are two types of variants: user-selected variants and platform variants.

User-selected variants are options selected by a user when a port is installed while platform variants are selected automatically by MacPorts' base according to the OS or hardware platform (Darwin, FreeBSD, Linux, i386, PPC, etc.).

More stuff and less fluff
There are several ways of working this. The first would be to log a ticket at the MacPorts trac with a request to add the variant.

Depending on the package maintainer's load you may be a response pretty quickly. I've generally gotten something back within days of logging the ticket.

In the meantime your universe cannot come to a halt waiting for someone else to add the next greatest thing as a variant to your favourite package. So here's some manual steps to get things up and running in the meantime:

• Install Aspell
  
• Recompile and install PHP with the required PSPELL support
  
• Check php to ensure the new PSPELL libs are active
  
• Do a simple test to see if everything is working as it should
  

Install Aspell
I'll assume you're using MacPorts for your your package management on your OS X host.

Grab the aspell application, libs and whichever dictionaries catch your fancy:

$ sudo port install aspell aspell-dict-en


Be sure to install at least one dictionary or your spell checking days will be rather deflated.

Recompile and install PHP with the required PSPELL support
To manually add a compilation flag you need to edit the Portfile that comes with your installed PHP version. Mine is located at:

/opt/local/var/macports/sources/rsync.macports.org/release/ports/www/php5/Portfile

Edit the Portfile and add “–with-pspell=${prefix}” to configure.args. You can then re-ininstall PHP and it should now use the modified Portfile to compile PHP.

Check php to ensure the new PSPELL libs are active
Use the following script from the command line to determine if your PHP was re-installed with the required PSPELL bits enabled:

$ php -r 'phpinfo();' | grep PSpell
PSpell Support => enabled

Do a simple test to see if everything is working as it should
You should be able to just use the example from the PHP documentation page to ensure everything is fine:

$ cat /tmp/t_pspell.php

$ php -f /tmp/t_pspell.php
Sorry, wrong spelling

The packaging gods exist!
A few days after creating this ticket on the MacPorts trac I got a response from the package maintainer informing me that the variant had been added to all the relevant PHP packages.

Cool!

If your ports distribution files are up-to-date you should now be able to do the following to see which variants are available for your PHP version of choice:

$ port info php5
php5 5.2.5, Revision 2, www/php5 (Variants: universal, darwin_6, darwin_7, macosx, apache, apache2, fastcgi, gmp, imap, pspell, tidy, mssql, snmp, macports_snmp, mysql3, mysql4, mysql5, oracle, postgresql, sqlite, ipc, pcntl, pear, readline, sockets)
http://www.php.net/

PHP is a widely-used general-purpose scripting language that is especially suited for developing web sites, but can also be used for command-line scripting.

Library Dependencies: libxml2, libxslt, openssl, zlib, bzip2, libiconv, expat, gettext, tiff, mhash, libmcrypt, curl, pcre, jpeg, libpng, freetype
Platforms: darwin freebsd
Maintainers: ryandesign@macports.org jwa@macports.org

Now that pspell is listed as a variant you can install PHP with this variant by doing the following, after removing previous PHP version:

$ sudo port install php5 +pspell


Pre-queue content-filter connection overload

In the last while I've been seeing the following error pop up in my logwatch report for postfix:


*Warning: Pre-queue content-filter connection overload


At first I was concerned that the pre-queue content-filtering subsystem of postfix was somehow being overwhelmed and I was possibly loosing mail. Digging around a bit more lead to these types of log entries that seemed like they were the subject of the logwatch report:


Feb 21 13:01:45 pyxidis postfix/smtpd[5994]: connect from unknown[unknown]
Feb 21 13:01:45 pyxidis postfix/smtpd[5994]: lost connection after CONNECT from unknown[unknown]
Feb 21 13:01:45 pyxidis postfix/smtpd[5994]: disconnect from unknown[unknown]


Huh?!
From what I can glean here the log entries above indicate that a SMTP connection was established with the kernel but the connecting host hot potatoed it before postfix was able to process the connection.

When postfix tries to process the connection there's nobody home because the kernel had already removed the connection and it dumps something like the lines above to the mail log.

Wherefor?
Here's the scoop from the logwatch docs:


This sometimes occurs in reaction to a portscan or broken bots, or when postfix is overloaded, due to excessive header_checks / body_checks content filtering, or even too few smtpd processes to service the demand. One could reduce the number of header_checks and body_checks, and possibly set smtpd_timeout to 60 (seconds). The key is that existing clients are overloading the number of smtpd daemons. The postfix-logwatch section configuration variable is postfix_ConnectionLostOverload, and the command line option is --connectionlostoverload. If you consider this sub-section to be meaningless, set the level limiter value to 0 and the sub-section will be suppressed.


I was not going to change my header or body checks (because they keep the unwashed spammers at bay) so I opted for tuning my smtpd_timeout down to 30 seconds in main.cf.

Because this looks like it is a possible resource issue you could also up the amount of smtpd processes allowed to service the pre-queue content-filtering subsystem.