Recently Jason A. Donenfeld reported a simple vulnerability in W3 Total Cache on the Full Disclosure mailing list, which was picked up by the Security Ledger website, and then posted on Slashdot. The vulnerability is a simple Apache Httpd configuration oversight — plugins often create their own folders under ./wordpress/wp-content/ without considering that directory indexing might be turned on, or that files within that folder are located under a DocumentRoot, and thus available to anyone. Some configuration files are also vulnerable in this way — the wp-config.php file, for example. During the WordPress install, it is recommended that the wp-config.php be re-located one folder above ./wordpress/, to move it out of the DocumentRoot.
Enable Autocomplete for root on Mac OS
Are you frustrated by the lack of autocomplete in root’s shell on Mac OS? I’ve tried a few different solutions, and the easiest / simplest I found is to create an /etc/inputrc file (chown root:wheel and chmod 644) with the following text.
"\C-i": completeThe /etc/inputrc file is used by readline — the input-related library used by bash and most other shells. GNU’s readline init file syntax page documents all the available settings.
Autossh Startup Script for Multiple Tunnels
When an encrypted VPN is not available, the next best solution is usually port-forwarding one or more port(s) through an SSH tunnel. The down-side of SSH is that by itself it cannot maintain a persistent connection — network issues may force the tunnel to stop responding, or even drop completely. Autossh is a small front-end for SSH that can monitor the connection, and restart the tunnel if it drops or stops responding. I found that the startup scripts available for autossh on the internet were a little too basic for my needs — I wanted autossh to start multiple connections, and to start/stop each one individually if I needed — so I wrote my own.
WordPress OS Disk Cache Report, Prime and Flush
I wrote a bash script this morning to report the size of WordPress cache folders, the number of files they contain, read each file to prime the OS disk cache, and optionally flush the OS disk cache as well. This might be a script you could execute to email a daily/weekly report of cache folder sizes, or perhaps execute during/after booting a server to prime the OS disk cache, or even on a regular schedule to make sure the OS cache is always primed. The script also has a “flush” argument to sync and drop the OS disk cache, which isn’t very useful (to me) except to see the difference in speed between a clean and primed cache (about 11s vs 0.4s for all websites on my server).
Memcached vs Disk Cache
I recently added some disk caching for MySQL queries, WordPress objects, PHP opcode, and PHP web pages on my server. There are several different caching techniques and applications available, and memcached seems like one of the more popular ones. Right or wrong, it appears to be the default go-to for many developers these days.
Since I’m a SysAdmin by profession (with maybe a penchant for scripting and integration), I tend to have a more “systems” oriented approach — which led me to first consider, and then choose disk caching over memcached. In this post, I’ll outline the reasons I chose disk caching, and why in most circumstances it might be superior to memcached.
Quick Freeze / Thaw of Reverse Zones
I had to update several reverse zone files today, so wrote a quick for-loop in bash to freeze and thaw all the zones. The script parsed the zone file names and reversed them into a proper `d.c.b.a.in-addr.arpa` format. Later I tweaked it with sed to make it more flexible (in order to pass it a full or partial IP address), but ended up using `tac` for the reversing part instead – that’s what it’s made for after all. And if you’re wondering what `tac` stand for, just read `cat` backwards. :-)
Create and Update OTRS Tickets from the Command-Line
I recently wrote a notification script for Centreon / Nagios to create and update tickets in OTRS. The ticket details and OTRS connection settings are all defined on the command-line. The GenericTicketConnector.yml must first be installed in OTRS, and a user (aka “Agent”) created for the script. I used perl’s taint mode, so had to hard-code the various log file locations ($logfile, $csvfile, and $dbfile). The Log::Handler module allows the script to output and log different amounts of activity detail, and the DBD::SQLite module is used to keep a local database of the Ticket ID (from OTRS) and the Problem ID (from Centreon / Nagios) associations — so the OTRS ticket can be updated with follow-up notifications from Centreon / Nagios for the same issue.
Change Passwords with SSH and Expect
A few years ago I was supporting a very diverse environment with Solaris, AIX, and Linux servers; some with password logins, public/private key authentication, and several with SecurID passwords. All accounts were local, passwords expired every three months, and the accounts locked after three failed logins — so you can imagine the mess this created if you didn’t go around every server at least every three months. After I’d accumulated about half a dozen passwords, I wrote an Expect script to login and change my password and wrapped it with a bash script to try every old password I had. Since some servers needed a SecurID number to login, the bash script would pause on those and prompt me for the token before continuing.